Grid tie solar (PV) in cloudy ol' England

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Grid tie solar (PV) in cloudy ol' England

Post by sheddi » Mon Sep 10, 2012 2:18 pm

I know the topic of solar power gets the occasional mention in Self-Sufficient Living, so I thought I'd share our experience so far.

Back in January we had a grid-tie PV system installed. We'd have liked 4kWp of panels, but due to a lack of roof area we had to settle for 2.7kWp - eleven 247Wp Samsung panels in a single string.
Image

The panels feed a 2.5kW Kaco Powador inverter (a German brand). It's in our loft space and I don't have a decent photo, but it looks like this.
Image

The inverter output feeds our generation meter, which in turn connects via a chunky isolator to our domestic distribution board. Surplus power is exported to the grid but (as is standard for UK small-scale PV systems) we have no export meter.
Image

Our roof faces a little West of South, so the alignment is good but not the best. There's no significant shading (the closest trees and buildings are far enough away not to be a problem) but, as mentioned, we're in England which is hardly an ideal solar power location. We're at 51 degrees North, a similar latitude to Calgary, CA: https://en.wikipedia.org/wiki/51st_parallel_north

The system went live in late January, and (at time of writing this) we've generated 1965 kWh. The installers provided us with an illustrative calculation suggesting that in an "average" year we might expect to generate 2400 kWh, and we're pretty much on target to hit that this year. (Owing to seasonal variations most of the generation is during the period April - September.) Given that our typical annual power consumption is very roughly 4000 kWh/yr, we're generating 60% of our electricity demand. (Due to the nature of grid tie, we're still importing roughly as many kWh/yr as we're generating.)

So far, so good. How do the economics shape up? Well, the installation cost us £8350 (call it $13k), which isn't trivial. Prices for PV systems have come down significantly since January and an equivalent system installed today would only cost ~£6000 (call it $10k). However by choosing to install in January we qualified for a significant UK government subsidy via a feed-in tariff, which (together with the savings on our power bills) means each kWh we generate is worth ~£0.50 / $0.80 to us for the next 25 years (and this return increases in line with inflation). We're thus expecting to gain ~£1200 of benefit annually, and the system will pay for itself in 7 years after which point we're in credit for the next 18 years. In purely financial terms, and even factoring in our natural gas use, our net energy bills for the next 25 years should be paid for.

Clearly, being a grid-tie system, we've not gained any significant degree of energy independence, but having the panels are on the roof gives me the option of adding an island-mode inverter at a later date, for use during outages ... (obviously all the usual constraints regarding generator transfer switches will apply in this situation).
Last edited by sheddi on Mon Sep 10, 2012 3:19 pm, edited 3 times in total.
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Grid tie sola (PV) in cloudy ol' England

Post by wee drop o' bush » Mon Sep 10, 2012 2:25 pm

Interesting post :)
We've thought about getting either solar panels or a wind turbine but as yet are unsure which would suit our location best. To be honest it looks likely that it would be a wind turbine but your info was very useful, thanks.

There haven't really been the best weather conditions so far for optimum solar panel charging...let's hope this improves.
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Re: Grid tie solar (PV) in cloudy ol' England

Post by sheddi » Mon Sep 10, 2012 2:54 pm

wee drop o' bush wrote:Interesting post :)
Thanks :) I thought it might provoke a few thoughts!
We've thought about getting either solar panels or a wind turbine but as yet are unsure which would suit our location best. To be honest it looks likely that it would be a wind turbine but your info was very useful, thanks.
There's a very useful site for the UK here that lets you pick your roof from Google Maps and it then calculates your PV potential and gives you a choice of pricers from local installers:
http://www.comparemysolar.co.uk/" onclick="window.open(this.href);return false;

There's also an EU-run site here that gives estimates for the solar potential of the whole of Europe and Africa:
http://re.jrc.ec.europa.eu/pvgis/index.htm" onclick="window.open(this.href);return false;
There haven't really been the best weather conditions so far for optimum solar panel charging...let's hope this improves.
Very true, this year's not been very good although there were the occasional spells of fine weather; March was particularly good.

