No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Variable speed drive (VSD) technology applied to HVAC systems for energy saving: an experimental investigation
Abstract
Variable speed drive (VSD) technology can be introduced in heating, ventilation and air conditioning (HVAC) systems, normally sized for peak load conditions, to match actual load requirements. The paper presents a detailed assessment of the impact of the application of VSDs to HVAC components in a public building. The study was based on the data provided by a long term monitoring of the performances. As regards the electricity consumption of pumping and fans, the investigation has pointed out the achievement of a global annual energy saving of 38.9% in comparison with the alternative of a constant speed HVAC system.
... In addition to the strategies discussed, there are other energy saving technologies for HVAC systems. The recent technological advancements in terms of HVAC system designs include but are not limited to the following: demand controlled ventilation systems (Cui et al., 2020); duct sealing (Harrington and Modera, 2014); logic control and FDD systems (Zhao et al., 2019); use of microchannel heat exchangers (Khan and Fartaj, 2011); variable speed drives (Schibuola et al., 2018), and variable flow volume systems (Lu and Warsinger, 2020). According to Merema et al. (2018), demand controlled ventilation (DCV) system is one of the possible strategies that can be adopted to enhance the energy efficiency of the HVAC system by automatically adapting the airflow rate according to the actual ventilation demand. ...
... Microchannels heat exchanger has superior features in this respect due to their higher heat transfer and reduced weight as well as their space, energy, and materials savings potential over regular tube counterparts (Khan and Fartaj, 2011). Schibuola et al. (2018) opine that variable speed drive (VSD) technology is a strategy that can be introduced in HVAC systems, normally sized for peak load conditions, to match actual load requirements. In addition, Schibuola et al. (2018) disclosed that the introduction of VSD technology in HVAC system has the potential in providing a global annual energy saving of 38.9% in the electric consumption of pumps and fans if compared with the same system but with constant flow rate. ...
... Schibuola et al. (2018) opine that variable speed drive (VSD) technology is a strategy that can be introduced in HVAC systems, normally sized for peak load conditions, to match actual load requirements. In addition, Schibuola et al. (2018) disclosed that the introduction of VSD technology in HVAC system has the potential in providing a global annual energy saving of 38.9% in the electric consumption of pumps and fans if compared with the same system but with constant flow rate. Lu and Warsinger (2020) posit that a multizone variable air volume (VAV) system can save energy by directing conditioned air to different occupied zones in the home as needed. ...
Purpose
Heating, ventilation and air-conditioning (HVAC) systems account for approximately half of all energy usage in the operational phase of a building's lifecycle. The disproportionate amount of energy usage in HVAC systems against other utilities within buildings has proved a huge cause for alarm, as this practice contributes significantly to global warming and climate change. This paper reviews the status and current trends of energy consumption associated with HVAC systems with the aim of interrogating energy efficiency practices for improving HVAC systems' consumption in buildings in the context of developing countries.
Design/methodology/approach
The study relied predominantly on secondary data by analysing the relevant body of literature and proposing conceptual insights regarding best practices for improving the energy efficiency of HVAC systems in buildings. The systematic review of the literature (SLR) was aided by the PRISMA guiding principle. Content analysis technique was adopted to examine germane scholarly articles and finally grouped them into themes.
Findings
Based on the SLR, measures for enhancing the energy efficiency of HVAC systems in buildings were classified based on economic considerations ranging from low-cost measures such as the cost of tuning the system, installing zonal control systems, adopting building integrated greenery systems and passive solar designs to major approaches such as HVAC smart technologies for energy management which have multi-year pay-back periods. Further, it was established that practices to improve energy efficiency in buildings range from integrated greening system into buildings to HVAC system which are human-centred and controlled to meet human modalities.
Practical implications
There is a need to incorporate these energy efficiency practices into building regulations or codes so that built environment professionals would have a framework within which to design their buildings to be energy efficient. This energy efficient solution may serve as a prerequisite for newly constructed buildings.
Originality/value
To this end, the authors develop an integrated optimization conceptual framework mimicking energy efficiency options that may complement HVAC systems operations in buildings.
... At no-load conditions, the single speed system was more efficient than VSCs. Schibuola et.al [26], ...
