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Instead of using expensive PV cells, the solar telescope uses commercially available triple-junction solar cells

In fact, triple-junction cells are far more expensive than garden-variety PV cells. The cost savings come from the fact that sunlight is concentrated onto a much smaller area of cells. And this is hardly the first company that has applied that idea; for example, see Energy Innovations, Inc.

Roger Angel has designed a new type of solar concentrator that uses half the area of solar (PV) cells used by other optical devices and delivers a light output/concentration that is over 1000 times more concentrated before it even hits the cells.

If the light is concentrated over 1000 times, wouldn't the the device require less than 1/1000 the area of solar cells, relative to a solar panel that lacked a concentrator?

http://www.energyinnovations.com/sunflower250.html is the two-axis concentrator. It's a bit worrying that the website appears unchanged since 2006 and commercial trials were supposed to start in 2007. But supposedly Google's going with their subsidiary for a 1.6MW system.

Under Technology their web site describes all the approaches they considered and reluctantly abandoned. Very interesting read.

Energy Innovations has tried Fresnel and is working on mechanically steered 5x5 set of mirrors.

Your box sounds promising but a grid of them requires an elaborate supporting frame? The Energy Innovations Sunflower 250 lies flat on the roof. Your water heat collector adds expense.

Energy Innovations has tried Fresnel and is working on mechanically steered 5x5 set of mirrors.

Your box sounds promising but a grid of them requires an elaborate supporting frame? The Energy Innovations Sunflower 250 lies flat on the roof. Your water heat collector adds expense.

why haven't I seen yet a combined system

Because it doesn't make sense economically. Yes, a combined system would save on roof space and mounting equipment, and would waste less of the sunlight striking it. But solar is so expensive that only millionaires can afford to cover their entire roof with solar heat or electricity, and combined systems cost even more.

I have both solar PV (nine BP panels) and solar heating (european tubes filled with glycol) on my roof, I'm waiting for approvals and final plumbing. The two systems are installed by different trades with different mounting frames and different hookups to your house.

The Holy Grail for all solar energy systems is to be cheap and efficient enough that any company or homeowner with some spare cash and roof space installs or adds on to one. It would be amazing if a combined heat and electric system reached that point, but I think dedicated systems will get there first. A solar electric system using a concentrator has to deal with overheating, so maybe it'll prove economical to do something useful with the waste heat.

Read all the Energy Innovations Technology pages for insights into the difficulties of making a concentrator system reach that Holy Grail, including a Stirling engine design

Is this at all related to what Energy Innovations has been doing?

build the fucking array of photo cells and then reroute to energy straight to the heart of Vegas. You know how fucking expensive it is to run an air-conditioner during the summer.

Have you even flown over Vegas and noticed that the roofs of most of the buildings and casinos are BLACK?? I mean, wtf are they thinking??

Perhaps one day the roofs will be covered with these.

Energy Innovations has a device called the Sunflower that uses a similar concept of focusing the sun's energy for heating purposes... on a sterling engine! They use it to generate electricity. They're also working on a newer model which, IIRC, is about 4 feet by 6 feet in a rectangular array (easier to orrient the mirrors, they said).

Energy Innovations has a device called the Sunflower that uses a similar concept of focusing the sun's energy for heating purposes... on a sterling engine! They use it to generate electricity. They're also working on a newer model which, IIRC, is about 4 feet by 6 feet in a rectangular array (easier to orrient the mirrors, they said).

I just can't wait until they get into mass production, because the metric they seem to be using throws out traditional physical efficiency and relies on power per unit cost rather than conversion efficiencies.

It's also been implemented on a much larger scale in molten salt power towers which iirc use high temp (200-500C) salt to make steam to turn turbines. Yes, it's a solar plant that can work at night if it has to.

-Holmes.

I just can't wait until they get into mass production, because the metric they seem to be using throws out traditional physical efficiency and relies on power per unit cost rather than conversion efficiencies.

It's also been implemented on a much larger scale in molten salt power towers which iirc use high temp (200-500C) salt to make steam to turn turbines. Yes, it's a solar plant that can work at night if it has to.

-Holmes.

> The thing I can't help but wonder, is why if these are so effecient, is why there isn't one under the hood?

Well, you still need heat to run it. Internal combustion engines have become very clean and the issues with manufacturing them are very well understood, too. And to the best of my knowledge, noone has ever built stirling engines of significant size at production quantities. Even if you made it gasoline powered (using the same infrastructure we currently have) you'd have to prove it was reliable to get any consumer buy-in. It would take some serious resources for an existing, successful company to do it.

It looks like the company that was talking about this has backed off of the technology for now, although it does say they're still working on the idea.

The author's daughter, Marcia Goodstein is CEO of Idealab. One of the companies they've invested in is Energy Innovations, which is trying to develop a solar energy system.

I bet they won't produce as much power as solar cells for the same area of sunlight.

But that doesn't matter. There is no shortage of sunlight; the problem is the expense of collecting it. This makes the most important metric $/W instead of W/m^2, and cutting $/W is the worthiest goal for the widest variety of uses. To that end, Energy Innovations came up with the idea of a small multi-mirror concentrator system feeding a Stirling cycle generator. 200 watts for $200, or $1/peak watt. The last I heard they had put the Stirling engine on the back burner due to development costs and were going to market with a concentrating photovoltaic system instead. We're going to have to wait, I guess (or license their patents).

