Another relevant metric is energy return on energy invested (EROI).This is not quoted for particular projects, but is the subject of more general studies. Using detailed atmospheric data to account for potential output, I study whether generation and installation experience leads to increased productivity for solar and wind projects.
A fuller account of EROI in electricity generation is in the information paper on Energy Return on Investment.
The (WEO2016) makes the points that VRE have five technical properties that make them distinct from more traditional forms of power generation.
Using panel data on program characteristics, electricity prices, generation, and employment, we find that portfolio standards have been successful at increasing regional renewable generation, with marginal compliance coming almost entirely from wind energy.
However, costs to consumers are large, with retail electricity rates increasing by 9-15% five years after adoption.
However, the variability of wind and solar power does not correspond with most demand, and as substantial capacity has been built in several countries in response to government incentives, occasional massive output from these sources creates major problems in maintaining the reliability and economic viability of the whole system.
There is a new focus on system costs related to achieving reliable supply to meet demand.
As electricity demand escalated, with supply depending largely on fossil fuels plus some hydro power and then nuclear energy, concerns arose about carbon dioxide emissions contributing to possible global warming.
Attention again turned to the huge sources of energy surging around us in nature – sun, wind, and seas in particular.
But attention swung away from renewable sources as the industrial revolution progressed on the basis of the concentrated energy locked up in fossil fuels.
This was compounded by the increasing use of reticulated electricity based on fossil fuels and the importance of portable high-density energy sources for transport – the era of oil.