Heat Pump Installation Research Articles

Using reinforcement learning for maximizing residential self-consumption – Results from a field test

This paper presents the results from a real residential field test in which one of the objectives was to maximize the instantaneous self-consumption of the local photovoltaic production. The field test was part of the REnnovates project and was conducted in different phases on houses in several residential districts located in Soesterberg, Heerhugowaard, Woerden and Soest, the Netherlands. To maximize self-consumption, buffered heat pump installations for domestic hot water and stationary residential battery systems were chosen due to their respective thermal and electrical storage capacities. The algorithm used to tackle the associated sequential decision-making problem was model-based reinforcement learning. The proposed algorithm learns the stochastic occupant behavior, uses predictions of local photovoltaic production and considers the dynamics of the system. The results show that this algorithm increased the average self-consumption percentage of the local PV generation (used instantaneously in situ) on average by 14%, even if only buffered heat pump installations for domestic hot water were used. This increase was achieved without causing any perceived discomfort to the residential end users. The average energy shifted per day from the solar production period to the night by the 2 kW/3.6 kWh batteries was 1.5 kWh. The main contribution of this work was therefore the real field implementation of the proposed algorithm. The results demonstrate that it is possible to improve even further the integration of local production using flexible loads.

The use of heat pump installations as part of waste energy convertion complexes in the joint generation of electrical and thermal energy

The possibility of using heat pump installations at thermal power plants is considered. An estimation of the sources of low-potential heat for the operation of the heat pump in the joint generation of electrical and thermal energy was carried out. The results of a comparative analysis of the schemes for the inclusion of a heat pump in the cooling system of recycled water are presented using the example of the Kirov thermal power plant.

Comparative analysis of heat supply options for small and middle-sized settlements of Eastern Siberia by using uncertain and fuzzy information

The problems of heat supply in small and medium-sized settlements of Eastern Siberia are considered. Variants of using cogeneration heat plant (CHP) or boiler plant on coal or wood waste, the use of liquid petroleum gas (LPG) and liquid natural gas (LNG) as a fuel, the use of electric boiler plant or stand-alone electric boilers, applications of solar collectors and heat pump installations are considered based on a systems approach and fuzzy modelling, by taking into account the uncertainty of some factors.

Thermodynamic modeling of a heat pump unit as part of a cogeneration turbine operating in ventilation mode

Currently, much attention is paid to improving the efficiency of energy generating facilities through the use of secondary energy resources. This article presented a cogeneration turbine in the general energy scheme with a heat pump installation. During the winter period, due to the increased consumption of heat energy, heat-generating turbines, by closing the regulating diaphragm, are switched to full steam extraction mode from the low-pressure flow part to heat the supply water. In this case, the last stages of the turbine are transferred to the ventilation mode with the release of heat due to the vortex flows on the blades of the low pressure part. In order to obtain additional heat energy for network water, the article considers the option of using secondary energy resources with the help of a heat pump unit operating in a steam turbine plant scheme. All necessary calculations of thermodynamic modeling were carried out according to the EES heat pump, the program working as part of a cogeneration turbine, and the results were obtained of increasing the efficiency of using secondary energy resources with various refrigerants.

A novel TRNSYS type of a coaxial borehole heat exchanger for both short and mid term simulations: B2G model

A dynamic model of a ground source heat pump system is a very useful tool in order to optimize its design and operation. In order to fairly predict the performance of such a system, the dynamic evolution of the fluid entering the heat pump and coming from the borehole heat exchanger (BHE) must be accurately reproduced not only in the long term but also in the short-mid term operating conditions, as it directly affects the coefficient of performance of the heat pump unit.In this context, the B2G model was developed to reproduce the short-term dynamic evolution of the fluid temperature inside the BHE. This work presents the new upgraded version of the B2G dynamic model for a coaxial BHE, which includes several new features to better reproduce not only the short-term but also the mid-term behaviour of the BHE. For that purpose, the model of the surrounding ground has been improved: vertical heat conduction in the grout and ground, heterogenous ground with different layers, and a higher number of ground nodes in the thermal network considered in the model were added, which are automatically located by means of polynomial correlations for any type of ground, geometry and operating conditions. This novel approach has been implemented in TRNSYS for accurately modelling the dynamic behaviour of a coaxial BHE with low computational cost (2.5 s for a 24 h simulation period in a modern computer).The model has been validated against experimental data from a dual source heat pump installation in Tribano (Padua, Italy) and has proven capable of accurately reproducing the short-mid term (up to five days) behaviour of the BHE, with a deviation lower than 0.12 K.

