This study proposes a novel solar wastewater treatment system comprising efficient solar energy absorption and contaminant separation processes. The proposed system aims to overcome the drawbacks of ...previous membrane-based systems especially high energy demand and lack of a complex wastewater consideration. Synthetic wastewater was prepared and the solar system was experimentally analysed under climatic conditions of Perth, Western Australia in summer and winter. The findings revealed that the solar thermal efficiency of the system fluctuated mainly around 63% in summer and 52% in winter. The system reached its maximum exergy efficiency in the afternoon with 5.54% and 4.82% for summer and winter, respectively. Moreover, the highest rate of treated water in summer and winter were 4.21 and 2.85 L/m2h, respectively. The results also indicated that the removal percentages of Fe, Mn, Cu, Na, K, and Ca were 96, 89, 96, 100, 100, and 94%, respectively. In addition, almost 100% of organics and nutrients were removed. The highest recorded gained output ratio and overall efficiency were 0.71 and 49.6% in summer, while these parameters were 0.58 and 46.6% in winter. Overall, the proposed solar-driven membrane-based system is a feasible and efficient option in the separation of contaminants from wastewater.
•A novel heat pipe solar membrane-based wastewater treatment system was proposed.•The proposed system was effective in separation of hazardous metals from wastewater.•Almost 100% of organics and nutrients was removed from wastewater.•Average solar thermal efficiency of 63% in summer and 52% in winter were achieved.•Maximum treated water production rate was 4.21 L/m2h in summer.
Um unsere Gebäude zukünftig zu klimatisieren, müssen wir erneuerbare Energien nutzen. Ein wichtiger Baustein auf dem Weg dorthin wird die Wärmepumpe sein. Diese nutzt als Energiequelle die ...verschiedenen Alternativen der erneuerbaren Energie. Die Leistungsfähigkeit der Wärmepumpe wird von der Temperaturdifferenz zwischen Quelle und Raumtemperatur bestimmt. Je geringer dieser Wert ausfällt, umso geringer ist der Stromverbrauch. Das vorgestellte Verfahren stellt eine Form von Zwischenspeicher zum Sammeln von Strahlungsenergie dar. Dabei wird die Temperatur in dem Speicher auf ein höheres Niveau als die Ausgangsquellen angehoben. Wird Wärmeenergie gebraucht, kann die Wärmepumpe immer auf eine Quelle mit hohem Temperaturniveau zurückgreifen. Die vorgestellte Energiesäule ist in der Lage, Energie aus Strahlung auf einem hohen Temperaturniveau einzusammeln. Die beiden zugehörigen Wärmespeicher bevorraten die erzeugte Wärmeenergie als Input für die Wärmepumpe im Heizfall. Sofern überschüssiger Strom vorhanden ist, wird das Temperaturniveau in den beiden Speichern angehoben.
Translation
A uniform and constant energy source with the newly developed energy column
In order to air‐condition our buildings in the future, we must use renewable energies. The heat pump will be an important factor on the way there making use of various renewable energy alternatives as an energy source. The performance of the heat pump is determined by the temperature difference between the source and room temperatures. The lower this value is, the lower the power consumption. The method presented here represents a form of intermediate storage for collecting radiant energy. The temperature in the storage is raised to a higher level than the output sources. If thermal energy is needed, the heat pump can always rely on a source with a high temperature level. The presented energy column is able to collect energy from radiation at a high temperature level. The two associated heat storage units store the heat energy generated as input for the heat pump when heating. If there is excess electricity, the temperature level in the two storage units is raised.
The present paper deals with an analysis of the building integrated photovoltaic thermal (BIPVT) system fitted as rooftop of a building to generate electrical energy higher than that generated by a ...similar building integrated photovoltaic (BIPV) system and also to produce thermal energy for space heating. A thermodynamic model has been developed to determine energy, exergy and life cycle cost of the BIPVT system. The results indicate that although the mono-crystalline BIPVT system is more suitable for residential consumers from the viewpoint of the energy and exergy efficiencies, the amorphous silicon BIPVT system is found to be more economical. The energy and exergy efficiencies of the amorphous silicon BIPVT system are found to be 33.54% and 7.13% respectively under the composite climatic conditions prevailing at New Delhi. The cost of power generation is found to be US $ 0.1009 per kWh which is much closer to that of the conventional grid power.
