• Energy Research

Subcooled compressed air energy storage system is a trigeneration technology that has been recently introduced to the literature. In the charging mode, the system stores the surplus power of a renewable energy system in the form of compressed air in a cavern and generates much heat as well. In the discharging mode, when the renewable power plant demands extra electricity, the system reclaims the compressed air to be expanded through a specific type of turbine and thereby generates electricity as well as a large amount of cold. At nominal load, when all the components are working at their optimal states, a high coefficient of performance of about 1.5 has been achieved for the system over a complete charging-discharging round. This paper, however, investigates thermodynamically and environmentally the performance of this technology while working at off-design conditions. For this, realistic performance curves for various components of the system are employed and the system operation is simulated for various operational conditions. The results show that the storage unit is best to work on its highest possible charging-discharging loads; otherwise, the overall efficiency would fall remarkably. The trigeneration/storage system overall performance coefficient will decrease to 1.27% and 1.05% if the operational load drops to 50% and 10%, respectively.

The importance of MHD nanofluid has increased due to its significant thermal characteristics. Influence of Joule heating on nanomaterial heat transfer in a duct is reported. In order to nanofluid simulation, Buongiorno model is incorporate. Governing formulas are turn into ODE by means of similarity transformation and then solved by Adomian Decomposition Method (ADM). Outputs for various values of Pr, Ha, Ec, Buoyancy ratio, Schmidt number, suction parameter and Brownian motion parameters are depicted. Our outcomes indicated that temperature improves with augment of viscous dissipation but it reduces with growth of Ha. Skin friction coefficient rises with augment of Ec while it reduces with augment of magnetic forces. Keywords: Magnetic field, Nanofluid, Induced magnetic field, ADM, Joule heating

The novel concept of district heating system with decentralized heat storage units, different supply temperatures and two pairs of parallel twin-pipes was recently proposed and investigated thermodynamically. In this work, the use of triple-pipes for the distribution and service segments of the pipeline of this district heating scheme (where the transmission segment remains with twin-pipe type) is proposed and investigated. For this, computational fluid dynamic methods together with Evolutionary Polynomial Regression/Multi-Objective Genetic Algorithm approach are used to drive reliable correlations for estimating the rate of heat losses from the twin- and triple-pipes. The validity of the numerical simulations and the developed correlations are examined with the available data in the literature. Then, the performance of the specific district heating system in its conventional form and the revised design (i.e. when employing twin- and triple-pipes) is investigated and compared. The results show that the use of triple-pipes for the district heating improves the overall energy efficiency of the system by offering a considerably lower rate of heat loss through the distribution and service pipes. In addition, this eliminates the need for the secondary pairs of distribution and service twin-pipes, decreasing the costs of the system.

Abstract The object of this paper is to develop and exergetically assess a multi-generation system comprised of a Molten Carbonate Fuel Cell (MCFC) coupled with Steam Methane Reforming (SMR), Methanol Synthesis Process (MSP) with distillation process, and combined heat and power cycle (CHP) including gas turbine, Rankine cycle (RC), Organic Rankine Cycle (ORC) and District Heating (DH) line. The combination of the MCFC, CHP and MSP can be considered as an innovative breakthrough in the field of energy systems, in light of the fact that the reforming compartment can mutually feed both MCFC and MSP, and the whole process can simultaneously produce electricity, pure methanol and hot water. The SMR at 800 kPa and 600 °C was applied to produce synthetic gas required by MCFC and MSP. The simulation was performed by Aspen Hysys, considering several operational conditions and the best was selected according to exergetic performance assessment. The structure produced 110,544 kW net electricity (34% MCFC, 33.4% gas turbine, 18.4% RC and 14.2% ORC), pure methanol (99.9%) at 271.7 kgmole/h, and hot water at 80 °C and 65398.7 kgmole/h. About 23% and 21% of the overall destructed exergy belonged to combustion chamber and MCFC, respectively. The overall exergy destruction, exergy efficiency and energy efficiency of the integrated system were obtained 116,353 kW, 58.4% and 83.7%, respectively. Finally, the performance of the proposed hybrid system was compared with similar studies and it was found that the hybrid MCFC-MSP-CHP system can outstandingly enhance the overall efficiency and reduce CO2 emissions.

