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This study addresses the issue of increasing energy consumption for household hot water production, emphasizing the significance of incorporating solar energy to lower this demand. This topic is critical in light of the need to minimize reliance on traditional energy sources while also limiting environmental effect. The study assesses the performance of an individual solar water heater built for the average family, with a focus on energy efficiency. The technology used involves the integration of an optimal solar tracking system, which is capable of autonomously altering the orientation of the solar thermal panels during the day, increasing solar energy capture. This dynamic change increased the efficiency of the water heating system by around 13%, demonstrating the efficacy of this strategy. In the end, the study shows that using a dynamic solar tracking technology can result in significant energy savings and improve the efficiency of solar water heaters. The novelty of this work is in the improvement of solar tracking, which goes beyond the standard static systems commonly explored by allowing real-time adjustment to maximize the utilization of solar energy. [ABSTRACT FROM AUTHOR]

Water consumption in social housing is related to social, economic, and environmental sustainability. Hot, cold, and total daily water consumption of 220 residential units in two social housing complexes in Southern Brazil were investigated to examine how they relate to construction features, user behavior, weather, and socioeconomic factors. The units in both complexes are similar in size, water fixtures, and hot water systems. However, each complex is equipped with a distinct type of cold-water tank. Units with central water towers consume more water than do those with water tanks on their roofs. According to the linear regression, the use of a solar water heating system increases water consumption, thus reinforcing the need for holistic sustainability in design. The number of people and composition of households were also predictors of water consumption, with single-occupant households consuming the most water per capita. These findings imply that the consideration of different construction alternatives and household diversity during the design phase can lead to more sustainable social housing projects. [ABSTRACT FROM AUTHOR]

This paper concerns an economic and exergetic efficiency analysis of a plate heat exchanger placed in a solar installation with TiO2:SiO2/DI:EG nanofluid. This device separates the primary circuit—with the solar fluid—and the secondary circuit—in which domestic hot water flows (DHW). The solar fluid is TiO2:SiO2 nanofluid with a concentration in the range of 0.5–1.5%vol. and T = 60 °C. Its flow is maintained at a constant level of 3 dm3/min. The heat-receiving medium is domestic water with an initial temperature of 30 °C. This work records a DHW flow of V ˙ D H W , i n = 3–6(12) dm3/min. In order to calculate the exergy efficiency of the system, first, the total exergy destruction, the entropy generation number Ns, and the Bejan number Be are determined. Only for a comparable solar fluid flow, DHW V ˙ n f = V ˙ D H W 3 dm3/min, and concentrations of 0 and 0.5%vol. is there no significant improvement in the exergy efficiency. In other cases, the presence of nanoparticles significantly improves the heat transfer. The TiO2:SiO2/DI:EG nanofluid is even a 13 to 26% more effective working fluid than the traditional solar fluid; at Re = 329, the exergy efficiency is η e x e r g y = 37.29%, with a nanoparticle concentration of 0% and η e x e r g y (1.5%vol.) = 50.56%; with Re = 430, η e x e r g y (0%) = 57.03% and η e x e r g y (1.5%) = 65.9%. [ABSTRACT FROM AUTHOR]

The utilization of phase change materials (PCMs) in solar water heating systems (SWHS) has undergone notable advancements, driven by a rising demand for systems delivering superior performance and efficiency. Extensive research suggests that enhancing heat transfer (HTE) in storage systems is crucial for achieving these improvements. This review employs a bibliometric analysis to track the evolution of HTE methods within this field. While current literature underscores the necessity for further exploration into hot water generation applications, several methodologies exhibit significant promise. Particularly, strategies such as fins, encapsulation, and porous media emerge as prominent HTE techniques, alongside nanofluids, which hold the potential for augmenting solar water heating systems. This review also identifies numerous unexplored techniques awaiting investigation, aiming to pave new paths in research and application within the field of hot water generation. It highlights methods that could be used independently or alongside predominantly used techniques. [ABSTRACT FROM AUTHOR]

Among solar energy technologies, differences exist in terms of costs, performance, and environmental sustainability. Flatplate solar collectors, solar towers, and parabolic dish systems offer high thermal efficiency and versatility, but they may be more costly and bulky compared to other collector models. This study focused on evaluating the efficiency of a cylindrical parabolic collector (CPC) for the production of domestic hot water in a high Andean region of Peru, using the F-Chart method. Its performance was estimated considering the energy demand for hot water in a single-family home with four occupants, in accordance with national regulations and international recommendations. Additionally, the collector area, water temperature, and incident solar radiation were determined based on meteorological data obtained using the PVsyst software. On the other hand, the F-Chart methodology was employed to find the dimensionless factors X and Y of the CPC collector, which allowed estimating the solar fraction factor and the monthly useful energy that can be provided by the designed CPC system. The results showed that, during months of maximum solar radiation, the CPC is capable of satisfying between 129% and 144% of the energy demand for hot water. This indicates that there is a surplus of usable solar energy in the collector during the summer, while in autumn and winter, the solar contribution balances and slightly exceeds the demand. CPC can significantly contribute to the development of high Andean areas by improving quality of life, reducing costs, and promoting environmental sustainability compared to other available technologies. [ABSTRACT FROM AUTHOR]

As electric hot water cylinders (HWCs) have a large capacity for thermal storage, they are well-suited for Demand Side Management (DSM). This paper compares different methods of HWC temperature control and presents a methodology to assess the amount of thermal storage available in HWCs for demand side management based on use behaviour in different household types. Simple stochastic methods for domestic hot water (DHW) demand prediction were employed to design a smart controller that produced lower rates of unmet DHW demand and higher available storage than setpoint and ripple controllers. The average storage available for DSM from the use of this smart controller is predicted to be between 3.63 and 7.20 kWh per household. These results indicate the use of HWCs for thermal storage is a low-cost viable option for peak-shaving of power system load and could decrease power system greenhouse gas (GHG) emissions in countries such as Aotearoa New Zealand, where GHG-emitting electricity generation is primarily used to meet peak loads. [ABSTRACT FROM AUTHOR]

In the present work, the operating results from an innovative, renewable, energy-based space-heating and domestic hot water (DHW) system are shown. The system used solar thermal energy as its primary source and was assisted by a shallow geothermal application in order to accommodate the space-heating and DHW needs of a domestic building in Austria. The system incorporated phase-change materials (PCMs) in specially designed containers to function as heat-storage modules and provide an energy storage capability for both the space-heating and DHW subsystems. This system was designed, implemented, and tested under real operating conditions in a building for a period of one year. The operating and energy results for the system are demonstrated in this work. The system was compared with a conventional one, and a reduction in the primary energy consumption equal to 84.3% was achieved. The maintenance and operating costs of the system were reduced by 79.7% compared to the conventional system, thus significantly contributing to the NZEB target of the building. The newly proposed system, although presenting an increased operating complexity, utilizes an innovative self-learning control system that manages all of its operations. The combination of a solar thermal energy source with thermal energy storage increases the use of renewable energy by extending the capacity of the system beyond the solar hours and using excess solar energy for space-heating needs. The thermal energy storage unit also increases the energy and economic efficiency of the geothermal heat pump by operating it during the hours of a reduced electricity tariff and using the stored energy during hours of a high electricity demand. The cost for the installation of such a system is higher than a conventional one, but due to the significantly decreased operating costs, the pay-back period was calculated to be 8.7 years. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive life cycle assessment (LCA) comparing the environmental impact of a Condensing Gas Boiler (CGB) and an Air Source Heat Pump (ASHP) within the context of a residential building. As the demand for sustainable and energy-efficient heating solutions rises, evaluating the environmental performance of these technologies becomes crucial for informed decision-making. The assessment encompasses the entire life cycle of both heating systems, including raw materials, production, transportation, installation, operation, and with deep focus on end-of-life disposal through recycling, landfill, and incineration. The environmental indicators considered in the analysis include greenhouse gas emissions, energy consumption, and other relevant impact categories. This study has been conducted using SimaPro 9.4.0 program database with IMPACT 2002+ method and findings from this research aim to guide homeowners, policymakers, and industry stakeholders in making informed decisions regarding the adoption of heating technologies in residential buildings. By shedding light on the environmental implications of CGBs and ASHPs, this LCA contributes valuable insights toward the transition to sustainable and energy-efficient residential heating solutions and destruction methodologies for better environmental gain. [ABSTRACT FROM AUTHOR]

