Hot Water Heating Research Articles

Analysis of a variable auxiliary volume predictive-controller for an auxiliary-energy producer with a stratified solar thermal combistorage

Status quo controllers of auxiliary-energy system in a hybrid thermal energy system use a simple dual-auxiliary-zone method where the maximum temperature and maximum volume of the space heating (SH) and domestic hot water (DHW) loads on highest consumption day in a year are utilized. Due to this simple control, there are high storage losses in the winter period an also less storage space available for the renewable production. In this paper, the authors propose a novel predictive control strategy with the use of stratified thermal storage. The control strategy is further, in terms of as ideal simulation study, investigated for a decentral thermal energy system in southern Germany with solar thermal collectors and a gas boiler auxiliary energy system for a stratified combistorage with DHW and SH loads. The obtained results in a Sonnenhaus standard single-family house show that the auxiliary energy input is reduced by 650 kWh (6%) annually with a maximum of 190 kWh reduction in March. Moreover, in the month of March, a 5% increment in terms of solar thermal fraction and a 5.5% decrement in terms of the gas boiler fraction is achieved. And by better use of the storage, especially during the winter months (November to March), a 16–20% reduction in storage losses is achieved. Annually, 2.2% reduction of gas boiler fraction, 4.6% reduction of storage loss and 1.8% increase of solar fraction are attained.

Combining horizontal evacuated tubes with booster mirror reflector to achieve seasonal reverse output: Technical and experimental investigation

Owing to seasonal fluctuations in solar radiation resources and ambient air temperature, stationary solar collectors have higher output in summer and lower output in winter. However, seasonal heating demand and hot water usage follows an opposite pattern, resulting in insufficient heating in winter and the risk of overheating in summer, reducing the feasibility of solar thermal technology. In this study, a new configuration that combines horizontal evacuated tubes with a mirror reflector was developed to achieve seasonal reverse performance: high performance in winter and low performance in summer. In contrast to conventional collectors, the collector plane of this new module was inversely inclined, pointing to the solar altitude angle on the summer solstice. Together with the bottom mirror reflector, the normal vector of the composed aperture plane was designed to point to the solar altitude angle on the winter solstice. Through experimental and numerical studies, we found that the standardized thermal efficiency of the new module on the winter solstice was comparatively high because it can be regarded as a concentrating collector with a concentration ratio of 0.77. On the summer solstice, the thermal efficiency was extremely reduced due to 100% self-shading of the collector plane. Based on the idea of overcoming the seasonal instability of renewable resources, this designed solar module is expected to enhance the competitiveness of solar heating technology, especially in the decentralized clean heating market.

Development and analysis of a clean methane production system

In the presented study, the design for a new renewable integrated multigeneration system that is capable of producing natural gas as well as methane is proposed. The multigeneration system harnesses solar energy through the implementation of a solar power tower and receives its electrical energy input by harnessing wind energy from horizontal axis wind turbines. The designed system is capable of storing the thermal energy collected from the solar tower through the integration of a molten salt storage sub-system containing a hot and cold storage tank. The methane produced from the system is renewably synthesized. This is essentially achieved from the syngas generated through the combustion of biomass, and the H2 gas that was produced from the electrical input from wind energy to a polymer electrolyte membrane system. The system is expected to perform at its best from May to July, due to the greatest wind velocity, hours of daylight, and solar radiation available during these months. Additionally, the useful outputs produced from the system consist of electrical power, heat for space heating, cooling and domestic hot water. During normal operating conditions, the system has an overall energy and exergy efficiency of 61% and 28.64%, respectively during its heating mode. Additionally, the system has an energetic and exergetic COP of 0.546 and 0.135 during the heating mode and an energetic and exergetic COP of 4.661 and 0.4934 during the cooling mode. Moreover, numerous parametric studies are performed to identify how the system operates during different operating conditions.

Investigation of a new integrated energy system with thermochemical hydrogen production cycle and desalination

This study presents design, development and analysis of a novel integrated energy system based on renewable geothermal energy source with a Copper Chlorine (CuCl) thermochemical cycle for hydrogen production production and a multistage desalination subsystem for freshwater production. In the proposed system, five useful outputs are effectively generated, such as heat for space heating, electricity, freshwater, hot water and hydrogen. CuCl thermochemical cycle is used for hydrogen production. The need for achieving high-temperature levels for the thermochemical cycle is met by a CuCl cascaded heat pump configuration in the system. The presented system is further analyzed and assessed thermodynamically through energy and exergy approaches. A case study is conducted for the city of Vancouver, Canada. Some parametric studies are also performed to observe the effects of different ambient and working conditions for the overall system and subsystems. According to conducted thermodynamic analysis, 42.06% energy and 49.65% exergy efficiencies are obtained for the overall system. The total exergy destruction rate for the overall system components is determined to be 46.56 MW. In the CuCl-Mercury cascaded heat pump configuration, the coefficient of performance values are obtained as 1.557 for energy and 1.128 for exergy.

