Solar panels

DSC_8807

We’ve finally got round to having solar PV panels installed. As you can see form the picture above.

The price of solar has been coming down, but still it isn’t economically viable without subsidy for us. However, the subsidy makes it clearly economically beneficial (to us) so combined with a guess that the ecological payback, which is far less clear, might be acceptable too, we went ahead. What finally tipped us into doing something was (a) the government announcing the end of the fat subsidy regime (of which more anon) and (b) a local group organising an installation firm for the village.

Economics

Let’s talk about the economics first. In the UK, this is all about the subsidy regime which is currently £0.433 / kWh for solar PV retrofitted, for an installation less than 4 kW. That compares with a cost of electricity from the mains per kWh (inc VAT) of ~£0.25-0.12 (depending on supplier, tier, phase of the moon, whatever). But since our energy needs are vastly less than our installed 3.5 kW, and we’re usually out during the day, most of the time we won’t be saving that money, instead we’ll be feeding stuff back into the grid. And I don’t really know what we get paid for that – casual conversation said £0.02/kWh, this says… its complicated. I can’t even remember if we did the 50:50 “deeming” deal spoken about there.

With all that, the payback time was put to us as being about 9 years. Since it cost ~£10k, that implies generating about £1k/year of power, which certainly exceeds our current bill. Given that price depends so heavily on the subsidy, these calculations only apply to the UK. We scrambled to get our installation in place before December 12th, when the subsidy was due to ~halve, but Solar tariff cut plan ruled legally flawed says that maybe that won’t be the cut-off date. It will be soon, though. Which is probably correct: the price is currently set too high, and its a cash cow for people with the installation.

Our system

DSC_8955-sunny-beam We have 15 Trina panels which are supposed to produce around 220-240 W each (so ~3.3 kW), a 3.5 kW inverter (Schuco) in the loft, wires leading down the the electricity cupboard, several isolator switches, and a meter thingy which we need to read sometimes and send in, in order to get our subsidy. Note that to get the good subsidy, you need a system < 4 kW, but we'd have struggled to get more panels on our (fairly small) roof. We were originally going to have 16, and a 4 kW inverter, but apparently the 4 kW ones are in short supply.

Most excitingly, we have a "sunny beam" Bluetooth power meter, which talks to the inverter in the loft, and draws pretty graphs of your power generated and £'s saved. Miranda in particular loves it, and consults it every day. She did want to take it away with her on a recent visit elsewhere, but we explained that Bluetooth doesn't have a range of 100 km.

Bronte Captial (that isn’t his best post on Trina, search around, you’ll find the rest) isn’t too impressed with Trina as an investment – indeed, he thinks that all panel makers are due to get squeezed. But that doesn’t affect me as a buyer.

The ecologics

Well, I dunno really. I’m assuming that, since it has to be subsidised, the total unsubsidised economic value must be negative. And therefore, using economics as a proxy for ecologics, the ecological value must be negative too? That is less clear; after all, we don’t cost externalities into our electricity costs.

Refs

* Upbeat energy were the people who did us, and others in the village. They seemed quite competent and got the job done.
* The eCoton posting with links to some (probably now obsolete) information.
* Misc pics of the installation; more.
* BP exits solar says Timmy. Shades of Bronte.

Comments

  1. #1 David B. Benson
    2011/12/22

    Rather than ‘ecological benefit’ (whatever that is), measure it in terms of kgs of CO2 avoided. (There is an additional benefit for not burning coal.) This is much harder to determine than one might first suppose. Indeed, it is probably much less than one might first suppose based solely on kWh generated. The difficulty is in the additional variable generation of the balancing agent (i.e., backup).

    If there are very few solar PVs installed, the additional variability can be neglected. As the number of installations grow so does the additional variability.

    [In fact, working out the CO2 avoided is easy - because the little meter tells you. Of course, it may not speak sooth -W]

  2. #2 Kooiti Masuda
    2011/12/22

    Whether solar PV is environmentally beneficial depends on whether it covers the energy cost to produce the system to produce and deliver electricity (not just the panels).

    With the technology available in 1970s the energy cost was certainly high. Someone (probably a physicist) said that “solar cells are just canned petroleum energy”. It was perhaps a fair comment then. And many science-oriented people think that what was true in 1970s must still be true. But, thanks to evolution of basic science of solid-state physics, the technology changed very much. Experts at a Japanese national institution says that the energy pay-back time of recent solar PV systems is around 2 years.

    But peripheral things matters. As a leading engineering professor remarks, the energy cost will be considerably higher if the stand to hold PV panels to the right direction is made of aluminium, which is virtually re-packaged electricity. It is surely low if the existing roofs are used without reconstruction.

