Heat Pump Manufacturers Research Articles

Environmental footprint analysis of domestic air source heat pumps

Air source heat pumps (ASHP) are increasingly being recognised as a low carbon alternative to traditional fossil fuel type heating systems for residential buildings, with many countries targeting their mass deployment to meet their emissions reduction goals. However, the environmental impacts of ASHPs throughout their entire life cycle to include manufacture and end-of-life, as well as operation, have not received comprehensive attention to date. This study addresses this gap by conducting a review of research quantifying the life cycle impact of domestic ASHPs, coupled with an examination of technology uptake and deployment. By analysing the entire life cycle, from production to end-of-life, the global warming potential of a 6 kW ASHP is estimated to be 35.8 t CO2 equivalent over the lifetime of 17 years identified by the study. Additionally, the study conducts a comparative analysis of the operational footprint based on a range of electricity carbon footprint and suggests possible improvement of 1200 % with targeted improvments. Furthermore, the study calculates the global warming potential using both the seasonal performance factor specified by a heat pump manufacturer and real-world field trial data. The findings unveil a significant disparity of 20 % between the two methodologies, underscoring the paramount importance of incorporating in-field heat pump performance data when evaluating their environmental impact.

Research on the effect of the refrigerant charge in a variable capacity heat pump

Current energy efficiency regulations have led to the development of heat pumps equipped with variable speed compressors (VSC) and electronic expansion valves (EEV). To reduce the amount of refrigerant charge, heat pump manufacturers are developing units without a liquid receiver. As a result, the amount of refrigerant charge has a direct impact on the unit performance and needs to be optimized. Previous studies have shown the existence of an optimum refrigerant charge that maximizes the COP at a given operating condition. However, with VSC it is not clear if the optimum charge at a given compressor speed is the adequate one at other speed values. This paper analyzes the effects of the refrigerant charge amount on the performance of a brine-to-water heat pump equipped with a VSC and an EEV. For a given compressor speed, the variation of the COP with the charge showed similar trends and an optimum refrigerant charge could be identified. The charge for the maximum COP changes slightly with the compressor speed. The seasonal coefficient of performance (SCOP) is proposed as a better metric for evaluating the optimum charge. Results show that the SCOP is quite stable with the refrigerant charge.

Hybrid Heat Pump Performance Evaluation in Different Operation Modes for Single-Family House

Hybrid heat pump (HHP) represents a heating system (HS) that simultaneously utilises two or more energy sources. The key novelty is the integration of an optimised control strategy, effectively maximising the efficiency of both the heat pump and gas boiler segments. In this study, a HHP system that consists of an air-source heat pump (ASHP) and a condensing-type gas boiler (GB) for a two-story single-family house was calculated and validated. The results from three different calculation methods were obtained: the heat pump manufacturer’s calculator, the simulator programme, and the calculations based on real measured data. Two operation modes were tested: economic mode, where the cheapest energy resource becomes the priority, and ecological mode, where the system operates using the energy resource with lowest CO2 emissions. When comparing consumed energy, there was a 15.36% variance between the manufacturer’s program and the actual measured data, while for produced energy, the difference amounted to 25.81%. It was found that the balance point temperature is −7 °C, where the heat pump unit of the HHP system can cover necessary heat losses until that point, while the gas boiler operates at lower temperatures. Changes in electricity price can significantly influence the point of the system switch, but the possibility to cover heat loads of the heat pump unit always has to be taken into account.

Performance assessment of R1234ze(E) as a low GWP substitute to R410A in fin-and-tube heat exchangers

Several energy efficiency regulations worldwide are forcing air conditioning and heat pump manufacturers to replace the halogenated refrigerants currently used in these systems, such as R410A, with more climate friendly alternatives that have a lower Global Warming Potential (GWP). This study explores how the performance of R1234ze(E) compares for an R410A based fin-and-tube evaporator coil. A total of 36 experiments were completed for both refrigerants, by means of a high-fidelity experimental facility, to validate a segment-by-segment heat exchanger model. For R410A, the mean absolute percent error between the experimental and simulated capacity was found to be 0.9%, and it was 1.4% for R1234ze(E). Simulations were then carried out, using the model, with R1234ze(E), where the fin density and refrigerant circuitry of the original heat exchanger were altered independently. By increasing the fin density from 15 to 20 fins per inch (FPI), the capacity increased by 4.9%, and refrigerant side pressure drop decreased by 4.5%. For the refrigerant circuitry optimizations, a maximum increase in capacity of 5.6% was observed when compared to the baseline, but at the expense of 7.5 times higher pressure drop. Alternatively, a separate circuitry resulted in a 38% pressure drop reduction and 2.5% reduction in capacity. The results demonstrated the relative sensitivity of capacity and refrigerant side pressure drop for R1234ze(E) on only two heat exchanger geometrical parameters. This sensitivity suggests potential for additional optimizations to heat exchanger designs for low-GWP refrigerants by performing further parametric analysis on heat exchanger geometry.