Heat storage: Hydration investigation of MgSO4/active carbon composites, from material development to domestic applications scenarios

The scarcity of durable and low-cost sorbent materials remains a significant technological barrier to long-term heat storage. In the present work, composite materials based on activated carbon supports and magnesium sulfate hydrates (labelled MgSO4/AC) were developed in order to increase the energy density and improve mass and heat transport phenomena. The results of composite characterization revealed uniform dispersion of magnesium sulfate in composites produced via incipient wetness impregnation. The hydration enthalpy increased as the MgSO4 content on AC increased, reaching a plateau for MgSO4 content of more than 30%wt (30-MgSO4/AC and 40-MgSO4/AC samples). The hydration experiment performed on the 30-MgSO4/AC sample at RH = 60% verified the relation between the salt hydration level and the hydration enthalpy. Higher water partial pressure enhanced water molecule transport and improved salt hydration. The hydration enthalpy of 30-MgSO4/AC showed an increase from 859 J/gdry material at RH = 30% to 1324 J/gdry material at RH = 60%. After 8 cycles of hydration/dehydration, the 30-MgSO4/AC sample was practically stable. Furthermore, the 30-MgSO4/AC) composite was modeled in two distinct scenarios for house heating and sanitary hot water generation. Finally, the experimentally obtained calorimetric data were used to implement a numerical model. Two different scenarios were considered, the first for heating a house and the second for producing hot sanitary water. Both scenarios show the possibility of using the MgSO4/AC composite in a multifunction thermochemical heat storage system.

Latent Thermal Energy Storage Application in a Residential Building at a Mediterranean Climate

An innovative thermal energy storage system (TESSe2b) was retrofitted in a residential building in Cyprus with a typical Mediterranean climate. The system comprises flat-plate solar collectors, thermal energy storage tanks filled with organic phase change material, a geothermal installation consisting of borehole heat exchangers with and without phase change material and a ground source heat pump, an advanced self-learning control system, backup devices and several other auxiliary components. The thermal energy storage tanks cover the building’s needs at certain temperature ranges (10–17 °C for cooling, 38–45 °C for heating and 50–60 °C for domestic hot water). A performance evaluation was conducted by comparing the TESSe2b system with the existing conventional heating and cooling system. The systems were simulated using commercial software, and the performance of the systems and the building’s energy needs were calculated. Based on the energy quantities, an economic analysis followed. The equivalent annual primary energy consumption with the conventional system resulted in being 43335 kWh, while for the storage system, it was only 8398 kWh. The payback period for the storage system was calculated to be equal to 9.76 years. The operation of the installed storage system provided data for calculations of the seasonal performance factor and storage performance. The seasonal performance factor values were very high during June, July and August, since the TESSe2b system works very efficiently in cooling mode due to the very high temperatures that dominate in Cyprus. The measured stored thermal energy for cooling, heating and domestic hot water resulted in being 14.5, 21.9 and 6.2 kWh, respectively. Moreover, the total volume of the phase change material thermal energy storage tanks for heating and domestic hot water was calculated to be roughly several times smaller than the volume of a tank with water as a storage medium.

A field study of combo heating systems in Canadian single-family buildings

This study presents a field study of the performance of three multi-zone gas-fired comboheating systems that provide space heating and domestic hot water in three new single-family houses in the Greater Toronto Area in the Province of Ontario, Canada. Two systems are composed of a gas-fired condensing tankless water heater integrated with a smart air handling unit, while the third system is composed of a gas-fired condensing combi boiler integrated with a smart air handling unit. The performance of the three combo heating systems was monitored, analyzed and evaluated over one heating season. The gas consumption of the three systems were compared with traditional gas-fired heating systems (composed of forced-air gas furnace and gas storage tank water heater). Results showed that combo heating systems tested in this study are reliable, met the peak space heating load, improved the indoor thermal comfort by providing two independently controlled temperature zones and achieved significant gas savings compared to traditional natural gas heating systems. The annual gas consumption and greenhouse gas emissions of the combo heating systems tested in this study are less than the traditional gas-fired heating system (forced-air gas furnace and gas storage tank water heater) by up to 29%.

