Renewable energies are the best solutions to reduce CO2 emissions and supply reliable electricity. This study aims to find the best combination of various components considering economic, environmental, and technical factors together. The most important consideration factors are the limitation of using PV panels due to the land constraints and applying CO2 penalties where diesel generators and the grid are generating electricity. Findings show that providing electricity by hybrid systems would be useful even in the well-provided electricity regions by the grid with the least blackouts. The best combination of the proposed components, including PV, bio generator, diesel generator, batteries, and grid for the case study region where the load demand is 890 kWh/day and peak load is 167.2 kW, would be an off-grid hybrid system including PV, bio generator, diesel generator, and battery. The optimization results show an NPC (present value of the costs of investment and operation of a system over its lifetime) of $1.02 million and a COE (the average cost per capital of useful electricity produced by the system) of 0.188 $/kWh. Finally, due to the showing of the effect of different conditions on the optimization results and making the study usable for other circumstances of the case study region, some sensitivity analyses have been carried out.

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Lithium heat pipe has broad applications in heat pipe cooled reactors and hypersonic vehicles due to its ultra-high working temperature which is around 1700 K. In this paper, a lithium heat pipe based experimental facility has been designed to test the heat transfer performance of the lithium heat pipe. A simplified mathematical model of heat pipe has been implemented into a CFD approach, which is used to verify the design of lithium heat pipe and its experimental facility. Results showed that the CFD approach is in good agreements with some well-known existing models and experimental data, and deviation between the results is within 5% range. The adjustment range of mixed gas thermal resistance and cooling water flow rate was obtained by analyzing the effects of different cooling conditions on the performance of the experimental facility. It is necessary to ensure the cooling water flow rate is above 0.11l/h to prevent water boiling when the heating power is10kW around, and the optimal proportion of helium is 70% -90%.The operation characteristics of the lithium heat pipe under unsteady state with varying heating power were simulated numerically. The results show that the proportion of helium must be less than 60% for normal operation of the lithium heat pipe. This work provides a reference and numerical verification for the design of lithium heat pipe based experimental facility, which can be used to reveal the heat transfer mechanisms of the lithium heat pipe during the experiment.

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