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![Seasonal Performance Factor (SPF) values during cooling season (summer), heating season (winter) and the whole year according to the SEPEMO project definition [38].](publication/320092669/figure/fig14/AS:543738184966145@1506648693896/Seasonal-Performance-Factor-SPF-values-during-cooling-season-summer-heating-season.png)
Seasonal Performance Factor (SPF) values during cooling season (summer), heating season (winter) and the whole year according to the SEPEMO project definition [38].
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Ground source heat pump (GSHP) systems stand for an efficient technology for renewable heating and cooling in buildings. To optimize not only the design but also the operation of the system, a complete dynamic model becomes a highly useful tool, since it allows testing any design modifications and different optimization strategies without actually...
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Ground-source heat pumps are an efficient technology for heating and cooling in buildings. However, the main limitation of their widespread application is the borehole heat exchanger’s (BHE) high investment cost. Hybridizing GSHP systems may overcome this limitation. This research work analyzes the long-term energy performance of a dual-source heat...
Citations
... The building and its corresponding thermal demand analyzed in the study were previously modeled by Ruiz-Calvo et al. [34]. The building belongs to the Department of Applied Thermodynamics situated on the campus of the Polytechnic University of Valencia, Spain. ...
... Building analyzed in the study: (a) TRNSYS building model and (b) fan coils' distribution in the building[34]. ...
Ground-source heat pumps are an efficient technology for heating and cooling in buildings. However, the main limitation of their widespread application is the borehole heat exchanger’s (BHE) high investment cost. Hybridizing GSHP systems may overcome this limitation. This research work analyzes the long-term energy performance of a dual-source heat pump (DSHP) system, which uses the air or the ground as external heat/sink sources, in three representative European climates. First, a BHE cost-effective design solution is proposed for each climatology; then, a complete energy analysis is carried out, and the optimal source control parameters that best enhance the system performance in each climate are determined with the use of a complete dynamic model of the DSHP system developed in TRNSYS. Simulations were carried out for a 25-year operation period. Results show that the DSHP maintains the efficiency during the simulated period, with deviations lower than 1.7% in all cases. Finally, the source control optimization method results in only slight efficiency gains (<0.35%) but with a stronger effect on the ground/air use ratio (up to 25% use of air in cold climates), reducing the thermal imbalance of the ground and leading to a consequent BHE size length and cost reduction.
... The study calculated the COP of the system and evaluated technical and economic factors. Ruiz-Calvo et al. [19] optimized the design and operation of the GSHP using TRNSYS software for the heating and cooling of buildings. The model was validated against experimental data; it accurately predicted the system behavior. ...
The purpose of this study was to conduct a modeling-based energy performance assessment and validation of an air-to-water heat pump (AWHP) system, in the cooling mode, integrated with a multi-span greenhouse using TRNSYS software. We used the building energy simulation (BES) model to investigate the performance characteristics of the AWHP system for greenhouse cooling. We modeled the components of the AWHP system, including the fan coil unit (FCU), water storage tank, and water circulation pump integrated with the greenhouse model. The proposed model included all the components of the experimental system. We validated the proposed model by comparing the simulation results with those obtained from field experiments. We investigated the cooling energy supply to the multi-span greenhouse, greenhouse internal air temperature, heat pump (HP) output temperature, and coefficient of performance (COP). We evaluated the performance of our model by calculating the Nash-Sutcliffe efficiency (NSE) coefficient of all the validated components. Furthermore, we performed linear regression analyses (R 2) to determine the relationship between the different parameters. NSE values of 0.87, 0.81, and 0.93, for the greenhouse internal air temperature, the energy supply to the greenhouse, and the HP output water temperature, respectively , validated the prediction accuracy of the model. Moreover, R 2 values of 0.83 and 0.39 indicated that cooling loads are more dependent on ambient solar radiation than ambient air temperature. Furthermore, an R 2 value of 0.91 showed a linear relationship between the HP's energy consumption and ambient air temperature. The average daily COP of the HP system was 2.9. Overall , the simulation results showed acceptable correlation with the experimental results. The high NSE values validated the high predictive power of the model. The proposed validation model can be used to improve the performance of systems by optimizing the control strategies and capacities of the equipment (e.g., the HP, the FCU, and the area of the greenhouse). We have provided detailed information to enable engineers, researchers, and consultants to implement the model for their specific needs.
