In many developing countries the exponentially growing electricity demand can be covered by using locally available, sustainable low-enthalpy geothermal resources (80-150 °C). Such low-enthalpy sources can make electricity generation more independent from oil imports or from the over-dependence on hydropower. Until now this huge energy resource has only been used by some developed countries like the USA, Iceland and New Zealand. The reason why low-enthalpy geothermal resources are not used for electricity generation is that there is still a misconception that low-enthalpy thermal fluids are fit only for direct application. The advancement of drilling technology, development of efficient heat exchangers and deployment of high sensitive binary fluids contribute to the useful application of this energy resource on a much wider scale. This book focuses on all aspects of low enthalpy geothermal thermal fluids. It will be an important source book for all scientists working on geothermal energy development. Specifically those involved in research in developing countries rich in such thermal resources, and for agencies involved in bilateral and international cooperation.