See:
http://www.guardian.co.uk/uk/series/las ... -s-weather" onclick="window.open(this.href);return false;
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Grid tie solar (PV) in cloudy ol' England

Post by wee drop o' bush » Mon Sep 10, 2012 3:02 pm

We only farm sheep here so apart from domestic use (I'm avoiding the tumble dryer at all costs) our electric bill isn't too bad. But it could be much better.
Our own renewable energy production is something my husband & I actually need to stop generally considering & actually have a serious discussion about.
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Re: Grid tie solar (PV) in cloudy ol' England

Post by Dawgboy » Mon Sep 10, 2012 3:16 pm

Very nice system! That steep roof will be nice in the snow. I am familiar with the Kaco controller, and they are High quality. You *could add a few batteries for a little extra "oomph" if the grid goes down. Not difficult, and I am betting you already have an automatic cutoff already, as that is required on Grid ties in the US for line worker safety.
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Re: Grid tie solar (PV) in cloudy ol' England

Post by sheddi » Mon Sep 10, 2012 4:01 pm

Dawgboy wrote:Very nice system! That steep roof will be nice in the snow.
Thanks Dawgboy :)

You're right about the roof; we had a little snow back in February and it slid right off the glass facing the panels. Also, the rain does a good job of cleaning off any dust and dirt.
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Re: Grid tie solar (PV) in cloudy ol' England

Post by majorhavoc » Fri Nov 02, 2012 7:57 am

Was directed here via the link in your post to the discussion about solar/wind power alternatives to gasoline generators in the aftermath of hurricane Sandy.

You raised a really interesting point in that other thread: to get solar systems that can generate a realistic amount of household electrical power in emergencies, they don't really make economic sense unless you see emergency back up power as a side benefit to a permanent, full time supplement to your energy needs. Short term, fossil fuel generators are still a more cost effective solution if all your looking for is temporary emergency power.

But with the capability of moving to "island mode" (what we on this side of the pond refer to as going "off grid") your present solar system offers a compelling capability to weather a more serious sort of emergency; the kind of long-term national or global disasters that can permanently change our way of life. The proverbial "zombie apocalypse" we often speak of metaphorically.

While I personally don't think such a long term disaster is likely in our lifetimes, I do often wonder to what extent our prepping should account for that possibility. A light duty grade emergency generator just isn't going to cut it long-term, even if by some miracle you could continue to obtain fuel to run it. It would wear out within months of continuous use.

I have to say: being able to produce appoximately 60% of your current household energy needs via solar panels is an enviable situation to be in, one that would serve you very well in maintaining a less energy-intensive, long-term lifestyle should the worst ever come to pass.

When trying to justify the economics of a permanent home photovoltaic system, the usual considerations are the up-front costs, various government incentives, on-going maintenance and the long term cost savings.

But for preppers like us, surely the insurance value of having an independent, reliable source of electricity during a potential long term disaster has to be part of the value equation.

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Re: Grid tie solar (PV) in cloudy ol' England

Post by sheddi » Fri Nov 02, 2012 10:38 am

Thanks for the feedback :-)
majorhavoc wrote:You raised a really interesting point in that other thread: to get solar systems that can generate a realistic amount of household electrical power in emergencies, they don't really make economic sense unless you see emergency back up power as a side benefit to a permanent, full time supplement to your energy needs.
It's easy to overlook the fact that the "running costs" of solar PV (as opposed to wind, say) are pretty minimal since there are no moving parts and next-to-no maintenance required. The panels will age while they're in the sun, whether you use the power they're generating or not; the inverter is potentially less robust, but other consumer electronics regularly reach 20+ years of age without complaint and I've no reason to expect less in this case.

The up-front costs of our system swallowed a significant portion of our savings; now it's got to work for it's living!
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Re: Grid tie solar (PV) in cloudy ol' England

Post by raptor » Fri Nov 02, 2012 10:51 am

Great write up. Thanks for sharing!

You monitor the electrical production of your system. It would be very interesting to see on a monthly basis the power it produces.

Obviously it produces less power in the winter and more in the summer, but the out put would be interesting none the less.

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Re: Grid tie solar (PV) in cloudy ol' England

Post by Angry Sapper » Fri Nov 02, 2012 2:05 pm

wee drop o' bush wrote:We only farm sheep here so apart from domestic use (I'm avoiding the tumble dryer at all costs) our electric bill isn't too bad. But it could be much better.
Our own renewable energy production is something my husband & I actually need to stop generally considering & actually have a serious discussion about.
Have you thought about methane capture? And run a genny off of sheep shit.
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Re: Grid tie solar (PV) in cloudy ol' England

Post by sheddi » Fri Nov 02, 2012 3:33 pm

raptor wrote:Great write up. Thanks for sharing!

You monitor the electrical production of your system. It would be very interesting to see on a monthly basis the power it produces.

Obviously it produces less power in the winter and more in the summer, but the out put would be interesting none the less.
Thanks raptor. I've got the data here; let me see if I can put it together in some web-friendly format.
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Re: Grid tie solar (PV) in cloudy ol' England

Post by sheddi » Fri Nov 02, 2012 4:11 pm

OK, here's a chart showing monthly output (blue bars, now red) vs the installers predicted output (orange bars, now blue), in kWh, up to the end of September (now November).

Image
January was a short month; the system wasn't commissioned until the month was more than half over.