... For that reason, the VSCs must be turned off at no-load condition.The HVAC system is designed at maximum load conditions, but when the system runs at partial loads, the conventional refrigeration systems will be at On/Off operation that results in more power consumption. Schibuola et.al[26] studied the A/C system for two rooms with different loads along one year at cooling and heating mode. Their EEV, and sub-cooler. ...
... Calculate Gr,l from equation (27) Calculate Re,l from equation (26) Calculate Pr,l from equation (28) Calculate hr,x from equation (24) Single-region INPUT (14) Calculate Vc from equation (13) Calculate Vf from equation (10) Calculate DH from equation (9) Calculate the convection heat transfer coefficient of the water Calculate Gw from equation (6) Calculate Acw from equation (7) Calculate Re from equation (5) Calculate hw from equation (4) INPUT (μl ,μv ,ρl ,ρv , Ps, Pc, Cpw, Cpl, Kl, Trs) ...
A variable speed compressor with different controlling methods is employed to improve the performance of the refrigeration and air condition systems by reducing energy consumption. In this thesis, the performance of the variable speed chilled water refrigeration system with an electronic expansion valve (EEV) was studied. The effect of changing the compressor speed and valve opening on the performance and stability of the system was investigated. The speed of the compressor was controlled depending on the change in the evaporator product cold-water temperature with the first control loop. The second loop was used to regulate valve opening to keep refrigerant superheat (DS) in its setting value. Two new controlling methods were presented to control the EEV
opening that achieved optimum performance at different operation conditions. The first method considered the DS was a variable value between 6.5 and 8.5°C which is estimated by an empirical equation depending on the compressor speed and the evaporator inlet water temperature with two control loops. The coupling effect between the two loops (compressor speed and valve opening) decreases system stability and performance. This was solved with a second control method with only one controlling loop to control the compressor speed while the EEV opening was estimated directly by the empirical equation which is related to the cooling load. For each controlling method, PI, PID, P-fuzzy, P+D-fuzzy, and PD-fuzzy controllers were considered. Comparison results showed high stability for the DS with a reduction in the response oscillation about 15% with the variable DS method and 35% with the direct EEV opening method compared to the constant DS at 7°C method. The DS response stability is affected the product cold
Table of Contents
II
water temperature response and system coefficient of performance (COP) which increases about 7% with variable DS method and 18% with direct EEV opening method compared to constant DS. Energy conservation was about 30% with the PD-fuzzy controller which was the best controller compared to the On/Off method.
The performance of the controlled system was examined at steady-state operation by changing the evaporator and condenser inlet water temperatures at a constant cooling load. Increasing the inlet water temperature of the condenser from 25 to 33°C decreases the COP of the system by about 42% due to the increase in the pressure ratio and compressor speed. The COP of the system increases about 6.5% with increasing the inlet water temperature of the evaporator from 15 to 19°C at constant cooling load and condenser temperature. The last tests were by changing the cooling load, evaporator inlet water flow rate, and condenser temperature to examine the controllability of the system at transient responses. The results showed good stability and at high performance with the direct EEV opening method to control the EEV and with the PD-fuzzy controller to control the speed of the compressor.
... Refrigeration systems consume about 40% from the total power [1]. With a new technology of variable speed compressor, energy saving is about 30% [2]. ...
... Heating and ventilation Air condition systems are designed at maximum load conditions, but when the system runs at partial loads, the conventional refrigeration systems becomes at On/Off operation which results in more power consumption. Schibuola et.al [1] studied A/C system for two rooms with different loads along one year at cooling and heating modes. The experimental results showed that energy saving can be increased by 38.9% using a variable speed driver for both the compressor and fans compared to single speed equipment. ...
Refrigeration and air conditioning systems consume high rates of electrical
energy of the total global power consumption. The major part of this energy
is used by compressor which is the main equipment in vapor compression
refrigeration systems. In this study, the performance of a variable speed
chilled water refrigeration system with electronic expansion valve (EEV) is
experimentally investigated. The system is composed of variable speed rotary
compressor, water cooled condenser, electronic expansion valve, and
evaporator with refrigerant R410a for one tone cooling capacity. The results
showed that the EEV opening was related to the compressor speed at limits of
refrigerant subcool and system stability to achieve better performance.