One-Dimensional Model of a Compact DHW Heat Pump with Experimental Validation

The current work presents a computationally cost-effective numerical model that successfully simulates a heat pump water heater (HPWH) under typical working conditions of dwellings. The model’s main components are a stratified tank and the heat-pump unit. Both systems are coupled, since a good prediction of water temperature is needed to accurately predict the heat-pump performance. Ten thermocouples measured the tank wall temperature. Measurements and simulations were performed under challenging conditions of a heavy stratification. The 190 L tank stratification was successfully modeled employing a 1D model, experimentally adjusted by three tapping cycles, with 6 × 22, 6 × 33, and 3 × 33 L consumptions, covering flowrates of 4 and 6 L/min. Water temperature is obtained with an uncertainty of 2.6 °C while the heat-pump was ON. A black box model has been used to obtain the heat-pump performance out of the external and condenser temperatures. For the analyzed days, the COP estimation presents an uncertainty of only 5.1%. Finally, an application example is included. It was used to simulate six tapping cycles of the European standard for heat pump water heaters testing (EN 16147). The results show the possibilities for heat-pump manufacturers of applying this calibrated model to predict the performance of HPWHs under different conditions.

An estimation of the European industrial heat pump market potential

This paper presents an estimation of the European (EU28) industrial heat pump market potential in terms of magnitude, sizing and number of units. This study is carried out in order to provide technology suppliers and manufacturers of industrial heat pumps perspectives for the technology. Potential heat pump applications in the food, paper, chemical and refining sectors are identified considering a maximum sink temperature of 200°C. This is achieved utilising a bottom-up methodology that uses detailed information from individual processes in the aforementioned sectors. Combining individual process data with typical plant capacities provides information on the heating capacities of heat pumps. The data is upscaled to European level, using production statistics relevant to the individual processes analysed. Since the database of processes is generic in nature and not fully covering the whole industrial sector, the results of this analysis provide a conservative estimate of the heat pump market potential. The results show a potential cumulative heating capacity of industrial heat pumps in EU28 of 23.0 GW, consisting of 4174 heat pump units which are able to cover 641 PJ/a of process heat demand. The largest number of heat pump units (%) can be found for heating capacities <10 MW, making up about 50% of the total market cumulative heating capacity. Clearly, there is a large market ahead for industrial heat pump manufacturers and suppliers.

Theoretical Minimum Thermal Load in Buildings

Summary Building cooling and heating accounts for a large portion of total global energy use and requires commensurate amounts of resources, which contribute significantly to global warming. Traditionally, addressing this issue has meant improving the efficiency of equipment supplying the thermal energy, reducing envelope heat transfer, and reducing air infiltration. However, this approach is already reaching practical limits. In this perspective, we explore (1) how to reduce thermal load in buildings theoretically and (2) how to achieve that reduction and dramatically lower the energy required to support building loads practically. First, we discuss our framework developed for calculating the theoretical minimum thermal load (TMTL) in buildings. Our analysis shows that current thermal loads in buildings are more than an order of magnitude higher than the TMTL. We also introduce an approximate formula to calculate energy savings from zonal control of thermal load, which shows that the majority of zonal control benefits can be achieved with fewer than 10 zones. Then, we discuss pros and cons of various approaches and strategies to achieve the TMTL. We conclude our perspective with some longer-term R&D ideas, such as thermally adaptive clothing and thermal storage to help approach the TMTL, while providing the additional benefit of interacting with the renewable grid of the future.

In-Use Performance of Air-to-Water Heat Pumps: are the Standards robust?

This paper presents an energy performance comparison of air to water heat pump manufacturer quoted values, calculated seasonal performance values from standards and actual in-use values for space heating mode only. Within this, the paper determines whether an in-use factor would be suitable to correct performance predictions where differences exist. The paper also presents an in-use Carnot efficiency. Over five weeks of high-resolution data during winter and shoulder season conditions were collected and analysed for three different systems. The average in-use Carnot efficiency was found to vary largely from system to system (0.19 to 0.42). All heat pumps were found to underperform on average with respect to their standardised energy performance certificate values. The difference between standardised values and in-use values was between 11% and 53% in relative terms. The gap in performance is thought to be due to oversized or under-utilised systems. Standardised methodologies appear unable to capture potential under-performance in these types of systems. An in-use factor appeared to be an inappropriate approach in reflecting this difference. Further investigations are required to incorporate these risks into standards.

