Geothermal energy, small hydropower, and bioenergy

This chapter is focusing on geothermal energy, small hydro-power systems, and a very brief description of biomass suitable for power generation or in industrial processes, building, and other large commercial and applications. Geothermal energy sources are providing thermal energy to the industrial processes, buildings and eventually used to generate electricity, having a significant potential to contribute substantially to the world energy demands. Water energy originates from sources, such as the oceans, seas, rivers, and waterfalls. From water systems, the mechanical energy can be harvested either in kinetic or potential energy from waterfalls, rivers, currents, tides, or waves that eventually is used for power generation. The thermal energy from the temperature differences between ocean's warm and cold deeper layers can also be used for electricity generation having a huge potential and availability. However, ocean thermal energy is not discussed in this chapter, being beyond the scope of this book. Hydropower, the most and the largest renewable energy source for electricity generation, is derived from the energy of moving water from higher to lower elevations or from water kinetic energy. Hydropower systems require relatively high initial investment, but have the advantage of very low operation and maintenance costs and a long lifespan. Hydropower technology is the most advanced and mature renewable energy technology and provides an important portion of the electricity generation in many countries. Small- and mini-hydropower systems mean, the systems that can be applied to the sites ranging from a tiny scheme to electrify a single home, to a few hundred kilowatts or even few megawatts for selling it to the grid. Small-scale hydropower is one of the most cost-effective and reliable energy technologies to be considered for providing clean electricity. Hydroelectric power plants use minimal resources to generate electricity, nor do they pollute the air, land, or water, as other types of power plants may. A reference to the resource estimates and analysis are also included here. Characteristics, advantages, and disadvantages of these renewable energy sources, their operation and characteristics, as well as their major applications are presented in this chapter and discussed in details.