V3Solar, another stupid idea January 30, 2013Posted by Maury Markowitz in solar.
The nerdy portions of the interwebs were all alight with the news that someone had figured out how to lower the cost of solar power to below that of coal. The company, V3Solar, claims to have invented a new way to dramatically simplify concentrated solar power, a thorny problem that many companies as great as Boeing have failed to solve. And through this miraculous invention, solar will be only 8 cents a kWh!
A little background
Solar panels start with a bunch of solar cells wired together, glued to a plate of glass, and then covered on the back with a plastic sheet. Then they put an aluminum frame around the glass. The closest analog you have is a window. There’s really not much to them.
The biggest cost of the panel is the solar cells within them, and that’s largely dominated by the wholesale cost of polysilicon, pSi, the main ingredient. If you reduce the amount of pSi in your panel, you reduce the price of the panel. That’s why you see things like Twin Creeks trying to figure out how to make the cells way thinner.
Concentrated solar power
There is another way to get more panel for the buck, and that’s to use less panel.
Generally about 1000 Watts of sunlight falls on every square meter of ground. About half of that is in the infrared, which we don’t really have a good way to harvest. Of the 50% that’s visible light, we can turn about 30% of it into power, so that’s pretty great overall.
But no one said I had to cover that entire square meter with cells. Consider taking a normal panel and pointing it to the sun. Now take a mirror that’s the same size as the panel and use it to bounce sunlight onto the panel. Now the panel is getting twice as much sunlight, and twice as much energy, but it still has the same amount of cells.
This is the whole idea behind concentrated solar power, or CSP. Actually in this case we’re talking about a specific example of CSP, concentrated photovoltaics, or CPV. Simply put – you collect a light from a really big area using something cheap, and shine it onto a small area of the expensive bits. That’s instead of building more of the expensive bits and covering the same area. The number you want to know is the concentration ratio, the amount of total collection area to the area of the active parts.
Here, let’s look at a picture from the V3 web site (click it if it’s too small):
So what they’re saying is that if you take 1 square meter of flat panel it will cost you $100 (about right), but if you instead use 1 square meter of lens and 1/20th a meter of of cell, the overall cost of the system is way lower, five times less. And in theory, it is…
So here’s the problem, the Earth turns. In the image above you can imagine the sun directly above the lens, so the light is focused down onto the cell. But wait even a few seconds and the sun is no longer directly above the cell, it’s a little bit to the west of it, so the light is now focused on a point just to the east of the cell. And now your cell isn’t making any power.
Now one way you could attack this problem is to move the cell a little to the east, under the new focus point. This works for a while, but if you’ve ever played with a magnifying glass and the sun, you’ll recall that the focal point is no longer circular, it’s oval. As the angle between the lens and the sun increases so does the size of the oval. Eventually most of the light is no longer hitting the cell no matter where you move it.
The only solution is to rotate the lens and the cell as a single unit, keeping it perpendicular to the sun. So now we’re looking at a complex system of mountings and moving parts. Suddenly it’s not so attractive is it?
And here’s the catch-22… the economics of concentration improve as the concentration ratio goes up. But when it goes up, the accuracy of the focusing has to improve the same amount in order to keep the light on the cell. So you save money on the cells, but you increase the cost of the tracking system.
Back in 2007 I was on a call with the makers of a cell designed specifically for use in CPV systems. It started off well enough, with them quoting cell cell prices about $1 a Watt, in an era when conventional panels were about three times that. But then I asked how much the tracker was… $7 a Watt. You could hear the pain in his voice when he admitted this.
And this is why there are no CPV systems being used commercially.
V3Solar was previously known as Solarphasec. Back then they were pushing a solar “panel” that was formed in a cone:
According to them at that time;
The proprietary electromechanical function of the system increases the efficiency of the photovoltaic cells deployed in the system leading to significantly higher output power compared to an equivalent footprint of a standard solar panel.
What’s this “proprietary electromechanical function”? Well supposedly they convert the DC power from the cells directly into AC. They did this by spinning the cone. That’s right, spinning it.
No details were given, but reading between the lines I suspect the idea was that the cells closest to the sun would provide more power than those on the other side. So if you track the amount of power coming out of one cell as it rotates around the circle, it peaks then drops to a minimum then builds back up to a peak again. Sine-like, although there’s definitely going to be electronics involved anyway.
