Combined Heat Pump Research Articles

Study and optimization of the influence of the water tank temperature on the performance of a solar assisted multi-source heat pump drying system

Solar assisted air source heat pump drying (SASHPD) system has been widely studied due to its excellent energy saving and high dried quality of product. To improve system performance, the control logic of a solar assisted multi-source heat pump drying (SMSHPD) system was investigated, and the simulation model and the experimental platform were established in this paper. The seasonal operating characteristics of the air source heat pump drying (ASHPD), the SASHPD and the SMSHPD modes were studied. The energy consumption, coefficient of performance (COP) and specific moisture extraction rate (SMER) of the three drying systems were calculated and analyzed. Additionally, the water tank temperature were also measured to determine the seasonal control logic of the drying system. It was found that compared to the ASHPD system, in summer, the energy consumption of the SASHPD system was reduced by 33.06 %, and COP and SMER was increased by 49.4 % and 49.38 %, respectively. Moreover, because of the high ambient temperature and water tank temperature, the experimental results indicated that only the SASHPD control logic should be implemented in summer. The maximum error of the simulation results was 9.1 % and the accuracy of the simulation model was confirmed. In autumn, the lower water tank temperature after drying illustrated that the solar energy can be more fully utilized, which explained why the performance of the SMSHPD mode was increased by 6.5 % compared to the SASHPD mode. Consequently, it is necessary to implement the SMSHPD control logic in autumn. Moreover, the operating temperature of the water source heat pump drying mode in autumn was optimized and the optimal temperature range was 28–54 °C. The average COP in one week after optimization was 6.21 % higher than that of the original operating temperature. Based on the validated simulation model, the optimal operating temperatures in spring and winter were also calculated and the control logic of the SMSHPD system operating in the four seasons were all obtained. This paper has important guiding significance for the reasonable choice of the control logic of a solar combined air source heat pump drying system.

Configurational Design of a Hybrid System Based on an Air–Water Heat Pump and Biomass Boiler for a Rural Dwelling

Hybrid energy systems combine multiple energy sources and storage technologies to enhance performance and meet diverse energy needs. Hybrid heat pump systems are particularly suitable for heating and cooling buildings in rural areas. Air-source heat pumps have two well-known disadvantages during the coldest period of the year, when the building’s heating load is at its peak: the heat pump’s capacity is reduced and it needs to perform defrost cycles. A potential solution is to size the heat pump to cover only a portion of the peak load and to use a second heat generator in a hybrid heat pump system. There is a gap in the literature regarding the configurational analysis of hybrid heat pump (HHP) systems, particularly in terms of combining heat pumps and biomass boilers, and evaluating their efficiency, economic aspects, and environmental impact. Thus, in this research, a dynamic model of a HHP system, consisting of an air-to-water heat pump paired with a biomass boiler as a backup, is presented. Various configurations of the HHP system have been developed to evaluate key performance indicators, such as efficiency, emissions, operational costs, and other relevant factors. The findings of this paper indicate that the energy performance of HHP systems is significantly affected by the system layout, heat pump size, cut-off temperature, and the control algorithm used to activate the heat generators. Moreover, series operation of HHP systems is not only more efficient than parallel operation but also results in lower emissions and reduced operation costs. As expected, the energy loss associated with defrost cycles significantly impacts the overall performance of a hybrid system based on an air-source heat pump. Finally, the impact of the cut-off temperature on the key parameters in the configuration analysis was examined, and the optimal performance of the HHP system, in terms of minimizing operational costs and emissions, was depicted using a heat map diagram.

