Renewable energy systems is an effective and a viable strategy that can be employed to harness renewable energy resources to energize remote rural areas of developing countries. A renewable energy system can be used to supply some or all of electricity needs, using technologies like: small solar electric systems, small wind electric systems, microhydropower systems, and small hybrid electric systems (solar and wind). Most renewable energy comes either directly or indirectly from the sun. Sunlight, or solar energy, can be used directly for heating and lighting homes and other buildings, for generating electricity, and for hot water heating, solar cooling, and a variety of commercial and industrial uses. The sun's heat also drives the winds, whose energy, is captured with wind turbines. Then, the winds and the sun's heat cause water to evaporate. When this water vapor turns into rain or snow and flows downhill into rivers or streams, its energy can be captured using hydroelectric power. Renewable energy brings about improvement in living environment and community welfare by supplying the basic needs such as biogas for cooking, water for domestic and irrigation purposes and electrical energy for lighting, communication, cold storage, educational and small- scale industrial purposes. Modeling and optimization of integrated renewable energy systems (IRES) for a selected study area makes IRES more advantageous when compared to hybrid concepts. The book Modeling and Optimization of Renewable Energy Systems should be of immense valuable for students, researchers, and people working on renewable energy systems. This book focuses on solar energy, wind energy, hybrid systems, biofuels, energy management and efficiency, optimization of renewable energy systems and much more. Consequently, the book presents the physical and technical principles of favorable ways of applying renewable energies.