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On the control of heating systems in the UK

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Abstract

This paper reviews current heating system control practice in the UK through surveys, computer simulation and experimental studies. It is evident from the survey results that both boiler and heat emitter controls in the UK are generally poor. Computer simulation of a heating system demonstrated that the use of poorly commissioned boiler controls and the use of thermostatic valves with limited flow control leads to buildings not maintaining the desired internal temperatures. This results in occupant discomfort when under-heating occurs and excess fuel consumption when over-heating occurs. Finally, an experimental study demonstrated that a newly developed boiler control algorithm can offer significant energy savings by controlling the boiler more appropriately and reducing the effect of poor thermostatic radiator valve use.

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... A heating system using condensing boilers is still designed to operate at 80/60 • C or 70/60 • C during peak demand [51,95], hence this has a limited impact on the sizing of the heating system. In non-domestic buildings, condensing boilers are not mandatory [27], and despite having an efficiency of some 10% higher than non-condensing boilers [51], a low price of energy limits the financial benefit of the investment [101]. Therefore, condensing boilers are widely deployed in domestic buildings but less-so in non-domestic buildings. ...
... For non-domestic systems, the setting of the weather-compensated control curve (where fitted) is another cause of malfunction. In a survey undertaken in 2004, it was found that the compensation curves were all set inappropriately [101]. Another cause of malfunction results from the hydraulic balancing of the heating system. ...
... The radiator is the main type of heat emitter in the UK, with up to 80% in nondomestic buildings [101]. Other typical heat emitters are underfloor and AHU. ...
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To reach net-zero emissions by 2050, buildings in the UK need to replace natural gas boilers with heat pumps and district heating. These technologies are efficient at reduced flow/return temperatures, typically 55/25 °C, while traditional heating systems are designed for 82/71 °C, and an oversized heating system can help this temperature transition. This paper reviews how heating systems have been sized over time in the UK and the degree of oversizing in existing buildings. It also reviews if lessons from other countries can be applied to the UK’s building stock. The results show that methods to size a heating system have not changed over time, but the modern level of comfort, the retrofit history of buildings and the use of margin lead to the heating system being generally oversized. It is not possible to identify a specific trend by age, use or archetype. Buildings in Scandinavia have a nascent readiness for low-temperature heat as they can use it for most of the year without retrofit. Limitations come primarily from the faults and malfunctions of such systems. In the UK, it is estimated that 10% of domestic buildings would be ready for a supply temperature of 55 °C during extreme external conditions and more buildings at part-load operation. Lessons from Scandinavia should be considered with caution. The building stock in the UK generally underperforms compared to other EU buildings, with heating systems in the UK operating at higher temperatures and with night set-back; the importance of providing a low-return temperature does not exist in the UK despite being beneficial for condensing boiler operation. Sweden and Denmark started to develop district heating technologies with limitations to supply temperatures some 40 years ago whereas the UK is only just starting to consider similar measures in 2021. Recommendations for policy makers in this context have been drawn from this review in the conclusions.
... Finalement, les économies d'énergie annoncées par les différents fabricants sont fortement dépendantes de la situation de référence et ne semblent réalistes que si l'on se base sur une situation reflétant une absence totale de régulation associée à un comportement peu vertueux. Cela peut malheureusement s'entendre lorsque l'on connait la réalité du terrain [11,13]. Par ailleurs, il semble que les économies réalisables sont principalement basées sur le caractère autonome de la régulation, permettant d'écarter l'utilisateur du processus. ...
... Pour cette raison, le NMBE ne peut être considéré seul, un autre indicateur doit être introduit. 11 International Protocol of Measurement and Verification Performance 12 American Society of Heating, Refrigerating and Air-Conditioning Engineers 13 Federal Energy Management Program, Measurement &Verification for performance-based contracts ...
... Cela peut en revanche devenir problématique dans le cas de systèmes fortement capacitifs (plancher chauffant dans un bâtiment inertiel par exemple) où la période d'inconfort, pouvant atteindre plusieurs heures, devient non négligeable et donc plus difficilement acceptable pour les occupants. En plus de leurs limitations intrinsèques, des études ont montré que ces systèmes de régulation pourtant simples, mais demandant une gestion par l'occupant, tels que les vannes thermostatiques et les thermostats d'ambiance, massivement utilisées dans le secteur résidentiel, sont généralement très mal gérés car mal compris [11,13,151]. ...
Thesis
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Le développement des techniques d’apprentissage automatique, et plus particulièrement des réseaux de neurones, associé à celui des nouvelles technologies de l’information et de la communication, bouleverse nos sociétés à travers des avancées technologiques dans une variété de secteurs d’activité. Le secteur du bâtiment n’est pas épargné, si bien que ces techniques peuvent constituer une opportunité intéressante dans un contexte où les émissions de gaz à effet de serre doivent être drastiquement réduites. L’objectif de ces travaux est d’évaluer l’intérêt de ces techniques appliquées à l’énergétique du bâtiment, dans une optique de réduction des consommations énergétiques et d’amélioration du confort thermique. Nous veillons par ailleurs à garder lors de cette évaluation une vision globale, en plaçant les éventuels avantages en face des différents besoins relatifs au développement de ces technologies. Ce travail de thèse s’organise en trois parties précédées d’une introduction détaillée visant à donner au lecteur une vue d’ensemble des différents éléments de contexte, permettant ainsi la mise en perspective du travail de thèse. Nous donnons ensuite dans la première partie le cadre théorique nécessaire à la compréhension des problématiques rencontrées lors de l’élaboration et de la création des réseaux de neurones pour des applications à l’énergétique du bâtiment. Dans un second temps, une étude bibliographique donnant au lecteur un large aperçu des diverses applications des réseaux de neurones au domaine de l’énergétique du bâtiment est présentée. La seconde partie est consacrée à la calibration du modèle de bâtiment utilisé ensuite pour tester et évaluer un contrôleur prédictif mettant en œuvre des réseaux de neurones. Après une explication de la méthode utilisée puis une présentation détaillée du modèle, une analyse complète des résultats de calibration est menée. Nous terminons cette partie par des observations et recommandations concernant les méthodes classiques de calibration préconisées par différents organismes internationaux. Enfin, une application concrète mettant en œuvre des réseaux de neurones pour le contrôle prédictif de la température intérieure est présentée au cours de la troisième partie. Après un point théorique concernant le contrôle prédictif, nous détaillons la méthode développée pour l’entraînement des réseaux de neurones utilisés. Les résultats obtenus en simulation avec un contrôleur prédictif sont ensuite analysés et comparés à ceux obtenus en présence de deux contrôleurs de référence pour diverses hypothèses de simulation. Le contrôleur prédictif est ainsi testé dans plusieurs cas de figures, allant d’une situation idéale à des conditions de fonctionnement plus réalistes, en passant par deux types d’émetteurs de chaleur différents, à savoir des plafonds rayonnants et un plancher chauffant.
... Several studies have therefore investigated how heating systems can be made to operate properly. The main aim of these studies was to investigate various ways of achieving energy savings and ensuring the proper thermal comfort of occupants through improved heating system control [51,55,62,63,[74][75][76][77][78]. The results highlight the following measures, which have been shown to have a great impact on the efficiency of the heating system control [32,63]: ...
... It may therefore require a higher level of expertise to ensure the proper functionality of a heating system balanced for a low flow rate. The complexity of the task is further increased by the interaction between the different heating system components [83] and the fact that thermostatic radiator valves do not always provide perfect control [39,84,85] and are often not operated properly [55,74,86,87]. ...
... Furthermore, there are good reasons to check the operation of a heating system regularly, because heating system settings get modified over time [51], and faults constantly arise in the control of a heating system [7]. Since occupants are not likely to react to poor heating system control unless their comfort is jeopardized, there is a need for tools to identify faults so that technicians can ensure that heating systems work properly [55,74]. ...
