Currently coal power and nuclear power compete directly. No one is deciding whether to build a hydro or nuclear plant, a set of windmills or a nuclear plant, or a natural gas or nuclear power plant. Well, the last is possible, but do that a few times and the price of natural gas really rises. Coal and nuclear are used all day, every day. Natural gas is more expensive, so it is more often used during days or times of days when extra power is needed.
GHG emissions from coal range from 0.97 kg to 1.3 kg CO2e*/kWh, let’s call it 1 kg (2.2 pounds/kWh). Nuclear power ranges from 9 to 21 grams/kWh, let’s call that 0. How many nuclear power plants are needed to reduce ultimate atmospheric levels of greenhouse gases by 1 part per million (ppm*)?
If there is feedback (warming soils releasing carbon dioxide and methane, plants growing in dryer soils and warmer oceans holding less GHG), then GHG we add today will produce more tomorrow. But for now, let’s assume no feedback. Then 2.1 billion metric tonnes (Gt) Ce corresponds to 1 ppm Ce. Pouring 2.1 GtCe into the atmosphere raises GHG concentrations by 1 ppm. At this point, we count every ppm not added, as it reduces the amount of damage we do the Earth. And ourselves.
Let’s assume our nuclear power plant is 1,000 MW. Assuming that the plant lasts 60 years, and has a 90% capacity factor (it’s down 10% of the time for refueling and repair, 90% is average capacity factor on current plants). Then the plant will produce
1,000 x 10(6) W * 24 hours/day * 365 day/year * 60 years * 90% = 526 billion kWh.
Each kWh from coal puts 1 kg of CO2e into the atmosphere. We’ll multiply this by 12/44 to get the added weight in kg Ce. Use 1 (metric) tonne = 1,000 kg.
526 billion kWh * 1 kg CO2e/kWh * 12/44 = 140 million tonnes Ce.
To convert to ppm:
2.1 billion tonnes Ce/(140 million tonnes Ce/plant) = 14,600 MW in nuclear power.
Nuclear power plants are larger than 1,000 MW, a large one might be 1,700 MW — about 8.5 of the largest plants will lower GHG concentration by 1 ppm.
If we start 15,000 MW in nuclear power every year for the next 20 years, these power plants will reduce ultimate atmospheric GHG concentrations by more than 20 ppm. If these take an average of 4 – 5 years to build, 60 GW (60,000 MW) – 75 GW will be under construction every year.
To put this in perspective
We all agree that nuclear power is being built at a snail’s pace today: 23 GW is under construction.
In the late 1970s and early 80s, 150 GW was under construction. This was the peak of the earlier construction period, when plant construction was much slower than it would be today. Not only were new designs being worked out, but a new regulatory system as well. Add in a few nuisance lawsuits here and there. Nevertheless, the construction rate was 4 – 5 times what it would need to be to reduce GHG concentrations by 20 ppm through projects started over the next 20 years.
Perhaps in 25 years it will become obvious that solar, etc will be able to supply electricity needs soon, and no more nuclear power plants need be built. But it’s not obvious today. What is clear is that building nuclear power plants decrease atmospheric GHG concentrations.**
Nuclear
Pressurized water model
and Solar
today
Typical system
and tomorrow
Flexible Solar Cell
* Parts per million — out of every million molecules in the atmosphere, how many are CO2 or CO2e?
Greenhouse gas concentrations or emissions are often measured in CO2e or Ce, equivalent to the values if all the change were to come from CO2 or C.
** CA is adding billions of dollars in subsidies to federal subsidies to build (hopefully) 3 GW, in solar photovoltaic panels. What GHG reduction will they achieve?
Assume GHG emissions for solar are comparable to nuclear (they aren’t, PV is energy intensive to build, but energy costs are coming down). Assume as well that PV panels last 30 years and that the capacity factor for CA is 20% (night, clouds, and changing position of the sun reduce average electricity production to about 20% of theoretical).
Then if solar replaces coal, how much will our subsidies here in CA reduce GHG emissions?
3 x 10(9) W * 24 hours/day * 365 day/year * 30 years * 20% = 158 billion kWh.
158 billion kWh * 1 kg CO2e/kWh * 12/44 = 43 million tonnes Ce.
43 million tonnes Ce/2.1 billion tonnes/ppm Ce = 0.02 ppm Ce
This investment in solar power is critical to reducing electricity costs in the future, and assuring a portfolio of low-GHG sources of electricity. But it will be a while before solar, etc, will be sufficient to meet the need for low-GHG emitting sources of energy.
Great way to analyze it Karen. but it is just as easy to put it this way.
How many coal plants of 1000 mw and oil refineries need to be replaced by solar, wind, water, and biogas and cionservation like geothermal heating/cooling and plugin cars every year over the next 20 years to reduce the GHG level the same amount as in your example?
Hidden at the very start is the wrong assumption that renewables can’t replace coal. Buy the false premise and you are lead down the garden path to the false conclusion.
It’s the old false diemna fallacy again. The favorite talking point pro-nuclear. Eith GHG disaster or nuclear power.
Karen,
Your calculation is a real eye-opener, I appreciate your insight. If you do the calc on an annualized basis (instead of one nuclear plant for 60 years) its gives an idea of the shear magnitude of the problem. Thus restating the question, how many nuclear plants are required to avoid 1 ppm Ce/yr? I estimate 900, or twice the number installed world wide.
The Princeton Wedge Theory has very aggressive allotments for ALL non-carbon sources, including conservation. I get a little tired of people expressing a preference for their favorite wedge, and critiquing others. Build them ALL, including (and especially) nuclear.
Thanx, Bill
Karen,
Very interesting point of view, but I noticed one thing missing in your argument. You said that nuclear produces only a couple of grams of CO2 per kWh and then you assumed this to be zero because it’s so small. This part is fine, but you didn’t mention anything about the mining, and transport associated with the nuclear fuel and then emissions associated the transport and storage of the waste by-product. But then again you’d have to add in the mining and transportation of the coal to the plant as well to make things even.
Cheers,
Scott
Scott, it’s a good point you raise. Not everyone may pay attention to it.
Since fossil fuel plants require 100,000 to a million times as much fuel as does nuclear, getting the fuel has major greenhouse gas costs. For solar and wind, the fuel is not a problem, but the diffuseness of the energy source means that there are greater construction costs. Also, the windmill/solar panel doesn’t last nearly as long as does a nuclear power plant. But because GHG costs are so low, most people just call them zero for nuclear power, wind, and solar.
For GHG costs, visit How Do Life-Cycle Greenhouse Gas Emissions of Electricity Sources Compare?
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