Wind: Nonviable (kills birds, not cost efficient.)

Solar: Nonviable (cost of production exceeds energy consumed, massive chemical waste byproducts)

Coal and gas: Viable (unless you believe in global warming, which most "greens" do)

Conservation: Nonscalable. Cut your energy consumption by 50%? Sure. But 50% of O(N^x, where x &gt 1) is still going to present you with unacceptable constraints on growth.

My question is, what fuel do we go to?

That said, there are a lot of places where other sources of energy could fit in if we designed our systems flexibly enough to accomodate them. For instance, cheap concentrating solar could supply energy to hybrid cars on an as-available basis, cutting emissions of CO2 and all related pollutants in the bargain. You don't need to get fancy when simple will do; doubling efficiency and substituting for half of the remaining demand yields a 75% reduction, and those figures are definitely within reach with stuff we could make today. That's just one of many things that are feasible right now.

Why can't we buy this stuff off the shelf? Inertia and politics, I guess.

A bit more nasty than you let on.

I read that as saying that what's not left in the machine is typically brought out in recyclable form; you can distill condensed vapors and re-use them, and molecular beam technology can boost utilization if it matters that much. I can't see that you refuted anything I said.

I can't find the exact quote by I believe it is from Zubrin talking about the latest 18-20% eff Solar cells and how they cost more to manufacture in energy than they will ever produce.

1 watt * 6 hours sun/day average * .8 derating factor * 365 days/year * 15 years = 26 kilowatt-hours. That's the energy equivalent of about 2/3 of a gallon of gasoline, or 3.3 gallons of gas if you consider the typical conversion efficiency of small to medium size engines. I find it doubtful that you could spend even a dollar on energy to make a cell that retails for four dollars, plus I've read that the payback time for the best panels these days is only a couple of years. I'll take better data when I can get it, but right now I don't think that the bleeding-edge economics applies to the stuff a consumer would buy.

Of course, not all solar is PV (see this, they updated their site), and wind pays back very quickly in any kind of decent site.

Some of the stories about cheap flexible solar arrays being made soon are promising but until there are demonstrateable enviromental and economic advantages over nuclear power I am reluctant to consider them a panacea and more of a hinderance to the energy crisis.

I've got nothing against nuclear, but its improvements are going to be incremental. Wind isn't bad, but barring tricks like gyromills it is going to move incrementally too. PV, photochemical, and other things are still improving on an exponential curve; those are the ones to watch.

Actually....

If you are going to use trick mirrors, it looks like the best way is to use a Stirling Engine to convert the solar energy to electricity. One example is Stirling Energy Systems but Discover just ran an article about the sunflower prototype from Energy Innovations that plans to break the magic $1/watt barrier. The sunflower uses reflective plastic petals to focus light onto a Stirling engine which generates electricity. This approach gets around some of the worst characteristics of PV cells such as sensitivity to the angle of light, high cost of material manufacturing, and upper limits on how much light can be converted.

But woudln't you just have to expend the energy to make the panels once? And, don't forget, there are other ways of capturing solar energy that copst as little as $1/Watt.

There are better ways to handle this. I Recently read in a Discover or Popular Science about Energy Innovation's producuts, such as the Sun Flower 250. They are basically thermal-solar-powered Sterling engines used to generate electricity. Their newest and most economical model costs $1/watt to purchase the actual unit, and that's it.

You could just stick one of these babies under a plastic (or whatever) shell to physically protect it from the elements while allowing the energy in to do the work.

So, let's not stop at photovoltaics when it comes to solar power.

One company, Energy Innovations, has an interesting new approach using a Stirling engine and solar mirrors.

UNLV has similar solar-power rigs at the far northern edge of campus. This page has more info, and some pictures...they're two different designs from different companies and can supply up to about 50 kW for the pair. Some solar A/C info and other stuff is further down the page as well.

Conversions of solar power to electricity through photovoltaic cells is quite expensive.
One company, Energy Innovations, has an interesting new approach using a Stirling engine and solar mirrors. This could prove to be a cheap way to bring solar energy directly to your home. As long as certain engineers don't start getting mysteriously shot in the head that is.

Discover Magazine just did a story on something like this. Unfortunately the full story is only available in dead tree format. If you wait until next month the older article will be available. You can probably check it out at your Dentist's office like I did if you feel like getting a filling.

EnergyInovations is working on a small version. From the Discover article it discusses how they refined the stirling engine with the best tradeoffs of manufacturing costs to effiency. IIRC they are also making this small enough to make it fit on a roof top.

Geek fact of the day: A stirling engine is an external combustion engine that runs off the pressure created when one side of its engine gets very hot while the other side stays cool. The greater the temperature difference, the greater the pressure, the greater the energy generated.

Discover Magazine just did a story on something like this. Unfortunately the full story is only available in dead tree format. If you wait until next month the older article will be available. You can probably check it out at your Dentist's office like I did if you feel like getting a filling.

EnergyInovations is working on a small version. From the Discover article it discusses how they refined the stirling engine with the best tradeoffs of manufacturing costs to effiency. IIRC they are also making this small enough to make it fit on a roof top.

Geek fact of the day: A stirling engine is an external combustion engine that runs off the pressure created when one side of its engine gets very hot while the other side stays cool. The greater the temperature difference, the greater the pressure, the greater the energy generated.