Heat pump and thermal energy storage: Influences of photovoltaic, the control strategy, and price assumptions on the optimal design

Combining heat pump, thermal energy storage, and photovoltaic is a common option to increase renewable energy usage in building energy systems. While research finds that optimal system design depends on the control, design guidelines neglect an influence of (1) photovoltaic, (2) the supervisory control, and (3) prices assumptions on the design of heat pump and thermal energy storage. We analyze how these influences may impact the optimal design. To analyze possible impacts, a pre-screening approach is used to identify relevant model input combinations with a potentially high influence on the optimal design. Applying a simulation-based design optimization with a detailed building energy system model, we optimize three cases: no photovoltaic, no supervisory control, and a state-of-the-art supervisory control. Results indicate that cost optimal design does not change with photovoltaic or the supervisory control, but heat pump size increases with higher electricity prices. For the storage, maximizing the size achieves high self-sufficiency degrees, but cost optimal design changes only for selected price assumptions. Overall, we find that neglecting photovoltaic and surplus control in the system design is a valid assumption. However, price assumptions should be included to allow simple but optimal design rules in current guidelines.

Effect of thermoelectric subcooling on COP and energy consumption of a propane heat pump

The building sector has an important impact on the environment, being responsible for 30 % of the total greenhouse gas emissions. Knowing that the energy consumption devoted to HVAC systems accounts for 50 % of the total energy consumption of buildings, it is paramount to develop environmentally friendly technologies able to provide green space heating to the building sector. To that purpose, this manuscript presents a computational study on propane vapor compression heat pumps which include thermoelectric subcooling to boost their operation. The combination of these technologies has been proven in the past to be very beneficial for refrigeration systems and this study concludes for the first time that propane heat pumps can highly benefit from thermoelectric subcooling. The widely conducted research includes the following parameters: ambient temperatures from −20 to 15 °C, voltage supplies to the thermoelectric modules from 0.5 to 10 VDC, number of thermoelectric subcooling blocks from 1 to 8 and two water inlet temperatures, 40 and 55 °C to study their influence on heating capacity, compressor and thermoelectric power consumptions, subcooling degree, propane mass flow, compressor capacity, COP, energy consumption and SCOP of the combined heat pump. The obtained results are very conclusive, COP enhancements up to 12.29 % are achieved when a thermoelectric subcooler with 16 modules is included in a propane heat pump already provided with an internal heat exchanger for an ambient temperature of −20 °C and a water inlet temperature of 55 °C. Additionally, improvements in Seasonal COP up to 9.98 % are achieved if the above-mentioned technologies integration between a vapor compression heat pump and a thermoelectric subcooler substitutes a conventional propane heat pump with an internal heat exchanger for space heating a single-story two-family house.

Combined solar and ground source heat pump heating system with a latent heat storage tank as a sustainable system to replace an oilfield hot water station

Present study focuses on a clean energy replacement for an oilfield hot water station and develops a combined solar and ground source heat pump (GSHP) heating system with a latent heat storage tank (LHST). The effects of LHST and heat replenishment on energy and coefficient of performance (COP) are quantitatively analyzed during short-term or long-term operation of the system. The suitability of three different phase change materials for the system is compared, and the optimal one is identified. Results show that the LHST with 70 °C melting point can increase the collector efficiency to 53.91 % and reduce the total energy consumption of the system by 52344 kWh. Heat replenishment could effectively mitigate the ground temperature drop to 0.19 °C/year, reducing the annual energy consumption of GSHP by more than 4230 kWh and providing an additional thermal energy of 72 GJ. Compared to the initial heating system, the novel system efficiency increases to 51.25 %. Gas consumption and total system energy consumption decreased by 81.7 % and 75.2 %, respectively. Annual reduction of CO2 emission is about 1150 tons, showing satisfactory performance. Outcomes of this study prove the application of clean energy in oil field industrial processes, and help in achieving the goals of emission reduction and carbon neutrality.

