Electric Heat Pumps Research Articles

Implementation of 1d/3d Integrated Model for Cabin Thermal Comfort and Energy-Saving Potential in Electric Vehicle Transcritical Co2 Heat Pump Air Conditioning System

Implementation of 1d/3d Integrated Model for Cabin Thermal Comfort and Energy-Saving Potential in Electric Vehicle Transcritical Co2 Heat Pump Air Conditioning System

Monte-Carlo Evaluation of Residential Energy System Morphologies Applying Device Agnostic Energy Management

Decarbonization requires new energy systems components to mitigate fossil fuel dependency, for instance electric vehicles and heat pumps, forming a sector integrated energy system. Energy management is a promising approach to integrate these devices more efficiently by orchestrating the respective consumption and generation. This study investigates the advantage of an advanced energy management algorithm that is applied to varying energy system scenarios. The energy management algorithm is based on economic principles and the system topology is represented by a rooted tree. Grid elements form parents, which act as auctioneers and devices act according to type specific demand and supply functions. This algorithm is compared to an approach where devices are not coordinated, at a system scale of six households. In order to account for different characteristics of the energy system, the different scenarios are defined according to a morphological analysis and are analysed by means of Monte-Carlo simulation. These scenarios vary the PV generation, heating technology, and building insulation. It is shown that the algorithm reduces peak loads across all scenarios by around 15 kW. Other key performance indicators, such as own consumption and self-sufficiency show a dependency on the scenarios, although the algorithm outperforms the reference in each one, achieving an increase in own consumption of at least 13 p.p. and 22 p.p. in terms of self-sufficiency.

Principle and Performance Optimization Analysis of a Frost-Free Control for Electric Vehicle Heat Pumps

Principle and Performance Optimization Analysis of a Frost-Free Control for Electric Vehicle Heat Pumps

The impacts of electric vehicles and heat pumps load profiles on low voltage distribution networks in Great Britain by 2050

The impacts of uptake and electricity load profiles of Electric Vehicles (EVs) and Heat Pumps (HPs) on the low voltage (LV) distribution networks were analyzed. The United Kingdom (UK) has a legally mandated policy concerning reduction of greenhouse gasses (GHGs) emissions. Therefore, the integration of low carbon technologies (LCTs) especially EVs and HPs at the LV networks is expected to increase in the drive to reducing the GHGs emissions. Future uptake scenarios, adapted from the National Grid studies, of EVs and HPs were developed for a real and typical urban LV distribution network in Great Britain (GB). Gridlab-D, an agent-based power system simulation software, was used to model the LV distribution network. The model was run for four different scenarios considering seasonal load profiles and projected EVs and HPs uptakes for each of the year 2020, 2030, 2040 and 2050 respectively. The results were analyzed in terms of transformer loading, voltage profiles of the feeders, and the ampacity loading of the cables for the different scenarios of the years.

Development of Planning and Operation Guidelines for Strategic Grid Planning of Urban Low-Voltage Grids with a New Supply Task

In contrast to rural distribution grids, which are mostly “feed-in oriented” in terms of electrical power, urban distribution grids are “load oriented”, as the number of customer connections and density of loads in urban areas is significantly higher than in rural areas. Taking into account the progressive electrification of the transport and heating sector, it is necessary to assess the required grid optimization or expansion measures from a conventional, as well as an innovative point of view. This is necessary in order to be able to contain the enormous investment volumes needed for transforming the energy system and aligning the infrastructures to their future requirements in time. Therefore, this article first explains the methodological approach of allocating scenarios of the development of electric mobility and heat pumps to analyzed grids. The article continues with describing which power values need to be applied and which conventional and innovative planning measures are available for avoiding voltage band violations and equipment overloads within the framework of strategic grid planning. Subsequently, the results of grid planning studies are outlined and evaluated with an assessment model that evaluates capital as well as operational costs. On this basis, planning and operation guidelines for urban low-voltage grids are derived. The main result is that low-voltage grids can accommodate charging infrastructure for electric mobility, as well as heat pumps to a certain degree. In addition, it is concluded that conventional planning measures are not completely avoidable, but can be partially avoided or deferred through dynamic load management.

Feasible Distributed Energy Supply Options for Household Energy Use in China from a Carbon Neutral Perspective.

