Germany’s gamble on P2G: Expensive electricity to expensive methane to expensive storage


There isn’t much good news about Germany’s failing Energiewende. Because they have boxed themselves into a corner by eliminating their nuclear portfolio, they are facing the physical realities of trying to deploy unreliable wind and solar far beyond their appropriate penetration levels. According to the research by Lion Hirth (Vattenfall Europe AG) appropriate penetration would be 7% wind for today’s Germany, perhaps as much 25% in a future Germany optimized for VRE [PDF]. Germany is abusing neighboring grids by dumping excess generation while exploiting the neighboring grids to supply power when the sun doesn’t shine and the wind doesn’t blow.

To push VRE to meet their 80% commitment Germany obviously needs abundant cheap storage. Unfortunately they don’t have the enviable volume of hydro that Sweden and Norway have. So, as  Quirin Schiermeier writes in Nature Renewable power: Germany’s energy gamble, Germany is making a big bet on P2G:

P2G, however, could provide a vast amount of new storage capacity and Germany is leading the way. The plant in Stuttgart has 250 kilowatts of electrolysis stacks, which use electricity from renewables to produce hydrogen from water. To make methane, the hydrogen is reacted with CO2 from decomposing sewage and agricultural waste at a nearby biogas plant. Other P2G plants could scrub CO2 from the air.

But P2G is still an immature technology, with high upfront costs and an efficiency of only about 50% in converting electricity to methane. Synthetic methane plants have also struggled with the purity of their product. At the ZSW facility, the main goal is to routinely produce gas with low oxygen and hydrogen content.

For transport fuels, the P2G concept might make some economic sense IF powered by nuclear electricity. But Germany is trying to use this process to fix the serious grid instability problems they have created for themselves. Adding the high cost of variable renewable electricity to the high cost of the P2G conversion – this is good for the economy? How prudent is it to base an industrial economy on advanced proton-exchange membranes for electrolysis?