Low Enthalpy Geothermal Resources for Local Sustainable Development: A Case Study in Poland

Many regions in Poland face the problem of air pollution. These regions include, though are not exclusive, to health resorts, an important element of the healthcare industry. Poor air quality is mainly associated with the domestic sector, which is dominated by individual solid fuel and coal boilers. One option for reducing emissions is to use alternative energy sources for heating purposes. Therefore, the paper presents an analysis into the possibility of using low enthalpy (low temperature) geothermal energy in health resort areas. The main purpose of the article is to estimate the potential of soil and water as the lower source for a heat pump. The article presents analyses of geological and hydrogeological conditions based on which the thermal parameters of the rock mass were determined, which were thermal conductivity and unit heat output for 1800 operating hours per year. The calculated values were used to perform a spatial analysis of the data and create maps of the average thermal conductivity for horizontal ground heat exchangers (HGHE) to a depth of 2 and 10 m and vertical ground heat exchangers (VGHE) in depth ranges up to 30, 60, and 90 m. The heating power of the intakes, located in the research area, were estimated using empirical formulas. In addition, a detailed analysis of the physicochemical parameters of groundwater in terms of the requirements indicated by four heat pump manufacturers is presented. The results of the presented research makes it possible to assess the potential of low-temperature geothermal energy and to characterize the suitability of the selected location for the use of HGHE, VGHE, and wells. As a result, the discussed area was found to have a high potential for the use of ground source heat pumps and a moderate potential for the use of low-temperature systems based on groundwater.

Environmental performance analysis of a dual-source heat pump system

Using all phases of a life cycle assessment (LCA), this paper analyses the environmental impact of a dual-source heat pump (DSHP) system that uses either the air or the ground as external heat sources. Data on the production were provided by the manufacturer of the heat pump prototype. The use phase was considered by evaluating the seasonal and annual energy performance of the system, using dynamic simulations. The system maintenance and end-of-life were modelled in accordance with the current regulations and statistical data in this sector. The Ecoinvent database was used as a reference for background data. The ReCiPe, CED and IPCC 100a impact methods were used to assess the environmental impact categories. The results were compared with those of conventional air and ground source heat pump systems. A sensitivity study on the influence of the energy in the use phase was carried out in terms of a variation in energy use and for different energy mixes, including photovoltaic energy. The results demonstrated the environmental validity of the technology in comparison with the two conventional heat pumps used for residential applications in different conditions. The results could be used by heat pump manufacturers to improve the design and performance of their products, by designers in the selection of thermal technologies, and by researchers involved in the study of similar emerging renewable energy technologies.

Measured and simulated energy performance of OLK NZEB with heat pump and energy piles in Hämeenlinna

In this work, measured energy use of the building space heating, ventilation supply air heating, appliances and lighting is compared against simulated energy use modelled in IDA ICE. As built energy need and detailed measured input data is applied in building model calibration procedure. Calibrated building model energy performance is studied in both measured and test reference year climate conditions. Previously modelled as built plant automation and implemented control logics are compared against measured. Geothermal plant in this study consists of heat pump, solar collectors, boreholes and energy piles. Heat pump SCOP estimated by post processing according to heat pump manufacturer’s performance map is compared against measured SCOP on the monthly basis. Opinion on actual plant operation is given and energy performance improvement potential is quantified. Important parameters for successful building model calibration are presented. Building compliance with Finland NZEB requirements are assessed. The results show good match with measured energy use after the model calibration.

Techno-economic analysis of flexible heat pump controls

There exists a gap between the flexibility needed within the German energy system and the flexibility being actually provided. Heat pumps can be seen to be the core technology to couple the heating and electricity sectors and thereby provide flexibility to the system. We contribute to the scientific discussion by conducting validated simulations of realistic and easily applicable heat pump control methods that are implemented to provide flexibility and not limited to pilot trials. We assess effects on energy efficiency and economic potentials compared to standard reference control algorithms. The flexible control schemes under investigation can be divided into two categories: time-of-use based controls and spot market price based control. We investigate both control types for current market conditions and for future scenarios of the German electricity market in 2030. In our study, we introduce a validated MODELICA simulation model of a ground source heat pump and market models to evaluate financial consequences. Our results indicate that efficiency losses occur for all investigated control methods. Further, financial gains for heat pump owners could not be achieved with current price structures, only distinct future scenarios with high shares of fluctuating renewables and low electricity demand led to enough price fluctuations to allow for electricity cost savings. Thus, we conclude that (1) heat pump owners need to weigh pros and cons of currently applicable, flexible heat pump controls carefully before their implementation, (2) there exists a need for heat pump manufacturers to further develop controllers that are capable of more advanced control schemes on large-scale, (3) policy makers should establish market mechanisms to ensure that heat pump owners are provided with incentives to use flexible controls, and (4) scientific modelers should not only focus on the development of highly elaborated control methods, but also investigate their transferability to large-scale real-world applications in the near future.

