Seasonal Coefficient Of Performance Research Articles

Techno-economic evaluation of a seawater source heat pump system with auxiliary heat source in cold region of China

The utilizing of renewable seawater energy through seawater source heat pumps (SWHPs) in coastal areas is considered as a sustainable technology with minimal environment impact. Promotion of this technology needs clear understanding of its techno-economic performance but there are limited relevant studies. An empirical study was conducted in Qingdao, China, based on a practical installation comprising SWHPs supplemented by electric boilers. On-site measurements revealed considerable COP of 3.81 for SWHP and COPs of 2.87 for the whole system, implying SWHP as a viable and efficient solution for space heating in mild winter in this region. Results from TRNSYS simulations showed SWHP with auxiliary gas boilers (SWHP-GB) achieved the lowest annual primary energy demand and best economic and environmental benefits compared with other three schemes, namely SWHP with electric boilers (SWHP-EB), chillers with gas boilers (Chiller-GB) and air source heat pumps with gas boilers (ASHP-GB). SWHP played important roles in energy efficiency of the whole system with a considerable seasonal COP of 3.72 and 3.22 respectively for heating and cooling. Annual primary energy demand of SWHP-GB accounted for 55 %, 78 % and 56 % of SWHP-EB, Chiller-GB and ASHP-GB, respectively. SWHP-GB achieved the lowest life cycle costs and a rapid payback period of 10.9 years. Moreover, using direct or indirect heat exchange with seawater was found with limited impact on techno-economic performance of the system. To conclude, SWHP-GB could be used as an efficient solution for building heating and cooling in northern coastal cities in China.

Analysis of the Cooperation of a Compressor Heat Pump with a PV System

The decarbonization of heating systems is one of the present political and legislative directions of the European Union and its Member States. The main activities concern the energy performance of buildings and energy efficiency. The mentioned UE directives are the basis for the financial support of high-emission fossil fuel thermal energy source replacement with emission-free ones, in particular heat pumps. Other aspects are the support of PV installations and the thermal insulation of buildings. 85% of EU buildings were built before 2000, and among those, 75% have poor energy performance. Therefore, a significant number of buildings have only high-temperature wall radiators, and this was a motivation to prepare this article. The main innovation of this research was a new theoretical design of a high-temperature heat pump based on ecological refrigerants. The presented solution allows wall radiators to receive a hot water supply with temperatures of up to 85 °C during external temperatures of up to −20 °C. Typical heat pumps do not have these kinds of parameters, so the authors decided to verify the possibility of operating this device in such a wide temperature range. Another important aspect was the analysis of PV support. Finally, this paper investigates the possibility of heating an energy-efficient house with the newly designed high-temperature heat pump. Depending on the location in Poland, i.e., Suwałki, Warsaw, and Wrocław, the total electric energy supplied to the compressors was 2538–3364 kWh. The energy provided by the PV to supply power to the compressors is 482–570 kWh. The achieved PV energy self-consumption is 16.9–19.0%. The Seasonal Coefficient of Performance (SCOP) of the heat pump is 1.825–2.038 without PV and 2.515–2.970 with PV.

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.

Analysis of rainwater use in membrane-based semi-direct evaporative cooling of air

The trend of seeking solutions to reduce energy consumption in buildings is evident in the context of heating, ventilation, and air conditioning technologies. One such solution with low energy consumption is direct evaporative cooling systems. However, the use of such systems is associated with an increase in fresh water consumption in buildings. The article presents a novel approach to air cooling, taking into account the sustainable building aims of designing buildings with low energy consumption and water conservation. The proposed system is a membrane-based semi-direct evaporative cooling system, which is fed by harvested rainwater. The study analyzed the potential of rainwater harvesting for direct evaporative cooling in ten cities. The cities selected for the analysis of system operation, are located in different climates according to the Köppen-Geiger classification. Water consumption for cooling at a base temperature of 26.7 °C was estimated using a mathematical model of the membrane module. Furthermore, the number of evaporative cooling hours per year was determined for this temperature. The system under analysis achieved a high coefficient of performance (COP) and a seasonal coefficient of performance (SCOP) of up to 183 and 133, respectively. Depending on the location of the building, the annual water consumption of the system ranged from 150 to 8859 dm3. The rainwater harvesting provided up to 100 % of the evaporative cooling requirements. The proposed solution reduces tap water consumption and lowers the temperature of fresh air supplied to indoor spaces while consuming low energy.

