All of the “alternate energies” – wind, solar, tidal, biomass, etc. – are difficult to deploy for three reasons: (1) periodicity, (2) stochasticity and (3) dilution.
The periodicity is easy to understand. The tide comes and goes; the sun does not shine at night, etc. The stochasticity limit is forced upon us by such sources as solar (clouds come and go), wind (gusts, then calm), etc.
On Nov. 17, The Ellsworth American published a piece I had written on the performance of the wind turbines in Texas. The editor went to some difficulty to get a color graphic on the editorial page. The graphic indicated that on March 26, 2014, the wind system in Texas established a record of 10,296 megawatts. (That’s a lot! Maine total day-to-day electricity use is about 1,000 megawatts.) The next day, the wind production had dropped to 2,000 megawatts; two days later, 1,000 megawatts. Such wild fluctuation of a major energy source must drive the system managers wild. They must start and stop fossil-fuel plats to match the erratic (stochastic) power generation from the wind.
I have been writing energy pieces for Maine papers for over 20 years. I nearly always get some small response – perhaps a letter-to-the-editor, an email or two or perhaps phone calls. But this time, nothing. Dead silence. I thought I had dropped a bomb; instead, I laid an egg. But the question remains: without massive ponded hydro or other renewable resources in a back-up mode, how can land-based wind power play a significant role?
The dilute quality of the alternate energies is a more subtle difficulty. Take the energy in biomass. The energy in any phytomass (algae. moss, trees, etc.) can be no greater than the energy of formation through photosynthesis. And photosynthesis is about as efficient as 0.3 watts per square meter. That is all that’s there. If you sit on a stump and watch the trees grow, those trees accumulate energy at the rate of about 1.2 kilowatts per acre year. The units used by foresters (0.69 tons of dry material per acre year) convert to only .3 kilowatts per acre. (The number the foresters use considers only the portion of the forest that is harvested; the 1.2 kilowatts refers to all growth – roots, leaves, etc.).
To quantify the dilution of wind power, consider a supermarket. Each square meter of floor space calls for about 300 watts for lights, refrigeration, heating, etc. The energy produced by a wind farm is about 5 watts per square meter – many square meters of wind farm are needed to supply one square meter of supermarket. Building larger and larger wind turbines does not help. Larger units must be spaced farther apart. The 5 watts per square meter prevails.
China has 50 nuclear plants under construction and nearly 200 additional units in the planning stage. If eight billion people are to enjoy hot showers and cold beer, they had better put off thinking about sunshine and wind turbines.
Richard C. Hill of Old Town, now retired, taught engineering at the University of Maine in Orono.
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