The modelling of reverse defrosting cycles of air-to-water heat pumps with TRNSYS

The most widespread defrosting technique adopted by Air-Source Heat Pumps (ASHPs) during the heating season is Reverse Cycle Defrosting (RCD). In this paper a dynamic model of RCD, based on performance data provided by the heat pump manufacturer, designed for TRNSYS and with a core-structure suitable for commercial units, is presented. A defrost cycle is divided in three phases. First, the unit heating capacity is reduced as a linear function of the ice layer thickness (Pre-Defrost phase). Subsequently, the reverse cycle operating mode is modelled on the basis of the performance data given by the manufacturer (Defrost phase) and, finally, the heat pump performances are altered taking into account the higher surface temperature of the external coil after the reverse mode (Post-Defrost phase). Then, the influence of defrosting energy losses on the heat pump seasonal performance factor in sites characterized by different climatic conditions has been assessed. Results point out that the ASHP seasonal efficiency decreases of about 5% taking into account defrost energy losses; in addition, the influence of defrost cycles on the internal air temperature is studied by assessing under which conditions the indoor thermal comfort can be guaranteed even in presence of frequent defrost cycles.

Quasi-dynamic model of the energy efficiency for an air-to-water heat pump

The energy efficiency of air-to-water heat pump operating in an actual heating installation depends on many factors. In order to create a reliable model of the unit, it is necessary to include as many of them as possible. Unfortunately, the most common data provided by heat pump manufacturers are based on tests performed in accordance with the EN 14511 standard [1]. These tests are performed in steady-state conditions and do not provide reliable information on the impact of dynamic effects on the energy efficiency of the device. The solution may be the tests in quasi-dynamic conditions. The article presents the possibility of creating the characteristics of an air-to-water heat pumps based on operational data. The accuracy of the created model has been compared with the characteristics resulting from measurements in steady state conditions. It has been confirmed that dynamic test data, after proper selection, will allow to determine the characteristics of repeatable parameters and this can be an alternative to tests performed in fixed conditions.

Comparison of the operation performance of split and integrated type air source heat pump water heater via modelling and simulation

Modelling and simulating the performance of air source heat pump water heaters can guarantee better operation and routine maintenance of the system. The primary data used in the development of the models were collected from data acquisition system that was designed and employed to monitor the COP of installed 150 L integrated and split type ASHP water heaters under three scenarios of controlled volume of hot water drawn off. The study presents both mathematical models and simulation application developed for the COP of the two systems; using the temperature difference of the refrigerant at the compressor suction and discharge ends, the temperature difference of the refrigerant at the inlet and outlet of the condenser, the ambient temperature and the relative humidity as predictors. The results revealed that the split type performed better than the integrated type with significant difference in both summer and winter with a p-value of 1.34 × 10-10 and 0.0167, respectively. In addition, the derived models for the both systems had very good predictions for both the trained and validated dataset with determination coefficient of over 0.9. Furthermore, heat pump manufacturers and energy service company can easily use the derived models in the developed two dimensional multi-contour simulation plots and the simulation applications to show the variation and the impact of the COP with the various predictors for both systems.

The Quaternary groundwater as the low temperature energy source for heat pumps in Małopolska Province

The paper presents the assessment of using Quaternary groundwater as the low–temperature energy source for heat pumps in the Malopolska Province. The analysis demonstrates that the Malopolska region has potential to use Quaternary groundwater in low–temperature systems both in terms of potential well flow rates and water temperature. Water as a heat source must also meet the relevant requirements in terms of the physical and chemical parameters indicated by manufacturers of heat pumps as important for the proper operation of installations. The data for this study were obtained from the Polish Hydrogeological Survey (the PHS is carried out by the Polish Geological Institute — National Research Institute). In some cases, physical and chemical properties of water do not meet the requirements indicated by heat pump manufacturers. These requirements may be met by using recycled water or another medium whose parameters do not affect the life of the installation.

