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International audience; The paper reports a system combining Solar Thermal Collectors (STC), Borehole Thermal Energy Storage (BTES), a Heap Pump (HP) and a backup boiler for space heating and Domestic Hot Water (DHW) production. The integration of the components and the overall control strategy are described. The system is flexible, being able to select the best thermal source and to use it directly or through a HP, while only the excess solar heat is stored into the BTES. The contribution of every subsystem to the energy mix is discussed. For a "reference configuration" combining the three subsystems ("Design D") and characterized by heating and DHW needs of 510.5 MWh.y − 1 and 226.7 MWh.y − 1 respectively, a BTES volume of 15000 m 3 , a distance between boreholes of 3 m, a STC area of 2500 m 2 , and a solar tank volume of 100 m 3 , the system uses 274 units of gas and electricity to provide 1000 units of heating and DHW. This reference configuration outperforms any alternative design: Design A (STC only), Design B (STC and HP) and design C (STC and BTES) would respectively require 612, 480 and 591 units of gas and electricity to do so. A one-at-a-time analysis reveals that the STC area, azimuth and inclination, the solar tank volume, the BTES volume, the borehole density and the HP power are key parameters to the overall system performance.

The aim of the current study is to evaluate the performance of a domestic water heating system for residential areas in Baghdad climatic conditions for substituting electric water heaters with solar-powered water heaters using solar collectors. Many countries, such as Iraq, are sluggish with electric power issues while receiving very high solar insolation. Solar energy is a clean, non-depleting and low-cost source that can be used especially in residential areas, which forms a great percentage of energy consumption by replacing electric water heating with solar water heating to reduce electricity usage. Therefore, six flat plate solar collectors with an absorbing area of 1.92×0.85m with one 4mm thick glass cover are utilized for experimental investigation under the Baghdad climatic conditions. The collector was tested under steady-state settings, which assumed that sunlight intensity, ambient temperature, and inlet-outdoor temperature difference in each collector in the system were constant throughout the operation. According to the experimental results, during the test months of November, December, January, and February, the time-weighted experimental daily average collector array efficiency is found in the range of 40% to 60%. Furthermore, the greater energy gain and performance of the solar collector array attain a peak value at solar noon. Additionally, a solar collector with flat plates can easily achieve relatively high water temperature levels of 70°C in the winter season. In addition, using a solar domestic hot water system as a water heater in Baghdad climatic conditions by substituting electric water heaters is useful for saving power consumption

Ultra-low temperature district heating (ULTDH) systems improve the heat distribution efficiency by reducing thermal network losses and can provide an easier access to Renewable Energy Sources (RES) by utilizing them as heat sources through Power-to-Heat solutions. In this paper, a data-driven seasonal-ARIMA model is developed to forecast Domestic Hot Water (DHW) demand at different time resolutions ranging from 10 to 60 minutes and a control-oriented non-linear model of a Heat Booster Substation (HBS) is developed, with main components including a Hot Water Storage Tank (HWST), two electric-driven heat pumps and a heat exchanger. Further, an optimal control strategy using Genetic Algorithm is developed for DHW preparation in ULTDH systems with the dual objective of generating load-shift flexibility on the demand side and reducing energy costs. The developed control strategy is successfully implemented to utilize the thermal energy storage capability of the HBS to optimally schedule the charging of the HWST based on electricity price signals. In comparison to the current rule-based control strategy, the developed control strategy demonstrates significant demand side flexibility and achieves energy cost savings of more than 70%. With increased DHW usage and greater volatility in electrical prices due to higher penetration of RES, greater potential for demand side flexibility is demonstrated and increased energy cost savings (more than 100%) are realized.

The paper illustrates the design and drafting of the Water Safety Plan (WSP) of a health facility, particularly with regard to water intended for human consumption. The components already present in the water and sanitary system as well as the control measures already provided, are described and critically discussed. Following the hazards identification and risk assessment related to the plant, some corrective measures and actions that have been proposed and implemented, are discussed.

Electrification is key to reaching decarbonization goals and curbing the impacts of climate change. Multi-function integrated heat pumps provide opportunities to reduce installation costs and space required for all-electric buildings. Multi-function heat pumps can use the compressor heat during a space cooling operation, which is otherwise wasted to the ambient through the condenser coil, to heat up water for domestic use. This project tested a multi-function heat pump that combines space cooling, dehumidification, ventilation, and domestic hot water (DHW) in a compact system (POD). Evaluation of the POD was conducted in environmental chambers simulating various indoor and outdoor conditions. Air flow and ventilation rates were calibrated, and the system was operated as per manufacturer recommendations. Performance metrics were compared across two operational modes of the POD: space cooling only and space cooling with DHW production. Operational mode decisions of the system controls impact the performance, for instance, cooling COP increases during operation with DHW heating compared to space cooling-only mode. In the combined mode, it was also observed that the cooling COP diminishes by 0.1 with every 3°F rise in tank temperature. The results indicate that a multi-function heat pump performance is not only dependent on the indoor and outdoor conditions but also on the DHW tank water temperatures. This study describes the performance of an integrated space conditioning and water heating system, while shedding light on the system metrics that would be useful to evaluate and rate such systems.

Electric Storage Water Heaters (ESWH) are a widespread solution to supply domestic hot water (DHW) to dwellings and other applications. The working principle of these units makes them a great resource for peak shaving, which is particularly important due to the level of penetration renewable energies are achieving and their intermittent nature. Renewable energy deployment in the electricity market translates into large electricity price fluctuations throughout the day for individual users. The purpose of this study was to find a demand–response strategy for the activation of the heating element based on a multiobjective minimization of electricity cost and user discomfort, assuming a known DHW consumption profile. An experimentally validated numerical model was used to perform an evaluation of the potential savings with the demand–response optimized strategy compared to a thermostat-based approach. Results showed that cost savings of approximately 12% can be achieved on a yearly basis, while even improving user thermal comfort. Moreover, increasing the ESWH volume would allow (i) more aggressive demand–response strategies in terms of cost savings, and (ii) higher level of uncertainty in the DHW consumption profile, without detriment to discomfort.

Collective heating systems have multiple end-users with time-varying, often different temperature demands. There are several concepts catering to this, e.g., multi-pipe networks and 2-pipe networks with or without decentralised booster systems. In this study, we focus on 2-pipe networks with a changing supply temperature by smart use of decentralised storage. By grouping high-temperature demands, the average supply temperature can be lowered during large parts of the day, which is beneficial for system efficiency. The actual energy-saving potential, however, can be case-specific and is expected to depend on design choices and implemented control strategies. In this paper, these dependencies are assessed and identified by implementing two optimised rule-based control strategies, providing in such a way a bench-mark for other control strategies. The results show that grouping yields energy savings of up to 36% at similar peak demand as with conventional control strategies. The energy-saving potential is greatest for large storage volumes and small networks, but large networks with large storage and proper control choices can also achieve around 30% energy savings. Moreover, high-temperature time can easily be reduced to less than 40% of the day, which could make space cooling without decentralised booster heat pumps possible, but this requires further research.

