Friday, July 3, 2015

Is It Feasible to Replace Coal With Solar?

With recent developments on the climate change-fighting front, I had to ask myself if it was feasible to replace all of the coal-fired power plants in the U.S. and replace them with solar cells. Could this be done and stay realistic? To answer that question I began to crunch some numbers.

According to the Energy Information Agency, coal was used to generate 1.58 million thousand megawatt hours of electricity in 2013. These plants had a combined total nominal capacity of about 340 gigawatts. The cost of solar cells is dropping rapidly and is approaching $1 per watt installed capacity. That means it would cost $340 billion to install enough solar cell arrays to replace all of the coal-fired power plants in the U.S. (approximately 1500 power plants). 

Yes, that is a doable number.

But, what about area? Surely, that many solar arrays would take up a lot of land. 
Using a figure of .556 m2 per 180 watts ofcapacity, we would need about 1 billion square meters of arrays. That is about 400 square miles. Including space between arrays and room to operate, let's say it roughly 1000 square miles. Using a standard measure of area, that is less than the area of Rhode Island (1200 square miles). To put it another way, it would be a square 32 miles on each side.

Again, this is certainly feasible - especially considering the total area of the coal fired power plants would be available for conversion. 

What about operating expenses?

The average cost to operate a coal-fire power plant is around $7 per megawatt hour = $11 billion per year (using the 1.58 million thousand megawatt hours figure quoted above). Total operating expenses for solar = $0.

Once again, solar compares very favorably.

What about public safety?

Coal is the number one source of mercury in the air and water; the number one source of arsenic in the air and water; the number one source of sulfur dioxide which causes acid rain; the number one manmade source of radioactive particles in the air (coal is usually radioactive); the number one manmade source  particulate matter in the air (leading to a whole host of health problems); and, oh yeah, the number one source of carbon dioxide emissions causing manmade global warming.

Solar? No emissions.

Solar certainly comes out a head on that one.

In summary, even using rough numbers, we find the cost of replacing coal-fire power plants with solar power is reasonable; the land requirements are minimal; the operating expenses are much lower for solar; and the health benefits from getting rid of coal-fired plants are enormous. In short, it is very feasible to replace all coal-fired power plants with solar cells in even the short-term.

So, why aren't we?


  1. OK... so the 2 issues I always hear in terms of why large scale solar isn't feasible are:

    1) Rare earth elements required to build the panels.
    2) Energy storage issues (batteries etc) for when the sun isn't shining.

    Just wondering if you could address those issues.
    Thanks & love your blog!

  2. Thanks for reading.

    Solar cells used to use a host of the rare-earth elements, but not so much anymore. One significant one tellurium. However, new technologies have pretty much replaced the rare-earth elements in solar cells and we continue to make progress in that respect. Ironically, this came about when China, which produces most rare-earths, tried to control the market. Faced with climbing prices and potential shortfalls, researchers were motivated to find alternatives.

    The energy storage issue is still a question. The easiest large-scale answer to that problem is the same one we use for peak-demand problems - natural gas-powered plants. Natural gas plants can ramp up very quickly when demand exceeds what is available from other sources. Yes, they still have greenhouse gas emissions, but they don't have all the host of other problems associated with coal (mercury, uranium, arsenic, sulfur dioxide, etc.) and they are much cheaper than coal. In fact, the number of coal-fired plants has been on decline in this country for several years because they are being replaced with gas-fired plants. Eventually, the issue of energy storage will become more affordable. Until then, we can use other power plants at night.