Refrigerant superheats increased with closing the EEV at constant
compressor speed. Moreover, the degree of superheat was inversely
proportional to the compressor speed at constant EEV opening. The
coefficient of performance (COP) was improved by about 2.2 to 4.0% by
controlling the EEV at constant compressor speed. Increasing compressor
speed from 1200 to 3600 rpm resulted in decreasing system COP from 5.2 to
2.35 due to the increase of the power consumed by compressor.
... The experiment involved a single unit in a range of air conditioners for real modification and tests. The choice was based on the energy efficiency of ductless air conditioners [3] published by the Taiwan Bureau of Energy. This report included 1177 air conditioner models from 49 air conditioner manufacturers. ...
... A proportional-integral-differential (PID) controller was employed for VSDs as the core of the control algorithm [3]. Figure 2 illustrates the VSD of a split-type air conditioner. ...
This study developed cloud-based artificial intelligence (AI) that could run AI programs in the cloud and control air conditioners remotely from home. AI programs in the cloud can be altered any time to provide good control performances without altering the control hardware. The air conditioner costs and prices can thus be reduced by the increasing energy efficiency. Cloud control increased energy efficiency through AI control based on two conditions: (1) a constant indoor cooling rate and (2) a fixed stable range of indoor temperature control. However, if the two conditions cannot be guaranteed or the cloud signals are lost, the original proportional-integral-differential (PID) control equipped in the air conditioner can be used to ensure that the air conditioner works stably. The split-type air conditioner tested in this study is ranked eighth among 1177 air conditioners sold in Taiwan according to public data. It has extremely high energy efficiency, and using AI to increase its energy efficiency was challenging. Thus, this study analyzed the literature of AI-assisted controls since 1995 and applied it to heating, ventilation, and air conditioning equipment. Two technologies with the highest energy saving efficiency, a fuzzy + PID and model-based predictive control (MPC), were chosen to be developed into two control methodologies of cloud-based AI. They were tested for whether they could improve air conditioning energy efficiency. Energy efficiency measurement involved an enthalpy differential test chamber. The two indices, namely the energy efficiency ratio (EER) and cooling season power factor (CSPF), were tested. The EER measurement is the total efficiency value obtained when testing the required electric power at the maximum cooling capacity under constantly controlled temperature and humidity. CSPF is the tested efficiency value under dynamic conditions from changing indoor and outdoor temperatures and humidity according to the climate conditions in Taiwan. By using the static energy efficiency index EER for evaluation, the fuzzy + PID control could not save energy, but MPC increased the EER value by 9.12%. By using the dynamic energy efficiency index CSPF for evaluation, the fuzzy + PID control could increase CSPF by 3.46%, and MPC could increase energy efficiency by 7.37%.
... The timely detection and diagnosis of HVAC faults can mitigate energy wastage and prevent complete equipment breakdown [1]. In line with this, numerous fault detection and diagnosis (FDD) strategies have been developed to address energy-saving issues, with the aim of enhancing system efficiency [2]. Extensive research [3,4] has been investigated into optimizing air handling units (AHUs) control strategies to achieve better operational efficiency. ...
Efficiency and comfort in buildings rely on on well-functioning HVAC systems. However, system faults can compromise performance. Modern data-driven fault detection methods, considering diverse techniques, encounter challenges in understanding intricate interactions and adapting to dynamic conditions present in HVAC systems during occupancy periods. Implementing fault detection during active operation, which aligns with real-world scenarios and captures dynamic interactions and environmental changes, is considered highly valuable. To address this, utilizing the dynamic simulation system HVAC SIMulation PLUS (HVACSIM+), an HVAC fault model was developed using 194 sensor signals from each HVAC component within a single-story, four-room building. The advanced HVAC fault detection framework, leveraging simulated HVAC operational scenarios with the Gramian angular field (GAF) and two-dimensional convolutional neural networks (GAF-2DCNNs), offers a robust and proactive solution. By utilizing the GAF capacity to convert time-series sensor data into informative 2D images, integrated with 2DCNN for automated feature extraction, hidden temporal relationships within 1D signals are captured. After training on nine significant HVAC faults and normal conditions during occupancy, the effectiveness of the proposed GAF-2DCNN is evaluated through comparisons with support vector machine (SVM), random forest (RF), and hybrid RF-SVM, one-dimensional convolutional neural networks (1D-CNNs). The results demonstrates an impressive overall accuracy of 97%, accompanied by precision, recall, and F1 scores that surpass 90% for individual HVAC faults. Through the introduction of the unified approach that integrates HVACSIM+ simulated data and GAF-2DCNN, a notable enhancement in robustness and reliability for handling substantial HVAC faults is achieved.
