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Most energy conversion systems, and especially electricity generation plants, do not operate at nominal conditions throughout their useful life: periodic, semi-periodic and stochastic changes in the availability of the resource affect solar (thermal and PV), wind, hydraulic, and geothermal plants, which in reality operate at off-design conditions for most of their life. To a smaller extent, fossil-fuelled plants may also be plagued by fuel availability problems and no longer easily predictable demand oscillation. In spite of the ever growing net connectivity, since the demand curve in even larger geographic regions displays a typical quasi-sinusoidal shape, fleet load modulation is unavoidable. Naturally, off-design operation and load cycling affect the cost of the generated kWh. This paper presents a general thermoeconomic method to evaluate the economic and environmental effects of energy system integration, taking into account life cycle concerns (supply chains) and the effect of inefficiencies due to off-design operation of the systems. The method here is applied to a realistic case study of an Italian regional utility: an analysis of the implications of the variation of the productive mix between a photovoltaic power plant (PV) and a standard commercial, non-cogenerating gas turbine plant (GT) on the final cost of the electrical kWh. The demand curve is prescribed, and the effect of different mixes is assessed, both on the monetary and on the exergy cost of the electricity. The economic cost assessment is performed by standard thermoeconomic techniques, whereas the exergy costs are evaluated using both the Extended Exergy Accounting (EEA) and the Thermo-Ecological Cost (TEC) methods. The results show that a purely monetary cash flow accounting and thermo-economics lead to contrasting results, and also that the EEA and TEC cost indicators generate different rankings among the studied alternative GT/PV mixes. [ABSTRACT FROM AUTHOR]

Abstract In this article, the economic and environmental implications due to the projected evolution of the power sector in Egypt until 2040 are assessed and discussed. The Reference Energy System (RES) of the Egyptian power sector has been defined and implemented in the Open Source Energy Modelling System (OSeMOSYS), based on two different energy scenarios. To increase the accuracy of the analysis, the discount rate on capital investments for the energy technologies has been imposed as a time dependent exogenous variable. Moreover, the robustness of the obtained results has been tested through a sensitivity analysis on the main exogenous parameters. It is found that Combined Cycles, Wind, and Photovoltaic rooftop systems are compatible technologies to be included in the future Egypt's power generation mix. In particular, based on the abundant Egypt's renewables resources endowments, wind power technology comes first in achieving the proposed target on renewables penetration in the country's generation mix, and it might be a feasible alternative to replace a part of the natural gas share. Moreover, the significant impact of discount rate on capitals on the final results is highlighted: low values of discount rate would skew generation mix to include higher investment cost technologies and vice versa. Highlights • Implications of future energy scenarios in Egypt have analyzed based on OSeMOSYS. • Sensitivity analysis has performed on relevant techno-economic scenario parameters. • Combined cycles, wind and PV are key technologies in future Egypt's power mix. • Efficiency of combined cycles is relevant in reducing power cost and emissions. • Wind technology may replace a part of natural gas share in the electricity mix. [ABSTRACT FROM AUTHOR]