Heat Pump Coefficient Of Performance Research Articles

Seasonal COP of a residential magnetocaloric heat pump based on MnFePSi

The performance of a magnetocaloric heat pump (MCHP) consisting of active magnetocaloric regenerators (AMR) of 12 layers of MnFePSi magnetocaloric materials (MCM) with a linear distribution of Curie temperatures was investigated using a 1D numerical model. The model predicted the heating power and coefficient of performance (COP) of the AMR for a fixed temperature span of 27K, between 281K and 308K, and variable flow rate and AMR cycle frequency. A maximum applied magnetic field strength of 1.4T was used. A well-insulated house with a maximum heating power demand of 3kW (under quasi steady state conditions) was considered. Ambient temperature in The Netherlands was taken as a reference for the estimation of the seasonal heating power demand. Without optimizing the design of the AMR, the model predicts a maximum single-AMR heating power equal to 43.5W when the AMR operates at 3Hz and 3Lmin-1, and a maximum COP equal to 5.8 when it operates at 1.5Hz and 1Lmin-1 Considering the maximum heating power of a single AMR, approximately 69 AMRs are needed to provide the design heating power demand of the house. It was found that it is possible to achieve an AMR seasonal COP of 5.6 by continuously adjusting the flow rate and frequency of operation of the MCHP along with the ON/OFF switching of some groups of AMRs in order to adjust the heating power of the MCHP to the heating power demand of the house.

Centrifugal compressor design and cycle analysis of large-scale high temperature heat pumps using hydrocarbons

Using natural refrigerants in heat pumps, including hydrocarbons, is becoming attractive because of the tightening regulations concerning synthetic refrigerants. In the literature there is lack of studies investigating detailed component design, including compressor design when using hydrocarbons. This study investigates numerically centrifugal compressor design with hydrocarbons for large-scale high-temperature heat pumps. The compressor analysis was combined with a thermodynamic analysis of a two-stage heat pump. The effect of temperature lift and flash intercooler temperature on compressor sizing, rotational speed, efficiency, axial force, and Mach number were investigated. Generally, the use of hydrocarbons with five carbon atoms resulted in higher coefficient of performance and required lower compressor rotational speeds and larger compressor dimensions when compared to the hydrocarbons with four carbon atoms. The simulated rotational speeds were ranging from 8 krpm to 30 krpm, impeller diameters from 0.15 m to over 0.7 m and compressor efficiencies from 77% to over 85%. The use of cyclic molecules, namely cyclopentane and cyclobutene resulted in the highest heat pump coefficient of performance. Also, the flash intercooler temperature had a notable effect on the compressor design and axial force which has to be taken into account in heat pump cycle design.

Performance evaluation of transcritical CO2 desiccant heat pumps for electric vehicles

Transcritical CO2 heat pump systems are eco-friendly and have excellent heating performance, which makes them suitable for electric vehicles. The recirculation mode can save energy but requires a dehumidification function to ensure driving safety. Therefore, this paper proposes a transcritical CO2 desiccant heat pump, which differs from the typical transcritical CO2 heat pump system by incorporating an indoor evaporator and a full-pass throttle valve. The flow area of the full-pass throttle valve can be adjusted to obtain the appropriate dehumidification rate. In addition, this study suggested using the desiccant heat pump coefficient of performance (DHCOP) to evaluate the overall energy efficiency of the heat pump system. We have investigated the dehumidification rate and optimal discharge pressure under different operating conditions. The results show that even under the harsh operating conditions at -10 °C, the HDCOP of the transcritical CO2 desiccant heat pump can still exceed 2.1, and reach 3.12 at a moderate condition of Ta=5 °C. The transcritical CO2 heat pump desiccant system demonstrates significant energy-saving potential.

