[PV post] Emergy - embodied energy

[PVPoster1]

[This is an edited re-post of a topic that existed before the forums were hit by a virus in June 2005. Please feel free to add comments at the end]


http://www.holmgren.com.au/Downloadable ... Emergy.pdf

Emergy analysis provides a surprising and challenging result for the renewable energy industry. Photovoltaic panels may be the most environmentally sound way to provide a needed commodity called electricity at some sites not connected to the grid, and banks of panels may be used to complement other primary sources of power. But emergy studies of existing solar systems shows a net loss so large that improvement in technology are unlikely to make the sun a rich source of industrial energy. In other words an industrial society running on solar energy without fossil fuel subsidy is thermodynamically impossible.

[PVPoster1]

At the PowerSwitch meeting in January 2005, we had a renewable energy academic researcher present. When asked about the time for a PV solar system to pay back its production energy, he said it was only a few years, and the very latest materials could achieve payback in 1 year.

This was a lot more positive than what I'd heard before, but he was better qualified to give an opinion than me. I was quite encouraged by the figures, though this on its own is not enough - renewable electricty on its own can't solve our transport problems for example.

[PVPoster1]

Sounds improbable to me, given PV's low efficiency.

I'm interested to know about your meeting though - any chance of a write-up?

[PVPoster1]

Sounds improbable to me, given PV's low efficiency.

I'm interested to know about you meeting though - any chance of a write-up?

Sounded improbable to me too, but my last data on it was very old, and the guy knew more about it than I did.

I think James may have written up some notes from the meeting, I'll check with him.

[PVPoster1]

Even if successful, surely it can only provide relatively short term assistance as the production and maintainence of components, as well as transport, must rely on our use of machinery? in fact i find it very difficult to comprehend any sort of organised sustainence of useful energy sources is possible.

it feels as though we are clinging to a way of life which cannot be maintained by our planet.

[PVPoster1]

it feels as though we are clinging to a way of life which cannot be maintained by our planet.

We are trying to do the impossible.

http://edison.ncssm.edu/programs/colloquia/bartlett.ram


End of PV posts

[heinbloed]

The energetic amortisation of a grid connected PV module with an output of 1000 kwh/kwp and 20 years of usage is between 3-7 years .
http://www.sfv.de/lokal/mails/wvf/amortisa.htm
That was 1995 . In the meantime manufacturing has become much more economic. Efficiency has increased fro 4-7 % to nearly 40 % . But these 40% efficient modules are not for sale now. Hopefully next year .The manufacturing plants are just being build .The trick ? Just a lense in front of the cell . Eureka !
I could dig deeper , if there is demand ?
Excuse my bad English.

[DamianB]

Hi heinbloed.

I'd like to know more please. I know someone who is working on using Fresnel lenses over PV cells.

[RevdTess]

This looks interesting. 37.3% efficiency?

http://www.pyronsolar.com/US/home.htm

[Bandidoz]

Yield: At 2,850 kWh/m2yr direct-sunlight as in sunny deserts, the annual electricity yield will be 450 kWh/m2year or 450 GWh per km2year

What people tend to forget when they're busy masturbating with excitement over these numbers is that a lot of dust is blown where there is strong sunlight. This essentially means that any major solar installation, particularly one that features a lot of optics, will require almost continuous maintenance to keep them clean.

[fishertrop]

This essentially means that any major solar installation, particularly one that features a lot of optics, will require almost continuous maintenance to keep them clean.

Don't we have neough people then to handle myrid meanial tasks?

For me PV panels made today, with cheap fossil energy are 20-year bridge while we sort ourselves out.

It doesn't matter if it takes HUGE amounts of fossil energy to make PV panels today, so long as the panels give back some energy long after fossils fuels become scarce.

Anyway it's either make PV panels with it or fill up your Hummer with it.

We should spend tons of energy today making things that will give back energy in the decades to come.

40% efficiency would be great, but the current 17% units will do if we make enough of them while we have the means to do so cheaply and easily

[heinbloed]

Spot on , Tess.
http://www.zeit.de/2005/18/E-Solarkraftwerk?page=1 , see also page two and three .
A long article , in German , so I extract :
These new cells -equipped with lenses - are floating in water, making them too heavy to be placed on a roof (according to H.Scheer,Chief of the Solarstiftung ) .
According to " Bolkow Systemtechnik " 12.700 km2 of these cells placed in the Sahara would cover the entire electric energy demand of Europe.
Involved in Pyronsolar is " Jungbeker Technology " and -hold your seat - Edward E.Nixon as CEO , brother of the former US president.
BP has tested the new cells and found teething problems as short circuits in the cells , quickly dusting of the cells -see the comment of Bandidoz- and material problems with the insulation.
Another new PV cell has been developed by the " Fraunhofer Institut " using a blend of gallium and germanium , instead of the more common silica . These g/g cells have an efficiency of 35 % - without lenses.
End of extract .
My opinion : The dusting up problem could be overcome by either an
anti statically charging - the charging electricity would be home made - or by the so called " lotus effect " that is already widely used in the glazing industry .
Imagine the efficiency of the gallium/germanium cells of the Fraunhofer Institute in combination with the lenses of Pyronsolar......

[Bandidoz]

Yes I can imagine something like those belts they use on the cameras on F1 cars

If the lenses are suspended in water then I guess a small current could move all the debris to one side.

[calvin.jones]

I found this post when looking for some information about energy return on investment for solar PV.

I`m a bit dubious about using any sources either from thinktanks or industry. I found 3 relavent reports in the end and thought i should post them her for others to use if of interest.

The are from 1. ECI (Oxford Uni, UK)

http://www.eci.ox.ac.uk/pdfdownload/ene ... c%20eci%22

2. Tyndall Centre (Several UK Universities in Colaboration)


http://www.tyndall.ac.uk/publications/w ... tyndall%22

and the

3. House of Lords Science and Technology Committe

http://www.publications.parliament.uk/p ... c%20eci%22

More of this and a rant on my blog

[heinbloed]

The payback time for PV cells (not the entire panel) is now reduced to 1.3 years. So the energy used to manufacture a PV cell (16x16) will be produced by the same cell in 1.3 years. However the entire board plus the converter will still push it down to around two years for a small installation. As usuall-the larger the installation the shorter the amortisation.

And concerning the Fresnell lense cells: they are mafucturing them now on a small scale.
Sanyo has reached now an efficiency of 21.6% (according to their own tests) on 100cm2 cells.
Their commercialy available standard modules have reached already an efficiency between 16.1% and 17.2%, depending on the type. What is the efficiency rate of uranium rods, btw. ?