Domestic Water Heating Research Articles

MgO-Nano Coating Consequences on the Performance of Domestic Solar Water Heating System

Nowadays, government around the world confining to usage of fossil fuels as they are emitting more harmful emissions to the nature. Thereby, some novel approaches which curbs the fossil fuel addiction and environmental degradation plays an imperative role in present days. The technologies which helps to effective utilization of solar energy is too urge. In line with this an effort is made to use solar energy effectively by doing some changes in solar water heating system. In this current study Magnesium Oxide (MgO) nano particles are prepared in house and characterized. Later, study unfolds the effect of reflective coatings on the performance of solar water heating system. From the learn, it is cleared that solar water heating system with MgO nano coated reflective plate has shown the better performance (heat flux & Reynolds no.) when compared to without reflective plate, with reflective plate and reflective plate with micro coatings.

Modeling and design of the new combined double-flash and binary geothermal power plant for multigeneration purposes; thermodynamic analysis

Renewable energy sources have great importance to deal with environmental detriments. To clean and sustainable future, various design renewable energy-assisted plants are of great importance. The current study examines the design and investigation of a double-flash binary geothermal energy-powered integrated system for useful products. For the purpose of producing hydrogen, power, heating, and drying, the proposed work basically consists of two steam turbines, a transcritical carbon dioxide Rankine cycle (tCO2-RC), a PEM electrolyzer, a domestic water heater (DHW), and a dryer. The chief target of this research study is to develop a more efficient plant as well as multigeneration productions. Additionally, detailed parametric modeling is carried out using energetically and exergetically approaches to examine this designed plant in the context of thermodynamic analysis. The variation of some parameters that influence the plant's performance, such as geothermal water temperature, flash pressure, and ambient temperature, are parametrically investigated. Subsequently, the thermodynamic simulation results show that the advised integrated plant produces 4431 kW electrical power. Also, the amount of the hydrogen generation capacity is 0.006809 kgs−1. The tCO2-RC sub-plant's energetic and exergetic performance is determined as 6.18% and 27.14%, respectively. Furthermore, the suggested integrated plant's energetic and exergetic performances are 26.20% and 37.49%. From the results, it can be finalized that the integration of various systems with the geothermal power plant is successfully possible and, in this way, there will be an increase in system performances.

Experimental investigation of the charging and discharging of latent heat in phase change material (PCM) based aluminium tube heat exchanger

Nowadays, given the increasing importance of energy sources, the possibility of energy storage in the heat exchangers through the Phase Change Materials (PCM) and releasing it when needed has been extremely essential. This study seeks to develop a model as that of the domestic water heating system in which the phase change material is used for storing that heat energy as latent heat and it can be discharged during cooling. The behaviour of a PCM material is studied and the performance is tried to improve by using aluminium as the inner tubes instead of copper. In this experimental study, the thermal characteristics of PCM is studied by passing hot fluid and cold fluid through the tubes. Further the heat-storing capacity and the temperature distribution of wax along the tube was studied at different fluid temperatures. Also, the type of flow created by the fluid for different temperatures and the corresponding behaviour of the PCM during that particular temperature is also studied. A commercial grade Paraffin wax as PCM material with specific heat capacity of 2 kJ/kg-K is used and arrived at effectiveness around 0.48 for 40-50 °C and 0.59 for 50-60 °C. Logarithmic average of the temperature difference between 40°C-50 °C hot cycle is 10.654°C and during the cold cycle it is: 2.495°C, In the same way for 50°C -60 °C, during Hot cycle 11.56°C and for cold cycle 3.77°C. Finally, it is observed that based on the experimental study on the charging and discharging of latent heat storage, due to the low thermal conductivity of Phase change material, the rate of heat transfer during discharging is very low and the time required for discharging of latent heat storage is longer compared to the time required for charging of latent heat storage due to low heat transfer rate between PCM and hot Temperature fluid (Water).

