This paper describes the concept of energy return on energy invested (EROI), and sets out some of the various approaches to calculating EROI ratios that exist, particularly in terms of boundary conditions. The paper presents a range of current estimates of EROI ratios for conventional oil and gas, and shows that these have generally fallen in recent years. EROI values for non-conventional oil and gas, and for a range of other energy sources, are also presented. These show that with the exception of coal and hydroelectricity, most of these other energy sources have lower EROI ratios than conventional oil and gas, and more so if energy storage is needed to compensate for intermittency of supply. The reasons that EROI data should be incorporated into energy forecasts, and the implication in terms of the EROI required to support modern society, are then briefly explored.
Hall, C.A.S. EROI Ratios of Energy Sources as Inputs to Energy Forecasting: Implications for Long-Term Prosperity The Oil Age 2 (1) 29-56
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