Domestic hot water production is the second most important energy use in the European residential sector, nowadays accounting for 14% of the sector's total final energy consumption. Despite its importance, the energy efficiency improvement rates for domestic hot water are lower than for other residential energy services, hence calling for energy-saving measures. One key measure is to install flow restrictors. Their advantages are the low upfront cost, easy installation, and suitability for integration into energy efficiency programs. Focusing on flow restrictors, this paper presents different methods for quantifying the energy savings using ex-ante and ex-post approaches: deemed savings (DES), dedicated measurements (DMs), and monthly and yearly billing analysis (SMBA and ABA). These methods were tested using information based on measurements (water flow, temperatures), historical billing analysis, a survey among inhabitants, and interviews with field experts. While measurements made at individual faucets or showerheads show significant water savings (20% and 33% respectively), energy savings associated with hot water production in the boiler (final energy) are significantly lower (around 10%) but far from being negligible. The main reasons for the difference are thermal losses related to hot water distribution in central heating systems, usages not affected by flow restrictors, and inhabitants removing them. We conclude that flow restrictors offer promising potential for short- to medium-term implementation. Given the simplicity of this solution, we recommend including it systematically in energy efficiency programs, as well as implementing a ban on fixtures with flow rates beyond a predefined level. [ABSTRACT FROM AUTHOR]

Electric Hot Water Cylinders (HWCs) offer considerable Demand Side Management in Aotearoa New Zealand, which can provide load management and increase integration of renewable electricity. In this work, scenario analyses are conducted to simulate the impact on Low Voltage transformer load and demand fulfilment of four HWC controller types: setpoint (the default in Aotearoa New Zealand), ripple, smart-power, and smart-thermostat. All controllers reduce peak electricity demand by 14-34% from setpoint, where 34% is the maximum possible reduction with hot water control. Unmet demand, which indicates insufficient hot water and can lead to negative outcomes such as cold showers, is increased by 120% and 12-69% by ripple and smart-power control, respectively, and decreased by 7-31% by smart-thermostat control. Average thermal losses are 2.25 kWh/day for the setpoint controller, and between 2.20-2.76 kWh/day for other controllers. Smart-power controllers demonstrate demand deferral, shifting peak electricity loads to shoulder loads, while smart-thermostat controllers demonstrate demand deferral and valley filling, shifting peak loads to times of lowest demand and smoothing load distribution. Overall, smart controllers improve load management performance with little-to-no increase in unmet demand or thermal losses. Thus, smart controllers are a viable option for Demand Side Management in Aotearoa New Zealand.Abbreviations and Nomenclature: DHW: Domestic Hot Water; DLC: Dynamic Load Control; DSM: Demand Side Management; EV: Electric Vehicle; GHG: Green House Gas; HV: High Voltage; HWC: Hot Water Cylinder; LDC: Load Duration Curve; LV: Low Voltage; MV: Medium Voltage; NZD: New Zealand Dollar; PV: PhotoVoltaic; TOU: Time Of Use; UD: Unmet Demand; WTP: Willingness To Pay; A: WTP function coefficient; B: WTP function coefficient; Cp: specific heat of water [J/kg/K]; Ctrans: cost imposed by the transformer; HWsuff: ratio of hot water sufficiency; Kloss,h: thermal losses for cylinder h [W/K]; Kmix: thermostatic mixing valve factor; m: WTP function coefficient; Ptotal: transformer power demand [W]; Pcap: transformer capacity [W]; Ph: Household power demand [W].; PHWC: heater element power [W]; Pop: Transformer limit for Type3 controller [W]; QDHW: heat loss from DHW use [W]; Qloss: heat loss from standing losses [W]; th: time horizon [s]; Tamb: ambient temperature [K]; THWC: temperature of the HWC [K]; Tin: water inlet temperature [K]; Tmin: minimum temperature before fulfilment failure; Tout: water outlet temperature [K].; Tset: temperature setpoint of the HWC controller [K]; $\dot{{\rm V}}$V˙: flow rate of hot water from the HWC [L/s]; Vavail: available DHW in the HWC [L]; VDHW: volume of hot water draw [L]; VDHW,expected: expected time weighted demand; VDHW,expected,max: maximum expected DHW demand; VHWC: volume of the HWC [L]; wf: time weighting function; ρ: density of water [kg/m3]. [ABSTRACT FROM AUTHOR]

An integrated numerical model that describes the operation of a renewable-energy-based system for a building's heating, cooling, and domestic hot water needs is described in this study. The examined energy system includes a vapor compression multi-source heat pump, PVT collectors, borehole thermal energy storage, and water tanks. Energy balance equations for the collectors and the tanks are coupled with correlations for the heat pump and the piping losses within a thermal network approach. The non-linear system of equations that arises is solved by employing in-house software developed in Python v. 3.7.3. The performance of the numerical tool is validated against measurements collected during the pilot operation of such a system installed in Athens (Greece) for two 5-day periods (summer and winter). It is shown that the proposed model can predict, both qualitatively and quantitatively, the building's energy system performance, whereas limited deviations from the experimental findings are mostly observed when highly transient phenomena occur. The numerical tool is designed with flexibility in mind and can be easily adapted to accommodate additional energy-system configurations and operational modes. Thus, it can be utilized as a supporting decision tool for new energy systems' designs and the optimization of existing ones. [ABSTRACT FROM AUTHOR]

The increase in energy demand, the scarcity of resources, as well as the adverse environmental impact of burning fossil fuels make it necessary to diversify the energy sources used. This also applies to the residential sector, which accounts for a significant proportion of global energy consumption. Particular attention should be paid to water heating, as the importance of this process in the energy balance of buildings is steadily increasing. One of the methods used to decrease energy consumption for heating water is to recover heat from greywater. However, commercially available horizontal drain water heat recovery (DWHR) units are characterized by low effectiveness, which creates a need for further research to improve it. The aim of the paper was to evaluate the possibility of improving the effectiveness of a circular horizontal DWHR unit through the use of baffles. Six different baffle models for installation in the greywater section of the heat exchanger were analyzed. The tests were conducted under the assumption of the installation of the DWHR unit on the horizontal shower waste pipe. They showed that the effectiveness of the unit equipped with baffles was higher by several to as much as 40% compared to the DWHR unit without baffles. This is tantamount to an increase in annual financial savings resulting from greywater heat recovery, as well as a reduction in CO2 emissions into the atmosphere. However, it was not possible to clearly identify the optimum baffle model. In any case, the selection should consider the hydraulic conditions in the heat exchanger before installing the baffles. The results can provide guidance for companies interested in bringing new equipment and technologies to the market. [ABSTRACT FROM AUTHOR]