Reducing the specific energy use of seawater desalination with thermally enhanced reverse osmosis

This study investigates the concept of using heat to enhance reverse osmosis (RO) desalination. An analytical model is used to evaluate the effect of temperature on water permeate flux, specific energy, permeate quality, and applied operating pressures. When feed is heated from 20 to 50 °C, specific energy savings of up to 24 % are observed for high flux seawater desalination and up to 33 % for brackish water. Such improvements are consistent with the literature, but until now the thermal energy input required to heat feed has been mostly neglected from analysis. For the first time, the overall energy balance of thermally-enhanced RO is considered to evaluate the tradeoff between savings in mechanical pump work and thermal energy input. Results suggest that this tradeoff is favorable under the right conditions. In particular, there is a need for high thermal efficiencies including both a very high heat pump coefficient of performance and very high heat exchanger efficiency for recycling thermal energy. Under these conditions, overall energy savings of up to 12 % are observed for seawater desalination when feed is heated from 20 to 41 °C, and up to 18 % for brackish water with feed heated to 46 °C.

Technical Performance Comparison of Horizontal and Vertical Ground-Source Heat Pump Systems

The configurations of ground heat exchangers (GHEs) play a significant role in the efficiency and sustainability of ground-source heat pump (GSHP) systems. However, there is a knowledge gap in understanding the performance differences between the horizontal and vertical GSHP systems in the same project under various heating and cooling demands. In this study, a technical performance comparison between GSHP systems coupled with horizontal ground loops and vertical boreholes under three scenarios of heating-to-cooling ratios (6 : 1, 2.4 : 1, and 1 : 1) was conducted. The simulations were based on a coupled thermal–hydraulic model for unsaturated soils that takes into account realistic ground surface boundary, GHE boundary, and the dynamics of heat pump efficiency. The GHEs were designed based on an experimental site located on the campus of a UK university. Results showed significant differences in the development of fluid temperatures and coefficient of performance (COP) of heat pumps between the horizontal and vertical GSHP systems due to the differences in the soil profiles and temperature boundaries. Both the fluid temperatures and heat pump COPs in the horizontal GSHP system reached a steady annual cycle after 2 years regardless of the heating-to-cooling ratios. For the vertical system, a general downward trend in the fluid temperatures and the COP of the heat pump in the heating mode can be found when a heating-to-cooling ratio was 6 : 1 or 2.4 : 1, while an overall upward trend in the fluid temperatures and the COP of the heat pump in the heating mode can be noted in the case of 1 : 1 heating-to-cooling ratio. Additionally, the heat pump operating in the cooling mode was off most of the time when a heating-to-cooling ratio was 6 : 1 or 2.4 : 1, while a declining trend in the COP of the heat pump in the cooling mode was exhibited in the case of a heating-to-cooling ratio of 1 : 1. The technical comparison reveals that the heating-to-cooling ratios would significantly affect the efficiency and sustainability of both GSHP systems.

Dehumidification load ratio: influence mechanism on air conditioning and energy saving potential analysis for building cooling

The construction energy consumption (EC) makes up around 35% of the total energy used. Half of this energy is used for air-conditioning to cool spaces. The effectiveness of cooling relates to various factors, particularly the dynamic thermal performance of air-conditioners (AC) in different conditions. Studying heat pumps in diverse hot and humid climates, especially where dehumidification matters in summer AC, reveals efficiency. Examining the connection between coefficient of performance (COP) and heat removal aids in lowering building energy usage and improving cooling systems. To achieve this, a validated thermodynamic model of heat pumps and a specific transient building heat transfer model were combined. The study focused on three distinct hot and humid climate zones: Guangzhou, Wuhan, and Jiuquan. Simulations of heat pump performance were conducted throughout the year to analyze variations in COP, relative humidity (RH), and latent heat load (LHL).Key findings indicate that the COP of heat pumps is notably influenced by the practical amount of dehumidification required. A positive correlation (correlation coefficient: 0.52151) exists between COP and LHL, emphasizing the importance of addressing dehumidification needs. The research highlights that the COP remains consistently high when the heat pump manages between 45% to 80% of the LHL. Practically, these findings have crucial implications for heat pump applications and building EC reduction, particularly in regions with pronounced dehumidification requirements during the cooling season. By understanding the interplay between heat pump efficiency, humidity, and heat load, practitioners can optimize heat pump performance to achieve energy savings. This research provides a valuable reference for designing and implementing cooling systems in various hot and humid climates, facilitating energy-efficient practices and environmentally friendly building operations.

