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To investigate the impact of blending natural gas with hydrogen on the combustion performance of partially premixed gas water heaters, a framelet-generated manifold (FGM) was employed for lower-order simulation of combustion processes. Coupled with the 30-step methane combustion mechanism simplified by GRI3.0, a three-dimensional computational fluid dynamics (CFD) simulation of the combustion chamber of a partially premixed gas water heater was carried out. A numerical simulation was performed to analyze the combustion process of a mixture including 0–40% natural gas and hydrogen in the combustion chamber of a partially premixed gas water heater. The results indicate that the appropriate hydrogen blending ratio for some premixed gas water heaters should be less than 20%. Furthermore, it was observed that after blending hydrogen, there was a significant increase in the combustion temperature of the water heater. Additionally, there was a slight increase in NOx. [ABSTRACT FROM AUTHOR]

Thermoacoustic air-to-water air source heat pumps (TAWASHP) are the eco-friendly, simple, compressor less, low cost and likely looking future substitute for the existing compressor-based heat pumps. In this work, the design optimization of the 1-kW TAWASHP with helium for the temperature difference of 15 to 70 K for pumping heat from the atmospheric air to water using the linear thermoacoustic concepts was discussed. The optimized design can fit for both cooling and water heating applications without wasting the heat rejection to the surrounding atmosphere, rather supplied to the insulated hot water tank. The optimized one-fourth wavelength resonator TAWASHP shows the coefficient of performance of 1.1 to 2.34. The theoretical results are validated with the DeltaEC software results, and the results are in concurrence with each other. The DeltaEC predicts the TAWASHP can supply 1.55 to 3.35 kW of heat to water, which is equivalent to 37.3 to 80.3 kWh of heat energy per day. [ABSTRACT FROM AUTHOR]

This study focused on assessing the financial efficiency of investing in a horizontal shower heat exchanger. The analysis was based on net present value (NPV). The research also examined the possibility of using artificial neural networks and SHapley Additive exPlanation (SHAP) analysis to assess the profitability of the investment and the significance of individual parameters affecting the NPV of the project related to installing the heat exchanger in buildings. Comprehensive research was conducted, considering a wide range of input parameters. As a result, 1,215,000 NPV values were obtained, ranging from EUR −1996.40 to EUR 36,933.83. Based on these values, artificial neural network models were generated, and the one exhibiting the highest accuracy in prediction was selected (R2 ≈ 0.999, RMSE ≈ 57). SHAP analysis identified total daily shower length and initial energy price as key factors influencing the profitability of the shower heat exchanger. The least influential parameter was found to be the efficiency of the hot water heater. The research results can contribute to improving systems for assessing the profitability of investments in shower heat exchangers. The application of the developed model can also help in selecting appropriate technical parameters of the system to achieve maximum financial benefits. [ABSTRACT FROM AUTHOR]

User requirements serve as the primary reference content in product design. The effective capture of crucial user requirements, followed by the development of a product technical solution aligned with these requirements, stands as a pivotal approach to enhancing design efficiency. In order to explore the problem of generating and decision-making of product technical solutions in the case of complex user demands, this study constructs a user requirements driven product optimization design model, which is used to complete the generation and decision-making of product design solutions in a more reasonable way. The model unfolds across three key stages: Firstly, a user requirements importance ranking system is crafted leveraging Kano Model and Pairwise Analysis. Next, employing the Functional Analysis System Techniques (FAST) theory and the Quality Function Deployment (QFD) theory, user requirements undergo transformation into technical solutions. Finally, these technical solutions are amalgamated into diverse technical combinations, with decisions facilitated by a game theory model to yield the optimal overall design solution. The new optimal design model reduces the influence of subjectivity and ambiguity in the process of user requirements analysis, increases the reliability of the transformation of user requirements into technical solutions, and improves the efficiency of the generation and decision-making of product design solutions under multiobjective situations. The model proposed in this study is exemplified through the development of a medicated bath water heater. Results indicate that the technical solution derived from the model surpasses similar products in terms of user satisfaction, thereby validating its feasibility. [ABSTRACT FROM AUTHOR]

