The return on investment argument....

[Claire]

Originally Posted by Nocturn

....Claire, I am aware of those factors, they seem largely exagerated. It depends also on what kind of solar panels we are talking about. New thin film panels are manufactured like a printing process, with a conductive "paint" sprayed on a very thin film of metal. Doesn't take nearly the same amount of energy as multicrystalline panels.

Even with present day multicrystialline panels, the aluminium frame can be entirely recycled. I find it very hard to believe that a product with a lifespan of over 30 years just "barely" produces enough electricity to offset the energy needed to produce it. If you have some figures I'd be interested to see what they say

The data I'm going on was from a two day conference at the Royal Academy in London earlier this year, which was called "Energy... for the future". They were supposed to be putting the notes from the conference on their website but I couldn't find them unfortunately - it was IMO a really good discussion of the options. The figures on solar PV were given (rather reluctantly) by the guy that was talking on solar power and I think he was linked to a manufacturer - I'm not sure exactly what type of panels he was talking about though. The impact of making aluminium frames wasn't mentioned. I know there're lots of things in the pipeline but from what he was saying, nothing actually available at that point that to me was environmentally "worthwhile", never mind costs. Solar thermal apparently is a better bet but wasn't discussed.

[Nocturn]

I hope that data shows up somewhere (edit: is this the page? http://www.royalsoc.ac.uk/page.asp?id=4633&tip=1 ). The data I'm going by is this, from Teslamotors blog:

In a modern manufacturing plant, the energy needed to create a frameless PV module from semiconductor scrap material is estimated to be around 600 kWh/m2 for monocrystalline cells and 420 kWh/m2 for multicrystalline cells (source: www.nrel.gov). A big variable is how thin the silicon wafer can be sliced. For ultra-thin cells, like those from Sunpower, the energy to produce a module may be considerably lower.

Taking the monocrystalline example:
Solar incidence (US): 1825 kWh/m2/year
Module efficiency: 18% (Sunpower)
Energy lost in system: 20% (Due to inverter, wires, cell temperature, etc.)
Total energy produced:

263 kWh/m2/year
Energy to create module: 600 kWh/m2 (National Renewable Energy Lab.)
… to build aluminum frame: 80 kWh/m2 (from Alsema et al)
Total energy used:

680 kWh/m2


The above results in a payback period of roughly 2 and a half years. The NREL study similarly calculates the payback period for polycrystalline panels to be 3-5 years, and amorphous silicon panels to be 0.5-2 years. Given that most modules have a 25 year warranty and an expected useful life in excess of 30 years, this indicates about a ten to one advantage for energy generated versus consumed.

I tried finding info on solar incidence for the UK (in France for example it varies between less than 1220 and more than 1760). I found this map:

http://www.greenenergyworks.org.uk/solar.htm

Lets assume 1100kWh/m2/year.

Doing that calculation again, taking into account the new 22% efficient panels from SunPower (available in 2007):

Solar incidence (UK): 1100kWh/m2/year
Module efficiency: 22%
Energy lost in system: 20%

Total energy produced:

194kWh/m2/year

Payback period would be around 3.5 years.

Now, this isn't even taking into account the amount of pollutants you avoid putting into the atmosphere by not consuming electricity based on non renewable sources during those 3.5 years, let alone 30 years of producing electricity from solar panels.

So I don't understand how one set of numbers can show a payback period of 3 years, and another that shows it's only marginally better.

[Claire]

The energy payback time certainly looks better from those numbers. I assume this guy must have been talking about products that are already on the market and there's a big difference with the sunpower device - for one thing I don't believe he made any mention of using all semi-conductor scrap, which would be very significant. Could also be a big difference between theoretical maximums and what a typical installed device sees, perhaps? I couldn't see which was represented from a quick view of the map you use as a source. Finally I believe he was talking about total impact rather than energy usage, e.g. a total LCA score. Oh, and his lifetime suggestions were 20 years as I recall.

It's not a field I'm concentrating on so I won't be going searching for the data I'm afraid - I can remember my interpretation of what he said well enough to convince myself and am unfortunately not in a position to buy at the moment anyway. If you've sufficient enthusiasm, time etc. do try digging around at the RA though, you might have more success than I did.

[Aquaman]

I agree that it is a worthwhile investment. One I plan on making, I'm sure I'll save money, but I don't know if the power rates are going to continue at the same rate of change. There could be any number of factors for a jump that big, plant upgrades/ repairs/ retrofitting. I agree that it will increase, I just don't think it will be a linear growth.

[Richard]

Originally Posted by Nocturn

Total energy produced:

194kWh/m2/year

Payback period would be around 3.5 years.

Is that the energy consumed or the energy produced? If it's just energy produced then you have to assume that all that energy is been put to good use...what about times when demand is low? Is that energy lost or stored somewhere for later use?

[Nocturn]

Originally Posted by Richard

Is that the energy consumed or the energy produced? If it's just energy produced then you have to assume that all that energy is been put to good use...what about times when demand is low? Is that energy lost or stored somewhere for later use?

