My plan to write a column about methane hydrate has now blossomed into a four part series on global warming and the future of the plant. Part I covered the science of methane hydrate. Part II explained the reasons why we are on the path to exceed the U.N. target of limiting carbon dioxide in the atmosphere to 450 ppm. Part III was a review of both the potential and limitations of carbon sequestration as method to address climate change as well as the potential benefits of developing an artificial photosynthesis technology. The question for this week is “Can we convert to renewable, no- or low-carbon emitting energy sources fast enough to stay below the U.N. target?”
To address the question, first we need to understand just how much energy we are talking about. Each year, humanity consumes approximately 145,000 terawatt-hours of energy to generate electricity, drive our cars and trucks, heat our homes and run our factories, of which 120,000 come from fossil fuels. (A terawatt is equal to one trillion watts.) Here in the U.S we consume 27,000 terawatt-hours per year of which 19,000 come from fossil fuels.
These numbers are so large they are difficult to wrap your mind around. So rather than confront the question of converting the entire global to renewable fuels, I’ll start by limiting the discussion to U.S. electricity generation. Each year in the U.S. we consume approximately 4,000 terawatt-hours of electricity, 2,800 of which come from fossil fuels, primarily coal and natural gas. Options to replace the 2,800 terawatt hours with no- or low-carbon emission sources include solar, wind, hydroelectric, and nuclear power.
To illustrate the challenge and magnitude transitioning away from fossil fuels, let me walk you through the math for installing 2,800 terawatt-hours per year of solar electric power. Currently in the U.S. there are approximately 100 utility-owned solar power stations which have an average peak output of 34 megawatts (MW). Peak capacity occurs on sunny summer days at noon. Since it is often cloudy or night time, time-weighted average power output, called the capacity factor, for a solar panel is in the range of 15-20% of the peak capacity. Most media reports on solar power only quote the peak power output which can be deceiving. Currently solar power is providing a paltry 0.4% of our electricity in the U.S.
The existing fleet of U.S. solar power stations includes older and smaller facilities which bring the average power output down. Large solar power plants being built today have peak capacities of up to 100 MW and next generation solar power plants, which use mirrors and lenses to concentrate sunlight, with even larger capacities are being built as well. So if we embarked on great national project to install solar power stations optimistic but reasonable assumptions for performance would be an average peak capacity of 150 MW with a capacity factor of 20%. With these assumptions, generating 2,800 terawatt-hours per year of electricity would require 10,000 solar power facilities.
An attempt to construct 10,000 new solar power stations would confront a significant number of potentially crippling limitations including availability of raw materials, money, and locations with adequate sunlight. The other critical constraint to consider is time. The atmosphere currently contains 390 ppm of carbon dioxide and at current carbon dioxide emission rates we will surpass the limit of 450 ppm within 20 years. So let’s use 20 years as our target for when we want have all of these new facilities on line. Twenty years is approximately 1,000 weeks, which translates to completing of 10 massive solar power plants per week, every week, for 20 years. The number of solar power stations needed would be reduced if we installed more wind and nuclear power plants; however, the problem would remain the same because these facilities are expensive and complex as well. Also recall that the efforts I have described so far only address electricity, leaving our other fossil-fuel-using energy sectors still to be addressed.
Thus far in the calculations I have not considered the possibility of reducing our energy consumption. Per capita energy consumption in the E.U. and Japan is only half of the current level in the U.S. suggesting that we could certainly do better. But would it be enough? Cutting our per capita energy consumption by half would help, but in the example above, we would still need to build five massive solar power stations per week for 20 years, still a nearly impossible task. Despite what you may have read, the U.S. is not making much progress in the energy efficiency arena. U.S. per capita energy consumption from 1900 to 2008 dropped by only 2%.
Even if we make progress in the U.S., there is little reason to hope that the rest of the world would follow suit. Consider this current real world example. Whatever one thinks of “fracking”, it is driving glut of natural gas supply in the U.S.; thereby, lowering its price and inspiring many electric power utilities to convert from coal to natural gas. Generating electricity with natural gas rather than coal produces less carbon dioxide per unit of power which is the right direction to go. Unfortunately, the coal that is being supplanted by natural gas in U.S. power plants is not being left in the ground but rather is being mined and exported to other countries negating the emissions reductions achieved in the U.S from switching to natural gas. As I covered recently in “If We Drill It or Mine It We’re Going to Burn it”, the only way to reduce carbon dioxide emissions from fossil fuels is to leave them in the ground.
President Carter tried to warn us in the 1970s that this crisis was coming and installed solar panels on the White House to try to lead the way. For these forwarding thinking efforts he was mocked for as asking us to “freeze in the dark.” But he was right. Each day the sun pours 10,000 to 20,000 times more energy on the earth that what humanity consumes clearly indicating that we can power global civilization with solar power. If we could have listed to President Carter 35 years ago and gotten started back then we just might have had enough time to avoid the looming climate and energy crisis. Now we don’t.
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