Original URL: http://www.theregister.co.uk/2010/05/06/german_synthetic_natural_gas/

Germans plan to make 'synthetic natural' gas from CO2

Megawatt trial: Could be huge for renewables, nuclear

By Lewis Page

Posted in Science, 6th May 2010 12:49 GMT

Remorseless German and Austrian boffins have a cunning new plan which could be good news for cutting down on fossil fuel use: they can make "synthetic natural gas" using electric power, water and carbon dioxide.

"Our demonstration system in Stuttgart splits water using electrolysis. The result is hydrogen and oxygen," explains Dr Michael Specht of the Zentrum für Sonnenenergie- und Wasserstoff-Forschung (Solar energy and Waterstuff [Hydrogen] Research centre - ZSW).

"A chemical reaction of hydrogen with carbon dioxide [then] generates methane – and that is nothing other than natural gas, produced synthetically."

The process is thought to scale up well, with Specht and his colleagues planning to fire up a "double-digit megawatt range" unit by 2012.

The kit is intended to solve one of the great problems of renewable power supplies - wind, solar and tidal - which is that their electric output is variable and uncontrolled, bearing no relation to demand at the time. Storing electricity on a large scale can be done by pumping water uphill for later use in hydropower turbines, but this is expensive even where suitable geography exists.

Even with the present, fairly low fractions of wind and solar power seen on the linked grids of Germany and adjacent countries, sudden pulses of renewables output often result in negative electricity prices as renewables operators pay to get their power onto the grid (and so claim the subsidies which are the principal source of their revenues).

"Surplus wind and solar energy can be stored in this manner. During times of high wind speeds, wind turbines generate more power than is currently needed. This surplus energy is being more frequently reflected at the power exchange market through negative electricity prices," confirms Specht's colleague Dr Michael Sterner.

This is not a good situation for renewables, but scope for expansion of pumped storage at reasonable cost is limited in Germany. Hence the plan to store surplus electricity as gas, rather than by lifting water.

At the moment, pumped storage has better efficiency - 70 per cent or better of the electricity so stashed can be recovered, compared to the ZSW synthi-natural gas figure of "more than 60 per cent".

"In our opinion, this is definitely better than a total loss," says Specht, modestly.

The synthi-gas plan has other things going for it, however, which pumped storage doesn't offer. First off you can store a lot more power, as massive gas storage is already available within the gas grid - to the tune of 200 terawatt-hours in Germany, apparently. That's enough to cover months of present-day German gas demand, or alternatively to generate more than two months' German electricity assuming the gas is used in efficient combined-cycle turbine generators.

Thus Germany could potentially store enough renewable juice in gas form to last it through a days-long midwinter calm of the sort which feasible amounts of pumped storage could probably never cope with.

For nations like Germany and the UK which make massive use of gas in the home and industry, too, supplies of natural gas made sustainably are potentially a secure option compared to Russian imports, though they could never compete on price at the moment.

Could be large for LNG cars - and for nuclear power

Then there's another important plus for the ZSW synthigas plan, which is that natural gas can, of course, be liquefied or compressed and used as a portable fuel. Diesel vehicles can run on LNG with relatively minor modifications and infrastructure - certainly minor compared to converting to an all-electric transport system. They offer superior performance to battery vehicles, too. And best of all, in this case the competition isn't cheap natural gas from underground but tremendously heavily taxed motor fuel, possibly offering profits right away.

There are two main problems here, though. First is the supply of carbon dioxide to make the synthi-gas with. There's tons of the stuff about, of course, but sucking it out of the air or sea is not easy and would consume a lot of energy in itself. Even sequestering it out of fossil powerplant exhausts is a largely unproven idea, and in any case a low-carbon future wouldn't offer any such exhausts to harvest.

Even if the supply of CO2 can be resolved, it's still necessary to generate all of today's total energy usage - electricity, gas, petroleum, coal, all of it - somehow. Some green visionaries consider that this is possible using only renewable power, though their assumptions are very optimistic and rely on most of humanity remaining in poverty - or Western living standards descending a long way to meet slightly-improved ones elsewhere.

Not even the most ardent renewables fanciers could contend that wind, solar et al could supply all current energy demand and huge amounts more to cope with 40 per cent synthigas storage losses and carbon sequestration. Even so, it's a very interesting and potentially useful idea, the more so in that serious ZSW engineers are examining it at multimegawatt scale.

One should note that it is also, potentially, a boon for nuclear power. Green advocates often assert that nuclear power plants must be run at full power all the time, but this is untrue: those of France can and do operate in load-following mode, on average running at perhaps 75 per cent capacity (as opposed to the 30 per cent normal for wind turbines). This is necessary as France gets most of its electricity from nuclear.

It is true, however, that the economics of nuclear power would improve markedly if the plants could run closer to full capacity: which they could potentially do using the ZSW synthigas tech. Gas so produced would be very cheap indeed, as the extra uranium used would barely affect the running costs of a nuclear plant - fuel accounts for a very small proportion of the cost of nuclear electricity, which mainly results from building, decommissioning, safety, personnel etc.

The possible future availability of carbon-neutral, secure natural gas supply is also of serious interest to gas microgeneration fanciers, and for other applications in gas-powered fuel cells such as the recently hugely-splashed "Bloom Box".

No matter where one stands in the modern energy debate, this one could be interesting if it pans out. There's a statement from the German researchers here. ®