Photovoltaics Get Extreme Makeover

Industrial Equipment News ^ | 11/07/2008 | Debbie Maskin

[Right Wing Assault]

I still think this is an elegant and simple design. Think about how much material goes into a traditional parabolic reflector and the support arm(s) for the PV receiver.

P.S. Yes, it is an interesting designs, but I would like to see a large scale demo. NOT on farmland, though. We already saw what happened when we ran our cars on food.

[SC Swamp Fox]

Yes, that statement is lame. I hate it when the marketing guys feel the need to “pump up” the claims like that.

[Publius6961]

The usual neglected reality will shoot this one down too.
Efficiency plummets with even the thinnest layer of dust. The bigger the area becomes, the more unmanageable and expensive it is to keep the units clean.

But somebody will get rich from the usual taxpayer subsidy!

Free?
Ha!

[Publius6961]

Believe it or not, I have a calculator that uses them...

*chuckle*

Anything under a couple hundred square feet is very feasible, but...
Running a boat and running even a small cabin are different animals entirely.

I expect a bit more reality when the dope consumption goes down.

[Reeses]

It might be possible to make this into a solar powered hot air balloon.

[saganite]

now if his coating could only be made cost effective....

Yep, there was no mention of how well this might translate into production. Still just a lab experiment at this point but it seems to have a lot going for it.

[Attention Surplus Disorder]

Thanks! My understanding is that PV cells are roughly 20% efficient at peak output. With that amount of concentration, it’s not hard to imagine that fluid cooling would be needed, and probably a good deal of it could be done convectively; using no external power source, or perhaps by siphoning off some of the PV cell’s output to run a small motor. I’d also imagine the focus of the sunlight wouldn’t need to be so razor sharp, so maybe the heat would be reduced that way.

Digging up an old article I saw on FR: “What this article misses is just how many watts can be captured with how much cell surface area based upon the intensity and wavelength of the incident energy. As always the maximimum solar flux incident tangent to the earth is 1367 W/m^2. 70% is relected back into space. This leaves about 900 W/m^2. But this spread across the spectrum. Even at the high eficiencies this only leaves about 300W/m^2. And this is when the sun is directly shining on the panels with no angle from tangent. So at 37 degrees north where I live, I can expect maximum on a clear winter day is about 100 w/m^2. So in the winter with a 30% efficient cell I will need 10 m^2 of cells. Someone at the equator in winter will need maybe 3 m^2”

So, an 8 ft diam “pod” as illustrated could theoretically produce about 6 x 300 = 1.8 kilowatts at the equator, a considerable (but not bombastic) amount of power. At off-latitude, probably 1/3rd that, assuming again, 30% cell efficiency which AFAIK is highish. Over a 24 hour duty cycle this probably translates into 100-200 watts which isn’t too exciting.

The energy “hill” is unquestionably a tough one to climb.

[SC Swamp Fox]

What is the output of a solar array when the sun goes down at night?

When is the daily peak electrical demand?

I not advocating solar as the solution, but we shouldn't discount it just because it can't supply all of our needs all of the time. Photovoltaic cells have already proven themselves useful particularly in remote locations that do not have access to the grid. If technology continues to advance and costs continue to decline photovoltaic generation could soon find use on the grid, particularly down south where the peak demand is usually in the afternoon and on the hottest, sunniest days of the year.

[Kevmo]

bmflr

[SC Swamp Fox]

Thanks for the numbers.

I don't believe it will be cost effective to disconnect from the grid anytime soon. In my mind the batteries currently pose a larger problem then the PV cells, but neither are ready for prime-time.

I think that the progression will be towards grid-connected PV installations. For example:
I install 10 of these PV collection pods on the south side of my barn. During the day when electrical demand is the highest my PV cells are providing power to the grid. (My wife and I are at work, my kids are in school.) At night we draw power from the grid. If I sized my PV farm right we provide more then we use and the utility puts a credit on my account. I'll need that credit when February rolls around and it's cloudy for weeks.

Unlike wind, solar has the advantage that it's output will be highest when it's needed most: hot, sunny days.

They cracked the 40% mark about two years ago. I'm not sure where they are now.

[OneWingedShark]

>It gets dark there at night, too. What is the output of a solar array when the sun goes down at night? Give you a hint, the word for the number begins with a “z”.

That’s true. But by that logic solar energy is useless at all points on the earth’s surface because of a 1:1 light/dark ratio which is cyclic in nature.

However, given that huge chunks of the populous is diurnal, the peak energy drains will be during the day.

Further, photo-voltaic is different from our power-system in one significant way, it produces DC whereas the grid is in AC. (So, an inverter must be used, and that will of necessity reduce the overall power-efficiency of the system.)

I’m not saying that it’s the ultimate solution, but it makes a WHOLE lot more sense to use solar in NM or AZ than say... London or Washington.