This contribution firstly proposed the concept of annual average power generation hours and analyzed per capita energy consumption, carbon emission, and the human development index from a macro perspective. On this basis, we compared the average household electrical energy consumption of urban and rural residents based on the data from CGSS-2015 from a micro perspective. The results show the positive correlation between carbon emissions per capita and the human development index and China’s regional imbalance characteristics between household electricity consumption and renewable energy distribution. Therefore, the distributed energy supply system is proposed as an effective complement to centralized power generation systems and is the key to synergizing human development and carbon emissions in China. Moreover, we analyzed the characteristics of distributed energy supply systems in the context of existing energy supply systems, pointing out the need to fully use solar energy and natural gas. Finally, two types of typical distributed energy supply systems are proposed for satisfying the household energy requirements in remote or rural areas of western and the eastern or coastal areas of China, respectively. Two typical distributed energy systems integrate high-efficiency energy conversion, storage, and transfer devices such as electric heat pumps, photovoltaic thermal, heat and electricity storage, and fuel cells.

Investigating Hydrogen-Based Non-Conventional Storage for PV Power in Eco-Energetic Optimization of a Multi-Energy System

Through the integration of multiple energy carriers with related technologies, multi-energy systems (MES) can exploit the synergies coming from their interplay for several benefits towards decarbonization. In such a context, inclusion of Power-to-X technologies in periods of excess renewable electricity supply, removes the need for curtailment of renewable electricity generation. In order to achieve the environmental benefits of MES without neglecting their economic feasibility, the optimal design problem is as crucial as challenging and requires the adoption of a multi-objective approach. This paper extends the results of a previous work, by investigating hydrogen-based non-conventional storage for PV power in the eco-energetic optimization of an MES. The system under study consists of a reversible fuel cell (r-SOC), photovoltaic (PV), electric heat pump, absorption chiller and thermal storage, and allows satisfying the multi-energy needs of a residential end-user. A multi-objective linear problem is established to find the optimal MES configuration including the sizes of the involved technologies with the goal of reducing the total annual cost and the fossil primary energy input. Simulation results are compared with those obtained in previous work with a conventional nanogrid where a combined heat and power (CHP) system with gas-fired internal combustion engine and a battery were present instead of an r-SOC. The optimized configuration of the non-conventional nanogrid allows achieving a maximum primary energy reduction amounting to 66.3%, compared to the conventional nanogrid. In the face of the environmental benefits, the non-conventional nanogrid leads to an increase in total annual costs, which, compared to the conventional nanogrid, is in the range of 41–65%.

Intelligent of Electric Vehicle Heat Pump Air Conditioning Control System

Traditional fuel vehicles consume a lot of fuel and cause serious environmental pollution. At present, when environmental protection is being paid more and more attention, Electric vehicles have received extensive attention from countries all over the world for their advantages in energy safety, environmental protection and long-term development. Electric vehicles have received extensive attention from countries all over the world for their advantages in energy safety, environmental protection and long-term development. With the rapid development of electric vehicles, as the main energy consumer, following the electrical system, the air-conditioning system has become an important factor restricting the power, economy and durability of electric buses. At the same time, compared with the current electric heating PTC method commonly used in electric vehicles, heat pump air conditioners can increase the working range of electric vehicles. Therefore, the application of large-scale energy-saving systems, high-efficiency energy-saving systems, and electric vehicle air-conditioning systems is developed, it is of great significance to the promotion of electric vehicles. This article aims to intelligently study the control system of the electric vehicle air-conditioning heat pump.

Residential energy efficiency interventions: A meta-analysis of effectiveness studies.

Residential energy efficiency interventions: A meta-analysis of effectiveness studies.

