Hot Water Generation Research Articles

Comprehensive thermoeconomic study of a new solar thermosyphon-assisted multigeneration system

Nowadays, due to the global energy crisis, limited reservoirs of fossil fuels, and their negative environmental effects, the use of renewable energy sources and multigeneration systems have become good alternatives for conventional thermodynamic systems. One of these resources, whose technology has developed rapidly in recent years, is the use of solar energy for the simultaneous generation of various products. Therefore, in this research, a multigeneration system with several subsystems is introduced. The proposed system includes a solar energy collector to receive thermal energy, two thermal energy storage tanks, an organic Rankine cycle, and a Kalina cycle to generate electricity, a multi-effect distillation unit to produce fresh water, an electrolyzer to produce hydrogen, as well as heat recovery for hot water and hot air generation. In this multigeneration system, the cooling unit is designed with the help of a thermosyphon. The performance of the proposed system is studied from energy, exergy, environmental, and exergoeconomic viewpoints using Aspen HYSYS and EES software. The obtained results show that due to the addition of the thermosyphon unit to the refrigeration system, the exergy efficiency increases from 55.62% to 70.26%. As a result of this combination, the performance of the whole system is improved and the amount of costs are reduced. In addition, the parabolic collector system has the highest exergy destruction ratio, 39%, among the subsystems. Furthermore, the results of the exergoeconomic analysis indicate that the PEM water heater with 33.3% and the ejector with 22.7% own the highest cost destruction rates.

Multi-objective optimization of solar energy systems for electricity and hot water generation in collective residential buildings considering the power-to-heat concept

An extremely important question concerning the planning and installation of solar systems in residential buildings is how to optimally size solar photovoltaic (PV) systems and solar water heating systems. This question is challenging especially if there is an interest to explore the excess PV generation to produce of portion of the thermal load and assist the solar water heating system under the so-called power-to-heat concept. A tri-objective optimization process is introduced to find the best size of solar PV panels, thermal collectors and storage capacity for a Moroccan collective residential building. Modelling and optimization investigations rely on high-resolution time step over a one year operation, considering pertinent life-cycle objective functions which are the Levelized Cost of Electricity (LCOE), Levelized Cost of Heat (LCOH) and the Renewable Energy Penetration (REP). The collective residential building is located in Fez, Morocco. Instantaneous variations of PV power generation, thermal collector efficiencies, water temperature in the storage tank, auxiliary power and power imports from the grid are determined at each time step. The developed numerical tool can be used in other buildings categories and in other locations revealing a huge interest in improving the feasibility and competitiveness of solar energy systems in buildings. For total annual electric and thermal loads of 96.31 MWh/year and 32.88 MWhth/year, respectively, the optimum design consisted on 25 kWp PV capacity, 18 m2 of thermal collectors and 1.8 m3 of thermal storage. The corresponding LCOE, LOCH and REP are determined to be 17.8 c$/kWh, 3.5 c$/kWh and 45.8%, respectively. The self-sufficiency ratio, self-consumption ratio and solar thermal fraction for the final optimum design are 30.6%, 69.7% and 90.1%, respectively.

Thermal performance and design analysis of U-tube based vacuum tube solar collectors with and without phase change material for constant hot water generation

Solar water heaters are the most promising technology, and they can be effectively used for hot water generation in cold climatic conditions. The moto of this research is the design and development of two compact vacuum tube solar collectors (VTSCs): (i) modified copper finned U-tube based VTSC filled with PEG6000 as a phase change material (PCM). However, it integrates heat transmission and storage capabilities into a unit (ii) conventional U-tube inserted VTSC without PCM. The developed VTSC with PCM was operated under dual (simultaneous and mid-day charging) modes, and their performance was compared with the conventional system at various flow rates. This study explored the design analysis, working principle, and the outcome of fixed mass flow rates on the system's thermal output. The results display that the daily energy output of the developed collector with PCM is 81.54–89.74 % for simultaneous mode and 78.21–86.52 % for mid-day charging mode. Whereas the daily energy output of conventional solar collector without PCM was 69.31–75.54 % for set mass flow rates. The highest thermal efficiency was around 89.74 % for U-tube inserted VTSC with PCM (simultaneous mode) at a high flow rate (30 LPH). The global heat transfer coefficient (UL) was maximum at a low mass flow rate (10 LPH) for conventional system without PCM, followed by mid-day charging and simultaneously operated VTSC with PCM. After comparing both systems, it is found that using PCM in VTSC improves the daily energy efficiency and increases the operating time for 3–4 more hours than conventional system. This analysis revealed that the developed U-tube inserted VTSC with PCM can substantially supply the hot water demand for domestic applications constantly at night/off sunshine hours.