Featured Application: The main application of this paper is to review and improve a model that enables the use of water heaters by small electricity customers in electricity markets and services in the short and medium term. For this goal, it is necessary to review the service of loads to avoid customer discomfort and the way control mechanisms work, usually thermostats. To guarantee a minimum level of accuracy in the flexibility of the response, the understanding of heat and electric processes in the load is a cornerstone for the participation of these appliances. This must be done by comprehensive validation of the model in different conditions, including water draws, temperature, and load control. To exemplify the potential of the model, an application in a prosumer scenario is presented. Residential segments are of the greatest interest from the point of view of Demand-Side Resources and Decarbonization. Main end-uses such as water heaters, heating, and cooling have interesting opportunities: first, they can store energy, and this is relevant for the integration of renewables. Second, they are candidates for efficiency and electrification, increasing their demand share and the flexibility of demand. This paper aims to formulate an elemental Physical-Based Heat Pump Water Heater model that will enable the use of these energy-efficient appliances through aggregation in complex products, considering the advantages for demand and supply sides. Simulation results show that the individual performance is quite accurate and that the proposed model is flexible enough to be used to take more profit from energy markets or to easily respond to fast-occurring events. The model can be easily aggregated and used to obtain baselines, an important point for Demand Response evaluation. Results also demonstrate that demand–supply coordination and balance can be improved using these models to reduce or mitigate the risks and volatility of renewables without inducing a noticeable loss of service. Consequently, the contribution of this responsive load can be modelled through this methodology, making the engagement of more customer segments in Demand Response policies more credible and deploying new segments, such as prosumers. [ABSTRACT FROM AUTHOR]

Domestic hot water heaters are considered to be easily integrated as flexible loads for demand response. While literature grows on reproducible simulation and lab tests, real-world implementation in field tests considering state estimation and demand prediction-based model predictive control approaches is rare. This work reports the findings of a field test with 16 autonomous smart domestic hot water heaters. The heaters were equipped with a retrofittable sensor/actuator setup and a real-time price-driven model predictive control unit, which covers state estimation, demand prediction, and optimization of switching times. With the introduction of generic performance indicators (specific costs and thermal efficiency), the results achieved in the field are compared by simulations to standard control modes (instantaneous heating, hysteresis, night-only switching). To evaluate how model predictive control performance depends on the user demand prediction and state estimation accuracy, simulations assuming perfect predictions and state estimations are conducted based on the data measured in the field. Results prove the feasible benefit of RTP-based model predictive control in the field compared to a hysteresis-based standard control regarding cost reduction and efficiency increase but show a strong dependency on the degree of utilization. [ABSTRACT FROM AUTHOR]

In this paper, a combined air/water source heat pump water heater is presented. At ordinary time, the heater can be used for hot water heating in water-source mode to improve the energy efficiency. While in cold season, it gives priority to air-source mode for water heating to improve operational safety. Experiments were conducted to investigate the thermodynamic performance of the heater in each operation mode, and the experiment results were analyzed. The research indicated that its operation was reliable during the long-time running. This paper offers a promising energy-saving method in future. [ABSTRACT FROM AUTHOR]

Heat exchangers, as essential devices for facilitating heat transfer, have found a variety applications in various industries. However, the occurrence of corrosion-related failures in real-world scenarios remains a prevalent problem that can lead to catastrophic incidents. This paper investigates the problem of corrosion perforation on the outlet flange of a heat exchanger in a sour steam stripper from a petrochemical company. Failure analysis was performed using physical testing and chemical analysis, metallographic examination, microscopic observation, and energy spectrum analysis. Intergranular corrosion experiments and flow calculations were performed to verify the analysis. The results indicate that the main cause of the flange corrosion perforation was the formation of a highly concentrated NH4HS aqueous solution during the cooling process of the NH3, H2S, and water vapor in the fluid passing through the heat exchanger, and the velocity was too high, which triggered alkali-sour water washout corrosion. To prevent the recurrence of similar corrosion perforations, recommendations for material and process optimization are proposed to effectively reduce the safety production risks in refinery units and provide valuable information for the safe long-term operation of a sour steam stripper. [ABSTRACT FROM AUTHOR]

