Are Geothermal Energy Returns On Investment High Enough?

Abstract

Energy Return On Investment (EROI) is an important figure of merit for assessing the viability of energy alternatives. If an energy technology has a low EROI, difficulties in defining the system boundaries and differences in quality of energy inputs and outputs become significant. There needs to be compelling reasons for pursuing a technology with a low EROI. But what is a low EROI? An EROI of one is not adequate. To be useful to society, energy systems must generate more than just the energy required to be self-sustaining, they must support the balance of society. Published work on what is the “minimum” EROI energy systems should have is discussed. One way of minimizing confusion regarding system boundaries and quality of energy on EROI is to close the loop that is use the system output energy as the investment energy for the next generation system. In the case of geothermal energy that means using electricity from one geothermal system to develop the next geothermal production system. The impact on geothermal EROI of closing the loop is examined. The benefit of using geothermal energy, as compared to fossil fuel, is examined for heating, electric power, and transportation based on past EROI analyses. This is done by comparing the merits of investing a barrel of fossil fuel directly in satisfying heating, electric power, and transportation demands vs. investing the barrel of fossil fuel in geothermal development and then using the geothermal energy for heating, electricity, and transportation.