In the current research, ferrofluid migration and exergy destroyed became the main goal. Demonstration of characteristics impact of permeability, buoyancy and Hartmann numbers on variation of nanomaterial movement as well as irreversibility was examined. CVFEM with triangular element is utilized to calculate the solution of formulated equations. An increment in magnetic field results in greater exergy drop which is not beneficial in view of convective mode. An increase in permeability demonstrates a growth of nanomaterial convective flow. Augmenting Da causes a reduction in Bejan number while it makes Nuave to augment.

There is no doubt that the determination of a smart charging-discharging pattern can be very effective in increasing the cost-effectiveness and overall energy efficiency of an energy storage system. For finding the optimal operation strategy of the energy storage unit of a renewable power plant, the electricity spot price, the forecast data of energy availability, and the regulations of the local power market should all be taken into account. In addition to these economic considerations, the effect of deviation from the nominal load (partial-load operation) on the performance of the energy storage system is a critical parameter that directly affects the optimal operation pattern of the system in real-life energy markets. In this study, the effects of partial-load work of a low-temperature compressed air energy storage system on its overall performance are investigated thermodynamically employing real performance maps of all the components of the system. The results of the study indicate that the energy storage system needs to operate around nominal design conditions if it is expected to perform efficiently. The round-trip efficiency of the unit approaches 68% at a nominal load while it offers the low efficiencies of 52% and 28% if working at 50% and 10% loads, respectively.

Abstract A novel alternative cooling system for photovoltaic (PV) panels that includes passing pre-cooled ambient air over back panel surface is experimentally investigated for local conditions of Port Said, Egypt. This is an alternative cooling system in the sense that an earth-to-air heat exchanger (EAHE) is employed to firstly pre-cool the ambient air which is then implemented to cool the back surface of the PV panel to simultaneously improve the PV panel performance. It was possible to decrease the PV module temperature from an average 55 °C (without cooling) to 42 °C with the help of geothermal pre-cooled air flow over the back surface of a PV module at an optimum rate of 0.0288 m3/s. At this optimum flow rate, due to the decrease in PV module temperature, an average improvement in the PV module output power and electrical efficiency of about 18.90% and 22.98% respectively was achieved. According to economics assessment, the relative levelized cost of energy is improved by 12% due to proposed cooling system which is helped in avoiding emissions of about 13896 g CO2 per summer season.

Abstract The existence of health clinics is an essential need for residents of a remote area to improve their quality of life. Providing energy and freshwater for these units are critical problems especially in countries with arid areas and tropical climate. In this study, a hybrid energy system including photovoltaic panels, diesel generator, and battery bank is considered to provide electrical demand for a health clinic. Lack of proper access to the fuel in standalone systems can be a challenge in desert remote areas which could cause difficulties in the electricity management. Accordingly, three excess electricity management methods including increasing the annual fuel availability, using a combination of fuel cell/electrolyzer and considering the annual capacity shortage are compared to each other. Also for the first time, the possibility of annual shocks to the load is taken into account due to the global outbreak of some epidemic diseases such as SARS and Covid-19 in recent history. The results showed that the energy cost of proposed hybrid system would be 0.105 $/kWh with more than 30% renewable fraction. Also, the grid breakeven distance in different situations is estimated between 1.2 km and 5.8 km which shows the high capability of off-grid development of the proposed hybrid system for small loads.

AbstractIn recent days, the scientific community has been forced to develop renewable fuels due to the demand and increasing cost of conventional fuels. Among the different renewable fuels, biodiesel is a primary renewable fuel produced by the efficient and straightforward process (i.e., catalytic transesterification) with the homogeneous or heterogeneous catalysts. The heterogeneous catalysts are of greater interest in industrial biodiesel production, offering high activity, easy separation, low cost of production, and high reusability. Various studies have shown that the heterogeneous catalysts of calcium and potassium oxides offer a faster reaction rate. In this context, this study provides an overview of calcium and potassium oxide catalysts derived from waste resources. This study also presents the biomass catalytic preparation method and the optimal process conditions under which high biodiesel yield can be achieved. On the whole, the core objective of this study is to find the feasibility of biomass‐derived catalyst in the commercial sector and to determine its suitability for sustainable industrial application.