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This study investigates a novel approach to reduce energy consumption in large commercial buildings by recovering waste heat from the condenser of a chiller and utilizing it to preheat domestic hot water (DHW). While numerous energy-saving strategies have been developed for building heating and cooling systems, the energy efficiency of DHW systems has lagged behind due to the increasing demand for hot water driven by improving living standards and hygiene concerns. By integrating a heat exchanger between the chiller and the DHW system, the proposed system effectively improves the chiller's performance and significantly reduces the energy consumption of the DHW heater. Simulation results demonstrate that during the cooling season (June–August), the chiller achieved a 3% reduction in energy consumption, while the DHW heater experienced energy savings exceeding 70%. Additionally, the operating frequency of the DHW heater was substantially decreased. Notably, despite the significantly higher energy consumption of the chiller compared to the DHW heater, the reduction in greenhouse gas emissions from the DHW heater accounted for more than 50% of the total reduction. This finding highlights the significant contribution of energy savings in the natural gas-fired DHW heater to improving the building's overall sustainability. [ABSTRACT FROM AUTHOR]

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]

Phase Change Materials (PCMs) are one of the most promising materials for storing thermal energy and supplying stored energy for Domestic Hot Water (DHW) applications. This paper presents a detailed numerical analysis to describe transient heat transfer in a phase-change composite thermal energy-storage system. The composite was composed of 92.5 % stearic acid, 7.5 % carbon fiber, and a heat transfer fluid (ethylene cellulose). Numerics were implemented using ‘The Integrated Computer Engineering and Manufacturing code for Computational Fluid Dynamics’. The results were validated using experimental data and demonstrated acceptable agreement and an accurate representation of this specific transient heat transfer problem. The difference between the simulation and experimental results was so small that we considered the simulation results reliable. When the phase change heat storage process is about 800 s, the heat is transferred to the entire phase change heat storage tank, and when the phase change heat storage process is about 10800s, the temperature of all composite phase change materials reaches the phase change temperature. When the phase change heat storage process is about 8 h, the temperature of the composite phase change material in the whole phase change heat storage tank reaches 90 ℃. The temperature tends to be stable after the phase transition heat release process for about 500 s, and there is no large fluctuation in temperature with the passage of time. When the phase change heat release process reaches 7200 s, the cold-water inlet temperature is 15 ℃, 20 ℃ and 25 ℃, and the outlet temperature is 25.8 ℃, 30.8 ℃ and 35.7 ℃, respectively, indicating that the application of composite phase change materials in phase change heat storage water tank has a good effect.

The use of solar water heaters (SWHs) in building facades in the Middle East region can significantly reduce energy consumption and carbon emissions. It can also reduce residents' electricity bills and provide a reliable source of hot water. Based on conducted studies, for the first time, the dynamic technical-energy-economic-environmental analysis of SWHs has been carried out in 17 countries in the Middle East region using TSOL PROS software. The use of accurate calculation of space heating requirements, among other differentiations from previous work, ensures that the results of this study are highly reliable and realistic. According to the results, Kuwait, Qatar, and Saudi Arabia have been identified as the most suitable countries because they have a higher percentage of heat supplied by solar energy. Turkey, Iran, and Jordan are considered less suitable countries. The average heat supply provided by SWHs in this region is 65.3%, which prevents the emission of more than 23 tons/year of CO2 pollutants. [ABSTRACT FROM AUTHOR]

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Currently, many opportunities for real energy and cost savings are missed, primarily due to the perception of quantitative heat recovery. However, in the context of the need for the energy efficiency of buildings and technological processes, the recovery and valorisation of residual energy will be a key element. For this reason, the article analyses the recoverable potential from residual energy from various sources and proposes a way to capitalize on it for heating/cooling buildings and preparing domestic hot water. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to analyses the solutions for the heating and domestic hot water supply system for a modernized hotel in the city of Chisinau for the climatic conditions of the Republic of Moldova. In the paper, the implemented solutions were analyses, the investment recovery term was determined. The Republic of Moldova does not have its own energy sources, and the need to implement alternative sources is obvious. In this sense, the use of heat pumps, photovoltaic panels form an energy efficient, economical and more ecological system than any thermal energy generating installation [ABSTRACT FROM AUTHOR]