... 24. The temperature of the HWST decreased, due to the air-to-air heat pump being switched off during this period, as seen inFig. ...
... This study shows that if a VSD is used in fan motors, the return of investment is 9 months, and it causes a 53% reduction in greenhouse gas [27]. The VSD application to the fan coil system in the two library reading rooms has provided annual energy saving of 38,9% compared to the same system at a constant flow rate [28]. The VSD and variable pitch (VP) fan control methods were applied to air handling units with axial fans in a hospital in Seoul, South Korea. ...
Fans should be involved in energy efficiency studies since they are widely used in the industry. In this paper, it is aimed to introduce the fan systems and the energy efficiency studies on fan systems. In the study, parameters like flow rate, power, and pressure difference were investigated by using the experimental data obtained via energy audit. Additionally, the effects of air temperature, velocity, and frequency parameters on fan efficiency have been investigated. In the study, it was determined that the temperature increment negatively affects the fan efficiency, and the 1 m/s increase in the air velocity reduced the efficiency by % 1,088. As regards the frequency-efficiency relationship, this article has determined that reducing the frequency with Variable Speed Drive (VSD) means less fan power and as a result, VSD encounters an energy-saving but not an energy efficiency for this case.
... According to the behavior of the blowers, the power consumed by the electric motor of the fan varies as the cube of its speed [13]. There is a significant global reduction in energy consumption in HVAC (heating, ventilation, and air conditioning) systems when VSDs are employed in motors in comparison with equipment that operates at constant rotation [14,15]. Al-bassam and Alasseri [16] demonstrated a decrease of 5.8% in the combined power in a chiller and cooling tower when installing VSD in the fans of the heat exchanger in comparison with a system with dual velocity. ...
The growing global demand for energy and the costly taxes on electric energy demonstrate the importance of seeking new techniques to improve energy efficiency in industrial facilities. Refrigeration units demand a large amount of electricity due to the high power needs of the components of the system. One strategy to reduce the electric energy consumption in these facilities is pressure condensation control. The objective here was to develop a logical control model where the physical quantities in the thermodynamic process can be monitored and used to determine the optimum point of the condensation pressure and the mass flow rate of the air in the evaporative condenser. The algorithm developed was validated through experiments and was posteriorly implemented in an ammonia industrial system of refrigeration over a period of sixteen months (480 days). The results showed that the operation of the evaporative condenser with a controlled air mass flow rate by logical modeling achieved a reduction of 7.5% in the consumption of electric energy, leading to a significant reduction in the operational cost of the refrigeration plant.
... The building sector contributes to approximately 40% of overall energy demand in industrialized countries, with Heating, Ventilation, and Air Conditioning (HVAC) systems accounting for a large part of this energy consumption [1,2]. Several scientific publications have discussed the application of efficient/innovative technologies [3] and/or optimal control strategies [4] with the aim of reducing the energy demand and related greenhouse gas emissions of HVAC units. However, HVAC systems could be exposed to various abnormal faults during operation as a consequence of a failure of components, lack of correct maintenance, or wrong installation. ...
The heating, ventilation, and air conditioning (HVAC) system serving the test room of the SENS i-Lab of the Department of Architecture and Industrial Design of the University of Campania Luigi Vanvitelli (Aversa, south of Italy) has been experimentally investigated through a series of tests performed during both summer and winter under both normal and faulty scenarios. In particular, five distinct typical faults have been artificially implemented in the HVAC system and analyzed during transient and steady-state operation. An optimal artificial neural network-based system model has been created in the MATLAB platform and verified by contrasting the experimental data with the predictions of twenty-two different neural network architectures. The selected artificial neural network architecture has been coupled with a dynamic simulation model developed by using the TRaNsient SYStems (TRNSYS) software platform with the main aims of (i) making available an experimental dataset characterized by labeled normal and faulty data covering a wide range of operating and climatic conditions; (ii) providing an accurate simulation tool able to generate operation data for assisting further research in fault detection and diagnosis of HVAC units; and (iii) evaluating the impact of selected faults on occupant indoor thermo-hygrometric comfort, temporal trends of key operating system parameters, and electric energy consumptions.