Thesis
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This thesis presents the results of four years of research on the possibility of providing existing buildings with space heating based on low-temperature district heating. The study consisted of three main parts. First, we investigated the sizes of current heating elements in existing buildings and the potential for using these heating elements for low-temperature heating. Secondly, we investigated several case study buildings in order to evaluate whether the control and operation of their heating systems constituted a barrier to realizing the full potential of the radiators installed. Thirdly, we investigated the possibility of applying various tools to realize the potential available for low-temperature district heating. The results showed that there is a big potential for using lower temperatures for space heating because as much as 80% of heating systems are currently over-dimensioned. Temperatures can often be reduced for much of the year even in under-dimensioned heating systems because heating systems are designed for very low outdoor temperatures that only rarely occur in reality. We found several examples of existing single-family houses that have been successfully heated with low-temperature district heating. However, in some of the houses investigated, the results indicated that poor control and heating system design caused heating system return temperatures to be unnecessarily high. Poor hydraulic control was a major issue and this was caused by simple problems like hydraulic short-circuits, thermostats not working optimally, occupants using the thermostats in the wrong way, and a few radiators being too small. It should be possible to overcome such problems by improving the hydraulic control in heating systems and in some cases by replacing a few critical radiators that have a large impact on the overall heating system return temperature. To ensure long-lasting results, it is vital that continuous fault detection can be carried out. Current research indicates that this can be based on monitoring data from energy meters or heat cost allocator devices. Monitoring of data needs to be combined with a physical inspection of the heating systems to identify crucial design errors, such as hydraulic short-circuits. One drawback of the methods currently used to correct heating system malfunctions is the fact that they are often based on simplifications that do not fit well with the actual conditions in the buildings. It is therefore suggested that these methods should be improved and new efficient tools to ensure proper hydraulic control should be developed, such as a new radiator thermostat with a return temperature sensor or a pump control system that would minimize excess water flows. Finally, in order to ensure that the improvements are carried out, customers must have an incentive to invest in a well- functioning heating system, and there is a need for personnel who can offer the correct service agreements and drive the transition. The overall conclusion of the study is that there is a large potential for using low-temperature district heating for space heating in existing buildings, and the current results indicate that it is economically feasible to realize this potential between now and 2050. To support the realization of this potential, future work should focus on improving the technical solutions and practical methods for implementing proper heating system control in existing buildings.
... If the water temperature is higher than Cut-Out, the boiler is switched off. If the water temperature is lower than the Cut-In, the boiler is switched on (Liao, Swainson & Dexter, 2005). The water set-point temperature can be fixed, varied based on external air temperature or varied based on heating load. ...
... The water set-point temperature can be fixed, varied based on external air temperature or varied based on heating load. Liao et al. (2005) discussed that the overall performance of a heating system is considerably affected by the scheme for determining the value of water temperature set-point. ...
... Improving the efficiency of domestic heating systems can be studied by considering the individual components such as boilers, thermostats, heat emitter controls (TRVs), pumps etc. or by considering the heating system as a whole (Liao, Swainson & Dexter, 2005). Liao et al. (2005) argues that although each individual item is becoming more efficient, the improvement in efficiency of the heating system as a whole is still unknown to a large extent. ...
Thesis
Full-text available
Most existing houses in the UK have a single thermostat, a timer and conventional thermostatic radiator valves to control the low pressure, hot water space heating system. A number of companies are now offering a solution for room-by-room temperature and time control in such older houses. These systems comprise of motorised radiator valves with inbuilt thermostats and time control. There is currently no evidence of any rigorous scientific study to support the energy saving claims of these ‘zonal control’ systems. This thesis quantifies the potential savings of zonal control for a typical UK home. There were three components to the research. Firstly, full-scale experiments were undertaken in a matched pair of instrumented, three bedroom, un-furbished, 1930s, test houses that included equipment to replicate the impacts of an occupant family. Secondly, a dynamic thermal model of the same houses, with the same occupancy pattern, that was calibrated against the measured results. Thirdly, the experimental and model results were assessed to explore how the energy savings might vary in different UK climates or in houses with different levels of insulation. The results of the experiments indicated that over an 8-week winter period, the house with zonal control used 12% less gas for space heating compared with a conventionally controlled system. This was despite the zonal control system resulting in a 2 percentage point lower boiler efficiency. A calibrated dynamic thermal model was able to predict the energy use, indoor air temperatures and energy savings to a reasonable level of accuracy. Wider scale evaluation showed that the annual gas savings for similar houses in different regions of the UK would be between 10 and 14% but the energy savings in better insulated homes would be lower.
... If the water temperature is higher than Cut-Out, the boiler is switched off. If the water temperature is lower than the Cut-In, the boiler is switched on (Liao, Swainson & Dexter, 2005). The water set-point temperature can be fixed, varied based on external air temperature or varied based on heating load. ...
... The water set-point temperature can be fixed, varied based on external air temperature or varied based on heating load. Liao et al. (2005) discussed that the overall performance of a heating system is considerably affected by the scheme for determining the value of water temperature set-point. ...
... Improving the efficiency of domestic heating systems can be studied by considering the individual components such as boilers, thermostats, heat emitter controls (TRVs), pumps etc. or by considering the heating system as a whole (Liao, Swainson & Dexter, 2005). Liao et al. (2005) argues that although each individual item is becoming more efficient, the improvement in efficiency of the heating system as a whole is still unknown to a large extent. ...
Thesis
Full-text available
Most existing houses in the UK have a single thermostat, a timer and conventional thermostatic radiator valves to control the low pressure, hot water space heating system. A number of companies are now offering a solution for room-by-room temperature and time control in such older houses. These systems comprise of motorised radiator valves with inbuilt thermostats and time control. There is currently no evidence of any rigorous scientific study to support the energy saving claims of these zonal control systems. This thesis quantifies the potential savings of zonal control for a typical UK home. There were three components to the research. Firstly, full-scale experiments were undertaken in a matched pair of instrumented, three bedroom, un-furbished, 1930s, test houses that included equipment to replicate the impacts of an occupant family. Secondly, a dynamic thermal model of the same houses, with the same occupancy pattern, that was calibrated against the measured results. Thirdly, the experimental and model results were assessed to explore how the energy savings might vary in different UK climates or in houses with different levels of insulation. The results of the experiments indicated that over an 8-week winter period, the house with zonal control used 12% less gas for space heating compared with a conventionally controlled system. This was despite the zonal control system resulting in a 2 percentage point lower boiler efficiency. A calibrated dynamic thermal model was able to predict the energy use, indoor air temperatures and energy savings to a reasonable level of accuracy. Wider scale evaluation showed that the annual gas savings for similar houses in different regions of the UK would be between 10 and 14% but the energy savings in better insulated homes would be lower.
... Domestic space heating has been dominated by fossil fuels, efficiency improvement in space heating will thus reduce greenhouse gas emissions [4,7,[11][12][13]. Heating system efficiency depends upon the thermal performance of the building envelope, occupancy [14] and climate, as well as the performance the system's component parts [15][16][17][18][19][20]. Whilst, in most heating systems well-functioning energy efficient components are installed these components may not be (i) optimally adjusted to the particular variations in energy load encountered and (ii) set-up to optimally communicate effectively with one another [9,15,18,[20][21][22]. ...
... Heating system efficiency depends upon the thermal performance of the building envelope, occupancy [14] and climate, as well as the performance the system's component parts [15][16][17][18][19][20]. Whilst, in most heating systems well-functioning energy efficient components are installed these components may not be (i) optimally adjusted to the particular variations in energy load encountered and (ii) set-up to optimally communicate effectively with one another [9,15,18,[20][21][22]. Seemingly innocuous inaccurate settings of individual components can lead to significant over-consumption of energy [9,20]. ...
... The majority of heating systems combust a fossil fuel to generate heat and use electrical energy to pump heat via a hydraulic distribution system to radiators [15,17,23]. Energy efficiency gains from heat distribution systems are not always optimal with even the most progressive energy standards failing to regulate to ensure the energy saving potential of the system is fulfilled [4,6,9,12,15,[24][25][26]. A tendency to oversize heating plant leads up to 50% higher energy consumption, particularly at part load operation [15,16,18,27,28]. A study of 92 dwellings in Northern Germany between 2002 and 2005 found that, on average and as illustrated in Fig. 4, boilers were oversized to the peak heat load by a ratio of 1.8, pump design was typically 3 times bigger than was required, Fig. 4. Typical component oversizing [20]. ...
... The age and quality of TRVs are essential for their performance and ability to respond to changing conditions. Old TRVs tend to have longer time constants and limited rangeability [4] . Poorly managed commissioning of outdoor temperature compensators, affecting the control curve in the feedforward loop, has also led to lower thermal comfort and higher energy use [4,5] . ...