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 m3, a distance between boreholes of 3 m, a STC area of 2500 m2, and a solar tank volume of 100 m3, 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. [Display omitted] [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The building sector is accountable for roughly one third of global energy- and process-related greenhouse gas emissions. Besides space heating, domestic hot water (DHW) heating contributes substantially to energy consumption and related greenhouse gas emissions in the building sector. Depending on the DHW system design and its required supply temperature, heat losses make up around 30...60 % of the energy required for DHW heating. To decrease energy consumption and reduce associated greenhouse gas emissions, it is essential to minimize heat losses and implement efficient DHW concepts. Heat pumps can potentially reduce energy consumption, but their efficiency strongly depends on the DHW system design and its required supply temperature. These aspects are evaluated by performing a comprehensive analysis of different DHW concepts utilizing heat pumps. Based on annual heat demands extracted from one year measurement data of a typical multi-family house in Germany, simulations of six different DHW concepts are performed. Our findings reveal that decentralized DHW systems or low system temperatures (48 °C), e.g. in combination with ultrafiltration for legionella treatment in centralized DHW systems, can lead to a substantial reduction in heat losses for DHW preparation of around 25 % and in final energy of 20 % compared to the reference case. In large systems the share of losses should be kept below 30 % by reducing pipe lengths and equipping the most distant tapping points with direct electric water heaters. [ABSTRACT FROM AUTHOR]

In Europe, the building sector accounts for approximately 35 % of the energy-related emissions. Hybrid systems coordinating heat pumps and gas boilers can avoid greenhouse gas (GHG) emissions from carbonized electricity production by providing demand-side flexibility without any service interruption. This work aimed to develop a control strategy for a fleet of hybrid heat pumps to reduce GHG emissions. The electricity and gas consumption of a fleet of 3000 hybrid heat pumps, heating 100,000 dwellings spread throughout France, was evaluated. A Modelica model of a district archetype was simulated in seven cities representative of the French climatic zones to obtain the national heating demand. The marginal emission factor of the electricity consumption was assessed using a French power system model coupled with marginal emission factors for interconnected power systems, which were assessed through linear regressions. Two types of control strategies (prioritizing the heat pump and fuel switch) are evaluated considering 4 different sizing for the heat pump (120 %, 50 %, 35 %, and 20 %). Between July 2018 and June 2019, a strategy prioritizing the heat pumps would have avoided between 8000 and 26,000 t CO2eq for the power system. A strategy switching between the heat pump and the boiler based on the marginal emission factor of the electricity consumption would have avoided around 38,000 t CO2eq , with a limited influence of the sizing of the heat pump. [Display omitted] • The impact of controlling a fleet of 3000 hybrid heat pumps on the power grid is evaluated. • Hybrid heat pumps can contribute to decarbonizing electricity consumption. • Between July 2018 and 2019, the new control strategy would have avoided 380 kg GHG eq per French dwelling. • The control strategy mainly decarbonized the electricity generation in the interconnected power systems. • The sizing of the heat pumps has a low impact on the avoided emissions. [ABSTRACT FROM AUTHOR]

Reduced energy consumption is essential for a rapid transition to net zero carbon emissions. Residential energy may constitute 27 % of primary energy consumption, and 20 %–50 % of residential energy is water-related energy (WRE). However, residential WRE consumption is difficult to quantify due to challenges in collecting data. The aim of this literature review is to critically appraise and compare models of residential WRE. This is the first literature review to provide a comparison of modelled estimates of residential WRE consumption. Reported values for residential WRE consumption were highly variable, ranging from 1 to 7 kWh/person/day. The results are not representative of the global population because 50 % of studies were conducted in Europe, while remaining studies were scattered across eight countries. 30 % of studies quantified energy consumption of specific end-uses (e.g. shower), and 40 % of studies only considered average consumption. Of the 61 studies reviewed, only four studies demonstrated clear validation of WRE consumption, and no studies validated energy consumption of individual end-uses. Therefore, it is difficult to determine whether the variability in reported results is due to true variability in residential WRE consumption, or uncertainty in the modelling approaches. Since successful water and energy reduction has been based on knowledge of specific end-uses, WRE models need better consideration of end-uses in order to inform design of interventions to reduce WRE consumption. Future research in this area also requires a greater focus on validation of modelling tools and wider geographical scope. [Display omitted] • Predicted water-related energy consumption ranged from 1 to 7 kWh/person/day. • Reviewed studies were conducted in only 8 countries outside Europe. • Significant variability exists in spatial and temporal resolution of models. • No studies validated water-related energy consumption for residential end-uses. [ABSTRACT FROM AUTHOR]

Domestic hot water (DHW) is essential for daily life, yet the production can be energy intensive. Advances in building insulation reduced space heating demand, while DHW energy demand remained constant or even increased. The need for a higher proportion of renewable heat amplifies the conflict in DHW systems between energy efficiency, hygiene, and comfort, since high temperatures are required for hygienic purposes. Thus, developing DHW systems efficiently utilising renewable heat without excessive temperature requirements is essential. This paper reviews efficiency and hygiene challenges in DHW systems and assesses proposed solutions through comparative simulations in well-insulated residential buildings. Results show higher efficiencies in decentralised than centralised DHW systems. However, even in decentralised systems the necessity for circulation is a significant limitation. Lowering DHW temperature or transitioning to decentralised systems significantly reduces final energy demand, improves heat pump performance and increases the renewable heat share. Reducing DHW temperature from 60 to 50 °C increases stagnation periods in lower temperature intervals (22–34 °C) in warm water pipes. The study indicates significant potential to increase system efficiency and reduce final energy demand in decentralised or low-temperature DHW systems and introduces a novel method to compare conditions with regard to hygiene of DHW system simulations. [ABSTRACT FROM AUTHOR]