... Variable flow, primary-only systems reduced total annual plant energy use by 2-5% [7]. Luigi Schibuola presents a detailed assessment of the impact of the VSDs to HVAC components on public buildings [8]. In HVAC systems a fundamental contribution to energy saving can be obtained by the installation of devices with the capability to fit the motor speed to the actual exigencies of the building demand which for the most part of the year is significantly lower than the design peaks used for sizing the HVAC system application of VSDs to HVAC components in a public building [9]. ...
Chiller plants are the most energy consuming system during summer season in residential, commercial and hospital buildings. The highly variable cooling demand of the buildings connected to a hybrid chiller plant included absorption and vapor compression chillers to achieve higher energy efficiencies is one of the important issues. Cooling load sharing strategies and apply the variable water flow system in chiller plant have a significant impact on energy consumption and consequently with more productivity and environmentally protected. This paper examines the behavior and pattern of energy consumption in a hybrid chiller plant that includes a combination of two air-cooled screw vapor compression and three single effect absorption chillers. In order to properly understand the pattern of energy consumption, an existing mechanical room in a hospital in Tehran has been studied for five months, and its energy consumption has been compared with the optimized model. The results indicate that the sequence of the chiller function and the way in which they are placed in the circuit during a partial load, is in highest importance in view point of energy saving also by Applying of variable water flow system for optimized chiller loading the more energy saving is achieved for hybrid absorption and vapor compression chiller plant.
... For instance, several studies focused on the significant benefits brought about by the application of variable-speed drive technology to various types of ME of air-conditioning systems. For example, studies achieved comparative analyses of the energy performance of variable-speed compressors [4,14], pumps [15][16][17], fans [18,19], chiller plants [20][21][22], and even entire systems [23,24] against the performance of on/off-controlled constant-speed ME. However, what about going in reverse? ...
Motor-driven equipment (ME) is one of the key components in an airconditioning system, which contributes to the vast majority of the total energy consumption by airconditioning systems. Distinguishing variable-and constant-speed equipment is important since the energy simulation models of the two types differ. Traditionally, types of ME are known in advance, and energy consumption data are consequently analyzed. However, in the application scenarios of energy consumption data mining, precedent information on the ME type could be missing. Thus, this study applies this process in reverse, providing new insight into energy consumption data of ME to recognize variable-speed ME in an airconditioning system. The energy consumption data of ME in an airconditioning system implemented in a commercial building were collected and numerically analyzed. A proposed simple parameter, coefficient of the median, and several numerical parameters were calculated and used to distinguish variable-from constant-speed ME. Results showed that the energy consumption data distributions of the two types of ME differed. The proposed coefficient of the median could successfully distinguish variable-from constant-speed ME, and it could be applied as an important step in energy consumption data mining of airconditioning systems.
... Actually, frequency-conversion technique has been previously applied in chiller cooling systems [33e35]. Schibuola et al. [36] investigated the energy-saving effect of introducing frequency-conversion technique into a fan coil system in the public building. Annual monitoring showed 38.9% savings in electricity. ...
A temperature and hydraulic-balance control strategy has previously been proven effective for improving the operational performance and achieving significant energy-savings in air source heat pump (ASHP) heating systems. In this study, a frequency-conversion technique was added to the control strategy for the pump operation, evolving into an updated control strategy. To investigate the performance and evaluate the energy-saving benefits when using the updated strategy, a field experiment was conducted in two almost identical ASHP heating systems in a teaching building, one with the updated strategy (system A) and the other without (system B). Results showed that the updated strategy can ensure an appropriate indoor temperature without overheating. The working number and hours of ASHP compressors in system A were lower than those in system B. Moreover, the savings of heat and electricity of system A were 46.6% and 43.0%, respectively. Electricity-saving of the pump using frequency-conversion technique reached 20.2%, and the effect is more remarkable in the high-frequency range. The percentage of pump's electricity consumption of system A was only 16.4%, which was significantly lower than the previous experiment. Additionally, the COP of ASHP units of system A was 3.23 and was not affected by the introduction of frequency-conversion technique.
