Geothermal
MIT has just produced a multi-hundred page book, The Future of Geothermal Energy (in the US), focusing on EGS, enhanced (or engineered) geothermal systems.
Some 50 GW in coal plants will need to be retired (and may be!) in the next 15 – 25 years. (Coal plants produce about 5/6 as much energy/GW as do nuclear plants.)
Their findings:
Geothermal energy from EGS represents a large, indigenous resource that can provide base-load electric power and heat at a level that can have a major impact on the United States, while incurring minimal environmental impacts. With a reasonable investment in R&D, EGS could provide 100 GWe or more of cost-competitive generating capacity in the next 50 years.This achievement could provide performance verification at a commercial scale within a 10- to 15-year period nationwide.
Note: if geothermal power is ramped up to 100 GW over 50 years, it will supply 1/2 wedge — just in the US!
Most US resources are in the West, though the Great Plains and South also have resources. Resource data are scarce for Hawaii and Alaska, but there is optimism about Alaska. Electricity prices are also higher there; in rural areas, it is provided by diesel generators.
Cost data are limited, and future costs are speculative. That said, costs appear to drop below 5 ¢/kWh once capacity is somewhat over 100 MW, and begins to rise again at 1,000 MW (=1 GW), dropping with learning and rising as more expensive resources are exploited. At 100 GW, cost/kWh would be over 7 ¢. Of course, R&D and initial government financing are critical.
Nuclear
A number of estimates exist, more or less in the same ballpark. I will use MIT’s report, The Future of Nuclear Power.
If no changes are made in how US nuclear power plants are built, the base cost will be 6.7¢/kWh, for plants with a 40 year lifetime, 85% capacity factor (fueling plus maintenance 15% of the time), and 5-year construction time. (Actual capacity factor is 90%, which brings the cost down 0.4¢/kWh if that remains true in new plants. After 40 years, costs will presumably go below 2¢/kWh, as they have for today’s plants.)
The cost could be as low as 4.4¢/kWh if capital costs can be cut 1/4, construction time drops to 4 years, and the costs of capital drop to that charged for coal and natural gas plants. Hopefully any optimism about how to lower costs is compensated for by pessimism about capacity factor and lifetime.
Advanced Boiling Water Reactor — 4 are now being built in Japan and Taiwan.
Fossil fuels
I am not providing cost estimates for coal or natural gas power. Natural gas emits carbon dioxide and empowers Russia and the Middle East, another cost. Coal power today emits about twice as much carbon dioxide/kWh and both both coal mining and pollution kill lots of people. Carbon capture and storage is much more expensive than nuclear power, emits 10 – 20% as much GHG as coal does today (so it’s better than natural gas today), but is an important option for countries that insist on using coal power.
