# Evaluation of the Coupling of a Hybrid Power Plant with a Water Generation System
## 1 Introduction  
Global economic progress, population increase, and the technological development of emerging countries lead to a constant growth in demand of water and energy [1]. It is undeniably true that water is a vital resource, fundamental to life and health. Access to water and sanitation requires the consumption of energy. The generation of energy, on the other hand, requires large amounts of water. In this way, water and energy are closely interrelated [2]. The future of global sustainability depends on the achievement of an optimized use of both resources that will provide a viable solution for future generations. In recent years, the use of Renewable Energy Sources (RES) within the energy sector has been increasing, currently accounting for 13.7% of the global energy supply. At present, however, about 80% of all primary energy in the world is still derived from fossil fuels, namely 31.7% from oil, 28.1% from coal and 21.6% from natural gas [3]. Although great amounts of energy can be obtained from fossil fuels, their use has a high environmental impact. Continuous release of pollutants to the atmosphereleads to considerable environmental and health problems [4]. In addition, climate change linked to fossil fuel combustion presents an important long-term impact on the availability and quality of water worldwide [5]. Today, Hybrid Power Plants (HPP) play an important role in the future of sustainable energy generation. HPPs combine two or more energy resources, make use of existing infrastructure and aggregate new components to combine the advantages of the combined resources. They can thus lead to secure and continuous energy production, savings in combustibles and reduction of harmful emissions. It is common that at least one of the energy sources is renewable, though the priority is to choose the most efficient and reliable mix of energy technologies to satisfy the users' needs. The combination of conventional thermal power plants with RES helps to transition away from fossil fuel use [6]. RES provide an alternative to fossil fuels and can help to mitigate greenhouse gas emissions and global warming [7]. Solar energy can be captured by means of two fundamental methods, photoreaction and heat, that can be combined in several ways to produce heat and electricity. Within these processes, Concentrating Solar Power (CSP) allows the collection of solar energy at relatively high working temperatures, resulting in better conversion efficiencies of heat into electricity [8]. CSP systems are based on the concentration of direct solar irradiance onto a specific area through mirrors or lenses that is then used to heat up the working fluid of the process. The harnessed energy by the working fluid is then directly or indirectly used to drive a steam turbine coupled to an electric generator [9]. Technologies used include parabolic troughs, Fresnel reflectors, parabolic dishes and solar towers [10]. Three major solar power plants can be found in the surrounding areas of Seville: PS10 and PS20, with water as working fluid, and Gemasolar with molten salts technology and 15 hours of storage facilities. PS10 is a plant with 11 MW of installed capacity and it consists of a solar field with 624 heliostats and a receiver tower of a height of 115 meters. PS20 and Gemasolar have an installed capacity of 20 MW and 19.9 MW, respectively [11]. There have been several studies on the coupling of CSPs with other conventional fuels or renewable energies in recent years in literature. A review of hybrid plant configurations involving CSP and fossil fuel was realized in 2012 by [PERSON] et al [12]. In that paper, solar-fossil fuel hybrids are classified by the authors into three general categories: combined cycles, solarized gas turbines and solar reforming. Examples of these categories include the Gemasolar solar plant in Spain [10] and the SEGS II-IX in California, both using natural gas backup for evaporation and superheating [13]. The integration of CSP with geothermal energy is another promising hybridization alternative.