    [The rails that the panels sit on look like extruded Al (see e.g. http://www.flickr.com/photos/belette/6443632385/in/set-72157627979005935/). The brackets connecting those to the roof are solidish steel -W]

  3. #3 Kooiti Masuda
    2011/12/22

    Whether solar PV is environmentally beneficial depends on whether it covers the energy cost to produce the system to produce and deliver electricity (not just the panels).

    With the technology available in 1970s the energy cost was certainly high. Someone (probably a physicist) said that “solar cells are just canned petroleum energy”. It was perhaps a fair comment then. And many science-oriented people think that what was true in 1970s must still be true. But, thanks to evolution of basic science of solid-state physics, the technology changed very much. Experts at a Japanese national institution say that the energy pay-back time of recent solar PV systems is around 2 years.

    But peripheral things matters. As a leading engineering professor remarks, the energy cost will be considerably higher if the stand to hold PV panels is made of aluminium, which is virtually re-packaged electricity. It is surely low if the existing roofs are used without reconstruction.

  4. #4 Alexander Ač
    2011/12/23

    William, should be solat, or solar?

    [Hmm, not sure how I managed that, but now corrected -W]

    And what about the low albedo of solar panels? ;-)

    Interestingly, there were some protests in China regarding solar factory (70 % of all solar panels is made in China), because of polluting nerby river, more on protest in China here:

    [Should that me nearby ;-? Our Trina panels are from China -W]

    Back in September, massive protests outside a solar factory in eastern China forced authorities to shut down the plant, which had been accused of contaminating a nearby river.

    http://www.businessinsider.com/haimen-china-protest-power-plant-2011-12

    Alex

  5. #5 Aziz
    2011/12/23

    It is a good solution to reduce the bill cost. In Germany most of DMs use solar panels.

  6. #6 Alexander Ač
    2011/12/23

    Yeah, nearby :-)

    Little bit OT, but not so much, given the effort to reduce our collective GHG footprint..

    Stuart Staniford seems to be less worried about (worsening, or overblown?) methane situation than prof. Ugo Bardi (both coming from the peak oil camp), sees Ugo’s reaction here:

    http://cassandralegacy.blogspot.com/2011/12/history-of-humankind-in-six-frames.html?showComment=1324558223256#c3887156089029219587

    Alex

    [I'm not sure the "Arctic methane emergency group" can really be trusted. It includes Andrew Lockley, who I presume is this one which is Bad (check contribs). For the moment, the best guide is actual methane concentrations -W]

  7. #7 PeteB
    2011/12/23

    - I meant to look into it too, but too late now.

    Overall, I think it is a good idea to withdraw the scheme – I think it is pretty clear that Fossil Fuel generation + carbon tax (even at Stern levels) would be currently cheaper than Solar.

    [I would certainly support a carbon tax, and let the market sort out the How and What, rather than the government picking the subsidies. However, since we don't have one, that isn't an argument for reducing the subsidy now. My main argument for doing so is the governments one - that the subsidy is too lucrative -W]

    I think this is why it is better applying a carbon tax rather than governments ‘picking winners’ – there is probably a whole stack of stuff that is marginal, that when you apply a carbon tax – would trigger a move away from fossil fuels – but I don’t think Solar is there yet

  8. #8 Tim Worstall
    2011/12/23

    “In fact, working out the CO2 avoided is easy”

    Then it’s simple.

    CO2 avoided x Stern value of social cost of CO2 (8 US cents per kg). If this is greater than subsidy then it’s fine. If less then we’re wasting resources which is most unecologic.

    As an example, the number from a year or so back in Germany was $1070 per tonne CO2 not emitted as against that Stern cost of $80. Pissing money away and thus wasting resources.

    I’m one of those who think that solar will get there, will actually be cheaper than coal even ignoring externalities, but it ain’t yet.

    [I was joking, though. The device tells me the CO2 avoided, but presumably it is making some assumptions about the UK generating mix. I could have signed up to use Nukes only in which case my CO2 avoided is ~0. Or something -W]

  9. #9 crandles
    2011/12/23

    You obviously got it installed by 12th Dec. I imagine last 6 weeks were rather fraught for installation companies with customers very anxious about installation dates. Were you close to 12th and did this cause concern for installation date?

    [There was some concern, especially as a couple of things needed fiddling and reduced our time margin. In the end, we had our work finished by tuesday, our certificates by wednesday, and I was going to mail them in on thursday but they turned out to accept email so that was less hassle; and the deadline was the next monday -W]

    I am expecting that we will get 50% of generated electric sold to grid at 3.1p/KWh making payments effectively 44.8p/KWh generated. They don’t meter usage just meter the generation and assume 50%. If it is connected to grid I cannot see any reason not to opt into scheme so hopefully supplier guided you to tick the box on the forms. If you failed to tick the box to opt in, I think there were annual opportunities to opt in or out.

