Energy Consumption Of Heat Pump Research Articles

Development of a high-resolution top-down model to estimate actual household-level heat pump electricity consumption

Heat pumps can play an important part in decarbonizing the residential sector due to their use of electricity instead of fossil fuels, and their high efficiency, which often exceeds 100%. However, heat pump performance and energy savings vary with climate and individual household energy usage. Recent studies have used geospatial models to estimate potential heat pump energy consumption across the United States. Yet most studies use generic and oversimplified heat pump models. We contribute to this field with a geospatial model based on manufacturer data and measured test data for 16 different R410A, high efficiency, variable speed compressor heat pumps. Using linear regression, we estimate a market average of COP with respect to ambient temperature. From this, we can identify the variation in efficiency with temperature across this technology class. We also use linear regression to estimate demand for heating and cooling as a function of ambient temperature and household characteristics. We compare the performance of both the predicted energy demand and heat pump efficiency against measured data from a heat pump-equipped house in West Lafayette, Indiana, and find that the model predicts daily heat pump electricity consumption with 27.8% relative error, comparable to other building simulation models. By incorporating high-resolution geospatial data inputs, such top-down models can still maintain a large scope across technologies and diverse climates while increasing spatial and temporal resolution.

Reducing energy consumption of heat pumps by introducing a thermal energy storage system

We proposed a short-term thermal energy storage system by applying Phase Change Materials (PCMs) in air ducts connected to an indoor air conditioning unit within a ceiling space. PCM tubes were arranged in a staggered layout in the air duct and cooled by chilled air from the air conditioning unit during “charging” mode, whereas the PCM tubes released cold energy to the room space without operation of the compressor during “discharging” mode. The charging mode allowed for an increase in the partial load ratio of the heat pump to prevent low-efficiency operation at <20% load, which can increase seasonal energy efficiency. We constructed an energy simulation program, where the heat exchange coefficient between the PCM tubes and air was varied with airflow rate and the temperature difference between the PCM and air, in accordance with results from CFD analysis. Switching between the charging and discharging modes was based on the outlet temperature (Tout) and 30% of the rated capacity of the indoor unit (Lr). The heat balance between the charging and discharging modes was improved by this change to the system control. A higher load factor and higher COP resulted in a 7.6% reduction in energy consumption.

Probabilistic Flexoffers in residential heat pumps considering uncertain weather forecast

The penetration of renewable energies is increasing in energy systems worldwide. Consequently, the intermittency of the energy sources raises technical challenges for sustainable energy supply. Demand-side flexibility is an effective solution to counterbalance renewable power fluctuations. In the residential sector, electrical heat pumps exhibit great flexibility potential. In this paper, a novel approach is proposed to generate FlexOffers for individual heat pumps considering the uncertain nature of weather conditions. To achieve the aim, firstly, the thermal dynamic model of residential buildings is presented mathematically. The model addresses different temperature zones. The constant coefficients of the thermal dynamics are estimated using Continuous-Time Stochastic Model (CTSM) in R software. Afterward, the building model is integrated with a success function to generate FlexOffers. The success function is comprised of two objective functions including minimization and maximization of the energy consumption of heat pumps. The FlexOffers are generated considering the existing gap between the minimum and maximum energy consumption. The patterns of energy consumption are defined based on occupants’ thermal comfort temperature setpoint. The FlexOffers are programmed in UPPAAL-STRATEGO software. Finally, a high-fidelity building model with four rooms is used to examine the proficiency of the suggested approaches. The simulation results confirm that the proposed method generates flexibility potentials for the upstream network in both optimistic and pessimistic states of energy consumption patterns.

Construction of Regional Cooling and Heating Source Air Conditioning System Based on Ocean Thermal Energy and Energy Consumption Analysis

Zhao, S.; Yan, P.; Zhao, C., and Chang, H., 2019. Construction of regional cooling and heating source air conditioning system based on ocean thermal energy and energy consumption analysis. In: Li, L.; Wan, X., and Huang, X. (eds.), Recent Developments in Practices and Research on Coastal Regions: Transportation, Environment and Economy. Journal of Coastal Research, Special Issue No. 98, pp. 22–25. Coconut Creek (Florida), ISSN 0749-0208.The ocean contains a huge amount of ocean thermal energy (OTE). The cooling and heating source heat-pump air conditioning system based on OTE collects thermal energy from seawater; then with the aid of the compressor system and a small amount of electricity consumption, it can heat or cool the buildings within the region. By conducting exergy analysis on the system and comparing it with the energy consumption of the air source heat-pump system, it shows that in case of equal heating and cooling supply, the heat-pump energy consumption and system energy consumption of the regional cooling and heating source air conditioning system based on OTE are significantly lower than those of the air source heat-pump system, and it can save about 25% of the energy.

