Energy Ratio analysis and accounting for renewable and non-renewable electricity generation: A review.

Abstract This review collates energy assessment data for the most common electricity generation methods and evaluates five Energy Ratios. The considered ratios are Energy Return on Investment (EROI) – standard and external, Energy Payback Time (EPT), Primary Energy Factor (PEF), and Resource Utilisation Factor (RUF). A common energy analysis framework, together with three energy accounting methods based on energy value, exergy, and primary energy, are described. The concept of the time-value for energy as an analogy to the time-value for money is proposed and has a significant impact on the calculated Energy Ratios. In total, this review brings together data for 45 electricity generation projects. Based on the Energy Return on Investment (external), the generation methods fall into three tiers: (1) nuclear, natural gas combined cycle, and geothermal (in New Zealand) with ratios > 30, (2) hydro, wind, and geothermal (in Iceland) with ratios between 5–30, and (3) solar PV with ratios less than 5. High Energy Return on Investment ratios correspond to short Energy Payback Times and vice versa. Energy Ratio performance levels for renewable energy generation sources – hydro, wind, geothermal and solar – heavily rely on the quality of the primary natural resource available. This review recommends Energy Return on Investment (external) and Resource Utilisation Factor as the most useful metrics for inclusion in full sustainability assessment. Highlights • Determines five Energy Ratios for 45 electricity generation projects. • Introduces the concept of time-value for energy for capital energy investments. • Nuclear, natural gas and geothermal power stations achieve high Energy Ratios. • Geothermal, hydro, wind performances strongly depend on available resources. • Solar PV has the least attractive Energy Ratios due to high embedded energy. [ABSTRACT FROM AUTHOR]