According to this handy link the weather in March was much better than is typical over here, while April and June were much worse. September was cooler than usual yet still sunnier; make of that what you will!
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Re: Grid tie solar (PV) in cloudy ol' England

Post by sheddi » Sat Dec 01, 2012 5:19 am

If the image ever updates :roll: I've added in the results from October and November.

The colours are now Red and Blue, for reasons known best to Microsoft.
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Re: Grid tie solar (PV) in cloudy ol' England

Post by sheddi » Sun Nov 22, 2015 1:18 pm

A quick thread update to let you know that my generation meter has recently passed 10,000 kWh. We've achieved that in a couple of months less than four years, which means we've slightly exceeded the 2,400 kWh/yr forecast provided by the installers.

So far I'm very happy!
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Re: Grid tie solar (PV) in cloudy ol' England

Post by duodecima » Sun Nov 22, 2015 2:42 pm

Don't know how I missed this when you first posted, very cool. Congrats!

Our town is actually hosting meetings for solar, and there's several houses in the neighborhood (1 is 2 doors down) that have it already, planning to try to make the one in December, to see what the incentives & prices actually would be.

In our case, this is complicated by the approaching need for New Roof - we have asphalt shingles currently and we'd like to switch to metal (much better for rainwater collection if we ever needed to drink it!) but that's pricey, and should probably be done before we attach solar panels to the roof. ( :gonk: )
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Re: Grid tie solar (PV) in cloudy ol' England

Post by TacAir » Sun Nov 22, 2015 3:50 pm

sheddi wrote:A quick thread update to let you know that my generation meter has recently passed 10,000 kWh. We've achieved that in a couple of months less than four years, which means we've slightly exceeded the 2,400 kWh/yr forecast provided by the installers.

So far I'm very happy!
Thanks for the follow up. I understand that that UK will be (over time) shutting in all the 'legacy' coal-fired thermal plants. Will the resulting spike in electric costs be factored into your system subsidy?
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Re: Grid tie solar (PV) in cloudy ol' England

Post by KYZHunters » Mon Nov 23, 2015 2:40 am

Thanks for doing the math for us on the cost-benefit ratio and payback period. A lot of us think about these things all of the time but fall short of pulling the trigger on projects because of the question of financial viability. Looking strictly at the math, if one can afford the monthly payment, it becomes a no-brainer.

US readers should also look at the tax advantages of installing such a system since it drives down purchase cost significantly. Those of us with small farms should also look at the USDAs incentives for installing renewable energy. Between tax incentives and USDAs EQIP program, I only ended up carrying 10-percent of the initial cost for my wind installation.

Lastly, batteries are expensive as hell but getting better all of the time. Sadly, my batteries are getting a little sleepy after 5 years hard use and I'm swallowing hard at replacing them. The upside is, even if you do lose commercial power, you are getting a very usable amount of juice during the day, even in cloudy ol' England.

BTW...just got off a one week narrow boat cruise on the Oxford Canal and was impressed by the number of the canal boats making good use of their 40 feet of open roof space for solar installations.
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Re: Grid tie solar (PV) in cloudy ol' England

Post by sheddi » Mon Feb 22, 2021 12:29 pm

I mentioned this thread somewhere else (the Texas winter storm thread) so thought I'd better add an update here.

My grid-tie solar system is still going strong, nine years on from installation. I last read the generation meter on 31st January, about three weeks ago, and on that date it had generated a little over 23,000 kWh of electricity. That's an average of 2550 kWh/yr, a little more than the original installer's estimate of 2400 kWh/yr. I'm very happy with its performance to date.

Economically, we're received subsidy payments of around £11500 over that period (I've not added them all up but it works out as around £0.50 per kWh). The install cost in 2012 was £8350 which, if you adjust for inflation, would be £10083 today (per this link) so we've more than broken even. The next eleven years of subsidy payments will be straight profit.

Of course, solar PV prices have fallen sonewhat since 2012 and an equivalent system, installed today, would be around £3000 - but they've stopped the subsidy scheme, so there's no money to be made (there are a couple of options to offset costs but break-even is in the far future).

If I wanted to make my system more resilient I'd swap the current inverter for a hybrid one and add ~12 kWh of batteries. That would set me back around £3k to £4k so I'm not currently giving it serious consideration; I've got a 3kVA Honda-powered generator that got us through the only significant power outage in the past nine years without problems. If outages become more frequent (or I decide to switch to a Griddy-like wholesale pricing electricity tariff) I might reconsider.
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Re: Grid tie solar (PV) in cloudy ol' England

Post by Lettuce Pray » Mon Feb 22, 2021 2:21 pm

I am glad you posted am update. I wasn't around here when you did the original post so this update brought the thread to light for me. Congratulations on the system and its financial viability.

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