... Old TRVs tend to have longer time constants and limited rangeability [4] . Poorly managed commissioning of outdoor temperature compensators, affecting the control curve in the feedforward loop, has also led to lower thermal comfort and higher energy use [4,5] . ...
Article
Indoor temperatures in apartment blocks are often indirectly controlled by the outdoor temperature using a feedforward control loop, in which the radiator supply temperature is a function of the outdoor temperature. However, this control principle cannot take into account heat gains or losses caused by tenants, electrical appliances, the sun, air leakage, etc., which may result in uneven indoor temperatures, overheating, airing and increased energy use. This can be partly addressed by using thermostatic valves on each radiator. A municipal housing company in Sweden that uses individual metering and billing (IBM) of space heating costs based on measurements of indoor temperatures in all rooms of each apartment has been studied. This article presents and evaluates a project in which these measurements were used for feedback control. The aim of the study was to evaluate the principle which is based on using the actual indoor temperatures. An existing feedforward control of the heating system with thermostatic valves was enhanced by a correction of the supply temperature. The magnitude of the correction was proportional to the difference between the actual mean indoor temperature of the apartments and the set-point temperature. The enhanced control resulted in more constant indoor temperatures, i.e. they were less dependent on the outdoor temperature. The results support the conclusion that the evaluated method would be promising to apply in multi-family buildings. The introduction of the enhanced control method provided valuable experience and awareness of influencing factors if it were to be implemented on a larger scale.
... A heating system is a mechanism for maintaining temperatures at an acceptable level; by using thermal energy within a home, office, or other dwelling. While considering about efficient energy rating, some factors are taken into consideration, such as thermal irregularities in building envelope, energy efficiency of the boilers, the distribution system and the performance of the control system [12]. The floor heating system has constituted the rate of 50% of the heating system in the recent days at Europe. ...
... Heat emitters which are commonly used are radiators, under-floor heating, fan-coil units (FCU) and airhandling units (AHU). This survey also showed that 95% of radiators were controlled by using TRVs (thermostatic radiator valves) and revealed that more than 65% of TRVs were performing very poorly [12]. ...
Article
Full-text available
Selection of the heating system is based on many characteristics from the customer side. Operating cost, comfort, ease of use and aesthetic of the systems are some of the most important ones of these characteristics. In this article, data is collected primarily for the implementation of quality house. With these data, customer requirements are listed and defined in terms of degree of importance from the customer side. Then, the relationship between customer requirements and technical requirements are described. Also, column weights are calculated according to the defined relations. Finally, the results obtained using a quality house is integrated with Analytic Hierarchy Process (AHP) methodology for system selection. Then results are interpreted. The main contribution of this paper is to determine the best heating system selection using the relationship between customer and technical requirements. To the authors’ knowledge, this will be the first study which uses the integrated QFD-AHP method for heating system selection.
... When SE was not abundant, BB and ETH were used as auxiliary energy for heating. The operating conditions for each control strategy were as follows: RS-CON [24]: The T room for the heat supply was set to 291.15 K and 295.15 K for starting and stopping the heat supply system, respectively. ...
Article
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Multi-energy complementary heating (MECH) is the most promising and potential heating technology of the future. However, owing to the increase in energy types, the system is complex, and the operation procedure cumbersome. In addition, due to the uncertainty of climate conditions, it is difficult to develop a general control strategy suitable for all heating systems. In order to study the optimal control strategy of MECH systems with solar, biomass, and electric energy as three heat sources in cold regions, the system heating was tested over different periods during the entire heating season for rural residential buildings in cold regions, and the operating performance of the system was evaluated. The MECH experiment, based on the optimal control strategy, was compared with other different heating systems, and the economic and environmental benefits of the system were further evaluated. The results showed that, compared with room temperature control strategy (RS-CON), the control strategy of the heat storage tank (HST-CON) with sufficient solar energy (SE) can afford a higher solar fraction by 10%, more HST heating hours, and lower operating costs and CO2 emissions. During heating operation, Mode 3 [biomass boiler (BB) + heat storage tank (HST) heating] was the best heating mode. At the end of the heating period, Mode 5 (HST heating) met the indoor heat demand and had a significant energy-saving effect. From the perspective of the whole heating season, HST-CON heating operation can generate lower energy consumption costs and achieve almost zero CO2 emissions. This study is of great significance because it provides an engineering reference for the rational the utilization of MECH systems in cold regions.
... The installation of balancing valves can also reduce occupants' complaints and enable reduced heating system temperatures in cases with insufficient heating or high return temperatures in some zones [96]. Lastly, pre-settings appropriately limit the water flow through individual heating elements, which is vital for low-temperature operation, as it helps to limit the consequences of inappropriately operating thermostats as open/close valves or with intermittent temperature set-point schedules [97,98]. Otherwise, both misuses can cause extreme flows with high return temperatures during re-heating periods that significantly impact the overall heating system temperatures [99]. ...
Article
Full-text available
District heating networks increasingly rely on heat pumps, condensing biomass boilers, and excess heat in the transition to sustainable energy systems. Accordingly, district heating operators seek to reduce their networks’ supply and return temperatures to maximise production efficiencies, minimise heat losses from distribution pipes and allow greater utilisation of renewable heat sources and excess heat. Experts have predicted that investing in solutions that reduce heating temperatures in buildings will yield a return on investment of 300% for district heating operators. Therefore, expecting incentives, building operators should identify methods to reduce supply and return temperatures to enable a rapid, widespread transition to low-temperature district heating. Ample research has investigated and documented the feasibility of low-temperature heating in buildings, and this paper presents the first comprehensive review. It synthesises available literature and adds new perspectives to help guide future implementation, research and development of low-temperature heating. The energy and temperature demands of various heating systems provides a background, leading to a review of typical malfunctions and their impacts. The article subsequently reviews the obtainable supply and return temperatures before and after renovating the building envelope and heating systems. It further identifies and summarises vital measures for decreasing heating system temperatures. Ultimately, the authors recommend minimising heating system temperatures using automatic balancing of space heating and ventilation systems, novel solutions for safe domestic hot water supply, and digitally-enabled performance monitoring and optimal control.
... It is important that energy-saving will not compromise thermal comfort. We hypothesise that the lowest possible HC is different if all radiators are controlled by thermostats with a correct setpoint of about 21 °C or if some thermostats are fully open, as can be the situation in practice [13][14][15]. In the latter case, the heat will be redistributed from overheated rooms to other apartments because internal walls and slabs are not insulated, which could allow further reduction of the heating curve. ...
Article
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In this research, an existing building calibrated simulation model from 1981 was built based on measured energy and indoor temperature data. The model was used to study the central control's energy-saving potential. With parametric simulations, DHW circulation internal heat gain and ventilation airflow rate was determined as 85% and 0.29 l/s/m², respectively. DHW circulation heat loss has been found almost as high as DHW use. Dropping the heating curve from 70/40 °C to 65/35 °C resulted in a saving of 0.6 kWh/m²a (0.8% of space heating energy) on the cost of thermal comfort as yearly hours of the mean air temperature below 21 °C rose from 2.7% to 9.0%. It was necessary to reduce the heating curve to 55/25 °C in a hypothetical scenario with fully open thermostats, indicating heat redistribution from warmer to colder rooms, leading to higher heating energy. The findings indicate no energy saving potential due to compromising thermal comfort even by 5 °C heating curve reduction. It was revealed that the building average indoor temperature is not a factor to estimate energy-saving potential because of too low temperature in the coldest apartments.
... In line with these, Ionesi et al. [11] propose a self-adaptive algorithm with learning abilities to adjust the weather-compensation curve. Liao et al. [13] point out the necessity for proper commissioning with selection of the weather-compensation curve as to the site in focus, highlighting the possible risk that the DH performance can be poorer than a constant supply temperature strategy. Same is also described by Ionesi et al. [11] that (i) an unnecessarily broad-covering curve can maintain the thermal comfort but with undesirable high indoor temperature possible at some cases while (ii) an inferior curve leads to thermal discomfort. ...
Article
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The paper presents a novel demand-responsive control strategy to be equipped centrally at the district level for district heating systems. The demand-responsive feature was maintained as to both the direct and the indirect substation configurations (by basing on their rating measures) in order to achieve lowest possible return temperature degrees from the end-user substations. Different than the traditional weather-compensation based supply temperature resetting, the new control strategy was formulated to adjust the supply temperature at the district level as to the cooling performance at the end-user substations. Two different simulations were carried out in order to quantify the benefits of the novel control strategy as compared to the traditional weather-compensation, equipped both at the substation level and the district level. The results obtained showed that the new control strategy, when considering the electricity loss at the heat production plant, shows superiority when compared to other control strategies.