This paper presents a new geometry of Latent Thermal Energy Storage (LTES), acting as both a plate heat exchanger and a storage unit, which can be charged and discharged simultaneously. The modelling of this LTES is presented in a solar-assisted heat pump. The dynamic models of the thermal panels and the LTES are based on the conservation of mass and energy equations. The aims of the study is to dynamically simulate this system combining solar-assisted heat pump and four Phase Change Material (PCM) storage units, for 7 days in winter and summer. A sensitivity study is carried out to determine the ideal system design parameters (LTES units set up in parallel and solar area), using multi-criteria decision-making methods. The winter selected configuration consists of 5 LTES units for each application (solar, heating and DHW) and 249.9 m 2 of solar panels. In summer, some LTES are disconnected and 3 cooling LTES are used. Then, a Life Cycle Assessment (LCA) is carried out on the system's use life cycle phase. Finally, the ideal solar-assisted heat pump with LTES is compared with conventional technologies (electricity and natural gas) or the use of sensible TES in terms of energy and environmental criteria. The electrical energy consumed by the sensible and latent solar-assisted heat pumps is similar, resulting in a similar ecological footprint. The results show the benefits of these systems compared with conventional technologies. From an energy point of view, the savings are significant, with energy consumption 9 times lower than with a reversible heat pump using electricity. As a result, this system reduces the ecological footprint of the building needs by more than 75% compared with conventional technologies. Future work will focus on the optimisation of operating parameters such as flow rates, and the LCA over the entire life cycle of the system. • A sensitivity study is performed to determine the number of latent storages and the solar area. • TOPSIS method with Shannon entropy is used to select a compromise solution. • Environmental impact of system's use is compared with that of conventional systems. • Power use and ecological footprint of systems with latent or water storages are compared. • Similar environmental footprint during use step is obtained with latent or sensible storages. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ground-source integrated heat pump (GSIHP) was evaluated for residential NZEBs. • Transient building energy simulation was conducted using validated model. • GSIHP achieved 37 % and 54 % energy savings compared to GSHP and ASHP, respectively. • GSIHP reduced monthly peak power consumption by (50 to 73) %. • Ground heat exchanger length was studied in terms of energy use and design criteria. For net-zero energy buildings (NZEBs), efficient heating, ventilation, and air-conditioning (HVAC) systems reduce the demand that must be met by renewable energy supply. Ground-source integrated heat pumps (GSIHPs) are attractive state-of-the-art HVAC candidates that efficiently provide all the heating, cooling, and domestic hot water (DHW) for a residence. We investigated the performance of a variable-speed GSIHP applied to a residential NZEB in Gaithersburg, Maryland, USA, using an annual building energy simulation in TRNSYS. The validated building model incorporated the performance of all facility equipment and simulated the scheduled thermal and electric energy use and gains within the building. For the GSIHP and all compared options, the renewable energy was generated from a roof-mounted photovoltaic (PV) array whose size was adjusted to achieve exactly net-zero annual energy use. The combined annual heating, cooling, dehumidifier, and DHW energy use with the GSIHP was 4112 kWh, a 37 % reduction compared to a two-capacity GSHP and a standalone heat pump water heater (HPWH). The variable-speed and more efficient components of the GSIHP reduced energy use by 18 %, and the remaining 19 % reduction was attributed to the more efficient water heating. Compared to a two-capacity air-source heat pump (ASHP) with a HPWH and an ASHP with an electric water heater (EWH), the GSIHP energy savings were 45 % and 54 %, respectively. We also varied ground heat exchanger (GHX) borehole depth and found little reduction in GSIHP energy use when GHX length was increased beyond that which minimally satisfied the heating criteria (55 m per bore with 2 bores). Finally, we explored using a solar hot water (SHW) system and found minimal benefit for the GSIHP and modest savings for the GSHP. [ABSTRACT FROM AUTHOR]

This study focuses on the development and testing under lab-controlled conditions of a hybrid sensible–latent thermal energy storage (TES) system for domestic hot water (DHW) provision in residential buildings. The TES system's design is based, for the first time in the literature, on a commercial tank-in-tank architecture integrating a macro-encapsulated commercial phase change material (PCM) inside the external tank to guarantee the safe provision of DHW and increase overall energy storage density at a reasonable cost. The PCM is a salt hydrate with a nominal melting temperature of 58 °C. The overall tank-in-tank TES volume is about 540 dm3. Almost one tenth of this volume is occupied by the PCM macro-capsules. The developed TES system was comparatively tested against the same configuration operated as a sensible TES. The obtained results showed the ability of the PCM to increase the thermal inertia inside the external tank, thus guaranteeing the quite stable provision of heat to the integral DHW tank during the stand-by periods. This effect was confirmed by the PCM's ability to achieve an energy storage capacity up to 16% higher than the reference sensible TES system. [ABSTRACT FROM AUTHOR]

This work focuses on the determination of the design and operation parameters of a thermal system depending on the optimization objective set. Its main objective and contribution concern the proposal of a generalized methodological structure involving multiobjective optimization techniques aimed at providing a solution to a practical problem, such as the design and dimensioning of a solar thermal system. The analysis is based on system operation data provided by a dynamic simulation model, leading to the development of multiple surrogate models of the thermal system. The thermal system surrogate models correlate the desired optimization objectives with thermal system design and operation parameters while additional surrogate models of the Pareto frontiers are generated. The implementation of the methodology is demonstrated through the optimal design and operation parameter dimensioning of a solar-assisted geothermal heat pump that provides domestic hot water loads of an office building. Essentially, energy consumption is optimized for a desired domestic hot water thermal load coverage. Implementation of reverse-engineering methods allows the determination of the system parameters representing the optimized criteria. [ABSTRACT FROM AUTHOR]

• Solar thermal collectors can be controlled based on time-of-use (TOU) electricity rates. • This TOU-based control strategy can increase annual cost savings by 30% • The TOU control strategy works better for systems with smaller solar fractions. • Only a simple time-based controller is required to implement this control strategy. • The target cost for a 1-year payback period is approximately $1000. Homes and commercial buildings account for roughly 40% of U.S. energy consumption. A significant portion of this energy consumption, and therefore utility cost, comes from domestic hot-water use. Solar collectors such as flat plate collectors, evacuated tubes, and combined photovoltaic/thermal panels, are renewable options that collect thermal energy and could help reduce utility costs. Hot water is generated by pumping a working fluid through the solar collector, where the fluid captures thermal energy via absorbed solar radiation incident on the collector surface. The collection of heat coincides with the availability of solar radiation, but the best time to use this thermal energy depends on the utility rate at a given time, which often changes throughout the day. In this work, we implement and simulate a control strategy using Transient System Simulation Tool (TRNSYS) that reduces utility costs by controlling when the system stores and uses thermal energy based on solar availability and time-of-use electricity rates. Our modeled results show that the control strategy can reduce utility costs associated with using hot water between 3% and 30%. We also show how the on-peak utility rates, the size and type of the solar collectors, and the location's climate impact the results. [ABSTRACT FROM AUTHOR]

• The performance characteristics of a GHP system with R410A for cooling and domestic hot water applications are systematically investigated. • In cooling mode, the total primary energy ratio is more than 31.49 % higher than that of the traditional GHP system without waste heat recovery. • The values of waste heat recovery rate in the GHP system are between 59.84 % and 78.81 %. • The PER of the GHP system is jointly determined by COP and engine thermal efficiency. This research work aimed at systematically evaluating the performance of a gas engine-driven heat pump (GHP) system with R410A for cooling and domestic hot water applications. The changes of cooling capacity (Q ˙ c), heating capacity of waste heat recovery (Q ˙ h,dom), total effective utilization energy capacity (Q ˙ all), gas consumption power (P gas), primary energy ratio (PER), total primary energy ratio (PER all), coefficient of performance (COP), and the growth rate of PER (R PER) were obtained under the conditions of different evaporator water outlet temperatures t w,out1 (5–18 ℃), engine speeds N eng (1200–2000 r/min), and ambient air temperatures T amb (30–40 ℃). The results show that the energy efficiency can be significantly improved through waste heat recovery. At low N eng , the effect of engine thermal efficiency (η eng) is greater than that of COP , and PER shows an increasing trend. However, at high N eng , the effect of η eng is less than COP , and PER tends to decrease. Among the three effect factors, the N eng and T amb have significantly larger influence on Q ˙ h,dom , the t w,out1 and N eng have greater influence on Q ˙ c , and the T amb and t w,out1 have greater influence on PER. In the experiments, the values of waste heat recovery rate (R rec,res) are between 59.84 % and 78.81 %, and the values of R PER are between 31.49 % and 60.58 %. It shows that the GHP system has an excellent waste-heat recovery effect, and the PER all is more than 31.49 % higher than that of the traditional GHP system without waste heat recovery. [ABSTRACT FROM AUTHOR]

