Pliable Solar Cells on a Roll

klevin writes "New Scientist is running a story on someone else who's developed thin, flexible, photovoltaic cells: 'The thin and bendy solar panels can be stuck to fabrics, sheets or backpacks and promise a go-anywhere electricity supply.' Whatever happened to those sheets of solar cells that some university here in the US developed several years back? As I remember, the concept was that they could be draped across roof-tops and whatnot. Never heard anything after that." We had post about solar building clothing last year.

Comments

Flat vs. Flexible Info

[sahrss]

To address some of Klevin's confusion, since I've been following solar panel advancements:

Thin, flexible cells have been around for a while. One reason they haven't caught on heavily is because they're nowhere near as 'powerful' (efficient at conversion) as hard panels. Did a quick search (don't take this data *too* seriously, but it represents what's normal); compare panels from these two pages:
Flexible
Solid

Specifically, compare "Unisolar 32 watt flexible solar panel" from the first link to "Shell ST40 thin film CIS 40 watt solar panel" on the second. The flexible panel is 940 sq. inches and 32 watts, while the solid panel 663 sq. inches and 40 watts. Big difference in watt per area.

I ended up choosing a big solid one to fit in the rear dash of my car; flexible would have been easier to deal with, but it won't fold, and produces less power. (I use the panel in my car to power my laptop/cell phone combo while camping and stuff, it's very cool and gets a lot of questions from random interested people!)

Here's another chart to compare the two: Product Page
Tried to find an efficiency rating chart comparing the two types, but no luck. The numbers are out there somewhere...

Re:Flat vs. Flexible Info

[RealUlli]

You mean, like this?

Cheers, Ulli

Is $US52 per square metre about right?

[thorpie]

They quote 7% efficiency, 1 euro per watt.
Full sun is 1000 watts/sq metre, so with 7% efficiency we get 70 watts/square metre, so it has a cost of 70 euros/sq metre or, at 1.33 euros to the dollar, about $US52.60/sq metre.
Cover a 10 * 4 metre area of roof for $2,100 and get enough energy, in the middle of summer, to boil your 2 kw electic kettle all day.
At 12c per kwH for electricity, @ 2.8 kw * 6 hours/day * 365 days/year gives a cost saving of $735 pa, or a repayment of the $2,100 capital in 3 years

Are these numbers OK?

At this price will it be practical to disconnect from the grid sometime soon?

Re:Is $US52 per square metre about right?

[drphil]

Although there is nothing wrong with your calculation per se, there are a lot of costs it doesn't include, so it is low by quite a bit. The 1 euro per W (peak Watt or average W - article doesn't say) is only the cost for just the solar cell at high volume manufacturing. At that point you are still quite a long ways from installing this on your roof cost-wise. You still have to put the solar cell in a module, then install it in a panel, then install the panel on your roof along with a rectifier (since your house expects AC) plus other equipment and power storage if you want to be competely off-grid - there are costs, of course, each step of the way.

The rule of thumb I came across when I was studying the econ of solar cells ~18 months ago was that for thin film cell solar to be viable (without govt subsidy) it had to be manufactured for $1/pW (or one euro, depending on exchange rate) and had to have at least 10% efficiency. If the 10% efficiency is not met then the downstream costs eat you alive because you have to install so much more area of solar cells to get the required power.

The current advances in flexible solar have been excellent and the solar market is growing at ~30% (although still >90% c-Si cells), but unless you are willing pay a price to be "green" or your govt gives you a fat subsidy for installing the solar power it will take you many years to repay your capital - on the order of 10 or more if you currently have ready access to the power grid. If you are remote from the grid, solar is actually a great deal cheaper today - but by using Si-based solar which is manufactured on relatively large scale today and has 15% efficiencies versus thin film.

Govt subsidies are still going strong in Japan - Germany is wavering. With G(lobal) W(arming) Bush in office the increase in solar in the US is going to be from the Eco-minded willing to take a bath $$-wise or off grid applications - well, there are also cats who are pretty good at utilizing passive solar power.

Re:Electricity is only a small part of the game

[TheLoneCabbage]

Most solar researchers in this veign are using Sodium Cloride (table salt). It has a much higher specific heat than water. Tends to be less explosive when heated to 600c (you really want to build your house on top of an aging steam boiler with the equivalent energy of dynamite?), and is even cheaper than water and dirt (water aint cheap where I come from)! When molten it's conduction of heat is so efficient you don't even need pumps, it's own confection currents do the work for you.

Now you just need a near perfect insulator and your all set. (say an underground tank insulated with airogel)

The real trick isn't in just heating homes though. It's also running things like ovens and stoves. For that your going to need a liquid that stays a liquid between -10c and 250c, without dangerous pressure build up, freezing, corroding or screwing up your pumps. (and it can't pollute the environment when it leaks)

Once you can safely transport high temperatures 2-3 times boiling point, you can do some pretty amazing things. Like running your A/C from the heat well. (two sterling engines hooked up to eachoter in reverse) Water pumps, air tools, and electrical generators (40-50% efficient in sealed systems like sterlings, but much higher for open ended boilers. The trick as you put it is to avoid converting the energy from one form to another untill it's absolutly necesary.