Calculation for carbon saved per kWh generated by solar PV?

celerity

As per the subject, what can I reasonably estimate as carbon savings per kWh that I generate via solar PV?
My SunnyBeam monitor has a default setting of 1.5lbs/kWh but I have no idea how this is derived.

Thanks,

/\dam

celerity

According to this site, "The emission factor used by Government is 0.43kg of CO2 / kWh".
Fair? Outdated? Opinions welcomed.

/\dam

Martyn1981

celerity wrote: »

As per the subject, what can I reasonably estimate as carbon savings per kWh that I generate via solar PV?
My SunnyBeam monitor has a default setting of 1.5lbs/kWh but I have no idea how this is derived.

Thanks,

/\dam

Adam, hope this helps. Had to search back through some issues of New Scientist for an article on frack gas in the US. I remembered some comparisons regarding the use of electric cars to petrol.

Anyway, long story short, under the heading 'typical power plant emissions' it states US 755g/kWh and European 467g/kWh.

Appreciate you asked UK, but hope that helps support the 430g you found.

Edit: The article also states that the most efficient gas plants emit around 440g/kWh.

Mart.

celerity

Cheers Mart, don't suppose you can dig out the issue number?

Martyn1981

celerity wrote: »

Cheers Mart, don't suppose you can dig out the issue number?

Since it's you.

Issue 2853, 25/2/12, Page 48, Title 'The great gas showdown'.

"Take the European Union. To ward off dangerous climate change, it wants greenhouse gas emissions cut by 80% of their 1990 levels by 2050. According to the Committee on Climate Change, which advises the UK government, this means CO2 emissions from electricity need to fall from around 500g/kWh today to 50g/kWh by 2030."

Good luck with that!

If you (or anyone else) wants some back copies I'm happy to post a bundle for free. Tried giving them to the library but apparently they have to pay for periodicals before they can display them. Seems a shame to recycle them, my chiro and physio's offices are already overflowing with em, surrounded by well thumbed copies of Heat etc!

Mart.

celerity

Superb, issue located, thank you!
I have a backlog of New Scientists in my office but they arrive quicker than I can read them properly. :-(

/\dam

penrhyn

Does any of this greenwash take into account the carbon footprint of manufacturing solar panels, inverters etc?

celerity

seagull09 wrote: »

"A recent study found that it takes 250kWh of electricity to produce 1m2 of crystalline silicon PV panel. Under typical UK conditions, 1m2 of PV panel will produce around 100kWh electricity per year, so it will take around 2.5 years to "pay back" the energy cost of the panel."

Thanks for posting this. [STRIKE]Do you have a source for the recent study please?[/STRIKE] [completely missed the link you provided, sorry! ]
The best article I found was here, which estimates 420-600kWh/m2.

Regarding generation, I've just done a rough estimate from my system, which will be a year old this week.
We've generated approx 4400kWh in a year and have 17 panels, so 260kWh/panel. Each panel is approx 1.6m2 so that is about 162kWh/m2/year. So your figure of 100kWh is, if anything, conservative.

It seems pretty clear though, that the "energy repayment" period for panels is say, 2-3 years, whereas the lifetime of the panels is more like 25-30 years.

/\dam

Martyn1981

celerity wrote: »

It seems pretty clear though, that the "energy repayment" period for panels is say, 2-3 years, whereas the lifetime of the panels is more like 25-30 years.

/\dam

Just to be pedantic, and to follow Penrhyn's statement, you also need to allow for associated / supporting kit. Can't remember where, but I've heard similar figures of about 2 years for panels, and another 2 years for inverters, rails, cables and so on. So around 4 years in the UK, less in higher solar regions.

So if panels are good for 25 to 40 years, that's a 6 to 10 times energy payback. Regarding carbon footprint, well that would depend how good or bad the energy in the country of origin is, when compared to the UK. In the above example, if they were manufactured in the US, then repayment would be a little longer, as they'd be displacing lower carbon leccy in the UK.

In an ideal world, all renewables factories would be powered by renewables. Nothing is ever simple, is it!

Mart.

jamesingram

check out http://www.earth.org.uk/_gridCarbonIntensityGB.html
for current grid carbon intensity and mix.

rogerblack

Martyn1981 wrote: »

Just to be pedantic, and to follow Penrhyn's statement, you also need to allow for associated / supporting kit.

In addition, calculating internal energy displacement is hard.

If I put my washing machine on at midday, and use free solar to run it - then only if I was going to run the exact same cycle nomatter what the weather or time of day does it simply subtract from the grid use.

If you have a 4kw panel, that you have setup so that when it's sunny, 3kW goes to water heating, rather than using gas, your solar water heating does _not_ have zero carbon footprint.