Many studies focus on the application of phase change materials (PCMs) to a photovoltaic (PV) panel. It has been proved that these materials provide a good thermal management for the PV panel, increasing the electrical conversion efficiency and recovering useful heat. This paper investigates these innovative systems from an environmental sustainability perspective. A PV-PCM prototype, built and tested over a reference year, has been taken as case study. The recovered heat by the PCM is intended as peak shaving for the domestic hot water (DHW) energy demand of a typical residential building. The analysis involves both the Life Cycle Assessment (LCA), basing on the ISO standard 14040, and the circularity of the proposed system, proposing an alternative calculation procedure to the new Italian standard UNI 1608856. Results show that the proposed system allows the reduction of impact on climate change of around 11%, reaching a potential circularity performance of around 45%. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Determining the demand for heat power for domestic hot water preparation is necessary to perform a building energy assessment. For this, we need to predict domestic hot water consumption. Considering the number of factors influencing domestic hot water consumption, it is difficult to develop a highly accurate methodology. The aim of the study was to compare the real domestic hot water consumption and heat power for its preparation with the values calculated based on the available prediction methods in multi-family buildings. The analysis was carried out based on annual monitoring (2021 year) of domestic hot water consumption and the actual demand for heat power in eight multi-family buildings located in Grudziądz, in Central Poland. The results of these measurements were compared with the values determined based on the available methodologies for forecasting the demand for heat power and domestic hot water consumption: Sander's, Recknagel's, the standard method and the method according to Polish regulations from 2008 and 2015. The real average demand for heat power for domestic hot water was 89.8 ± 8.5 W/person, 211.2 ± 13.7 W/apartment and 4.8 ± 0.3 W/m2, and the daily domestic hot water consumption was 26.7 ± 3.6 dm3/person·day, 62.6 ± 5.8 dm3/apartment·day and 1.4 ± 0.1 dm3/m2·day. The real demand for heat power for domestic hot water was lower than that determined by the analyzed methods. The values obtained from the modified standard method based on Standard PN-92/B-01706/A1: 1999, with mean relative error of 10.5 ± 4.1%, were the closest to the real values. The current ordinance method (Regulation 2015) is characterized by an error of 45.4 ± 10.2%. The predicted domestic hot water consumption using the current ordinance was the closest to the real consumption. On average, it was higher by 7.7 ± 5.0%. [ABSTRACT FROM AUTHOR]

The availability of freshwater and energy is a serious issue in remote and islanded areas, especially at a small scale, where there may not be the possibility to access the grid and/or water distribution systems. In this context, polygeneration systems operating on the basis of local, renewable energy sources can be an answer to the users' demand for electricity, heating, cooling, and domestic hot water. The scope of the proposed paper was to investigate, numerically, the energy and economic feasibility of a novel hybrid polygeneration system powered by biomass, solar, and wind energy for a micro-district of households. The proposed system consists of a biomass-fueled steam cycle, wind turbine, photovoltaic field coupled with thermal and electrical energy storage, adsorption chiller, and a reverse osmosis water desalination unit. The system is also assisted by an LPG generator set running as backup. The system provides space heating and cooling, electrical energy, and fresh and domestic hot water to 10 households located on Pantelleria Island, Italy. The proposed system is modelled and simulated through TRNSYS software with realistic user demand. The energy and economic performance of the proposed system are assessed with respect to a reference system in different scenarios, taking into account islanded operation, connection to the grid, and biomass tariffs. The results show that the proposed system achieves an excellent primary energy saving performance in all the investigated scenarios, with savings of more than 94% for all the investigated scenarios. Excluding any kind of funding, in case of new investment for the system, the simple payback oscillates between 7 and 12 years, showing that the developed alternative is fairly valid with respect to traditional solutions. [ABSTRACT FROM AUTHOR]

Thermal energy storage is a key issue in efficient energy system applications, especially in renewable energies. In this respect, phase change materials (PCM) have attracted interest as an active solution for efficient energy management, particularly in the building sector. This paper presents a modelling of a PCM thermal battery in solar system assisted by heat pump. The storage stores the heat produced by unglazed solar panels (Batisol®) and releases it into a heat pump. Then this heat is sent to two other PCM storages. In this way, the low-temperature heating and domestic hot water needs of a commercial building in winter are met. The storage consists of a block of PCM contained between two plates of heat transfer fluid. It acts as a plate heat exchanger that can be charged and discharged simultaneously. The objective of the study is to dynamically simulate the thermal behaviour of this storage for different hot inlet temperature profiles. A rectangular profile is used to validate the model using experimental results. Then, a solar system assisted by heat pump and three PCM storages is dynamically simulated. This 2D model would be useful to validate a simpler model for optimising the operational parameters of the system. • PCM thermal battery acts as plate heat exchanger which can be charge and discharge simultaneously. • PCM storage model is validate using experimental results. • Three different PCM are chosen according to the temperature levels of each application. • A solar system assisted by heat pump has been dynamically simulated to supply DHW and low-temperature heating requirements. • No auxiliaries are required to meet the building's needs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Operation of water heater for simultaneous heating and hot water supply was studied. • Verification of TRNSYS mathematical model Type158 for gas condensing water heater. • Newly configured model deviations for DHW characteristics are from −2.3 % to + 0.80 % • Model for combined space heating and simultaneous hot water supply was developed. • Parametric study of water heaters operation for different types of buildings. This article presents novel insights into direct-fired water heaters with a storage tank, making a significant contribution to the scientific community. The paper has two main objectives. Firstly, it examines the possibility of reconfiguring the standard mathematical model Type 158, originally designed for indirect heated storage tanks in the TRNSYS database, for use with direct heated storage tanks. The study demonstrates that the reconfigured Type 158 model produces deviations in water temperature during charging, ranging from −2.3 % to + 0.80 % compared to the manufacturer's technical specifications. A detailed procedure for reconfiguring this model is provided, filling a gap in existing literature. Secondly, the paper uses the reconfigured model to analyse the usage of direct water heaters for dual purposes: space heating and hot water supply. System simulations in three realistic installation scenarios—single-family house, hand car wash, and apartment building—validate the findings. The first scenario evaluates the heater at very low load, the second assesses its performance with low space heating and high hot water demand, and the third highlights potential shortcomings in buildings with high space heating and hot water demand. These simulations provide valuable data on the heater's ability to meet energy supply needs in different contexts, demonstrating its practicality and effectiveness. [ABSTRACT FROM AUTHOR]