[truthguy]

Never say never... If solar energy ever gets cheap enough the next problem will be energy storage and that's changing rapidly as well. You need enough energy storage to cover the worst case expected sun outages. Also by placing solar production over a wide area you greatly increase the chances of the sun shining in one or more of those places. The key remains costs. If the costs are low enough one can afford to build many redundant systems

Can you tell me how to store electrical energy? We don't even have batteries that can store enough energy to run a small car. Maybe in the next two years or so there will be batteries that will begin to be used in a car. See Chevy Volt. But there are no means that exist today that will allow you to store electrical energy in mass. If you know of any then let me know. There are not many places that it makes sense to put solar panels outside of the southwest. Yes states like Arizona, New Mexico, etc have a lot of sun but remember that you are still looking at about getting effective sunlight about 25% of the time on the best of days. Solar is completely unpractical for the Northeast, Mid-West, Pacific Northwest, Eastern Seaboard, etc. Those areas do not get enough Sun and they are very heavily wooded. When you transmit power over long distances there is a substantial amount of energy loss. I don't have time to explain this. You will have to research it yourself. Anyway WE Will NEVER get more than 8-10% of our energy from solar and wind. The only reason we have solar and wind power today is because the government is subsidizing it. Take away the money provided by the tax payers, all solar and wind power development will stop overnight. Again Rube Goldberg!

[HawaiianGecko]

I looked into solar when I built this home a couple of years ago.  Building solar  for peak usage is the problem.  I use an average of 6,400,000 watts of electrical power per month or 8,767 watts per hour.  Now this doesn't sound unreasonable especially at $1 per watt but it's not anywhere near my peak value.  You get to triple that 8.7K value to start with because on Dec 20th, you only have about 1/3 the hours in a day of daylight.  There's another multiple thanks to the sun's position in the southern sky of about 2.  I have three tank-less water heaters that are 220V, 150amp devices each or 33,000 watts times three if they are all cranking at the same time, and believe me, the kids all sleep until the last possible moment, and all get in the showers at the same time so from 7am to 7:20 am my meter is spinning at 99,000 watt-hrs of use.

All in all as I remember I needed to build a system that could peak at 115,000 watt-hrs and compared to the 6 cents per Kilowatt-hr that my electric company is charging me it would have taken around 150 years to pay itself back.

Humans have this inbred hope that miracles happen.  A watt of electrical power is as cheap today as it will ever be.  150 square miles of potato chip bags sounds cheap until God discovers it's location and starts throwing lightening and hail stones at it.

[truthguy]

Whatever turns you on. But I don’t want to pay for your solar panels through taxes.

[ProtectOurFreedom]

...what keeps the dirt off the clear surface? Another big clear bubble, of course. It’s another “simple and free solution”.

[SC Swamp Fox]

I don't want them subsidized by the gov't either.

I saw this article today and thought it was a pretty slick piece of engineering, I decided to post it. It's a shame that the company's marketing guys exaggerated the product's potential.

I won't be placing an order until someone can prove a reasonable ROI. Technological advancements and cost reductions like this one may make that possible in the near future.

[Attention Surplus Disorder]

I competely agree that a zillion independent installations connecting to the grid are not a very attractive model. Actually, I’ve generally thought that “off-grid” installations would offer the most promise: for the end user, not for “society”. But, I don’t have any such situation so I can’t speak from experience.

Reason I say that: If you could operate your barn and the (I assume, perhaps wrongly) fairly limited appliances within it from 12 or 24 VDC or 48 VDC as an “island”, then the whole thing becomes a lot simpler. Much like a RV, really, living life as a 12 VDC universe until such a time as the engine starts & recharges your batts, or, pull up to an AC outlet and recharge. Very simple setup. The disadvantages are: High wattage devices running from 12 V would require significantly larger conductors and various other components of higher ampacity.
Eg;
5 qty 100 watt bulbs = 500 watts @ 120 VAC = ~~4 amps = not that much current, could use 20 ga wire in air.
5 qty 100 watt bulbs = 500 watts @ 12 VDC = 40 amps, implying 10 ga wiring or better.

To convert the DC output of solar cells into AC requires a synchronous inverter, not just a vanilla inverter, because the output has to be in phase with the prevailing grid phase.

My view of the whole thing is that if you can avoid converting low voltage DC to high voltage AC and run your world from the solar cells, at the native voltage of your battery stack, life will be much simpler. True, you won’t be able to sell power back to your local utility, but I’d like to see the payback time for the synchronous inverter (vs vanill inverter or NO inverter) and extra circuitry divided by how much you’ll be credited by your local utility. The sync inverters I’ve seen are between $2.2K and $3.5K

http://www.sierrasolar.com/manufacturers.php?manufacturer_id=137

and I guess if you get a warm feeling with a 2-3 year payback at $2-3 a day, then have at it. Otherwise, it seems like a potentially fun but overengineered and probably not very cost effective exercise. Batteries, too, become a religious experience in large arays.

[SC Swamp Fox]

150 square miles of potato chip bags sounds cheap until God discovers it's location and starts throwing lightening and hail stones at it.

lol...very good.

I made similar calculations a couple of years ago and came to the same conclusion. However, I was planning for "above average" not for peak usage. If you stay on the grid you can sell excess power during the day and draw off the grid at night. It still didn't add-up, the break-even point was too far away and it was impossible to get an honest estimate on maintenance costs.

If cost reductions like this one continue it may not be too long before the math works.

[Titus-Maximus]

Solar and wind will only work when electricity can be stored efficiently, that day has not come. Research that and get that done before spending this money.

Every wind and PV solar installation needs a fossil fuel plant backing it up in case the weather changes and the renewable power stops. That is why T Boone Pickens has a stupid plan, thousands of MW’s of wind have to be backed up by the same MWs in natural gas power plants. Pickens owns nat gas so it all helps him, but it is devastating to the economy.

Gore owns a windmill company so I don’t trust him as far as I could throw him. He does not disclose the interest and therefore he is being dishonest as he ‘preaches’ global warming.

[ApplegateRanch]

How many KWH can these guys pump out on a treadmill?