And how much better would this be? Well modern inverters operate with average efficiencies between 90 and 96%. So even if Solarphasec’s concept was 100% efficient, the cone would only produce a few percent more power. So basically, complete bogosity.
But who cares about details? It’s the bottom line we’re talking about. And wow, look at this bottom line:
The 17 Kilowatt Power pole serves as an art form with the ability to produce 17,000 watts in a 3 square meter footprint
Please tell me you see this is utter BS. Remember, 1000 Watts of power falls on every square meter of the planet. That means 3,000 watts falls on 3 square meters. Now their design extends upward, but if you look at it there’s maybe, maybe, 5 square meters and the vast majority of it is empty space.
And they say they’re making 17,000 Watts from that area.
Let me put this as bluntly as I can: this is impossible. Not difficult, impossible.
So it seems that they couldn’t convince too many people of their miraculous claims, so they gave up.
Wait, that’s in the alternate reality where people aren’t trying to scam everyone. On this planet what they did is change their name, tweaked the sales brochure, and relaunched looking for financing. And here’s the new version:
Looks a lot like the old version, but with a cover on it. And that’s exactly what it is. Except in this version, those ridges on the outside of that cover are lenses that magnify the light under them. So suddenly it’s a concentrating system.
And now we’re not spinning it for some sort of super power conversion magic voodoo, apparently that “proprietary electromechanical function” isn’t worth mentioning any more. No, now we’re spinning it because when you concentrate the light the cells heat up, which is bad. So spinning them out of the sunlight cools them down again.
Awesome. Awesome to the max.
Remember that concentration ratio is the amount of total collector surface compared to total cell surface, so if you have one panel and one mirror, that’s 2 times concentration.
Ok, now look at that image again… am I wrong, or is the ratio of collector surface to cell surface 1 to 1? No, I’m not wrong. There is no concentration going on.
Now admittedly, those little “lens ruts” on the surface do indeed increase the amount of sunlight directly below them. But they do that by lowering the amount of sunlight on either side. That’s what lenses do.
Ever looked at the bottom of a pool in bright sunlight? Notice the bright spots where the ripples on the surface as focussing the light? Notice the dark spots around them? It’s simply geometry.
Now wait, the idea here is to only “use” the cells that are under the lens, and sure, those ones will be seeing concentrated sunlight. Sure, but that’s at the cost of turning all the other cells off.
Look at the first image in this article again, they’ve taken 1 square meter of lens (say) and focussed it down onto 20 cm of cells. Great.
Then they fill the rest of the square meter with cells that do nothing.
Yeah, that’ll make it cheap.
Arg! This is such BS it makes me mad just thinking about just how much BS it is!
To back up their claims, V3 hired a freelancer to write up a technical review. Note that the “technical” review doesn’t include a single formula. This should worry everyone. In fact there’s very little in the way of support for their claims, mostly just some hand-waving that might get you a few percent here and there. But then there’s this statement:
Although normally one sun cells are not fully optimal for higher concentrations, current test data on the V3Solar Spin Cell shows 20X greater current production and an additional 20% higher voltage under 20X concentration during the dynamic spin.
Now just look at the statement: he’s saying that 20x more light results in 20x more current. Wow, STOP THE PRESSES! And this 20% increase in voltage is explained in magical terms that even he admits, right in the article, might not exist.
All of this magical power conversion is supposed to add up to a lower cost of the installed system. It’s all enclosed in a single package, so you just stick it on a pole and you’re done. I can actually see how that would indeed save costs.
But how do they manage that? By doing all that work during the manufacturing cycle instead. They make the concentrator, they make the spinny parts, they put their “inverter” into the same box. And then they sell the whole thing for 59 cents a watt.
Let me express my scepticism. Just look at it, do you really think a “panel” that spins rapidly on top of a lamp post and lasts 20 years is something you can build cheaply?
Bridge for sale, cheap
There’s been any number of similarly weird solar power proposals over the years. My favourite was the solar roadways concept that hoped to replace the world’s pavement with plastic sheets with solar cells on them. Hmmm, driving on plastic sheets, that’s gotta be fun in the snow!
So here’s my prediction: V3Solar consists of a web page. It will in the future too.