The big problem with a solar panel is that it only produces power part of the time. As we discussed in How Wind Power Doesn’t Work, the intermittent nature of solar (and wind) energy doesn’t work so well on the grid. The power company still has to maintain backup power plants to replace all the solar power that is lost on days when the sun doesn’t shine.

One thing that would help solar/wind is an ability to efficiently store electricity and release it when needed. Another possibility is to convert the electricity efficiently into a hydrocarbon fuel like methane or methanol. Researchers seem to be getting a lot closer to the fuel option:

The next best thing to oil

A renewable carbon economy? Surely that’s a pipe dream? Perhaps not, now that solar power facilities are cropping up in deserts across California, Spain and North Africa. The idea is to use the sun to power chemical plants able to split carbon dioxide. Combine the resulting carbon monoxide with hydrogen and you have the beginnings of a solar fuel that could one day replace oil.

The key is to use both the heat and the electricity that the sun can provide to make both hydrogen (from water) and carbon monoxide (from carbon dioxide). High temperature electrolysis (HTE) is one way to split hydrogen away from water. By raising the temperature of the water to 850 degrees C and then adding electricity, it takes much less electricity to do the job and the efficiency goes up.

It is possible to take carbon dioxide (say from a coal-fired or natural-gas-fired power plant) and combine it with hydrogen to create methane. The big advantage of methane is that it is identical to natural gas and can therefore plug into the already-existing natural gas pipelines and infrastructure. Or you can use something like the Fischer–Tropsch process to create liquid hydrocarbons.

There is also recent research showing that a plant enzyme can make propane from CO2:

Car fuel ‘could be made from thin air’

This process of creating hydrocarbon fuels is known as the “carbon economy” or the “carbon cycle”. These videos discuss some of the possibilities:

The only problem is cost. A gallon of gasoline contains about 35 kilowatt-hours of energy, and the processes described above are not 100% efficient. Therefore, at the moment, fuels produced in this way cannot compete with fossil fuels pumped out of the ground. But as fossil fuels get more expensive and solar power gets cheaper, they eventually reach parity.

More info:
- How the Hydrogen Economy Works
- How Solar Cells Work

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