Study on photovoltaic combined air source heat pump heating system under typical meteorological conditions

Abstract This paper proposes a photovoltaic (PV) combined air source heat pump heating system for rural areas in severe cold regions of northern China, where the current clean heating methods have high costs and low efficiency. The paper uses meteonorm8 and TRNSYS software to derive the typical meteorological parameters and simulate the system performance in a guard room in Shenyang city. The paper analyzes the heat pump power consumption, PV cell power generation, and economic and environmental benefits of the system under different outdoor temperatures in the heating season. The results show that the system can meet the heating demand and maintain a comfortable indoor temperature, with an annual cost of 1603 RMB, which is 61.33% lower than a single heat pump system. The system can also reduce the emissions of carbon dioxide, sulfur dioxide, and dust by 2619.43 kg, 10.78 kg, and 6.91 kg per year, respectively, demonstrating its economic feasibility and environmental contribution.

Evaluating the Energy Efficiency of Combining Heat Pumps and Photovoltaic Panels in Eco-Friendly Housing

This article aims to analyze the energy efficiency of combining heat pumps with photovoltaic (PV) panels in energy-efficient homes. The research methodology involved a detailed energy balance analysis, assessment of the impact of mechanical ventilation, location, heat loss, and the choice and operation of heat sources, with a particular focus on heat pumps in synergy with PV installations. The results demonstrate that integrating heat pumps with PV panels can significantly reduce the demand for external energy sources and lower the operating costs of buildings, while contributing to their energy self-sufficiency. This study highlights that such a combination of technologies is key to promoting sustainable development and achieving energy efficiency goals in the residential sector. The results of this analysis expand knowledge about the effectiveness of such systems and provide practical recommendations for designers and engineers interested in implementing renewable energy technologies in modern energy-efficient buildings, taking into account the impact of these solutions on reducing CO2 emissions as well.

Sustainable Heat Supply for Greenhouses with Heatpumps

The heating of greenhouses in Germany is yearly responsible for the emission of about 3 million tCO2eq. In the small horticultural city of Straelen in North-west Germany, the possibility to partially replace the heat supply of greenhouses with heat pumps instead of CO2-intensive coal and oil boilers has been investigated. Different scenarios based on the power of the heat pump and the type of source (air or ground) have been simulated and compared economically and ecologically. Over the lifetime of the whole system, the levelized cost of heat for a combined heat pump & gas boiler heating system is lower than the reference case (coal & gas boilers). The installation of a heatpump covering at least 70% of the yearly heat demand would reduce the CO2-emission from minimum 70%.

Energy efficiency analysis of novel combined open absorption multifunctional heat pump and FlashME desalination system with a compressed air dryer

Energy intensive thermal desalination and compressed air-drying processes coupled with low grade heat recovery units can significantly contribute to carbon and energy footprint reduction. In this paper, a novel combined system based on an open absorption multifunctional heat pump and FlashME desalination system with a compressed air dryer is proposed to recover the latent heat from flue gas and efficiently utilize it to drive the desalination process for seawater treatment and supply the compressed dry air. The energy performance of the combined system is analyzed under the effect of various key operational parameters by simulating the validated process model. The results of energy analysis indicate that the novel system can recover the latent waste heat from flue gas with an efficiency of 83.02 % and supply the compressed dry air at low humidity of 1.41 g/kg by operating at a thermal COP of 1.95. Furthermore, the system can efficiently utilize the recovered low-grade heat to produce freshwater at a recovery rate of 23.14 %. The findings of the critical performance analysis show that the drying, and latent heat recovery performance of the coupled system is dependent mainly on the inlet parameters of the spray solution and the flue gas humidity. However, the water recovery of FlashME is totally dependent on heat capacity and the regeneration pressure such that the performance ratio increases from 1.51 to 4.03 by operating with hot seawater of 60–80 °C, when the regeneration pressure is raised up to 53.48 kPa. Moreover, the coupled system configured in parallel double stage can lower 11.43–37.78 % regeneration load along with 54.24 % improvement in distillate productivity when the operating pressure is raised up to 800 kPa and the rise in airflow rate in dryer can decrease the 10.41–52.45 % regeneration load on external heat source.