A small ammonia heat pump using linear compressor

The electrification of space heating and hot water via heat pumps is a widely pursued policy aim but field trials demonstrate poorer seasonal performance than anticipated. Linear compressors without crank mechanism can be oil-free. The potential for capacity modulation by adjusting the compressor stroke offers significant advantages over traditional methods including on-off control and variable frequency given that heat pumps operate at part load most of time. R717 (ammonia) has superior latent heat which offers a higher heating capacity compared to R134a, making it a very promising refrigerant for small heat pumps but there is no compatible compressor due to corrosivity. This paper introduces a novel small ammonia heat pump using an oil-free linear compressor technology that is compatible with R717. A numerical model was established to predict the heat pump baseline performance. The outcomes show a linear relation for specific power input, heating capacity, and Coefficient of Performance (COP) against ambient temperature. The system can achieve COP of 2 when ambient temperature is 0 °C. With linear compressor, there will be no on-off cycling for heat pumps so that the seasonal COP will be significantly higher than on-off control and variable frequency drive systems.

Comparative study on energy-saving performance of single- and two-stage evaporative-cooling condenser systems

The mechanical vapor compression system (MVC) coupled with the evaporative-cooling condenser is an effective method to improve its high temperature adaptability. However, this hybrid systems typically use an evaporative cooler as a single-stage pre-cooling unit of condenser and is mainly designed for hot–dry climates. In this paper, based on conventional evaporative-cooling condenser configuration, three two-stage evaporative-cooling condenser systems (MVC-TSEC(A), MVC-TSEC(B) and MVC-TSEC(C)) were proposed. The MVC-TSEC(A) consists of one condenser and an indirect/direct evaporative-cooler. The MVC-TSEC(B) and MVC-TSEC(C) have two condensers (in series), which are coupled with a two-stage evaporative cooling system. The refrigerant in the MVC-TSEC(C) forms a counter-flow configuration with the outdoor air, while it is concurrent flow in MVC-TSEC(B). Subsequently, the effects of the ambient parameters and outdoor air flowrate on the three two-stage hybrid systems were analyzed comparatively based on detailed numerical models. Finally, the application potential of these hybrid systems was evaluated comprehensively in hot–humid climates. The results showed that the seasonal COP and energy-saving rate for the MVC-TSEC(C) are reached by 4.2–4.7 and 12.7–21.1 %, respectively. Moreover, the static equipment payback period of the three two-stage hybrid systems are 3.8, 3.3 and 3.0 years, respectively.

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.

Case Study on the Heat Pump Integration for Enhanced Efficiency in Battery-Electric Short-Sea Ferries

This case study investigates the potential of incorporating water heat pumps into onboard thermal systems to utilize low-temperature waste heat for onboard heating and enhance the efficiency and economics of all-electric battery-driven ferries. We analysed a hybrid-driven roll-on/roll-off passenger ferry operating in the Baltic Sea, gathering data on vessel operation, power, and heat provision in low-temperature cycles. We integrated real-time measurement data, energy flow analysis, and thermodynamic calculations to draw conclusions for a potential battery retrofit scenario featuring an all-electric operation and a battery system capacity of 10 MWh. Our results indicate that the integration of heat pumps in battery-electric mode can cover more than 50 % of the onboard nominal heat capacity of HVAC systems, with a seasonal coefficient of performance (SCOP) of 3.5 during the heating season. The overall electric energy demand of the vessel during the 6-month heating period is reduced by approximately 8 % compared with direct-electric heating.

Technical evaluation of solar-activated absorption refrigeration systems and operating conditions: a case study in Culiacán-Mexico

This research shows the methodology for technical evaluations of the energy performance of absorption refrigeration systems activated with solar energy. This document determines the optimal installation angle of the solar thermal collectors that activate the chiller. Also, the cooling energy Qe, Coefficient of Performance (COP), and hourly Seasonal Coefficient of Performance (SCOP) are determined for each month of the year and recommendations are made for operation in the city of Culiacán, Mexico. The absorption cooling system achieved a Qe of 400.9 kW, a COP of 0.778, and a SCOP of 0.557.