Analysis of Air-Conditioning Radiator Based on Thermal Environment Characteristics of Buildings

The heating method based on coal-burning in residential buildings in northern China is seriously polluted and consumes a lot of energy. The "coal-to-electricity" heating using heat pump technology is an energy-saving and emission-reduction measure being implemented by the state. Based on the thermal environment characteristics of the building and the performance characteristics of the heat pump, this paper optimizes the layout of the air conditioner, and numerically simulates the system to analyze the thermal load of the building and the heat pump energy consumption with the outdoor climate. The results show that the wall air-conditioning radiant panels arranged near the outer wall can effectively reduce the heat supply temperature of the heat pump while effectively improving the indoor thermal comfort. The increase of the heat load of the building can reduce the actual heat pump power consumption by the increase of the heat pump COP.

Characterization, testing, and optimization of load aggregation methods for ground heat exchanger response-factor models

Ground heat exchangers (GHEs) are often simulated using response factor-type models that rely on the GHE load history. As the simulation progresses, the number of GHE load history terms that need to be included in the temperature response computation grows. For extended, multiyear simulations the required computation time due to these history terms can be excessive, which limits the usefulness of response factor-type models. To cope with this, load aggregation procedures have been developed that preserve the net effect the individual loads but reduce the overall number of computations. The previously developed load aggregation methods can be characterized as two different methods, but with different parameters. The parameters each affect the accuracy and computational efficiency of the methods, yet there has been no systematic investigation of the parameter space. In this article, both methods are implemented and compared for a wide range of parameters. A final recommendation is made that results in a 73-fold reduction in simulation time when compared to nonaggregated simulations. For a worst-case situation with an imbalanced load profile on a densely packed borehole field, the MBE is less than 0.13 °C for 5- and 10-year simulations. The resulting predicted heat pump energy consumption error is less than 0.3%.

Primary energy consumption of heat pumps in high renewable share electricity mixes

The increase of power plants’ conversion efficiencies, together with the high share of renewable energy sources in the electricity production for some countries, pushes for the use of heat pumps for space heating when aiming at reducing the associated primary energy consumption. However, the effective reduction of primary energy consumption should be supported by careful evaluations, as a number of parameters influence the heat pumps performance, including outdoor temperature, supply temperature, heat load and electricity primary energy factor. The variability of such parameters increases the complexity of the analysis, and annual or monthly average calculations might lead to incomplete evaluations and thus to sub-optimal solutions. This paper performs a hourly simulation of the operation of an air-source heat pump for space heating, relying on the available heat demand data of real buildings currently connected to a district heating network. In addition, the paper proposes the calculation of the hourly primary energy factor of the electricity supplied by the power grid, as the variability of the generation sources plays a key role in the global analysis of the energy system’s conversion efficiency. The results show that in all the considered cases the heat pumps provide potential primary energy savings compared to natural gas boilers, thanks to the combined effect of their high coefficient of performance and the low electricity primary energy factor in the analyzed context. The primary energy consumption reduction obtained in each case is in the range 10–40%, with a median value close to 30%. Moreover, the comparison between average and high-resolution calculations of primary energy factors shows the possible underestimation of the potential primary energy savings when yearly or monthly data are adopted.

Integrated model for comparison of one- and two-pipe ground-coupled heat pump network configurations

Several network configurations are possible when designing the interior portion of centralized ground-coupled heat pump systems. In this study, three different configurations are examined: Two-pipe networks with either a direct-return or a reverse-return and one-pipe systems. One-pipe networks typically require less piping than two-pipe systems. However, heat pump energy consumption might be higher because the inlet temperature to the heat pumps tends to increase (in cooling) or decrease (in heating) along the network. In the current study, a versatile integrated modeling tool is developed in the TRNSYS environment to study the energy consumption (pumps and heat pumps) of each type of network. A control method for one-pipe systems, based on the bore field return temperature, is also proposed. The tool is first compared to detailed individual models in annual simulations where it is shown to give good results. The results obtained with four different case studies indicate that the total annual energy consumption of one-pipe networks is up to 5% higher than two-pipe networks even though the pumping energy is 4% to 53% lower than two-pipe networks. No significant differences are observed in the required borehole length.