South Africa currently has the highest carbon emission intensity per kilowatt of electricity generation globally, and its government intends to reduce it. Some of the measures taken by the government include a reduction of emissions in the building sector using solar water heating (SWH) systems. However, there is currently no study in the country that comprehensively assesses the technical, economic, and environmental impact of SWH systems across the country. This study therefore used the System Advisor Model (SAM) to model two different technologies of SWH systems (i.e., flat plate (FPC) and evacuated tube (EPC) SWH) at five different locations (i.e., Pretoria, Upington, Kimberley, Durban, and Cape Town) strategically selected across the country. According to the study, the optimum azimuth for both the evacuated tube and flat plate SWH system in South Africa is 0°. Installing FPC and EPC at the different locations would yield payback periods of 3.2 to 4.4 years and 3.5 to 4.3 years, respectively. Comparably, levelized cost of energy for the FPC and EPC will range from 7.47 to 9.62 cents/kWh and 7.66 to 9.24 cents/kWh, respectively, based on where the SWH system is located. Depending on where the facility is located, the annual cost savings for the FPC system would be between $486 and $625, while the EPC system would save between $529 and $638. Using SWHs can reduce CO2 emissions by 75–77% for the evacuated tube system and 69–76% for the flat plate system annually, depending on the location.

Domestic hot water installations provide an ideal habitat for Legionella spp. and pose a potential risk of human infection. Heating the water is considered the major preventive measure against Legionella contamination. Our study aimed to understand better the relationships between hot water temperatures and Legionella spp. occurrence within such systems. We utilized routine monitoring data from public and apartment buildings, comprising 292,937 data sets. We employed the analysis of variance, receiver operating characteristic analysis, and relative probability of occurrence to quantitatively assess statistical relationships. In the case of supply flow (SF) and return flow (RF), i.e. near the water heater, water temperature strongly regulates Legionella spp. growth. Below calculated tipping points (SF: 56 °C, RF: 53 °C), the relative probability of Legionella spp. occurrence is 18.7 and 7.5 times higher, respectively. For peripheral samples, the relationship between temperature and Legionella spp. occurrence is less pronounced. Additionally, statistical relationships between central and peripheral temperatures, as well as between central temperatures and peripheral Legionella spp. concentrations within one system, were weak or zero, respectively. Thus, the central temperature regime of hot water systems alone is insufficient to control the occurrence of Legionella spp. in the periphery. HIGHLIGHTS The periphery (P) in the domestic hot water system shows the highest frequency and concentrations of Legionella spp.; Temperature is a valuable predictor for Legionella spp. growth in central parts of hot water systems (supply flow and return flow) but needs to be supported by other factors in the P.; The central temperature regime of hot water systems is insufficient to explain the occurrence of Legionella spp. in the P.;

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]

In a residential building, the integration of thermal modules from the design phase can bring multiple benefits in terms of energy efficiency and thermal comfort. The article deals with a brief comparison between the traditional heating system and the decentralized system with apartment thermal modules by making the preparation of the thermal agent for heating and domestic hot water more efficient. The study was carried out following the new nZEB requirements regarding the obligation for all new buildings and those undergoing renovation to ensure a percentage of at least 30% from renewable sourcess. [ABSTRACT FROM AUTHOR]