Shutdowns of photovoltaic installations are a problem that has been increasingly affecting private investors who have built home installations of several to a dozen kWp over the last few years. This problem, most often caused by outdated infrastructure, appears in many countries and impacts energy production. This work focuses on three aspects of the problem. The first one answers the question of how shutdowns of the photovoltaic installation affect production, and how significant the energy loss happens when the PV inverter is not working or is in the restart phase. The second aspect proposes an original, low-cost method that reduces the number of shutdowns. This method relates to the auto-consumption mechanism associated with domestic water heaters and the system for measuring voltage and energy consumption from the electrical network. The solution is based on constant monitoring of the network voltage and the switching of heaters based on a dedicated algorithm. Additionally, continuous analysis also allows for reporting observed irregularities to the electricity supplier. The third and final factor corresponds to the real impact of shutdowns on the long-term aspect of the investment and the extension of its payback period, and to what extent the proposed solution shortens this period. Through a detailed analysis on the issue of shutdowns, the proposed solution allows for a reduction in the number of shutdowns by over 40%. However, due to the fact that it discusses a specific case, this solution requires a calibration and adjustment process, which is discussed in the article. [ABSTRACT FROM AUTHOR]

This paper reviews the stability, heat transfer efficiency and photothermal conversion efficiency optimization studies of solid-liquid phase change materials (PCM) applied to water heaters. Suggestions and prospects were proposed. The study shows that the solid-liquid PCM are mostly filled in the water tank, thermal storage devices or solar thermal collector heater system with paraffin wax, and the addition of solid-liquid PCM can significantly improve the water heater performance. Further in-depth research is needed on PCM dosage and system economics of their application in heat pump water heaters, and the application of photothermal conversion PCM in solar water heater systems. [ABSTRACT FROM AUTHOR]

The share of renewable energy share in India's energy mix of India has been increasing recently owing to the promotion and implementation of various government policies that promote the use of renewable sources of energy, depleting fossil fuel levels, increasing fuel prices, and stringent laws for emission reduction worldwide. The increase in the use of solar-evacuated-tube-collector-based domestic water heating is the result of this transition from conventional to nonconventional sources of energy. The recent urban agglomeration is challenging to install these solar water heaters in every household because the roof space is limited. Space reduction can be achieved by reducing the collector area by varying the diameter of the evacuated tubes. This study used a single tube and tank arrangement model with a fixed inclination to achieve a thermosyphon effect in a solar water heating system with three different diameter configurations of 48 mm, 54 mm, and 72 mm, with a tube measuring 1800 mm in length. Thermal assessment of the thermosyphon-based evacuated tube-solar water heater using the ANSYS CFD simulation software involves measuring the temperature at three different positions in the tank to study the thermosyphon initialization. This study signifies that the 72-mm-diameter evacuated tube is more capable of initializing the thermosyphon effect in the system. Nevertheless, the final temperature of the system is better achieved in the 48-mm-diameter evacuated tube. [ABSTRACT FROM AUTHOR]

To achieve the flexible operation of the active distribution network (ADN), an optimal control method for the ADN considering the soft open point (SOP) and thermostatically controlled loads under distributed photovoltaic (PV) access is proposed. First, the mathematical model of the SOP and thermostatically controlled loads are constructed based on the flexibility of the SOP and the thermal storage characteristic of thermostatically controlled loads, respectively. Then, the mathematical model of theADNconsidering the SOP and thermostatically controlled loads are further constructed. The optimal control of the ADN is realized by adjusting the transmission power of the SOP and the switching state of the electric water heater. Finally, the optimal operation analysis of the SOP and thermostatically controlled loads under various control methods is carried out, and the impact of the SOP and thermostatically controlled loads on the economic and secure operation of the ADN is further investigated. The results show that the proposed method taps the demand response potential of thermostatically controlled loads while satisfying the water consumption habits of different customers, and utilizes the network reconfiguration with the SOP to further improve the security and economy of the ADN operation. [ABSTRACT FROM AUTHOR]