Encapsulated phase change material (PCM) can be used to increase the capacity of domestic hot water (DHW) storages by a factor of 2 to 3. This extra capacity allows for an increase of own-consumption and self-sufficiency of locally produced renewable energy from solar thermal or photovoltaic systems and thus reduces the energy demand taken from the grid or other fuel sources. While the energetic sustainability can already be seen directly from simulations, the environmental benefit in terms of avoided CO2 emissions depends heavily on the life cycle analysis (LCA) of the added PCM capsules compared to the energy saved. This LCA was carried out for a demonstrator PCM-enhanced domestic hot water station and shows a very early break-even point for CO2 emissions. In addition, a comparison was made with a battery system (as an electrical storage system in front of the heat pump, with equivalent heat capacity), which shows that the latent heat storage system with encapsulated PCM leads to ten times fewer emissions per kWh of thermal energy delivered., + ID der Publikation: hslu_88639 + Art des Beitrages: Präsentation Konferenzpapier/Tagungsbeitrag + Sprache: Englisch + Letzte Aktualisierung: 2022-03-15 11:45:22

Calculations of solar collector hourly thermal energy output as part of central solar water heating system with individual 150 liters storage tanks for each apartment in high rise multi-apartment residential building in Tel Aviv. The energy output at noon is 758 kcal/hr in January and 1,221 kcal/hr in April. Solar collectors supply 2,647 kWh/year of thermal energy to each apartment, minimum 5.41 kWh/day on average day in December, maximum 8.53 kWh/day in August. Hot water supply equivalent at 40°C is 30 liter/hr in December and 81 liter/hr in August at noon, 192 liter/day in January to 500 liter/day in August.

Demand-responsive control of electrically heated hot water storage tanks (HWSTs) is one solution, already present in the building stock, to stabilise volatile energy networks and markets. This has been put into sharp focus with the current energy crisis in Europe due to reduced access to natural gas. Furthermore, increasing proportions of intermittent renewable energy will likely add to this volatility. However, the adoption of demand response (DR) by consumers is highly dependent on the economic benefit. This study assesses the economic potential of DR of centralised HWSTs through both an analysis of spot price data and an optimisation algorithm approximating DR control. The methods are applied to a case study apartment building in Norway using current pricing models and examine the effect of the demand profile, electricity prices, heating power and storage capacity on energy cost and energy flexibility. Unit cost savings from DR are closely linked to the variation in unit energy price during the optimisation period. Increasing the storage capacity or the heating power increases the flexibility with a diminishing rate of return. However, increasing storage capacity does not result in cost savings as additional heat losses are greater than the saving from shifting demand, except for during highly volatile electricity price periods. Changing the minimum setpoint temperature improves the cost curve as a greater thermal storage capacity can be achieved without increasing heat loss. Systems utilising a smaller heating power are more economical due to the dominant role of the monthly price related to the peak energy demand of the system.

This paper shows a comparison of the vertical and horizontal tank orientation and the associated maximum demands from synthesized aggregated load models for various grid scenarios. Aggregated load profiles are produced by replicating a 50 litre (50% capacity) draw event for a 100-litre dual-mountable electric water heater (EWH) for each orientation. A total of 416 load profiles are produced containing 208 sets of horizontal and vertical aggregated profiles for comparison. Two factors are varied, (1) total EWH population from 1 to 1 million in various increments and (2) peak time window for initiating EWH draws ranging from 1 to 12 hours, where a Gaussian distribution is applied to the times each EWH starts participating on the grid. The resulting aggregated load profiles show that EWHs in the vertical orientation produce a higher aggregated maximum demand whereas the horizontal orientation can have a much lower aggregated maximum demand to a ratio of 0.58. A maximum demand ratio P h /P v of 0.80 is determined for a scenario similar to normal grid operation for a peak time window of 4 hours. The significance of this work is to quantify the difference in maximum power demand of a population of EWHs due to tank orientations in a controlled simulated environment.

The design and demonstration of a solar PVT assisted - heat pump system with a cold buffer storage tank on the source side of the heat pump and a hot storage tank for domestic hot water preparation is presented. The system was subject to real weather conditions and hot water draw offs. Measurements over nine months are presented and analyzed. The focus was on the thermal dynamic of the system and the interplay between the heat pump, the storage tanks and the thermal absorber of the uninsulated PVT panel. The hot water demand was almost completely covered by the thermal part of the PVT collector in sunny summer periods. In less sunny periods, the brine-water heat pump recharged the hot water tank after draw offs and discharged the buffer storage tank. The uninsulated PVT collector worked as an energy absorber and was able to extract heat form the ambient air and recharge the buffer storage tank to the ambient air temperature when no solar irradiance was available. In the less sunny and colder periods, the PVT added a significant amount of energy to the cold storage tank.

An innovative renewable-energy based system is examined for covering the heating and cooling demand in residential buildings. This system adopts an alternative solar-assisted heat pump configuration, developed around its two main components: the PVT collectors and a dual-source heat pump. The heat produced by the collectors can be either used directly for covering the heating needs or stored in a buffer tank for supplying the heat pump with low-temperature heat, exploiting all solar heat and operating the heat pump with an elevated performance for a longer period during the day. Once the stored heat in the buffer tank is discharged, the heat pump is supplied by ambient heat. The same configuration can also operate at cooling mode during summer, with the heat pump reversing its operation. The current work examines the main system parameters, in order to evaluate its performance for covering a large share of the building’s energy needs.

Nowadays, one of the most important challenges in the residential sector is the efficiency improvement of the equipment and systems used for space heating (SH) and domestic hot water (DHW) production. The main objective is to reduce the consumption of fossil fuels and CO2 emissions in these applications. In this context, heat pumps are an effective technology as an alternative to boilers for SH and DHW production. However, the SH demand has a different temperature level than the DWH demand. Generally, the SH demand has a variable temperature level that depends on the type of distribution system (type of building) and the different climate conditions, while the DHW demand requires the storage of hot water at a temperature above 60 °C to prevent the presence of legionella. On the other hand, the performance of heat pumps deteriorates when working with high condensing temperatures. This paper presents a theoretical study of the performance of an air-to-water heat pump for simultaneous SH and DHW production, where the use of a desuperheater for DHW production and the condenser for SH production are analyzed. The study shows the optimization of the desuperheater capacity for a given SH demand. The performance of the heat pump is analyzed in terms of the COP and the capacities of the condenser and desuperheater. In addition, the heat pump performance was compared with the performance of two heat pumps (SH and DHW) for the same capacity in terms of compressor swept volume and heat exchanger sizes.