Energy Recovery in Air Conditioning Systems: Comprehensive Review, Classifications, Critical Analysis, and Potential Recommendations

Energy has become the backbone of humanities daily activities. Heating, ventilating, and air conditioning systems (HVAC), which consume around 39% of energy in the residential sector, have turned into an essential constituent for providing fresh air, especially after COVD-19, not only in hospitals but also in any simple construction. Thus, decreasing this percentage or recovering part of the energy lost is an essential issue in today’s energy management scenarios. In this context, the present manuscript suggests a comprehensive review, classifications, critical analysis, and potential recommendations for energy recovery in air conditioning systems. It classifies energy recovery into two main categories: using lost energy for external uses, such as heating domestic water, or with other devices; and using lost energy for internal uses, such as the hot airflow which can be reused again for increasing efficiency of HVAC. In addition, this paper presents a summary of previous research and undertakes a review of the devices used for recovering energy. Furthermore, this review identifies superior devices in terms of climate and weather conditions. These objectives are accomplished by investigating around 190 published papers to conclude that energy recovery devices show a considerable effect on energy consumption in HVAC, mainly the heat pipe, fixed plate, and rotary wheel devices.

A Comparative Performance Analysis between Serpentine-Flow Solar Water Heater and Photovoltaic Thermal Collector under Malaysian Climate Conditions

Solar energy has increasingly been employed for domestic and industrial water heating. Both conventional solar water heater (SWH) and photovoltaic thermal (PVT) systems suffer from the drawback of poor energy conversion efficiency. In this article, a unique parallel serpentine-flow thermal collector has been designed and developed that has been employed as an isolated SWH and also integrated with a 32-cell monocrystalline photovoltaic (PV) module. Simulation models of both SWH and PVT systems have been built in TRNSYS to study their thermal performance numerically. Thereafter, outdoor experimental investigations have been conducted under the composite climates of Malaysia. Experimental results show very good agreement with the simulation outcomes with disparity less than 2%. At the optimum flow rate, the maximum thermal efficiencies of SWH and PVT are 82.5% and 74.62%, respectively. Superior water outlet temperature was obtained with SWH. Although SWH exhibits superior thermal performance, PVT’s additional electrical output might make it preferable for several applications.

Data-Driven Virtual Replication of Thermostatically Controlled Domestic Heating Systems

Thermostatic load control systems are widespread in many countries. Since they provide heat for domestic hot water and space heating on a massive scale in the residential sector, the assessment of their energy performance and the effect of different control strategies requires simplified modeling techniques demanding a small number of inputs and low computational resources. Data-driven techniques are envisaged as one of the best options to meet these constraints. This paper presents a novel methodology consisting of the combination of an optimization algorithm, two auto-regressive models and a control loop algorithm able to virtually replicate the control of thermostatically driven systems. This combined strategy includes all the thermostatically controlled modes governed by the set point temperature and enables automatic assessment of the energy consumption impact of multiple scenarios. The required inputs are limited to available historical readings from smart thermostats and external climate data sources. The methodology has been trained and validated with data sets coming from a selection of 11 smart thermostats, connected to gas boilers, placed in several households located in north-eastern Spain. Important conclusions of the research are that these techniques can estimate the temperature decay of households when the space heating is off as well as the energy consumption needed to reach the comfort conditions. The results of the research also show that estimated median energy savings of 18.1% and 36.5% can be achieved if the usual set point temperature schedule is lowered by 1 °C and 2 °C, respectively.

Waste Heat Recovery from Servers Using an Air to Water Heat Pump

The analysis of advisability and profitability of using an air to water heat pump for the purpose of waste heat recovery from servers being used as cryptocurrency mining rigs, was performed. To carry out such an analysis, the cooling unit of the computing server was connected to the heat pump, and the entire system was adequately equipped with devices measuring parameters of the process. Performed experiments proves that the heat pump coefficient of performance (COP) reaches satisfactory values (i.e., an average of 4.21), what is the result of stable and high-temperature source of heat at the pump inlet (i.e., in the range of 29.9-34.1). Economic analysis shows a significant reduction in the cost of heating domestic hot water (by nearly 59-61%). The main conclusion which can be drawn from the paper, is that in a case of having a waste heat source in a form of a server or similar, it is advisable to consider the purchase of air-to-water heat pump for the purpose of domestic hot water heating.

