Monday, May 3, 2010

A Note On Energy Density

An unpleasant example, but nonetheless a sobering reminder of just how much of an expansion in renewables will be needed to replace a significant slice of energy produced from fossil fuels.

Energy Outlook puts out some numbers:

Cape Wind and the Macondo prospect that the Deepwater Horizon rig was drilling into represent opposite poles of the energy spectrum, and not just because the latter is now leaking oil into the marine environment at a rate that the latest estimate puts at 5,000 barrels per day, much higher than initially thought. Cape Wind would tap into the clean and renewable, but extremely diffuse energy sources that surround us. After taking into account the restrictions imposed by DOI, its 130 turbines would on average generate as much electricity as a gas turbine power plant consuming a quantity of natural gas equivalent to 6,000 bbls/day of oil. In other words, it takes a very large array of offshore wind turbines to match the energy in the oil currently leaking from a single well. Platforms similar to what BP might have been planning to install after successfully completing the exploration of Macondo routinely produce up to 20 times that much oil.

The implications of this huge difference in energy density are clear. Without the energy concentration that nature has embedded in fossil fuels over many millennia, the hardware required to tap natural energy flows in real time becomes vast in extent.

Over at Science Friday the same point was made with regards to the potential of algae and microbes in producing fuels. They too suffer from the problem of capturing diffuse sunlight..the effect being that very large extents of land are required to produce significant quantities of fuel. The estimates given were a few thousand gallons of fuel per acre per year.

Currently the U.S uses about 275+ billion gallons of oil per year. Currently only a few percent of the liquid fuel needs of the U.S are met by biofuels.

Similar differences apply to the two fastest growing consumers of energy ..China and India.

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