... According to the research results, energy savings were determined based on the average heat consumption before and after modernization, depending on the type of installed valves or their combination. In [7], the results of an experimental study are presented showing that the use of manual balancing valves reduces the energy efficiency of the system. This circumstance is caused by the fact that the comfort temperature is not maintained inside that leads to overheating and excessive fuel consumption. ...
Article
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Energy conservation and improving energy efficiency are priority areas for the development of the global economy. The need to increase the energy efficiency of the engineering equipment of buildings is due to both the requirements to reduce the energy consumption of buildings in general, and the increase in the proportion of energy-consuming climate systems used in modern construction. In large modern office, hotel and residential complexes to achieve the greatest energy efficiency it is necessary to use various technical solutions. The main element of an energy-efficient heating system is regulation. Balancing devices allow to not only balance and tune the system at any time of operational period but also serve as stop valves during reparation and diagnostics. Determination of energy savings bases on the average value heat consumption before and after modernization, depending on the type of installed valves or their combination. The focus of the work is hydraulic calculation of the heating system the authors conduct research on the effect of differently balancing fittings on the hydraulics of the heating system.
... The problem becomes more significant when the operation of the TRVs is problematic. There are several studies [12,[19][20][21][22][23][24][25] indicating that the optimal operation of the TRVs is affected by faults and misuse by the users. Several fully opened TRVs can cause an imbalance in the system: If the radiator in the lowest position of a riser in a multi-family building has a fully open TRV, a high flow can run through the radiator with a very small pressure drop. ...
Article
Full-text available
Low-temperature district heating will play an important role in a future free of fossil fuels. This will only be able to be realized through the low-temperature operation of heating systems in existing buildings. Existing radiator systems can operate with low temperatures for most of the year because they are designed for extremely cold days, but errors have to be corrected and the control of the radiator systems needs to be improved. In this paper, we present a strategy to achieve low-temperature operation from the radiator system of a multi-family building in Denmark without a pre-setting function in the thermostatic radiator valves. The strategy is based on operating the system with a combination of a minimum supply temperature and small temperature differences over the radiators. The operation of the system is analyzed through a thermal-hydraulic model. A minimum supply temperature weather compensation curve was calculated and implemented in the central supply temperature control. Return temperature measurements in the substation, the risers, and several critical radiators were performed before and after the implementation of the strategy. The measurements confirm that a lower supply temperature results in a reduction of the return temperature. However, the system operator needs to be supported by a tool package to correctly maintain the system's operation.
... The case study models a terraced house with a multizone thermostat and night set back and concludes that optimal efficiency can be achieved when a flexible heating design is used, which is able to cope with large variations in heating load. A very similar study was performed by Liao et al. [21] in a UK context, however this focused on nondomestic users and no new information is provided for UK domestic dwellings. ...
Article
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Domestic heating accounts for 64% of domestic energy usage in the UK, yet there are currently very few viable options for low carbon residential heating. The government’s carbon plan commits to improving the uptake of district heating connections in new build dwellings, but the greatest carbon saving can be made through targeting traditional housing stock. This paper aims to quantify the potential carbon and energy savings that can be made by connecting a traditional tenement building to a district heating scheme. The study uses a transient system simulation tool (TRNSYS) model to simulate the radiator system in a tenement block and shows that a significant benefit can be achieved by reducing the supply temperature; however, the minimum supply temperature is drastically limited by the building condition. Therefore, the study also critically compares the benefits of a lower supply temperature against minor refurbishments. It was found that improving building conditions alone could offer a 30% reduction in space heating energy consumption, while building improvements and integration of a river source heat pump could offer almost a 70% reduction. It is the recommendation of this study that a dwelling be improved as much as economically possible to achieve the greatest carbon and energetic savings.
... The operating perfor- mance of heating systems need to be improved and personal heating devices are suggested to provide to occupants in areas with relatively low air temperature, including electric radiators, heating chair cush- ions, etc. Thirdly, overheating in winter was pervasive throughout three climate zones, especially in Cold zone. Thus, the set point for heating is suggested to be lower in Cold zone to reduce the waste of overheating [64], though there may be a risk of decreasing occupant satisfactions on thermal environment in winter. ...
... Several groups of researchers carried out surveys on the thermal control strategies in buildings [1] [2] [3]. Their studies were, typically, based on thermostatic valves on radiators (TVR). ...
... Occupant induced internal gains are modeled using the stochastic occupancy model StROBe, developed in Python and described in [28]. However, a deterministic schedule is used for the room thermostat as given in table 3. The variation in indoor air temperature that is allowed to activate the thermal mass during the ADR-event is limited to maximum 2 • C, corresponding to the variation observed for traditional heating control [29]. Thereby it is noted that the allowed deviation for ADR is always compared to the temperature setpoint of the occupied period. ...
Article
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The use of structural thermal storage is often suggested as a key technology to improve the penetration of renewable energy sources and mitigate potential production and distribution capacity issues. Therefore, a quantitative assessment of the energy flexibility provided by structural thermal energy storage is a prerequisite to instigate a large scale deployment of thermal mass as active storage technologies in an active demand response (ADR) context. In the first part of the work, a generic, simulation-based and dynamic quantification method is presented for the characterization of the ADR potential, or energy flexibility, of structural thermal energy storage. The quantification method is based on three ADR characteristics – i.e. available storage capacity, storage efficiency and power-shifting capability – which can be used to quantify the ADR potential in both design and operation. In the second part of the work, the methodology is applied to quantify the ADR characteristics for the structural thermal energy storage capacity for the different typologies of the Belgian residential building stock. Thereby an in-depth analysis demonstrates the relation between the building properties and its energy flexibility as well as the dependence of the energy flexibility on the dynamic boundary conditions.
... For example, Peffer et al. [7] undertook a review of thermostat studies in North America and found reported energy savings from the use of programmable thermostats varying from zero to 9%. 1Liao et al. [8] reviewed current practice regarding control of heating systems in residential buildings in the UK and Peeters et al. [9] undertook a similar study in Belgium. In both cases, they demonstrated the inefficiency of many installations, and concluded that overall efficiency is affected markedly by the boiler size, the choice of boiler control, whether weather compensation is applied, and the particular configuration of a control thermostat and TRVs. ...
Article
Energy is wasted in domestic buildings when rooms that are heated are not occupied. Allowing those rooms to cool reduces the inside – outside temperature difference and therefore rate of heat loss, resulting in an energy saving. This suggests a cost effective way to upgrade an existing modern heating system, especially in older properties where other energy saving possibilities are limited. Assessing the savings achievable requires an analysis of a range of influencing factors, such as house type and age, location and occupancy patterns. Door opening has a major influence due to the impact on air exchange between heated and unheated zones in a house, so this was also considered.
... The lack of temperature distinction between seasons apparent in some homes supports this premise and demonstrates a potential energy component of overheating in modern housing. This may be attributed to a number of factors associated with energy-efficient housing, including: greater occupant expectations (Herring & Roy, 2007;Howden-Chapman et al., 2007), improved fabric performance (with no subsequent change in heating behaviour), oversized and/or poor control of heating systems (Liao, Swainson, & Dexter, 2005), and low ventilation rates in practice (Sharpe, McQuillan, Howieson, Farren, & Tuohy, 2014a;Sullivan et al., 2013). ...
Article
Despite growing concerns about overheating, a lack of evidence exists on the scale of the problem, particularly in contemporary UK housing. This paper presents the results of a meta-analysis of indoor temperatures in selected low-energy housing. Temperature data recorded at five-minute intervals in 60 dwellings across 19 demonstration projects (2012–14) were collated and analysed to investigate the prevalence of overheating. Findings evidence high summertime temperatures, with 27% of living rooms exceeding 28°C during August. Based on the Chartered Institution of Building Services Engineers (CIBSE) threshold of 5% annual occupied hours > 25°C, 57% of bedrooms and 75% of living rooms were classified as having overheated. Overall, 30% of living rooms exceeded the adaptive comfort threshold of > 3% occupied hours ΔT ≥ 1 K. The results suggest a fundamental relationship between ventilation and indoor temperatures. The higher minimum and average summertime temperatures observed in mechanical ventilation with heat recovery (MVHR) homes (p < 0.05) and lower temperature range (p < 0.001) suggest the need for greater attention to adequate summertime ventilation provision in airtight homes. The results demonstrate a high prevalence of overheating in exemplary housing, indicating the need for greater efforts to ensure the effective implementation of strategies to minimize overheating and improve ventilation in low-energy homes.