This study presents the development, the methods, and the state of the art of heat pump field trials as they are currently carried out by the Heat Pump Test Center (WPZ) in Buchs SG, Switzerland. In the current study, heat pumps for hydronic heating systems in single family houses within Switzerland have been investigated since 2016. So far, over 20 air-source and geothermal heat pumps have been added to this governmental quality assurance program (Swiss Federal authority EnergieSchweiz). For each heat pump system, more than 40 measured variables are recorded at a time interval of 10 s using calibrated sensors with very low measurement uncertainty. The aim of this field study is to record the real system efficiency in operation and to draw comparisons with characteristic values from laboratory measurements and manufacturer data. The study presented is divided into two parts. The first part entitled “Technology, Methods and State of the Art of the field studies” focuses on the procedure and measuring technology of field studies performed at WPZ Buchs. The second part is entitled “Results, Analysis and Optimization of current field studies” and presents meaningful results of the current field study as well as identification and optimization of possible deficiencies in the planning, installation and handling of the investigated heat pump systems. Heat pumps installed in new and refurbished buildings have been investigated with different system boundaries. In terms of performance, the current study shows an average annual coefficient of performance (SPF) of 3.6 and a span from 3.5 to 3.7 for floor heating and domestic hot water production using air/water heat pumps. Geothermal heat pump systems reach an average annual coefficient of performance of almost 5. Although the systems are running quite satisfying overall, the results also show considerable differences between the systems as well as typical mistakes in the installation and handling of the heat pumps. A controller that does not work optimally in terms of application and consumption is a frequently found cause of decreased performance. After evaluating the baseline performance for two years, the systems are optimized to increase performance and avoid poor operation. The collected data is also used to better define guidelines for planner and installers.

Water-to-Water heat pump (WtWHP) is an efficient alternative to the current technologies used in Domestic Hot Water (DHW) production. However, this application is characterized by high secondary temperature lifts and irregular demands that define critically its design. In order to maximize the efficiency, transcritical cycles coupled to stratified storage tank has been the preferred solution. Nevertheless, recently subcritical cycles with a subcooling control system has been also considered also as a promising alternative because of the cost with the right desing the efficiencies could be in the range of transcritical system. The objective of this work is to compare the performance of both heat pump systems for DHW production in a heat recovery application where there is no restriction in the low temperature energy source availability. This situation could correspond to a source coming from sewage water or a system of low temperature district heating. The comparison has been made for the optimum configuration of both system which has implied the definition of the proper control strategy, proper sizing of the WtWHP and the tank and incorporation of a primary recovery heat exchanger in order to compare both systems in what is considered as the optimum working conditions. Results show that while both systems are able to operate with similar SCOPs, the CO2 system is more sensitive to water temperature lifts variations and temperature of the heat source than the propane WtWHP resulting in lower performances.

carried out by the Heat Pump Test Center (WPZ) in Buchs SG, Switzerland. In the current study, heat pumps for hydronic heating systems in single family houses within Switzerland have been investigated since 2016. So far, over 20 air-source and geothermal heat pumps have been added to this governmental quality assurance program (Swiss Federal authority EnergieSchweiz). For each heat pump system, more than 40 measured variables are recorded at a time interval of 10 s with calibrated sensors with very low measurement uncertainty. The aim of this field study is to record the real heat pump system efficiency in operation and to draw comparisons with characteristic values from laboratory measurements and manufacturer data. The study presented, is divided into two parts. The first part that is entitled “Technology, Methods and State of the Art of the field studies” focuses on the procedure, system boundaries and measuring technology of past and current field studies at WPZ Buchs and provides an insight to the state of the art of field performance measurements of domestic heat pumps carried out in Switzerland. The second part is entitled “Results, Analysis and Optimization of current field studies” and concentrates on various measured figures and the improvement potential of the investigated heat pump systems. Compared to the former studies made in the 1990s and early 2000s, the measurement methodology and data acquisition have changed considerably to date. Nowadays, thanks to digitalization, much more data is available. Short sampling intervals are used to describe temporal processes in heat pump systems in detail, enabling an easier detection of defects such as heat losses and unwanted circulation. Thanks to carefully defined system boundaries like JAZ, WNG and SNG heat pump systems can be compared and optimized effectively. Great importance is attached to the measurement of temperature because of its major influence on the overall uncertainty. Therefore, temperature is measured with an uncertainty of ±0.1 K/±0.02 K (absolute/relative) using directly immersed PT-100 sensors and four wire technology. Together with the prior calibration of the whole measuring equipment in the laboratory, an overall uncertainty of the target values (COP, JAZ) of 10% was achieved.

Domestic hot water heating of multifamily buildings accounts for a substantial portion of the energy load of existing buildings. This load is made up of both the energy required to produce hot water and the energy needed to maintain the temperature of the heated water within a building’s distribution piping so that heat can be promptly delivered to building occupants as needed. Properly designed heat pump water heater (HPWH) systems have the ability to improve efficiency in both water heating and temperature control operations. Further, CO2 heat pump technology reflects a shift away from traditional refrigerants and toward refrigerants with low global warming potential (GWP). In this paper’s case study, a design consisting of multiple CO2 heat pump water heaters (commonly used in single-family homes) with a novel “swing tank” was proposed to meet the demand for domestic hot water heating and recirculation loop temperature maintenance. The proposed design was applied to the retrofit of a 60-unit, low-rise, multi-family building located in the Pacific Northwest of the United States. The purpose of this paper is to verify the performance of the system including the proposed “swing tank” in a centralized SHW system using CO2 HPWH. It also provides practical information and lessons learned from the retrofit project. Long-term monitoring data showed that the system had a coefficient of performance (COP) of three or greater and provided an average of 20 gallons of hot water per day per apartment. The results of this work indicate that residential-scale CO2 HPWH equipment and a “swing tank” design can efficiently provide domestic hot water heating and temperature maintenance for mid-sized multifamily buildings.

Designing solar strategies is a powerful step forward to set up an adequate residential house in terms of energy. Many types of research have simulated the energy needs for residential buildings. Designing an improper installation can contribute to a growth in the overall energy expenditure in ensuring thermal comfort. The use of solar thermal processes in Slovakia is on a rise as compared to recent years. This study models twelve solar water heating systems created on the roof of the household. Solar energy techniques are carried out to comply with the demands of heating and domestic hot water. The analysis deals with the most efficient alternative for the arranged solar systems of the building. Considering these installations and the corresponding overall prices of machinery, the best workable alternative is selected. The potential energy performance of auxiliary heating and the energy output of the solar thermal installation are examined. The required amounts of the different energy contributions are modelled and simulated in specific software for a family house in Kosice, Slovakia. We determine the limits of the design for an apartment and analyse which procedure is used to provide the typical average water expenditure and heating need, covering a multi-criteria analysis considering costs, energy, and life cycle analysis of every installation. This approach can support professionals to decide the best scheme considering these criteria, and this method can be satisfactorily applied. In these conditions, converting a conventional gas boiler into a solar thermal system involves monthly economic savings of around EUR 140–250, with payback periods of 2.5–7 years. The energy requirements are fully covered by the solar thermal schemes and the life cycle assessment resulted in reasonable impacts on the environment. This study was financially supported by Grant Agency of Slovak Republic to support project No. 1/0512/20. This paper is also the result of the Project implementation: University Science Park TECHNICOM for Innovation Applications Supported by Knowledge Technology, ITMS: 26220220182, supported by the Research & Development Operational Programme funded by the ERDFI.

