Telephone Sales and solar panels

[watervole]

I've just made a complaint to the Telephone Protection Service about a solar panel company.  Telephone cold-calling people on the TPS list is illegal.  I can't do anything about overseas companies, but I sure can complain about the UK ones.

That's the second solar panel company to phone me in a week.

I like solar power, I already have solar panels.

The usefulness of solar power in no way excuses people breaking the law in an attempt to drum up as much trade as possible before the level of subsidy falls.

If you want solar panels, do NOT let yourself be tricked by some of the con men out there.   There are some that will grossly over-estimate the likely yield and savings.  Go with one of the companies that fit free panels - you know exactly what you're getting with those - and they will only use your roof if it really is suitable as it's their money on the line, not yours. 

This lot - Apple solar energy - fall into the 'lying bastards'  category.  Their web site claims "Domestic Electricity prices are rising, but by installing Apple Solar Energy Solar Panels you can generate as much Electricity as you require – becoming self-sufficient."  

Self sufficient with solar?  Whatever happened to night time?

Comments

[vicarage.livejournal.com]

Most of my UK based telephone spammers are solar panel companies. I complain to TPS and ring them back with phantom calls.

[birdsedge.livejournal.com]

We were interested in solar but the 'free panel' company that I contacted said looked on google earth at our roof and they wouldn't touch it because it was 35 degrees off due south. Bummer.

How do you find the panels ylou hae? What benefit do you get (as the householder) since presumably the company that fitted them gets the subsidy? How much power do the produce and howe much does it chop off you electricity bill?

Just curious because I haven't given up on the idea, yet.

[watervole.livejournal.com]

Mine produce 2kw at peak, but you won't get that most of the time. 3-400W is more likely on an overcast day.

Haven't had them long enough to do a full cost-benefit analysis. It partly depends on whether you adapt your electricity use. eg. I now try and do laundry when the sun is shining.

I'll ask my sister about the site she did her math from. I know she found a good one for evaluating sites that aren't close to south.

[watervole.livejournal.com]

Gillian says:
umm, can't remember exactly where I got what I used. However there is a standard formula called SAP, which all the solar panel installers
use and refer to. It takes account of roof orientation, slope but not
latitude.

My spreadsheet notes say that:
The SAP formula says a 1 kWp array will produce 886 kWh for a 30
degree roof facing E/W. Multiplied by a standard factor 0.8.

The 886 was a number I got from an online calculator that takes
account of east/west and 30 degrees.
I think the 0.8 is a standard factor to take into account losses in
the inverter.
You are suppose dto add another factor for shading, but I didn't as
our roof is not shaded.


Back to Judith. Hunt the numbers and see what you get. I was surprised that Gillian's roof worked out okay. Be aware that chimneys can make a big difference. The shade (according to a friend) can cause something called a back emf and loses you more power than you'd expect.

[uitlander]

There are three of us within 5 miles of each other who have all bought identical systems from the same supplier. We all have 3.92 kWh systems, same panels, same inverter.

One has a house partially shaded by a flyover, and has an 'interesting' array of panels split across different bits of roof facing SE & SW. He gets the worse generation.

I and the other person have the same roof angle - 30° - and the same orientation - 160° - so not quite true south. He gets some shading from trees in the early morning, I have no shading issues.

We have been sharing dailing generation figures since our systems were installed. My generation is 8-10% higher than his on a daily basis. He's a physicist and is using our numbers, lat & long to build a better model of generation.

I have at times generated over 3.92 kWh at peak. The panels are also temperature sensitive and the rating is for their performance at 24°C. If the temperature goes above that their performance decreases, so some of the very hot summer days we have had actually generated less than on cooler days.

I am seeing a lot of panels around here going up on roofs that face East or West rather than south. I would be interested to see what generation figures they are getting.

[watervole.livejournal.com]

Interesting. I never knew there was a temperature factor.

My sister reckoned she could make a pair of E and W facing panels pay. It will be interesting to see the generation figures.

Temperature

[johnrw.livejournal.com]

The higher the panel temperature the lower the efficiency. Panels are rated at 24 or 25 degree C with a drop in efficiency around 0.1 to 0.2 % per degree C up to 80 degrees. In the UK air cooling is normally sufficient to keep this temp below 40 to 50 degrees so the loss is around 5% or so which will get lost in the 'noise' In the Caribbean I'm aware that some people have modified panels with water cooling pipes glued to the back of the panel and claim a twofold win. Increase in power by up to 20% and plenty of domestic hot water!