Optimization on the performance of ground heat exchangers for GSHP using Kriging model based on MOGA

A multi-objective genetic algorithm (MOGA) combined with Kriging response surface method was proposed to optimize the design parameters of the ground heat exchanger (GHE) for ground source heat pump (GSHP). The effect of design parameters, including inlet flow velocity, inlet flow temperature, U-tube diameter, borehole diameter and pipe spacing on the entropy generation number (EGN) and the integrated evaluation factor were analyzed, respectively. Furthermore, the optimization results using MOGA approach and Screening approach were compared. Finally, the multi-objective design optimization was carried on GHEs and the results were verified in the GSHP system simulation platform using TRNSYS software. The results illustrated that both the MOGA optimization approach and the Screening approach using the Kriging model could improve the thermal performance of GHEs. Furthermore, the thermal performance of optimal results in the MOGA approach was superior to that in the Screening approach. Compared with the original GHE, the average energy consumption of heat pump of the optimal GHE in the MOGA approach decreased by 215.86kJ·h-1, while that in the Screening approach declined by 133.64kJ·h-1 .

Prediction of residential building energy consumption: A neural network approach

Some of the challenges to predict energy utilization has gained recognition in the residential sector due to the significant energy consumption in recent decades. However, the modeling of residential building energy consumption is still underdeveloped for optimal and robust solutions while this research area has become of greater relevance with significant advances in computation and simulation. Such advances include the advent of artificial intelligence research in statistical model development. Artificial neural network has emerged as a key method to address the issue of nonlinearity of building energy data and the robust calculation of large and dynamic data. The development and validation of such models on one of the TxAIRE Research houses has been demonstrated in this paper. The TxAIRE houses have been designed to serve as realistic test facilities for demonstrating new technologies. The input variables used from the house data include number of days, outdoor temperature and solar radiation while the output variables are house and heat pump energy consumption. The models based on Levenberg-Marquardt and OWO-Newton algorithms had promising results of coefficients of determination within 0.87–0.91, which is comparable to prior literature. Further work will be explored to develop a robust model for residential building application.

An assessment of efficient water heating options for an all-electric single family residence in a mixed-humid climate

An evaluation of a variety of efficient water heating strategies for an all-electric single family home located in a mixed-humid climate is conducted using numerical modeling. The strategies considered include various combinations of solar thermal, heat pump, and electric resistance water heaters. The numerical model used in the study is first validated against a year of field data obtained on a dual-tank system with a solar thermal preheat tank feeding a heat pump water heater that serves as a backup. Modeling results show that this configuration is the most efficient of the systems studied over the course of a year, with a system coefficient of performance (COPsys) of 2.87. The heat pump water heater alone results in a COPsys of 1.9, while the baseline resistance water heater has a COPsys of 0.95. Impacts on space conditioning are also investigated by considering the extra energy consumption required of the air source heat pump to remove or add heat from the conditioned space by the water heating system. A modified COPsys that incorporates the heat pump energy consumption shows a significant drop in efficiency for the dual tank configuration since the heat pump water heater draws the most heat from the space in the heating season while the high temperatures in the solar storage tank during the cooling season result in an added heat load to the space. Despite this degradation in the COPsys, the combination of the solar thermal preheat tank and the heat pump water heater is the most efficient option even when considering the impacts on space conditioning.