Comparative study of three hybrid air-conditioning systems based on multiple evaporative coolers and run-around reheating coils

Existing evaporative-cooling hybrid air conditioning systems cannot fully utilize the synergistic energy-saving potential of multiple evaporative-cooling technologies. Moreover, they cannot meet simultaneously the energy-saving requirements of standard mechanical vapor compression (MVC) systems in the terms of fresh air pre-treatment, condenser pre-cooling and supply air reheating. Therefore, in this paper, integrating MVC system with the indirect evaporative cooler, outdoor-air evaporative-cooling unit, and run-around reheating coils, three alternative hybrid systems were proposed to meet the aforementioned three requirements. The three hybrid systems have different outdoor-air unit configurations (single condenser with direct evaporative cooler, dual condenser with direct evaporative cooler, and dual condenser with two-stage evaporative-cooling configuration) and reheat sources (exhaust, outdoor, and mixed air of fresh and return air). Then, the parameter effects and application potentials of the three hybrid systems were analyzed comparatively based on detailed numerical models. The results showed that the third proposed hybrid system (HAC-R3) exhibits the best energy-saving advantages in almost the range of ambient temperature, relative humidity and fresh airflow rate studied. The first proposed hybrid system (HAC-R1) has the simplest outdoor-air side configuration, which is also a good choice in medium–low humidity conditions. In hot-humid summer in southern China, HAC-R3 has the highest average energy-saving rate and seasonal COP of 16.0 % and 7.0 respectively. In addition, HAC-R1 has the lowest static equipment payback period of 3.3 years, slightly lower than that of HAC-R3 (3.4 years).

Comparative energy analysis of cooling energy performance between conventional and hybrid air source internet data center cooling system

The widespread need for data processing has led to an increase in internet data centers (IDCs), contributing to the generation of high heat loads and high energy usage. This study discusses a simulation model of a newly proposed cooling system applied to data centers for five selected climatic areas in South Korea. Using experimental data of the newly proposed system, performance correlations are developed by regression analysis method to estimate performance curve coefficients for energy modelling and simulation to predict the annual energy performance of the system and compare the performance with that of a conventional cooling system. The results showed an overall annual average energy efficiency of approximately 14.1% of the hybrid cooling system over the conventional cooling system. The mean seasonal coefficient of performance (SCOP) for the hybrid system and the conventional system is approximately 6.7 and 4.9 respectively for all cases in the winter period while a SCOP of 3.2 and 3.7 respectively for the summer period.

Long-term performance prediction of ground source heat pump system based on co-simulation and artificial neural network

Ground source heat pump (GSHP) systems are efficient and widely used form of shallow geothermal energy utilization. In practical application, GSHP systems face the problem in predicting the long-term performance and energy efficiency variations in GSHP systems in regions with thermal imbalances. In this study, a coupling heat transfer model of vertical ground heat exchanger (GHE), heat pump, and building load was established to achieve refined simulation calculations of the long-term operation of GSHP systems. Parametric modeling was conducted by employing the co-simulation of COMSOL and MATLAB, enabling dynamic simulations of 600 sets of GSHP system models throughout the entire year. A database was established by extracting the numerical results, and a prediction model was developed using artificial neural network (ANN) methodology to learn from the database. The model predicted the ground temperature, seasonal energy efficiency ratio (SEER), seasonal coefficient of performance (SCOP), annual electricity consumption, and annual energy savings of the GSHP system and the prediction model was valid. The results were used to estimate the ground temperature, coefficient of performance (COP), payback period for static investment, and carbon dioxide emission reduction. Finally, the prediction model was applied to a GSHP system engineering project in Yancheng, China, forecasting the operation performance of the system for 10 years. The accuracy of ANN in predicting 10 years of long-term performance is verified.

Retrofit of a standard split-type air conditioner into an air-to-water heat pump

In the context of the rising prices of energy and especially of natural gas, the interest in heat pumps has grown steadily over the last period, as they are a very convenient alternative to low and medium power thermal plants. Although the price of heat pumps has dropped a lot recently, these systems are still very expensive compared to the wall-mounted natural gas fuelled power plants found in the vast majority of residential buildings in Romania. In this context, the authors proposed the conversion of an inverter type air conditioner into an air-water heat pump with minimal costs, maintaining and even improving the global performance of the system. The newly made heat pump was tested at variable regimes in the Cogeneration Trigeneration Laboratory of the Faculty of Mechanical Engineering of Iasi. The external unit was inserted into a climatic chamber capable of simulating variable climatic conditions for any region in Europe. Later, the same heat pump was tested in real operating conditions, being inserted in the heating circuit of a medium-sized house in the Iasi area. Its operation was then monitored during an entire winter season, being instrumented to measure the energetic balance and determine the coefficient of performance (COP) continuously throughout the season, in accordance with the weather conditions and also to measure the seasonal coefficient of performance (SCOP).