    I think you should be able to get 3.92KWp system for about £10k and less than that after April. I paid ~£10.5k and subsequently saw advert for £9950 but prices probably rose approaching 12 Dec.

    So you can tell that I think it is clear that the 43.3p subsidy is sufficiently lucrative to allow the installation companies to get away with charging a high rate for their services.

    After the subsidy reduction, competition between the installation companies to survive might be interesting. I wonder how low the installation element of the cost will fall.

    [Agreed. I expect panel prices will fall (I think they are ~60% of the cost), and people could get more efficient -W]

  10. #10 Brad
    2011/12/23

    The aluminum in the frames is of course, highly recyclable with minimal additional energy inputs, so you are really just borrowing the cost of smelting the aluminum for perhaps thirty years or so. Other factors like corrosion resistance affecting estimated lifetime probably make aluminum the best choice.

    Here in Manitoba, Canada, our electricity rates are very low – 6.5 cents per kWH for domestic use, which makes solar unattractive. Payback times for small solar installation would be at least 25 years even with zero interest cost. Ontario has subsidized small to medium renewable energy tie ins with guaranteed rates up to ten times commercial rates which has led to farmers plowing under orchards and vineyards and paving them with solar panels. I have my doubts this is overall a smart move.

    [Um, but don't forget that what makes my panels attractive isn't the electricity cost either - its the subsidy per kW generated, which is entirely independent of use -W]

    Solar makes sense where mains electricity isn’t available. We use it for powering electric fence energizers, many cattle farmers use it for pumping water for cattle on remote pastures. I know a small ISP who has a number of hilltop wireless relays powered by solar, and I’m sure it is a boon for the third world for things like lighting and battery charging for cell phones and radios.

    At present, the low-hanging fruit is energy conservation, everything from mass transit to energy-efficient cars to retrofitting buildings with better insulation to reduce heating costs. Just my opinion of course.

  11. #11 Jumper
    2011/12/23

    Of course if one used solar electricity to make the aluminum, and all the components, the CO2 costs are entirely different. This is where I get completely confused.

  12. #12 crandles
    2011/12/23

    >{Agreed. I expect panel prices will fall (I think they are ~60% of the cost), and people could get more efficient -W}

    16 of these 245W panels (the ones I got, made about 14 miles from me)
    http://www.swithenbanks.co.uk/Solar_Photovoltaic_Equipment/294/product.html
    at £310 each inc VAT is less than £5k and I wouldn’t be at all surprised if solar installers get some volume discount. So panels already under 50%.

    Re People could get more efficient. Hmm, at doing the installations or at remaining MCS accredited rather than becoming accredited and similar? I think there is more in the pricing of the labour than in the hours per installation.

    [Our people could have scheduled things a bit better - they used more electrician time than was really needed (see-also http://www.flickr.com/photos/belette/6466637459/in/set-72157628306966429/, showing them putting the meter in the wrong place to start with). Scaffolding time must be a cost, too - not sure how that can be improved -W]

  13. #13 DavidinCalifornia
    2011/12/23

    I put in a 4.68Kw PV system 1.5 yrs ago. After the rebate and tax credit my net cost was $9,500 (US). I installed the system myself, so that cut the cost in half. My annual electric bill was $2,100 prior to install. After the first year it was reduced to $340, Therefore my system should pay for itself in a little over five years.

  14. #14 Turboblocke
    2011/12/23

    When calculating the kgs of CO2 saved, you shouldn’t use the average of the energy mix rate. When renewables go on line, they displace the most expensive other supplies. These generally tend to be the most inefficient and probably the most polluting. However, as it’s a free market, you can’t be sure. For more details check out the Merit Order Effect.

    BTW: I live in France and there are subsidies for home installations in the form of tax breaks. I was interested in a system a couple of years ago but not being in a position to fully benefit from the tax breaks I looked at getting an installation outside of the subsidy scheme. I looked at systems from the UK, Belgium, the Netherlands and Germany as well as France.

    I easily got quotes for systems with subsidies, but not for unsubsidised sytems. I was mildly amused to find that if I subtracted each countries’ subsidy from the price in that country I arrived at similar figures across all the countries.

  15. #15 DavidinCalifornia
    2011/12/23

    I put in a 4.68Kw PV system 1.5 yrs ago. After the rebate and tax credit my net cost was $9,500 (US). I installed the system myself, so that cut the cost in half. My annual electric bill was $2,100 prior to install. After the first year it was reduced to $340, Therefore my system should pay for itself in a little over five years.