The pursuit of sustainable district heating solutions has driven a growing interest in ultra-low temperature district heating (ULTDH) systems, where booster heat pumps (BHPs) play a pivotal role despite challenges posed by their efficiency limitations under large temperature glide conditions. This paper investigates the potential of drop-in R-1234yf/R-32 zeotropic mixtures in BHPs compared to a baseline R-134a system, within the context of a ULTDH framework. This study focused on the viability of the mixtures of R-1234yf/R-32 with the composition ratio of 80 %/20 % and 90 %/10 %. The investigation reveals disparities in compressor efficiency and heat exchanger pressure drop at the component level. Device-level analysis unveils increased COP for R-1234yf/R-32 mixtures, alongside with maximum second-law efficiencies reaching 0.32. A remarkable enhancement in heating capacity up to 58 % was found. System-level analysis demonstrated exergetic efficiencies and identified preferable district heating temperatures. Exergetic efficiencies of 0.47, 0.55, and 0.59 were achieved for domestic hot water preparation at district heating supply temperatures of 30 °C, 35 °C, and 40 °C, with a subsequent shift in optimal district heating temperatures as central heating station efficiency decreased. Temperature profile analysis underscored challenges stemming from excessive subcooling, highlighting the need for configuration refinements. [Display omitted] • Drop-in application of zeotropic mixtures in booster heat pumps are studied. • Coupling effects between district heating and heat pump parameters are analyzed. • Heating capacity and COP improvements with mixture refrigerants are demonstrated. • Temperature profile analysis identified the challenges for efficiency improvement. [ABSTRACT FROM AUTHOR]

This work investigates the techno-economic performance of a hybrid photovoltaic-thermal (PVT) solar-assisted heat-pump system for covering the electrical and hot-water demands of a three-bedroom terraced house in Belfast, United Kingdom with four occupants. This system combines a water-to-water heat pump with PVT panels to deliver both electricity and hot water for domestic consumption. The PVT array provides a source of low-temperature heat for the water-to-water heat pump, while cooling the PVT array and thus preventing the electrical efficiency degradation that occurs at higher operating temperatures. Analyses have been performed for PVT arrays of different size, including 12-panel, 20-panel and 24-panel systems. Results show that, thanks to its lower initial investment cost, the most economically viable system configuration for the household considered in this work is based on a 12-panel PVT array covering a total area of 16.3 m2. This system has the potential to produce 2.4 MWh of (gross) electricity and 2.0 MWh of hot water per year, which is equivalent to just over 30% of the electrical and 80% of the hot-water demands of the household under consideration, with the PVT array acting to reduce the electricity consumption of the heat pump in the heating system by a little over 60%. The system has lower recurring yearly costs relative to current household energy systems that use electricity from the grid and natural gas, despite having higher investment costs. It is also found that the system can reduce the investigated household's annual CO 2 emissions by 910 kg per year (about 18 tonnes over a lifetime of 20 years) and that, with an electricity generation incentive rate of 5 p/kWh and a heat generation incentive rate of 21 p/kWh, the aforementioned system has a discounted payback period of 14 years. [ABSTRACT FROM AUTHOR]

In this work, a novel design of a real scale Scraped Surface Heat Exchanger (SSHE) for solar LTES has been developed and experimentally tested. The main issue in PCM heat exchangers is the growth of a solid layer at the heat transfer walls during the latent energy extraction/discharging, that lowers heat transfer. The removal of the solidified PCM through scraping increases the heat transfer rate with nearly constant heat flux. Those characteristics make it suitable for domestic hot water generation. Discharging tests have been performed in scraping and no scraping modes (SM and nSM). The heat release rate in SM has shown to be between two and three times higher than in nSM. Moreover, in SM there is a complete extraction of the available latent energy (11.9 MJ) in a short period, compared to nSM. Additionally, a performance comparison between the developed SSHE and those available in open literature has been done. The results of heat release density (4 kW/m2) and overall heat transfer coefficient (1000 W/m2K) have shown similar values, though the scraping mechanism, the rotational speed, the size and their energy capacity are different. The developed design is an appropriate technology to increase the efficiency in solar LTES. • A novel design of Scraped Surface Heat Exchanger (SSHE) with PCM has been tested. • There is a performance enhancement of the scraping over the no scraping mode. • The heat release is easily controlled during the discharging process. • The use of the SSHE allows to extract the total available latent energy. • The SSHE is a promising technology for domestic hot water generation in solar systems. [ABSTRACT FROM AUTHOR]

In the EU countries, almost 50% of the produced energy is used in residential buildings. More than 25% of this energy is used to produce domestic hot water, of which almost 80% is used to heat water in domestic hot water circulation systems. This is due to high expectations on the part of residents based on their comfort, in particular regarding the supply of heat for heating and domestic hot water. In the course of their long-term research conducted on real systems, the authors confirmed that the operation of domestic hot water distribution systems causes significant costs, mainly due to heat losses. Therefore, typical variants of energy optimization of such systems were analyzed. Tests have shown that selected solutions, such as the use of control automation, are not sufficient, and recommended additional thermal insulation may not be applicable due to technical reasons. With an aim of finding a solution to the problem, the publication analyzes operational data from an existing heat source and domestic hot water circulation system in a residential building. On the basis of these analyses, a solution was proposed to reduce energy consumption within the installation by means of its hydraulic optimization. The reduction of heat losses in domestic hot water installation by means of a method presented by the authors is estimated at approximately 20%. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

For most traditional energy sources, price increases are a current perspective; on the other hand, conventional fuels are considered responsible for global warming, with very negative estimated consequences. For these reasons, the use of more environmentally friendly energy sources, from the category of renewable sources, is required for the next period. The article presents a part of a system designed to obtain domestic hot water by combining 2 renewable sources: solar energy and biomass energy. For the conversion of energy from biomass, tests were performed in 2 constructive variants, in order to improve the performances. [ABSTRACT FROM AUTHOR]

The costs of gas transportation and its environmental/security impacts in Iran have led to evaluating geothermal/solar renewable sources instead. Regarding the high potential of geothermal/solar in Sistan/Baluchestan province, Iran, which have still no access to the global gas network, these resources create a desirable plan. This paper attempted to present/compare four possible solar-assisted ground source heat pumps to supply four purposes of electricity demand, heating/cooling, and domestic hot water. First, the energy needed in the region was designed with DesignBuilder. Then, each proposed system was modeled in Polysun software using a photovoltaic-thermal and a vertical geothermal heat exchanger. Afterward, all probable plans were evaluated and compared technically, economically, and environmentally. The results indicated that the maximum/minimum values of the coefficient of heat pump performance for direct heat exchanger and series systems were 4.39/3.87. Also, the optimal plan was introduced with 4957/10667 kWh electricity consumption/production. Besides, an economic analysis was estimated for the optimal strategy with an investment return of 7years. The designed system prevented 5089kgCO 2 emissions annually. By means of this integrating hybrid system, Sistan/Baluchestan province would become a significant renewable power plant globally, and a considerable techno-economic and environmental challenge would be dissolved in Iran. • A novel geothermal/solar hybrid system was introduced and analyzed technically, economically and environmentally. • The proposed hybrid system could supply heating/cooling/electricity demands. • One of significant challenge, non-renewable resources usage, would be dissolved in Iran by using a renewable hybrid system. • The proposed plan could reduce CO2 emissions significantly. [ABSTRACT FROM AUTHOR]

