I am late in posting a reference to this interesting op-ed from the WSJ a short while ago by Robert Bryce on the potential role of renewables in future energy supply. Better late than never, here is an excerpt:

The latest data from the U.S. Energy Information Administration show that total solar and wind output for 2008 will likely be about 45,493,000 megawatt-hours. That sounds significant until you consider this number: 4,118,198,000 megawatt-hours. That’s the total amount of electricity generated during the rolling 12-month period that ended last November. Solar and wind, in other words, produce about 1.1% of America’s total electricity consumption.

Of course, you might respond that renewables need to start somewhere. True enough — and to be clear, I’m not opposed to renewables. I have solar panels on the roof of my house here in Texas that generate 3,200 watts. And those panels (which were heavily subsidized by Austin Energy, the city-owned utility) provide about one-third of the electricity my family of five consumes. Better still, solar panel producers like First Solar Inc. are lowering the cost of solar cells. On the day of Mr. Obama’s speech, the company announced that it is now producing solar cells for $0.98 per watt, thereby breaking the important $1-per-watt price barrier.

And yet, while price reductions are important, the wind is intermittent, and so are sunny days. That means they cannot provide the baseload power, i.e., the amount of electricity required to meet minimum demand, that Americans want.

That issue aside, the scale problem persists. For the sake of convenience, let’s convert the energy produced by U.S. wind and solar installations into oil equivalents.

The conversion of electricity into oil terms is straightforward: one barrel of oil contains the energy equivalent of 1.64 megawatt-hours of electricity. Thus, 45,493,000 megawatt-hours divided by 1.64 megawatt-hours per barrel of oil equals 27.7 million barrels of oil equivalent from solar and wind for all of 2008.

Now divide that 27.7 million barrels by 365 days and you find that solar and wind sources are providing the equivalent of 76,000 barrels of oil per day. America’s total primary energy use is about 47.4 million barrels of oil equivalent per day.

Of that 47.4 million barrels of oil equivalent, oil itself has the biggest share — we consume about 19 million barrels per day. Natural gas is the second-biggest contributor, supplying the equivalent of 11.9 million barrels of oil, while coal provides the equivalent of 11.5 million barrels of oil per day. The balance comes from nuclear power (about 3.8 million barrels per day), and hydropower (about 1.1 million barrels), with smaller contributions coming from wind, solar, geothermal, wood waste, and other sources.

Here’s another way to consider the 76,000 barrels of oil equivalent per day that come from solar and wind: It’s approximately equal to the raw energy output of one average-sized coal mine.

During his address to Congress, Mr. Obama did not mention coal — the fuel that provides nearly a quarter of total primary energy and about half of America’s electricity — except to say that the U.S. should develop “clean coal.” He didn’t mention nuclear power, only “nuclear proliferation,” even though nuclear power is likely the best long-term solution to policy makers’ desire to cut U.S. carbon emissions. He didn’t mention natural gas, even though it provides about 25% of America’s total primary energy needs. Furthermore, the U.S. has huge quantities of gas, and it’s the only fuel source that can provide the stand-by generation capacity needed for wind and solar installations. Finally, he didn’t mention oil, the backbone fuel of the world transportation sector, except to say that the U.S. imports too much of it.

Perhaps the president’s omissions are understandable. America has an intense love-hate relationship with hydrocarbons in general, and with coal and oil in particular. And with increasing political pressure to cut carbon-dioxide emissions, that love-hate relationship has only gotten more complicated.

But the problem of scale means that these hydrocarbons just won’t go away. Sure, Mr. Obama can double the output from solar and wind. And then double it again. And again. And again. But getting from 76,000 barrels of oil equivalent per day to something close to the 47.4 million barrels of oil equivalent per day needed to keep the U.S. economy running is going to take a long, long time.