The present study aims to assess the technical feasibility of a novel Metal Hydride-based Solar Thermal Collector (MH-STC) system. This system includes a flat-plate solar collector integrated with a metal hydride bed, a hydrogen compressor, a photovoltaic panel, a hydrogen tank, and a water storage tank. This system combines the principles of a conventional solar thermal collector with the energy storage capabilities of metal hydrides, enabling the storage of surplus thermal energy. The LaNi5 alloy was used as heat storage material. A 3D-mathematical model is established and a numerical code written in Fortran-90 is developed to simulate the dynamic behavior of the proposed solar thermal collector. It was shown that the developed 3D-model produces computational results that are consistent with experimental data. In addition, to check the accuracy of the mathematical model and numerical approach, the relative errors in the mass balance and energy balance were calculated and values of 0.054 % and 0.18 %, respectively, were obtained.The simulation results offer insights into the system's technical feasibility, revealing an overall efficiency of 90.6 %, the water temperature at the collector outlet can reach 357.3 K, and a water volume heated of 230.4 L under the considered operating conditions. Moreover, the results indicate that the proposed MH-STC system exhibits significant potential as a viable alternative for thermal storage in domestic hot water systems.

The energy sector is the main source of greenhouse gases, so it has the highest potential for improvement. The improvements can be achieved by generating energy from renewable sources. It is necessary to combine production from renewable sources with storage systems. Thermal energy storage using concentrated solar power systems is a promising technology for dispatchable renewable energy that can guarantee a stable energy supply even in remote areas without contributing to greenhouse gas emissions during operation. However, it must be emphasised that greenhouse gases and other impacts can occur during the production process of concentrating solar system components. This paper analyses the receiver design to produce thermal energy for the existing CSP dish plant at the Energy Center of the Politecnico di Torino. The plant is designed to produce electrical energy in the spring and summer periods. In addition to this energy production, the CSP can be adopted to produce thermal energy, through hot water, during the less favourable periods of the year in terms of global solar radiation. The surface heat flux is calculated in the first part of the analysis to obtain the maximum internal temperature in the receiver, which is 873.7 °C. This value is a constraint for the choice of material for the solar receiver. A life cycle assessment is performed to compare the emissions generated during the production of the main components of the CSP system with the emissions generated by the methane-fuelled water heater to produce the same amount of thermal energy. It can be concluded that the production of the main components of the CSP system results in lower greenhouse gas emissions than the operational phase of a conventional system. Given the assumptions made, the utilization of methane leads to the emission of approximately 12,240 kg of CO2, whereas the production of the CSP system results in emissions totalling 5332.8 kg of CO2 equivalent

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]

The use of greywater heat exchangers (GHEs) is an effective way to reduce energy consumption for heating domestic water. However, the available characteristics of this type of device are often insufficient and consider only a few selected parameters of water and greywater, which results in the need to look for tools enabling the determination of the effectiveness of GHEs in various operating conditions with incomplete input data. The aim of this paper was to determine the usefulness of artificial neural networks (ANNs). For this purpose, comprehensive experimental tests were carried out on the effectiveness of the horizontal heat exchanger, taking into account a wide range of water and greywater flow rates and temperatures of these media, as well as the linear bottom slope of the unit, which allowed for the creation of a database of 32,175 results. Then, the feasibility of implementing the full research plan was assessed using ANNs. The analysis showed that the impact of the media temperatures on the heat exchanger effectiveness values obtained using ANNs is limited, which makes it possible to significantly reduce the number of necessary experiments. Adopting only three temperature values of at least one medium allowed the generation of ANN models with coefficient values R2 = 0.748–0.999 and RMSE = 0.077–1.872. In the case of the tested GHE, the slope and the flow rate of the mixed water are of key importance. However, even in the case of parameters of significant importance, it is possible to reduce the research plan without compromising the final results. Assuming five different values for each of the four input parameters (a total of 625 combinations) made it possible to generate an ANN model (R2 = 0.993 and RMSE = 0.311) with high generalization ability on the full research plan covering 32,175 cases. Therefore, the conducted analysis confirmed the usefulness of ANNs in assessing the effectiveness of GHEs in various operating conditions. The approach described in this paper is important for both environmental and economic reasons, as it allows for reducing the consumption of water and energy, which are necessary to carry out such scientific research. [ABSTRACT FROM AUTHOR]