Waste Heat Recovery by Air-to-Water Heat Pump from Exhausted Ventilating Air for Heating of Multi-Family Residential Buildings

The paper presents an analysis of the application of an air-to-water electric compressor heat pump (AWHP) for the recovery of waste heat from the exhaust air in a typical multifamily residential building and the use of this heat for space heating, as well as the impact of this solution on the building energy performance (the PPR index). Simulations were performed in TRNSYS for five locations in Poland (Koszalin, Wrocław, Lublin, Białystok, Suwałki), for various heating system parameters (80/60 °C, 75/65 °C, 70/50 °C, 55/45 °C, 35/28 °C), for various temperature limitations of heat pump operation. It was shown that the analyzed system has great potential from an energy and environmental point of view. It can provide significant benefits in terms of the energy performance of the building, depending on the system parameters. The results show that the most energy-efficient system is the one with the lowest heating system temperatures. Moreover, implementing a temperature limitation on the heat pump operation improves its efficiency, but the higher the design parameters of the heating installation and the lower the limitation, the lower the heat pump contribution, and the higher the SCOP and the PPR. The energy effect is also influenced by location, but its scale depends on the parameters of the heating system and the temperature limitation of the heat pump’s operation. It is more significant for lower heating system parameters. This system enables the possibility of further reducing the demand for nonrenewable primary energy by powering the heat pump with photovoltaic cells.

Investigation on the performance enhancement of electric vehicle heat pump system with air-to-air regenerative heat exchanger in cold condition

Since the heat pump operation in low ambient temperature requires considerable amount of electric energy, electric vehicles (EVs) suffer from the significant range loss problem in cold regions. In this study, heat pump system with air-to-air regenerative heat exchanger (ARHX) is suggested as a way to improve the energy inefficiency in the ventilation or dehumidification process. In recirculation mode, ARHX reduces heating and dehumidification load by utilizing the temperature difference of two air streams, occurring in the subsequent dehumidification and heating process. In outdoor air mode, ARHX enhances heating performance by recovering the heat from the preconditioned cabin air, which is exhausted to the environment in conventional heat pump system. Heat pump model was built upon an experimentally validated component model and thermal load model. Based on this heat pump model, performance enhancement of the proposed system is investigated in both recirculation and outdoor air mode with various climate conditions. Results confirm that suggested heat pump system decreases heating load and dehumidification load up to 12.3% and 12.9% in recirculation mode and the heating load reduction reaches 20.2% in outdoor air mode. Power consumption of the compressor is saved up to 10.6% in recirculation mode and 55% in outdoor air mode.

Renewable hydrogen driven CHCP device

Rural Research Stations (RRS), Refugee Camps Motorhomes and Caravans are in need of a portable Compact Heating, Cooling and Power (CHCP) generating device. Heating and power generation devices with diesel as driving source of energy are available commercially. In this paper, an innovative compact heating, cooling and power generating device which uses renewable hydrogen and suits rural areas, extreme weather conditions and disastrous situations is proposed. The device is driven by renewable hydrogen fuel generated by PV electrolysis as the source of energy. Low vibration low noise Stirling Engine (SE) is used as mechanical energy converter. Generator is used as electrical energy converter and heat pump is used for supplying heating and cooling effects. The proposed device has many advantages such as encouraging the rural tourism, supply rural research stations the heating and/or cooling loads and contribute in saving lives in the extreme weather conditions and disastrous situations. Analysis of the proposed device in terms of workability and performance was performed. Results showed that renewable energy base, electricity independent, silent, low vibration and better performance were achieved (OHR = 2.662) with the current device compared to available devices.

A novel defrosting initiating strategy for automotive air conditioner heat pumps based on frost thickness growth prediction

Automotive air conditioning heat pump systems draw increasing attention as an alternative to conventional electric heaters. Once the air temperature falls below the freezing point, frost begins to form on the surface of the evaporator. The accurate defrost strategies could avoid heat exchange efficiency reduction and prevent heating capacity from decaying, which are the main factors affecting the energy efficiency of electric vehicle heat pump systems. The frost characteristic on micro-channel heat exchanger of the electric vehicle heat pump system is tested, and a novel defrosting strategy which is based on the dimensionless analysis method is introduced too. Conclusions could be drawn as following: a correlation that considers the effects of ambient parameters and structural parameters has been developed to predict the frost thickness on fins with dimensionless analyses. Based on this correlation, the relative error and the RMS error between the experimental data and the predicted value are 8.44% and 12.54%, respectively; the effective blockage ratio (EBR), a parameter that accurately reflects the blockage ratio and directly linked to the system operation state, is first proposed. Through the analysis between the EBR and system heating capacity, it can be concluded that the optimal defrosting start-point is identified as the EBR reaches 30%. With this method, the defrosting start-time can be found accurately and effectively to avoid unnecessary defrost cycles, thus leading to a highly efficient operation and low energy consumption for the electric vehicle heat pump system.