Comparative analysis of the energy performance of an air handling unit with two-stage heat recovery operating in the different climatic zones of Bulgaria

A comparative analysis was carried out to establish the energy performance of an air handling unit (AHU) for two-stage heat recovery of the exhaust air. The seasonal coefficient of performance (SCOP) was calculated when AHU is operating in heating mode, as well as COP for the entire unit on an annual basis, taking into account the specific features of the different climatic zones in the Republic of Bulgaria. The results have been compared with the BIN-temperature data for an average climate provided in EN 14825 (Table 37) in order to find out how far this standard will give reliable results for the Bulgarian climate, both in terms of energy consumption and SCOP.

A Dynamic Heat Pump Model for Indoor Climate Control of a Broiler House

Environment control systems in broiler houses utilize non-renewable electricity and fuels as energy sources, contributing to the increase in greenhouse gases, while not providing optimal conditions. The heat pump (HP) is an energy-efficient technology that can continuously regulate the indoor temperature and relative humidity by combining different operation modes (heating, cooling, and dehumidifying). The current study presents an analytical numerical model developed in Simulink, capable of simulating the thermal loads of a broiler house and the dynamic operation of three heat pumps to cover its needs. Outdoor climatic conditions and broilers’ heat production are used as inputs, while all the heat exchange mechanisms with the external environment are considered. The study investigates the energy use and performance of each HP mode under different environmental conditions. A total of 7 different production periods (PPs) are simulated for a 10,000-broiler house in northern Greece, showing total energy consumption of 18.5 kWh/m2, 43.4 kWh/m2, and 58.7 kWh/m2 for heating, cooling, and dehumidifying, respectively. The seasonal coefficient of performance (SCOP) reaches above 3.1 and 4.8 for heating and dehumidifying, respectively, while the seasonal energy efficiency ratio (SEER) for cooling is above 3.7. Finally, focusing on the two warmer periods, a comparison between cooling with and without evaporative pads was performed, showing similar energy consumption.

Energy Evaluations of a New Plant Configuration for Solar-Assisted Heat Pumps in Cold Climates

Heat pumps in buildings allow for the limiting of CO2 emissions by exploiting directly the renewable energy available in the external environment (aerothermal, hydrothermal and geothermal sources). Moreover, other renewable technologies such as active solar systems can be integrated easily into use with them. This combination not only increases the share of primary energy provided by renewable sources for heating/cooling but also improves the heat pump performance indices. Nevertheless, in cold climates, air–water heat pumps should be equally penalized due to the unfavorable outdoor air temperature. Conversely, a water–water heat pump, connected with a solar tank and thermal solar collectors, overcomes this issue. Indeed, the higher temperature attainable in the cold source allows for reaching greater COPs, and when the solar tank temperature level is enough, emitters can be directly supplied, avoiding the absorption of electric energy. In this paper, this plant configuration, in which a further tank after the heat pump was considered to manage the produced thermal energy, is investigated. Proper control strategies have been developed to increase the renewable share. Regarding a reference residential building located in Milan, for which the water–water heat pump was sized properly, a parametric study, carried out in TRNSYS by varying solar tank volume and collecting surface, has allowed for the identification of the optimal system configuration. A renewable share, ranging between 54% and 61% as a function of the collecting surface and the storage volume, was detected, as was an average seasonal coefficient of performance (SCOP) over 4. Regarding two common heating plant configurations using an assisted PV air-to-water heat pump and a gas boiler, the optimal solution allows for the limiting of CO2 emissions by 33% and 53%, respectively.