Techno-economic analysis of green energy resources for power generation & direct use by preserving near-wellbore geothermal gradient

Closed-loop fluid circulation in wellbores has gained considerable attention for harnessing the earth's thermal energy. Recent studies with analytical and numerical models show that geothermal gradient and well depth constitute the two most consequential variables in fluid output temperature at the surface. This study presents a new strategy for managing geothermal-gradient cooling to ensure more prolonged operation by adopting another energy source, such as solar or wind, with a day/night cycle over the years. In other words, the fluid circulation will occur at night, while the solar or wind source will operate in the daytime. Well-depth and geothermal gradients dictate which geographic area provides the best opportunity for power generation or hot water production to meet various industrial needs. Economic tools, such as Net Present Value and Levelized Cost of Electricity, helped gauge their strengths and limitations, thereby offering business decisions objectively.Considering a 20-year power generation period, this study provides some pragmatic lessons. For example, retaining the near-wellbore geothermal gradient is essential for assuring about 130 °C for the binary cycle. We can attain this objective with a 12-h fluid-circulation cycle by juxtaposing a second well or a solar/wind source for a day/night cycle. Also, besides being a safety net, a power grid can aid the economic value proposition in this energy-transition phase. The generation of hot water for direct industrial usage for low-geothermal prospects also becomes economically viable, particularly in repurposing abandoned wells. These industries include food and agriculture, requiring 60 to 85 °C.

Modeling and optimization of fuel cell systems combined with a gasifier for producing heat and electricity

In this research, a proton-conducting membrane fuel cell is used in conjunction with a gasifier for producing electricity with air considered as the gasification agent. The simultaneous electricity, heat, and hot water generation of these two when coupled with an Organic Rankine Cycle (ORC) installed within a Thermoelectric Generator (TEG) was studied. Additionally, to utilize the electricity generated from various parts of the process; i.e. the fuel cell, organic Rankine cycle turbine, and the thermoelectric generator, the reverse osmosis (OR) water desalination unit was coupled to the process. The aforementioned system was studied and analyzed based on thermodynamic and thermos-economic aspects. A parametric study was also carried out to analyze the effect of main factors on power output, energy/exergy yield, and the total cost of each system. Finally, a dual objective optimization was achieved by taking the main factors into consideration and using a genetic algorithm. Results indicated that the work generated by the system was not significant; however, the amount of hot water produced was relatively promising. Based on exergy and exergoeconomic evaluation, the After-Burner is an important non-renewable energy source while the fuel cell has a higher inefficiency cost which could be due to low work generation. Results indicate that the moisture in the biomass and the figure of merit, are important parameters that have to be kept as low as possible. The energy yield of the fuel cell was calculated to be 45.05%. Additionally, considering the optimized operating point, pure power output and system cost rate will be 1.81 KW and 5.15 $/hr respectively.

Installation of an ultrafiltration plant in a multi-family house to reduce the hot-water temperature and energy demand: A case study in Germany

Hot-water generation complicates energy efficiency and emission reduction efforts in buildings. High water temperatures are designated for thermal disinfection to prevent human harm from pathogenic microorganisms. Therefore, almost 200 Mt CO2 are annually emitted in the US, Germany and Canada. Heat pumps can replace fossil energies. However, lower temperatures are required to enhance efficiencies.In this case study, the hot-water temperature of the drinking-water installation of a retrofitted multi-family house was decreased by 5 °C to 50 °C. For physical separation of microorganisms, an ultrafiltration plant was installed in the hot-water circulation. To control hygienic safety, microbiological conditions were assessed by laboratory methods such as the cultivation of Legionella spp. and counting of total cells using flow cytometry. The filtrated hot-water was constantly Legionella-free. The cleaning effect of ultrafiltration was 91.15%. Cold-water was not filtrated so that contaminations occurred. As cold- and hot-water pipes (including circulation) are embedded in the same riser strands, temperature transfer occurred promoting bacterial growth. An energy demand calculation revealed that heat losses of the distribution network accounted for 55.25% of the total heat quantity required for hot-water generation. The actual heat up process of water and storage losses constituted 42.74% or 2.01%. Lowering the water temperature by 5 °C saved 7355 kWh yr−1 (equiv. to 1.77 t CO2e yr−1) in this multi-family house. Extrapolation of this case building results in a saving potential of 7.78–14.50 TWh yr−1 (equiv. to 1.87–3.48 Mt CO2e yr−1) in Germany alone, if the energy source is natural gas.