Technical and economic analysis of multi-energy complementary systems for net-zero energy consumption combining wind, solar, hydrogen, geothermal, and storage energy

An integrated renewable energy supply system is designed and proposed to effectively address high building energy consumption in Zhengzhou, China. This system effectively provides cold, heat, and electricity by incorporating various clean energy sources such as wind, solar, hydrogen, and geothermal energy. Technical and economic analyses are conducted to optimize the integration of these renewable sources. Technical and economic analyses are conducted to optimize the integration of these renewable sources. Rigorous system modeling and dynamic simulation using TRNSYS software evaluate the seamless integration and optimal functioning of the PV/T subsystem within the CCHP system. The interaction between Photovoltaic/Thermal (PV/T) and borehole heat exchanger (BHE) coupling is investigated, analyzing their impact on individual system performance. Furthermore, key indicators, including overall electricity consumption (OEC), life cycle cost (LCC), heat pump coefficient of performance (COPHP), and system coefficient of performance (COPSYS) are analyzed. The robust response surface methodology (RSM) and Box-Behnken experimental design approach are employed to show remarkable agreement between predicted and simulated values, with a maximum deviation of only 1.45%. The optimal configuration consists of a PV/T area of 132 m2, 20 wind turbines, 12 alkaline fuel cells, and 17 borehole heat exchangers, resulting in highly favorable outcomes: an OEC of −35648.72 kW∙h/year, an LCC of $209113.85, a COPSYS of 2.91, and a COPHP of 3.82. Moreover, detailed assessments of each subsystem's performance enhances our understanding of the system's overall operation, affirming the feasibility of the proposed integrated energy supply system for buildings.

A numerical study on performance efficiency of a low-temperature horizontal ground-source heat pump system

Exploitation of shallow ground and its low-grade heat potential is fundamental to designing 5th generation district heating and cooling (DHC) networks. Horizontal ground-source heat pump (HGSHP) systems are a common way to utilize shallow geothermal energy. Realistic estimation and prediction of performance of a HGSHP system and shallow ground thermal behaviour should consider the whole system including building heating and cooling load, heat pump and ground heat exchanger, and the ground. This should be accompanied by realistic atmospheric and ground conditions. In this paper, a three-dimensional coupled thermal–hydraulic model with realistic boundary conditions adopting a whole system approach is presented. Dynamic heat pump coefficient of performance (COP) that depends on seasonal variation of heating/cooling demand and ground conditions are also considered. Model validations are conducted against experimental and analytical results in literatures. The model is applied for evaluating a HGSHP system to support development of a 5th generation DHC network on a potential site in the UK. Several influencing factors, such as ground moisture transfer, building thermal load mode, buried depth of ground loops, and initial ground temperature profile are studied to assess performance efficiency of the HGSHP system and evolution of ground thermal behaviour in response to heat extraction or rejection into the ground. The results show that 5% of the monthly total heat demand of the site could be met by the designed HGSHP system, consisting of 200 U-shaped ground loops buried at the depth of 3 m and pure water as the heat carrier. Overlooking the ground moisture transfer or hyperbolizing the ground saturation would overestimate the load-carrying capacity of the HGSHP system. The HGSHP system is more efficient with a higher heat pump COP under the heating and cooling mode than under the heating-only mode. Predicted performance of the HGSHP system improves with buried depth of the ground loops. The results also show that a 1 ℃ increase in the undisturbed ground temperature could suffice up to 8% of the monthly total heat demand of the site.

