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Germany has set the bold emissions target of reducing its greenhouse gas levels by 40% by 2020, and then 80% by 2050, compared to 1990 levels. Other countries have set similarly ambitious targets but Germany is the largest economy to aim to produce so much of their energy from renewable sources. They have led the world in solar installations, and now are concentrating on wind power as well. Germany will be a test case to show whether industrialised nations can still compete whilst relying on renewable energy.
Keeping energy costs low whilst moving towards a renewable energy based grid will be difficult. Solar is still much more expensive, and whilst wind is almost as cheap as fossil fuels, it is also intermittent; even a perfectly situated wind turbine only generates power about 33% of the time.
Germany is going to have to install huge amounts of energy storage systems to make up for the intermittency of renewables. Siemens estimates that generating 85 percent of Germany's electricity using renewables will require 30,000 gigawatt-hours of storage. The cheapest way to store energy is to use excess power to pump water up a hill, and then let it flow down through a turbine when the energy is needed again. It is should be easy to develop as well, all you really need is a hill … but Germany is mostly flat.
Siemens believe they have the solution; Electrolyser plants. In a plant the size of a large warehouse, electricity will be used to split water into hydrogen gas. The hydrogen can then be mixed with existing gas and piped to gas-fired power plants, or stored in containers. The salt caverns used to store Germany’s strategic oil reserves could also provide more storage options for hydrogen gas.
Siemens’s electrolysers are based on technology very similar to that of fuel cells found in cars. They differ from existing examples due to the fact that they are flexible enough to run on intermittent power, and cope with surges in power up to three times the normal level. Perfect for accommodating the varying power levels created by renewable energy.
Hydrogen production is an incredibly inefficient form of energy storage. In the process of creating the hydrogen, and then using the hydrogen to create electricity, about two thirds of the initial energy is lost. However Siemens also suggest that it is the only storage option available to Germany that offers the required scale.
By. Charles Kennedy of Oilprice.com
Charles is a writer for Oilprice.com