Multi-objective bat optimization for a biomass gasifier integrated energy system based on 4E analyses

• An innovative gasification-based energy system was designed and scrutinized deeply. • The system was evaluated from energy, exergy, economic, and environmental views. • EES, COMFAR III, and MATLAB software were utilized for each step of evaluation. • Bat optimization algorithm was applied to find optimal operating points. • Optimal results were compared with TOPSIS, LINMAP, and Shannon entropy algorithms. An innovative biomass gasifier integrated plant was proposed for combined heating and power production in the current paper. The plant consists of an s-CO 2 cycle, gasifier, combustion chamber, and a domestic water heater for heating purposes. The system was studied from different perspectives, i.e., energetic, exergetic, exergo-economic, economic, and environmental (4E). For this purpose, simulation of the proposed plant was carried out by EES software; then, by utilizing COMFAR III software, the economic sensitivity investigation was conducted to detect the influence of financial parameters on the system's economic features after installation of the plant. Results of economic evaluation unfolded that installing the proposed plant is affordable from the economic point of view. Besides, a sensitivity analysis was conducted to calculate the main performance indicants, including an environmental impact indicator. The proposed system was optimized by a robust Multi-Objective Bat Optimization Algorithm . For determining the final optimum solution, TOPSIS, LINMAP, and Shannon entropy methods were used in the optimization process. Optimization results were also compared to the conventional multi-objective optimization methods to detect the suitable optimization method. The findings of the comparison confirmed that the bat algorithm's performance had been better, based on Taylor and Violin diagrams. Besides, scatter plots of effective parameters are presented to define the suitable operating ranges. The results show that the optimum exergy efficiency, Levelized CO 2 emissions, and total product cost are 38.42%, 0.4757 t/MWh, and 7.517 $/GJ obtained. The total product cost was reduced significantly from 10.01 $/GJ to 7.517$/GJ at the expense of a slight diminish in exergetic efficiency of about 2% through the use of the bat algorithm. Also, the annual greenhouse gas emission made by the proposed system was reduced by about 9% after the optimization process.

Experimental investigation of a solar absorber and nocturnal radiator hybrid system for simultaneous water heating and cooling

An experimental study of a Solar Absorber and Nocturnal Radiator (SAANR) hybrid system used for simultaneous water heating and cooling in Gaborone, Botswana is presented. A SAANR hybrid system was designed and fabricated and the system consists of major components that include a 1.4 m2 SAANR hybrid panel, 100 L hot and cool water storage tanks, chlorinated polyvinyl chloride (CPVC) plumbing and a 0.2778 kg/s circulation pump, all mounted on a steel frame that is inclined at 30 °C to maximize solar absorption and self-cleaning of the panel. Experiments carried out in December 2020 in Gaborone with water at an initial temperature of 26 °C produced 100 L of hot water at 60 °C and similarly 100 L of cool water at 23 °C, during the day and at night respectively. These results provide proof that the SAANR hybrid system could be used simultaneously for applications of domestic water heating and building envelope cooling in Botswana and similar climates. This technology can therefore be used instead of electric water heaters and air-conditioners and thus save energy.

A Review on Techno-Economic Assessment of Solar Water Heating Systems in the Middle East

Currently, the economy of Middle Eastern countries relies heavily on fossil fuel sources. The direct and indirect adverse consequences of fossil fuel utilization for power generation enforce the region’s countries to raise the share of renewable energy. In this context, various incentive policies have been developed to encourage the residential and industrial sectors to support a portion of energy needs through renewable energy resources. In this case, a solar water heating system (SWHS) as an application of solar thermal technology provides some of the heat energy requirements for domestic hot water (DHW) and space heating, supported conventionally by electricity or natural gas, or even other fossil fuels. This paper reviews the feasibility of the SWHS in the Middle East region from technical and economical standpoints and investigates some of the progress, challenges, and barriers toward this market. The pay-back times and CO2 emission reduction under different incentive frameworks and configurations of each system have been assessed in this context. Furthermore, the advantages and weaknesses of the SWHS in several countries have been reported. Finally, various guidelines have been proposed to enhance the development of this technology.

