Article

Go ahead, do the math

All renewable energies have a common fault: They are very dilute. Massive areas are needed to produce small amounts of energy. Solar and wind have strong periodicity and do not match actual electricity use.

University of Maine mathematics professor Jerry Farlow (BDN op-ed, April 5) calls for the appropriateness of math knowledge.

Again, on April 6 the editor of Fortune promotes "Math key to nation's future." Here is some very simple energy-related math that every Mainer should understand.

A liquefied natural gas tanker holds between 100,000 and 200,000 cubic meters of LNG.

When converted to gas the volume increases by a factor of 600.

A cubic meter is about 30 cubic feet

A cubic foot of natural has an energy content of about 1000 Btu

A power plant like the one at Veazie uses 7000 Btu to make one kilowatt-hour

Maine Yankee could generate six billion kilowatt-hours each year

Now do the math: About one LNG tanker load is required every 20 days to supply the gas needed to generate the electricity once provided by Maine Yankee. Political leaders in 1995 should have done the math and had the courage to cheer for the rebuilding of Maine Yankee - not its cancellation. Instead, they listened to public opinion polls.

Let's assume that 10,000 households in Maine have roof orientations that could manage the installation of 100 square feet (ten square meters) of photovoltaic array.... more [truncated due to possible copyright]  
University of Maine mathematics professor Jerry Farlow (BDN op-ed, April 5) calls for the appropriateness of math knowledge.

Again, on April 6 the editor of Fortune promotes "Math key to nation's future." Here is some very simple energy-related math that every Mainer should understand.

A liquefied natural gas tanker holds between 100,000 and 200,000 cubic meters of LNG.

When converted to gas the volume increases by a factor of 600.

A cubic meter is about 30 cubic feet

A cubic foot of natural has an energy content of about 1000 Btu

A power plant like the one at Veazie uses 7000 Btu to make one kilowatt-hour

Maine Yankee could generate six billion kilowatt-hours each year

Now do the math: About one LNG tanker load is required every 20 days to supply the gas needed to generate the electricity once provided by Maine Yankee. Political leaders in 1995 should have done the math and had the courage to cheer for the rebuilding of Maine Yankee - not its cancellation. Instead, they listened to public opinion polls.

Let's assume that 10,000 households in Maine have roof orientations that could manage the installation of 100 square feet (ten square meters) of photovoltaic array. A square meter of such an array will produce about 200 kilowatt-hours per year. Maine uses about 11 billion kilowatt-hours per year. This photovoltaic effort would produce one kilowatt-hour of electricity for every 500 we use.

A wind machine with a diameter of 250 feet - like the ones being installed at Mars Hill - will produce an annual energy of about 1000 kilowatt-hours for each square meter of wind disc. One machine will produce about five million kilowatt-hours per year. Again; Maine uses about 11 billion kilowatt-hours per year. Divide eleven billion by five million. The result: 200 such machines will produce ten percent of Maine electricity.

The forest of Maine will, on a steady yield basis, produce an annual yield of about five tons of biomass per acre. About four pounds of biomass are required to generate one kilowatt-hour. Baxter State Park has about 200,000 acres. If this area were devoted to short rotation wood crops, we could provide one kilowatt-hour for every 20 we need.

The U.S. Department of Energy (the Energy Information Administration) uses an accounting system in which 10,000 Btu thermal input is required for every kilowatt-hour generated. Thus Maine's annual eleven billion kilowatt-hours electric use requires an input of about 110 trillion Btu. Maine consumes about 233 trillion Btu of petroleum energy each year. (This 2001 data implies a petroleum consumption of about 30 barrels per person.)

Most of this petroleum is used in the transportation sector and has almost nothing to do with electric power generation. As we have seen above, the generation of significant electricity with renewable energy would be a major struggle; the notion that we should approach twice that much energy to help replace petroleum becomes absurd.

Every politico and energy pundit touts renewable energy. Tom Friedman in a recent public radio piece scolded the administration for not doing more research on renewables.

Won't work. Friedman won't, or can't, do the arithmetic of renewable energy. The numbers used above - the 1000 kWh per square meter for wind, the 200 kWh for Photovoltaics and the four pounds of biomass required for each kwh - are established by laws of physics.

All the research in the world will do little to change this. Better methods of harvesting biomass, cheaper solar collectors, etc. may be possible, but don't look to a "break-through" that will permit renewable energy to keep the future like the past.

All renewable energies have a common fault: They are very dilute. Massive areas are needed to produce small amounts of energy. Solar and wind have strong periodicity and do not match actual electricity use.

India and China are increasing their nuclear capacity ten-fold. They can do the math, and don't need to listen to the Tom Friedmans of this world.

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


Source: http://www.bangornews.com/n...

APR 12 2006
https://www.windaction.org/posts/2142-go-ahead-do-the-math
back to top