Life cycle assessment of domestic heat pump hot water systems in Australia

Water heating accounts for 23% of residential energy consumption in Australia, and, as over half is provided by electric water heaters, is a significant source of greenhouse gas emissions. Due to inclusion in rebate schemes heat pump water heating systems are becoming increasingly popular, but do they result in lower greenhouse gas emissions? This study follows on from a previous life cycle assessment study of domestic hot water systems to include heat pump systems. The streamlined life cycle assessment approach used focused on the use phase of the life cycle, which was found in the previous study to be where the majority of global warming potential (GWP) impacts occurred. Data was collected from an Australian heat pump manufacturer and was modelled assuming installation within Australian climate zone 3 (AS/NZS 4234:2011). Several scenarios were investigated for the heat pumps including different sources of electricity (grid, photovoltaic solar modules, and batteries) and the use of solar thermal panels. It was found that due to their higher efficiency heat pump hot water systems can result in significantly lower GWP than electric storage hot water systems. Further, solar thermal heat pump systems can have lower GWP than solar electric hot water systems that use conventional electric boosting. Additionally, the contributions of HFC refrigerants to GWP can be significant so the use of alternative refrigerants is recommended. Heat pumps combined with PV and battery technology can achieve the lowest GWP of all domestic hot water systems.

Partial load efficiency degradation of a water-to-water heat pump under fixed set-point control

A laboratory study was conducted to evaluate the influence of fixed set-point control strategies on the partial load behaviour of a water-to-water heat pump of 40.5kW heating capacity. Experimental results indicate that the control configuration is highly influential on the heat pump cycling response and efficiency degradation at part load. Deterioration of energy performance occurred mainly during system start-up, with additional efficiency loss caused by short cycling for supply temperature control at low loads. It was concluded that a minimum of 20min compressor run time is necessary to reduce degradation effects, suggesting that installers and heat pump manufacturers should ensure minimum operation times to improve systems efficiency. Comparison of models and experiments indicate that it is important to adequately account for both stand-by and start-up efficiency losses for improving predictions of part load performance by steady-state heat pump models.

A comprehensive study on the important faults in heat pump system during the warranty period

The heat pump market has become mature in many countries. There are millions of heat pumps installed worldwide. So any improvement in the installation, operation, and maintenance of heat pump systems can save a considerable amount of energy and cost, and reduce Green House Emissions to a large extent. The present study suggests a Smart Fault Detection and Diagnosis (SFDD) mechanism as the essential part of the next generation of heat pumps. A SFDD mechanism can minimize the installation and control errors, decrease the performance degradation during operation, avoid unnecessary visual inspections and components replacement, and reduce the maintenance cost and down-time of the system. To develop a SFDD mechanism, the first essential step is to obtain knowledge about the most common and expensive faults experienced by heat pumps. The heat pump manufacturers are one of the best sources to find out the most common and costliest faults occurring in heat pump systems during the first few years of their life. The present paper, as the first part of two, describes the results from a comprehensive study done on the most recent faults which were reported to some of the heat pump manufacturers in Sweden during the warranty period. The most common and the costliest faults in the Air/Air, Air/Water, Brine/Water, and exhaust air heat pumps are presented. Some of the faults such as faulty pressure switches or fans are only related to the heat pump unit, i.e. the thermodynamic cycle which facilitates the heat pumping cycle. Some of the common and expensive faults such as faulty shuttle or shunt valve are related to the faulty components in the heating systems. Generally, the results show that faults in Control and Electronics are almost the most common and costliest faults in all types of heat pumps. Faults in Control and Electronics include any fault related to control unit, electrical faults (such as short circuit, etc.), Printed Circuit Board (PCB), display, soft starter, overcurrent and motor protection relay, etc.

The Common and Costly Faults in Heat Pump Systems

The heat pump market has become mature in many countries. There are millions of heat pumps installed worldwide. So any improvement in the installation, operation, and maintenance of heat pump system can save a considerable amount of energy and cost, and reduce Green House Emissions to a large extent. In order to minimize the number of faults in installation and operation phases and improve the maintenance process, it is essential to obtain knowledge about the common and expensive faults which usually occur in the heat pump systems. Insurance companies and heat pump manufacturers (OEMs) are the best sources to find out the most common and costliest faults recently occurred in the heat pump systems. The present paper describes the results from a comprehensive study done on the most recent faults which were reported to both OEMs and insurance companies in Sweden. According to the results, it is essential to pay a special attention to the control and electronics in heat pump system in order to reduce the number and cost of the faults in the heat pump systems. Furthermore, the results show the importance of system thinking in any effort to minimize, detect or diagnose the faults in heat pump system.