Living in the US, one could be forgiven for believing that continued development of global fossil fuel resources and infrastructure must come at the expense of alternative energies, and vice versa. Political rhetoric increasingly casts the two as foes in a zero-sum game.
Other parts of the world, however, are approaching the need to develop both conventional and alternative sources of energy more pragmatically. European efforts to store solar and wind-generated electricity as "green gas" stand as one example.
A number of speakers at the Euro Institute for Information and Technology Transfer's Pipeline Technology Conference, held last month in Hannover, Germany, addressed the possibility of using the existing natural gas storage and transportation network as a means of providing this storage.
Germany currently produces more wind energy in the north than it can transmit to consuming centers in the south. This imbalance will likely grow through 2020 as southern nuclear plants are retired and wind development continues in the north.
Much of the excess energy can be stored, but only for a short time. Using electrolysis to produce hydrogen from the electricity and adding it to the existing natural gas stream is one storage solution. But still-not-thoroughly-defined limits on how much hydrogen can efficiently be transferred as part of the gas stream without degrading the infrastructure restrict this path.
Methanizing the hydrogen, however, by combining it with carbon dioxide, removes such efficiency and integrity concerns and offers an energy storage medium that would be completely compatible with existing infrastructure.
Private-public partnership
Private industry is leading the technological way in Europe, with funding from the German federal government. Solar Fuel Technology GMBH & Co. KG announced late in 2011 that it would build a pilot e-gas facility for German automaker Audi by 2013.
The pilot plant will use about 6 Mw of wind-generated power to produce 1.4 million cu m/year of e-gas. The efficiency ratio of the e-gas pilot plant—from wind turbine to methane gas—is about 54%, according to Audi, which intends to raise this level above 60%.
Audi will bring its A3 TCNG auto to market in 2013. The company touts the turbocharged compressed natural gas vehicle, which can also burn conventional gasoline, as capable of covering more than 745 miles on a combination of the two fuels and nearly 250 on natural gas alone. The gas is stored at 200 bar in two steel cylinders below the luggage compartment.
Between wind generation of the electricity, using CO2 in methanization, and the lower emissions involved in burning natural gas as opposed to gasoline, Audi has declared the project's goal as nothing short of CO2-neutral mobility.
Though the Solar Fuel-Audi project is self-contained, Germany's midstream companies have also taken interest in the potential of "green gas" as a storage medium. Officials from E.ON-subsidiary Open Grid Europe, natural gas and environmental technology firm DBI GUT GMBH, and electricity and natural gas company EnBW Energie Baden-Wurttemberg AG all enthusiastically detailed not just the ability, but the need for Europe's natural gas and electricity networks to work together as one.
Audi describes Germany's natural gas network as capable of holding 217 TWh of electricity, as compared with the power grid's 0.04 TWh. This energy can be transferred back to the power grid through combustion at any time. The e-gas could also be burned directly at private homes and businesses to generate heat.
The path towards both CO2-neutral mobility and the broader storage of renewable electricity as natural gas uses existing, fully developed technology. The methods can be replicated anywhere with an existing natural gas transportation infrastructure.
Europe's efforts to tangibly pursue these goals also underscore the potential of what can be achieved when public and private entities, and conventional and alternative energy interests, work together.
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