How big of a solar farm would you need to power the entire world with renewable energy? That’s a question addressed recently on Quora, the website that specializes in providing in depth, well researched answers to important questions. Actually, the original question was quite different. The discussion started this way. “Could the world feasibly switch to all-nuclear power generation? If so, would that be a good counter to global warming?” For an answer, Quora turned to Mehran Moalem, PhD, a professor at UC Berkeley and expert on nuclear materials and the nuclear fuel cycle.
Professor Moalem began with this brief biographical information. “I have taught courses in nuclear engineering and a few seminar courses in alternative energies. I also worked for two years starting up six solar factories around the globe. In spite of my personal like for nuclear engineering, I have to admit it is hard to argue for it. Here is the simplified math behind it.”
Moalem then calculated that the world uses approximately 17.3 terawatts of continuous power each year. Sounds like a lot, doesn’t it? Actually it is. But, he says, a solar farm just 43,000 miles square would produce just about that amount of power. Moalem says the Sahara Desert covers 3.6 million square miles. If you’re into math, that means covering just 1.2% of the Sahara with solar power could provide the entire world with all its electrical needs.
It turns out the Sahara is also an ideal site for solar power. Because it is on the Equator, it receives 12 hours of sunlight virtually every day of the year. Also because of its location, that sunlight tends to shine directly down, meaning solar panels located there can be two to three times more efficient than those located in higher latitudes, like Europe and North America.
Moalem puts the price of such a system at $5 trillion dollars. Wow! That’s a lot of money, right? Actually, no it’s not, the professors says. Its less than the US spent to bail out banks 8 years ago. It’s about 10% of world GDP. The cost of building a nuclear power plant with a similar capacity would be more than 10 times as much.
He points out that this is a one time cost. Once such a facility gets built, the energy it produces is free. There are no ongoing costs for fuel, no generators to spin, to boilers to make steam. Moalen thinks that’s a pretty cheap price for something that could replace every other power source on earth, especially those that spew deadly pollution into the air.
Even though he is nuclear power engineer, Moalem says nuclear is not the way to meet world energy needs. One important reason is that a nuclear power plant gives off twice as much energy by way of waste heat than it generates. The environment — whether the atmosphere, oceans, or rivers — would be unable to absorb that much extra heat without drastic climatic consequences.
What does Moalem see as the future of energy? Solar. “There is no future in other energy forms. In 20 to 30 years solar, will replace everything. There will still be need for liquid fuels but likely it will be hydrogen produced by the electrolysis of water and that powered by solar. Then tankers and pipelines will haul that hydrogen around the world. One can also envision zirconium or titanium batteries that store large quantities of hydrogen.”
A hydrogen economy would require an abundance of excess energy to split water into hydrogen and oxygen. With solar, Moalem expects there would be enough excess energy to make the dream of clean hydrogen power possible.
Others are contemplating ways of meeting the world’s future energy needs. A consortium of Chinese, Russian, and South Korean partners is planning an ultrahigh voltage supergrid that would take electrical energy generated from renewable sources and distribute it to the world’s population centers. The group specifically mentions North Africa — home to the Sahara Desert — as one of the areas best suited to producing renewable energy. The Sahara has one other significant advantage. The land is some of the least expensive to acquire available anywhere in the world.
One potential concern is that Moalem’s projections do not take into account population growth and the increasing demand for energy as under-served areas of the world gain access to reliable electrical power for the first time. Not to worry. Doubling the output of solar energy from the Sahara would only require using 2.5% of the available land area.
The dream of abundant zero emissions energy can come true. It just means thinking on a grander scale than normal. Reducing carbon emissions will not be enough to avoid the consequences of climate change. Eliminating them will be needed wherever possible. Shutting down all the world’s fossil fuel generating plants would be a good start. It’s possible, given the will to do so. Mehran Moalem just proved it.