In this study, the development and comparative characterization of different composite sorbents for thermal energy storage applications is reported. Two different applications were targeted, namely, low-temperature space heating (SH) and domestic hot water (DHW) provision. From a literature analysis, the most promising hygroscopic salts were selected for these conditions, being LiCl for SH and LiBr for DHW. Furthermore, two mesoporous silica gel matrixes and a macroporous vermiculite were acquired to prepare the composites. A complete characterization was performed by investigating the porous structure of the composites before and after impregnation, through N2 physisorption, as well as checking the phase composition of the composites at different temperatures through X-ray powder diffraction (XRD) analysis. Furthermore, sorption equilibrium curves were measured in water vapor atmosphere to evaluate the adsorption capacity of the samples and a detailed calorimetric analysis was carried out to evaluate the reaction evolution under real operating conditions as well as the sorption heat of each sample. The results demonstrated a slower reaction kinetic in the vermiculite-based composites, due to the larger size of salt grains embedded in the pores, while promising volumetric storage densities of 0.7 GJ/m3 and 0.4 GJ/m3 in silica gel-based composites were achieved for SH and DHW applications, respectively.

Los sectores residencial y comercial suponen un porcentaje grande de las emisiones de gases de efecto invernadero. Para reducir estas emisiones hay que reducir el consumo de energía y desarrollar e instalar tecnologías de energías renovables. Estos cambios deben ser aplicados en viviendas de nueva construcción o en rehabilitaciones de edificios antiguos. En este proyecto se ha analizado la rehabilitación de dos viviendas de un edificio ubicado en un entorno rural a las afueras de Durango. Se han determinado las medidas aplicadas para reducir la demanda energética del edificio, y se ha analizado la rehabilitación de la instalación de calefacción y Agua Caliente Sanitaria. El objetivo del proyecto es analizar la rehabilitación realizada, y analizar el efecto que ésta tendrá en el medioambiente. También tendrá como objetivo analizar los costes económicos de la instalación energética, así como su viabilidad. Se ha aislado las viviendas mediante la colocación de distintos aislamientos en la envolvente térmica de la vivienda, y se han cambiado las ventanas. En lo que a la instalación energética se refiere, se ha instalado una bomba de calor de aerotermia para las dos viviendas, y se ha realizado una instalación de paneles fotovoltaicos en el tejado del edificio. Berotegi efektuko gasen isuri totalen ehuneko handi bat etxebizitza eta zerbitzuen sektoreari dagozkio. Isuriok murrizteko energia kontsumoa jaitsi eta energia berriztagarrien teknologiak garatu eta instalatu behar dira. Aldaketa horiek etxebizitza berrietan edota zaharren eraberritzeetan egin behar dira. Proiektu honetan, Durango kanpoaldean kokatzen den landa eremuko eraikin baten etxebizitza biren birgaitze integrala aztertu da. Berokuntza eskaria murrizteko harturiko neurriak zehaztu dira, eta berokuntza eta ur bero sanitario instalazioaren birgaitzea aztertu da. Proiektuaren helburua etxebizitzetan egindako birgaitzea aztertzea da, eta honek izango duen ingurumen inpaktuaren eta kostu ekonomikoaren eta bideragarritasunaren kalkulua egitea. Etxebizitzen inguratzaile termikoan isolamendua ezarri da eta leihoak aldatu dira. Instalazio energetikoari dagokionez, aerotermia bero-ponpa bat jarri da bi etxebizitzentzat, eta eraikinaren teilatuan panel fotovoltaikoak instalatu dira. Residential and commercial sectors are accountable for a large percentage of the greenhouse gases emitted into the atmosphere. To reduce these emissions energy consumption must be reduced and renewable energy technologies must be developed and installed. These changes must be implemented in new buildings and in older building restorations. This project has analysed the integral restoration of two houses of a building located in a rural area in the outskirts of Durango. The measures to reduce the energy demand have been determined, and the restoration of the heating and Domestic Hot Water installation has been analysed. The aims of the project are to analyse the restoration of both homes, as well as to calculate the environmental and economic impact of it. Insulation has been installed throughout the thermal enclosure of the building, and the windows have been changed. An air source heat-pump has been installed for both homes, and photovoltaic panel have been mounted in the roof.

In recent years, there has been a growing interest in heat pumps coupled with photovoltaic thermal (PVT) collectors to cover the space heating and domestic hot water demand in buildings. However, most existing systems have not been designed for the specific heat demand of the climate they are located, and limited system comparisons have been conducted regarding performance and economy in different locations. In this study, the performance of a domestic PVT heat pump system installed in Denmark was demonstrated. A TRNSYS model of the system was created and validated with experimental data from the demonstration system. Afterward, it was used to perform a sensitivity analysis on the collector area to achieve the best performance and economy, using multiple indicators. Three different systems were investigated in three locations: a PVT water-source heat pump system, a photovoltaic (PV) air-source heat pump system, and an air-source heat pump system in Denmark, Austria, and Greece.

The current high energy prices pose a serious challenge, especially in the domestic economy. In this respect, one of the main problems is obtaining domestic hot water. For this reason, this article develops a heating system applied to a conventional water tank in such a way as to minimize the necessary energy supply by converting it, under certain circumstances, into atmospheric. For this purpose, the domotic system has been equipped with sensors that automate the pressurization of the compartment and solenoid valves that regulate the external water supply. This design, to which different level sensors are applied, sends the information in real time to an artificial intelligence system, by means of deductive control, which recognizes the states of the system. This work shows the introduction of an extension of propositional dynamic logic in the field of energy efficiency. Thanks to this formalism, a qualitative control of the program variables is achieved by incorporating qualitative reasoning tools. On the other hand, it solves preventive maintenance systems through the early detection of faults in the installation. This research has led to the patenting of an intelligent domestic hot water system that considerably reduces energy consumption by setting disjointed heating intervals that, powered by renewable or non-renewable sources, are controlled by a propositional dynamic logic. This research received no external funding. Partial funding for open access charge: Universidad de Málaga.