Re: Temperature

[wibble-puppy.livejournal.com]

It certainly is a win-win solution, isn't it! There's already a commercially available version of exactly this concept, and once the technology matures and the price becomes reasonable I suspect the new panels are going to make standard solar panels look a bit silly. The panels are known as PVT - photovoltaic thermal - and you get both electricity and hot water from them. The water keeps the PV cells at their optimum operating temperature, thus increasing their output. There's currently only one supplier in the UK but I suspect there are a lot of companies out there slapping their foreheads and racing to the drawing board.

I quite fancy a nice Caribbean home-knitted version myself :)

Re: Temperature

[johnrw.livejournal.com]

I wasn't aware that this had reached commercial deployment. Thanks.

Ah well, another idea makes the big(ger) time. I seem to run ahead of the curve:-) (I developed- well cobbled together - a pair of solar electric fencing units for the farm over a decade ago and in the past couple of years they've become a standard commercial option (at a silly money premium initially). ditto for several other technology trends. Mind you I might still play with a home brewed variant of PVT, just for the fun and experience.

(Now I wonder what other idea/gadget I've been playing with will be next! and can I actually get ahead and make some money off it? honestly? I doubt it.)

[johnrw.livejournal.com]

Re the split array. If the inverter was capable of handling the panels as two separate banks he would get better figures (this is doable as several off grid systems work this way) What's happening is a mismatch between outputs of the banks is working against him. (for the purposes of this post I'm ignoring the flyover shading problem) it's the equivalent of the shading issue writ large.

Putting the panels on East or West facing roofs will definitely reduce the efficiency - particularly in the winter as the ridge of the roof will shade the West roof until eleven or so if the roof is pitched at 30 degrees and past noon with steeper pitches. Again treating this as two smaller installations or separated banks would improve matters.

I'd like to see how real world figures compare with the theoretical models.

[uitlander]

The panels are set up as multiple strings. They are split into 6 separate strings IIRC to address exactly this issue. I do not have his generation figures, but am aware that they are significantly less than mine and that the greater E-W orientation is believed the be the major differentiator. I have visited his house and seen the setup, and frankly if it had been my house I wouldn't have done it because I dont think the site is appropriate for the return on investment. However, he's happy with his generation numbers, so I guess you pays your money and makes your choice.

[johnrw.livejournal.com]

Thank you for the additional information.

The greater East/West orientation would have quite a significant bearing, Personally I'd say 30 to 35 degrees either side of South is close on the practical limits financially speaking. 45 degrees is still yields significant usable energy but you'd have to accept a max of say 70 to 75% of optimum and very little in mid winter. Which pushes payback out another few years. Beyond that? well it depends on how much you're willing to pay for energy sufficiency (disclaimer I'm in a building with exactly East/West orientation and 30 degree roof pitch I'm not fitting solar up there any time soon particularly as it's the northern half of a semi and the neighbours have a large loft conversion)

[uitlander]

I've seen installations on garage roofs, separate from houses where the house is E-W oriented by the garage N-S.

The same installer is putting them on a nearby listed building in a College where he's having to hide them from view to meet listing requirements, and mount them on a temporary frame that's not affixed to the roof again to meet listing requirements. it seems that you can be quite innovative about it as long as you can run power to the site for the inverter.

There is one installation I have seen that faces directly west into the setting sun (I go past it on my bus ride home). I cannot see how the economics of that one work.

[johnrw.livejournal.com]

In pure economic terms it probably doesn't at best it's going to deliver maybe 50% of potential during summer and maybe a few kilowatts during the winter from the oblique light as the sun reaches the horizon. Sounds like a system which has been oversold.

Don't know whether the local planners would allow the hidden/temporary option around here, they threw fits over a modern plastic window in a Victorian building which replaced a rotten 1960's design because it was in a 'conservation' area It was harder to take because literally across the street the building has been boarded up await auto demolition from rain, woodworm and the tree in the chimney

[uitlander]

We're talking Grade 1 listed here. I think that as it's 1, hidden from sight and 2, a 'temporary' structure and not in any way attached to the fabric of the building they got it through. Or at least that's what I'm told by the gentleman who lives under the flyover and is the Bursar of the College concerned.

[watervole.livejournal.com]

does that mean six inverters? Surely not as the cost would be horrendous.

[uitlander]

No, one inverter capable of handling multiple strings. The inverter costs a bit more, but nothing like double the usual.