To improve the heat transfer coefficient of a condenser, this paper proposes using a fin-tube condenser to replace a smooth-tube condenser in a domestic heat pump water heater. The finite element method is used to analyze the heat transfer coefficient of fin-tube condensers with different design parameters. By comparing the results of experiments with those obtained using CFD methods, it has been determined that the CFD method used in this study is feasible. Simulation results showed that the heat transfer coefficient enhanced clearly. The total thermal resistance of the fin-tube condenser decreased by 7% through increasing fin thickness. The total thermal resistance of the fin-tube condenser increased by 1–1.3% when fin spacing was increased. The heat transfer coefficient decreased severely and the maximum total thermal resistance of the fin-tube condenser increased by 8.7% with increasing fin height. In 600 s, when the fin spacing, fin height, fin thickness and inner diameter were 14 mm, 12.5 mm, 1.2 mm and 22.5 mm, respectively, compared to the smooth-tube condenser, the fin-tube condenser could increase the final water temperature by 18.37%, and the heat transfer coefficient would increase by about 95%. This research could provide a low-cost way to improve the heat transfer coefficient of condensers in domestic heat pump water heaters. [ABSTRACT FROM AUTHOR]

Technically, residential energy management systems are fundamental sectors in the smart grids for implementing demand response programs in the layer of households for managing energy consumption and reducing energy bills. The paper proposes a novel energy management scheme that takes production and usage into account based on a heuristic searching operation. In addition to modelling the grid, renewable energy sources, batteries, and electric vehicles, various kinds of electrical and thermal devices have been examined, including air conditioners, water heaters, vacuum cleaners etc. A method is developed for solving the objective constraint issue in a smart home in order to reduce energy consumption and determine feasible operation states among the various loads. Moreover, this paper proposes a grey wolf optimization method for solving the issue over a longer simulation period. Various cases were examined to evaluate the effectiveness of this suggested robust optimization algorithm. The outcomes show that the suggested model could not only reduce energy costs significantly but has also shown good performance for energy management purposes. [ABSTRACT FROM AUTHOR]

Evaluations of nonintrusive load monitoring (NILM) algorithms and technologies have mostly occurred in constrained, artificial environments. However, few field evaluations of NILM products have taken place in actual buildings under normal operating conditions. This paper describes a field evaluation of a state-of-the-art NILM product, tested in eight homes. The match rate metric—a technique recommended by a technical advisory group—was used to measure the NILM's success in identifying specific loads and the accuracy of the energy consumption estimates. A performance assessment protocol was also developed to address common issues with NILM mislabeling and ground-truth comparisons that have not been sufficiently addressed in past evaluations. The NILM product's estimates were compared to the submetered consumption of eight major appliances. Overall, the product had good performance in disaggregating the energy consumption of the electric water heaters, which included both electric resistance and heat-pump water heaters, but only a fair accuracy with refrigerators, dryers, and air conditioners. The performance was poor for cooking equipment, furnace fans, clothes washers, and dishwashers. Moreover, the product was often unable to detect major loads in homes. Typically, two or more appliances were not detected in a home. At least two dryers, furnace fans, and air conditioners went undetected across the eight homes. On the other hand, the dishwasher was detected in all homes where available or monitored. The key findings were qualitatively compared to those of past field evaluations. Potential areas for improvement in NILM product performance were determined along with areas where complementary technologies may be able to aid in load-disaggregation applications. [ABSTRACT FROM AUTHOR]

The paper presents a cause-and-effect analysis of the failure of a 130 MWt gas-fired water boiler. The fault was a rupture of the helically finned tubes in the first rows of the second-stage water heater (ECO2). The high frequency of failures forced the boiler user to investigate their causes. The rapid drop in water flow in the ECO2 and the tightly finned pipes suggested that the permissible operating temperature of the steel used was exceeded. The only possible way to assess the working conditions was through a CFD simulation of the operation of the ECO2. Validated with the data acquisition system, the results show that the main reason for the failure was the overheating of the first rows of finned water heater pipes, regardless of the boiler load. The high heat flux value, exceeding 500,000 W/m2, and the increased flue gas temperature in front of the ECO2, almost reaching 900 °C, affected the appearance of the boiling film, limiting the cooling of the tube wall. Heat radiation and eddies behind the tubes significantly impacted the non-uniform temperature distribution, resulting in high pipe wall stress. By analyzing the service life of the first row of pipes based on the Larson–Miller parameter, it was concluded that the pipes would fail after only a few tens of hours. [ABSTRACT FROM AUTHOR]

