school energy&environment

A “cascade” of applications

After being used for electricity production and domestic heating, geothermal fluids still have a certain quantity of heat that allows their usage in a variety of ways, some of which very peculiar: in Sapporo (Japan) and Klamath Falls (USA), for example, hot waters are used for heating the roads during the winter to avoid the formation of ice. Various productive processes benefit from the use of geothermal waters. For example, special absorption systems for refrigeration with ammonia or lithium bromide used for cooling and summer air-conditioning are obtained from hot waters, if the temperatures are between 80-120 °C. Among the productive uses, agriculture and zootechnics are the sectors where the use of geothermal energy is more immediate and advantageous. The hot waters are used for direct heating in greenhouses: very well-known examples are the Piancastagnaio greenhouses (M. Amiata, Toscana), or the Colli Euganei (Veneto) cultivations of ornamental plants. In countries where the climate is particularly cold, such as, for example, Siberia, the hot waters are made to circulate in a system of pipes that are in contact with the ground, the so called “hot beds”, obtaining the heating of the cultivated ground, which allows cultivation even under conditions that would otherwise be prohibitive for agriculture. The warmth that is produced by contact with hot waters is exploited for all zootechnic and agricultural processes that require a warm environment, such as, for example, mushroom cultures, fish and animal breeding and egg-hatching in poultry farms. Other uses in the agro-alimentary sector regard wood and fish dehydration, the preparation of tinned food, the production and seasoning of dairy products or sugar refining, while more industrial uses regard the production of heavy water, aluminium, cement production processes, tire vulcanization and many others. The waters that circulate deep underground are often rich in salts and minerals: these can represent a problems, in terms of pollution, but they can also become an important resource, as for instance for the extraction of suplhur, boron and metals. We must not forget the therapeutic uses. The habit to go to thermal baths was spread in Europe by the Romans, who exported it in all the territories they conquered, but it has been present in Asia for centuries: only in Japan there are more than 1600 thermal centres, some of which have very ancient origins. In Italy thermal complexes are about 170 and they are exploited not only for the heat of the waters, but also for the therapeutic effects of the minerals present in them. The benefic effects of a thermal bath are wll known also by the macaque population of the Nagano springs, in Japan, who bathe there during the winter months to keep warm: the funny images of the little animals happily lying in the warm water, with the coat covered in snow and red snouts, have gone all around the world and now the Nagano macaques have become a famous tourist attraction, so much so that, in typical oriental fashion, an area of the thermal baths has been reserved for them only!