Mine are split between two strings on my roof handled by one inverter.

[johnrw.livejournal.com]

No, it means that the input/charge regulator stage of the inverter is capable of handling a mix of different input voltages and currents and turning it into a single flow for the inverter itself. This is probably (I'm not a power electronic engineer so take this with caution) an application of the MPPT Maximum Power Point Tech which is an integral part of modern charge controllers. Really ought to check this with an electronic or power engineer just to be sure I've got it right

[johnrw.livejournal.com]

Oops that should be MPPT Maximum Power Point Tracking tech

Solar calculators

[johnrw.livejournal.com]

Just been poking around (looking for the calculator I used before) and found the 'Photovoltaic Geographical Information System' of the European Commission Joint research Centre at http://re.jrc.ec.europa.eu/pvgis/

Also the Centre for Alternative Technology solar PV calculator, this is a bit more pessimistic than some calculators but possibly better for that, see

http://info.cat.org.uk/solarcalculator?gclid=CPCakJee3KsCFUVTfAodMyaONw

Hope it's useful, but I can't find the one I used before!

[johnrw.livejournal.com]

Start with the Carbon Trust website, also I found David Mackay's book "Sustainable Energy - without the hot air" well worth reading. It's a free download.

Don't know where you live, but 35 degrees off due south means peak generation would be about two and half hours before/after the local noon when the intensity is lower. At peak solar flux (noon +/-two) A panel orientation of 35 degree askew means peak generation would be approximately 80% of panel rating. At the latitude of Manchester (UK) panels facing within 15 degrees of South (on a 45 degree roof) would be expected to yield approximately 1000 kilowatt hours per year per kilowatt of installed capacity (Actually 982 according to one calculator). By far the bulk would be generated during the summer months (there being approximately a six to eight fold disparity between mid summer and mid winter).

Re subsidy I suggest you check out the Friends of the Earth website As it gives a far more detailed overview than I could write here.

If you can possibly afford it buy rather than the 'free' systems There are multiple reasons - some of which may be irrelevant to your situation.

The 'Free' systems will save you some money but the mismatch between generation and consumption timing means that unless you are home, or can program your appliances to take advantage in your absence, you will principally only benefit from the 'background load' fridge, freezer, standby for heating control systems and the like. (normally estimated as between 300 and 500 watts though personally I've tracked the background load here as approximately 3 kilowatt hours in each twenty four hour period) so the solar company benefit from the feed in tariff (based on energy generated - not what is fed back to the grid - currently around 36 pence per unit. Plus a further 4 pence per unit actually fed into the grid).

Finally, most systems readily available are direct grid tie systems with no local storage (batteries are heavy and expensive - to store a single kilowatt hour requires a 100 amp hour (at 12 volts) battery weighing around 40 kilograms). When the grid fails the inverter shuts down until external power is restored. This is for safety reasons (frying some poor engineer at a local substation would not be good). Systems with some battery and better engineered inverters/switching circuitry capable of operating in isolation are both more expensive to buy and install.

P.S. unless you're planning on staying where you are for at least the next five years don't do it - for some perverse reason houses with solar arrays are far harder to sell - even with the property priced at a discount to the local norm.

[watervole.livejournal.com]

Thanks John, that's a very informative reply. Especially the bit about why there's no solar power when the grid is down.

[birdsedge.livejournal.com]

Many thanks for all that.

[exmoor-cat.livejournal.com]

Capacitors?

[watervole.livejournal.com]

Not as easy as it sounds. There isn't much in the way of suitable batteries - and the yield is unlikely to be enough to power you through a whole day in any case, especially in winter.

[exmoor-cat.livejournal.com]

Also, worth reproting them to the Solar Trade Association - nice people, who certainly wouldn't want the industry to be hit with further PR problems.

[raspberryfool.livejournal.com]

I keep getting calls about government grants for loft insulation and cavity wall; I tell them I already have those, which I do, but they keep on calling. My normal response is fairly polite, but I feel my reserves of politeness running low. Maybe if I swear at them they'll get the message! :-)

[watervole.livejournal.com]

They're spammers. They're not calling from the government, they're touting for business.

Report them to the TPS (assuming you're registered with them).

Ask the caller what company they are. Get the caller's name if possible. If you can get their phone number, even better. Then go and fill in the TPS complaint form. (Just the company name will do at a pinch- that usually enables you to find the rest of the details on the web)