Reducing industrial hydrogen demand through preheating with very high temperature heat pumps

Decarbonising industry while maintaining economic competitiveness and improving living standards is one of the main challenges of reaching net zero targets, and low-carbon process heating will play a key role in this. In this work we investigate the potential to reduce the energy demands of hydrogen-based industrial heating systems using very high temperature reverse Joule-Brayton cycle heat pumps as preheaters, considering their economics and technical challenges. A thermodynamic process model is used to assess performance at temperatures of 300–500 °C, and cost optimisation is used to conduct cost-benefit analysis of preheating green hydrogen using heat pumps. It is found that over this temperature range, heat pump coefficient of performance lies in the range 1.4–1.7, with the turbine meeting 30–40% of the compressor load. At the electricity prices currently paid by heavy industry in Western Europe, levelised cost of heat from these heat pumps would be less than 4.5p/kWh. Using 500 °C heat pumps as preheaters in hydrogen heating systems could reduce hydrogen demands by over 20% and provide savings on the cost of green hydrogen of at least 8% out to 2050. With process heat accounting for three-quarters of industrial energy use and half of this being at temperatures above 400 °C, these savings are significant and suggest that very high temperature heat pumps could make an important contribution to industrial decarbonisation.

Performance Analysis of Solar Assisted Ground Source Heat Pump to Supply Heating Load and Domestic Hot Water

Algeria’s geographical location offers several advantages related to the extensive use of renewable energy sources such as solar and geothermal. Owing to the vast Algerian territory, the need for isolated areas to be supplied with energy by autonomous systems using sustainable energy. In this study, we propose a hybrid renewable energy system to provide heating systems for residential buildings and domestic hot water (DHW). Four different solar-assisted ground source heat pump (SAGSHP) combinations are being studied, with the aim of satisfying the energy needs of a building located in Batna, Algeria. The TRNSYS software allowed us to study the different effects of the parameters on their performance. It turned out that a 7.7 kW ground source heat pump system combined with flat solar collectors is a feasible choice that satisfies our objective. The extreme annual average values of the heat pump coefficient of performance (COP) obtained are 3.48 and 4.55. In the system, with recharging the borehole, the net energy extracted from the ground is decreased by 30.4% compared to the reference case (GSHP). This can reduce the ground thermal imbalance problem, which positively affects the stability of the operational system.

INFLUENCE OF PRESSURE IN THE TURBINE CONDENSER ON HEAT SUPPLY EFFICIENCY OF NPP WITH HEAT PUMP

The use of a heat pump for heat supply makes it possible to practically stop thermal pollution of the environment during the operation of thermal and nuclear power plants in winter. If a steam turbine condenser is used as a low-potential energy source for heat pump, the amount of released thermal energy will be equal to the sum of the thermal power of the NPP condenser and the power of the heat pump compressors. From the point of view of environmental safety, heat supply by combining power plant with a heat pump is an urgent task. But it is known that the due to the lack of steam extraction for water heating, the additional electrical power of the cogeneration heat and power plant will be less than the capacity of the heat pump compressors. Thus, in terms of thermodynamic efficiency, the use of a heat pump loses to a traditional cogeneration plant. The purpose of the work is to determine the influence of the final pressure in the turbine condenser on the thermodynamic efficiency of a nuclear power plant with a heat pump. A mathematical model of the thermal scheme of the K-1000-5.8/1500 NPP turbo-plant during summer and winter operation with heating plant has been developed. With the heating plant capacity of 230 MW, the electric capacity of NPP unit decreases by 43.5 MW. A mathematical model of a heat pump has been developed, for which a steam turbinecondenser is used as a low-potential energy source. To ensure the release of 230 MW of heat, the power of the heat pump compressor must be 48.4 MW. Thus, if the heating plant is replaced with a heat pump of the same capacity, the electric power will decrease by 4.8 MW. Calculations were made regarding the influence of the final pressure in the condenser on the exergetic efficiency of the NPP with heat pump, which uses the entire capacity of the turbine condenser. The analysis of the obtained results showed that the exergetic efficiency due to the increase in electric power released in winter increases with the increase of the final pressure in the condenser. This is explained by an increase in the heat pump coefficient of performance.