Using renewable energy to create comfort in the first Romanian passive house suited for offices

Using renewable energy is becoming more profitable nowadays because of applying advanced technology. The paper, presented by the authors, analyses the case of using solar and geothermal energy to create comfort in homes with low energy consumption. In this situation, the performance of the systems that take energy from low-heat renewable sources and convert it into useful energy is growing. The characteristics of the buildings with low power consumption, of passive houses in particular, can cause the development of a new generation of devices to create comfort. The energy used to create comfort in the first passive house built in Romania, which was designed for offices, analyzed by the authors, is using both geothermal and solar power. The authors present the energy performance of the building correlated with the performance of the air-conditioning system that uses ground-water heat pumps. The thermodynamic analysis presented, highlights how the performance of geothermal energy systems increased, their variation depending on the climate zone variation parameter values. The authors make a detailed analysis, in the presented paper, about the influence of the working conditions of the installation elements, on the heat pump energy consumption and the methods adopted to reduce losses and increase system performance.

Thermodynamic evaluation of the possibility to increase cogeneration turbine efficiency by using a heat pump operating with steam

Cogeneration turbines operate in different operation modes that considerably differ as to the working process conditions. In summer time, when heat demand is minimal, almost all steam flow passes through all turbine stages and enters into the condenser (condensing mode of operation). When heat supply is needed, the steam bleed-offs are used. The several last stages of the turbine (low-pressure part—LPP) have a control diaphragm at the inlet. When the heat supply is large, the diaphragm is maximally closed, and the entire steam flow, with an exception for a minimal ventilation flow is delivered to the steam bleed-offs (cogeneration mode). LPP flow path is designed for the optimal operation in the condensing mode. While running in cogeneration mode, the LPP operating conditions are far from optimal. Depending on the ventilation steam flow rate and outlet pressure, the LPP power can drop to zero or even become negative (ventilation mode). It is proposed to control an outlet steam pressure by using the heat pump that operates with steam. The heat pump energy consumption can be compensated and even exceeded by optimizing the steam expansion process in LPP. In this respect, operating conditions of cogeneration turbine LPPs during the cold season are analyzed. A brief description of a heat pump operating with steam is made. The possibility of increasing cogeneration turbine efficiency by using a steam heat pump is shown.

Primary-secondary de-coupled ground source heat pump systems coefficient of performance optimization through entering water temperature control

A control technique to optimize an existing de-coupled primary-secondary ground source heat pump (GSHP) loop system using site data is presented. The proposed control algorithm improves system performance by optimizing the primary loop pump's flow of well water into the secondary loop to deliver more favorable water temperatures to downstream heat pumps. Improvements are presented on a specific installation using 15-minute interval data collected from a building automation system (BAS) for a period of one year. Energy savings are calculated to demonstrate the benefits of improved heat transfer by modulating the building heat pumps condenser/evaporator entering water temperatures to improve COP. The specifics of how to implement this control scheme with an existing de-coupled GSHP system are provided. By monitoring the building HVAC operations, and optimizing the entering secondary loop water temperature, a 3% decrease in annual heat pump energy consumption is achieved.

A quasi-transient model of a transcritical carbon dioxide direct-expansion ground source heat pump for space and water heating

In this study, a theoretical quasi-transient model is developed for detailed simulations of a carbon dioxide (CO2) direct-expansion ground source heat pump (DX-GSHP). This model combines a transient analytical model for the ground, steady-state numerical models for the borehole and the gas cooler, as well as several thermodynamic models for the remaining components of a conventional heat pump, organized in interacting subroutines to form a powerful simulation tool. Extensive validation combining experimental data and CFD-generated results was performed for the borehole before the tool was used to simulate a practical application case.Performance is investigated for a system satisfying both space heating and domestic hot water requirements of a typical single family detached home in a cold climate region. The variation of different system parameters is also evaluated in this study. It is shown that CO2 DX-GSHPs can offer relatively efficient and stable performance for integrated water and space heating applications. Furthermore, the importance of an accurate geothermal borehole sizing is highlighted for the DX-CO2 heat pump systems. It is shown that, due to changes in the system working conditions, the total borehole length is not linearly correlated with the heat pump energy consumption and other parameters such as heat pump coefficient of performance and pressure drop in ground heat exchangers. Results showed that increasing the total borehole length of an optimum design (reference case study) by 25% decreases the total annual energy consumption by only 6%. However, reducing total borehole length of the reference case by 25% increases the total annual energy consumption by 10%.

