Solar PV advice sought

[misterfish]

We're trying to do what we can to go green in a sensible way. All the light bulbs are low energy cfl where possible, cavity wall is insulated, loft has almost 300mm insulation, central heating has gas condensing boiler with heating zones with programmable thermostats as well as all radiators having thermostatic valves, we have a large well insulated mains pressure hot water tank with a solar array on the roof. Our electricity supplier is a 'green' hydroelectric company.

So we were wondering about solar PV. We've tried looking around and found that any grants available are small compared to most of the rest of the EU and North America and are really questioning the cost effectiveness of these systems. If we were to spend about £15,000 on a mains connected system (where we sell back excess generation to the 'grid') would we be taking a sensible step? Apart from the 'feel good' factor and the possibility of being less reliant on external supply would we do better to save the money (with currrent derisory rates of interest) or 'invest' it in a PV system. We've got a south-west facing roof and are on the south coast in sunny Chichester, West Sussex.

Any comments or suggestions would be appreciated.

Misterfish

 

[MikeG.]

Hmmmmmmmm.....

I have been studying these things for 20 years, and take a professional interest, as well as a personal one, in all things "green". I am a huge advocate of super-insualtion, of mechanical ventilation systems with heat recovery, of low-embodied energy construction techniques, of wind turbines, and solar hot water systems etcetc.........but, I have very little time for photovoltaics.

I'm afraid that in our cloudy climate the enormous amount of energy that goes into their production can take up to 12 years to be re-paid in terms of output from the cells. Given that they have a reducing output over their life, and are generally thought of as having a working life of 20 to 25 years, you can see that they are currently extremely innefficient in energy terms in this country.

If you live on the continent, or in Canada, or Africa, Australia, the Middle East, etc.......then the numbers are entirely different.

The economics don't work either, hence the large subsidies.

My advice would be to invest in super-insulation, triple glazing, solar hot-water systems, draught proofing, mechanical ventilation systems etc, before you even consider photovoltaics.

Mike

 

[Jake]

Mike, you would know, if anyone - have you ever seen any data on the efficacy of IGU seals at retaining inert gas fills? I see loads of sceptical comments around about how fast the gas "must" dissipate, but never any proof.

 

[MikeG.]

I haven't seen any data, Jake..........but my experience is that different manufacturers seem to manage to get entirely different performance levels from the same construction and components.

Swedish window manufacturers, and Germans, seem able to make double and triple glazed units that last "forever", whereas many others, inc. a number of UK companies, using exactly the same spec, seem to have a high failure rate at 7 to 10 years. I have no figures to back this up, though, sorry.

Mike

 

[Jake]

I assume by failure, you mean (easily observeable) condensation?

If so, no need for much data!

It's those pesky invisible gases which can't be distinguished by eye.

 

[MikeG.]

Any failure of the gasket leading to the loss of the inert gases also leads, inevitably, to the intake of air. Now, whilst there is sometimes a dessicant within the units, this can only last for so long in relation to the quantities of moisture in air, and so any leakage of gas will soon lead to condensation.

So, the simple answer is.....yes!

Mike

 

[Jake]

Hmm, not sure you would necessarily see condensation in the absence of a pretty major seal failure, rather than just a bit of gas-permeability in the seal (after all the performance of an IGU with say a krypton fill will plummet if you lose 50% of the fill, and the dessicant ought to be able to deal with the moisture in the 50% of gap-volume of air that replaces it).

However, I have found an answer of sorts, as it seems there is now a (shortly to be compulsory) European standard, e.g:

Intercept Warm Edge Spacer Achieves BS EN1279 Part 3

Intercept Spacer Systems have now passed BS EN1279 Part 3, the section of the standard that deals with insulating gas leakage.

The leakage rate called for in the Standard is set at 1% per year. The GED manufactured Intercept units achieved remarkable results at better than half the requirement.

