| Abstract |
From 1985 to 2013, geothermal power grew in Italy at an average rate of 2.4% per year thanks to the exploitation of high-temperature hydrothermal systems within 5 km depth by using conventional technologies, mostly condensing power plants supplied by steam or water-dominated reservoirs. However, these types of systems with T more than 100 °C within 5 km of depth are found in only a few areas of the country which aggregately extends over 1,500 km2. Thus, an objective limit exists to increasing Italian geothermal generation by harnessing hydrothermal systems only. A study published by Unione Geotermica Italiana (UGI – Italian Geothermal Union) in December 2011 concluded that by limiting development to such systems, geothermal electricity in Italy would attain in 2030 no more than 1,500 MWe and 9 TWh/yr; however, should the technology of unconventional geothermal systems (UGS) become commercially mature for power production by 2025, the figures above might increase in 2030 to a maximum of 2,000 MWe and 12 TWh/yr. In such case, the UGS would give a contribution to total Italian geothermal generation in 2030 of more than 25 %. A more recent study made by UGI on the possible growth of geothermal power in Italy by 2050 pointed out that by only harnessing hydrothermal systems in the above-said 1,500 km2 of high-temperature areas, with no contribution from UGS, the moderate increase envisaged for the future would vanish around 2030 and a gradual decrease would then begin, resulting in ~1,200 MWe installed capacity and ~7.5 TWh/yr produced by 2050. On the contrary, should UGS become technically mature around 2025 and their commercial exploitation start for power production, they would counterbalance abundantly the decreased production from hydrothermal systems, and the combined generation from hydrothermal systems plus UGS would reach in 2050 some 3000 MWe and 18 TWh/yr. Out of these totals, ~1800 MWe and ~10.5 TWh/yr would belong to UGS alone. It is thus patent that the long-term increase of geothermal power in Italy largely depends on the technical-economic feasibility to exploit geothermal systems other than traditional hydrothermal systems. After describing shortly the geological characteristics of the UGS, where they are found in Italy, and the estimated overall extension on land and offshore of their first order priority areas (4,000-10,000 km2), an estimation is given of the aggregate potential for power generation from UGS in such areas: 200-500 GWye. For plants operated at full load for 50 years and 6000 hours/yr, this range of values corresponds to 4000-10,000 MWe of installed capacity and 25-60 TWh/yr of power generation. Finally, a proposal by UGI is outlined for the execution of a large-scale R&D Project targeted at UGS as a whole. The general program of such Project would include drilling of 10-20 wells at 4-5 km depth, located in geologically different sites, and the installation of 3-5 pilot plants. The duration and cost of the Project are estimated to be 9-10 years and 200-400 M€, respectively. Only this type of Project, we think, may create the technical pre-requisites necessary in Italy to start harnessing the sizeable energy potential of unconventional geothermal systems. In this way only, we feel, the country’s geothermal power development can be directed towards a stable rising trend, with the figures given above for 2050 representing a step only of much more important long-term targets. |