... In addition, Ruiz-Calvo et al. [7] developed TRNSYS models to represent a Mediterranean building equipped with a water/water HP and for which they also compared HP models to field measurements. Furthermore, Conti et al. [8] compared the energy performance of an air/water HP in a HIL experiment to simulations based on manufacturer datasheets. ...
Heat pumps play a paramount role in carbon emission reductions as they allow the use of sustainable energy. As heat pumps mainly use electricity to provide thermal services, they also enable the provision of energy flexibility services. In this context, new heat pump control strategies are investigated. Though, the comparison of smart and traditional control strategies requires an accurate knowledge of the real heat pump behaviour, both in short-and long-term. Firstly, this paper presents a hardware-in-the-loop setup which allows a real heat pump behaviour analysis, while the required communication is also shown. Secondly, the test bench was used to validate and further develop a water/water heat pump model. Hence, artificial test cycles were used to distinct and validate the internal control strategies of the heat pump, with the focus on both the short-term behaviour and energy consumption. As the heat pump model started from the manufacturer documentation, comparing the experimental results to the simulations revealed deviated behaviour due to a different modelling approach of the heat pump internal control strategies. Hence, the heat pump model was improved by changing and adding control strategies such as a compressor modulation controller, timing constraints and condenser and evaporator pump control. Although the improved heat pump model reached better profile agreement, deviations remained and indicated a calibration work necessity. Analysis also showed that the real heat pump was not able to quickly recover for the combination of high space heating temperatures and low thermal loads, while increasing the supply temperature for energy flexibility services is common. To conclude, results proved that only using heat pump manufacturer documentation is not sufficient for real heat pump behaviour representation.
... In general, GCHP systems utilising the vertical BHEs have higher coefficients of performance (COP) and require less ground area due to lower seasonal variations in mean temperature of the ground [5]. The performance of GCHP systems has been widely investigated by both simulation tools and experiments [6][7][8]. ...
The present study aims to investigate comprehensively the performance of various nanofluids in single U-tube borehole heat exchangers (BHEs). Seven common nanoparticles with the volume fraction ranging from 0.1% to 2.0% are selected to be evaluated as the heat carrier fluid. Firstly, a comparative techno-economic analysis is performed in order to highlight the merits and drawbacks of each nanofluid. Then, a sensitivity analysis is performed to optimise the decrement percentage of BHE thermal resistance. Finally, by means of the linear regression of numerical results obtained for different nanofluids, simple equations are proposed allowing evaluation of the outlet fluid temperature for nanofluids. The obtained results indicate that Ag- and Cu-based nanofluids are characterised by the highest heat transfer enhancement, although this improvement is at penalty of a higher pressure drop and up to 31% higher required pumping power. On the other hand, SiO2- and TiO2-water nanofluids are the worst cases in terms of thermal performance, but at the same time, they are characterised by the lowest pressure drop. The optimum decrement percentage of thermal resistance yielded in presence of Cu-water nanofluid is equal to 4.31%. Furtheremore, it is shown that employing nanofluids for the purpose of BHE length reduction is not a promising choice. Economic analysis revealed that the cost of electrical energy for nanofluids due to the higher energy consumption of pump is negligible in comparison with the capital cost of nanoparticles. The SiO2 nanoparticles with a capital cost ranging from 5.8 to 17.5 €/m is the cheapest nanoparticle to employ, unlike the Ag nanoparticles
... On the other hand, a vertical GSHP is expensive to install but has the advantage that its geofluid shows almost a constant temperature throughout the year because the earth's temperature remains constant at depths below 12 m (Monzó et al., 2015;Priarone and Fossa, 2016). To date, very few GSHP systems are constructed and analyzed experimentally, and are usually studied numerically and analytically in order to avoid the high costs of installation, especially those related with drilling (Belzile et al., 2016;Katsura et al., 2020;Spitler and Gehlin, 2019;Li et al., 2019;Rivoire et al., 2018;Naldi and Zanchini, 2018;Ruiz-Calvo et al., 2017;Jung et al., 2016;Jahanbin et al., 2020;Eslami-nejad and Bernier, 2012;Lee and Lam, 2012). ...