... Installing condensing high efficiency boilers rather than standard ones, improve control management [2] [3] and rightsizing boiler capacity [4] [5] has been shown to produce a great effect on boilers energy consumption and efficiency on field. ...
Article
Full-text available
Domestic gas boilers on the market are able to modulate up to a modulation ratio equal to 10, in the present work the convenience of adopting modulation ratios up to 40 has been assessed.A methane condensing domestic boiler has been set up to work over the nominal modulation range up to 15, so that a consumption and efficiency experimental characterization has been carried out and numerically extended to 40. A bin method based model has been implemented in order to estimate the modified boiler consumption for different scenarios.Increase the modulation ratio improves the overall boiler efficiency by reducing cycling losses yet rises the operating time and the electrical consumption, accordingly, in the present work a comprehensive analysis has been performed to identify optimal “ultra-modulating” ratios for different climates and buildings.
... A systematic study, both theoretical and experimental, can be seen in (Liao et al., 2005). The study is very critical with the results of this type of heating control systems in the UK. ...
Conference Paper
This paper introduces a tool for teaching control strategies and design techniques, using thermal systems as problem domain. A radiator-based heating system has been simulated. Different system components are modelled, as well as the heating dynamics of a building. The tool can find room temperatures as a function of its structure and the selected control strategies as well. A useful interface with a real heating system has been also developed, such that a remote supervisory control can be managed. The aim is to help both teachers and students when they work on the control techniques involved in energy saving.
... In previous works (Mathews et al. 1999;Riederer 2002;Stec et al. 2005) the authors applied different methods to analyse and study the problem in specific systems. In this sense, a systematic study, both theoretical and experimental, can be found in (Liao et al. 2005). Important contributions in this field include a modular thermal model with heat transfer between zones, affording a system of stochastic differential equations with statistical estimation of their parameters (Andersen et al. 2000), and a recent work with a model predictive control strategy (Shui et al. 2006). ...
Conference Paper
In this work a systematic procedure for the modelling and simulation of an HVAC (Heat Ventilating and Air Conditioning) thermal system is reported. The dynamic behaviour of each element, not only on its own but also as part of the whole process, is analysed and tested. The basic principles of energy conservation and heat transmission are applied to model the various processes that usually occur in thermal installations. An experimental building was used to evaluate the proposed energy control; it was also used to identify methods for modelling both particular elements and the whole system. Following validation of the model, new control strategies for the process, with classic and advanced algorithms and procedures, are proposed with a view to achieving both comfort and important energy savings.
... The main consequences are temperature non-uniformities and drifts around set-point, leading to additional losses through the building envelope. Nowadays, building thermal control is generally performed by room thermostats or thermostatic valves on radiators [9][10][11] driven by on-off, and in the best cases, PID logics to ensure desired indoor temperature and, at the same time, minimize overheating phenomena. In spite of their diffusion, these controllers are not conceived for optimal performance in heating applications neither in terms of energy saving nor in terms of internal comfort. ...
Article
Full-text available
This paper investigates and compares the energetic and ergonomic performance of three different control logics (on-off, PID, fuzzy), used to regulate the emission of the heating system of an energy-efficient building. Tests were carried out on an experimental building, equipped with three electric radiators and a sensor network mapping internal, external and surface thermal conditions. The building-technical system ensemble was evaluated in real time for a monitoring period of five/six days of non-occupancy, winter/midseason weather and Mediterranean climate. All controllers were assessed with regard to thermal comfort and energy consumption in order to return an exhaustive scenario of possible strengths and weaknesses. The comparison showed that fuzzy logic, properly configured, outperformed both PID and on/off controllers reducing energy consumption of 30-70% and maintaining thermal dissatisfaction between comfort limits for all the monitoring period.
... Moreover, it has been shown that both in Sweden and internationally, secondary systems are often oversized [14][15][16][17][18] and are thereby capable of supplying enough heat to provide comfortable indoor temperatures at lower supply temperatures than their design values. The second reason for high primary supply temperatures is the occurrence of temperature faults in substations and secondary systems, and the only option for district heating operators to maintain the heat supply for all customers is to increase the supply temperature. ...
Article
Full-text available
Current temperature levels in European district heating networks are still too high with respect to future conditions as customer heat demands decrease and new possible heat source options emerge. A considerable reduction of temperature levels can be accomplished by eliminating current faults in substations and customer heating systems. These faults do not receive proper attention today, because neither substations nor customer heating systems are centrally supervised. The focus of this paper has been to identify these faults by annual series of hourly meter readings obtained from automatic meter reading systems at 135 substations in two Swedish district heating systems. Based on threshold methods, various faults were identified in 74% of the substations. The identified faults were divided into three different fault groups: Unsuitable heat load pattern, low average annual temperature difference, and poor substation control. The most important conclusion from this early study of big data volumes is that automatic meter reading systems can provide proactive fault detection by continuous commissioning of district heating substations in the future. A complete reduction of current faults corresponds to approximately half the required reduction of the current temperature levels in the effort toward future low-temperature district heating networks.
... Authors in [27] showed that 142 even in the non-renovated houses in Denmark, it is enough to supply DH water at a temperature 143 of 67°C. International studies [27][28][29][30]showed that there is an over-sizing of around 20 – 30% of 144 DH systems and also of radiator systems, since designers want to be sure that the system provides 145 enough heat. This can be the reason for further reductions in DH temperatures. ...
Article
European Directive 2010/31/EU stated that by the end of 2020 all new buildings should be nearly Zero-Energy Buildings (nZEB). Since such buildings require a low quantity of energy for heating, they can utilize energy from the return line of a District Heating (DH) system. Further, this new type of buildings can successfully be integrated into the fourth generation of heat distribution technology, which is the new trend in the DH industry. On the other hand, existing building stock has a service lifetime of around 50 years, indicating that the required supply temperature in the DH system cannot be lowered beneath a certain level. Hereafter, together with new types of buildings and different policies, this could lead to changes in heat demand profiles of the DH system.
... The thermal inertia of the heating systems, for example, is not taken into account in the EPB calculation. The available dataset did not allow further investigation into these hypotheses, but other studies focusing on heating system efficiencies confirm the importance of intermittency, emission systems, sizing and thermal inertia on the total efficiency of heating systems, while these are not taken into account in the EPB calculation (Liao, Swainson, & Dexter, 2005 ...
Article
How accurately can official energy performance calculations assess the real energy use in high-performance houses? This question was investigated by analysing 537 dwellings. Data on building characteristics and calculated performance from the Flemish Energy Performance of Buildings (EPB) database were complemented with data from energy utilities and surveys of inhabitants, their socio-demographic characteristics and user behaviours. While the real and theoretical energy uses were strongly correlated, the official calculation method overestimated the heating energy use of most houses while neglecting important electricity end uses. The prediction error varied strongly between individual cases. Two options within the calculation procedure had a significant impact on these prediction errors: the use of default values for the air tightness of the building envelope and the reported return temperature of the space heating system. The simplified calculation of net domestic hot water consumption and the real heating of the master bedrooms also affected prediction accuracy. However, extrapolations are hazardous due to the risk of selection and non-response biases implied by the approach and the need for further research into the causalities. Nonetheless, the findings stress the importance of accurate input data and realistic default values for calculation models used for high-performance buildings.
... According to [3], 95% of radiators were controlled using TRVs (thermostatic radiator valves). It was found that majority of TRVs failed to reduce the heating output once the room temperature is greater than the setpoint as a result energy was wasted. ...
Conference Paper
Full-text available
In this paper, we propose a novel variable setpoint RNN controller for maintaining comfortable indoor environment in double storey residential building by controlling the motorised thermostatic radiator valves (TRVs) mounted on radiators. In order to monitor the indoor environmental condition of the building the sensor interface collects information from different sensors and sends this information to random neural network (RNN) controller. The RNN controller ensures comfortable environment for occupants by regulating the air temperature of the building according to the setpoint suggested by PMV index based variable setpoint estimator. The proposed RNN controller is compared with ANN controller and it is found that accuracy of RNN controller is 26% more than ANN controller and conserves 2.75% more energy than ANN controller at PMV index based temperature setpoints. The RNN controller has the capability to adjust the room temperature to lower setpoints (not included in the training data) while ANN controller failed to maintain accurate comfortable environment for the operating points not covered in the training data. The results show that the percentage of accurate air temperature regulation for RNN controller is 95.69% while for ANN it is 2.22%.
