# Evaluation of the Coupling of a Hybrid Power Plant with a Water Generation System
## 5 Conclusions  
The management of water and energy resources will face new challenges in the future due to increasing demand, the depletion of traditional energy sources and their environmental consequences, and increasing water scarcity. Within this context of great pressure on vital resources, climate change adds an additional level of complexity. The introduction of renewable solutions is thus essential for the achievement of short and mid-term sustainable objectives.  
This work presented the simulation and analysis of a 20 MW hybrid solar/biomass power plant combined with an advanced wastewater facility for a region in the province of Seville, Spain. The plant used molten salts as the working fluid and included two thermal storage tanks of a total capacity of 600 MWh for operational autonomy of up to 4 hours. The biomass combustor was used as an auxiliary system, in the event of limited solar radiation or inadequate thermal energy in the storage tanks. The water treatment plant consisted of a direct potable reuse system with the objective of treating urban sewage and producing clean water for the selected region. The specific treatment train consisted of physical, biological and chemical procedures including membrane bioreactors, ozonization, biological and granular activated carbon, reverse osmosis, ultraviolet radiation and chlorination.  
We found that the biomass combustor had the highest exergy destruction among all plant components due to the chemical reaction taking place there. Some heat exchangers, such as the feedwater preheaters, also display relatively low exergetic efficiencies due to the mixing of streams with great temperature differences. The full-load global exergetic efficiency of the power plant is found to be 15% when the solar part is used and 34% when the biomass support system is required. The net capital investment required for the construction and implementation of the plant was found to be 211,526,000 \(\epsilon\). This cost included both the hybrid power plant with thermal storage and the required advanced treatment technologies used to supply the region with potable water. The levelized cost of electricity of the combined plant was found to be 0.25 \(\epsilon\)/kWh, a value somewhat higher than existing solar tower power plants. Lastly, a sensitivity analysis of the water reclamation plant was conducted in order to evaluate the feasibility and viability of the project. The required selling price of the generated potable water was found to be 14.61 \(\epsilon\)/m\({}^{3}\). Accounting for present conditions, this cost is considered relatively high. However, foreseen future water limitations are expected to drive water prices up, especially in arid regions with intense lack of water resources. In essence, the combination of renewable energy plants with water generation processes will provide a valuable and profitable alternative for local communities to create environmentally safe facilities with continuous and stable power supply and the additional sustainable management of fresh water resources.  
Conceptualization, F.P.; investigation, A.d.M.; writing, A.d.M. and F.P.  
Fontain Petrakopoulou is funded by the Ramon y Cajal Programme of the Spanish Ministry of Science, Innovation and Universities (Grant no. RYC-2016-20971).  
The authors