  16. #16 TheGoodLocust
    2011/12/23

    What concerns me, from a “sustainability” aspect, is the mandates that power companies buy this electric power from people.

    It is an odd scenario where someone must buy a product due to government mandate.

    Who pay for those buying the power?

    Other customers through higher rates. Will that encourage a massive number of people to buy solar panels? It seems to me that this would eventually reach a point where the power company couldn’t pay for the solar energy anymore.

    They would have to raise the rates incredibly or the government mandates would have to be abolished.

    I mean, it is nice for the people with solar who can sell the energy during the day at a premium and get fossil fuel energy at night in exchange, they get a cheap bill, subsidized by poorer people who can’t afford solar systems, but I don’t think it can be scaled up effectively.

    [Not sure what you mean. The power companies buy power back at a much lower rate than the rate we pay for power, as I said -W]

  17. #17 crandles
    2011/12/23

    > Scaffolding time .. not sure how

    Some simple arrangements: First, which we used, is get together with neighbours and order at same time offering the benefit of minimal movement of scaffolding. If you are lucky and they don’t want to find the £10k, you rent their roof in order to double your investment. I wasn’t that lucky.

    Second would allow homeowners to fit rails themselves to reduce installation cost but that may involve more accidents and take more time.

    Third each gang to own their own scaffolding, preferably after job going to a gang-members home rather than extra journeys to the company’s premises. Probably with some extra company scaffolding to cope with 3 stories …. I believe our installers owned their scaffolding and trailer.

    Even if unnecessary for a bungalow, I wouldn’t be too surprised if time putting it up may be saved in carrying out work.

    AIUI scaffolding time is pretty cheap, it is the (dis/)assembly that is risky and expensive. Making sure assemblers are going to be using it seems to be one risk reduction strategy.

  18. #18 David B. Benson
    2011/12/23

    Solar PV tends to displace first, natgas burners and second, coal burners.

  19. #19 Rob Dekker
    2011/12/24

    William, congratulations !
    You are ahead of me here. Here in California, your panels will probably generate more power (even today, we had bright sun and clear skies) so we could have made a deal where you pay for my panels and I pay you back the savings ;o)

    [That is a fair point, though you wouldn't have been eligible for our subsidy. Some people have been getting them installed on west-facing roofs, because that is what they have. Undoubtedly the same panels, in California on a south facing roof, would generate double the power; that would be far more sensible, in an ideal world -W]

    Uptil last year, the utility company here also would not pay you anything for the kWhs you generate in excess of your usage. However, the law changed here in California, and you now get residential rate paid for every excess kWh generated. This is done on a yearly basis.
    Either way, I still think that solar power could only become economical if done on a large scale. Installation costs (with people climbing on your people’s roofs, with each roof being different and such) simply will always be much more costly than simply lining up thousands of panels in the Mahovi desert.

    [Very likely. Roofs are used just because they are spare (though for new-build, the scaffolding costs disappear, and indeed you should be able to save on tiling costs). We have no empty deserts, other than Slough, to put our panels in. I've seen semi-serious proposal to put the panels in the Sahara, and xfer the power back (cables, or as hydrogen) -W]

  20. #20 John Mashey
    2011/12/27

    Roofs are used because they are spare, but also because they do not require new transmissions lines and rights-of-way, as do some utility-grade solar farms. THer is plenty of room for both, and of course, new construction is easier.

    Commerical roofs are easier, and one finds panels sprouting around Silicon Valley on roofs and over car parks.
    The latter is a triple win:
    1) Generates electricity.
    2) Keeps cars cooler.
    3) Asphalt parking lots can get hot, making a little heat island around the building, thus making air conditioning work harder. Solar panels over parking lots lessen this.

    If starting from scratch, here’s a very cool NASA building.

    Of course, climate differences matter, and optimal solution mixes vary radically.

  21. #21 TH
    2011/12/27

    There may not be deserts in the UK, but East Anglia is not short of flat land. There’s a 5MWp solar farm out at Wilburton, north of Cambridge, and another being built at Chittering.

  22. #22 Brian Schmidt
    2011/12/28

    “we could have made a deal where you pay for my panels and I pay you back the savings”

    Three cheers for offsets!

  23. #23 Paul Kelly
    2011/12/29

    Way to go. You’re now in the running for this year’s Exemplar of the Bottom Up Walk the Walkers. The price of the fossil fuel externalities your installation prevents should factor into your economic calculations. Also, there is a real economic value to the fulfillment of your desire to do something beneficial for climate and/or be on the cutting edge of technological progress.

  24. #24 Anonymous
    2011/12/29

    We have no empty deserts, other than Slough,

    Seriously? Have the friendly bombs fallen at last?

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    2012/03/29

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