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.
In this work, the thermo-fluid performance of a liquid flat-plate collector (FPC) has been analyzed using experimental and computational methods. A closed-loop active flat-plate solar water heater ...(AFPSWH) was tested under quasi-static and laminar flow operating conditions, where a maximum instantaneous collector efficiency of 62.82% and an outlet temperature of 45.2°C were attained in the winter with flow rates of 0.012 and 0.004 kg/s, respectively. Raising the flow rates from 0.004 kg/s to 0.008 and 0.012 kg/s reduces the energy loss parameter F
R
U
L
by 23.77% and 34.61%, whereas the absorbed energy parameter F
R
(τα)
n
improves by 10.48% and 21.55%, respectively. The suggested axisymmetric numerical model was validated with outcomes of an in-house developed lab scale experimental setup, with less than 1.5% deviations for all studied cases. In addition, the overall thermal efficiency of the solar thermal system (STS), Nusselt number (Nu), and friction factor (f) have been analyzed for a comprehensive understanding of the system's thermo-fluid performance.
In this Paper solar desiccant air conditioning system integrated with cross flow Maisotsenko cycle (M-cycle) indirect evaporative cooler is used to investigate the performance of whole system in ...different range of parameters. Solar evacuated tube electric heater is used to supply the regeneration temperature to the desiccant wheel, whereas, Desiccant Wheel (DW) and M-cycle is used to handle latent load and sensible load separately. Major contribution of this research is to predict system level performance parameters of a Solar Assisted Desiccant Air Conditioning (Sol-DAC) system using Radial Basis Function Neural Network (RBF-NN) under real transient experimental inlet conditions. Nine parameters are mainly considered as input parameters to train the RBF-NN model, which are, supply Air temperature at the process side of desiccant wheel, supply air humidity ratio at process side of the desiccant wheel, outlet temperature from the desiccant wheel at process side, outlet humidity ratio from the desiccant wheel at process side, regeneration temperature at regeneration side of the DW, outlet temperature from the heat recovery wheel at process side, outlet humidity ratio out from the Heat Recovery Wheel (HRW) at process side, temperature before heat recovery wheel regeneration side of the system, humidity ratio before heat recovery wheel regeneration side of the system. Four parameters are considered as the output of the RBF-NN model, namely: output temperature, output humidity, Cooling Capacity (CC), and Coefficient of Performance (COP). The results of the RBF-NN model shows that the best Mean Squared Error (MSE) and Regression coefficient (R) for outlet temperature prediction are 0.00998279 and 0.99832 when regeneration temperature is 70 °C and inlet humidity at 18 g/kg. Best MSE and R for predication of outlet humidity are 0.0102932 and 0.99485 when the regeneration temperature is 70 °C and inlet humidity at 16 g/kg. Best MSE and R for predication of COP are 0.0106691 and 0.9981 when the regeneration temperature is 70 °C and inlet humidity 12 g/kg. Best MSE and R for predication of CC are 0.0144943 and 0.99711 when the regeneration temperature is 70 °C and inlet humidity 14 g/kg. Experimental and predicted performance parameters were in close agreement and showed minimal deviation. Investigations of predicted results revealed that trained RBF-NN model was capable of predicting the trend of output result under the varying input condition.
This article deals with the impact of including transverse ribs within the absorber tube of the concentrated linear Fresnel collector (CLFRC) system with a secondary compound parabolic collector ...(CPC) on thermal and flow performance coefficients. The enhancement rates of heat transfer due to varying governing parameters were compared and analyzed parametrically at Reynolds numbers in the range 5,000-13,000, employing water as the heat transfer fluid. Simulations were performed to solve the governing equations using the finite volume method (FVM) under various boundary conditions. For all Reynolds numbers, the average Nusselt number in the circular tube in the CLFRC system with ribs was found to be larger than that of the plain absorber tube. Also, the inclusion of transverse ribs inside the absorber tube increases the average Nusselt number by approximately 115% at Re = 5,000 and 175% at Re = 13,000. For all Reynolds numbers, the skin friction coefficient of the circular tube with ribs in the CLFRC system is larger than that of the plain absorber tube. The coefficient of surface friction reduces as the Reynolds number increases. The performance assessment criterion was found to vary between 1.8 and 1.9 as the Reynolds number increases.
