The Gore Challenge Starts Here

You've heard about Al Gore's challenge to remodel the U.S. electrical industry in 10 years to eliminate all CO2 emissions. Some commentators say the job is too big, some say it isn't, but everyone, including Al, agrees it's a big, big job.

But exactly how big? What are we up against here? How much new wind, solar, geothermal power do we need to replace the CO2 producing plants? What else might be needed to make such a system work?

We have to start with the status quo: how much of our power is clean, how much is dirty? The chart provides a snapshot. First off, you can see that coal generates about 49% of our electricity and gas chips in another 20%. That's the dirty part.

The other 31% comes from nuclear (19%), hydro (7%), renewables (2%) and some miscellaneous small generators (2%).That's the part that's already clean.

So we need to clean up about 69% of our generation capacity. How hard will that be?

Let's start with wind. There's 225 GW of windpower in the pipeline. I previously estimated this could displace about 37 percent of coal power. And just to provide some context: the giant wind farm that T. Boone Pickens has been flogging lately is a mere 4 GW.

How much solar power would it take to replace the 20% of US electricity powered by natural gas? About 311 GW of nameplate capacity would do the trick. Some more context: SolveClimate linked to a story yesterday about a proposal for the world's largest solar farm. It would produce 250 megawatts of power. We'll need 1,250 of those to replace the gas plants.

How much solar power to replace all the coal? About 761 GW. Gulp. These are big numbers.

Baseload and Storage

Now let’s deal with the problem that wind and solar can't be used for base load power exactly like coal, and can't be started and stopped on cue like gas generation to fill the demand in peak hours.

Estimates are that we can have up to 20% of our electricity generated by intermittent sources, and maybe we can stretch it to 30%, and still have a reliable grid. But at 30%, we’ve replaced less than half our target of 69% of the total. Still, it’s a good start.

To use more than that, we’ll have to solve the energy storage problem. Solar thermal has been designed to store some energy after the sun goes down. That solves the diurnal solar problem, so a solar plant can generate through the day and several hours after sunset during the hours of peak use. That does not solve the problem of a cloudy day. The best sites for solar plants don’t have a lot cloudy days, but there isn’t anywhere that has none.

Likewise, the wind blows when it wants to, which might be at peak hours but more often is at night. Again, where the wind prospects are best, power supply is more consistent, but not good enough to be the reliable source of base power like coal.

We could get around the intermittent solar and wind generation if we had an effective way to store the electricity. Then we could make juice when conditions were right and use it when we needed it.

The problem is that storing several days or a week’s worth of energy will dramatically reduce the efficiency and increase the cost of renewable energy. The electrical energy has to be converted to some other form of energy, stored, then converted from the stored form back to electricity again. Each conversion to a different form of energy is less than 100% efficient and so some energy is lost, usually a lot.

Each conversion will also require more equipment such as a utility scale electric generator, which costs real money. Batteries don’t require conversion to a different form of energy, but batteries that could store several days of energy are impractical today. The cheapest energy storage alternatives are pumped-hydro and compressed air stored in underground caverns or abandoned mines. They might be part of the solution, but there are limited sites of a useful scale.

Transmission

One last problem with solar and wind power: the best prospects are in the sunny Southwestern deserts and the windy Great Plains. Since most of the demand is east of the Mississippi and on the West Coast, we are going to need some new transmission lines. These aren't cheap and they take a long time to build: a 240 mile project in Indiana will take 6 years and a billion dollars. Some of these would be needed anyway, like the three billion dollar line proposed in Florida that I talked about earlier, but these projects have to compete with any new ones we need for financing, steel and crews.

Distributed generation can eliminate the need for some transmission lines, but by definition, the generation is not at an optimal location so efficiency is going to be lower and costs higher. Still, windfarms are in the works in many states and solar panels are showing up on a lot of rooftops.

Don't forget to include some extra power for growth: the U.S. demand has been growing at 1-2% annually. Efficiency programs can take a huge bite out of that and even retire a lot of coal plants, but there's another source of growth that we'd all like to see: electric cars.

We could handle about 20% of the US fleet going electric without adding new generation because they could recharge during non-peak hours. That profile might actually fit in well with wind power. Other projections are that if all US cars go electric, we'd need to add 20% to our electric generation, so tack on another 300 GW or so of solar and wind.

Bottom line: a laudable goal, but we need a plan.

Note: If you want to dig in to numbers that produced the pie chart, attached below is a spreadsheet.

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