Design and calculation of an environmentally friendly carbon-free hybrid plant based on a microgas turbine and a solid oxide fuel cell

This is an overview of a hybrid power plant design and predesign analysis, including a microgas turbine with heat recovery, a high-temperature fuel cell, and a carbon dioxide capture system. A hybrid installation model is presented, taking into account the compatibility and technological limitations of the main components. The material and heat balance calculation of a hybrid power plant is performed depending on the input parameters under partial load conditions. In order to create a decarbonized highly efficient energy production process and in connection with the need to minimize the negative impact of carbon dioxide on the environment, the article presents the developed technologies for carbon dioxide utilization and a carbon adsorption unit as a hybrid power plant part. The hybrid power plant is a carbon-free mini thermal power plant with integrated electricity, steam, and hot water generation and more than 90% total efficiency.

Energy, exergy, energy-saving, economic and environmental analysis of a micro-gas turbine-PV/T combined cooling, heating and power (CCHP) system under different operation strategies: Transient simulation

A micro-gas turbine (MGT) combined cooling, heating and power system coupled with low concentrating photovoltaic/thermal-heat hump (LCPV/T-HP) and absorption chiller is proposed in this study. LCPV/T is used as the heat source of HP to realize mutual promotion. The performance of CCHP system under different operation strategies is dynamically simulated and analyzed by TRNSYS software from energy, exergy, energy-saving, economy and environment. The results demonstrate that both high temperature water source heat pump (HWHP) and low temperature water source heat pump (LWHP) achieved better COP in following electric load (FEL) mode. The average COP of HWHP and LWHP are 22.69% and 4.75% higher than the rated COP, respectively. Annual total cost per unit building area (ATCUBA) and carbon dioxide emissions per unit building area (CDEUBA) are also more advantageous in FEL mode, while primary energy consumption per unit building area (PECUBA), ATCUBA and CDEUBA seems less preferable in following thermal load (FTL) mode. The exergy efficiency and energy efficiency of the system in FEL mode are 19.96% and 41.90% in summer, and 25.13% and 59.36% in winter. Additionally, the equipment with higher exergy loss is mainly LCPV/T, gas-fired boiler, absorption refrigeration unit, MGT and hot water generator under the three operation strategies.

Numerical performance of a water source transcritical CO2 heat pump with mechanical subcooling

In order to improve their efficiency, transcritical CO2 heat pumps need to resort to the use of a subcooling method. Among the different subcooling methods, dedicated mechanical subcooling (DMS) systems and internal heat exchangers (IHX) are currently the more promising technologies. This paper presents a numerical study of a transcritical water source CO2 heat pump during hot water generation using different subcooling methods. Ten different configurations, including both, IHX and DMS, separately and combined in different layouts, some of them not studied previously, are analyzed numerically under the same operating conditions in order to compare their performance. A description of the numerical model is presented: compressors are modeled using the performance curves provided by their manufacturers, expansion valves are modeled as isenthalpic, and heat exchangers are modeled by deriving correlations for the evaporation/condensation pressure and heat transfer rate obtained using a 1D cell-by-cell discretization method previously applied to all heat exchangers. Results are presented for different water heating conditions and show that in most configurations analyzed, the use of a DMS does not improve the performance of the system compared to the base system with IHX. There is only an improvement in the efficiency for two of the configurations analyzed, those in which the main CO2 cycle and the DMS cycle are coupled by the water flowing first through the evaporator of the auxiliary cycle and then through the gas cooler of the main cycle. Specifically, compared to the base cycle with IHX, the configuration that provides the best results (Conf. F* according to the nomenclature used in this work) gives average improvements of around 26% in efficiency and almost 160% in the heating capacity, while the optimum gas cooler pressure is reduced by an average of 12%. Even more, compared to the best performance system previously studied by other authors (indirect DMS without IHX, Conf. F in this work) this configuration improves the efficiency by almost 8.5%, with a decrease in the total capacity lower than 1% and similar gas cooler pressure. The results also show that the auxiliary compressor capacity and the way in which the water is distributed among the main and the auxiliary cycle have an important influence on the efficiency of the system, although that influence depends on the configuration studied. For the configuration that provides the best efficiency (Conf. F*), the optimum efficiency is obtained when the auxiliary compressor capacity is similar to the capacity of the main compressor (55% of the total heating capacity comes from the auxiliary cycle), and the water is mostly heated in the auxiliary cycle (85% of the water flow heated in the condenser of the auxiliary cycle, 15% heated in the gas cooler of the main cycle).