... Control is frequently effected via control algorithms. They vary in complexity from digital versions of simple on/off, PID (proportional -integral -derivative), or optimum start/stop control, to advanced model-based control formats such as adaptive or predictive methodologies (see, for example, Liao et al., 2005). To date, such condition monitoring and control systems are usually restricted to commercial buildings, and there remains scope for their introduction into the domestic sector. ...
Thesis
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The domestic sector currently accounts for approximately a third of the UK’s energy use and so energy demand reduction in the domestic sector is a key part of the UK’s strategy for carbon reduction. However, energy demand reduction has typically been addressed from an engineering perspective, with little consideration of the requirements of users. This PhD submission aims to identify how qualitative information about users’ experiences, values and practices relating to UK domestic energy demand reduction can be collected and presented effectively to an engineering audience and incorporated into engineering-focused energy research. User centred design is presented as a viable approach to understanding the context of energy use in UK homes and specifying requirements of the householders; as a way of ensuring user needs are included in this socio-technical problem space. This requires presentation of information about human behaviour in a form that is timely and appropriate to the engineering audience, who take a positivist view, preferring facts and figures to descriptions and anecdotes. A collection of nine publications, mostly peer-reviewed journal papers, by the thesis author and her co-authors is presented. Publications spanning from 2006 to 2014 illustrate a range of approaches to providing user centred information, from literature review to complex householder studies, which can provide information to enhance the engineering data and so provide additional insight and understanding. The research findings within the individual papers add to the body of knowledge on domestic energy use. In addition, the research identifies a number of roles where user centred design contributes to understanding of home energy use. From providing background and raising awareness of the presence of users within a system, to contextual understanding and the specification of user requirements, through to more sophisticated user characterisation, it is argued that user centred design can offer a significant contribution to the field. Future application of user information into engineering models, together with large scale, longitudinal studies of home energy use are proposed, building on the contributions of this thesis.
... Therefore, almost two-third of the energy savings in dwellings seems achievable through space heating. Furthermore, the operation control of many heating systems (boilers and heat emitters) in use in the UK is found to be inefficient [4,5]. Novel efficient systems therefore are in a real demand for UK market as well as other countries with long heating seasons. ...
Conference Paper
Full-text available
In response to climate change, energy poverty, and increasing prices of fossil fuel energy; building integrated renewable energy should find a quick and strong stream in design and construction fields. Solar thermal appears as a promising technology for domestic and non-domestic building envelopes, particularly for space heating which counts for 61% the total domestic energy consumption in countries with long cold seasons like UK. The integration of transpired solar collectors (TSC) technology however suffers lack of adoption in building envelopes despite its apparent technical competitiveness for using solar pre-heated external air for space heating since patented in the late-1980s. Architectural integration seems to play a major role in developing and encouraging the use of TSC in buildings. This paper therefore investigates the innovative possibilities of improving the architectural integration of TSC into building envelopes at both multi-functional and aesthetic levels. An international web-based survey was distributed to architects, engineers, and other academic and professionals in design and construction fields with intensive focus on countries with long heating seasons and potential integrations of TSC such as Canada, USA, and UK and mainland Europe. The responses of 1,295 participants, the largest pool ever for previous comparative studies in this field, were analysed quantitatively and qualitatively. Unlike previous studies the outcomes were statistically examined using Pearson's Chi-square and Spearman's correlation Coefficient tests. Although respondents only had a moderate awareness of the TSC technology they were very interested in integrating solar energy into the built environment. Seven selective integration images of TSC and photovoltaic (PV), from existing projects in Canada, USA and Europe were rated by respondents in terms of multi-functional and aesthetic roles of integration. The barriers and limitations along with preferable integration schemes were investigated and discussed. Integration parameters such as function, type, and position of TSC which were found to be the most favoured by the participants were identified. The survey results provide valuable contributing information of architecturally integrating transpired solar thermal in the built environment. This contribution is necessary for researchers and professionals in design and construction fields.
... While many fabric-based and equipment-based interventions are needed, controllers for residential heating systems could play a useful part without compromising the occupants comfort. According to [4], 95% of radiators were controlled using thermostatic radiator valves (TRVs). It was found that majority of TRVs failed to reduce the heating output once the room temperature is greater than the setpoint, as a result energy was wasted. ...
Conference Paper
Random neural networks (RNN) have strong generalisation capabilities and are easy to implement on hardware as compared to Artificial Neural Networks (ANN). In this paper, a novel RNN controller is proposed to maintain a comfortable indoor environment in a single zone residential building fitted with radiators for heating. This controller is capable of maintaining a comfortable indoor environment on the basis of a predicted mean vote (PMV)-based set point. The implemented RNN controller is compared with ANN controller for energy consumption, indoor room temperature, and minimum square error. Results show that for same training data and learning algorithm parameters, RNN converges faster and it consumes less energy, results in better comfortable room temperature as compared to ANN controller.
Article
Residential thermostat control is considered to be an effective way to allow individual regulation, and to encourage energy saving behavior. However, energy savings resulting from occupants’ regulating behavior still needs to be quantified. We investigated several district heating systems that had thermostatic radiator valves (TRVs) installed, in Beijing and Tianjin, and evaluated the energy saving ratio, and the influence of heat transfer from adjacent apartments for four typical regulation scenarios. To separate out the effects of the occupants’ regulation, a reference analysis method is proposed for comparison. Results indicate that when an individual occupant adjusted the TRVs according to a daily schedule for intermittent heating, the energy saving ratio was only about 6%. When the TRVs of an apartment are kept closed for a long unoccupied period (more than 4 days), the daily energy saving ratio was about 20%, and the total quantity of heat transferred from adjacent apartments was about 80% of the heat consumption of the reference apartment. In addition, when the TRVs were kept at a set-value (such as 3), energy saving ratios of about 12% were obtained. The results of this study provide further data for developing better management policies for heating terminal customization.
Article
Conventional district heating (DH) substations in China use a feed-forward adjustment method that predicts the water supply temperature based on the outdoor temperature. This method does not consider the delay of the pipe network and the thermal inertia of the building. Most importantly, the lack of closed-loop feedback on the indoor temperature results in high energy consumption and large fluctuations in room temperature. In this study, a predictive feedback system based on effective temperature control has been proposed to improve the quality of district heating. First, a dynamic simulation control model of a DH substation was created based on measured data. Then, through dynamic simulation analysis, the influence of the heating network delay on the room temperature was observed to be smaller than the influence of the building's thermal inertia, which confirmed that predictive feedback control based on effective temperature could be achieved. Finally, the new control method was compared to two conventional control methods. Based on the comparison with the two conventional controls, refining the timespan of the feed-forward control was found to be ineffective for improving room temperature stability owing to thermal inertia. The new control method demonstrated high control flexibility and strong anti-interference, and the indoor temperature fluctuation decreased from ±1.1 °C to ±0.3 °C compared with conventional control methods. In this case, under the premise that thermal comfort is not affected, the room temperature setting can be reduced by 0.5 °C, resulting in an energy saving of 6.1%, with a payback return period of less than a year. This method only requires installing room temperature sensing equipment and linking the feedback control algorithm to the original control system and is therefore easy to achieve.
Article
Full-text available
Automated hydronic balancing in space heating systems is crucial for the fourth-generation district heating transition. The current manual balancing requires labor- and time-consuming activities. This article presents the field results of an innovative electronic radiator thermostat tested on two Danish multi-family buildings. The prototypes had an additional return temperature sensor on each radiator and an algorithm was used to accurately control valve opening to ensure automated hydronic balancing. The results highlighted that the new thermostat performed as expected and helped secure the cooling of district heating temperatures —defined as the difference between supply and return temperature—4–12 °C higher during the test compared to results obtained in 2020, when the prototypes were replaced with state-of-the-art thermostats in the first building. The measurements from the other building illustrated how only two uncontrolled radiators out of 175 could contaminate the overall return temperature. The remote connection of the thermostats helped pinpoint the faults in the heating system, although the end-users were not experiencing any discomfort, and secure, after fixing the problems, a return temperature of 35 °C. Future designs may consider integrating a safety functionality to close the valve or limit the flow in case of damage or malfunction to avoid a few radiators compromising the low-temperature operation of an entire building before the cause of the problem has been identified.
