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F. Calise, et al. Energy Conversion and Management 220 (2020) 113043

Fig. 14. Proposed System 2 (PS2): Sensitivity analysis of the photovoltaic field area, A PV.
• the considerable advantages in terms of energy, environmental and freshwater costs. The results of the paper show that some arrangements
economic savings: the obtained primary energy saving, avoided CO 2 of renewable polygeneration systems are not currently profitable when
emissions, and simple payback period are equal to 64.4%, 63.9% compared with conventional fossil fuel systems. However, these sys-
and 6.2 years, respectively. This is mainly due to the use of a heat tems are very promising for isolated islands. In fact, for islands featured
pump, an established technology with high energy efficiency; by short offshore distance and stable load demand, the direct connec-
• with the adoption of electric storage systems, an improvement of the tion with mainland water and energy network is the most common
self-consumed electric energy could be attained, reducing the elec- option. However, in case of small islands which are furthest away from
tric energy withdrawn from the grid during night hours; the coastline, the interconnection schemes are significantly complex
• good performance is obtained in terms of freshwater demand: re- and hybrid energy systems based on local RESs represent the best so-
verse osmosis unit produces 68% of the freshwater demand; lution, for the production of both energy and water. Results are spe-
• the variation of the area of the photovoltaic field from 5000 m to cially promising for those islands where buildings are located in small
2
2
25,000 m suggests including a smaller photovoltaic field compared areas close to the coast, minimizing the cost of the district network. In
to the one studied, in order to increase the plant profitability. the framework of the solar desalination technique, the performed
thermoeconomic analysis model can help to guide the optimal plant
The piping networks of the district heating and cooling systems of location and the selection of design parameters, for the selected island.
the two cases studies need to cover areas of relatively low energy de- Finally, the study confirmed that, in the current energy market,
mand. This is a result of the relatively high number of secondary homes photovoltaic panels coupled with electric driven HPs are more profit-
or vacation houses and low occupation of a large number of buildings in able than concentrating photovoltaic and thermal collectors coupled
the communities, especially in the winter. Nevertheless, these networks with thermally-driven technologies.
promote the incorporation of renewable energy in communities cur-
rently strongly dependent on fossil fuels, which would reduce the en-
vironmental impact of local energy and water generation. Declaration of Competing Interest
Finally, the obtained results of this work, could be used as a re-
ference for the self-sufficiency and decarbonization of other small The authors declare that they have no known competing financial
Mediterranean islands, rich in renewable energy sources and seawater, interests or personal relationships that could have appeared to influ-
featured by limited sources of fossil fuels and freshwater, and high ence the work reported in this paper.

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