Sizing domestic air-source heat pump systems with thermal storage under varying electrical load shifting strategies

The demand for local heat storage to help manage energy demand in dwellings is likely to increase as the electrification of heat through heat pumps becomes more widespread. Sizing thermal energy storage systems has been an important topic in contemporary literature, but the effect of the electrical load shifting tariff and the service the householder receives in terms of space-heating and hot water delivered, however, has not and this is particularly important when households transition from conventional gas fired to low carbon technologies. This paper takes a whole system modelling approach to understand the impact of user demand patterns and load shifting scenarios on the volume of energy storage required for a heat-pump installation. The work uses monitoring data from several family homes to drive the simulation and finds that the level of service the householder receives is sensitive to their patterns of consumption, thermal energy storage volume and the electricity tariff, with some households being far more sensitive to tariff choice than others. The paper introduces a novel, quantifiable measure of service for space-heating and hot water systems that can be incorporated into thermal energy storage sizing procedures.

Passive Cooling in the System of a Heat Pump with a Vertical Ground Collector

Heat pumps from more than ten years are known as an alternative source of thermal energy. They are primarily used for central heating and domestic hot water preparation. Next to the solar collectors, they are the cheapest and easiest way to save energy. But heat pump can also be used for cooling. Heat can spontaneously flow from a colder to a hotter body. Flows from a body with a higher temperature to a body with a lower temperature are commonly known as the second law of thermodynamics. The heat pump pulled out of cooler ambient heat which may be used for central heating or for domestic hot water. There are many types of cooling pumps. This depends mainly on the type of pump, and actually kind of heat source that can be used in two ways: as a heat receiving surface - or as a source of cooling for utilization. Knowing the general principle of operation of the pump, we can introduce innovative technologies that allow more devices to reduce the operating costs. In this solution, the heat pump installation, initially designed only for heating or, ultimately, also for cooling purposes, enables the use of a system that will be based on the part of the installation associated with the lower heat source, but not as a source of heat but as a source of coolness. This system is often referred to as “natural cooling” or as a passive cooling system. In such a system, during the production of chilled water, a significant reduction in production costs is obtained due to the lack of energy consumption for the drive of refrigeration compressors, and only the use of circulation pumps for the lower and upper circulation of the heat source. The disadvantage of this solution is the limitation resulting from the situation of close connections between ground temperature and chilled water temperature in the supply, which causes the limitation of its use for the period beyond the maximum peak demand for cold in the cooling season, i.e. most often at the highest outside temperatures. Thanks to the economical use of electricity, we can contribute to protect the environment.

Numerical Modelling of Heat Transfer in Convector’s Pipes by ABAQUS

The paper presents method for implementation of numerical modelling of heat transfer process between the water flow and the internal surface of a “water-air” convector’s pipes. The convector is a heat consumer in a reversible heat pump installation. To implement the CFD simulations, which are part of the numerical modelling of the processes, the ABAQUS software has been used. The main features and results from the simulations have been analysed. The method includes experimental investigations aiming determination of the boundary conditions for CFD simulation. The distribution of temperature, pressure and velocity in the fluid flowing through the pipe have been investigated. The results of the investigation of the temperature distribution present reduced heat transfer intensity in pipe’s sections, characterized by higher local hydraulic resistances.

Improving a water treatment and a heating performance of the water-to-water heat pump: misallocation and available solutions1The Authors thank the Government of the Russian Federation for its financial support of the Decree No. 860 August, 29 2017

The object of our experimental investigation is a heat pump system operating at low temperatures of a low-grade heat source. The purpose of experimental research of the heat pump installation is to increase the efficiency and reliability of heat pump unit by adjusting compressor performance. To carry out the experiment we connected the reciprocating compressor with Variable Frequency Drive of AC 0..650 Hz, designed for rated capacity of 2.2 kW, as well as electricity meter. The dependence of heat load of pump condenser on the speed (rpm) is approximated by the formula and will be used to design a heat pump unit. The proposed experimental unit allowed us to determine the correlation between basic characteristics and the compressor shaft speed and determine the possible range of its regulation (50..180%). The obtained results allow us to design the water treatment plant with using heat pump unit with quality regulation systems as well.