Article
Poor indoor temperature control level is the most common issue of building space heating in Chinese district heating system (DHS). The aim of this study was to provide on-demand heating for the buildings. A temperature and time-sharing dynamic control approach was developed by integrating three energy-saving heating patterns. Given that different heating patterns had different set temperatures, unreasonable patterns switching time would cause indoor temperature to deviate from set value. To address this issue, equivalent thermal capacity of building was introduced to establish an indoor temperature prediction model and to determine the appropriate switching time. The practical application of proposed approach was based on the control system with wireless indoor temperature monitoring. A group of buildings with the same demand temperature could be controlled by one control system. A DHS in a university was selected as a case study to validate the proposed method. The experimental works include short-term and long-term validation. Short-term daily comparative experiments showed that the approach could yield heat-saving and heating on-demand for different buildings. Four heating seasons’ long-term operation data indicated the approach could save annual heat use by 14.6%∼28.7%. The energy-saving effect also yielded considerable economic and environmental benefits.
Article
Through a large-scale questionnaire survey across China and indoor physical measurements of typical cities in the four climatic zones, this study investigates the current status and retrofitting priorities of the IEQ of existing public buildings in China. The public buildings in China mainly present uneven indoor hot and cold distributions and draft sensations. The utilization ratio of natural light is low, and glare often exists. HCHO and TVOC are not major concerns of indoor air quality, but affected by the region and season, the PM2.5 and PM10 concentrations exceed the limits of the Chinese standard. All the buildings present excessive noise. Respondents generally demand improved indoor air quality and thermal environment, and different control strategies should be adopted across regions with different local climatic conditions and behavioural habits. For the thermal environment, the indoor air distribution should be optimized and the indoor humidity ratio increased in winter in northern regions of China. For the luminous environment, the indoor illuminance value should be decreased and the lighting quality improved. For the acoustic environment, the sound insulation and sound absorption performance of the building envelope should be improved. For indoor air quality, the purification capacity of the air conditioning system and the airtightness of the building envelope should be strengthened. According to the outdoor air quality, different channels can be opened to introduce fresh air. For example, when the outdoor air quality is good, fresh air can be directly introduced to improve the service life of the filtering system and reduce energy consumption.
Article
This study investigates the return on investment (ROI) of building energy management system (BEMS) through reviewing research works published from 1977 to 2017. The ROI is quantitatively evaluated by payback periods of BEMS cases. The results indicated that the BEMS payback periods decreased from 5.4 to 0.7 years for commercial buildings. For compound buildings, the BEMS payback periods were shortened from 3.7 to 1.8 years. For residential or office buildings, the BEMS payback periods could not be effectively shortened. Therefore, the BEMS for the commercial and compound buildings had the better energy savings and ROI. An ROI model, based on four characteristic parameters of buildings and four major BEMS technologies, is built. The calculating results indicate that the most effective technology to increase the ROI of BEMS is the scheduling control technology developed for the heating, ventilation, air‐conditioning, and refrigeration system of buildings. The future development of BEMS should focus on (1) scheduling control, (2) collecting the managing information through Internet, and (3) combining the mobile communicating devices for interacting with the occupants in the building. Therefore, using BEMS would be a worthwhile choice for most commercial buildings.
Article
This paper presents results of a research study into improving energy performance of small-scale district heat network through water supply and return temperature optimization technique. The case study involves establishing the baseline heat demand of the estate’s buildings, benchmarking the existing heat network operating parameters, and defining the optimum supply and return temperature. A stepwise temperature optimization technique of plate radiators heat emitters was applied to control the buildings indoor thermal comfort using night set back temperature strategy of 21/18 °C. It was established that the heat network return temperature could be lowered from the current measured average of 55 °C to 35.6 °C, resulting in overall reduction of heat distribution losses and fuel consumption of 10% and 9% respectively. Hence, the study demonstrates the potential of operating existing heat networks at optimum performance and achieving lower return temperature. It was also pointed out that optimal operation of future low temperature district heat networks will require close engagement between the operator and the end user through incentives of mutual benefit.
Article
This study presents a method to adapt existing hydronic systems in buildings to take advantage of low temperature district heating (LTDH). Plate radiators connected to double string heating circuits were considered in an optimization procedure, based on supply and return temperatures, to obtain the required logarithmic mean temperature difference (LMTD) for a low temperature heating system. The results of the analysis are presented as the average reduction of LMTD over the heating season compared to the base case design conditions. Two scenarios were investigated based on the assumption of a likely cost reduction in the end users' energy bills of 1% for each 1 °C reduction of return and average supply and return temperatures. The results showed possible discounts of 14% and 16% respectively, due to more efficient operation of the radiators. These were achieved without any intervention in the thermal envelope or to the heating systems, through simply adjusting the temperatures according to demand and properly controlling the plate radiators with thermostatic radiator valves (TRVs).
Conference Paper
This paper presents an optimal strategy for thermal control of a real building. The control algorithm uses a strategy based on model predictive control MPC (Model Predictive Control). In this control strategy, in order to improve system performance regarding the comfort and the energy consumption, weather forecast and occupancy of the building program are taken into consideration. To achieve optimal control of a building or to characterize its energy performance, one of the steps to follow is experimental identification of the dynamic model for heat transfer of that building. Using such a calculated model for the presented house, the implemented strategy provides better outcomes than other control solutions based on classical PID controllers.
Article
To assess the impact of interventions designed to reduce residential space heating demand, investigators must be armed with field-trial applicable techniques that accurately measure space heating energy use. This study assesses the feasibility of using a passive acoustic sensor to detect gas consumption events in domestic combination gas-fired boilers (C-GFBs). The investigation has shown, for the C-GFB investigated, the following events are discernible using a passive acoustic sensor: demand type (hot water or central heating); boiler ignition time; and pre-mix fan motor speed. A detection algorithm was developed to automatically identify demand type and burner ignition time with accuracies of 100% and 97% respectfully. Demand type was determined by training a naive Bayes classifier on 20 features of the acoustic profile at the start of a demand event. Burner ignition was determined by detecting low frequency (5-10 Hz) pressure pulsations produced during ignition. The acoustic signatures of the pre-mix fan and circulation-pump were identified manually. Additional work is required to detect burner duration, deal with detection in the presence of increased noise and expand the range of boilers investigated. There are considerable implications resulting from the widespread use of such techniques on improving understanding of space heating demand.
Article
The energy efficiency of gas-burned boilers in space heating systems is sensitive to how the boiler is controlled. This study is aimed to investigate how the overall energy performance of a heating system can be optimized using best boiler control scheme. This is to be achieved through experimental studies and simulation studies. This paper presents the latter. A simplified boiler is proposed and integrated in a heating system modeling platform for the simulation study. The results show that the boiler in a heating system should be controlled according to the heating load in order to achieve the highest long-term energy efficiency while maintaining desired comfort.
Article
This study investigated energy saving effects of published papers related to energy management system (EMS), building energy management system (BEMS), industrial, company and factory energy management system (I/C/F/EMS); and EMS for heating, ventilation, air conditioning (HVAC) and refrigerating equipment, artificial lighting systems, motors and others (EMS for equipment). From 1976 to 2014, management performance reported by 305 EMS cases (105 BEMS cases, 103 I/C/F EMS cases and 97 cases of EMS for equipment) is analyzed to evaluate varied energy saving effects. Statistical results show that saving effects of BEMS increased from 11.39% to 16.22% yearly. Inversely, saving effects of I/C/F EMS decreased from 18.89% to 10.35%. Regarding to EMS for equipment, there is no obvious trend but only the averaged saving effect can be reported. EMS for artificial lighting systems has the highest saving effect up to 39.5% in average. For HVAC and other equipment, energy saving effects are around 14.07% and 16.66% respectively. These energy saving performances are correlated with developed EMS functions. The key EMS functions could be identified from their developing progress for effective energy savings. Based on the quantitative analysis, the future trends of EMS are discussed.