An innovative conversion of a district heating water-tube boiler for cogeneration of electricity and heat

The primary goal of combined heat and power (CHP) generation is to increase the overall efficiency of the process, which is primarily achieved by reducing energy losses associated with a single generation. The research aims to verify the possibility of adapting the district heating hot water cycle into the CHP plant through thermodynamic and techno-economic analyses. A complete layout of the innovative conversion as well as technical limits and possibilities are discussed. The manuscript presents a method of obtaining cogeneration conditions, therefore simultaneous production of heat and electricity in a cycle where the heat source is a water boiler. The solution from the thermodynamic and financial point of view has been proven on the example of the WR25 stoker boiler, for which the system produces 0.5 MWe with a simultaneous increase in the efficiency of the unit and no additional restrictions on its operation. At the same time, methods for further increasing the electric power without additional modernizations in the system were presented.

Dynamic simulation of hydrogen-based zero energy buildings with hydrogen energy storage for various climate conditions

Solar energy systems are an effective way to meet the needs of zone heating, cooling, electricity, and domestic hot water. However, to reach sustainability, and energy storage unit should be considered for installation. In this study, two combined cooling, heating and power (CCHP) systems are simulated and studied using TRNSYS software; both using natural gas engine generators and photovoltaics as prime movers and a hydrogen fuel cell/electrolyzer storage unit, one with absorption chiller and another with compression chiller cooling. For the study, a residential building is modeled for three major populated climate zones of the United States of America, namely, Hot-humid, mixed-humid and cold using DesignBuilder and EnergyPlus software. The energy demand for its HVAC operation and domestic electricity is obtained and used for system simulation in TRNSYS software. Due to choosing actual equipment for the CCHP arrangement, precise economic and environmental models are designed to further evaluate the possibility of execution of the system. The results show that absorption chiller-equipped CCHP has better performance both environmentally and economically. In addition, the outcome shows that the suggested systems show less favorability to be utilized in hot humid climate zones.

Energy, exergy and economic analyses and multiobjective optimization of a novel solar multi-generation system for production of green hydrogen and other utilities

Renewable energy based multi-generation systems can help solving energy-related environmental problems. For this purpose, a novel solar tower-based multi-generation system is proposed for the green hydrogen production as the main product. A solar-driven open Brayton cycle with intercooling, regeneration and reheat is coupled with a regenerative Rankine cycle and a Kalina cycle-11 as a unique series of power cycles. Significant portion of the produced electricity is utilized to produce green hydrogen in an electrolyzer. A thermal energy storage, a single-effect absorption refrigeration cycle and two domestic hot water heaters are also integrated. Energy, exergy and economic analyses are performed to examine the performance of the proposed system, and a detailed parametric analysis is conducted. Multiobjective optimization is carried out to determine the optimum performance. Optimum energy and exergy efficiencies, unit exergy product cost and total cost rate are calculated as 39.81%, 34.44%, 0.0798 $/kWh and 182.16 $/h, respectively. Products are 22.48 kg/h hydrogen, 1478 kW power, 225.5 kW cooling and 7.63 kg/s domestic hot water. Electrolyzer power size is found as one of the most critical decision variables. Solar subsystem has the largest exergy destruction. Regenerative Rankine cycle operates at the highest energy and exergy efficiencies among power cycles.

A Novel Dynamic Approach to Cost-Optimal Energy Performance Calculations of a Solar Hot Water System in an nZEB Multi-Apartment Building

This paper presents the methodology for conducting a cost-optimal energy performance calculation of a solar hot water system, used for space heating and domestic hot water needs. The calculation is based on dynamic hourly methods, according to the new Energy Performance of Buildings’ (EPB) set of standards EN 15316:2017, and a revision of the standard EN 15316-5:2017 from the year 2021, dealing with storage-tank water temperature calculations. The paper provides proposals for modifications to these newly introduced standards, in order to overcome the observed ambiguities and shortcomings. The calculation of annual energy performance of a building was performed on an hourly basis over a year for the reference of an nZEB multi-apartment building, for a climate area of the city of Zagreb, taking into account water temperature change in the layers of the storage tank connected to solar collectors and hot water boilers. The cost-optimal solution was then determined by varying individual parameters of the building technical system. The influence of these parameters on the energy efficiency of the building was analyzed in detail. Furthermore, the results were compared against those obtained by the Croatian calculation algorithm based on the previous set of EPB standards, EN 15316:2008, currently used EU-wide for the energy performance certification of buildings. The results indicated that the calculation methods of the present algorithm underestimated the consumption of building primary energy by 12%. The energy delivered by solar collectors was underestimated by 18%.