Empirical evaluation of energy profiles of thermally-efficient homes with smart energy systems and controls

Smart control technologies are beginning to be deployed in homes to optimise heating and alter the timing of domestic energy demand to enable residential demand side response (DSR). This paper presents before (baseline phase) and after (control phase) evaluation of the monitored indoor temperature and energy demand during the heating season in 10 new-build dwellings, each of which received a 5kWh electro-chemical battery and smart control to enable shifting of heating energy demand. The dwellings had air source heat pumps (ASHP) and 2kWp solar photovoltaic (PV) panels, and were located in a social housing estate in Barnsley, England. For eight dwellings, heat pump electricity use per heating degree day was found to decrease by 10% and narrow baseline peaks were suppressed during the control phase. Daily mean grid electricity import and heat pump electricity use in the peak period (4pm – 7pm) were measured as 4.0 kWh and 1.4 kWh during the control phase as compared to 3.8kWh and 1.3 kWh for the baseline phase. However the use of a flat tariff (single-rate) meant that battery charging-discharging capability was not fully utilised. Time-of-use tariff would further enhance cost savings associated with the change in the timing of energy demand.

Ejector optimization and performance analysis of electric vehicle CO2 heat pump with dual ejectors

The performance of fixed ejector is limited by working conditions, so it is difficult to meet the operating requirements of electric vehicle heat pump system under varying conditions and wide temperature range. In this paper, a transcritical CO2 refrigeration cycle with dual ejectors in parallel (DEP) for electric vehicle heat pump system is established and its operation condition weight statistics method in all climate is proposed. On this basis, a fixed ejector optimization method based on the genetic algorithm is proposed, which takes the increment of integrated part load value (ΔIPLV) compared to the conventional transcritical CO2 refrigeration cycle (CON) system as the evaluation index. The performance analysis results show that under the cooling conditions, the coefficient of performance (COP) of DEP system with the optimized ejector for cooling is increased by 17.32%–23.42% compared to the CON system, and the COP of the transcritical CO2 refrigeration cycle with a single ejector (SEJ) system is increased by 7.31%–9.47%. In the heating mode, the COP of DEP system with the optimized ejector for heating is increased by 18%–19.79%, while the COP of SEJ system with the unoptimized ejector is decreased by 0.07%–2.43%.

Coordination of dynamic tariff and scheduled reprofiling product for day-ahead congestion management of distribution networks

The increasing penetration of distributed energy resources in distribution networks poses new challenges to the secure and efficient operation of distribution networks. One major challenge is the network congestion caused by the non-coordinated operation of flexible demands, such as electrical vehicles and heat pumps. In general, there are two categories of market-based day-ahead congestion management methods for distribution networks: price-based method and incentive-based method. In order to use the synergy of the two types of methods and to resolve potential conflicts against regulations when one type of method is implemented solely, a coordination scheme of the two types of methods is proposed for efficient day-ahead congestion management. In the proposed coordination scheme, the dynamic tariff (DT) as a price signal is used to partly resolve congestion firstly, and the scheduled reprofiling product (SRP) as an incentive-based flexibility service product is used to deal with the remaining congestion. By employing the coordination scheme, the distribution system operator (DSO) holds the profit neutral position in terms of congestion management, denoting that the DSO does not have the congestion management cost or revenue. Based on the DT model and SRP-based model, the coordination problem is formulated as a two-level non-convex mixed-integer non-linear programming (MINLP) model that is transformed into a one-level MINLP model with linear constraints and is solved by a proposed particle swarm optimization-based solution strategy. The Roy Billinton Test System was used to conduct case studies to validate the effectiveness of the proposed coordination scheme for day-ahead congestion management in distribution networks. The case study results demonstrate that the proposed coordination scheme can efficiently resolve congestion by the coordination of the DTs and SRPs while ensuring that the DSO is in a profit neutral position.

