An important part of the energy discussion is that different sources of energy are appropriate for different needs. Gasoline and diesel fuel are the most reliable, efficient, cost-effective way to power vehicles. Oil is a critical input for many chemistry-driven products, all benefiting humankind. Important health and safety products such as Plexiglas, artificial limbs, and aspirin are oil based. And recreational and convenience products might not be “necessary,” but undeniably make the world more comfortable.

Another “evil” fossil-fuel-based energy source is coal. Many things are made from coal-powered energy. For example, steel is necessary for safe and secure factories, offices, and homes. We can’t produce steel without coal.

A key consideration must be the amount of power generated. Is a power source effective? Does it produce more energy than it consumes? In order to be effective, a source must generate, and we must be able to capture and use, more power than is used in consuming it. This is called “energy density” and “power density.” As physics teaches, “energy” is the ability to do work, and “power” is the rate of doing that work. In order to be economically useful, the energy and power produced needs to be high. The energy produced by many sources (wood, ethanol, wind, and solar) is generally very low. These are not economically productive power sources. This is ignored by radical environmentalists.

Most current renewable fuel sources have low energy and power numbers hence the problems. The power density of wind is only about 1.2 watts per square meter (W/m2). The largest off-shore wind field, the London Array, only has a power density of about 2.5 W/m2. Wind turbines in Iowa cornfields are not any better.

Because solar panel technology is very ineffective at converting sunlight into electricity, the power density is only about 5 W/m2. Even in the desert, energy from the sun has a power density of only about 200 W/m2. The amount captured by solar panels is only a tenth of that, about 20 W/m2. The density of sun in Iowa is about 170 W/m2 at its June/July peak, resulting in a captured density of about 5 W/m2.

Yet some activists claim Iowa can be the next solar king, arguing that solar in Iowa can produce “comparable electricity as one located in Miami, Houston, (or) Atlanta.” Note that photos of solar panels show acres and acres across good Iowa farmland. At least farmers can still grow crops near wind towers.

A similar problem exists in using crops to make ethanol the power density is low (0.05 W/m2). Some argue that feeding grain to animals is inefficient and a poor way to feed people. If feeding animals is bad, converting corn to ethanol is an even more inefficient use of crops.

In contrast, the power density of natural gas is 28 W/m2 and gas and coal-fired power plants often near 1,000 W/m2. Even a propane-powered home generator has a power density of almost 1,000 W/m2. If, as a consumer, you are comparing energy sources power density will overwhelmingly show that gas, coal, or propane should be used for electricity and heat generation. However, most people don’t know about “energy density” and “power density.”

We must bring power density to the front of energy economics and planning, consider the amount of power we get from original sources, and choose the most productive energy source.

If Iowans truly want to “go off the grid,” help the environment, and be energy efficient, they should invest in home generators and use propane or natural gas. They should encourage the use of oil and coal, not discourage it.

The views expressed in this column are those of the author and not necessarily those of the Public Interest Institute. They are brought to you in the interest of a better informed citizenry.

Deborah D. Thornton is a research analyst a the Public Interest Institute in Mount Pleasant.