Denmark has one of the highest Legionnaires’ disease notification rates within Europe, averaging 4.7 cases per 100,000 population annually (2017 to 2020). The relatively high incidence of disease is not uniform across the country, and approximately 70% of all domestically acquired cases in Denmark are caused by Legionella pneumophila (LP) strains that are considered less virulent. The aim of this study was to investigate if colonization rates, levels of colonization, and/or types of LP present in hot water systems were associated with geographic differences in Legionnaires’ disease incidence. Domestic water systems from four cities in Denmark were analyzed via culture and qPCR. Serogrouping and sequence typing was performed on randomly selected isolates. Single nucleotide polymorphism was used to identify clonal relationship among isolates from the four cities. The results revealed a high LP colonization rate from 68% to 87.5% among systems, composed primarily of non-serogroup 1. LP serogroup 1 reacting with the monoclonal antibody (MAb) 3/1 was not identified in any of the systems tested, while MAb 3/1 negative serogroup 1 strains were isolated from 10 systems (9.6%). We hypothesize that a combination of factors influences the incidence rate of LD in each city, including sequence type and serogroup distribution, colonization rate, concentration of Legionella in Pre-flush and Flush samples, and potentially building characteristics such as water temperature measured at the point of use.

Denmark aims to be independent of fossil fuels in the country's energy production by 2050. One of the initiatives to reach the decarbonization goal is the digitalization of the energy sector, specifically the roll-out of smart meters in the buildings connected to the district heating network. As a result, it allowed having better insights into the dynamics of the heating loads of the demand side. However, these meters often record the total energy usage without distinguishing between the energy use for space heating (SH) and domestic hot water (DHW). Additionally, the metered data have hourly resolution, which prevents the detection of short DHW usage. To tackle this limitation and gain valuable information on the buildings' heating patterns, this paper presents a new methodology to estimate the energy use for SH and DHW from total measurements in residential buildings. The method employs a combined smoothing algorithm with a support vector regression to estimate the energy use for SH from outdoor conditions. The energy use for DHW is calculated a posteriori by the difference between the total measurements and the estimated SH energy. The advantage of this technique is the ability to be applied in hourly-resolution data while only requiring local weather measurements, making it a tool to be utilized in different scenarios. This method is validated with three different sets of building cases. The first dataset consists of 28 apartments in Denmark, where the measurement resolution is coarse at 1 kWh. This case focuses on determining the method's accuracy in single-family dwellings when their measurements are truncated. The second dataset set of apartments is located in a 5-story building in Switzerland. In this case, the objective is to test the method's accuracy when analyzing aggregated measurements of all dwellings in the building. The third dataset includes hourly readings from customers connected to a DH network in Italy. In this case, the objective is to test the method's application to other building typologies (i.e., historical buildings). Because these three cases are located in different countries, this validation study also tests the method's robustness to the variability of users, locations, and heating system types.

In the effort to de-carbonize the building stock, heat pumps are increasingly utilized in Switzerland, with 70% of the fast-growing heat pump market using ambient air as heat source. Inexpensive and easy to implement, these heat pumps are, however, less efficient than their ground- or water-source counterparts. In this modeling study, we aim at increasing the efficiency of air-source heat pumps using domestic greywater-contained heat. We assess the performance improvement relative to standard heat pump configurations across various climates, seasons, building envelopes, and domestic hot water consumption patterns. The results show that the annually-averaged coefficient of performance improves by 4.1% on average – ranging from 0.6% to 7.5%. This efficiency gain translates on average to 1.8 kWh/week of compressor electricity savings. Although attractive due to its simplicity, the proposed open-loop configuration – preheating of an external heat source – only leads to moderate performance improvement of air-source heat pumps. Based on these results, we extensively discuss and compare alternative system configurations and identify several fundamental differences in the heat recovery dynamics of each configuration. We show that closed-loop systems – using greywater as direct heat source – show the largest performance improvement potential, although being more expensive and complex to implement., Applied Energy, 305, ISSN:0306-2619, ISSN:1872-9118

With limited roof space available, the selection of the most suitable solar energy systems to meet hot water and electricity demands for a household in a cost-effective way is always a challenge. This paper presents a comparative study of solar energy collection methods to meet Australian household's energy demands using both solar thermal collectors and photovoltaic (PV) systems. Numerical models are developed for various system configurations and two different scenarios are analysed in this research. In the first scenario, only PV system is used to meet both hot water and electricity demands. In the second, both the solar thermal collectors and solar PV system are used in combination for the same roof area. Based on the modelling results, economic benefits are determined and compared. The combined system was found to be a better option, providing greater benefits in cost and emission reduction.

Solar energy is the most abundant, inexhaustible and clean of all the renewable energy resources till today. Solar energy has received much more attention in building energy systems in recent years. During the first years of the twenty-first century, extensive efforts have been undertaken to alleviate global warming of the earth caused by emission of CO2 in atmosphere. These emissions are generated by intensive burning of fossil fuels to satisfy the growing energy needs of humanity. The emissions may be mitigated when part of energy needs is satisfied by using non-polluting energy sources such as solar energy, instead of fossil fuels. In households, customary is to use electricity for heating of DHW. Most of electricity is produced by using coal with high greenhouse emission. Accordingly, worldwide, the most rewarding application of solar energy is when it replaces electrical energy for heating of DHW in households. The solar collector has to take the optimal position that will guarantee the highest generation of heat. Optimal positioning must be based on rigorous calculations and not on the basis of experience. Such calculations lead to the improvement of the operation of solar energy systems. This paper gives a review of research with the objective of presenting, classifying and analysing the different criteria by which the authors observed an optimal position of the solar collector. In addition, it is important to have a high efficiency of conversion of solar energy to heat. Then, the highest amount of avoided primary energy, avoided electrical energy, avoided exergy, and decrease in CO2 emissions may be expected.

The implementation of a self-consumption photovoltaic installation in a single-family house with Passivhaus Classic certification is pre-sented. In this case the surpluses of photovoltaic production are diverted to an electrical resistance in the Sanitary Hot Water tank. The system converts electrical energy that is not self-consumed in the home, into thermal energy in the DHW tank for later use. Consumption derived from ACS is often higher than air conditioning in a Passive House, so a solution of this type reduces the energy bill and takes advantage of a renewable energy source to produce hot water, avoiding many of the maintenance problems that solar thermal energy systems usually suffered. Resumen Se presenta la implementación de una instalación fotovoltaica de autoconsumo en una vivienda unifamiliar con certificación Passivhaus Classic, en donde se desvían los excedentes de la producción fotovoltaica a una resistencia eléctrica en el depósito de Agua Caliente Sa-nitaria. El sistema convierte la energía eléctrica que no se autoconsume en la vivienda, en energía térmica en el depósito de ACS para su uso posterior. Los consumos derivados del ACS son a menudo superiores a los de climatización en una Passivhaus, así que una solución de este tipo reduce la factura energética y aprovecha una fuente de energía renovable para producir agua caliente, evitando muchos de los problemas de mantenimiento que suelen sufrir los sistemas de energía solar térmica.