Article
Heat pumps are widely recognized as a key technology to reduce CO2 emissions in the residential building sector, especially when the electricity-generation system is to decarbonize by means of large-scale introduction of renewable electric power generation sources. If heat pumps would be installed in large numbers in the future, the question arises whether all building types show equal benefits and thus should be given the same priority for deployment. This paper aims at answering this question by determining the CO2-abatement cost of installing a heat pump instead of a condensing gas boiler for residential space heating and domestic hot-water production. The electricity system, as well as the building types, are based on a possible future Belgian setting in 2030 with high RES penetration at the electricity-generation side. The added value of this work compared to the current scientific literature lies in the integrated approach, taking both the electricity-generation system and a bottom up building stock model into account. Furthermore, this paper analyzes the possible benefits of active demand response in this framework. The results show that the main drivers for determining the CO2-abatement cost are the renovation level of the building and the type of heat pump installed. For thoroughly insulated buildings, an air-coupled heat pump combined with floor heating is the most economic heating system in terms of CO2-abatement cost. Finally, performing active demand response shows clear benefits in reducing costs. Substantial peak shaving can be achieved, making peak capacity at the electricity generation side superfluous, hence lowering the overall CO2-abatement cost.
Article
Good room temperature control is beneficial for users’ thermal comfort and health. It also helps reduce energy consumption and carbon dioxide emissions inside the buildings. However, there are certain limitations with the current thermostatic valves commonly used in central heating systems, especially the ones used in China, since they cannot satisfactorily adjust room temperatures. In response to such problems, an intelligent on-off regulation method is presented in this paper. The room temperature can be maintained by controlling the valves according to the on-time ratio predicted by this method. The on-time ratio is predicted for each cycle, and the current ratio is decided by checking a 6-order fuzzy-control table with room temperature deviations in the last step, as well as room temperature set points. Two major factors that may affect the controlling effect are also discussed: the length of the controlling cycle and the design of the fuzzy-control table. A proper controlling cycle and optimal controlling table have been worked out. Besides, the robustness and application effectiveness of this strategy have also been discussed in this paper. The results show that the room temperature can be maintained in the range of set point ±0.5 °C by using this method in different conditions. It is fair to say that this method is a stable, reliable and advanced controlling method, with robust and accurate control. © 2015, Tsinghua University Press and Springer-Verlag Berlin Heidelberg.
Conference Paper
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In this paper, a novel random neural network (RNN) model based optimization process for radiator-based heating system is proposed to maintain a comfortable indoor environment in a living room of a single storey residential building. The predictive model of the living room is developed by training a feed forward RNN and then optimisation algorithms are used to calculate the optimal flowrate for the radiators. Three optimisation algorithms: Genetic Algorithm (GA), Particle swarm optimization (PSO) algorithm, and Sequential quadratic programming (SQP) optimization algorithm are investigated to calculate the optimal control input. The accuracy of the control scheme is verified by simulations using International Building Physics Toolbox (IBPT). It was found that mean squared error (MSE) for PSO is 38.87% less than GA and the MSE for PSO is 21.19% less than SQP. The RNN model based optimization technique is further compared with model predictive controller (MPC) designed for the radiator based heating system. The comparison results showed that the proposed RNN technique minimize the energy consumption and maintains accurate room thermal comfort according to the predicted mean vote (PMV) based setpoints.
Conference Paper
In this paper, a novel random neural network (RNN) controller is proposed to maintain a comfortable indoor environment in a single storey residential building having four rooms fitted with radiators for heating. This controller considers the effect of outside temperature and solar radiations on the building and is capable of maintaining a comfortable indoor environment on the basis of a PMV-based setpoint. The RNN controller is trained with a 30 day dataset from the living room of the building and the performance of the controller is evaluated by testing the controller in all four rooms of the building for 100 days. It is found that the RNN controller is not only capable of maintaining comfortable indoor environment as suggested by PMV-based setpoint but can also adjust the room temperature to a lower setpoint (not included in the training set) required by the user for unoccupied rooms. The RNN controller is further compared with similar artificial neural network (ANN) controller and model predictive control (MPC) controller. The results show that for maintaining comfortable indoor environment, the performance of the RNN controller is approximately equivalent to the MPC controller for the setpoints not covered in the training set, while ANN controller failed to maintain accurate comfortable environment for the operating points not covered in the training phase.
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Analyze the influence of different type of pump to the stability of the central heating system with distributed variable speed pump. Propose the concept of relative back pressure. Draw the following conclusion: In the central heating system with distributed variable speed pump, regulating the same flow of the same branch, through the variable speed pump regulation or valve regulation, the influence to the stability of the system is the same. When the branch pump regulates the flow by change the speed of the pump, we should not use the proportionality law to calculate the new working condition. To the stability of the system, It is good to use the pump with more precipitous pump characteristic curve in the branch. The influence of one branch regulation to the stability of the other branches is nothing related with the regulating branch's pump characteristic curve but related with the regulated branch's pump characteristic curve and the regulating flow.
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The residential sector is responsible for more than 35% of the final energy consumption in the European Union, and is increasingly constrained by thermal regulations, resulting in a significant rise of new efficient heating technologies. This paper presents a comparison of the energetic and environmental performances of six heating systems installed in a low energy house: a gas-fired condensing boiler, a wood pellet boiler, a micro-combined heat and power (MCHP), an air-to-water electric heat pump, an air-to-water gas absorption heat pump and an exhaust air-to-air electric heat pump. The comparison is made with respect to the annual primary energy consumption and the annual greenhouse gas (GHG) emissions, and carried out under various climates and electricity generation mixes. The results indicate that, based on an ideal sizing, the MCHP and the absorption heat pump achieve the highest energy performances. However, both technologies suffer from small size unavailability, leading to significant oversizing which impacts their performances. Based on current size availability, the air-to-water electric heat pump benefits from the previous systems oversizing and thus appears as the most efficient technology. However, current sizing practice also causes significant oversizing which impacts the performances of thermodynamic systems. Without significant sizing practice improvements, the air-to-water electric heat pump merit decreases in favor of the MCHP. In terms of environmental impact, the wood boiler causes the lowest GHG emissions, whatever the electricity generation mix considered.
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The impacts of boiler control on the overall performance of multi-zone heating systems have been studied using a simulation platform. Conventional boiler controllers have been investigated to determine the potential for optimization and to identify the key variables that should be taken into account. An inferential control scheme is accordingly proposed for use in multi-zone buildings where there is no measurement of the internal air temperature. The scheme estimates the overall average room temperature from available information, including boiler ” ring signals, external temperature and solar radiation. The output of the estimator is fed back to a PI controller that determines the hot water supply temperature setpoint. The estimator has been validated using experimental data obtained from different sources. It has been shown in simulation that this control scheme can signi” cantly reduce the energy consumption of heating systems and improve the overall control performance in terms of the thermal comfort.
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The problem of controlling the start-up of heating plant in industrial and domestic buildings is considered and the need for a self-tuning start control scheme is explained. Using a simple semi-empirically derived relationship between the time required to preheat the building before occupancy and the measured temperatures, a self-tuning start controller is developed based on an on-line adaptive predictor. The controller assumes no prior knowledge of the thermal characteristics of the heating plant and building, and is suitable for low-cost microprocessor implementation. Results obtained from a hybrid simulation of a heating plant, building and environment show that the self-tuning controller behaves well and has superior performance characteristics compared to conventional start controllers. The results of preliminary experimental tests, using a microprocessor-based controller, suggest that, in certain circumstances, further simplifications to the control algorithms can be made so that implementation on small single-chip microcomputer systems, which are suitable for the control of domestic heating equipment, is feasible.
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This paper describes the development and testing of a new optimum start algorithm for control of heating plant in conventionally heated buildings. The algorithm which is based on detailed thermal response data from several UK buildings, exhibits more accurate and consistent performance than commercially available optimisers. Main features of the algorithm include a new empirically based non-linear schedule and a fading memory least squares self learning procedure which is used to identify the optimal parameters of the schedule for each application.
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A simplified model for estimating the average air temperature in multi-zone heating systems has been developed for use in an inferential boiler control scheme (Building Services Eng. Res. Technol. 24(4) (2003) 245), which can significantly improve the overall performance of heating systems. The model can maintain the long-term accuracy required by the control scheme as well as the simplicity in configuration and commissioning. This paper also presents the method for commissioning the model, the validation of the model using experimental data obtained from different resources, and the application of the model in the control of boilers in multi-zone heating systems.
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