Control optimization of PV powered electric storage and heat pump water heaters

Domestic rooftop photovoltaic (PV) systems are typically installed without energy storage and power generated in excess of the building electric load must be exported to the grid or curtailed. In this paper the use of excess PV electricity for water heating is investigated, with the hot water storage tank acting as a low-cost thermal battery. A 3.6 kWp PV system installed on a domestic house with a 315 L storage hot water heater is analysed. It is shown that advanced control of the water heater is critical to make effective use of local intermittent PV power. Without appropriate controls the excess PV power can only reduce the grid energy consumption of an electric storage water heater by approximately 13%. However, with appropriate control, savings of purchased grid electricity above 80% can be achieved for electric storage water heaters. Similarly, using a heat pump, the consumption of purchased grid electricity for water heating can be reduced by close to 90% by making use of excess PV power. The use of excess PV electricity for water heating purposes can also significantly reduce export PV electricity, thereby also assisting the voltage and frequency stabilisation of the electrical distribution network.

Experimental evaluation of cycle performance for new-developed refrigerants in the electric vehicle heat pump systems

The heat pump is increasingly popular for the electric vehicles (EVs), however, there are no appropriate refrigerants. To provide long-term and environmental-friendly refrigerants in the heat pump for EVs, a test bench that can investigate the performance of an R410A prototype was built. The drop-in tests of three refrigerants (M1, M2, M3) developed previously with ultra-low GWP were carried out. The cooling and heating cycle performance were measured for R410A and alternative refrigerants. Experimental results showed the optimal refrigerant charge for the alternatives was less by 36-44% than that of the R410A system. For M1 and M2, the heating capacities showed 85-99% of those of the R410A system, with COP being 94-112%; the cooling capacities showed 94-109% of those of the R410A system, with COP being 99-107%. M3 showed much better COP than that of R410A system. The pressure drops were lower than those of R410A up to 21.6%, 25% and 55.7% for M1, M2 and M3, respectively. Furthermore, the alternative refrigerants showed better temperature match with air in the evaporator and condenser, the irreversible loss in the heat exchangers was also analyzed. This research will contribute to providing appropriate refrigerant substitutes in heat pump for EVs.

A Variable Performance Parameters Temperature–Flowrate Scheduling Model for Integrated Energy Systems

Optimal scheduling strategy of integrated energy systems (IES) with combined cooling, heating and power (CCHP) has become increasingly important. In order to make the scheduling strategy fit to the practical implementation, this paper proposes a variable performance parameters temperature–flowrate scheduling model for IES with CCHP. The novel scheduling model is established by taking flowrate and temperature as decision variables directly. In addition, performance parameters are treated as variables rather than constants in the proposed model. Specifically, the efficiencies of the gas turbine and the waste heating boiler are estimated with the partial load factor, and the coefficient of performance (COP) of the electrical chillers and heat pumps are estimated with the partial load factor and outlet water temperature. Then, to deal with the model nonlinearities caused by considering the variability of COPs, the COP-expansion method is developed by adopting a specific representation of the COP and the expansion of the outlet water temperature. Finally, case studies show that the variable performance parameters’ temperature–flowrate scheduling model can account for the variation of performance parameters, especially the impacts of water temperature and the part load factor on the COP. Therefore, the proposed scheduling model can obtain more adequate and feasible operation strategy, thereby suggesting its applicability in engineering practice.

Impact of demand management with load frequency control in distribution network with high penetration of renewable energy sources

Renewable sources are deployed to meet the growing needs of the energy demand. Integration of these renewable sources in a power system leads to increased complexity due to which it is essential to adapt new control strategies to retain system stability by preserving frequency in a nominal value. Therefore, the objective of the work is to control the load frequency of an interconnected hybrid (wind, solar, thermal) power system by optimizing generator cost while implementing the demand management technique. Deviation in the frequency and tie-line power due to fluctuation of renewable energy sources and load is addressed. For cost optimization, demand management technique was applied to the distribution system comprising flexible loads such as electric vehicle and heat pump. Voltage constraints and network congestion in the system are considered. The cascaded control technique is proposed for load frequency control and firefly based controller for cost optimization in the thermal power system. In the cascaded controller, proportional integral derivative (PID) and atom search optimization algorithm-tuned PID controller are recommended. Performance of the projected approach is compared with a PID controller and fuzzy logic controller-based load frequency control. Simulation studies and the result of various test cases considered clearly show the effectiveness of the controller implemented in the proposed system.