Virtual Test Bench for the Design of Control Strategies for Water Heaters

Abstract An innovative methodology and a virtual test bench (VTB) are proposed to support the design of water heaters’ control strategies. This platform allows to speed up the development and evaluation of control systems even before the existence of prototypes or real test environments. By simulating the environmental conditions and the state of the different device components, it will be possible to detect and correct possible initial errors in the control system design which can be time consuming and costly due to subsequent modifications to the system or equipment components. The architecture of the proposed system establishes four operating modes: open-loop data acquisition, real-time simulation, hardware-in-the-loop simulation, and test of the complete real system, the incorporation of these functionalities in the same platform is not reported in the literature for domestic water heaters. The virtual test bench was designed to accommodate different water heaters including, but not limited to, gas, electric, and heat pumps, for instantaneous hot water production or including hot water storage. The prototype of the virtual test bench is described emphasizing the hardware-in-the-loop methodologies and embedded control. The particular case study of a tankless gas water heater (TGWH) is presented implementing the different operation modes in the virtual test bench. The water heater models, control strategies, simulation, and experimental data are presented and discussed.

Techno-economic analysis of control strategies for heat pumps integrated into solar district heating systems

This present work focuses on assessing the techno-economic benefits of different control strategies for a heat pump integrated into the solar assisted district heating system (SDHS). The system has been developed using dynamic simulation software (TRNSYS) and optimized based on a genetic algorithm. With an industrial-sized heat pump connected to thermal storage tanks for domestic hot water (DHW) and space heating (SH) for the requirements of the community, a SDHS is operated by applying two different control mechanisms for the heat pump based on its reference operating temperature. The application of the methodology is applied to a residential neighborhood community of 10 buildings located in Madrid to act as a proxy for the Mediterranean climates. The results showed a significant effect for the heat pump control in the techno-economic benefits where the proposed system is able to provide a solar fraction up to 99%. Furthermore, the total electricity consumption of the heating system varied by 10% between the best and the worst cases. Besides, the annual seasonal storage efficiency improved up to 90% with a life cycle expense up to 67.12 Euro/MWh, and a payback period of 29 years.

Assessment of control tools for utilizing excess distributed photovoltaic generation in domestic electric water heating systems

Appliance level control and automation is an increasingly promising demand-side management tool with growing installation of advanced metering, monitoring and control infrastructure in both residential and commercial contexts. Successful implementation of appliance control and automation can alleviate network peak demand and improve distributed photovoltaic (D-PV) self-consumption to reduce its network voltage and reverse power flow impacts. Domestic electric water heating (DEWH) systems are widely deployed globally and have one of the highest peak power draw and overall energy consumption of household appliances. DEWH storage tanks offer large thermal energy storage capacity which can be used for shifting demand to lower demand periods. With growing D-PV deployment, they also offer the opportunity to store excess generation that would be otherwise exported to the grid. In this work, an intelligent water heating control tool (IWHC) is developed to store excess D-PV generation in DEWH storage tanks as thermal energy, according to the D-PV generation characteristics, household electricity consumption, hot water draw (HWD) patterns, and real time energy monitoring. The IWHC tool was installed and tested in nine Australian households with D-PV and DEWH systems. For performance comparison, two other commercially available control tools, timer, and diverter, were installed and tested in eleven other households with D-PV and DEWH systems. For each control tool, energy simulation models were developed, and the collected field performance data was used to validate the models. The validated simulation models were extended to a broader set of 380 Australian households with a year of D-PV, household and DEWH electricity consumption data. The results indicate that, on average, households can utilize 2.4 kWh, 1.8 kWh and 3.4 kWh of daily excess D-PV generation for water heating, using the IWHC, timer and diverter, respectively. Financial savings from the control of DEWH are highly dependent on households’ tariffs and daily HWD profiles. Under the most optimal morning dominant HWD profile scenario and with an average tariff, households can, on average, save $100, $80, and $170 per year with the IWHC, timer and diverter, respectively. However, the diverter’s superior field performance comes with higher capital cost, making IWHC the most attractive option.

