Life + Outdoors » Garlick's Notebook

More Power to You

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PG&E is planning an upgrade of its aging Humboldt Bay power station. It currently produces 135 megawatts from two steam turbine generators working at 35 percent efficiency (backed by two emergency 15-megawatt diesel-fired gas turbines). The new system would employ 10 reciprocating internal combustion engines running on natural gas, capable of producing 163 megawatts with 47 percent efficiency! Having multiple independent engines provides the flexibility to accommodate variable demand and the evolving availability of solar, wind or ocean power. Here is an outline of the new technology.

We are familiar with the four-stroke diesel engine, in which ignition occurs when high-pressure diesel is injected into the cylinder at the moment air is maximally heated by compression. No spark plug is required, as in a gasoline engine of lower compression. PG&E plans to use 10 engines, each with 18-cylinders, which take in natural gas mixed with air. The mixture is ignited at the top of the piston stroke by a tiny injection of diesel fuel. These engines have the advantage of being able to seamlessly switch to diesel fuel alone in case natural gas from Redding is disrupted by some accident to the pipeline.

The engines are cooled by fresh water through closed loops, as in your car. (The existing power station uses once-through sea water to condense steam for re-injection into its boilers.) Internal combustion engines can be noisy, but PG&E will enclose its engines in acoustically engineered buildings and use silencers on the exhaust stacks. Their Application for Certification assures us that they will be as quiet as the existing turbines. Air pollution will be reduced in spite of increased power generation, and will conform to North Coast Air Quality regulations. The planned facility will have a lower profile than the old structure, which should be dismantled when the new is completed.

To exemplify the importance of energy in our lives I share with you some data from a letter in Science by R. Burruss. One human can work at the rate of 100 watts. Dividing the world's total energy use by its population yields 2,000 watts per human. Thus, an average human is supported by the equivalent of 20 energy slaves or "Virtual Persons" (VPs), each rated at 100 watts. Pushing a 20 m.p.g. car 10,000 miles per year requires 20 VPs. But Americans use a disproportionate fraction of the world's energy, equivalent to 115 VPs per American. Please sir, can you spare a VP?

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