Green building technologies (GBTs) play an important role in carbon emission reduction in the building sector. China is currently in the booming phase of green buildings construction and numerous studies have been conducted on green building technologies, especially on the potential of reducing buildings' energy consumption and carbon emissions. This paper provides a comprehensive overview of various GBTs, including high performance envelope, lighting and daylighting, natural ventilation, HVAC (heating, ventilation and air conditioning) system and the utilization of renewable energy. After describing the phases of the building life cycle and the calculation method of building carbon emissions, the literature review focuses on the applications of GBTs in different climate areas in China as well as the main findings and innovations on their carbon reduction potentials. Finally, recommendations for GBTs development are proposed based on the existing researches to facilitate carbon neutrality in the building sector.
A reporting of Energy Audit in 2018 by LEMTEK UI has reported that air fan system currently used in Power Plant of PLTU Tanjung Jati B Jepara is inefficient, energy efficiency in FDF is only 32% and PAF efficiency is 49.01%. Inefficiency of the air fan system is an impacted there are waste of electric energy amount of 13,352,929 KWh (13,35 GWh) a year with a financial loss of IDR 13,352,929,140. To overcome this condition, variable frequency drive (VFD) is installed which adjusted air flow as needed so that energy waste can be reduced. MATLAB simulation is proposed to analyze the VFD method. The result shows that by using VFD, 8,233,573.444 KWh (8.45 GWh) can be saved a year. Total cost benefits are IDR 8,233,573,444 as 32.1% of saving cost. Efficiency of FDF is 72.57 % and PAF is 66.84%.
Different climate characteristics put forward different requirements for the performance of air conditioning system. Climatic division has been proposed to facilitate the selection or design of HVAC systems to match indoor cooling/heating loads of buildings better. However, humidity parameter and distinction of sensible and latent loads are usually ignored, bringing problems to the operation and control of HVAC systems. Therefore, this study proposed a novel climatic division method for China during the cooling period taking the coupling effect of cooling and dehumidification of HVAC systems into account. The humidity-based cooling degree-day was firstly taken as an index to evaluate the influence of outdoor humidity parameter. Then, 96 cities, whose cooling loads are particularly affected by the humidity, were selected for further analysis. Indoor cooling loads were calculated using EnergyPlus and the climatic division based on sensible heat ratio and total cooling load was presented. Finally, on the basis of the novel climatic division, hourly sensible cooling load and latent cooling load of representative cities in each zone were analyzed to get the characteristics of load boundary and frequency distribution. A new design method was therefore proposed and discussed, paving a new way for the customized design of HVAC systems for each climate zone.
Climate change is a serious threat to the environment and socioeconomic globally. Climate change is caused by natural processes and due to human activities that have resulted in long-term climate fluctuations and even globally over the past few decades, the climate has experienced a fairly rapid rise in average temperatures. Climate change is mainly caused due to ozone depletion which results in changes in greenhouse effect conditions. The International Maritime Organization (IMO) has adopted standards to reduce sulfur pollution from ships. The majority of naval warships today use conventional mechanical propulsion systems where the power from the main propulsion is transmitted to the propeller through gearboxes. The ships owned by the Navy almost all still use conventional thrust systems with diesel engine starters. With a conventional support system. The latest innovation in the support system that has been carried out, namely on the United States Navy warship TAKE-1 (the destroyer ship), whereby changing the support system from conventional to electricity with the concept of Integrated Fully Electric Propulsion (IFEP) can reduce fuel use by 10% to 25%. IFEP application if applied to ships of the Navy, will obtain a very large benefit in overcoming environmental problems namely reducing air pollution.
