Many insist that renewable energy can replace coal, gas, and/or nuclear plants. My first response to this declaration is to ask, by when? Next decade? Someday in the distant future?
Before answering those questions, please consider two sets of facts:
1. Coal (45%), gas (24%) and nuclear plants (20%) today provide 89% of America's electric power, with oil another 1%. Including large hydro, renewable energy provides 10% of our power. Nothing to sneeze at all but now just one-tenth of our total power. See March 19th Posting Key Power Production Facts About Coal, Natural Gas, Nuclear, and Renewables.
2. Also our power production or demand will probably increase about 10% by 2021. Power production escalated 20% since 1996. It declined from 2007 levels in 2008 and 2009. But power production increased in 2010 to 2007 levels. It is growing again.
So could renewables replace all of coal, gas and/or nuclear power within 10 years? Or 20 years? As sure as the sun comes up in the morning, the answer is: "no; renewables cannot replace the 90% of power now coming from coal, gas, and nuclear within 10 years or 20 years."
But renewable energy can do a lot and will. So here is a different question:
Can and will renewables increase from the current 10% of electric power supply to 20% in 10 years?
Renewables can and I think will provide 20% of our power in about 10 years. Why? Renewable energy normally has no fuel costs and capital costs are falling sharply, especially for solar but also wind.
Wind power costs are down, with capital costs $2,500 per kilowatt. Projects can be financed with power purchase agreements at an attractive 5.5 cents per kilowatt-hour.
Solar total costs (equipment plus installation) are down to $3.50 per watt for larger projects in Pennsylvania and are falling literally every month.
Attractive hydro opportunities exist around the country. Many more biogas projects are possible at landfills, sewer plants, and at farms. So growth for renewables will occur. But how much?
If renewable energy goes from 10% to 20% of all power provided in the United States in the next decade, it would have had an excellent decade. Achieving that goal would require a trippling of non-hydro renewables, going from 4% now to 12% of total supply. It would require too a renaissance in hydro.
A doubling of all renewable sources from 10% now to 20% a decade later would mean that renewable energy effectively met all of the load growth (10%) in the USA plus a bit more over the next decade. Approximately $600 billion over a decade or $60 billion per year of private investment would be required.
Even after a tremendous growth decade for renewable energy, 80% of electricity would be coming from a mix of coal, gas, and nuclear. Using less gas means more coal and/or nuclear. Less nuclear means more gas and/or coal. Less coal means more gas and/or nuclear. That also is our world for the next 10 years and longer.
Technology can and is changing that world but not at the speed of light.