Energy

New frontiers

Technological development and the need to retrieve energy from the highest possible number of sources are contributing to the rediscovery of geothermal energy and an increase of its areas of utilisation: of the “clean and cheap” energy provided by our planet, nothing is wasted! Using systems of heat pumps, which extract heat from a fluid using small quantities of electricity, heat that is then yielded to a heat tank, waters with very low temperatures can be used for domestic heating, up to 30-40° C. The same waters can be used directly with panel heating systems instead of heaters. Currently there are studies concentrating on the exploitation of the so called hot dry rock fields. At high depths (around 5,000 m), even under normal heat flux conditions, the majority of the rocks is sufficiently hot to be able to fuel a geothermal system. If the warmth from the Earth is always available, sometimes though the other fundamental “ingredient” for the use of geothermal resources is missing: underground water circulation. In this case, nature has to be “helped” to create a tank that will aide the formation of a geothermal system: cold waters are artificially pumped into deep wells, after having seen to the fracturation of the surrounding rocks to allow the water to penetrate, in order to recreate an aquifer system similar to a natural geothermal field, from which it is possible to draw heated waters. Currently they still are experimental and expensive systems, but the first attempts appear encouraging and in a few years energy production from dry rock fields could become a reality. These systems, however, are very “invasive” and their long-term effects are still not predictable: since one of the most probable side effects is to trigger subsidence phenomena on the surface, the experiments are currently undertaken in desertic or scarcely populated areas, like in the New Mexico desert. In some areas of the Earth, such as the Mexico Gulf, geothermal systems have been discovered at a depth of 4,000 m, where hot waters are mixed with methane at very high pressures: in this case, the exploitation would yield geothermal energy as well as significant quantities of hydrocarbons. The Hawaii islands, thanks to the heat of the various active volcanoes, also constitute a formidable experimental ground. For example, there is an ongoing experiment for the production of hydrogen from very hot waters that are heated by volcanic magma, the temperatures of which are around 900-1,200° C. What however represents the ultimate frontier in this field of research is the possibility to put organic waste in contact with hot magma to produce gaseous hydrocarbons. Will man really be able to reproduce Nature’s processes to create energy?