The influence of flow step ratio (FSR) on the startup characteristics of instant heat pump water heaters (IHPWHs) with natural mixture M (R744/R290 (12/88)) under nominal conditions was studied experimentally to verify the feasibility of a new quick startup method. The results show that the FSR had a marked effect on the startup time of system performance parameters. Under the optimal FSR of 0.6, the shortest system startup time and available hot water supply time were 700 s and 250 s, respectively, which were markedly shorter than those in the conventional startup. Therefore, rapid startup of the system and rapid production of usable domestic hot water can be realized by controlling the flow step. The influence of flow step on the variation trend of system performance parameters was obviously different, and there was no slow warming section for the heat sink outlet temperature (HSOT) under three FSRs. The HSOT, heating capacity, and high pressure side pressures had the maximum values in the quick startup, and the maximum values were obviously affected by the FSR. The FSR had no marked effect on the minimum suction pressure. The refrigerant pressures and refrigerant temperatures fluctuated markedly in both rapid and conventional starts. [ABSTRACT FROM AUTHOR]

For a country with a tropical climate, such as Indonesia, heat pump technologies are usually necessary in high-altitude regions, where the temperatures tend to be cooler, such as a pool heater for an artificial hot spring swimming pool. A vapor compression heat pump's optimal performance relies on its working fluid's characteristics. This paper aimed to assess the performance and compare the time required to heat a hot spring pool using heat pumps with two different refrigerants: R32 and R134a. A thermodynamic modeling approach was employed to determine the better refrigerant choice between R32 and R134a for the heat pump, aside from other important factors that are considered when selecting the refrigerant, such as safety and environmental impacts. Comparing the results of R134a and R32 refrigerants, R134a has a higher GWP value than R32, indicating that R32 is more environmentally friendly. Regarding safety, R134a has low toxicity and flammability, while R32 exhibits low toxicity and mild flammability. Thus, R134a is considered safer than R32. Furthermore, the COP value of R134a was found to be higher than that of R32, indicating that R134a offers greater efficiency for the heat pump compared to R32. [ABSTRACT FROM AUTHOR]

The generation of electricity, considering environmental and economic factors is one of the most important challenges of recent years. In this article, a thermoelectric generator (TEG) is proposed to use the thermal energy of an electric water heater (EWH) to generate electricity independently. To improve the energy conversion efficiency of the TEG, a fuzzy logic controller (FLC)-based perturb & observe (P&O) type maximum power point tracking (MPPT) control algorithm is used in this study. An EWH is one of the major electricity consuming household appliances which causes a higher electricity price for consumers. Also, a significant amount of thermal energy generated by EWH is wasted every day, especially during the winter season. In recent years, TEGs have been widely developed to convert surplus or unused thermal energy into usable electricity. In this context, the proposed model is designed to use the thermal energy stored in the EWH to generate electricity. In addition, the generated electricity can be easily stored in a battery storage system to supply electricity to various household appliances with low-power-consumption. The proposed MPPT control algorithm helps the system to quickly reach the optimal point corresponding to the maximum power output and maintains the system operating point at the maximum power output level. To validate the usefulness of the proposed scheme, a study model was developed in the MATLAB Simulink environment and its performance was investigated by simulation under steady state and transient conditions. The results of the study confirmed that the system is capable of generating adequate power from the available thermal energy of EWH. It was also found that the output power and efficiency of the system can be improved by maintaining a higher temperature difference at the input terminals of the TEG. Moreover, the real-time temperature data of Abha city in Saudi Arabia is considered to analyze the feasibility of the proposed system for practical implementation. [ABSTRACT FROM AUTHOR]