An energy-saving strategy of Variable Refrigerant Volume (VRV) is proposed for air conditioning systems by using the stepless variable speed driving technology. This control technology is applied to the Air Cooled Packaged Water Chiller Unit (ACH) according to the change of environmental heat load to achieve the best amount of refrigerant in real time. This study designs a double feedback Stepless Variable Frequency and Variable Refrigerant Output (DFSVFVRO) for controlling ACH. The double feedback variable frequency control uses both temperature and the pressure sensors as feedback signals to the control board and the frequency of the compressor is regulated by the inverter. Experimental results indicate that the proposed variable frequency control method has a lower energy consumption compared with the conventional normal mode (N). In addition, the proposed double feedback mode (DF) has a lower energy consumption, and thus, it is with better energy efficiency. Furthermore, in the various experiments of proposed DFSVFVRO by comparing the cumulative energy consumption of DF mode with N mode, the DF mode shows an energy saving rate of at least 25%. It also verifies that the double feedback variable frequency control method has a better energy-saving benefits than that of the single feedback frequency.
The operation of indirect evaporative cooler (IEC) largely depends on the ambient temperature and humidity. To maintain stable indoor temperature, proper controller is essential. On-off control is a mature and stable control method used on constant speed fans. However, large fluctuation of indoor temperature can be observed because of limited control precision. To achieve better thermal comfort, a proportional–integral (PI) law based variable speed technology is proposed for accurate temperature control in an IEC system. This technology had been proved highly effective in central air-conditioning systems and direct expansion air-conditioners in terms of control precision and energy saving, but its techno-economic feasibility in IEC has not been investigated. In this study, annual dynamic simulation has been conducted to an IEC system based on the IEC model and control algorithm. Results show that indoor temperature can be controlled within ±0.5 °C around the setting point for 81.9% of time, while it is only 30.5% under on-off control. The PI based controller is well adapted to cooling loads in all seasons with good control precision, fast response speed and small overshoots. Response time of PI control is only 10 min in a disturbance rejection test, which is much shorter than 30 min under the on-off control. Annually, IEC with variable speed fans consume 50.0% less energy than that of on-off fans. At last, economic analysis shows that this technology is economically feasible only when the power of primary air fan is larger than 1.75 kW.
This study proposed a real-time fault diagnostic model for air-handling units (AHUs); the model used deep learning to improve the operational efficiency of AHUs and thereby reduce the energy consumption of HVAC—heating, ventilating, and air conditioning—systems in buildings. Additionally, EnergyPlus simulation software was employed to establish different types of fault operation behavior data to serve as references for deep learning, thus reducing the complexity of data preprocessing, retaining data completeness, and improving the reliability of the diagnostic model.
The proposed deep neural network fault diagnostic model can serve as a reference for this research field; the model features five hidden layers, each comprising 200 neurons. Additionally, this study tested abnormal faults commonly observed in AHUs, including failure to control two-way hydronic valves and variable air volume box dampers as well as supply air temperature sensors exhibiting measurement error. After performing diagnosis with data that had not been used in the training or verification process, the diagnostic results indicated that the diagnostic model exhibited 95.16% accuracy.
This paper is the first global analysis of the potential energy savings which could be found in electric motor- driven system (EMDS). EMDS currently accounts for more than 40% of global electricity consumption. Huge untapped energy efficiency potential was found in EMDS; around 25 % of EMDS electricity use could be saved cost-effectively, which would reduce total global electricity demand by about 10%. To date, energy efficiency opportunities with EMDS have been relatively neglected in comparison with other sustainable energy opportunities. It is crucial to scale up operations and resources committed to realizing the vast potential energy savings and this paper proposes a comprehensive package of policy recommendations to help governments achieve these significant energy savings in EMDS.
CO2 based ventilation control is an eligible technology to reduce energy consumptions concerning ventilation air treatment and its distribution in particular in presence of highly variable occupancy. An experimental assessment of the performances of this control strategy is illustrated in this paper. The study refers to a historic building in Venice recently refurbished and subject to a preservation order. It concerns a demand controlled ventilation (DCV) system installed in a part of the building transformed in a university library and based on the use of CO2 sensors. A building management system (BMS) able to measure and record the required data was used as a tool for long term monitoring of the HVAC system. A comparison with alternative solutions was also carried on. The results permit to quantify remarkable energy savings, particularly strategic in the energy retrofit of historic buildings especially in presence of preservation orders. But the investigation highlights also the peculiarities of CO2 based ventilation control in meeting the indoor comfort requirement which suggest a systematic use of long term assessment to verify control efficacy in different operating conditions.
