| Title | A thermoeconomic approach to the analysis of geothermal plants |
|---|---|
| Authors | Vaccaro, Franco |
| Year | 2013 |
| Conference | European Geothermal Conference |
| Keywords | Medium-low temperature resources, binary power plants, geothermal power plants design, Interdisciplinary approach, Thermoeconomics. |
| Abstract | Nowadays geothermal plants constitute a marginal part of the worldwide energy mix. In the electricity worldwide production only 11 GW on a total of about 5000 GW are geothermal plants. However a growing interest from industry and national institutions has been observed in the last ten years. The goals of sustainability and maximization of the resource durability can be pursued only through a multidisciplinary approach. Different backgrounds are involved in these studies (Energy Engineering, Reservoir Engineering, Geology and Geophysics). The quite high economic cost of geothermal energy is well known and it is due to the exploration costs, to the drilling and plant facilities, to the variation of the resource characteristics during time and to the difficulties in obtaining “economies of scale”. This last aspect is directly linked to the concept of renewability and sustainable use of the energy resources, that has been already discussed by the authors in recent papers (Franco and Vaccaro 2012). In the meantime the typical approach to the geothermal potential assessment has always been quite conservative from the point of view of technological optimization, so that a lot of installed plants have very low efficiencies. This is particularly true in the case of medium to low enthalpy reservoirs. Moreover the efficiency of small size power plants is strongly conditioned by the temperature of reservoir and environment. Reservoir temperature decline is also a complex function of the exploitation strategy adopted. Reservoir and power plant should be then considered as a global “geothermal system” together with the environment and with the energy/mass transfers between them. On the other hand the real advantage of geothermal energy is the null cost of the energy source. During the history of the development of geothermal industry this last aspect lead to the consideration of the geothermal energy utilization only under an economic perspective. But an exclusively economic approach is not always good. The resource durability cannot always be subordinated to the economic scale (mainly for medium-low temperature resources). In this particular context the authors propose a thermoeconomic approach for the analysis of geothermal power plants. Irreversibilities and hidden costs for the reservoir restoration should be taken into account for a complete perspective of this growing industry. Different case studies are considered and discussed. The results of a thermoeconomic analysis appear to be interesting particularly in case of small size plants. |