Sunday, September 27, 2009
Each solution carries hefty price
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Brian Lindholm
Lindholm is a mechanical engineer who lives in Salem.
The U.S. House recently passed the Waxman-Markey bill, commonly called "carbon cap and trade." Under this law, carbon dioxide emissions would be explicitly capped, with utilities purchasing permits to be allowed to emit CO2. The quantity of permits distributed would be gradually reduced, cutting emissions by 83 percent by the year 2050. Estimates of annual cost impact to U.S. households have varied wildly, ranging from $140 to nearly $6,000. What would really happen?
First, one must understand that the total electricity supplied by utilities must exactly match the total demand of the grid. Not the other way around. If they fail to supply enough electricity and line voltages sag, they must fire up more generators until demand is met.
The generators fired up first are those powered by hydroelectric and renewables, such as wind and solar. Why? Because they produce power that's essentially free. Unfortunately, it's very limited in supply. Hydro provides about 7 percent of U.S. electricity, wind about 1 percent, and solar a trivial amount. If hydro and renewables can't meed demand, then nuclear is added next. Nuclear stations produce power at about 2 cents per kilowatt-hour, providing 20 percent of U.S. electricity.
Next, coal-fired stations are activated. They cost about 4 cents per kilowatt-hour to operate but emit 1,700 pounds of CO2 per megawatt-hour of electricity produced. And last, gas-fired turbines are used. They produce only 850 pounds of CO2 per megawatt-hour but cost more than 10 cents per kilowatt-hour to operate. Coal and gas supply 50 percent and 22 percent of U.S. electricity, respectively.
Because of these economics, nuclear stations operate more than 90 percent of the time, coal-fired nearly 75 percent of the time, and gas-fired under 25 percent of the time. Utilities would love to get more out of hydroelectric and renewables, but these are intrinsically limited by nature (drought, calm days, night, etc.), yielding about 30 percent effective utilization.
How will Waxman-Markey affect this mix? Well, instead of using whatever means is cheapest, utilities would have to alter their mix to limit CO2 emissions. Because nuclear, hydro and renewables are operated fully already, the only option is to burn gas in preference to coal. As permit restrictions tightened, gas-fired turbines would run increasingly often while coal-fired plants increasingly sat idle. Electricity prices would rise by at least 6 cents per kilowatt-hour, costing households $800 annually.
Because of ever-decreasing permit limits, operators would eventually run with zero coal, probably around the year 2030. And when the limits decreased still further (per the plan), even natural gas would emit too much. Unable to meet electrical demand without exceeding permit limits, utilities would have to implement rolling blackouts. By 2050, all of America's coal-fired and two-thirds of its gas-fired stations would be permanently mothballed, reducing our total generating capability by more than 50 percent. Blackouts would occur daily. How could we avoid this obviously unacceptable fate?
There are three options. The first is to implement carbon capture and sequestration, where CO2 is extracted from the exhaust stream and injected underground, eliminating the need for permits. This is probably feasible from an engineering standpoint, but it would cost many hundreds of billions of dollars to implement, and we'd burn through coal and gas reserves 25 percent faster to compensate for losses incurred by running CCS equipment. Power bills would double.
The second is to write off our multi-decade, multi-trillion-dollar investment in coal- and gas-fired stations and build a completely new infrastructure based on renewables. This means hundreds of thousands of acre-sized solar farms and wind turbines, gargantuan (and not yet invented) energy storage systems to compensate for supply vs. demand mismatches, and endless miles of power lines to link it all together. It would cost trillions, and power bills would skyrocket.
The third is to retrofit mothballed stations with nuclear power. This option would likely be cheapest in the long term, as we could reuse existing generators, transformers, cooling towers, etc. While straightforward and well-understood, it would still cost hundred of billions.
These options aren't mutually exclusive. We could pursue a mixture of all three. However, there's no way to avoid the truth: Waxman-Markey would substantially increase our power bills, and the U.S. Senate should think very hard before passing a counterpart version. If CO2 emissions are truly responsible for harmful global warming, then this sacrifice may be necessary. But if not, it would be a tremendous and needless burden on our economy.