A significant percentage of energy consumption in buildings is to produce hot water. Photovoltaic solar heating can be considered a clean and renewable energy option—easy to install, silent, and without maintenance—to replace the consumption of fossil fuels used in this process. This paper presents a study that simulates the heating process using thermal electrical resistors powered by photovoltaic solar energy. For this purpose, a solar hot water installation has been set up. This installation consists of a water tank with an electric resistance connected to photovoltaic modules by means of a low-cost experimental electronic conversion system. This electronic system has been developed to avoid the need for inverters or batteries, typical of traditional photovoltaic solar installations. It is an isolated system since it is not connected to the power grid. The photovoltaic solar modules, the tank, and its heating resistance correspond to commercial models. This electronic system has a 95.06% yield, and it operates across the whole irradiance’s daily curve, having verified its operation over several months. Even though this is an experimental electronic device, it is financially viable as the cost of its components is below EUR 60 per kW peak capacity. The results obtained in a proper functioning system are promising, demonstrating the technical feasibility and economic advantages of using this type of isolated photovoltaic system to power heating processes.

COVID-19 made considerable changes in the lifestyle of people, which have led to a rise in energy use in homes. So, this study investigated the relationship between COVID-19 and domestic hot water demands. For this purpose, a nondimensional and principal component analysis were conducted to find out the influencing factors using demand data before and after COVID-19 from our study site. Analysis showed that the COVID-19 outbreak affected the daily peak time and the amount of domestic hot water usage, the active case number of COVID-19 was a good indicator for correlating the changes in hot water demand and patterns. Based on this, a machine learning model with an artificial neural network was developed to predict hot water demand depending on the severity of COVID-19 and the relevant correlation was also derived. The model analysis showed that the increase in the number of active cases in the region affected the hot water demand increased at a certain rate and the maximum demand peak in morning during weekdays and weekends decreased. Furthermore, if the number of active cases reached more than 4000, the peak in morning moved to afternoon so that the energy use patterns of weekdays and weekends are assimilated.

A large part of the Kyrgyz territory is covered by mountain ranges which result in extremely cold winter periods. The cold climatic conditions of Kyrgyzstan define heating as an essential need for Kyrgyz people. The majority of the residential buildings are constructed with poor thermal insulation or none at all, which yields high energy consumption in buildings to maintain thermal comfort. Especially in rural households, the heat demand is usually covered by solid fuels (i.e. wood, branches, coal and other solid fuels) burned in traditional stoves / boilers. The intensive use of solid fuels contributes to indoor and outdoor air pollution. Hence, there is a substantial need to provide sustainable and adequate heating services for residential buildings, particularly for the rural population. In response to this, the presented research article describes an investigation of solar resources to support space heating and domestic hot water preparation for single-family homes in rural Kyrgyzstan. Besides that, it identifies the thermal performance of typical single-family houses by considering local boundary conditions such as cold climate, highaltitude and routine behavior of the inhabitants. The determination of fuel savings by implementing solar-thermal domestic heating systems helps to explain the positive impacts on the environment. The investigation shows a significant solar-thermal energy potential available for domestic space heating and hot water preparation in Kyrgyzstan.

RESUMEN: La vivienda objeto de este Trabajo Fin de Grado cuenta actualmente con una instalación térmica encargada de dar cobertura a la demanda de calefacción y agua caliente sanitaria (ACS) mediante gasóleo, un recurso no renovable. Con el fin de reducir el impacto generado por dicha instalación, se plantea la sustitución de la instalación existente por una basada en energía solar térmica y energía de biomasa. Para el diseño de dicha instalación se ha estimado en primer lugar las necesidades térmicas de ACS siguiendo lo establecido en el Código Técnico de la Edificación (CTE). También se han estimado las cargas térmicas de la vivienda a partir de las características de la envolvente de la vivienda. Tras la estimación de las necesidades térmicas se han dimensionado los colectores, acumulador, intercambiador…, así como las pérdidas de carga de la instalación con el fin de seleccionar las bombas a colocar. La nueva instalación dimensionada consta de un colector solar, un intercambiador de 11 placas de 2,5 kW de potencia, un acumulador de 200 l y una caldera de biomasa de 15,6 kW. Finalmente se ha realizado el presupuesto de la instalación dimensionada, el cual asciende a veintitrés mil seiscientos veintitrés con sesenta y cinco céntimos. ABSTRACT: The heating system of the house, object of this project, provides central heating and domestic hot water with diesel oil (non-renewable resource). With the purpose of reducing environmental impact, I am going to study the possibility of substitute the actual system for a new one using solar termal and biomass energy. In order to design this new system, I have estimated the thermal need of domestic hot water in line with the thermal building regulations. Besides that, I have estimated the heating loads of the house according to the insulation of the building. Once I have calculated the thermal need, I have evaluated the collector, accumulator and exchanger as well as the heat loss of the system to select the appropriate pump. The new system consists of a solar collector, an 11 plate heat exchanger of 2.5KW, a 200 l accumulator and a biomass boiler of 15.6 KW. Finally, to carry out this project I have valued a budget of 23.62367€. Grado en Ingeniería Eléctrica

Thermal energy storage (TES) is extensively applied in production and daily life. As a basic work, we designed a single tank phase change TES domestic hot water system using night valley power. Based on the single tank TES experimental platform, a 2D numerical model of the system was established. To optimize the performance of a single tank TES system, the effect of heat transfer fluid (HTF) inlet velocity and temperature on the heat release of the storage tank was analyzed based on simulation. The enhanced heat transfer effect of the radial cascade system and axial cascade system was also compared. The results showed that 0.8 m/s is the optimal HTF inlet velocity in the calculation range. The rule of the heat release about the HTF inlet temperature just meets the different hot water requirements in winter and summer. The heat release capacity of the radial cascade system and axial cascade system is higher than that of the conventional single-stage system, and the proportion of latent heat release in radial cascade is larger. This study will provide theoretical guidance for the optimal design of the single tank TES domestic hot water system in the future.

A major challenge in the common approach of hot water generation in residential houses lies in the highly stochastic nature of domestic hot water (DHW) demand. Learning hot water use behavior enables water heating systems to continuously adapt to the stochastic demand and reduce energy consumption. This paper aims to understand how machine learning (ML) can predict the stochastic hot water use behavior, and to investigate the potential reduction in energy use by an adapting hot water system. Different ML models are implemented on a data set of 6 residential houses, and their average performance is compared. Ten different models were evaluated, including four single models (Random Forest, Multi-Layer Perceptron, Long-Short Term Memory Neural Network, and LASSO regression), four Sequential Multi-Task models combining classification and regression models, and two Parallel Multi-Task models based on Random Forest and Multi-Layer Perceptron. Dynamic simulation of a smart hot water supply system, which adapts to the predicted demand, shows that adaptive hot water production can provide significant energy use reduction.