Heat transfer and pressure drop of supercritical CO2 in brazed plate heat exchangers of the tri-partite gas cooler

The heat transfer characteristic of supercritical CO2 is an essential research topic due to its significant influence on the performance of heat exchangers and systems. In this paper, the heat transfer and pressure drop of supercritical CO2 in the brazed plate heat exchangers are experimentally researched. The heat exchangers belong to a tri-partite gas cooler which can simultaneously fulfill the demands of domestic hot water and space heating. The results demonstrates that the thermal resistance in the CO2 side is the main factor that influences the total heat transfer. The increase of CO2 inlet pressure can reduce the heat transfer coefficients except at the high temperature region. The improvement of heat transfer coefficient by increasing the CO2 mass flow rate is more significant in the space heating (SH) and domestic hot water (DHW) preheating gas coolers, and is lowest in the DHW reheating gas cooler. The influence of DHW inlet temperature is more obvious in the DHW preheating gas cooler that connected to the water inlet. The influence of water mass flow rate is different in the DHW and SH operation modes. Moreover, the effects of CO2 pressure and mass flow rate on the buoyancy force are discussed and the influence of buoyancy force on heat transfer is verified. The inaccuracy of the correlations from the literature is proved and then new correlations are established. The mean absolute relative errors of the new correlations are 11.61% and 12.82% for the one-pass and two-pass configurations, respectively. Furthermore, the frictional pressure drop in the heat exchangers is low (up to 36.51 kPa) and basically increases as the Reynolds number increases.

Operation strategy of multiple stage independent phase change material modules integrated with thermal storage

This paper presents a study on a new technique for the packed bed Thermal Energy Storage (TES) system that consists of having multiple stages of Phase Change Materials (PCMs) modules placed independently. The TES model is integrated with the domestic water heating application and consists of a cylindrical storage tank with spherical PCMs inside the tank. Water is used to transfer heat from the hot water to the PCMs during daytime. The system operates according to a well-defined control strategy that ensures an appropriate distribution of the heat transfer fluid toward the various modules. A parametric study is conducted to evaluate the thermal behavior of the PCMs and the storage performance of the system for complete charge and discharge modes. The paper evaluates the multiple stage independent PCM modules advantageous side compared to the conventional TES system and indicates that the usage temperature and useful energy are significantly enhanced through the use of the proposed technique. In addition to that, the charging and discharging processes analysis are conducted in order to examine the thermal behavior of the independent PCM modules with the variation of different operation parameters.

Comparison of the performance of a domestic solar water heater in different climates in Algeria

A simulation with TRNSYS of an individual solar water heater for the hot water needs of an average family in Algeria was made; three cities of different climates were chosen to the north on the coast, in the highlands and in a desert region, the solar water heater consists of a flat panel of 4m² and a storage tank of 300 liters, a back-up electrical energy is activated when solar radiations are insufficient or during the night, the consumption of domestic hot water leaving the tank at 60 °C follows a typical profile, the results show significant performance in the south and similar data in the north and in the highlands.

Analysis of electricity consumption and thermal storage of domestic electric water heating systems to utilize excess PV generation

Water heating is one of the most energy intensive applications in households and domestic electric water heating systems (DEWH) offer large thermal storage for moving electrical load across the day. This study uses a unique dataset from 410 households and presents a comprehensive analysis of electricity consumption and hot water draw of DEWH for the Australian context. Using the real-world data and thermal energy modelling tool TRNSYS, the study analyses the potential of storing and using excess PV generation in DEWH and investigates the impact of different daily hot water draw profiles, PV and DEWH size on the potential for excess PV utilization. The results show that households on average use 6 kWh of energy for DEWH and 142 L of hot water daily. Potential excess PV utilization is highly dependent on the household's daily hot water draw profile and is also affected by seasonality. On average, excess PV generation from a 4.5 kW PV system can provide 48% of daily DEWH energy for a household with a typical working family profile, which corresponds to a 28% increase in PV self-consumption.

