The major problem is not the unreliable timing of wind and sun. The major problem is that renewable energy sources are so diffuse. David MacKay made this point in an excellent free book I recommended to WanderingEng: Sustainable Energy – Without the Hot Air. Some time ago I complained privately to b_b about a comment observing that a square solar panel 100 miles on a side could power the U.S. It wasn't meant as a feasible proposal, but it didn't sound utterly unfeasible either, and a math error in a followup comment reduced the area needed by 99%. I told b_b that we don't even have a 10,000 square mile patch of empty land in Nevada. The feasibility challenges are formidable, even in the empty Sahara. How do you rinse dust off the panels, in the desert? How do you maintain the installation, when would take hours just to drive past it? MacKay is supportive of renewables, but he is insistent on making the numbers add up. I got the impression that photovoltaic panels will not practical for more than a small fraction of consumption anytime soon.Author Sarah Zielinski discusses the major problem with solar and wind-generated electricity: relying on it puts you at the mercy of weather and daylight.
To make a difference, renewable facilities have to be country-sized.
Figure 25.5. The celebrated little square. This map shows a square of size 600 km by 600 km in Africa, and another in Saudi Arabia, Jordan, and Iraq. Concentrating solar power facilities completely filling one such square would provide enough power to give 1 billion people the average European’s consumption of 125 kWh/d. The area of one square is the same as the area of Germany, and 16 times the area of Wales. Within each big square is a smaller 145 km by 145 km square showing the area required in the Sahara – one Wales – to supply all British power consumption.
The comment you complained privately about was mine. And since you're still snarking about it, let's run the numbers: US energy consumption, 2013: 25,451TWh. Let's crack that down into hours, rather than spreading it across the year and we're at 2.9 terawatts constant capacity. Average solar energy per square foot, 2015: 13.8W What we wanna use for daylight? They've got about 10 hours right now, and it's a couple months past solstice. Six months from now they've got 14 hours. Let's put the duty cycle at half a day. That puts a solar panel at 7 watts per square foot. Cracking it down to square miles to get rid of some of the decimality (2.8e7 feet per square mile; 1,000,000 watts per megawatt) and we're at 27.88 megawatts per square mile. 2.9 terawatts/27.88 megawatts = 10,401 square miles. There's some dickering in there - solar panels weren't quite as efficient in 1995 but power usage wasn't quite as high. By the way: the Nevada Test & Training Range is 4500 square miles. This is land that we use to drop explosives on, primarily, and it's not quite halfway to your disingenuous square. I read Mackay's book, by the way. Or part of it, anyway. He's condescending. And my flippant comment was exactly that - flippant. No one is advocating dropping ten thousand square miles of solar panels in the middle of Nevada ("How do you rinse dust off the panels, in the desert? "). The whole point of the argument is that yes, typo, 200 square miles of solar panels feeds a state. And yes. 200 square miles of solar panels is a bajillion dollars. And yes. there are probably better ways to do sustainable energy. And yes. There are formidable challenges. But snarking about it instructs no one. And snarking about it behind my back is cowardly.
I think our energy needs can be more robust going forward with a mixture of sources. So long as there's natural gas in the ground, we'll burn it. But we'd be in a stronger position if gas was supplemented by large amounts of solar and wind, as system and price stability is greater when diversity is high, I believe. I know if I were building a house from scratch, I'd definitely have solar panels on it. Unfortunately, the gable on my roof isn't well suited for them, as my hose was built back when not even Jimmy Carter was considering solar. I still think that delivery is a bigger problem than production. Solar on a rooftop is convenient, because you don't have to worry about transmission lines. Even if we could block a 10,000 sq mi tract in NV, we couldn't deliver the energy to NY, because line resistance is too high right now. Someday, someone is going to become a billionaire many times over by inventing a high temp super conductor (remember Airbus's electric plane that's predicated on a high temp super conductor, lol?). That would be a game changer, if it's not a fantasy.
In my opinion, photovoltaics haven't crawled up Moore's Law to the point where they make sense for individual investment. SolarCity is arbitraging renewable energy law to externalize the cost of solar ownership to the government which, really, is worth doing. The grid's a mess and has been. HVDC may clean up some of it but local power production is a better solution. Frankly, energy efficiency is the solution.