Accelerating Upstream Together: Achieving Infant Health Equity in the United States by 2030.

Accelerating Upstream Together: Achieving Infant Health Equity in the United States by 2030.

ОСОБЛИВОСТІ ВИКОРИСТАННЯ АЛЬТЕРНАТИВНИХ ДЖЕРЕЛ ЕНЕРГІЇ В ГОТЕЛЬНИХ ЗАКЛАДАХ

The purpose of the research is to find out the specifics and feasibility of using the alternative energy sources in hotel enterprises of Ukraine. The rate of development of renewable energy sources in our country over the past 7 years has been analyzed, the main directions of alternative energy have been highlighted. The total installed capacity of renewable energy facilities in Ukraine as of the end of 2021 reached 9,225 MW. At the moment, the capacity of all solar power plants is 6351 MW (SPP), wind power plants is 1593 MW (WPP), the energy of solar power plants of private houses is 933 MW, the energy of biomass power plants is 119 MW, the energy of biogas power plants is 111 MW, the energy of small hydropower plants is 118 MW. The analysis of the state of use of alternative energy sources in hotel complexes was carried out in order to reduce the costs of utility services. The possibilities of reducing the energy dependence of hotel complexes and ecology of modern hotels are considered. The problems and prospects of using renewable energy at hotel enterprises are characterized. The most common systems of alternative sources have been considered, such as solar collectors for heating or heating hot water, wind generators and solar power plants for conversion into electrical energy, biogas plants for heating systems, and heat pumps of four types for heating and air conditioning systems. Examples of their application in existing hotel enterprises of Ukraine are given, the approximate cost and sequence of actions for obtaining permit documentation before the start of installation are estimated. The concept of "alternative energy sources" has been defined. The analysis of the features of the use of alternative energy sources in hotel complexes of Ukraine has been done. The renewable energy projects have been characterized. The assessment of the problems of formation and prospects for the use of renewable energy in hotel enterprises is given. The economic effect from the commissioning of alternative energy supply systems has been calculated, the positive and negative aspects of their use are assessed. The positive ones include saving energy resources, partial or full energy autonomy, a positive impact on the branding of the hotel enterprise due to the use of green energy. It gives a potential opportunity to expand the number of consumers of the hotel product. The disadvantages are high cost of equipment, difficulties with permit documentation and some individual features of system installation.

Validation of a new method to estimate energy use for space heating and hot water production from low-resolution heat meter data

One of the initiatives to reach the European decarbonization goal is the roll-out of smart heating meters in the building stock. However, these meters often record the total energy usage with only hourly resolution, without distinguishing between space heating (SH) and domestic hot water (DHW) production. To tackle this limitation, this paper presents the validation of a new methodology to estimate the SH and DHW from total measurements in different building types in three countries (Denmark, Switzerland, and Italy). The method employs a combined smoothing algorithm with a support vector regression (SVR) to estimate the different heating uses. The estimation results are compared with the different countries’ DHW compliance calculations. The comparison showed that the compliance calculations outperformed this method by considering the validation dataset characteristics.

Performance analysis of a solar-assisted dual-tank heat pump system for climatic conditions in Turkey

This study aimed to analyze the performance of a solar-assisted dual-tank heat pump system under climatic conditions in Turkey. This system and its components were modeled and simulated using transient system simulation software. The system was designed not only to supply domestic hot water for a restaurant, but also to heat it in winter and cool it in summer. The modeled system works on the principle that a water-to-water heat pump operating between dual tanks transfers the heat from the cold water tank (source side) to the hot water tank (load side). The hot water for both heating and domestic hot water is supplied from the hot water tank throughout all seasons, whereas, the cold water is supplied from the cold water tank for cooling the space in summer. A photovoltaic thermal collector was integrated into the cold water tank to support the source side of the heat pump and also to generate electricity for the system in winter, but was used only for producing electricity in summer. Analyses were carried out for five provinces (Istanbul, Ankara, Izmir, Hakkari, and Trabzon) located in five different regions of Turkey. According to the simulation results, the highest seasonal performance factor (2.65) was obtained for Izmir, whereas the lowest seasonal performance factor value (1.74) was obtained for Hakkari. The system worked 52% more efficiently in Izmir than in Hakkari. With the photovoltaic thermal collector, 17.68% of the total electrical energy consumption of the system was compensated for Izmir Province and 12.09% for Hakkari Province.