Analysis of key influencing factors for multi-mode solar heat pump systems

To further improve the stability and renewable energy utilization of the compound heat source heat pump system under complex operating conditions, a multi-mode solar heat pump system was proposed and a mathematical model was established in this paper. The accuracy of the model is verified by the experimental data, with the relative error within ±15%. The effects of the number of solar photovoltaic/thermal (PV/T) collectors (area), environmental parameters, and refrigerant flow rate on system performance are discussed separately for different models by the validated model. The results show that (1) PV/T-water source heat pump mode: the number of PV/T collectors in parallel (area) increases to 3 (3.84 m2), and the system performance improves the most, subsequently weakening; (2) PV/T-water and air composite heat pump model: When the refrigerant distribution ratio in the double-pipe heat exchanger 1 is increased from 55% to 95%, the collector's heat collecting capacity, power generation efficiency, and system coefficient of performance (COP) increase by 8.99%, 1.22%, and 6.4%, respectively. Moreover, the increase in solar irradiance can promote more refrigerant flow into the double-pipe heat exchanger 1 and improve heat pump COP more than the effect of increased ambient temperature. The research results can provide an effective reference for further optimization of solar heat pump systems and full utilization of renewable energy.

건물유형 및 지역을 고려한 하천수 이용 수열 히트펌프 시스템의 연간 성능 분석

Recently, as interest in renewable energy has increased, research in various fields has been continuously conducted. Among them, interest in hydrothermal energy is increasing due to the revision of the enforcement decree in 2019. However, although various studies have been conducted on system demonstration, performance and economic feasibility analysis, heat exchangers, etc., studies on the performance of the water heat pump system considering the domestic region and building type are insufficient. Thus, in this study, an annual performance analysis of the water source heat pump system was performed using dynamic energy simulation considering the domestic region and building type. The regions were assumed to be Seoul, Daejeon, Busan, and Gwangju, and the building types were assumed to be office buildings, apartment houses, and greenhouses. As a result of heat pump Coefficient of Performance(COP) analysis, the cooling COP was an average of 4.01 by region and 3.99 by building type. Heating COP was 3.13 and 3.43, respectively. Also, when comparing the performance deviations by region and building type, the heating performance differed greatly depending on the building type, and the cooling performance showed a significant difference according to the region. Overall, it was confirmed that the cooling performance of the hydrothermal heat pump system was approximately 15% superior to the heating performance.

A method to evaluate the performance of an open loop geothermal system for mine water heat recovery

Purpose. To develop a method to evaluate hydrodynamic and thermal parameters of an open loop geothermal system with the discharge into surface water bodies as well as to test the method under real site conditions considering different technology options, geotechnical and thermodynamic factors. Methodology. We employed the relations of hydraulics and thermodynamics, performed an engineering review of open loop geothermal systems for mine water heat recovery, studied hydrodynamic and mining conditions of the colliery Novohrodivska No.2. The developed technique includes evaluating the temperature of rocks around flooded workings, the length of the hydraulic path and flow resistance of workings. Findings. The evaluated temperature of mine water entering on-ground heat exchangers ranges at 17.8 0.25 C, and the system thermal output is 1070 21 kW. Water temperature in flooded workings due to dilution with infiltration during the operation period of 25 years is expected to fall by 0.61.0 C, which decreases the thermal output by 5.68.3%. The estimated cooling of water during its rise in the shaft does not exceed 1C. The criterion of the geothermal system energy efficiency decreases from 1.8 when pumping close to the mine water level to 1.05 when pumping 460 m below the ground; the heat pump coefficient of performance (COP) reaches 5.0. Originality. The flow characteristics and hydraulic flow lengths at different horizons, the temperature of rocks around workings were found to be the dominant factors for the thermal output under steady flow. The pumping depth was proved to significantly affect the energy efficiency of the system. Practical value. The proposed method allows quantifying the energy criterion of an open loop geothermal system with the discharge into surface watercourses, which enables optimizing system performance indicators.

