www.ted.com

I just learned about this site. They have an amazing amount of videos of some pretty smart people.



I am in love.

There have been TED talks linked here before.

I agree though, it's a great website-- I've loved it for a long time.

TED talks are completely awesome.

_________________

agree, TED rox

For Fribs:

http://www.ted.com/talks/ken_robinson_s ... ivity.html

Being a music teacher, I'm sure you can appreciate what this guy has to say. Upshot is he's pretty damn funny.

Here is an idea worth spreading. (Cause I'm sick of people saying it takes more energy to make a solar cell than it produces.)

Make a solar panel factory powered by a large solar farm...

Sick or not, it's true. Not that it's necessarily a bad thing. It just limits the technology's capability to take a large role in commercial power generation.

Ideas like this we should keep an eye on: http://www.mererhetoric.com/archives/11275723.html

Agreed. Any technology that recovers power as we use it is worth a look.

Er, source? Because every life cycle analysis I've read puts the energy payback of silicon and CdTe PV systems between 1 and 4 years depending on the tech and where system boundaries are drawn.

Sources:
http://www.clca.columbia.edu/papers/Pho ... _Times.pdf
Also see:
M. Raugei, S. Bargiglia and S. Ulgiatia. Life cycle assessment and energy pay-back time of advanced photovoltaic modules: CdTe and CIS compared to poly-Si. Energy 32 (8) 2007, pp. 1310-1318.

Studies conducted by the US Department of Energy and Sandia National Lab.

The study linked appears to not account for production waste and manufacture of raw materials. I'm guessing this because it doesn't include fluorine or bromine compounds. In fact I don't see any etchants listed there. If you start from the grown wafer of course you cut out a lot of the cost. Unfortunately nature does not provide those for us.

Over the life span of a solar panel it produces 5 times the energy that was used to produce it. People just don't want to hear the life span is 40 years. Economics and peoples patience suck when it comes to human evolution.

Current solar technology produces ~2.5 times the energy used to manufacture the cell within a frame of around six years. Which is great when its sitting right on your house. It's not as simple when we're talking about using it to provide power via a solar plant.

The problem with the studies I've read is they haven't addressed manufacturing waste because "it's the same as any other chip", they do not account for infrastructure costs, and they assume all you have to do is clean the panel to maintain it. Panels degrade logarithmically starting at ~0.5% a year.

Some will last longer than others, but one really can't say it lasts 40 years when its power output drops by half or more over that period. It will have to be replaced, or supplimented during its life cycle.

This myth started because it's true when you talk about space craft solar panels. But in those instances, spend more energy is worth it because you have many more factors you are worried about other than efficiency. (Volume, weight, durability)

According to this study done 9 years ago the average solar panel gets five times more energy out than was originally put in. Roughly the same energy balance as gasoline.

What people see is $$ and the initial cost. Which can be brought down significantly with bootstrapping the industry with capital and resources. Much like the highway projects of the 30s. (Can't imagine anyone denying the benefits of them now.)



So low output in later years is an excuse not to still use them? You need to be at 80+% output to make them useful? If they are degrading logrithmicly your later years should be pretty steady even if much lower..... Hell send them back to my fictional solar poweredsolar panel factory in the desert for reduced cost new ones and it will connect them to it's grid.

Forgot link. http://www.solarbus.org/documents/pvpayback.pdf

Space solar panels are a special case, and almost a different technology. They aren't what drives the 'myth'. There's more behind the assertion than a look at a single panel. It's a power plant that is using them, to supply our domestic grid. Anything I've seen to date suggests that you're better off using a solar heat exchanger than a solar cell for that purpose. Fewer batteries required.

Realistically, silicon is not the way to go anyway but that's another issue. It's a technology for individuals at this point. Beyond that it would make more sense to invest infrastructure to it when multijunction cells mature.

You need to maintain a steady output because the people whose homes are connected to the grid the panel supplies expect their lights to come on when they flick the switch. And they also want it cheap. And yes, I think a power company would want to replace a panel when it hits 80% efficiency. That is a lot of loss in the scale we're talking about.

From the DOE's Solar Energy Technologies Program (http://apps1.eere.energy.gov/solar/cfm/ ... ations#Q69):

From the DOE's National Renewable Energy Laboratory (http://www.nrel.gov/docs/fy99osti/24619.pdf):

Another LCA (peer reviewed) done for the Solar 2000 Conference (http://www.ecotopia.com/apollo2/knapp/PVEPBTPaper.pdf):

Still interested in a link to the study you're talking about. I searched around Sandia's site but didn't find anything that looked like what you're referring to.

I was listening to a program on NPR just a few days ago about solar, and they were saying that even in the last 2 years solar technology has moved forward in cost efficencies a great deal. In fact, it was pointed out that if solar energy was given the same amount of tax subsidies and rebates as the coal / oil / nuclear industries, it would easily be able to compete on a cost basis.

Since we've had these threads before over the years, and the "it takes too much energy to produce solar energy" argument has been made before, I am wondering if those of you making it have updated your information, or are still basing it on information you found 5 years ago.

It was in a conference I attended (I think in 2006), if I can find it I'll see if it's postable. If not, well, I'm not going to go digging. Same conference was briefing their solar furnace power plant technique that is being tested/built out West. Basically they were speaking to the viability of x, y, and z technology power plants. IEEE also has a few decent sources.

And again, there's a lot more than just the module that you have to factor in to the cost. It takes a lot of equipment to condition solar energy for use in our grid. Those studies are great for rating individual use. Things like RVs, boats, water heaters, etc.. Silicon is more geared toward individual use anyway. A ~2000 kWh/m2 footprint is not viable to supply a population with electricity. The urban area around Baltimore consumes ~1.25 billion kWh in one year. Need the emerging, more efficient, technologies for that.

Short version:

Individual use = good (if price point is low enough)
Power grid use = not quite there yet beyond small scale

I'm basing it on research, though admittedly I work more with multijunction cells than silicon. I'm not aware of any trade studies yet but there's probably one on thin films floating around somewhere.

It could compete with subsidies, but short term those subsidies should go to taxpayers installing the cells at home. I don't see how they could compete on a cost basis when they'd need a 10+ square km array to match the plant's output (with silicon). Land costs money too, and roof space is free and mostly unused.

Your comments actually cooincide with the program I heard, for the most part. The focus there was also on individual use as the primary way to use it, on already existing rooftops.

Apparently (according to it), Walmart is considering putting solar panels on the top of their rooftops-- with the size of both the rooftops and the company itself, it seems to me that this would be a good thing.