 

[tnimble]

I would certainly not consider going the photovoltaic route except for as just to experiment if you have really deep interests in that (and deep pockets)

The only effective means of generating electricity from solar engergy is going the CSP route. This means to collect, focus, heat capture, convert heat into electricity. There are two paths to do this. Use hollow mirrors to collect and focus the light on a glass tube filled with water / steam that is super heated. The super heated steam drives a turbine. The other way is to use Fresnel lens capped cells. The first takes up lots and lots of space and can only be done on very large scale. The second method is scalable but still expensive and hard to obtain in small quantities.

The large two drawbacks with photovoltaic panels already mentioned like:
- costs more than they will provide over their life cycle
- production and recycling costs of the panels uses many resources whch contributes largely to the above

To this can be added:
- if for climate change, using solar energy contributes to warming the planet. All the effectively produced energy warms the planet at the point of consumption (the heat given off the a bulb, a telly, the fridge etcetera). The system itself is not 100% efficient (far from it) only a small amount of the losses of the 'system' are reflected light the rest is heat production. Most surfaces of the earth have high solar energy reflective properties in comparison. *

*) The human contribution to climate change is debatable to say the least and tiny in comparison to the contribution of natural processes like volcanic activity, rotting vegetation, solar activity, variations in the density or space, distribution of rain fall.

 

[wizer]

I asked about this before and got the same answer. Which is a shame because I really like the idea of free electric, as opposed to free warmth. i.e I use a lot of electric.

So what about other methods of cheap or free electric? Wind?

 

[big soft moose]

I asked about this before and got the same answer. Which is a shame because I really like the idea of free electric, as opposed to free warmth. i.e I use a lot of electric.

So what about other methods of cheap or free electric? Wind?

at the moment - unless you have a very fortuitous location (like my mate ben who bought an old watermill in ireland and installed a turbine to run off the wheel) there is nothing that really works for "free" power (except illegally wiring in to a streetlamp - and i would not advocate that route) or more acurately there are workable solutions but the capital cost is such that repayment will take many years.

of course that is a todays energy costs - if the unit price went up dramatically as fossil fuels run short then the renewable option would look much more affordable.

 

[wizer]

(except illegally wiring in to a streetlamp - and i would not advocate that route)

Wistfully looks out the window at the street lamp that keeps him up at night...

Actually I have seen this happen on a couple of occasions. Trying to remember the first, but the last time I saw it was on my old allotments. The guy was digging one day and found the cable from the perimeter lamp. Some how he managed to spur off it into his shed. Got caught when he was using an electric strimmer one day :lol: :lol:

 

[MikeG.]

The human contribution to climate change is debatable to say the least and tiny in comparison to the contribution of natural processes like vulcanic activity, rotting vegetation, solar activity, variations in the density or space, distribution of rain fall.

This is a blatant attempt to stir up controversy. Out of the woodwork will come all sorts of strange comments, now. This idiotic argument should be turned on its head by asking...........how is it that we can have altered the chemistry of the atmosphere so much, and, as it now turns out, the oceans as well, without it having any effect?

Don't hijack threads.

Here is a chap wanting advice on PV's..........please start a new thread in Off Topics with a clear title if you want to start this nonsense all over again. I wont be contributing.

Sorry for being so hot under the collar about this, but this is half a lifetime's work for me, and I can't even begin to understand the mentality of flat-earthers who disregard all of the science.

Mike

 

[TrimTheKing]

and the dessicant ought to be able to deal with the moisture in the 50% of gap-volume of air that replaces it).

Just a thought but, what about when the dessicant is 'full'?

My wife is the CFO of the worlds biggest manufacturer of silicates, and I was talking with their OPS director down the pub one day asking if he could get me a few bags for use around the workshop. His comment was that it isn't the right thing to use because it is just like a sponge, when it's full it stops soaking up any more water until it has dried out.

Slight deflection from the topic (and not relevant to windows) but his advice was a dehumidifier, which I now have, and a hygrometer which tells me the RH in the workshop and outside.

To caveat this, I am speaking from what I was told, not with any level of authority based on my own understanding.

Cheers

Mark

 

[TrimTheKing]

vulcanic activity

What has Mr Spock got to do with any of this?

Sorry, had to.

Cheers

Mark

 

[Jake]

and the dessicant ought to be able to deal with the moisture in the 50% of gap-volume of air that replaces it).