The energy sector is the main source of greenhouse gases, so it has the highest potential for improvement. The improvements can be achieved by generating energy from renewable sources. It is necessary to combine production from renewable sources with storage systems. Thermal energy storage using concentrated solar power systems is a promising technology for dispatchable renewable energy that can guarantee a stable energy supply even in remote areas without contributing to greenhouse gas emissions during operation. However, it must be emphasised that greenhouse gases and other impacts can occur during the production process of concentrating solar system components. This paper analyses the receiver design to produce thermal energy for the existing CSP dish plant at the Energy Center of the Politecnico di Torino. The plant is designed to produce electrical energy in the spring and summer periods. In addition to this energy production, the CSP can be adopted to produce thermal energy, through hot water, during the less favourable periods of the year in terms of global solar radiation. The surface heat flux is calculated in the first part of the analysis to obtain the maximum internal temperature in the receiver, which is 873.7 °C. This value is a constraint for the choice of material for the solar receiver. A life cycle assessment is performed to compare the emissions generated during the production of the main components of the CSP system with the emissions generated by the methane-fuelled water heater to produce the same amount of thermal energy. It can be concluded that the production of the main components of the CSP system results in lower greenhouse gas emissions than the operational phase of a conventional system. Given the assumptions made, the utilization of methane leads to the emission of approximately 12,240 kg of CO2, whereas the production of the CSP system results in emissions totalling 5332.8 kg of CO2 equivalent [ABSTRACT FROM AUTHOR]

In the context of the acceleration of the need to store and process data and digital telecommunications, which leads to an increase in global electricity consumption and greenhouse gas emissions, the need for research to find reliable, efficient, and cost-effective solutions to reduce energy consumption and the recovery of the residual heat produced by the data centres is an increasingly urgent one. The article presents aspects that refer to the recovery of residual energy from data centres and its use for the preparation of domestic hot water, but also for the preparation of the thermal agent necessary for heating installations in buildings and respectively modern heating systems, with the mention that the latter work at a low temperature regime. [ABSTRACT FROM AUTHOR]

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.

This study analyzes research trends on photovoltaic–thermal (PVT) systems used in buildings. The applications of PVT systems are also classified into system design, material and fluid types, and operating methods. Although many studies proposed new types of PVT systems and applications to improve system performance, there are few reports on the design and operating methods for the system, which consists of the PVT system and hot water storage tank in real-scale buildings. Therefore, our research team conducted a quantitative evaluation of a small household with a PVT system and hot water storage tank installed, according to design factors. The results of the parametric study showed that electricity production was more sensitive to changes in system capacity than those in heat production. By contrast, the change in heat production was dominant in response to the change in the installation angle and load profile of domestic hot water. Through energy simulation, it was found that the PVT system could provide 95% of the annual thermal energy for the domestic hot water consumption of the target buildings.

The seamless coexistence of distributed photovoltaics (PV) with the utility network may be maintained by focusing on higher energy autonomy of micro-grids.This may be approached by seeking any opportunities to increase local energy consumption, especially when legal regulations are cutting-down the benefits for energy overproduction.The microgrids combining PV with electric storage and heat pumps largely fail at satisfying local energy needs autonomously in winter periods and create excessive load of power network. Although the all-electric microgrid is a long term target, any improvements to the existing residential infrastructure with mixed-supply sources are worth revisiting as low-cost steps towards more conscious energy utilization.The concept of using Domestic Hot Water (DHW) heating to dump locally the excess of PV-energy is affordable method to improve energy autonomy of residential microgrids with minimal interference to their existing configuration and the advantage of no additional energy demand.The use of PV for DHW heating was studied in various configurations, but in contrast to former works, this paper presents the parametric analysis focusing on increasing the local consumption (goal A), minimizing the interference with utility grid (goal B) and optimal adjustment to net-metering accounting rules (goal C).The case study is the residential-type micro-grid in climate of Central Europe. The study uses both simulated (energy consumption profiles) and recorded (solar irradiance) data. The simulation is based on microgrid proportions and provides the results beyond reach of single experiments and conclusions applicable to similar cases, regardless the absolute size.

