The utilization of geothermal energy has exhibited an interesting trend over the years. In the five years between 1975 and 1979 the geothermal electric capacity installed in the world increased from 75 to 462 MWe; by the end of the next five-year period (1984) this figure had reached 1495 MWe, showing a rate of increase during these two periods of 500% and 223%, respectively (Dickson and Fanelli, 1988). In the next sixteen years, from 1984 to 2000, there was a further increase of almost 150%.
Geothermal power plays a fairly significant role in the energy balance of some areas; for example, in 2001 the electric energy produced from geothermal resources represented 27% of the total electricity generated in the Philippines, 12.4% in Kenya, 11.4% in Costa Rica, and 4.3% in El Salvador.
As regards non-electric applications of geothermal energy, Table below gives the installed capacity (15,145 MWt) and energy use (190,699 TJ/yr) world-wide for the year 2000. During that year 58 countries reported direct uses, compared to 28 in 1995 and 24 in 1985. The number of countries with direct uses has very likely increased since then, as well as the total installed capacity and energy use.
The most common non-electric use world-wide (in terms of installed capacity) is heat pumps (34.80%), followed by bathing (26.20%), space-heating (21.62%), greenhouses (8.22%), aquaculture (3.93%), and industrial processes (3.13For Gas turbine based combined cycles using this concept have 2-3 % higher efficiency over multi-pressure combined cycle plants using steam/water as the working fluid. In low gas temperature heat recovery systems such as diesel engine exhaust or fired heater exhaust,the energy recovered from the hot gas stream is more significant and Kalina cycle output increases by 20-30 %.The main reason for the improvement is that the boiling of ammonia-water mixture occurs over a range of temperatures, unlike steam and hence the amount of energy recovered from the gas...