Downhole heat exchangers are comparatively low cost methods of exploiting a geothermal resource. In addition, they have certain advantages claiming a higher level of geothermal energy than other methods of utilization. Environmental impact, for example, is usually very low when using downhole heat exchangers, as fluid is not normally removed from the reservoir. Downhole heat exchangers (DHE) allow very efficient use of the heat resource and often provide very low running cost (fuel cost) to the end user. However, the number of installations worldwide is relatively low because only under certain combinations of circumstances can DHE be considered as a suitable method. It is at the lower end of the temperature range where the DHEs advantages are most easily realized. Moreover, it is important to recognize that in Croatia there are many more low temperature resources than high temperatures ones.