The solar domestic hot water system is currently widely applied as a building energy saving technique. Various forms of the system exist, which should be properly applied in practical engineering. It is significant to study the adaptability of the solar domestic hot water system as it accounts for the building energy consumption in a non-negligible proportion, which is still scarcely studied based on field measurements in current research. This study figured out the performance of the centralized solar domestic hot water system through field measurements, as well as built a sub-hourly simulation model, which has been validated with the field measurement. The model was used to analyse the influence of several factors on the energy consumption of the system, such as the water supply strategy, the use modes of occupants, the thermal insulation of pipes, and the forms of the system. The adaptability of the system was concluded.

District heating in Denmark is going through the transition from 3rd generation (80/40 °C) to 4th generation (50–55 °C/25 °C) systems in preparation for district heating based completely on renewable fuels by 2035. However, concern about Legionella growth and reduced comfort with low-temperature domestic hot water supply may be discouraging the implementation of low-temperature district heating. Aimed at providing possible solutions, this study modelled various proposals for district heating systems with supply temperatures of 65 °C, 50 °C and 35 °C and for two different building topologies. Evaluation models were built to investigate the energy, economy and exergy performances of the proposed domestic hot water systems in various configurations. The configurations of the devised domestic hot water substations were optimised to fit well with both low and ultra-low-temperature district heating and to reduce the return temperature to district heating. The benefits of lower return temperatures were also analysed compared with the current district heating situation. The evaluation results show that the decentralized substation system with instantaneous heat exchanger unit performed better under the 65 °C and 50 °C district heating scenarios, while the individual micro tank solution consumed less energy and cost less in the 35 °C district heating scenario.

This study investigated the performances of five different substation configurations in single-family houses supplied with ULTDH (ultra-low-temperature district heating). The temperature at the heat plant is 46 degrees C and around 40 degrees C at the substations. To avoid the proliferation of Legionella in the DHW (domestic hot water) and assure the comfortable temperature, all substations were installed with supplementary heating devices. Detailed measurements were taken in the substations, including the electricity demand of the supplementary heating devices. To compare the energy and economic performance of the substations, separate models were built based on standard assumptions. The relative heat and electricity delivered for preparing DHW were calculated. The results showed that substations with storage tanks and heat pumps have high relative electricity demand, which leads to higher integrated costs considering both heat and electricity for DHW preparation. The substations with in-line electric heaters have low relative electricity usage because very little heat is lost due to the instantaneous DHW preparation. Accordingly, the substations with in-line electric heaters would have the lowest energy cost for DHW preparation. To achieve optimal design and operation for the ULTDH substation, the electricity peak loads of the in-line electric heaters were analysed according to different DHW-heating strategies.

The achievement of United Nations Sustainable Development Goals, related to energy and resource use, is a critical issue for small and insulated communities. In many minor islands, solar energy is not correctly exploited, and electrical heaters are connected to weak grids with very a high share of generation by fossil fuels. As a consequence, there is the necessity to assess the potential and the suitability of diffusion of alternative systems to avoid dependency on the electrical grid and reduce carbon emissions. This paper aims to evaluate the technical and economic performances of some alternative systems exploiting renewable energy for domestic hot water production. Four different systems were simulated and studied: a heat pump connected to the grid, a heat pump coupled with a photovoltaic plant, a heat pump combined with a solar thermal collector, and a solar thermal plant. Moreover, heat and electricity storages were studied for reducing impacts on the distribution network. The work presents data gathered for a study on energy-retrofit strategies on Lampedusa Island (Italy, 35&deg, 30&prime, 56&Prime, north (N), 568 degree-days). Finally, to select the most cost-effective plant, an economic analysis of the chosen systems was carried out. This analysis shows that the best net present values are associated with the heat pump (HP) coupled with a stand-alone PV system and a small battery and solar thermal-assisted HP. The shortest payback time was calculated for the solar thermal system.

The need for efficient use of energy and sustainable energy management and the fact that large quantities of heat are deposited in the discharged sewage have contributed to the development of research on waste heat recovery. Gray water began to be seen not just as waste, but also as an alternative source of energy. Research related to the development, improvement, and finally, the popularization of waste energy recovery devices and systems has evolved rapidly over the last two decades. Initially, technologies for gray water reuse were not widely used, which was due to the low efficiency of the current heat exchangers and the significant investment outlays that would have to be covered by potential users. Research conducted by scientists from around the world has allowed us to eliminate construction flaws, improve efficiency, and also provide information on the selection of optimal waste heat recovery technology, depending on the installation conditions and operating parameters. The ability to correctly select the device allows for effective energy collection from gray water, which improves the investment profitability. This paper reviews the research regarding issues related to waste heat recovery from gray water in sewage installations and systems. A critical analysis of the current state of knowledge was carried out with a special consideration to the technologies intended for the residential buildings.

This contribution presents a concept for the direct integration of a refrigerant/water Heat Exchanger (HEX) with a Phase Change Material (PCM) in the hot superheated section of an R32 - air source compression Heat Pump (HP) cycle, for optimized Domestic Hot Water (DHW) generation in multi-family houses. The concept takes advantage of the PCMs high thermal storage capacity integrated into a high performance compact enhanced plate-and-fin aluminium HEX. On the refrigerant side, it works as a de-superheater for DHW generation during heating and cooling operation whereas the process water is connected to decentralized DHW storages located in single apartments of a low energy building. We present results from simulations at a system level for typical operating conditions and corresponding seasonal and annual performances. Compared to conventional systems, the results indicate savings up to 11% of electric energy over the year for DHW generation in average climate. The authors thank C. Köfinger, M. Lauermann, W. Pink and A. Zottl for critical discussion.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 768824 (HYBUILD). GREiA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2017 SGR 1537).