A Fault Detection System for a Geothermal Heat Exchanger Sensor Based on Intelligent Techniques.

This paper proposes a methodology for dealing with an issue of crucial practical importance in real engineering systems such as fault detection and recovery of a sensor. The main goal is to define a strategy to identify a malfunctioning sensor and to establish the correct measurement value in those cases. As study case, we use the data collected from a geothermal heat exchanger installed as part of the heat pump installation in a bioclimatic house. The sensor behaviour is modeled by using six different machine learning techniques: Random decision forests, gradient boosting, extremely randomized trees, adaptive boosting, k-nearest neighbors, and shallow neural networks. The achieved results suggest that this methodology is a very satisfactory solution for this kind of systems.

INDICATORS OF THE EFFICIENCY OF COGENERATION HEAT PUMP INSTALLATION IN THE THERMAL SCHEME OF HEATING BOILER HOUSE

The study analyzes the indicators of the efficiency of cogeneration heat pump installation (CHPI) in the thermal scheme of heating boiler house. It is determined that the application of CHPI in the thermal scheme of heating boiler house will provide high

Assessment of three types of shallow geothermal resources and ground-source heat-pump applications in provincial capitals in the Yangtze River Basin, China

The evaluation of geothermal resources and ground-source heat-pump systems has been performed for a wide variety of individual buildings and cities. However, the assessment of ground-source heat-pump systems for multiple cities with different climatic and ground conditions has rarely been performed. The feasibility of ground-source heat-pump installation strongly depends on the local climatic, geological and geothermal conditions. This paper first investigates the shallow geothermal resources, including the thermal resources of open reservoirs (lakes and rivers, surface water), underground aquifers and geological materials. Then, the potential for ground-source heat-pump system applications in eleven provincial capitals in the Yangtze River Basin in China is assessed. The Yangtze River Basin covers a wide range of territory with dramatically different climates and geological conditions. The potential of ground-source heat-pump systems is evaluated by modeling the energy consumption of a certain conventional building with defined thermal and geometric characteristics under various climatic conditions. The results indicate that three ground-source heat-pump systems, namely, surface-water heat pumps, groundwater-source heat pumps and ground-coupled heat pumps, show different potentials among the investigated cities. The findings from this study are meant to optimize the high capital costs of ground-source heat-pump systems in the study area.

Predicting the thermal behaviour of sands considering its moisture content and grain size with applications to geothermal heat pump installations

Space conditioning has one of the highest end-use service demands in the building sector. To avoid negative effects on the energy system and the environment, efficient energy sources and technologies must be implemented to provide future heating and cooling requirements. Geothermal heat pump systems (GHPS) are one of the technologies with highest thermodynamic and cost performance; nevertheless, its performance highly depends on local geological characteristics. In this study, a thermodynamic assessment of different types of sands, that could potentially be used as energy sources for GHPS in dry regions, has been conducted. The experiment focuses on understanding the thermal behaviour of five dry sand samples with different standard sieve sizes according to ASTM designations (Nos. 50, 45, 30, 16, and 14) and moisture content capacities. Based on the obtained data, a mathematical model to predict sand temperatures has been derived considering grain size, shape and moisture content. Compared to previous models, our results show that the developed model computed more accurate approximations compared to actual temperatures, providing a robust thermal behaviour model of dry regions’ sands that could be used in building simulation tools more effectively.

Conditions for shallow geothermal energy utilization in Dinaric karst terrains in Croatia

Hydrogeological and thermogeological properties of the shallow subsurface in the Dinaric karst area of Croatia were investigated in the context of its utilization for ground- and water-source heat pumps (GSHPs and WSHPs). The research encompassed four 100 m deep boreholes with GSHP installations in both coastal and inland Dinaric karst (different limestones and evaporitic rocks at one location), and a set of six exploratory boreholes, abstraction and reinjection wells for WSHP heating and cooling using seawater on the coast (fractured and karstified limestones). It was determined that rock thermal conductivities are favourable for GSHP utilization, but dependent on the wider rock mass characteristics which are hard to predict (size of karst voids and their saturation status). In addition, wells with high enough yield and stabile seawater or groundwater temperatures for WSHP utilization can be designed in appropriate structural settings (tensional fractures and fracture set intersections). Advantages and disadvantages of the utilized methodology have been pointed out, as well as methods which should prove useful in the future, especially if larger systems are planned. Hydrogeological, geotechnical, and thermal risks expected during the drilling, installation, and operational phases have also been identified. Presented case studies have given the insight into heat pump installation options and conditions in Croatian part of the Dinarides, but can be useful to other researchers and engineers both in the Dinarides and in similar karst regions.