Parametric assessment of a novel renewable energy based integrated plant with thermal energy storage for hydrogen generation and cleaner products

Renewable energy-supported multigeneration plants and energy storage systems have important in reducing carbon emissions and also effective use of energy sources. In this study, both a renewable energy source-based energy storage process and a newly developed multigeneration plant are studied through detailed thermodynamic analysis. Here, the energy required for the compressed air storage unit is obtained from the hybrid system of solar and wind energy, and the stored compressed air reacts with natural gas in the Brayton cycle and goes to the multigeneration cycle. Furthermore, the key aim of this research is the examination of a multigeneration system for power, heating, cooling, hot water, and hydrogen generation using energy and exergy efficiency methods. The investigated model includes a thermoelectric generator, an organic Rankine cycle, a hydrogen production and liquefaction unit, a cooling system with an ejector, a Brayton cycle, a Rankine cycle with three turbines, and a compressed air energy storage unit with solar photovoltaic and wind turbines. Moreover, to observe the impact of some substantial design variables on the proposed subsystems and the entire plant’s performance and irreversibility rate, thermodynamic analysis is applied parametrically. In light of assessment findings, the net power generation rate of the entire system is 31,308 kW at 25 °C reference condition. Also, the net hydrogen generation capacity, cooling capacity, and heating capacity of the total plant are 0.0499 kg/s, 3650 kW, and 4281 kW. In conclusion, the energetic and exergetic efficiencies of the entire model are determined as 0.5258 and 0.4867.

Impact of an internal heat exchanger on a transcritical CO2 heat pump under optimal pressure conditions

Transcritical R744 (CO2) heat pumps are a low-GWP high-efficiency alternative for domestic hot water generation and space heating. For high set-point temperatures, however, the COP drops and the optimum operating pressure increases. For this reason, the effect on system performance achieved by the inclusion of an Intermediate Heat Exchanger (IHX) is analyzed in depth. This is carried out by means of a numerical-experimental approach in which the effectiveness of the IHX and other characteristic parameters of the heat pump cycle are studied as a function of the IHX heat transfer area. The numerical modeling of the heat pump components is implemented for transient simulations of system heating-up process. Experimental tests with and without IHX are carried out with a water-to-water heat pump that feeds an accumulator tank, to assess its influence on the system’s COP and the electrical consumption. Simulations reveal that improving the efficiency of the IHX, by increasing the exchange area, improves the system’s performance. For the cases with higher IHX exchange area, the optimum pressure in the system is lower. For the heating experiments, the resulting thermodynamic COP is 7.55 % higher in the case with IHX, while the effective COP increases by 4.26 %. In consequence, the use of the IHX is recommended for the conditions analyzed.

A Conceptual Design and Analysis of a Novel Trigeneration System Consisting of a Gas Turbine Power Cycle with Intercooling, Ammonia–Water Absorption Refrigeration, and Hot Water Production

In this study, the performance of a novel trigeneration system with a gas turbine prime mover, an ammonia–water refrigeration system, and a hot water generation system is investigated from thermodynamic and economic standpoints. The effects of various operating conditions on energy efficiency and the levelized cost of energy are investigated. The proposed system has a production capacity of 45.4 kW power, 14.07 kW cooling rate, and 16.32 kW heat rate. The efficiency of the gas turbine cycle is 49.7%, and it becomes 83.0% after the implementation of the trigeneration system. Through combined heating, cooling, and power generation, primary energy input and the CO2 emissions will be 49% lower compared to separate production. According to the exergy analysis, the combustion chamber is the main component where the greatest exergy destruction occurs. Sensitivity analysis revealed that an increase in the ambient temperature results in a decrease in the energy utilization factor and the net power output. The LCOE of the system is around 0.02 $/kWh, whereas the unit price of the local electricity from the grid is 0.09 $/kWh. The payback period of the absorption sub-cycle is between 4 months and 4 years, depending on the annual operation time of the chiller.

