The current administration has articulated a goal of an 80% reduction U.S. carbon emissions by 2050. The first thing to keep in mind as one considers this lofty goal is that electricity production consumes 40% of our primary energy resources in the U.S. and produces 40% of the CO2 emissions. The remaining 60% of our primary energy consumption and CO2 emissions originate in the transportation, industrial process heat, and non-electrical building heating sectors. (According to their 2007 energy analysis, LLNL analysts estimate the transportation sector is directly responsible for 33% of our total CO2 emissions.) So... achieving this goal will require rapid transformation of BOTH the electricity and transportation sectors.
Sometime ago, I created a simple Excel spreadsheet model of U.S. electric energy consumption and carbon emissions. I decided to use this simple model to explore the magnitude of the electricity sector actions required to achieve the 80% reduction goal.
The simple model I built employs a first-order approach to estimating time-dependent energy consumption and carbon production based on the market share of a specific generation in the first and last years of the analysis, the carbon intensity of each energy production type, the population growth rate, and the per capita electricity consumption per U.S. citizen. The model interpolates in a linear manner from the starting year to the ending year of the analysis, and provides year-by-year estimates of electric energy production by type, carbon emissions by type, and the required installed electrical production capacity to deliver these results. Not rocket science, and subject to several approximations - but certainly good enough to provide some high-level insights.
Now for some basics... Several sources indicate the average American consumes approximately 14,000 kWh of electricity each year. This value varies a bit as a result of economic conditions (it apparently has been somewhat lower this year). Future improvements in energy efficiently might drive this per capita consumption down, but it's a reasonable number for our estimates.
The U.S. Census Bureau predicts our 2008 population to be ~ 304,000,000, and our population growth rate to by 0.6% per annum for the foreseeable future. Based on this data, one can predict total electricity consumption grows by 14% by 2030, and 29% by 2050. [At this point I note that this is where we can harness the "law of large numbers". Even small improvements in energy efficiency and personal energy conservation can have very large payoffs. Thus investments in energy conservation and efficiency should be high on everyone's list of things to do... But conservation will only take you so far...]
I assumed the carbon intensity of various energy production types to be constant at:
Coal: 0.96 kgCO2/kWh
Natural Gas: 0.60 kgCO2/kWh
Wind, Solar, Nuclear: 0.00 kgCO2/kWh.
With this as background, let's examine a few simple questions:
1. What is the impact in 2050 if the current U.S. generation mix (~ 51% coal, 21% nuclear, 17% gas, 6% hydro, 1% wind, and the remaining 4% solar, geothermal, etc.) is maintained? The answer is simple. Since the generation mix doesn't change, the total CO2 from electricity production grows by 29% by 2050. Remember the 80% reduction goal...
2. What electrical energy production mix is required to achieve the 80% reduction in CO2 emissions by 2050? (Remember this would still leave the 60% CO2 emission fraction from transportation and industrial process heat sectors untouched, so we would still fail the 80% overall reduction test miserably...) According to my model, we could achieve this by transitioning to 60% nuclear, 15% natural gas, 10% wind, 10% solar, while maintaining the current market shares of hydro, geothermal and oil, and eliminating all coal-fired generation. Remember - this is energy production. In terms of installed capacity (assuming 92% nuclear availability, 30% wind availability, and 40% solar availability) this translates to ~ 410 GWe installed nuclear capacity, 211 GWe installed wind generation capacity, 158 GWe of solar capacity. That's a factor of 4 expansion over our current nuclear capacity, a factor of 50 expansion in our current solar capacity, and a factor of 10 increase in our current wind generation capacity. That's 400 1-GWe nuclear plants; 211,000 2-MWe wind turbines, and I haven't taken the time to calculate the acres of solar panels.
3. Can we completely de-carbonize electricity production? Yes. According to my model, we could go with ~ 65% nuclear 15% wind, 15% solar, IF we can maintain the current hydro energy split - an unlikely possibility. Or, we could go 80% nuclear, 10% wind, and 4% solar - if we maintain the current hydro production fraction.
What's the "so what?"
Here's my summary observations:
- We really need a focus on energy conservation and energy efficiency improvements. Harness the law of large numbers. Probably still much low-hanging fruit there.
- If we totally decarbonize electricity production, we still miserably fail in achieving the 80% overall CO2 emissions reduction target unless we also transform the transportation and industrial energy use sectors
- A breakthrough in carbon sequestration would be really nice. Otherwise it's difficult to see a future for coal-fired electricity production in an era of carbon taxes, and the demand for deployment of other energy forms is dramatically increased.
- A massive uptick in the deployment of nuclear, wind, and solar energy is required. ALL THREE are needed. There's no silver bullet.
Again, all this based on a simple analysis of the fundamentals. No rocket science (but maybe a Nobel ? )
Got to run. Be especially safe during the next few days. An astonishing percentage of the folks you meet on the road during the next 72 hours will be intoxicated. Take extra precautions.