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]

Building energy modeling plays an important role in analyzing the energy efficiency of the existing building stock, helping in enhancing it by testing possible retrofit scenarios. This work presents an urban scale and place-based approach that utilizes energy performance certificates to develop a statistical energy model. The objective is to describe the energy modeling methodology for evaluating the energy performance of residential buildings in Milan; in addition, a comprehensive reference dataset for input data from available open databases in Italy is provided—a critical step in assessing energy consumption and production at territorial scale. The study employs open-source software QGIS 3.28.8 to model and calculate various energy-related variables for the prediction of space heating, domestic hot water consumptions, and potential solar production. By analyzing demand/supply profiles, the research aims to increase energy self-consumption and self-sufficiency in the urban context using solar technologies. The presented methodology is validated by comparing simulation results with measured data, achieving a Mean Absolute Percentage Error (MAPE) of 5.2%, which is acceptable, especially considering city-scale modeling. The analysis sheds light on key parameters affecting building energy consumption/production, such as type of user, volume, surface-to-volume ratio, construction period, systems' efficiency, solar exposition and roof area. Additionally, this assessment attempts to evaluate the spatial distribution of energy-use and production within urban environments, contributing to the planning and realization of smart cities. [ABSTRACT FROM AUTHOR]

Water heating is a significant part of households' energy consumption, and tankless gas water heaters (TGWHs) are commonly used. One of the limitations of these devices is the difficulty of keeping hot water temperature setpoints when changes in water flow occur. As these changes are usually unexpected, the controllers typically used in these devices cannot anticipate them, strongly affecting the users' comfort. Moreover, considerable water and energy waste are associated with the long-time response to cold starts. This work proposes the development of a model predictive control (MPC) to be deployed in low-cost hardware, such that the users' thermal comfort and water savings can be improved. Matlab/Simulink were used to develop, validate and automatically generate C code for implementing the controller in microcontroller-based systems. Hardware-in-the-loop simulations were performed to evaluate the performance of the MPC algorithm in 8-bit and 32-bit microcontrollers. A 6.8% higher comfort index was obtained using the implementation on the 32-bit microcontroller compared to the current deployments; concerning the 8-bit microcontroller, a 4.2% higher comfort index was achieved. These applications in low-cost hardware highlight that users' thermal comfort can be successfully enhanced while ensuring operation safety. Additionally, the environmental impact can be significantly reduced by decreasing water and energy consumption in cold starts of TGWHs. [ABSTRACT FROM AUTHOR]

This paper evaluates the energy operational performance of a system to produce domestic hot water, from the use of waste heat in a centralized air conditioning system in a hotel in Cuba. The hotel facility has two different chillers capacities, where the system recovers the condensed heat, through a heat exchanger at the compression process outlet. These schemes allow the simultaneous production of air conditioning and Domestic Hot Water, also those considering thermal storage tanks. The system modelling starts analyzing its components and their processes, based on the traditional thermodynamics and heat transfer equations and ends with a validation process. This model estimates a wide range of operating conditions, such as thermal demands of the cooling load, the chiller water temperature, the electricity consumed by chillers, and the climatological variables involved. The system is evaluated in the highest tourism season in Cuba during a year under partial load. Results were validated in a hotel as a study case, which allowed us to estimate the thermal potential available in the plant to meet the thermal demand of the hot water required, as well as showing that variations in the chiller operation affect the temperature stability in the hot water system.