Design of a Pyroacuotubular (Mixed) Boiler for the Reduction of Flue Gas Emissions through the Simultaneous Generation of Hot Water and Water Steam

Environmental protection is a continuous challenge that requires innovating the combustion process of boilers that emit polluting gases. This research proposes a novel pyroacuotubular (mixed) boiler design that reduces the emission of combustion gases by hot water and steam. The applied methodology considers the dimensioning-construction, modification, and analytical calculation of water volume, metallic masses, heat for hot water and steam generation, and combustion gases. The Ganapaty method of heat transfer is applied to prioritize the velocity of gas displacement, the pressure drop along the pipe, and its application on surfaces. In the parallel generation of hot water and steam, a mass of CO2 (1782.72 kg/h) and CO (5.48 kg/h) was obtained; these masses were compared with the results of the proposed design, obtaining a reduction in the mass of gases emitted to the environment in hot water CO2 (44.35%) and CO (44.27%); steam CO2 (55.65%) and CO (55.66%). A significant reduction was achieved in the simultaneous generation of hot water and steam compared to the individual generation, which shows that the simultaneous generation of the pyroacuotubular (mixed) boiler reduces the emission of combustion gases.

Overcome data gaps to benchmark building stocks against climate targets related to the EU taxonomy and other decarbonisation initiatives

National disclosure regulation is more and more flanked by stricter requirements of climate reporting. Industry stakeholders with more than 250 employees will for example be required to report on the share of their CAPEX and OPEX that is in line with the 2050 climate targets of the EU. Financial institutions are required to declare how much of their investment is in 2050 target compatible assets. Investment in buildings is an important part of such reporting and there is need of a robust approach and method to be used. The presented project developed such an approach. With reference to the work of the EU Technical Expert Group on Sustainable Finance and the Climate Bond Initiative (CBI), generally applicable criteria for buildings have been determined and calculated for the example of Switzerland. They are based on a best-in-class approach. While the EU Technical Taxonomy refers to the top 15% of buildings in terms of primary energy demand, CBI uses CO2-emissions as a benchmark. To compare the current state of buildings sector with these criteria, a distributional building stock model is used, which also addresses the fact that the data availability on energy efficiency and climate compatibility of the building stock is unsatisfactory in many European countries including Switzerland. To be easily applicable in practice, the criteria are mainly based on two dimensions: on the one hand, on the requirements of codes (in Switzerland the model regulations of the Cantons, MuKEn) and widely used standards and labels (Minergie, GEAK), and on the other hand, on the energy sources used for the generation of space heat and hot water. The study shows that ecologically sustainable, climate-compatible building financing can always be assumed in Switzerland if one of the following two criteria are met for new buildings: multi-family, office or other non-residential buildings according to Minergie from 1998 on, MuKEn from 2000 on or GEAK B that use heat-pumps, wood, pellets or solar energy. Or, any building with Minergie from 2009 on label, MuKEn 2014 or GEAK A that use heat pumps, wood, pellets, solar energy or district heating based on non-fossil energy. In the context of increased pressure on resources, it is important to acknowledge the climate-compatibility of older buildings as well (and to not only consider newly which would generate a bias towards resource intensive building of new houses).

Techno-economic analysis of a hybrid photovoltaic-thermal solar-assisted heat pump system for domestic hot water and power generation

This work investigates the techno-economic performance of a hybrid photovoltaic-thermal (PVT) solar-assisted heat-pump system for covering the electrical and hot-water demands of a three-bedroom terraced house in Belfast, United Kingdom with four occupants. This system combines a water-to-water heat pump with PVT panels to deliver both electricity and hot water for domestic consumption. The PVT array provides a source of low-temperature heat for the water-to-water heat pump, while cooling the PVT array and thus preventing the electrical efficiency degradation that occurs at higher operating temperatures. Analyses have been performed for PVT arrays of different size, including 12-panel, 20-panel and 24-panel systems. Results show that, thanks to its lower initial investment cost, the most economically viable system configuration for the household considered in this work is based on a 12-panel PVT array covering a total area of 16.3 m2. This system has the potential to produce 2.4 MWh of (gross) electricity and 2.0 MWh of hot water per year, which is equivalent to just over 30% of the electrical and 80% of the hot-water demands of the household under consideration, with the PVT array acting to reduce the electricity consumption of the heat pump in the heating system by a little over 60%. The system has lower recurring yearly costs relative to current household energy systems that use electricity from the grid and natural gas, despite having higher investment costs. It is also found that the system can reduce the investigated household's annual CO2 emissions by 910 kg per year (about 18 tonnes over a lifetime of 20 years) and that, with an electricity generation incentive rate of 5 p/kWh and a heat generation incentive rate of 21 p/kWh, the aforementioned system has a discounted payback period of 14 years.

