Low Emission Electricity Plants

BishopBerkeley writes "Nature is reporting (I have a univ. IP, so hopefully the link works for everyone) that plans are underway to build a power plant in Scotland that dramatically reduces carbon emission in fossil fuel burning power plants. The process will use steam to crack methane into hydrogen and carbon dioxide. The hydrogen is then burned, and the carbon dioxide is pumped into deposits under the North Sea. If it works, will resistance to the Kyoto Treaty finally go away?"

Comments

Depositing CO2

[Pegasus]

There's a whole article in this month Scientific American on that topic. They examine three different methods of depositing CO2 from burning fossil fuels. I hope it will be online next month.

Re:Just a new method to dump carbon dioxide

[PhilHibbs]

From Wikipedia:

Another proposed form of carbon sequestration in the ocean is direct injection. In this method, carbon dioxide is pumped directly into the water at depth, and expected to form "lakes" of liquid CO2 at the bottom. Experiments carried out in moderate to deep waters (350 - 3600 meters) indicate that the liquid CO2 reacts to form solid CO2 clathrate hydrates which gradually dissolve in the surrounding waters.

Also:

Phytoplankton in the oceans, like trees, use photosynthesis to extract carbon from CO2. They are the starting point of the marine food chain.

So it's like fertilizer for the seas.

Unfortunately... wrong solution, too late

[Engineer-Poet]

The reaction of methane and steam to form hydrogen and CO2 is energetically downhill. In practice, this means that the efficiency of the conversion of fuel to energy goes down.

If there was natural gas to spare, this wouldn't matter so much. Unfortunately, North American gas production has already peaked ; I'm sure Britain's situation is no better. We cannot afford to sacrifice efficiency to sequester CO2.

What we could use is technologies which allow CO2 to be captured and simultaneously boost efficiency. Solid-oxide fuel cells and molten-carbonate fuel cells, which can operate at substantial pressure, are good candidates for these. SOFC's in particular look good to me; their charge carriers are oxygen ions (O--) so the mixture on the fuel side of the cell shifts from fuel to CO2 and H2O. This means you don't have to exhaust CO2 along with the air feed, and it's easier to capture.

High-efficiency combined-cycle gas turbines can convert natural gas to electricity with an efficiency on the order of 60%, but they require large, central installations. SOFC's could conceivably be made in home-sized units without losing efficiency, and the waste heat from the process could be used for space heat and hot water. Heating with them would result in a substantial excess of electricity over local needs, which could be diverted to heat pumps to reduce the overall fuel required. (If you can get 60% out of the fuel cell and 3.3:1 out of the heat pump, the total CoP of the system can go as high as 2.4.) Run CO2 exhaust lines in parallel with the natural-gas supply lines, and you've really got something.