• A novel GEHP facility for cooling and domestic hot water is developed. • A novel condenser and three thermostatic expansion valves are used in the system. • The novel GEHP facility is able to maintain expected high performance. Heat pump technologies have been widely used in air conditioning and hot water application. However, most of the heat pump systems adopt an expansion valve to complete the cooling and heating modes currently. The flaw is that as the four-way valve is switched, the expansion valve cannot be guaranteed to be very close to the inlet of the evaporator in both modes, making the performance of the cooling or heating mode worse. In addition, for gas-engine-driven heat pump (GEHP), the utilization of engine waste heat is insufficient. Based on the above two shortcomings, a novel GEHP unit with an advanced finned tube heat exchanger and three thermostatic expansion valves was built in this work. The performance was evaluated under an experimental operating range of engine speed from 1300 rpm to 2000 rpm, air temperature from 23.8°C to 27.7°C, and evaporator water inlet temperature from 13.2°C to 22.4°C. Experimental results showed that when the engine speed and ambient temperature increased, the compression ratio increased, whereas the coefficient of performance (COP), primary energy ratio with heat recovery (PER 1), and primary energy ratio without heat recovery (PER 2) of the system decreased linearly. As the evaporator water inlet temperature increased from 13.2°C to 22.4°C, the COP, PER 1 , and PER 2 had an improvement of 23.6%, 20.8%, and 27.6%, respectively. The averages of COP, PER 1 and PER 2 were 3.67, 1.57 and 0.96, respectively. The results indicated that the novel GEHP unit was able to maintain expected high performance. [ABSTRACT FROM AUTHOR]

International Energy Agency reported that buildings are accountable for one-third of the global final energy demand in 2017. On-site renewable energy generation can reduce buildings' grid electricity consumptions. Medium-rise buildings located in urban areas have limited available rooftop or facade surfaces, thus solar driven technologies such as solar thermal, photovoltaics (PV) or photovoltaics/thermal (PV/T) are in competition for the available space. This investigation aims to compare available solar driven water heating systems in the market, suitable to replace the conventional electric water heater for a multi-residential building. Under the present study, solar PV electric water heating system (S1), solar thermal water heating system with electric boosting (S2), solar PV/T water heating system with electric boosting (S3) and integrated solar PV and heat pump water heating system (S4) are investigated. The performance parameters compared are the annual net electricity consumption from the grid and the net present value of life-cycle cost (LCC) for 20 years life. Results reveal that S3 and S4 have 'net' positive electricity production but higher initial costs, compared to the other systems. For buildings located in colder climates, S2 has lower LCC compared to S3 but for warmer climates the LCC of S3 is the lowest. • Solar driven water heating systems were compared with an electric water heater. • Hot water provision for an urban medium-rise residential building was investigated. • Annual net electricity consumptions and life-cycle costs were assessed. • The PV/T and PV-HPWH systems have net positive electricity production. • The solar thermal and the PV/T water heating systems have lower life-cycle costs. [ABSTRACT FROM AUTHOR]

A numerical model is developed and validated to simulate the performance of sensible energy storage (water tank) and hybrid energy storage (water tank including phase change material "PCM" modules) integrated into solar domestic hot water (DHW) system. Two configurations with direct heat exchange and indirect heat exchange using immersed heat exchangers are explored. A novel comparison is presented between both systems based on the solar fraction, which denotes the solar thermal energy contribution to the load. The effect of the storage volume on the solar fraction of the system is studied during a typical spring day while providing the hot water demands for a single-family residence, assuming a dispersed daily draw profile. The numerical results showed the crucial role of thermal stratification induced in the storage system with direct heat exchange. The storage system with direct heat exchange operates with 18–23% larger solar fraction than that with immersed coil heat exchangers. Adding PCM modules in the water tank with 50% volume fraction can yield around 40% potential reduction in the storage volume. The melting temperature of the PCM must be carefully chosen to maximize the energy storage in the latent form, thus limit the large temperature fluctuations of the system. • Numerical model for hybrid thermal energy storage with phase change materials is developed. • Experimental validation of the model yields good agreement within the measurements' uncertainty. • Storage with direct heat exchange outperforms that with heat exchanger due to stratification. • Adding phase change materials to storage tank could reduce the storage volume by 40%. • The melting temperature of the phase change material has a critical impact on the performance. [ABSTRACT FROM AUTHOR]

This paper presents and discusses results from a field test that uses model predictive control (MPC) to optimise the operation of a multi-source heat pump-based energy system for space heating and hot water provision in a building. The objective of the optimisation is to minimise the electricity consumption of the heat pump using flexibility from the heat sources, the space heating and domestic hot water tanks while ensuring end-user comfort and system constraints. The field test was performed in the context of the RES4BUILD project. The integrated system consists of photovoltaic-thermal (PVT) collectors, an advanced vapour-compression multi-source heat pump and water buffer tanks for space heating and hot water needs. The heat pump utilises a solar buffer, a borehole thermal energy storage (BTES) and air as heat sources. The solar buffer is supplied with heat from the PVT collectors. The optimal operation of the system is obtained by monitoring and controlling the interactions between the different system components using MPC, taking into account the weather and heat load forecasts. Results have shown that MPC has a potential and added value for the optimal operation of multi-source heat pumps in real-life while considering system constraints and user behaviour to ensure thermal comfort. However, significant effort and expert knowledge are needed to develop the sufficiently accurate system models required by this control approach. The outcomes and conclusions of this work are therefore a basis for further development of such control approaches to improve their replicability and feasibility on a large scale, considering the diverse nature of energy system components in buildings. [ABSTRACT FROM AUTHOR]

• A novel DWH interconnection and sharing mode is proposed. • The CEEL based dynamic energy consumption calculation models for water heater clusters is established. • Two operational strategies for optimizing economic and environmental benefits were compared. • The maximum total energy consumption can be reduced by 41.58 %. Residential buildings in China are consuming over 20 % of their operating energy on domestic hot water (DHW), a percentage that has been increasing in recent years. The use of energy-efficient water heaters is a direct solution to reduce DHW energy consumption, but high costs and installation requirements often deter households from adopting them. This issue is particularly prevalent in high-rise residential buildings, resulting in a low adoption rate of energy-efficient water heaters in China's high-rise residential sector. To address this challenge, this study proposes a DHW interconnected and sharing mode as a novel approach to enhance DHW energy efficiency in high-rise residential buildings. A dynamic performance calculation model based on the China Energy Efficiency Label (CEEL) for various types of water heaters was developed to evaluate the energy efficiency of this mode. The total energy consumption, carbon emissions, and energy costs of the building were assessed under both decentralized mode and interconnected and sharing mode. The findings indicate that implementing the interconnected and sharing mode can significantly decrease the annual total energy consumption, carbon emissions, and energy costs of DHW. Among the two operational strategies examined (economic optimal and environmental optimal), the economic optimal strategy is more suitable for China's current energy landscape. Under the economic optimal strategy, the annual total energy consumption, carbon emissions, and energy costs of DHW in the target building are reduced by 41.58 %, 27.97 %, and 34.87%, respectively. [ABSTRACT FROM AUTHOR]

This paper develops a computationally fast algorithm to disaggregate the total energy use recorded by smart heat meters into space heating (SH) and domestic hot water (DHW). The algorithm trains a regression model on SH-only hours and predicts SH for all other hours with potential DHW use. Data from smart water meters were used to identify hours with only SH. Assessing 13 regression models, an untuned random forest was identified as the best-performing regression model with an acceptable computational cost (median: 7.4 s per building). Furthermore, using one year of data from over 2400 single-family homes, it was shown that the best result (median CVRMSE: 0.13) can be obtained using only smart heat meters based regressors, increasing the applicability of the developed method. Furthermore, two tests were implemented, and it was successfully demonstrated that they identify situations where the regressors are distributed differently for hours with SH only and hours with SH and DHW, to identify possible training bias; thus, buildings where the disaggregation is potentially unreliable. Validation against data from three single-family houses with known SH and DHW use confirmed the good performance of the method and that the performance can be estimated without ground truth data via nested cross-validation. [Display omitted] • Calculation of space heating (SH) and domestic hot water (DHW) from total energy use. • Requires only hourly data from smart heat and water meters; is computationally fast. • Developed using one year's data from over 2400 single-family houses. • Method validated against ground truth data from 3 single family houses. • Accuracy estimate can be obtained without labelled known data. [ABSTRACT FROM AUTHOR]