Ground-source heat pumps are widely used around the world because of their capacity to provide renewable and emissions-free energy for residential use. A vertical ground-source heat pump in an air conditioner mode is studied experimentally and numerically. The geothermal heat pump is located in Mexico, and consists of a single U-tube of 100 m depth, with 41.16 m³ of conditioned space. A computational fluid dynamics analysis of the geothermal heat exchanger and a thermoeconomic analysis of the heat pump are developed to evaluate the thermal performance of the system under the weather conditions of Mexico, and to know the cost allocation per equipment of the system. Results show that the geothermal heat pump provides a comfort temperature with the minimum value of a comfort relative humidity; the most important temperature changes for the geothermal heat exchanger are present during the first 10 m depth; the system decreases its performance when operating in cities with hot ambient temperatures; the irreversibilities present in the system are small, and the cost of the components depends mainly on the capital investment. In addition, the coefficient of performance of the system is of 3.3–3.6.
... They showed that increasing the imbalance of the load by reducing the heat load would reduce the long-term efficiency of the system. Ruiz-Calvo et al. [135] presented a GSHP model in TRNSYS with a BHE model that considers both short-term and long-term models for BHE [42]. However, these models were not used for optimizing the operation of GSHP. ...
This work is protected by the Swedish Copyright Legislation (Act 1960:729) Dissertation for PhD ISBN: 978-91-7855-648-9(print) ISBN: 978-91-7855-649-6 (pdf) Electronic version available at: http://umu.diva-portal.org/ Printed by: Cityprint i Norr AB Umeå, Sweden 2021
... In this case, the experimental data of a prototype were interpolated to obtain the heating/cooling capacity and COP/EER maps, as a function of outdoor air temperature for airsource operation, of the inlet brine temperature for the ground-source mode, the load side inlet water temperature and the inverter frequency for both modes. Ruiz-Calvo et al. [17] developed a TRNSYS model of a GSHP using the performance matrix obtained as explained in Corberan et al. [18]. The maps were obtained using a quasi-state mathematical model developed using IMST-ART [19] and integrated into EES, and were validated against experimental data. ...
TRNSYS Software is a flexible tool for dynamic simulation of plants, interconnecting the different components of the system represented as black boxes and called “Types”. This paper presents a novel Type for the simulation of a reversible water-to-water heat pump that is freely released. Differently from the previous models available in this environment, the Type is based on the polynomials of the compressors and contains an internal link to REFPROP to easily evaluate the thermodynamic properties of refrigerant fluids. In the present work, the Type was employed for investigating a ground source heat pump providing space heating and cooling to a historic building, where, for architectural limitations, the existing high-temperature terminal units cannot be replaced. Its operation, using different refrigerants, was evaluated under three climates, simulating two heat pump configurations coupled with radiators or fan coils. In the first case, a cascade-cycle configuration was considered to supply high-temperature heat, whereas, with fan coils, a standard single-stage cycle was studied. The results for the cascade-cycle configuration showed a seasonal coefficient of performance ranging from 2.48 for the coldest location (Helsinki) to 2.86 for the warmest one (Athens). These values increased to 3.29 and 4.90, respectively, when considering fan coil terminal units instead of radiators. On the other hand, the seasonal efficiency values were equal to 7.95 in Helsinki and 5.56 in Athens. Moreover, the low incidence of the thermal drift effect on the long-term performance of the cascade ground source heat pump was highlighted, showing for the coldest location a penalisation of 2.5%, compared to 7.3% of the single-stage cycle.
... However, to be able to correctly reproduce both the short-term and long-term behavior of the GSHP system, a detailed model is needed including all its main components. Such a model is proposed and validated in [149,150] basing on TRNSYS dynamic simulation software. Inequality constraints have to be considered related to the to the minimization of the so-called "thermal drift" [151]. ...