As the smart grid involves more new technologies such as electric vehicles (EVs) and distributed energy resources (DERs), more attention is needed in research to general energy storage (GES) based energy management systems (EMS) that account for all possible load shifting and control strategies, specifically with major appliances that are projected to continue electrification such as the electric water heater (EWH). In this work, a methodology for a modified single-node model of a resistive EWH is proposed with improved internal tank temperature for user comfort modeling and capabilities for conservation voltage reduction (CVR) simulations as well as Energy Star and Consumer Technology Association communications protocol (CTA-2045) compliant controls, including energy storage calculations for "energy take". Daily and weekly simulations are performed on a representative IEEE test feeder distribution system with experimental load and hot water draw (HWD) profiles to consider user comfort. Sequential controls are developed to reduce power spikes from controls and lead to peak shavings. It is found that EWHs are suitable for virtual power plant (VPP) operation with sustainable tank temperatures, i.e., average water temperature is maintained at set-point or above at the end of the control period while shifting up to 78% of EWH energy out of shed windows per day and 75% over a week, which amounts to up to 23% of the total load shifted on the example power system. While CVR simulations reduced the peak power of individual EWHs, the aggregation effect at the distribution level negates this reduction in power for the community. The EWH is shown as an energy constant load without consistent benefit from CVR across the example community with low energy reductions of less than 0.1% and, in some cases, increased daily energy by 0.18%. [ABSTRACT FROM AUTHOR]

Tankless gas hot water users’ perceived comfort is severely affected by sudden changes deviating from the desired temperature. Water temperature instability due to overshoots and undershoots is the most common issue that appears mainly due to sudden changes in users’ water flow demands and response delays inherent to the heating system. Classical controllers for heat cells have difficulties responding to temperature instability in a timely manner because they lack the capacity to anticipate the effects of sudden variations in water flow rate. Previous studies have reported the model predictive controller (MPC) with adaptive function strategy to provide the best response for stabilizing temperature, and its performance is a result of the predictive nature that allows for anticipating and correcting the negative effects on temperature from sudden flow rate variations. The present study aims to employ this strategy to a low-computational algorithm that can be embedded in low-cost hardware with limited computational and memory resources. The study’s motivation is to fill the space manufacturers have left in this regard by implementing low-cost optimal-performance microcontrollers for water heaters. The algorithm results show good agreement for the responses in temperature stabilization with experimental data. [ABSTRACT FROM AUTHOR]

In the near future, hydrogen is expected to become a significant fuel, greatly contributing to atmospheric air quality. So far, fossil fuels have dominated global hydrogen production. Pure hydrogen can be produced by electrolysis of water; however, it is an energy-demanding process. In this study, a novel multigeneration system is introduced using nanofluid in a solar system. The proposed system includes a quadruple effect absorption refrigeration cycle, a thermoelectric generator, a PEM electrolyzer, a vapor generator, and a domestic water heater. A parametric study was done to consider the effect of significant parameters on the system's efficiency. It was observed that the system generated 18.89 kW of power, and the collector energy and exergy efficiency were 82.21% and 80.48%, respectively. Furthermore, the results showed that the highest exergy destruction rate occurred in the solar system at the rate of 4461 kW. The energy and exergy COPs of the absorption chiller were discovered to be 1.527 and 0.936, respectively. The hydrogen production rate decreases by increasing the volume concentration of the nanoparticles, the solar radiation, and the figure of merit index. [ABSTRACT FROM AUTHOR]

In this comparative study, the thermodynamic and economic investigation of an integrated system driven by a parabolic trough collector and geothermal water is carried out. The proposed multigeneration system is composed of a high-temperature modified Kalina cycle, an electrolyzer, a combined organic Rankine cycle-ejector refrigeration (ORC-EJR) cycle, a reverse osmosis (RO) desalination unit, and a domestic water heater. The absorption fluids applied in the solar collector are AL2O3 and CuO-based nanofluids, and Therminol VP1 as the base fluid. A comprehensive thermodynamic and exergoeconomic analysis is carried out for the proposed cycle. Engineering Equation Solver (EES) software is used in all conducted simulations. Nanoparticle percentage, solar irradiation, ambient temperature, and collector inlet temperature were the parameters studied to find their effects on the hydrogen production rate, total net power, useful energy achieved, energy and exergy efficiency, collector outlet temperature, and freshwater production rate. The highest outlet temperature of the solar collector was found to be 688.7 K, and the maximum energetic and exergetic efficiencies of the cycle were 34.45% and 17.25%, respectively. The exergo-economic outputs show that the PEM with 1.99 $/h has the maximum exergy destruction cost rate. The results depicted that CuO-based nanofluid has better performance from the exergy and exergo-economic viewpoints compared to AL2O3- nanofluid. Also, the results proved that the nanoparticle percentage and solar irradiation increases lead to the increase in hydrogen production rate and total net power produced by the system. Moreover, the freshwater production rate increases when the ambient temperature and the collector inlet temperature rise. [ABSTRACT FROM AUTHOR]