Investigation of the Interactions between Refrigerant, Flowsheet, and Compressor in Residential Heat Pumps

The refrigerant used in heat pumps significantly influences the overall system performance. However, selecting a proper refrigerant is no trivial matter due to the heat pumps’ sensitivity to the selected flowsheet, components, and operating conditions. Herein, a holistic approach is used that covers all these interdependencies simultaneously considering the flowsheet, fluid‐dependent compressor efficiencies, and the operating point. Six low global warming potential (GWP<150) refrigerants are investigated, which include pure fluids, azeotropic mixtures, and zeotropic mixtures from different substance groups. For four flowsheets, the seasonal coefficient of performance (SCOP) by EN 14825 is calculated and serves as the assessment metric. The case study is based on typical conditions of residential heat pumps. The results show that the SCOPs substantially differ depending on the refrigerant and the flowsheet (reaching from 3.8 to 4.6). Differences in the performance of refrigerants for an equal flowsheet are mainly driven by compressor efficiency. However, these differences can be overcome by adjusting the flowsheet. In particular, when an internal heat exchanger is added, the refrigerant ranking is substantially changed. It is shown that R436A, which is inferior to R290 for the basic cycle, benefits more from an internal heat exchanger and reaches a competitive SCOP than R290.

Integration of a heating and cooling system driven by solar thermal energy and biomass for a greenhouse in Mediterranean climates

World population growth, climate change, and water scarcity will increase food vulnerability, especially in developed countries. Therefore, increasing crop productivity is one of the main challenges to be addressed in the next years. In this sense, intensive horticulture will play a key role to supply the growing demand for food. In greenhouse farming in Mediterranean climates the passive control of the greenhouse ambient conditions is insufficient and, therefore, the use of active heating/cooling systems is required.The status of solar thermal, biomass, and absorption heat pump technologies makes the active management of greenhouse climate conditions technically feasible. At the same time, the utilization of solar thermal and biomass energies allows reducing, as much as possible, the consumption of natural resources and the generation of waste.In this study, we present a system based on solar thermal energy, biomass, and an air-cooled absorption chiller that are integrated to control the temperature of a greenhouse for tomato production in Mediterranean climates. The greenhouse thermal demand is firstly modelled with the TRNBuild tool and validated with real data obtained from a monitored greenhouse in southern Spain. The validated model is used to both study the system operation and determines the annual heating and cooling demands of a greenhouse with tomato crop (26.31 kW·h·m−2, and 61.97 kW·h·m−2, respectively), the energy performance of the system (solar fraction 54.92 %, and absorption chiller seasonal COP 0.624), and the annual biomass operational cost (2.70 €·m−2). This study also provides the specification of the main components (absorption chiller capacity, solar collector technology, absorbance area, biomass boiler thermal capacity, and water tank volume…) that can achieve these results. Moreover, the control for different typical days is shown.

Multi-objective optimization of a photovoltaic thermal curtain wall assisted dual-source heat pump system

To address the limitations of single renewable energy applications in cold regions, a novel photovoltaic thermal curtain wall assisted dual-source (air and ground source) heat pump system is proposed. The performance of the system was investigated using numerical simulations and experimental tests. Furthermore, a multi-objective optimization based on the non-dominated sorting genetic algorithm was employed to achieve the optimal design of the hybrid renewable system for a nearly zero-energy building in Shenyang, China. The energy consumption, life cycle cost, and photovoltaic power generation of the system were considered as objective functions. A sensitivity analysis was performed to study the effect of the design variables on the objective functions. The results showed that the seasonal coefficient of performance (COP) of the unit and the proposed system were 3.30 and 2.80, which are increases of 6 % and 5 %, respectively, compared with the dual-source heat pump system. According to the Pareto front obtained, life cycle cost is negatively correlated with energy consumption and positively correlated with photovoltaic power generation. When the area of the photovoltaic thermal curtain wall increased from 0 to 15 m2, the energy consumption and life cycle cost were reduced by 253 kWh and 1118 CNY, respectively.

Study on performance of Vuilleumier cycle heat pump for residential heating

Vuilleumier cycle heat pump (VHP) is a thermally driven heat pump and has huge potential for improving energy efficiency in residential heating. In this paper, performance of VHP is studied based on SAGE software. The errors between the experiment and simulation are in the range of −4.6 %∼4.5 % and −18.2 %∼7.4 % respectively for COPh and heating capacity. Based on developed model validated by experimental results, available energy losses (AEloss) are obtained and analyzed. Hot regenerator is the main component for AEloss and incomplete heat transfer is the main contribution for AEloss. Then, the effects of parameters on the performance are studied. And parameters are optimized. The results show that the improvement of COPh could be up to 3.6 %. Moreover, the performance and seasonal energy efficiency ratio of VHP in the cold region are carried out. The results show that seasonal COP could be up to 1.53 at −0.26 °C average ambient temperature.