Renewable Energy Source (RES)-Based Polygeneration Systems for Multi-Family Houses

This research work synthetizes the energy, economic, and environmental aspects of a novel configurational analysis of four polygeneration schemes designed to fulfill the demands of a multi-family building that includes 12 dwellings. The design aims to meet the requirements (water, electricity, heat and cold air) from Renewable Energy Sources (RESs), in particular by selecting photovoltaic and photovoltaic-thermal panels, thermoelectric generators, and biomass as auxiliaries. Electricity is available from the grid, and no electrical storage is planned. Water and cooling may be produced by alternative technologies that configure the polygeneration alternatives. The case study is in Valencia, a coastal Mediterranean city in Spain. The Design Builder Clima estimated demand calculations, and the system performance was modeled in TRNSYS. Desalination was linked by using EES models. Results show that the suggested schemes offer substantial energy and CO2 savings. The innovative life-cycle analysis applied further enhances the cumulative CO2 savings across the four configurations if the impact of the installations is compared with the conventional external supply. The electric option (combining heat pump and reverse osmosis for cooling and desalination) emerged as the most appealing solution due to its reliability, lower investment cost, and environmental impact.

Research on the Application of Heat Pump with Different Coupling Methods in Heating Terminal

Under the dual pressure of energy supply and demand contradiction and increasingly severe environmental pollution, adopting clean energy to replace traditional fossil energy, reducing conventional energy consumption, and achieving clean heating is a necessary measure for China to build a resource-saving and environmentally friendly society. In order to achieve the above goals, heat pump technology is receiving attention and promotion from people. Analyze the application of solar and air source heat pump combined heating systems and water source heat pump and air source heat pump combined heating systems based on the comparison of two coupling methods and temperature distribution at different heating ends.

Effects of combined vacuum and heat pump drying on drying characteristics and physicochemical properties of pineapple

Vacuum drying (VD) and heat pump drying (HPD) are widely used in the food industry. However, their application is limited due to low drying efficiency and the resultant poor quality of dried products. Additionally, varying drying durations in combined drying can markedly impact the physical and chemical properties as well as the nutritional content of the dried product. To achieve the highest quality dried products, VD + HPD was initially compared and identified as the most suitable drying method. This paper investigates the impact of the first stage drying duration on the physical characteristics (color, microstructure, texture, volume shrinkage rate (VSR), rehydration rate (RR)) and bioactive components (total phenolic content (TPC), total flavonoid content (TFC), Polysaccharides) of pineapple. The results indicated that VD + HPD necessitated lower energy consumption and markedly enhanced the physical properties of dried products. The brightness, rehydration rate (RR), color difference, volume shrinkage rate (VSR), and surface microstructure of pineapple dried by VD 5h + HPD 5.5h were all optimal. In comparison with other tested drying methods, the textural properties (hardness, chewiness, viscosity) and bioactive components (TPC, Polysaccharides) exhibited significant improvement. Overall, these results indicate that VD5h + HPD5.5h can be viewed as a valuable technology for improving the quality of dried pineapples.

Effect of photovoltaic combined heat pump system on energy production: An Experimental Optimization

Effect of photovoltaic combined heat pump system on energy production: An Experimental Optimization

Adaptive Virtual Inertia Control for Combined Heat Pump and Biogas Engine Generator System: An Alternative Solution for Grid-Level Energy Storage

Adaptive Virtual Inertia Control for Combined Heat Pump and Biogas Engine Generator System: An Alternative Solution for Grid-Level Energy Storage

A Lumped-Parameter Model of a Smart Ventilation unit for nearly Zero Energy Buildings

In the present work, a simple model of a ventilation unit used for residential purposes is proposed, which was developed by means of MATLAB Simulink and the Simscape toolbox, also including the Moist Air and Two-Phase fluid libraries. This study falls in the realm of air conditioning in nearly Zero Energy Buildings. The model presented here is focused mostly on the aeraulic system. A parametric analysis of various installation conditions was conducted to assess and enhance the combined heat pump and the air distribution system performance, under various operating conditions. Therefore, the overall approach included several parameters, such as outdoor and indoor air temperature, humidity, static pressure, pressure drop in the intake and the distribution ducts, and filter fouling. The model serves as a predictive tool to evaluate the effectiveness of the whole system, in both design and off-design conditions; notably, critical conditions are emphasized, which are associated to severe fouling conditions, making the use of an additional fan ineffective.