Decreasing the Load of Air to Water Heat Pump Systems on Electrical Grids

Abstract This article focuses on decreasing the energy taken from the electrical grid by air to water heat pumps in buildings that use renewable energy. Conventionally the majority of the produced renewable energy is not used directly to operate the heat pump. An energy management concept was developed, with a main new parameter – RCOP that enables to create an optimal working schedule that considers the renewable energy availability and heat pump coefficient of performance in relation to the weather. The concept was proven with computer models that use weather forecasts, renewable energy production, and heat demand. The achieved yearly savings in grid-electricity used by the heat pump were 14.3 %. The fluctuations in the grid load were decreased which as well were quantified by a lower standard deviation of the demand. In months with the best renewable energy availability, the grid electricity savings can reach up to 70 %.

Quantification and comparison of COP improvement approaches for large-scale ammonia heat pump systems

• Compares five approaches to improve the COP of large-scale ammonia heat pumps. • Evaluates both one-stage and two-stage HP cycles connected in series. • A pinch analysis optimizes the heat exchanger network between HP and heat sink. The number of large-scale heat pumps (HP) implemented in Danish district heating networks has increased in recent years. The installations are often custom-made solutions designed carefully to obtain a high Coefficient of Performance (COP). This study aims at quantifying and compare five approaches for improving the COP of a heat pump, with a one-stage ammonia cycle used as the reference case with sink temperatures of 50 °C/80 °C (in/out) and source temperatures of 10 °C/3 °C. The approaches include increased complexity of cycle layout, optimization of intermediate pressure in two-stage cycles, a connection of HP cycles in series, optimization of load share between heating capacity for HPs in series, and optimal design of heat exchanger networks (HEN). The latter is based on an implementation of pinch analysis to HP HENs. The results revealed an improvement in COP by +15.8% obtained with increased complexity of cycle layout (two-stage cycle with a low-stage desuperheater) compared to a COP of 2.98 for the reference case. Connecting up to three one-stage HPs and two-stage cycles in series improved COP by 4.42% and 24.5%, respectively. The benefit of optimal load share and intermediate pressure was less than 0.5 % points for all configurations compared to reference values based on theoretical approaches. Exploiting the potential for optimal HEN increased the potential to 10.4% for one-stage cycles in series and nearly 29% for two-stage cycles increasing the COP to a maximum of 3.84.

Performance and economic analysis of a heat pump water heater assisted regenerative solar still using latent heat storage

• Maximum hourly productivity of 1.73 kg/h was observed during peak sunshine hours. • Maximum productivity of 16.1 kg/day was observed during summer months. • Maximum and minimum daily efficiencies were estimated as 0.81 and 0.78, respectively. • Heat pump coefficient of performance was estimated in the range between 2.21 and 2.55. • Cost of distillate was estimated as 0.05471 USD per liter. • Payback period was estimated as 21.46 months for 275 days of operation. • CO 2 emissions is estimated as 26.8 tons for 275 days of operation in ten-year life. In this paper, the performance and economic analysis of a heat pump water heater assisted regenerative solar still using latent heat storage was experimentally studied. The heat released during condensation of water vapour inside the solar still was regenerated using a heat pump to pre-heat the saline water before entering the basin and producing hot water for domestic use. The experimental observations have been made under the influence of solar irradiation, ambient temperature and ambient wind speed. The results showed that the heat pump water heater assisted regenerative solar still has attained cumulative productivity between 14.0 and 16.0 kg/day during 12 h of operation. Moreover, the system delivers more than 100 L of hot water at 46.8–52.8 °C for domestic use. The monthly average coefficient of performance of the heat pump was estimated in the range between 2.21 and 2.55. The cost per litre of distillate obtained from the system is estimated as 0.05471 USD. The payback period was estimated as 21.46 months for 275 days of operation in a year at 12% interest and distillate selling price of 0.08 USD/litre. The water samples obtained from the experiments are suitable for drinking and met the Bureau of Indian Standard requirements.