Aims: The prediction of water consumption patterns is a challenge, especially when water metering is not available at scale. The use of time-of-use survey (TUS) data offers an alternative to metering in order to track the general patterns of water consumption across large and representative groups of end-users. The paper focuses on the prediction of analytical domestic hot water (DHW) demand profiles for detailed building archetype models, using an occupant focused approach based on TUS data. The paper illustrates and discusses the resulting capability of dwelling archetypes to capture variations in heat demand and energy usage for water heating on a national scale and at high time resolution. Methodology: Five dwelling types are considered over different construction periods, representative of the majority of the Irish residential stock, which is used here as a case study. They are modelled at room level using EnergyPlus and converted into archetype models. A bottom-up approach is utilised to develop the required operational data at high space and time resolution. That methodology applies Markov Chain Monte Carlo techniques to TUS activity data to develop activity-specific profiles for occupancy and domestic equipment electricity use. It is extended to DHW demand profiles by combining the probability distributions for particular TUS activities with average daily DHW consumptions, depending on the household size, day type and season. Results: The archetype models capture variations in DHW consumption, heat demand and energy usage for DHW heating, on a national scale and a fifteen-minute basis. Moreover, they are found to be 90% accurate with the Irish standard dwelling energy assessment procedure in estimating the annual energy requirements for DHW heating. Conclusion: This study demonstrates the potential for utilising time of use surveys to predict domestic water demand profiles on a national scale and at high time resolution. Science Foundation Ireland

Waste heat from cooling circuits can be a useful source of energy for other applications, such as domestic hot water heaters. Furthermore, by removing waste heat from the cooling circuit, its effectiveness can theoretically be enhanced. A number of previous studies have shown that waste heat can be effectively harvested by installing a desuperheater in the cooling circuit between the condenser and compressor. More recently, studies have concentrated on applying heat pumps in conjunction with desuperheaters in low energy houses. In this study, we describe an experimental laboratory-scale cooling circuit with a serially connected desuperheater for heating domestic hot water. We were able to verify that installation of a desuperheater between the compressor and condenser significantly increased the energy efficiency ratio of the experimental cooling circuit, thereby confirming the hypothesis that simultaneous use of waste heat increases the efficiency of cooling circuits.

In this paper a system for the Domestic Hot Water (DHW) production based on solar collectors is analyzed by means of a dynamic approach based on a Simulink model and by using the F-chart method, able to evaluate system performances on a monthly basis. Following the dynamic approach, it is possible to evaluate hour by hour the energy collected by the solar panels and the temperature of the hot water produced by the system, by taking into account the impact of different daily DHW consumption profiles on the percentage of thermal energy produced by the solar collector (Solar Coverage Factor, SCF). The comparison between the prediction made both by using the Simulink model and the F-Chart method in terms of SCF is shown by taking into account the effect on SCF of the typology of solar collector (unglazed, glazed and evacuated collectors), of the storage tank volume connected to the solar panels and of the hourly DHW consumption profile. The results point out that SCF is strongly dependent on the daily DHW consumption profile, which cannot be taken into account in a quasi-static approach like the F-chart method.

In this article, to assess the use of renewable energy sources, the method of social efficiency of substituting non-renewable fuels with renewable energy sources was used. Social efficiency means the difference of energy-environmental, economic or sociological effects connected with producing the same amount of usable product in conditions of applying reference fuel and renewable substitute energy source. The amount of useful product should equal the use of one substitute energy unit. The proposed method constitutes a generalization of the existing method of economic effect evaluation on the basis of the Economic Efficiency of Energy Substitution indicators (EEES). Furthermore, the relations of calculations which enable defining dimensionless indexes for the effects of interest and method of standardization of the social efficiency index were described. The procedure is applied for the evaluation of renewable energy sources (solar energy in solar collectors, boilers powered by biofuels and heat pumps using geothermal energy) to prepare hot tap water.

Heat pumps have a significant and increasing share in the European heating market. In most applications heat pumps are operated with a storage tank, either for domestic hot water or for the space heating circuit. The design of the storage and its connection to the heat pump has a significant influence on the performance of the heat pump and the whole system. Within a comprehensive investigation, system simulations in TRNSYS are used to identify the optimum design of two typical systems with a heat pump connected to a buffer storage including total storage volume, number and size of heated zones, sensor and in- and outlet positions. As result, a sharp decrease in the energy demand can be reached if the storage is equipped with two heat zones instead of one. This can be explained by the decreased set temperature in the additional heat zone for space heating leading to a higher performance of the heat pump. Other measures with a positive effect on the energy demand are a large space heating volume, the number and place of sensors, low set temperatures and the sensor position in the upper part of the heating zone. The investigation gives important recommendations how to connect a heat pump with a storage tank and may be considered as design rules for all heating systems consisting of heat pump and different types of storage tanks.

Currently, a number of companies manufacture liquid-to-water heat pumps for geothermal applications, based on the scroll compressor technology and using refrigerant R407C. The performance of this kind of machines depends greatly on the operating conditions, basically on the temperature levels of the liquid and water fluids. This paper presents an experimental study of a liquid-to-water heat pump with the possibility of domestic hot water production. The refrigerant used is R407C. The main components of the heat pump are a scroll type compressor, a desuperheater for hot water production, two brazed plate heat exchangers (condenser and evaporator) and a thermostatic expansion valve with external equalizer. A liquid-vapor heat exchanger has been included to check the effect of this heat exchanger on the heat pump performance. Experimental results for typical operating conditions of liquid-to-water heat pumps (EN 14511-2, 2013) in the heating mode of operation (low and medium temperature applications) are presented and discussed. Additional tests were performed to check the performance of the heat pump with domestic hot water production at different water temperature values. From the experimental measurements, parameters such as the COP, heating powers or compressor electric power consumption were obtained and analyzed. The final goal of the paper is to characterize and to explain from a thermodynamic perspective the performance of the heat pump under a broad range of operating conditions.

International audience; This paper presents tests results of a large system on a semi-virtual test bench. The tested system aims to provide the heat needed for domestic hot water and space heating of a building with 19 housing units. The three main thermal sources of the systems are the heat recovery on exhaust air, the heat recovery on grey water and solar thermal collectors. Those sources are combined with a heat pump and terminal auxiliary systems. The core part of the system was set up in the test bench: two 1000L storage tanks, a 20kW heat pump and the controller of the whole system. This real part interacted with a virtual environment emulating the other parts of the system through hydraulic modules. A realistic test sequence has been defined to study the system operations and to assess its performances. Results are promising and lead to the installation of such a system in a real building.

A new type of photovoltaic (PV) fresh air and domestic hot water system is established to improve indoor air quality and to provide living hot water. And a phase change energy storage water tank heating system is established to optimize heating with non-continuous energy forms, such as solar energy. A 600 mm * 485 mm * 250 mm phase change material is selected as the storage container, decanoic acid is as the main phase change material, and aluminium alloy box is as the package material. We establish a real scale model of the system and apply the FLUENT software to explore and optimize the design scheme employed in the heating system. Effective hot-melt method is used in dealing with the enthalpy of the phase change material. The system will be an effective way to solve the indoor air quality problem and to achieve the optimal allocation of energy.

Drain water heat exchangers worldwide are used since the end of the twentieth century. Different drain water heat exchangers have been installed in Lithuania in last five years. Performance of these systems varies depending on the type of energy users, equipment and design of the systems, as well as their maintenance. The aim of this paper was to analyze different types of drain water heat exchangers and operational systems from the perspective of energy saving and temperature effectiveness. One drain water heat exchanger system in Lithuania was selected for the analysis. Calculation of temperature effectiveness showed that in most cases it is possible to save energy for hot water preparation.