Fudged electricity numbers

Recently, Rich Hewitt of the Bangor Daily News staff wrote a very responsible thousand-word piece on the anniversary of the wind turbine installation at the G. M. Allen & Sons blueberry plant on route 15 in Orland. The U. S. Public Interest Research Group took this occasion to release a report on the potential of renewable energy in Maine. The report concluded: “We must ensure that we expand our current energy mix to include nonhydro renewables such as clean biomass, wind and solar.” Then again: “Maine’s potential for electric generation from these renewable resources is 12.5 billion [annual?] kilowatthours…enough to power 1.2 million homes.”

Let’s assume that we can get four billion kilowatthours (kWh) from each: wind, solar and biomass.

Wind: Ralph Chapman reported that the wind machine at Orland produced 27,000 kWh in its one year of operation. If we are to get four billion kWh per year from wind energy in Maine we will need about 150,000 Orland-type wind machines. Here is another way to look at the output of the Orland wind unit: an electric clothes dryer uses about 5.6 kilowatts. If that dryer unit were to run steady for one year, the energy use would be about 50,000 hWh. Almost two Orland wind machines would be required just to keep one electric dryer operating full time. Let’s assume that we feel so dedicated to the importance of renewable energy that we are willing to commit to the construction of the equivalent of 150,000 Orland wind machines. The maximum demand for electricity occurs late in the afternoon around Dec. 20. This is not a high-wind period. We must build all the fossil fuel or biomass plants needed to carry the electric load; then shut some units down when the wind blows. Again, at nine a.m. on a Sunday morning in June, a high wind domain may be available – what does one do with the electricity generated by the wind machines? Very few customers demand electricity at that time. Solar: Here are some very optimistic assumptions for a back-of-the-envelope calculation. Each day of the year the sun stays at high noon, no cloud cover, for five hours. During that five-hour period each square foot of solar collector “sees” 100 watts of solar energy. The conversion efficiency to electricity is 10 percent. To keep the arithmetic simple, lets assume 400 days in year. This yields 200 kWh of electric energy each year from one square foot of photovoltaic array. If 200,000 households in Maine could find a place to mount 100 square feet of solar collector (that’s a lot), we could meet the annual requirement of 4 billion kilowatthours. But, solar generated electricity, like the wind, does not match the profile of electricity use. What becomes of all that solar electricity generated on a clear Sunday morning in June when the demand for electricity is small? Where does the electricity come from at suppertime in December?

Biomass: That is different. Many studies have been made of the biomass (forest residue) available as fuel from the Maine forest. Here is a good guess: if we harvested all the current forest residue – tops, branches, dead stuff, etc. we could collect 15 million tons per year and generate (depending on moisture content) nearly seven billion kWh each year. In the halcyon biomass power days of the late 80s Maine actually produced about four billion kWh of electric energy each year from biomass. At the moment biomass is contributing between one and two billion kWh per year. About 20 percent of our current Bangor Hydro bill covers the cost of buying down mostly biomass contracts that proved financially non-competitive with other sources of generation. Unlike wind and solar, we could generate substantial amounts of electricity with biomass if the public were willing to see higher electric bills.

When the U.S. Public Interest Research Group urged us to expand the energy grid to include more solar, wind and biomass they got one-third of it right. We could expand the biomass portion, but I don’t think we would like what it would do to the nutrient balance of our forest, roads to haul the stuff, and the price of electricity.

I think it is understandable that the U. S. Public Interest Research Group should overreach the data in order to promote wind and solar energy. They have an agenda, a constituency, and need support. Less understandable is the silence of at least several hundred readers of the BDN that know enough about the technical aspects of electric energy generation to reject out of hand any projected seamless segue from current dependence on fossil fuels to solar and wind energy. Where are the hundreds of letters to the editor crying “foul”?

Richard C. Hill, of Old Town, is professor emeritus at the University of Maine.