This paper analyzes methods of heating battery-driven electrical buses. The examined buses were two identical airport transport buses and two buses used in local transportation. To heat the first buses, an electrical water heater with a heating capacity of 20 kW, and for air conditioning, a rooftop air conditioner with a cooling capacity of 20.6 kW was installed. Climate control in the city buses was achieved using an R744 heat pump with a cooling capacity of 25 kW and a heating capacity between 14 and 21 kW, along with an electrical water heater with a capacity of 32 kW. During the project, the measurement data of the buses described above were taken for a full year and evaluated. The analysis of the measurement data brought insights into the specific electrical energy consumption of climate control in the buses in real operating conditions at outdoor temperatures between 2 °C and 36 °C. The results of this project additionally provide information on the optimization potential for the climate control of buses. [ABSTRACT FROM AUTHOR]

In the global trend towards decarbonization, peer-to-peer (P2P) energy trading is garnering increasing attention. Furthermore, energy management on the demand side plays a crucial role in decarbonization efforts. The authors have previously developed an automated bidding agent that considers user preferences for renewable energy (RE), assuming users own electric vehicles (EVs). In this study, we expand upon this work by considering users who own not only EVs but also heat pump water heaters, and we develop an automated bidding agent that takes into account their preferences for RE. We propose a method to control the start time and presence of daytime operation shifts for heat pump water heaters, leveraging their daytime operation shift function. Demonstration experiments were conducted to effectively control devices such as EVs and heat pumps using the agent. The results of the experiments revealed that by controlling the daytime operation of heat pumps with our method, the RE utilization rate can be improved compared to scenarios without daytime operation shifts. Furthermore, we developed a simulator to verify the outcomes under different scenarios of demand-side resource ownership rates, demonstrating that higher ownership rates of EVs and heat pumps enable more effective utilization of renewable energy, and that this effect is further enhanced through P2P trading. Based on these findings, we recommend promoting the adoption of demand-side resources such as EVs and heat pumps and encouraging P2P energy trading to maximize the utilization of renewable energy in future energy systems. [ABSTRACT FROM AUTHOR]

In this paper, the fabrication and optimization of a spiral-tube heat exchanger (STHE) were considered for improving the heat transfer rate and efficiency of traditional instantaneous water heaters. The large number of instantaneous water heaters exported from the customers of the "Garman Gas Toos" company, which was mainly due to corrosion and leakage, imposed a lot of cost and credit reduction for this company. The high energy consumption was the second reason that justified working on a new STHE. The main innovation of this research is the design and construction of a new heat exchanger with a smaller size and higher efficiency with the help of identifying the factors affecting its efficiency and heat transfer rate. In order to optimize the responses, three variables were considered, including fin number (per unit area), exhaust outlet diameter, and water flow rate. Implementing face-centered central composite design (CCD), the proposed levels of factors and the corresponding response variables were measured in the "Garman Gas Toos" laboratory. Using the design of experiments (DoE), the effects of the three factors and their mutual interaction effects were evaluated. Response surface methodology (RSM) was devised to build a prediction model and obtain the values of the factors for which the responses were optimal. Based on the results, optimum conditions for the STHE were found to be an exhaust diameter of 4 cm and a water flow rate of 6 L/min coupled with six fins. At this optimal point, the values of efficiency and heat transfer rate, as response variables, were obtained as 85% and 8480 W, respectively. [ABSTRACT FROM AUTHOR]