How Many Wedges Do We Need? — pt. 2/2

Socolow-Pacala analyses for different wedges, with some caveats.

Decarbonizing Power (Electricity)
One wedge could be supplied by 700 GW of new nuclear plants with a 90% capacity factor (plus replacing others as they reach the 60 year or so limit on use). This would triple installed capacity (so that the use of nuclear power would rise a little faster than the production of electricity in general). Assuming that the new nuclear power plants are an equal mix of EPR (1.6 GW), ESBWR (1.5 GW), and AP 1000 (1.15 GW), about 10 – 11 new nuclear power plants would be needed per year (plus replacement plants) to achieve this. For comparison, Kansas is planning to build coal plants totaling 2.1 GW, and Texas is considering coal plants totaling 9 GW. [Either the figures for nuclear power are too high or those for wind and solar are too low. If the renewables numbers are valid, then new construction would be closer to 650 GW, or 13 GW/year.]

To get one wedge from wind power, assuming 26% capacity factor (actually 20% in Germany, 27% in US, this will go down if wind power expands to less windy areas), 2400 GW in new wind power must be installed over 50 years, 3100 GW if Germany’s experience is more valid, more if the shift into less windy areas is needed, even more to compensate for the use of inefficient natural gas power plants to even out wind power with a compressed air energy storage system. [I’ve corrected their analysis – either their figures for nuclear power are too high, or their figures for wind and solar are too low.] Windmills erected today are expected to last 20 – 30 years. Unless this improves a lot soon, windmills will need to be built even more rapidly. The current installed wind power is 60 GW, so as much wind power, more or less, needs to be added (plus replacements) each year for the next 50 years, if wind is to supply one wedge.

Wind Farm
Wind Farm Wind power requires hydroelectric or, more commonly, natural gas, backup — most days, wind is considerably below 27% average capacity in the US, 20% average capacity in Germany.

Photovoltaic (solar) power (PV) is assumed to have a 26% capacity factor, higher than estimates for new PV in the US Southwest. For areas of the world further from the equator, such as Europe, the capacity factor will surely be lower. [Again, the analysis includes a mismatch between assumptions for nuclear power and solar.] Current US capacity factor for PV is 19%; assuming that this increases to 30% over 5 decades, then a world average of perhaps 25%? makes sense. Energy payback times are 2 – 5 years, so electricity production must be increased to shift to PV’s. Or to put it differently, with a payback time of 3 years, a PV system lasting 30 years produces only 90% of the electricity apparently produced (from the IEA book, Renewables for Power Generation- Status & Prospects). For one wedge, 2500 GW of PV (lifetime about 30 years) must be installed, more than 2700 GW if energy payback times are counted. The addition (doesn’t count replacement) of PV would average 5 GW/year. The addition will need to equal about 6 times total current installed capacity, or 1.7 times estimated installed capacity for 2010. These numbers look impossible; however, there is considerable optimism about the ability to add solar power, especially at low latitudes. The California Million Solar Roofs Initiative subsidizes PV installation, with a goal of 3 GW by 2017, and anticipates an increase in capacity factor from 18% to 20%. (pdf) Note that installing 3 GW over 12 years is considerably less than the 9 GW of coal power Texas wants to build today. Coal power plants have a capacity factor of 75%, so produce about 4 times as much electricity per installed capacity as does PV. Nuclear has a capacity factor of 90%, so nuclear produces about 5 times the amount of electricity per installed capacity as PV.

PV panels
PV Panels Compare the price of electricity from photovoltaic panels at the site to the retail price of electricity. PV doesn’t have to reach wholesale prices to be cost-effective.

Fuels can be decarbonized using ethanol as it’s made today (ugh), though this method won’t work for airplanes — ethanol energy/volume ratios too low (maybe it’s OK for shorter trips?). Some newer ideas — such as plug-in hybrids – highly fuel-efficient hybrids powered by nuclear power and fueled by cellulosic ethanol – are not even examined.

How Many Wedges Can We Reject?
Given current assumptions on reducing GHG emissions (and next year’s assumptions are not likely to be more optimistic), it seems foolish to reject any wedge. If calculations are incorrect, if solar improvements are slower than expected, or wind more problematic, if there are changes in climate that reduce the effectiveness of installed PV or wind systems, if increased carbon dioxide levels in the atmosphere and changes in the climate reduce the productivity of crops for biofuels, if desalination becomes an important and heretofore uncounted demand on electricity systems, if the necessary rate of GHG emissions reduction is determined to be faster than currently predicted, the costs of optimism could be catastrophic.

Arguments that we should reject any of these wedges usually fall into two categories. The first is that, just in case climate scientists are overly pessimistic, perhaps we should go slow. After all, there will be costs to change. Most analyses show that erring on the side of more GHG reductions is likely to be cheaper.

The second argument is, not nuclear. To be convincing, the anti-nuclear people should demonstrate that nuclear power is really bad, on the same level as climate change, or direct deaths from using coal or natural gas, and that solutions can exclude coal, natural gas, and nuclear with plenty of room for error.

There are other issues besides climate change. Solutions that depend disproportionately on natural gas make American hunters unhappy and give disproportionate economic and political power to Russia and the Middle East. Shifting to nuclear powered plug-in hybrids more rather than less rapidly will decrease the power of oil producers. Fossil fuels pollute and are dangerous to workers and the environment.

Not sure how the energy sources compare in terms of health and the environment? Take a quiz to test your knowledge.

One Response to “How Many Wedges Do We Need? — pt. 2/2”

  1. Steve Bloom says:

    (Reposted from part 1)

    Fresh from GRL:

    Kempton, Willett; Archer, Cristina L.; Dhanju, Amardeep; Garvine, Richard W.; Jacobson, Mark Z.
    Large CO[2] reductions via offshore wind power matched to inherent storage in energy end-uses
    Geophys. Res. Lett., Vol. 34, No. 2, L02817