Stanford Professor Mark Jacobson

I was disappointed when I discovered that the list of experts at last week’s Clean Energy Summit would not include Stanford University’s Mark Jacobson. Of course, no individual is indispensable at such a summit. But as the day went by I felt his absence more and more keenly.

That’s because Jacobson is one of the few scientists looking at energy’s Big Picture. How big?

In an article published in the journal Energy & Environmental Science earlier this year, Jacobson reported the first quantitative, scientific study evaluating the top energy sources based on:

1. Potential for delivering adequate power for electricity and vehicles
2. Impacts on global warming
3. Air pollution mortality
4. Energy security
5. Water supply
6. Land use
7. Wildlife
8. Water chemical pollution
9. Thermal pollution
10. Nuclear proliferation
11. Undernutrition

By using each of these factors to assess ten major energy sources, Jacobson produced a list that should be the starting point in any discussion about our energy future. Here’s what he found:

The top electrical generating energy sources are (from best to worst):

1. Wind
2. Concentrated Solar Power (CSP)
3. Geothermal power
4. Tidal power
5. Solar photovoltaics (PV)
6. Wave power
7. Hydroelectric power
8. Nuclear power
9. Coal (even with Carbon Capture and Sequestration, CCS)

Nuclear and coal actually tied for last place.

For powering vehicles, Jacobson produced a second list. Again going from best to worst:

1. Wind BEV (Battery Electric Vehicles)
2. Wind HFCV (Hydrogen Fuel Cell Vehicles)
3. Solar CSP-BEV
4. Geothermal BEV
5. Tidal BEV
6. Solar PV-BEV
7. Wave BEV
8. Hydroelectric BEV
9. Nuclear BEV
10. Coal CCS-BEV (tied with #9)
11. Corn ethanol
12. Cellulosic ethanol

Jacobson’s findings are a surprising blow to backers of ethanol-based bio-fuels. He also had harsh words for politicians who are pouring money into this area. “Biofuels are the most damaging choice we could make in our efforts to move away from using fossil fuels,” Jacobson told a reporter. “We should be spending to promote energy technologies that cause significant reductions in carbon emissions and air-pollution mortality, not technologies that have either marginal benefits or no benefits at all.”

Jacobson highlights the need to fund wind energy in particular. He says that the entire US fleet of vehicles could be powered by as many as 144,000 5 MW wind turbines. That’s a large number. But the country has met higher production goals in the past. In WWII, Jacobson says, America built 300,000 airplanes — a far larger and more difficult job than building wind turbines.

Such a program would be positive way to stimulate and grow our economy as well, he adds.

Click me

“There is a lot of talk among politicians that we need a massive jobs program to pull the economy out of the current recession,” Jacobson says. “Well, putting people to work building wind turbines, solar plants, geothermal plants, electric vehicles and transmission lines would not only create jobs but would also reduce costs due to health care, crop damage and climate damage from current vehicle and electric power pollution, as well as provide the world with a truly unlimited supply of clean power.”

The paper is available by clicking on the journal cover.

That’s the reductionist headline for a more nuanced op-ed published recently in the WaPo by Robert Glennon.

Glennon is a professor of law and public policy at the University of Arizona and the author of an excellent new book,  Unquenchable: America’s Water Crisis and What to Do About It. He writes widely and wisely about water issues, and so his concerns about the amount of water used for Concentrated Solar Power (CSP) deserve serious consideration.

Early on in the piece, Glennon seems a bit confused about solar technology.

“Most people think of solar power as the flat panels on a neighbor’s roof that are used to heat water. This photovoltaic system directly converts the sun’s waves into electricity. But so far, it’s not commercially feasible.”

If they’re flat panels on the roof heating water, they’re almost certainly passive solar heaters, not photovoltaic (PV). I have one of these systems on my roof. If it’s generating electricity I’d sure like to know where that power is going.

And as far as PV not being commercially feasible, Glennon might want to talk with some of the tens of thousands of homeowners and businesses in the US using grid-tied PV (we’re far behind Germany and Japan in this regard) with a total capacity of over a gigawatt of electricity — enough to power approximately 750,000 homes.

Beyond these missteps, however, Glennon is right on the mark when he asks supporters of solar power to consider the amount of water needed to produce electricity by CSP.

Glennon’s op-ed is a reminder that, this time, we need to get it right.

IMHO, Glennon paints a slightly worse picture of CSP than it deserves. For example, he writes:

“…CSP uses four times as much water as a natural gas plant and twice as much as a coal or nuclear plant.”

If you read the government study he cites, however, CSP’s water usage is not quite so bad. According to the study:

“A typical coal plant or nuclear plant consumes 500 gallons of water per MWh (gal/MWh) of electricity generated. This is similar to the water consumption by a power tower.”

A power tower, pictured below, is a kind of CSP that uses mirrors to concentrate sunlight onto a single point.

Power Tower

The study continues:

“A combined-cycle natural gas plant consumes about 200 gal/MWh. A water-cooled parabolic trough plant consumes about 800 gal/MWh.”

Water intensive parabolic troughs have dominated the CSP field. But many in the solar industry see an industry shift to power towers. And many existing natural gas plants are the simple-cycle variety that use more water. Companies still build them and plan for more.

So, yes, when generating electricity, the most water-intensive CSP plants use more water than the do the least water-intensive natural gas plants.

But this doesn’t include the water used in extracting natural gas; millions of gallons of water are required to get a single well producing gas.

Glennon focuses on water in his piece, and for good reason. As writer and author Cynthia Barnett observes in her wonderful book, Mirage: Florida and the Vanishing Water of the Eastern US, water is too often left out of environmental equations. Water should be included, but as a part of the overall energy “footprint.” And the same goes for all sources of energy.

I’ll happily join Glennon and Barnett in demanding that water use be considered in regulating energy sources — as long as these new regulations aren’t limited to solar power. (Glennon gives a nod in this more inclusive direction near the end of his essay.)

It’s also worth remembering that solar power is enjoying a renaissance at the moment because of what it doesn’t produce — green house gases. Using natural gas as an energy source in the United States, on the other hand, emits 6.7 metric tons of methane annually according to a DOE study, making it the largest single contributor to human-caused methane emissions. (And because methane’s effect on global warming is 23 times greater than that of CO2, this is the equivalent of 154 tons of carbon dioxide.)

So, while I quibble over some parts of  his argument, I recognize that Glennon’s op-ed is an important reminder that this time we need to get it right; we need to use solar power mindfully. We need to ask questions of solar that we failed to ask about coal, nuclear, petroleum and gas.

Glennon points to an obvious truth that has somehow eluded us for far too long. What’s needed isn’t just a non-GHG emitting energy source. We need to change our attitude. We need to see energy, including solar, in a new, more thoughful light.