Buildings are responsible for over 30% of global final energy consumption and nearly 40% of total CO2 emissions. Thus, rapid penetration of renewable energy technologies (RETs) in this sector is required. Integration of renewable energy sources (RESs) into residential buildings should not only guarantee an overall neutral energy balance over long term horizon (nZEB concept), but also provide a higher flexibility, a real-time monitoring and a real time interaction with end-users (smart-building concept). Thus, increasing interest is being given to the concepts of Hybrid Renewable Energy Systems (HRES) and Multi-Energy Buildings, in which several renewable and nonrenewable energy systems, the energy networks and the energy demand optimally interact with each other at various levels, exploring all possible interactions between systems and vectors (electricity, heat, cooling, fuels, transport) without them being treated separately. In this context, the present paper gives an overview of functional integration of HRES in Multi-Energy Buildings evidencing the numerous problems and potentialities related to the application of HRESs in the residential building sector. Building-integrated HRESs with at least two RESs (i.e., wind–solar, solar–geothermal and solar–biomass) are considered. The most applied HRES solutions in the residential sector are presented, and integration of HRES with thermal and electrical loads in residential buildings connected to external multiple energy grids is investigated. Attention is focused on the potentialities that functional integration can offer in terms of flexibility services to the energy grids. New holistic approaches to the management problems and more complex architectures for the optimal control are described.
... Among hybrid systems, the dual source heat pump is surely interesting. In this case, the heat pump can use the most favorable source or sink between air or ground [28,29]. ...
Ground coupled heat pumps are a notoriously efficient system for heating and cooling buildings. Sometimes the characteristics of the building and the user’s needs are such that the amount of heat extracted from the ground during the winter season can be considerably different from the amount injected in summer. This situation can cause a progressive cooling or heating of the ground with a negative effect on the energy efficiency and correct operation of the system. In these cases, an accurate sizing has to be done. In systems already built, it could be necessary to intervene a posteriori to remedy an excessive ground thermal drift due to the energy unbalance. In this work, such a situation relating to a real office building in Italy is investigated and several solutions are examined, one of which has been then implemented. In particular, a hybrid heat pump using as heat sink both the ground and external air is compared with common solutions through computer simulations using a dedicated numerical model, which has also been compared with monitoring data. As a result, the hybrid heat pump shows better performance and limits the thermal drift of the ground temperature.
... The most common BHEs have a diameter of about 15 cm, with lengths ranging between 40 and 200 m. The performance of GCHP systems has been exhaustively investigated by both simulation tools and experiments [5][6][7][8][9][10]. ...
... The figure shows a fair agreement between numerical results and those obtained through correlations. The mean square deviation (MSD) of the results obtained numerically from those obtained through the correlations can be determined by: (6) where ϕ is an arbitrary parameter. The MSD of the mean fluid temperature, Tf,m, obtained by numerical simulation from Tf,m obtained through the correlations is 0.29 °C, equal to a normalized MSD of 1.05%. ...
Given that the issue of variations in geometrical parameters of the borehole heat exchanger (BHE) revolves around the phenomenon of thermal resistance, a thorough understanding of these parameters is beneficial in enhancing thermal performance of BHEs. The present study seeks to identify relative changes in the thermal performance of double U-tube BHEs triggered by alterations in circuit arrangements, as well as the shank spacing and the borehole length. The thermal performance of double U-tube BHEs with different configurations is comprehensively analyzed through a 3D transient numerical code developed by means of the finite element method. The sensitivity of each circuit configuration in terms of the thermal performance to variations of the borehole length and shank spacing is investigated. The impact of the thermal interference between flowing legs, namely thermal short-circuiting, on parameters affecting the borehole thermal resistance is addressed. Furthermore, the energy exchange characteristics for different circuit configurations are quantified by introducing the thermal effectiveness coefficient. The results indicate that the borehole length is more influential than shank spacing in increasing the discrepancy between thermal performances of different circuit configurations. It is shown that deviation of the averaged-over-the-depth mean fluid temperature from the arithmetic mean of the inlet and outlet temperatures is more critical for lower shank spacings and higher borehole lengths.
