You might think we’d know whether a solar PV system produced energy before we installed 1,000 Megawatts of it. But it’s hard to even know after the fact. Dr John Constable points us at an interesting new paper that discusses the odd creature called EROEI. This stands for energy return on energy invested. If you get back less than “one”, it sucks.
That sounds like a fine idea except everyone seems to get different answers to the same question. Solar PV in Switzerland achieves either a tenfold return or it costs a fifth of your energy. Plan your national policy with a Ouija Board?
Constable comes to the conclusion that the whole calculation is so uncertain it’s useless. There are so many subjective estimates on the “energy invested side” that the answer is almost irrelevant. Constable points out that what we really need to know is how the whole system responds to the addition of a new generator –but the whole grid analysis is even harder than just the EROEI to calculate.
His conclusion, it that we really need something more like a neural net to calculate the costs. Luckily we have one — us — and the contractual free market. It’s just the government keeps getting in the way of it working.
ENERGY RETURN AND ECONOMIC PLANNING
Date: 22/02/17 Dr John Constable: GWPF Energy Editor
In 2016 Ferruccio Ferroni and Robert J. Hopkirk published a striking article (“Energy Return on Energy Invested (ERoEI) for photovoltaic solar systems in regions of moderate insolation”, Energy Policy 94 (2016), 336–344) claiming that the energy return for Solar PV sites in Switzerland might be as low as 0.8, implying that the technology was not a net energy producer but a consumer. Unsurprisingly, this paper has been the subject of intense criticism, and a detailed and in many points persuasive rebuttal has recently been published by Marco Raugei et al. (“Energy Return on Energy Invested (ERoEI) for photovoltaic solar systems in regions of moderate insolation: A comprehensive response” Energy Policy 102 (2017), 377–384). Raugei and his colleagues make a number of methodological criticisms of Ferroni and Hopkirk and using alternative methods, calculate that the energy return is in the region of 7 to 10. While Raugei et al’s figure is positive it is not particularly high, as compared for example to figures in the literature for electricity from coal and gas (EROEI = 28–30), and nuclear (EROEI = 75–105) (see D. Weissbach et al. “Energy intensities, EROIs (energy returned on invested), and energy payback times of electricity generating power”, Energy 52 (2013), 210–221).
If you think the Swiss were crazy, ponder the Germans. If I read this chart correctly, they’ve installed 40,000MW.