Study on optimization of winter operation characteristics of solar-ground source heat pump in Shanghai

The operational characteristics of the combined solar-ground source heat pump system (referred to as SGSHPS) are influenced by local solar resources, climate characteristics, and operating modes. This paper aims to study the operational characteristics of SGSHPS in Shanghai under different operation modes, providing a reference for engineering applications of SGSHPS.Three operation modes were selected for this study: operation of the soil source heat pump, tandem operation mode 1, and tandem operation mode 2. The tandem operation mode 1 represents the heat pump source-side outlet fluid passing first through the buried pipe and then through the thermal storage tank, The tandem operation mode 2 represents the heat pump source-side outlet fluid passing first through the thermal storage tank and then through the buried pipe. The highest system COP was experimentally measured for tandem mode 1. TRNSYS software was used to construct the three oeration modes and obtain parameters such as unit COP, system COP, and buried pipe heat exchange.By comparing and analyzing the winter typical january month average system COP values obtained from experiments and simulations for each operation mode, The maximum error between the experimentally derived conclusions and the simulated conclusions is 9.9 %. The winter typical month january average system COP for the operation of the soil source heat pump was 3.26, while for tandem mode 1 it was 3.5, and for tandem mode 2 it was 3.44. Tandem mode 1 exhibited a 7 % higher system COP compared to the operation of the soil source heat pump, and a 1.7 % higher system COP compared to tandem mode 2. This indicates that the tandem operation of the solar-ground source heat pump is more energy-efficient than the operation of the soil source heat pump system. Therefore, tandem mode 1 is considered the optimal operating mode for SGSHPS in Shanghai during winter.

A dynamic programming based method for optimal control of a cascaded heat pump system with thermal energy storage

AbstractThe residential heating and cooling sector has been increasingly electrifying, predominantly using electrically driven heat pumps (HP) in combination with thermal/electrical energy storage systems. While these developments contribute to increased renewable and low carbon energy shares in the sector, exploiting the full potential of the technology requires a smart control of these systems that can account for predicted renewable energy availability in the future and the corresponding HP system performance. However, modelling a system featuring complex internal dynamics, in a way that is suitable for smart control, is challenging. Models need to be sophisticated enough to accurately capture the system's nonlinearities and intricacies while at the same time fast enough to enable a thorough search of the solutions space, in suitable computational time. Dynamic programming (DP) is a promising approach to smart controls, as it combines the ability to use complex, non-linear models while being an exhaustive search algorithm, guaranteeing that the global optimum is found. This paper presents an innovative modelling framework that entails reduced order models (ROM) of an HP substation's main components (i.e., HP and thermal energy storage—TES), elaborated in a fashion suitable for use in DP; these have been shaped as to include significant physical operating constraints (e.g., HP compressor variable speed, non-linear coefficient of performance—COP—dependency on outdoor and distribution temperature) affecting the system performance, while at the same time minimising the amount of state variables (i.e., TES temperatures, HP thermal and electric capacity) the optimizer needs to handle. In an application to an exemplary HP system, our system models compare remarkably well to detailed TRNSYS counterparts, used as a reference ground truth. The system achieves significant cost-saving enabled by the dynamic programming optimization approach, facilitating a 13% decrease in power consumption compared to conventional rule-based control.