I would have preferred to respond in public earlier, but was muted at the time. Thank you for including me in this conversation. You take issue with my tone, and with MacKay's. I take issue with using the words "very little land" and "tiny" to describe the space requirements of solar. But physics, not sentiments, will decide whether solar is viable. So I enthusiastically support running the numbers. MacKay gives a peak solar energy of 1000 W per square meter, over 90 W per square foot. So we can hope that the 7 watts of today's panels will continue improving. Seven watts per square foot gives 195 MW per square mile. So 2.9 terawatts / 195 megawatts per square mile = 14,871 square miles. How big is that? It depends on what you compare it to. I find it disingenuous to compare it to the continental United States. A test range is also simply a shape drawn on a map. A solar installation would be an engineering megaproject; we should compare it to other engineering megaprojects. Small towns are mere dots on the Nevada map, the Hoover Dam is invisible. The floor space of the Pentagon is a fraction of a square mile. Fresh Kills landfill is four square miles. No one thinks Elon Musk actually wants to build a solar facility the size of New Jersey in the desert. But he is definitely advocating when he characterizes solar as realistic for more than a small portion of our energy needs. If he wants to spend his own money on energy innovation, I salute him, but he is clearly willing to spend other people's money.
I'm starting to remember why. Here's crescent dunes. It's 1700 acres of mirrors, 2.6 square miles, in the middle of thousands of square miles of nothing. It's good for 500 GWh and cost about a billion dollars. 500GWh is a long road from 25,000 TWh. We'd need 50,000 of them to meet our yearly power requirements. That's a 50 trillion dollar investment. Nobody thinks we're going to do that. Nobody thinks we're going to build a photovoltaic array a hundred miles on a side, either. Not you, not me, not Bob Mackay. Not anyone who has ever so much as paid $12 for a Radio Shack solar panel capable of generating half a watt. Those of us who have worked on solar-electric hybrids have a pretty firm grasp on the disappointments of solar. But 25 thousand TERAWATTS is a staggering number. It's Doc Brown's "Two point twenty one jigawatts!" with four more zeroes. It's the kind of math that makes you lose hope. Hundred miles on a side? You can wrap your head around that. You'll never build it - it's 3,000 times the size of that very-impressive heliostat out in the middle of the Nevada desert. But fuckin' A, we can build a few. And at the cost of the Iraq War, we could have built 1700 of them for a power generation of 850TWh. STILL a long goddamn way from 25 thousand terawatts but you know what? It's a percentage. It's a start. And it's in human numbers, broken down to size that people who haven't read Bob Mackay can understand. And that's my beef - I threw out a flippant comment to make a point that renewable energy is within the realm of contemplation. You're going to the mattresses to argue that people aren't allowed to be flippant because you read a book. "How big is that?" About as big as I said. Is it "simply a shape drawn on a map?" Fuck yes. Because without drawing a shape on a map it's all a bunch of fuzzy numbers. How fuzzy? Well, according to MIT there is more surface area of the United States covered by parking spaces than there is covered by Puerto Rico - 3500 square miles in fact. Fuck Nevada - let's put a panel on top of every garage and cut our energy needs in half. And now we're back to your buddy Elon and realistic goals and nobody even had to call anybody else an asshole.I would have preferred to respond in public earlier, but was muted at the time.
We agree on this. And I think we agree that drawing a square on a map can help people wrap their heads around what that number represents. When I draw the square, I say "Golly! I have to zoom in three clicks before I can see the speck that is the Hoover Dam. Maybe solar is not yet ready for prime time, even if we could overcome the storage and transmission challenges." When Elon Musk draws the square, he says "actually very little land is needed to get rid of all fossil fuel electricity generation in the United States" and his map has the title "Surface area of solar panels required to power entire U.S." He would make a Dyson sphere look small by drawing it next to the Milky Way. Elon Musk is a visionary, a dreamer, and a savvy marketer. Attracting investment is his game, and he does it well. If his reality distortion field gets private investors to sign up, and the result is cool luxury cars and awesome rockets and better solar power, I am all for it. When he dips into the same public funds that brought us Solyndra and Fisker, I have reservations. I want to see reality as it is. The numbers show that, for now, the words "solar" and "power entire U.S." should not appear in the same sentence. There is a niche for solar. Pilot projects are useful. More research and development is warranted. I didn't interpret your flippant comment as a serious policy proposal. But the "tiny" typo gives the reader the wrong idea, I think. b_b appears to have anticipated that readers would conclude that "it's such a small area." Renewable energy takes a staggeringly large amount of area. 100% solar would require about as much as there is paved road in the lower 48. Hmm. If "more worthwhile than war" is the standard, then sure, we should build giant pyramids covered in solar panels. If "making responsible use of resources" is the standard, then I don't see solar contributing more than 1% of consumption anytime soon.25 thousand TERAWATTS is a staggering number.
Elon Musk expresses a similar view of what constitutes a small amount of land.