Economics of Implementing Solar Thermal Heating Systems in the Textile Industry

This paper analyzes the potential of solar thermal systems for being employed for process heating in cotton-based textile industries. The technological capability of a flat plate collector (FPC) to meet the solar industrial process heating (SIPH) requirement in yarn production is assessed. Moreover, the usability of a parabolic trough collector (PTC) in meeting the technological mandates of SIPH in fabric processing units is critically examined. Further, this paper reports the findings of a study on the potential cost advantage of solar process heating over the conventional process heating practices in cotton-based textile industries. The approach involves the selection of the locations of sample textile industries and the employable solar collector technologies, as well as assessment of financial reward, if any. Eight different cotton-based textile industries located in different geographical domains (in India) are selected. The selected textile industries are situated within the textile hubs existing in different states across India. Analysis of technoeconomic benefit derivable in selected textile industries using FPC for hot water generation and PTC for steam generation is presented. In the case of FPC-based SIPH systems, the maximum value of solar fraction is estimated to be 0.30 and the corresponding estimation for the levelized cost of useful thermal energy (LCUTE) delivered comes out as INR 790/GJ to INR 1020/GJ. On the other hand, in case of parabolic-trough-solar-concentrator-based SIPH systems, LCUTE is estimated in the range of INR 1030/GJ to INR 1610/GJ. From a critical analysis of financial viability in consideration of related factors such as payback time and return on investment in SIPH, it appears that the SIPH systems for hot water generation may be a good choice, whereas SIPH systems for steam generation are seen to have longer payback periods and lower returns on investment, and, therefore, it seems that adequate financial support from central and state governments with additional supports from bilateral or multilateral organizations may enable them to become a sustainable technology option.

Experimental research on the performance of BIPV/T system with water-cooled wall

Solar photovoltaic/thermal building integrated power/heat technology (BIPV/T) can provide both electricity and heat to buildings, which is important for improving the efficiency of solar energy utilization and reducing building energy consumption. In this paper, a BIPV/T system with water-cooled wall is proposed. The water-cooled wall heat exchanger is not in direct contact with the PV module, and uses air to dissipate heat from the PV module, which in turn heats domestic water, and can provide hot water or hot air to the building as needed. This paper experimentally investigates the system’s ability to produce domestic hot water and power generation performance, with an average power generation efficiency of 12.6% for the whole day and providing 35 °C domestic hot water for more than 7 h. The results of this paper have some guiding significance for the efficient operation of BIPV/T.

Thermal and hydraulic characteristics of a parabolic trough collector based on an open natural circulation loop: The effect of fluctuations in solar irradiance

This study introduces a novel open natural circulation loop-based parabolic trough collector capable of operating in dual-mode and is tested experimentally for four days of solar insolation under three common climatic conditions. The tests are conducted in two modes viz hot water and low enthalpy steam generation. Both modes shows stable thermo-hydraulic characteristics with Start-up oscillations. Hot water mode experienced single mode thermal oscillations with 0.015 Hz having a decay ratio of 0.45. Steam generation mode experienced little fluctuation in outlet temperature with the insolation. However, it affects mass flux in both modes. Nevertheless, all fluctuations are stable and die out faster. Type-I instability is observed in two-phase flow transition in the receiver tube for both the modes. Overall efficiency is estimated at 68%, which is almost consistent throughout the day. The efficiency and total heat loss are also observed to be dependent on total insolation. In Hot water mode, the system can produce 150 L of hot water at 97.5 °C, and 8.7 kg of total steam in Steam generation mode. The results also show that proposed Parabolic Trough Collector based on Open natural Circulation loop is suitable for agricultural and small-scale industries where hot water or low-enthalpy steam at temperatures of 80–110 °C are required.

Experimental performance of a novel scraped surface heat exchanger for latent energy storage for domestic hot water generation

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

Testing and Performance Validation of Ordinary Evacuated Tube Based Parabolic Trough Collector for Low Enthalpy Process.

In this paper, a parabolic trough collector is designed and fabricated, and its thermal performance is evaluated for hot water generation. Theparabolic trough collector was built with a 90o rim angle with a small concentration ratio of 5.5, and the collector aperture area is1.7 m2.Both side open ordinaryevacuatedglass tube and acrylic sheet were usedas a receiver and reflective surface,respectively.Siemens NX has been used to simulate the maximum wind load of 1000 N. The thermal output of the collector is evaluated for close and open circuits as per ASHRAE 93 1986 (RA 91) standard. The achieved maximum efficiencies