This study evaluated the effect of an organic Rankine cycle (ORC), powered by various renewable heat sources, on enhancing the primary energy benefits in a liquid desiccant (LD) and indirect and ...direct outdoor evaporative cooling-assisted air system (LD-IDECOAS). Combining an LD-assisted air conditioning system with the ORC, which uses renewable or waste heat sources, may be beneficial in terms of energy saving and environment efficiency. However, only a few studies have addressed the benefits of integrating the ORC with this air conditioning system as the heat source for the ORC. A solar thermal system, district heat source, and conventional boiler were used respectively in a 2-kW ORC which was integrated with the LD-IDECOAS to establish three system cases, and a comparative investigation was conducted. The power and heat generated by the ORC are supplied to the LD-IDECOAS to satisfy the power and solution heating demands, respectively. By performing a detailed energy simulation, the primary energy consumption in each ORC-integrated case was calculated during the cooling season and compared with that of a conventional LD-IDECOAS driven by grid power and a gas boiler. The results revealed that three ORC-integrated system cases consumed additional electric power compared with the base case (21.6% more electric power consumed in case 1 and 20.0% more electric power consumed in cases 2 and 3). Additional heat input to the ORC evaporator was also required, however, the ORC-integrated LD-IDECOAS powered by a solar thermal system (case 1) and district heat source (case 2), which are renewable energy sources, achieved a primary energy saving of 15.7% and 35.4%, respectively, compared with the base case. In conclusion, the district heat source was more feasible than the other heat sources considered in this study, achieving the best primary energy saving (35.4%) and CO2 emission reduction (23.9%).
•A solar thermal system, district heat source, and boiler were applied as the heat sources in an organic Rankine cycle (ORC).•The ORC was integrated with a liquid desiccant and evaporative cooling system.•Primary energy consumption and CO2 emission of each case were compared.•Cases using renewable energy as the ORC heat source presented an increase in energy savings and a reduction in CO2 emission.•For the case of a district heat source, the best energy savings (35%) and CO2 reduction (24%) were obtained.
•A specularly reflective cavity placed over a solar absorber reduces radiative losses.•Cavity performance is sensitive to cavity size and cavity-absorber alignment.•Radiative loss reduction validated ...with proof of concept experiments.•Losses from near blackbody absorber reduced by over 75%.•Receiver efficiency shown to be comparable to idealized wavelength selective absorber.
A principal loss mechanism for solar receivers in solar-thermal systems is radiation from the absorbing surface. This loss can be reduced by using the concept of directional selectivity in which radiation is suppressed at angles larger than the incident angle of the sunlight striking the absorber. Directional selectivity can achieve efficiencies similar to high solar concentration, without the drawbacks associated with large heat fluxes. A specularly reflective hemispherical cavity placed over the absorber can reflect emitted radiation back to the absorber, effectively suppressing emission losses. An aperture in the cavity will still allow sunlight to reach the absorber surface when used with point focus concentrating systems. In this paper the reduction in radiative losses through the use of a hemispherical cavity is predicted using ray tracing simulations, and the effects of cavity size and absorber alignment are investigated. Simulated results are validated with proof of concept experiments that show reductions in radiative losses of more than 75% from a near blackbody absorber surface. The demonstrated cavity system is shown to be capable of achieving receiver efficiencies comparable to idealized spectrally selective absorbers across a wide range of operating temperatures.
•Designing an optimal controller for the heat pump in solar thermal systems is challenging.•The robust control method is employed to design a novel robust feedforward controller.•The overall control ...structure consists of the separated feedback and feedforward parts.•The heat pump consumes the minimum electricity under varying disturbance conditions.•The domestic hot water temperature is kept within the desirable range.
In this paper, an optimal control strategy is developed for managing a heat pump in an integrated solar thermal system. Solar thermal systems usually operate with both feedback and feedforward controllers. The focus of many existing studies in solar thermal system applications has been on the feedback part, while less effort has been made to improve the performance of the feedforward part. This paper introduces a novel robust feedforward controller as a sub-controller of an optimal controller for operating a heat pump integrated with the solar thermal system. In a simulation environment, the optimal control structure is implemented, and the performance of the robust feedforward controller is compared with a simple feedforward controller. Regarding the electrical power consumption, the simulation results demonstrate that the optimal control structure with the proposed robust feedforward controller outperforms the control structure with the simple feedforward controller.
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