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The Real Problem With Renewable Energy

June 15, 2010 at 12:03 pm Matt Leave a comment Go to comments

From Robert Bryce of the Manhattan Institute:

Given the raging hype over renewable energy sources, those numbers, which are readily available from the Energy Information Administration, are remarkable. Over the past six decades tens of billions of dollars have been spent on renewable and alternative energy schemes such as wind energy, solar energy, corn and other biofuels, and electric cars. All have aimed at cutting our hydrocarbon use. And yet only nuclear power, which went from zero to about 8.5% of the U.S. primary energy over that time frame, has managed to steal significant market share from coal, oil and natural gas.

In other words, despite these huge investments, renewables’ share of the energy market has been shrinking. What’s happening? While conspiracy theorists may want to believe that Big Oil, Big Coal and Big Nuclear are stifling the growth of renewables, the simple truth is that coal, oil, natural gas and nuclear can satisfy the Four Imperatives: power density, energy density, cost and scale.

The Four Imperatives provide a simplified way to analyze the physics and math that rule our energy and its delivery, the latter better known as power. Before going further we must differentiate between energy and power. If you recall your high school physics, the definitions are straightforward: Energy is the ability to do work; power is the rate at which work gets done. Put another way, energy is an amount; power is a rate. And rates are more telling than amounts.

The first of the Four Imperatives, power density, is the most telling of the rates. Power density refers to the energy flow that can be harnessed from a given unit of volume, area or mass. Common metrics of power density include: horsepower per cubic inch, watts per square meter and watts per kilogram. And given the current infatuation with renewable energy sources like wind and solar, the essential metric for power density is watts per square meter (W/m2), which shows how much power can be derived from a given piece of real estate. It is also the metric that exposes the inherent weakness of sources like corn ethanol, wind energy and solar energy. If a source has low power density, then it will likely require too much real estate, material or space to provide the power that we demand at prices we can afford or in the vast quantities that the world needs.[...]

Now let’s consider the power density of wind energy, which is about 1.2 W/m2, and solar photovoltaic, which can produce about 6.7 W/m2. Both sources are superior to corn ethanol (nearly everything is), but they are incurably intermittent, which makes them of marginal value in a world that demands always-available power. Nor can they compare to the power density of sources like natural gas, oil and nuclear. For instance, a marginal natural gas well, producing 60,000 cubic feet per day, has a power density of about 28 W/m2. An oil well, producing 10 barrels per day, has a power density of about 27 W/m2. Meanwhile, a nuclear power plant like the South Texas Project–even if you include the entire 19 square-mile tract upon which the project is sited–produces about 56 W/m2.

Simple math shows that a marginal gas or oil well has a power density at least 22 times that of a wind turbine while a nuclear power plant has a power density that is more than 8 times that of a solar photovoltaic facility. Those numbers explain why power density matters so much: if you start with a source that has low power density, you have to compensate for that low density by utilizing more resources such as land, steel, and ultra-long transmission lines. Those additional inputs then reduce the project’s economic viability and its ability to scale.

But this won’t stop foolish Ohio politicians from attempting to manipulate the market and encourage the use of wildly inefficient forms of energy through tax credits and state partnerships to build giant ugly windmills in Lake Erie.

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