Simulation Modelling and Design Optimization of Vertical Ground Heat Exchanger-GEOSTAR Program

This paper presents the analytical heat transfer models for the vertical ground heat exchangers (GHEs) and the attendant program named “GEOSTAR” developed for use in design and simulation of vertical GHEs. The program used spatial superposition for multiple boreholes and sequential temporal superposition principles to account for time-varying loads. Coupled with the models of the heat pump and building loads, the GEOSTAR can predict time-varying heat pump energy consumption, heat transfer rates of GHEs, and other variables of interest. Finally, the program is applied to design an existing GCHP project and to simulate the system performance. The results demonstrate the usefulness of the simulation model and attendant program as a tool for designing GCHP systems.

Simulation and Analysis of Air-soil Dual Source Heat Pump Energy Consumption in Cold Regions

INTRODUCTIONThis paper mainly researches the practical engineering about Simulation of air-soil heat pump system in an office building of Shenyang, China. This system in the winter uses the air source as the main heat source and soil source as the auxiliary heat source for heating, in the summer only uses the soil source heat pump to refrigerate. METHODSThis paper mainly applies DEST software and TRNSYS software to study engineering air simulated analysis of soil heat pump system and compare with a single heat source. Analyzing the energy consumption of the dual heat sources pump system and its results were compared with the single soil source heat pump system to draw a conclusion. RESULTSAnalysis of energy consumption of dual-source heat pump system in summer and winter. And energy consumption analysis of single soil source heat pump system in summer and winter. CONCLUSIONSIn terms of energy consumption, the annual energy consumption of dual heat source heat pump system is 25962.23 kWh. The annual energy consumption of single soil source heat pump system is 45573.78 kWh, saving about 43.03% of energy consumption. The superiority and development prospects of the dual heat source heat pump system is obvious and promising, in the operating cost and conservation area. This project was financially supported by the National science and technology support plan sub-topic (2011BAJ05B01-04).

Energy and climate simulations and management system in the Szentágothai research center

The Szentagothai Janos Research Center in Pecs brings computer based building physics simulations to reality closer than ever. This high class building ads ground to several medical research programs and lectures, but it also gives a rare opportunity to improve computer simulations with its’ Building Management System (BMS from now on). The system does not only allow the complex building services system to be remotely controlled from a single computer, but also gathers important data related to the buildings’ physical performance, for example: room temperatures; air flow rates; geothermal pipe performance; and energy consumption of heat pumps. By comparing the results of a zone based building physics simulation model of the building, enhancement of the precision of the simulations and optimization of the actual buildings energy consumption can be done, by trying out different maintenance strategies.The first step is to build the computer model to be as precise as possible. In the zone based physical model...

Coupling of geothermal heat pumps with thermal solar collectors using double U-tube boreholes with two independent circuits

Abstract This study presents an analytical model to predict steady-state heat transfer in double U-tube boreholes with two independent circuits operating with unequal mass flow rates and inlet temperatures. The model predicts the fluid temperature profiles in both circuits along the borehole depth. It accounts for fluid and pipe thermal resistance and thermal interaction among U-tube circuits. The proposed model is used to study a novel double U-tube borehole configuration with one circuit linked to a ground-source heat pump operating in heating mode and the other to thermal solar collectors. The performance of this configuration is compared to a conventional ground-source heat pump system (without thermal recharge of the borehole) and to a single-circuit solar assisted ground-source heat pump system. All three systems are simulated over a 20-year period for a residential-type single-borehole configuration. Results indicate that winter solar recharging, either for the proposed configuration or the solar assisted ground-source heat pump system, reduces by 194 and 168% the amount of energy extracted from the ground by the heat pump. It is also shown that, for a ground thermal conductivity of 1.5 W m −1 K −1 , the borehole length can be reduced by up to 17.6%, and 33.1% when the proposed configuration or the solar assisted ground-source heat pump system are used. The impact on the annual heat pump energy consumption is less dramatic with corresponding reductions of 3.5% and 6.5%.

Fault diagnosis for heat pumps with parameter identification and clustering

For reducing the energy consumption of heat pumps, fault detection and diagnosis (FDD) is fundamental. The FDD system presented is based on a gray-box process model, the parameters of which are identified online. The faults are classified from the parameters using clustering methods. Known clustering techniques have been simplified and new “vector clustering” techniques have been developed for classifying gradual faults. The FDD system has been tested in various real applications, for one of which the results are presented in this work. The contribution lies on the application side with a software tool developed for the fully automated training process.