Ground source heat pump control methods for solar photovoltaic-assisted domestic hot water heating

Domestic hot water (DHW) heating is one of the most energy-consuming activities in a typical household. Photovoltaics (PV) connected with a ground source heat pump (GSHP) offers a low-emission method for DHW heating. This paper studies four different control methods for DHW heating in a building with a GSHP and a PV system. The main control method aims to minimize DHW heating costs by utilizing Nord Pool Spot market information together with a PV production output forecast. The results of this control method, implemented with a perfect PV output forecast and assessed over three years of hourly data, indicate that annual cost savings over other methods are achievable. Results with the real-world actual PV output forecast, evaluated between June–September 2020, demonstrate DHW heating cost savings up to 36–53%, even though forecasting errors are present. The heating costs are 9–11% higher compared against the perfect forecast case. The suggested control method thereby effectively reduces the costs when compared with all other methods, and its performance is not significantly affected even when an actual imperfect forecast is implemented. The results also indicate that minimizing energy consumption does not offer the lowest cost.

Life-cycle cost optimization of a solar combisystem for residential buildings in Nepal

ABSTRACT Current solar thermal systems used in Nepal are mostly for domestic hot water heating. Meanwhile, there is a growing need for space heating. A solar heating system can be configured to provide heat for both space heating and domestic hot water, leading to a solar combisystem. Research on residential solar combisystems in the Nepalean context barely exists in literature. This paper intends to propose, model and optimize a solar combisystem for typical single-family houses in Nepal. The optimization problem is formulated to have life-cycle cost as the objective function and a total of 11 variables, which are related to the sizing of combisystem components and the insulation thickness of building envelope. The number of hours not satisfying the thermostat heating set point is treated as the constraint. TRNSYS is used for modeling the solar combisystem. Particle Swarm optimization and the Hooke-Jeeves algorithm implemented in GenOpt are sequentially applied to solve the optimization problem. The results show that the optimization is effective to reduce the life-cycle cost by 66% for the Terai region and 77% for the Hilli region. The findings have demonstrated the importance of building envelope insulation to spread the use of solar combisystems in Nepal.

Energy-Efficient Operation of PV-T Solar Collectors with Heat Pump based Water Heaters Suitable for Domestic Applications

A photovoltaic-thermal (PV-T) hybrid collector evaporator was designed and developed to produce electrical energy and extract thermal energy simultaneously from the panel using the refrigerant circulated the evaporator tubes. The refrigerant absorbs the heat from photovoltaic panels during its phase change from liquid to vapour. The PV-T evaporators deliver both electricity and heat outputs. An R-32 refrigerant-based solar-assisted heat pump water heating system with a rated heat output of  4 kW was developed and tested its performance for producing 150-200 litres of hot water at an average temperature of 60oC. The R-32 refrigerant is selected because it does not have any ozone depletion potential (ODP), and possess very low global warming potential (GWP). The heat pump evaporator was designed to absorb 3.25 kW heat from the panel and maintains the panel below 30oC. The average PV electricity output was 6 kWh, and the requirement was 3.5 kWh. The average excess power of 2.5 kWh has been supplied to the grid, and the average coefficient of performance (COP) of the system was 6.3. For a life span of 25 years, the total equivalent warming impact analysis (TEWI) resulted in a CO2 value of 15,543 kg, which is very much lower than that of conventional systems. The economic analysis performed was reported, and the system is found to be quite suitable for domestic applications and also economically feasible with a payback period of 2.5 years. Keywords: Solar PV-T Collectors, VFD Compressor, Domestic Water Heating.