Waste Heat Recovery from Servers Using an Air to Water Heat Pump

The analysis of advisability and profitability of using an air to water heat pump for the purpose of waste heat recovery from servers being used as cryptocurrency mining rigs, was performed. To carry out such an analysis, the cooling unit of the computing server was connected to the heat pump, and the entire system was adequately equipped with devices measuring parameters of the process. Performed experiments proves that the heat pump coefficient of performance (COP) reaches satisfactory values (i.e., an average of 4.21), what is the result of stable and high-temperature source of heat at the pump inlet (i.e., in the range of 29.9-34.1). Economic analysis shows a significant reduction in the cost of heating domestic hot water (by nearly 59-61%). The main conclusion which can be drawn from the paper, is that in a case of having a waste heat source in a form of a server or similar, it is advisable to consider the purchase of air-to-water heat pump for the purpose of domestic hot water heating.

Thermo-economic analysis of working fluids for a ground source heat pump for domestic uses

Ground source heat pump, due to high coefficient of performance (COP) and use of low-temperature thermal energy source, is one of the best technologies to use renewable energy resources. In this work, at first, a geothermal heat pump for heating with an economizer is simulated, and then the effects of the variations in different parameters such as evaporator pressure, condensation pressure, and intermediate pressure on heat pump and total COP and exergy efficiency are analyzed. Initially, the thermodynamic simulation of the system is performed for different working fluids (R134a, R-12, R152a, R1234yf, and R1234ze(E)) in the EES software programming environment. The COP and exergy efficiency are calculated for different working fluids and obtained optimal values. The best overall coefficient of performance of the system is related to fluid R134a with a value of 3.663 and the best overall exergy efficiency of the system is related to fluid R1234ze(E) with a value of 0.5517. The lowest PCEU value is for fluid R152a with 0.01247$ per kilowatt. It can be concluded that by reducing the evaporator pressure of the cycle, the cost of producing an energy unit will be cheaper and by reducing the middle pressure of the cycle, the cost of producing an energy unit will be more expensive.

Investigation and optimization of a solar-assisted pumped thermal energy storage system with flat plate collectors

The objective of this work is the investigation of a solar-assisted pumped thermal energy storage system. The examined unit includes a solar field with flat plate collectors, a high-temperature heat pump, a latent storage system and an organic Rankine cycle. This system is fed by electricity from any renewable energy source (e.g., wind turbines or photovoltaic panels), and so the compressor of the heat pump is driven. The heat pump is fed with low-temperature heat from flat plate collectors, and it rejects heat of medium temperature to a latent storage system. The next step is exploiting the stored heat from an organic Rankine cycle for power production when there is a need for using electricity. The studied system is a “heat and power to power” system and can lead to high power recovery ratios. The analysis was conducted with a developed mathematical program in Engineering Equation Solver, and it was validated with numerical results from the literature. The optimum storage temperature has been found at 150 °C and the optimum temperature in the evaporator of the heat pump at 75 °C. In this case, the electricity recovery ratio (or power to power ratio) is found at 68.48%, the organic Rankine cycle efficiency at 18.45%, and the heat pump coefficient of performance at 3.704, while the collecting area is 150 m2. The use of a similar system without solar collectors but with the ambient as the heat source leads only to a 32.14% power recovery ratio. So, the specific gain of the used collecting area is 35.17 W/m2 which is an important amount of electricity. In the global optimum case, the simple payback period of the solar field investment is found to be at 7.8 years, which is a reasonable value and proves the financial viability of the examined idea. Moreover, this work proves that providing heat input of a relatively high temperature in the heat pump of the pumped thermal energy storage system is an excellent choice for recovering higher amounts of electricity.