Characterisation of efficiency losses in ground source heat pump systems equipped with a double parallel stage: A case study

This work focuses on methods to characterise the efficiency losses in existing ground-source heat pump (GSHP) installations under part-load conditions. Efficiency losses were identified and quantified in a GSHP by analysing key parameters measured and recorded by its monitoring system. The heating/cooling production facility comprises a vertical borehole heat exchanger field and a GSHP equipped with a double parallel stage and fixed-speed compressors within. The methodology was based on the EN-14825 standard and other recent works. However, the particularity of having two parallel stages motivated the creation of a modified theoretical approach, since the original methodology was only applicable to single-stage heat pumps. To obtain significant results, minute-resolved data acquired over time periods with almost constant thermal load (quasi-steady state conditions) proved necessary. The study concluded that the coefficient of performance can suffer reductions as high as 9% exclusively due to part-load operation. Most importantly, it demonstrated that the actual capacity of the GSHP as a whole shows an effective reduction ranging between 20% and 24% with respect to the declared capacity of the heat pump alone. Moreover, weekly-averaged data collected during 3 complete cool and warm seasons point to a progressive degradation from the date of commissioning. Finally, Ground Loop Design software (v2016) was used to validate the methodology. Consistent agreement was found between simulated and measured seasonal performance.

Система теплопостачання з використанням скидного тепла трансформатора

The task is to use the waste heat of powerful electric transformers for hot water supply in residential and industrial buildings. The high heat of transformers is of low-temperature and therefore requires heaters. The thermal scheme of the hot water supply system with electric transformer and heater - heat pump and electric heater is considered. In the scheme, the heat from the transformer is transmitted to oil, from oil to the heat in the oil-heat exchanger is transferred to water, from water to the evaporator of the heat pump installation (HPI) is transferred to the freon and from the freon to the water of the hot water system is transmitted in the condenser of the HPI. After the HPI condenser, water is heated in the electric heater and is supplied to the consumer. The thermal capacity of the transformer and the temperature of hot water supplied to the consumer are known. The temperature of the water supplied to the heater after the HPI condenser is unknown. According to the criterion of quality of variants with different water temperatures, the total cost of equipment of the scheme of hot water supply system is accepted. The method of determination of the total reduced costs of the hot water supply system with regeneration of waste heat of the transformer is offered. Costs for the hot water supply system are defined as the sum of the costs of heat exchangers, pumps and their consumed electricity, the costs of HPI and consumed electricity of its compressor, the cost of the heater and the consumption of electricity. A computer program for determining the total reduced costs of a hot water supply system with regeneration of the transformer discharge heat has been developed. The results of calculations of the total reduced costs for hot water system options are presented. The variants without HPI with heating of water in the electric heater, with heating of water in HPI and heating it in the electric heater are investigated. The HPI thermal capacities and the compressor drive electrical capacities at different water temperatures from the condensers were determined using the well-known FKW Cycle program. The comparative analysis of the obtained results is performed and it is shown that the cumulative cited costs for the variant of HPI are lower than the cumulative cited costs of the variant without HPI, that the nature of change of the cumulative reduced costs when the temperature of the heated in HPI of water is the same for a wide range of specific costs of HPI and electricity. The lowest total costs shown correspond to the lowest water heating in the HPI and, accordingly, the highest heating in the electric heater.

Applying heat pumps to utilize municipal solid waste at St. Petersburg TPP

In this article, we address an urgent problem of solid waste management. We consider the possibility of applying gasification technology for municipal solid waste disposal at existing TPPs in St. Petersburg in order to produce thermal and electric energy. St. Petersburg Northern TPP-21, facing the problem of undercooling of the circulating water in the cooling towers, is proposed as a possible placement site. Using this water as a source of low-grade heat of a heat pump installation is considered as the possible solution to the problem. The study was carried out by calculating the thermal circuits in the Boiler Designer program, and calculating the heat pump in the Cool Pack program. The efficiency of the installation is achieved by increasing the supply of thermal energy and increasing the environmental friendliness of the installation by reducing thermal pollution. We have also calculated the limits of cost-effective heat pump application.