Motors systems are a major electricity consumer (about 70% of the industrial electricity consumption and about 35% in the non-residential buildings sector). Several studies showed the very large energy saving potential deriving from motor improved efficiency.
After a period of Voluntary Agreement with a somehow limited impact, the EU introduced in 2009 Minimum Efficiency Performance Standards (MEPS) with the Commission Regulation 640/2009, which specifies requirements regarding Ecodesign of electrical motors and the use of electronic speed drives (VSD). The Regulation is based on the findings of the first Energy using Products (EuP) study on motors (Lot 11), which highlighted the importance of introducing Minimum Efficiency Performance Standards (MEPS) relating to these products in the EU.
A new Ecodesign preparatory study (European Commission - Lot 30 on special motors and drives) has since then been carried out to evaluate the possibility of extending the scope of the Regulation to motors outside the current power range and to technologies other than three-phase induction motors.
Six policy options (PO) were identified, as well as their possible implementation timelines, that will lead to the reduction of environmental impacts taking into consideration the Life Cycle Cost and the best available technologies in the market.
This paper shows the results of a monitoring campaign on an invertible ground source heat pump (GSHP) with borehole heat exchangers installed in the historical center of Venice in the frame of the renovation of an ancient building where other renewable energy systems, such as solar energy systems, are not admitted because of historical preservation regulations. Despite the coastal position, the use of surface or ground water was not achievable in this case. In fact, the withdrawal from wells is absolutely forbidden in Venice, due to the risk of subsidence of the soil. In addition, as often happens in Venice, the internal channels next to the building have insufficient water flow rate. The experimental analysis highlights very satisfactory performance especially in comparison with the alternative use of air source heat pumps. The high humidity of the soil and the underground water flow present even in the surface layers of the soil promote the quick thermal rebalancing in the borehole field. For the same reason, although there is un-balance between the heat rejected in summer and the one extracted during winter, no consequent thermal degradation of the ground heat exchange is encountered.
Electric motors are repaired 2-3 times over their lifetime. Poor repair practices, particularly widespread in developing countries, can lead to a significant increase in motor losses. It is estimated that worldwide poor repair leads to annual electricity losses of approximately 40 TWh, representing 20 Mtons of CO<sub align="right"> 2 </sub> emissions. The main objective of this paper is to provide a technical basis for designing demand side management actions, which address the motor repair market. This paper brings into focus motor repair process trends, energy-efficient motors, typical repair process, actions to promote energy-efficient motor repair, energy-efficient motor rebate schemes to replace old, badly damaged motors and the factors influencing payback. This paper will be useful to energy policy makers, and Demand Side Management (DSM) staff in energy agencies and electric utilities.
Most motors are designed to operate at a constant speed and provide a constant output; however, mod-ern technology requires different speeds in many applications where electric motors are used. A variable speed drive (VSD) is a device that regulates the speed and rotational force, or output torque of mechan-ical equipment. Effects of applying VSDs are in both productivity improvements and energy savings in pumps, fans, compressors and other equipment. Variable speed drive technology and the importance of controlling the speed of existing motors have fascinated many attentions in the last years with the advent of new power devices and magnetic materials. This paper is a comprehensive review on applica-tions of VSD in electrical motors energy savings. The aim is to identify energy saving opportunities and incorporated costs of applying variable speed drives to the existing applications of electrical motors. Sub-sequently, economic analysis, payback period and the effect of current and voltage harmonics generated by VSDs are presented. Authors are hopeful to provide useful information for future variable speed drive applications like fans, pumps, chillers, ventilators and heaters. Nomenclature VSD variable speed drive DC direct current AC alternating current GHG greenhouse gas ASD adjustable speed drive Hp horsepower PWM pulse width modulation IGBT insulated gate bipolar transistor HVAC heating, ventilating, and air conditioning MOV motor operating value EMS energy management control system
Operation and application of variable frequency drive (VFD) technology
- Carrier
Carrier. "Operation and application of variable frequency drive (VFD) technology" New York, Carrier Corporation Syracuse (2005) available
on line.
Guide to variable speed drives
ABB, "Guide to variable speed drives", technical guide n°4 (2011)
2016 ASHRAE handbook -HVAC Systems and Equipment
- Ashrae
ASHRAE. "2016 ASHRAE handbook -HVAC Systems and Equipment" (2016)