Just a thought but, what about when the dessicant is 'full'?

Well, at that point the window starts to fail ... but by that point the original fill gas really must be long gone unless the dessicant is extremely ineffective, surely?

edit: anyway this is all well OT, so apologies to the OP for the diversion.

 

[tnimble]

So what about other methods of cheap or free electric? Wind?

Wind is one (although the effectiveness increases when the wind is captured at greater height (about 160 meters and higher) and at lower blade rotational speed, for this the blades needs to have the blades aligned not only with the wind direction but also the pitch of the blade with the wind speed.) For home usage a small horizontal wind turbine can be used, but vertical wind turbines can be used in more residential areas.

Water energy from flowing water like rivers has great potential for small scale usage. Utilisation on larger scale often has too much impact on the surrounding environment and water transportation.

Is you would happen to life in a very active area (Geysers, hot gas vents and those kinds of phenomena) one could use this to drive a steam powered generator. Since these areas are not quite residential most of these projects are large scale. Experiments are done to gather energy more directly from the earth its core.

Also a generator could be run on swamp or bog gasses. This has much potential in some areas to be utilised on small scale on a per house basis.

Other methods like full cells have large disadvantages like the PV panels.

This is a blatant attempt to stir up controversy. Don't hijack threads.

Sorry it wasn't meant like that, it was only a footnote (hence the asterisk).

This idiotic argument should be turned on its head by asking...........how is it that we can have altered the chemistry of the atmosphere so much, and, as it now turns out, the oceans as well, without it having any effect?

Please don't put words in my mouth/fingers. We do mayor harm to and exploit our environment and Earth its inhabitants in a gazillion ways. The comment is only and only applicable to climate change as in global temperatures.

And I would request indeed not to go into any discussion about CC.

 

[dickm]

Aberdeen Univ is running a series of seminars on "Energy Controversies" at the moment. Last night's was on Alternative energy sources, and one suggestion, among a lot of others, was that solar PV, particularly using large array of solar tiles, was "becoming economic". I used to work with the guy who made this prediction, and he is a bit of an optimist, but does have his finger on the pulse in this area. So possibly worth looking out again soon.

According to the panel on this occasion, tidal, wave and wind are the most likely big sources in the near-ish future, but only if Govt can be prepared to back the start-up costs rather than pouring money into *ankers' pockets.
Not that most of us can use tidal or wave!

Solar thermal (whatever recent reports have said) does seem to be economic now, especially if combined with heat storage (i.e. basically, a d*** great hot water tank). We are probably going down this route shortly, so will report back next year.

 

[dickm]

Just thought I'd update this thread, as there doesn't seem to be anything more recent on PV around the forum.
Having looked at the sums regarding the Feed In Tariff, they seem too good to be true, so I've broken the rules of a lifetime, and become an early adopter of new technology. We've just had 3.9kW nominal output PV panels installed on the roof, and in two nice sunny days, had pretty reasonable generation. The shine (literally!) rather taken off on the last couple of days when Aberdeenshire went dreich, with a cloud base just above the trees, so generation has been pretty negligible.
But talking today at a meeting to one of the other (2? 3?) folk who have PV installed round here, it looks as if even with our weather the investment will be better than most other opportunities. Our kids should recoup the investment anyway when they pop us into boxes and sell the house.

 

[misterfish]

As the OP (from over 18 months ago) I'll also add our update.

When we saw the Feed in Tariff rates for PV we also thought it might be worth pursuing, so we started investigating the feasibility/options back in March. This is not a DIY option but has to be installed by approved contractors using approved equipment so it isn't a cheap 'on a whim' purchase.

Anyway, we finally ended up with a 3.25KW notional power system that was installed in August. The actual maximum output of mains power we get is 90% at just over 2.8KW - so far we have generated just over 500kW.

The system has rendered the old Electrisave (OWL) energy monitor useless during the day as there is no way to tell if the total displayed is usage or export.

If anybody is interested in more details then let me know - (I have also been recording daily power production (my scientific/geeky nature).

Misterfish

 

[RogerS]

What's the revenue return so far, misterfish?