Techno-economic analysis for the assessment of heat pump integration in a real poly-generative energy district

The present research study aims at analysing technical and economic feasible solutions for heat pumps integration in energy districts for polygeneration purpose and particularly to store excess of electricity via Power-to-heat schemes considering that, from previous researchers’ works, thermal storage has been identified as the most remunerative and easy to handle storage technology to maximise self-consumption in polygeneration grids. This technology is already developed and currently employed for conditioning of residential, commercial and industrial buildings. However, studies regarding the analysis of heat pumps’ integration in energy districts for distributed generation are still limited. The potential advantages of its employment in this context are fuel savings, a lower emission level and the possibility to couple it with local renewable energy sources (i.e. solar panels, wind turbines) and traditional generators (i.e. engines, micro gas turbines) in order to increase flexibility in operational terms. In this paper, a performance analysis of the poly-generation energy district installed at the University of Genoa Campus, located in Savona, is analysed throughout a whole year: the model is implemented using a dedicated software tool, developed by Thermochemical Power Group. Different solutions for the integration of the heat pump, including size optimization, are investigated, considering the real data related to the University of Genoa Campus: the final aim of the analysis is to determinate the best operational strategy, minimizing variable costs (i.e. fuel) and evaluating the economic feasibility of heat pump installation in the energy district. This work has been also redacted as a preliminary analysis for solar-coupled HP integration (from a optimized management point of view) to be performed in the demonstration campaign of H2020 ENVISION Project*, where both RINA Consulting and University of Genova collaborate.

국내 하천수의 수열에너지 활용 가능성 분석 : (1) 허가 기준유량 산정 및 취수 가능지역 설정

In recent years, there has been continued interest in the utilization of river discharge as a new energy source. Before this can be achieved, it is essential to examine the stability of the flow rate. In Korea, however, there are no guidelines for calculating the water availability of river water. Therefore, this paper proposes a method of estimating the water availability of river water based on the permissible standard flow rate according to the permission system of river water in Korea, and the amount of domestic river water available is estimated. In addition, the area where sufficient hydrothermal energy can be taken is analyzed considering the heat pump installation conditions of the river water. These results can be utilized as an indicator for evaluating river water hydrothermal energy as an alternative to fossil fuels and the contribution of river water to greenhouse gas reduction.

Performance analysis and experimental validation of a solar-assisted heat pump fed by photovoltaic-thermal collectors

Solar energy is called to play a relevant role in meeting the energy requirements of heating and cooling in industry and households. Its widespread use depends on the development of cost-effective and highly-efficient systems. The joint installation of heat pumps and photovoltaic/thermal (PVT) panels can greatly contribute to these targets, since solar energy provides a heat source that allows operating the evaporator of the heat pump cycle at a higher temperature than the air temperature in winter. The coefficient of performance (COP) of the heat pump therefore increases because of the reduction of the electricity expense on the compressor. Additionally, the solar system is allowed to work in a low temperature range, so the heat loss from the collector to the surrounding areas decreases, resulting in higher collector efficiencies.The solar assisted heat pump is conceived in this work as a support system to be installed in existing facilities with yearly more or less constant thermal demands being supplied by conventional boilers. This paper shows the simulation of such a system, performed in Trnsys (a flexible graphically based software used to simulate the behaviour of transient systems specialized in the solar energy field), and its experimental validation. From the collecting operating parameters (irradiance, temperature, pressure and mass flow measured on the facility) and the actual design of the system defined by the size of the solar field, the storages and the heat pump capacity, the final objective of the work is to analyse the most appropriate size of the solar field, storage (water tanks) and heating power of the heat pump for optimizing the efficiency of the system. Results show that the working cold temperature ranges from 10 to 20 °C and the seasonal COP rose to 4.62, instead of 2.96 when working between 7 and 10 °C. The 67.6% of the electricity demanded by the heat pump is provided by the photovoltaic production (9309 kWh/yr of the 13,771 kWh demanded by the heat pump are renewable). The economic analysis indicates a payback period of about six years, what makes the proposal greatly attractive.