Renewable Gas #5 : Beyond BiogasPosted on July 11th, 2011 3 comments
I was speaking to a nuclear power “waverer” the other day. They said that George Monbiot or Mark Lynas was saying that since Germany has cancelled its nuclear power programme, Germany’s Carbon Dioxide emissions will increase, because they will be using coal and Natural Gas power stations :-
I explained that this was a common misconception, and that Germany is still planning to meet their carbon targets, and that it can be done even with coal and gas power plants because in a few decades’ time the coal and Natural Gas power plants will only be used a couple of weeks a year in total to back up all the renewables, such as wind power and solar power, that Germany is building.
This is not the end of the story, however.
In 20 or 30 years’ time, Germany will need to abandon burning coal. It only wants to burn coal at the moment for power generation because it has – indigenous coal – energy it can dig up at home. However, because of the carbon emissions, coal-fired power generation will become untenable over time. What will really bridge the gap after the exit of nuclear power will be gas burned in Combined Cycle turbines.
But, as the Green Alliance have pointed out for the UK, building more CCGT and burning Natural Gas to generate electricity risks being locked-in to carbon emissions that will be off target within decades :-
“Avoiding gas lock-in : Why a second dash for gas is not in the UK’s interest : …Gas will continue to have an important role as a flexible fuel in the transition to a low carbon economy. However, because the UK has already cut its emissions by switching from coal to gas, a second dash for gas could prevent us from meeting our carbon budgets or significantly increase the cost of meeting them. Relying on unabated gas which is cheap to build now doesn’t lead to lower cost decarbonisation; it will simply load the cost of decarbonisation into the 2020s…”
However, the key factor that none of these people have mentioned so far is that within a couple of decades, renewable sources of gas should be widely available, and provide a truly carbon-free back up to intermittent wind power and variable solar power.
Gas is easy to store – and it could even be stored in the gas grid :-
[ IMPORTANT : Regarding the design above - if fossil fuels are used to top up the tank of carbon dioxide (CO2) for the methanation of wind-reformed hydrogen (H2), this is "carbon capture", but the carbon dioxide would have to be captured a second time when the renewable gas is burned for power, otherwise this would result in net carbon dioxide emissions. ]
The various ways to make synthetic or synthesis natural gas (SNG) from biomass resources and spare wind and solar power may take some time to perfect and roll out. For example this snippet was posted to The Oil Drum back in 2008 :-
“Boof on March 10, 2008 – 2:10am : As the song says ‘this could be the start of something big’. I wouldn’t bother too much cleaning up the biosyngas, just store it in a low pressure gasometer for use in low speed diesel or turbine generators. There is a nice symmetry about forest areas helping backup renewables located in desert, offshore or mountain areas. Urban sewage plants could also store biomethane for backup purposes…”
All the same, there will be some competition for the use of this grid Renewable Gas – transport :-
The renewable gas that most people have heard of, biogas, will be an excellent companion to biosyngas – and they will both be used in biorefineries to create a range of fuels and other products :-
[ UPDATE : EurActiv has more on Germany's strategy. ]Big Number, Big Picture, Biofools, British Biogas, Carbon Capture, Coal Hell, Design Matters, Direction of Travel, Drive Train, Energy Change, Energy Revival, Engineering Marvel, Fossilised Fuels, Fuel Poverty, Green Investment, Green Power, Hydrocarbon Hegemony, Major Shift, Marvellous Wonderful, National Energy, National Power, Nuclear Nuisance, Nuclear Shambles, Optimistic Generation, Peak Emissions, Policy Warfare, Realistic Models, Renewable Gas, Renewable Resource, Solar Sunrise, Solution City, The War on Error, Tree Family, Unnatural Gas, Wasted Resource, Wind of Fortune
3 responses to “Renewable Gas #5 : Beyond Biogas”
The front end doesn’t have to be standard electrolysis of water (well, it does for wind). Direct Photoelectrochemical Water Splitting ( http://www.nrel.gov/hydrogen/proj_production_delivery.html#split ) might be the better approach for solar. It all depends where the efficiency of that process stacks up v the in-series efficiency of photovoltaic power followed by electrolysis.
A section in “Wasserstoff fuer Alles” compares current electrolysis to a Hoescht patent [No DE 3401636 A1]. Current electrolysis cell is shown with an efficiency of 81%. The patented method is claimed to exceed 94%. You are correct in quoting 75% for typical electrolysers. I guess that includes peripheral losses.
You also should consider the amount of water necessary. See: Ulf Bossel [Proc IEEE page 1827 Vol 94 No 10, October 2006] “About 50 jumbo jets leave Frankfurt airport every day, each loaded with 130 tons of kersene. If replaced on a 1:1 energy basis by 50 tons of liquid hydrogen… Every day 22,500 tons of water would have to be electrolysed… the entire water supply of Frankfurt (650,000 inhabitants) and 25 full size power plants would be needed…”
If on the other hand you generate the hydrogen by thermochemical gasification from biomass of 40 to 50% water content that is enough to provide the water. That moisture content is typical of biomass as harvested. You don’t need to dry it as in co-firing by Drax. You don’t need excess moisture to ferment it as in AD biogas. The loss this method of gasification should be as low as 8%.
NB: Ulf Bossel is refered to as ‘That campaigner against hyrogen’ by K-H Tetzlaff author of Wasserstoff fuer Alles. Chemists and aero engineers come with differing assumptions!
Genuinely educational thanks, I reckon your trusty visitors might want further well written articles like that maintain the good effort.
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