Heating performance, exergy, and economic analysis of a heat pump drying system with an independent operating ability for drying shiitake mushrooms

In response to the problems of untimely drying in place of agricultural products after harvesting, low drying temperature of open heat pump drying system and low energy utilization of closed heat pump drying system. A novel heat pump drying system is proposed, which uses a gasoline generator as the power source and an open-closed combined heat pump system equipped with a box-type drying chamber. A prototype was constructed to investigate the feasibility and heating performance of this system, and experimental studies were carried out with wet towels and shiitake mushrooms as drying objects, and the system heating performance and specific moisture extraction rate (SMER) were analyzed. The results from the wet towels experiment revealed that the drying temperature decreased by 30%–74% when the system operation mode was the dehumidifying mode (open cycle) compared with the switching of the heating/dehumidifying mode. When the air speed was increased from 2.2 m/s to 4.3 m/s, the mass of water removed increased by 39.4%. The results of the shiitake mushrooms experiment showed that the SMER were 1.19 kg/kWh, 1.18 kg/kWh and 1.05 kg/kWh for gasoline generator drive and electric drive, respectively, which is an improvement of 42%∼61% comparing with the data of other researchers. This study provides guidance for heating performance and structural optimization of a new type of heat pump drying system driven by gasoline generator.

Exergy, exergoeconomic and exergoenvironmental assessments of experimental hybrid energy systems for hot water production to improve energy sustainability

Hybrid energy systems have proven their efficacy in improving energy sustainability. This paper focuses on the design and evaluation of various hybrid energy systems for hot water production in the experimental plant of the Laboratory for Quality Control in Buildings. The experimental facility was created to test and control various systems for energy supplies in buildings. In this work, three thermal installations were investigated: (1) a combined boiler cogeneration system, (2) a combined boiler solar collector system, and (3) a combined boiler heat pump system. After configuring each system in the laboratory, defining the control, and running the experimental essay, the corresponding data were obtained and treated. The exergy concept matches very well with the goal of promoting new systems that efficiently integrate renewable and nonrenewable energy resources. The exergy analysis and its extended assessments, the exergoeconomic and the exergoenvironmental, were applied to the designed systems. The results show that DHW production by the combined boiler solar thermal collector system is the most expensive in terms of the exergy cost index (about 33.29 kWhex/kWhex). DHW production by the combined boiler cogeneration system offers the lowest exergy unit cost (about 21.15 kWhex/kWhex). Based on economic and environmental indexes, DHW production by the combined boiler solar thermal collector system is the most suitable option. Its unit exergoeconomic cost is around 2.15 €/kWhex, and its exergoenvironmental unit impact is equal to 9.35 kg CO2/kWhex.

Performance characteristics of a compact self-circulating liquid desiccant air dehumidification system coupled with a heat pump: A comprehensive parametric study

Integration of a heat pump with a liquid desiccant system for air dehumidification has received growing attention in recent years in view of its more compact size and lower electricity consumption. This paper presents a compact combined heat pump and self-circulating liquid desiccant air dehumidification system targeted at small cooling load applications. The compactness lies in the integration of the dehumidifier and evaporator as well as the integration of the regenerator and condenser. Besides, the design of solution self-circulation (SSC) is intended for energy savings and the auxiliaries are employed to help achieve energy matching between the heat pump and the air dehumidification system. First, a comparative study is performed to identify the more energy efficient one of the two strategies for energy matching. Based on this, a thermodynamic model-based parametric study is conducted to investigate the effects of various influencing factors on the energy matching relationship and performance of the proposed system, as well as the energy-saving potential relative to the basic system without SSC. The results show that there exists an optimum solution self-circulation ratio (SCR) to achieve the maximum COP under a given condition. Basically, the proposed system with a proper SCR could yield a significant energy-saving effect regardless of the performance variations under studied operation conditions. It is found that a reduction of 29.68 % in energy consumption and an improvement of 42.20 % in COP are achieved under the ambient condition of 30 ℃ temperature and 20 g/kg humidity ratio. Furthermore, a correlation analysis is used to reveal the association strength and direction between any two main operation and performance parameters. Finally, the heat recovery is proved to effectively reduce the cooling coils load. This paper provides an in-depth understanding of the energy matching relationship and demonstrates the energy-saving performance benefiting from SSC for future practical applications of the proposed system.