This paper explores methodologically and theoretically how to understand variations in the temporal performances of showering as a practice-as-entity. Time-based data on domestic hot water consumption in 134 Danish households show distinctly different patterns, where some households exhibit highest consumption in the morning and others in the evening. This temporal pattern of showering is analysed based on an innovative combination of statistical cluster analysis and qualitative interviews. Focus is on the timing of showering related to sequences of other everyday practices, and to the rules, meanings and dispositions guiding this practice. From a sustainability perspective, the consumption of water and energy entailed by showering is problematic, and with increasingly intermittent renewable energy production, the timing of showering also becomes an issue. The study demonstrates that the time of showering is closely related to sequences of different practices, that dispositions and socio-demographics influence the order of sequences, and that meanings of showering may vary accordingly. However, there are also common meanings and rules related to showering across these variations, which contribute to the formation of showering as a practice-as-entity. [ABSTRACT FROM AUTHOR]

The author reports an experimental investigation of the thermal performance of a multipurpose photovoltanic (PV) solar wall with phase change material (PVSW-PCM). The PVSW-PCM configuration was made of double layers. The external layer consists of a 12 Wp photovoltaic panel attached to a 15 cm thick PCM tank integrating water pipes. The internal wall is an ordinary clear glass pane. There is an 8 cm air gap between the two layers. The PVSW-PCM was integrated into the southern side of a small house of 4.05 m3 volume built by autoclaved aerated concrete block walls 0.07 m thick. On top of the external layer, three glass blocks (3 × 0.2 × 0.2 cm²) are installed to ensure indoor illumination. The absorbed solar radiation by the PV panel and PCM heats the water in the pipes and the air in the gap. The hot water produced is stored in a 10 liters tank located near the roof. At the inner lower part (room side) and the external upper part (ambient) of the gap, a small DC fan (12 V, 0.48 A) box was installed. The fans were connected to the PV panel directly to enhance indoor ventilation. The investigation considered both natural (fans OFF) and PV assisted ventilation. Another similar house without the PVSW-PCM referred to as glass wall (GW) was built and used as a reference for comparison. The experimental results revealed that the indoor temperature of the PVSW-PCM house was considerably lower than that of the GW house. Moreover, the PVSW-PCM could produce hot water temperature of 55-62 °C and induce a ventilation rate proportional to the intensity of solar radiation. Indoor illumination was sufficient for general house use. Therefore, the PVSW-PCM offers a new alternative for architects and engineers to reduce electric energy use for producing hot water and ventilation and save electrical energy consumption of air conditioner, as the indoor temperature is lower than that of the conventional house. [ABSTRACT FROM AUTHOR]

This paper focuses on the water-energy nexus in low income households. Water, electricity and gas constitute fundamental resources for households that interplay throughout many daily activities. However, in studies on household poverty, there is a tendency to treat water and energy separately. In this contribution, we argue for the joint consideration of both forms of deprivation and present empirical evidence for the Metropolitan Area of Barcelona (AMB). In Barcelona, the dynamics between water and energy poverty in households widened the scope of institutional measures on energy poverty by incorporating water poverty as part of guaranteeing the 'right to basic utilities'. We document the interactions between the two resources through the water-energy nexus approach by combining quantitative and qualitative methodologies. Apart from presenting the expenditure-based analysis of the Spanish Survey of Income and Living Conditions, which reveals that a significant part of the population is both water and energy poor, with the results from our semi-structured interviews, we are able to demonstrate how much importance and value the affected households give to their thermal and hydric (dis)comfort, which in turn, exerts a direct impact on their daily hygiene and health. The paper also highlights institutional and socio-technical perspective as the differences in ownership and regulatory status of both resources cause discordances in public efforts to alleviate the status of the water and energy poor. [ABSTRACT FROM AUTHOR]

• Calibration of models using smart-meter data and basic building characteristics. • Separation of district heating into space heating and domestic hot water components. • Use of priors in Bayesian calibration framework to address data-related uncertainty. • Performance showcased in case study modelling 159 residential single-family houses. • Models used to investigate demand response schemes aimed at peak reduction. Several studies have indicated a potential to exploit the thermal inertia of individual residential buildings for demand response purposes using model predictive control and time-varying prices. However, studies that investigate the response obtained from applying these techniques to larger groups of buildings, and how this response affects the aggregated load profile, are needed. To enable such analysis, this paper presents a modelling methodology that enables bottom-up modelling of large groups of residential buildings using data from public building registers, weather measurements, and hourly smart-meter consumption data. The methodology is based on describing district heating consumption using a modified version of the building energy model described in ISO 13790 in combination with a model of the domestic hot water consumption, both of which are calibrated in a Bayesian statistical framework. To evaluate the performance of the methodology, it was used to establish models of 159 single-family houses within a residential neighbourhood located in the city of Aarhus, Denmark. The obtained bottom-up model of the neighbourhood was capable of predicting the aggregated district heating consumption in a previously unseen validation period with high accuracy: CVRMSE of 5.58% and NMBE of −1.39%. The model was then used to investigate the effectiveness of a simple price-based DR scheme with the objective of reducing fluctuations in district heating consumption caused by domestic hot water consumption peaks. The outcome of this investigation illustrates the usefulness of the modelling methodology for urban-scale analysis on demand response. [ABSTRACT FROM AUTHOR]

• Application of Model predictive control to a residential single-family building • Coupling of thermal and electric supply by an air source heat pump with part load capability • Simultaneous control of domestic hot water, space heating and a battery storage • Feasibility of efficient control by development of distributed MPC algorithms • Operational cost reduction of 11.6% compared to PID-control in annual simulations This article investigates the potential of economic model predictive control of complex residential energy systems with electric coupling to the public grid. The examined system includes a battery energy storage system, photovoltaic power generation, an air-to-water heat pump, thermal energy storage and a building model. The said power generation provides energy for electric loads as well as domestic hot water and space heating. Model predictive control algorithms manage the energy system by nonlinear global optimization. Within this optimization, a time-varying state space model, which is derived from the energy system simulation model, reflects the system dynamics. Owing to the resulting high complexity, two algorithms for distributed model predictive control are developed. In addition, the developed approaches are compared to a common reference control concept as well as centralized model predictive control. For the comparison of annual operational costs, current German energy prices and subsidies are implemented into the economic calculation. Results show an improved performance of the developed approaches with 11.6% cost reduction in comparison to the reference. This is achieved through an increase of the heat pump seasonal performance factor by 3.4%, reduced curtailment of electrical photovoltaic energy to 21.5% of the reference value and prevention of auxiliary heater operation. Furthermore, increased photovoltaic self-consumption by the heat pump results in a slight reduction of battery storage operation. In conjunction with monetary and energetic advantages, model predictive control increases the comfort in regards to the violation of minimum limits for the comfort criteria. [ABSTRACT FROM AUTHOR]