Well you could have a system that that gives your home whatever electricity it needs, and sells the rest to your power company. That way all the production will be used. With the laws passed in Germany and France, your house can actually earn you money while you do nothing, especially if you decide to sell all your electricity and buy it back from the power company, since the solar incentives allow you to sell it for a much higher price than what you buy it for.

[Claire]

Originally Posted by Nocturn

...(edit: is this the page? http://www.royalsoc.ac.uk/page.asp?id=4633&tip=1 ). ...

Yes! Thanks! Well found. It was Prof Michael Graetzel, second to last on the first day, I think, and as I recall the question of impact payback was raised in questions at the end of his presentation.

This is turning out to be a very interesting discussion. Thanks for starting it Nocturn. Oh, and another question occurred to me last night - are the printed panels available now? I had heard of that technology but didn't realise they'd gone commercial yet.

[Nocturn]

Yes, it was Michael Graetzels presentation I saw too. About the semi conductor scrap, he mentioned in his presentation:

"The silicon used in solar cells comes mostly from the waste in electronics industry".

Anyway, I think his presentation was mostly about a new type of solar panel that he is researching, and that they have about 11% efficiency, which is pretty low, below the 14% that most panels have now.

I've also seen plans for making much more efficient panels, >38%, for example this company just licensed technology from Berkeley to make such panels:

http://www.rosestreetlabs.com/RSL%20Energy.htm

Beside the massive improvement in efficiency, their panels don't use silicon, which is by far the most expensive component in current panels.

About the printed panels, there is a company called Nanosolar which next year will build the worlds largest solar cell factory in the world, their tech is thin film and very cost effective since the cells are made like a printing process. There are two videos on their site: http://www.nanosolar.com

All of these things have made me pretty enthusiastic about solar, yes
Especially after seeing Prof Pete Edwards presentation on hydrogen. It made very little sense to me, especially for transportation. Why would you first waste electricity to make hydrogen (electrolysis 70% efficient), then compressing the hydrogen (90% efficient), then finally use it in a fuel cell to make electricity (40% efficient)? A lot of energy wasted when you could use electricity directly in an all electric vehicle, rather than a fuel cell vehicle.

He also mentioned that if you want to liquify the hydrogen to save storage space, that would cost you around 40% of the energy contained in the hydrogen....there is research to store it instead embedded in a special metal alloy, but that gives you problems of weight.

Even for using hydrogen as a storage, newer types of batteries seem much more efficient.

[Claire]

Yes solar is exciting for the future but I have to stand by what I said originally, that it's not a good bet in the UK and at the moment i.e. not until we get better products and processes (which is what I said in my original post) - am I correct in saying that none of the products you're talking about are actually on the market Nocturn? I can't, if sufficently excited by your excitement, go out and get a solar panel tomorrow morning that will give me those kinds of paybacks in environmental and financial terms?

Don't think I'm anti-renewables, or even anti-solar - I'm not - I'm just pro-"doing the maths" on these things. I'm also probably a bit over-cautious because I work with someone who's prone to getting highly over-excited and rather muddled about new stuff that's out there. It's like the guy has a form of environmentally conscious gadget mania!

Have to admit though, I can't wait to be able to get the gen on the solar house paint....

[Nocturn]

I completely understand what you mean, don't get me wrong

A few years ago, I was pretty excited about all the hydrogen fuel cell tech, pushed on by auto makers and oil companies (which would now like to be called "energy" companies). But now, having looked at the figures I realized it's not a very good solution at all. Ofcourse they still push it because the still want you to go to a refueling station which they own.

I'm saying that any info that's out there has to be taken into consideration, you can't be too naive about it, but you can't give something a definite thumbs down either.

Solar has for a long time been dismissed simply because it's too expensive, but when you look at recent figures the prices have come down substantially.

Even with current panels at around 18% efficiency, ones that you can actually buy today, for me it still makes sense. The environmental and economical payback depends ofcourse on where you live, but in my other post I tried to give an example in the UK, not even taking the best solar incidence figures in the UK, and I got an environmental payback time of 3.5 years. If you think I've exaggerated something, or my figures are wrong, I'd love for somebody to point that out to me. I'm trying to learn about this as much as I can after all. I'm not really trying to convince you of anything, but would just like to have a balanced argument.

About the new panels, how far off are they? Well I mentioned the new panels from SunPower will be available in 2007 (22% efficient), and the Nanosolar thin film ones will also be available in 2007, so it's really not that far off.

To me, the benefits of solar vs wind, biofuels, hydro are clearly evident. There is no extra infrastructure needed to install solar panels, no dams to build, there is no farm land needed, and personally I don't want to see spinning windmills everywhere I turn.

If in 30 years from now an ever better tech is available, by all means, lets use that. But here we have something that we can do now, today. I can't help but feel many people say they are concerned about the environment, but in the end unfortunately, they are more concerned about their wallet, even in cases like this, where the "risk" is virtually non existent (I forgot to mention the kind of warranties you get from the company that installs the panels).

This is really why so little is happening.....lots of talk, lots of concern, lots of heavy criticism towards oil and power companies, yet when it's time to actually do something....