Proposal to Minimize the European Dependence on Russian Natural Gas for Space Heating and Sanitary Hot Water by Using Heat Pumps

Proposal to Minimize the European Dependence on Russian Natural Gas for Space Heating and Sanitary Hot Water by Using Heat Pumps

Performance Analysis of Systems Powered by a Ground Source Heat Pump

Heat pumps are known as zero-emission heating and cooling devices at the point of energy production. In order to exploit their advantages, they are combined with low-temperature heating systems. Using the example of a residential building in five climatic zones in Poland and one in Ukraine, systems analyses were carried out, in which heat into rooms is supplied in two different ways: low-temperature radiators and thermally active ceilings. The energy demand for heating, cooling and domestic hot water preparation was calculated. The seasonal coefficient of performance of the ground source heat pump was estimated to compare the systems. The results of the analysis confirmed that the thermo-active ceiling (with a flow temperature of 35°C) ensures a lower final energy demand when it works throughout the year in the heating and natural cooling mode compared to the low-temperature radiators (with a flow temperature of 45°C) which facilitate only the heating mode in the heating season. Performance analysis demonstrated differences in final electric energy demand from 8% in the I climatic zone to 9% in the V climatic zone in Poland and 10% in Ukraine.

Influence of Usage and Model Inaccuracies on the Performance of Smart Hot Water Heaters: Lessons Learned from a Field Test on Autonomous Demand Side Management Via Retrofit

Influence of Usage and Model Inaccuracies on the Performance of Smart Hot Water Heaters: Lessons Learned from a Field Test on Autonomous Demand Side Management Via Retrofit

Thermal Loss Analysis of a Flat Plate Solar Collector Using Numerical Simulation

In this paper, we studied theoretically and numerically heated losses of a flat solar collector to model the solar water heating system for the Kazakhstan climate condition. For different climatic zones with a growing cost for energy or lack of central heating systems, promising is to find ways to improve the energy efficiency of the solar system. The mathematical model (based on ordinary differential equation) simulated the solar system work process under different conditions. To bridge the modeling and real values results, we studied the important physical parameters such as loss coefficient, Nu, Ra, and Pr values. They impacted the efficiency of flat solar collectors and heat losses of the system. The developed mathematical models, the design and composition of the software and hardware complex, and automated control and monitoring systems allow solar hot water heating systems to increase the energy efficiency of life support systems and heat supply of buildings by reducing energy consumption for heat supply. The simulation result showed that during the daytime, the temperature of water in the collector is 70°C; the storage of heated water since heated water is cooled at night. We defined that a work period of the system can be extended with high efficiency (April–October) for Almaty region.

Heat Production in Considering Boilers and their Influence on CO and NOx Emission Values

At present, there is a tendency to make greater use of hot water heat sources for the combustion of solid fuels, such as lump wood, coal, coke, instead of heat sources for the combustion of natural gas. This tendency is due to the high price of natural gas as well as the availability of cheaper solid fuel. In many cases, as part of saving on heating costs, respectively. as part of waste disposal, municipal waste of various compositions is also co-incinerated with solid fuel. This co-incineration entails increased emissions, such as CO (carbon monoxide), NOx (nitrogen oxides), TZL (particulate matter), PM10, HCl (hydrogen chloride), PCDD/Fs (polychlorinated dibenzodioxins and dibenzofurans), PCBs (polychlorinated biphenyls) and others which, with a relatively large number of heat sources for the combustion of solid fuel in municipalities, have a significant impact on the quality of the environment in the locality. Between the population and representatives of the state administration as in Žilina, Thus, the Moravian-Silesian Region also lacks awareness of how the environment is degraded due to the co-incineration of solid fuel and municipal waste. At present, there is no qualitative comparison of the effect of combustion of solid fuel and municipal fuel waste to the emission burden on the environment. There are no real measured emission factors for determining the production of the above emissions from the co-incineration of solid fuels and a certain amount of municipal waste. The combustion of fossil fuels and the consequent occurrence of harmful emissions on the environment are therefore becoming a central theme of current heating technology.