Solar Panel Guide Discussion

zeupater

alterego wrote: »

Not to me, but here are some newer ones..

http://notrickszone.com/2011/07/04/weed-covered-solar-park-20-acres-11-million-only-one-and-half-years-old/

Clearly this is an extreme example, but solar panels do need to be kept clean, which isn't always easy if they're on the roof. The cells in a panel are connected in groups in series, which means that if one gets obscured, the whole group stops working. I know this because years ago I was involved with their deployment offshore, where the power output was regularly affected by seagull droppings...

I don't often agree with George Monbiot, but even he's opposed to solar power:

http://www.guardian.co.uk/environment/georgemonbiot/2010/mar/11/solar-power-germany-feed-in-tariff

Hi

I don't think that most who have invested in pv would let the weeds grow that high in their gutters ....

Anyway, your exposure to pv was, as you say, years ago and therefore could be considered to be a little outdated. Modern panels do not suffer as badly from the issue you describe. With most decent makes, each panel is fitted with bypass diode circuitry to exclude a failed or fully shaded panel from the series string and the panel is protected against partial shade causing total bypass through zoning groups of cells in the panel with other diodes. The result of this approach is a remarkable increase in performance where failure or partial shade conditions exist .... although there are a number of installers who don't really understand the benefits of using the direction of the groups to their customer's advantage ....

What also needs to be considered is that in offshore situations the absence of land results in a heavy concentration of seabirds, which therefore concentrates the issue .... the result being an example which is totally irrelevant to everyone who doesn't live on an oil platform or lightship :D

HTH
Z

zeupater

grahamc2003 wrote: »

Thanks. i don't know what their original estimate of savings was, but I'd like to see their reasoning of how they worked out £70pa and secondly the evidence and reasoning they used to up that estimate to £90 to £180.

Seems to me that one of those figures must have been plucked out of the air. Certainly their credibility has dropped imo, simply because it's proof they don't mind advising people with information they haven't estimated by some sort of verifiable evidence based means (at least one of their estimates is wrong by a large margin).

The problem is, in all likelyhood, they have no one suitably qualified (that is, a Chartered or European Engineer) to examine whatever scientific data or other reliable evidence they do hold, and make a reaonsable deduction from that. I'm afraid that is a typical situation these days with 'green' organisations.

They say 'the percentage use could be 50% for some users'(or similar). That is correct, as is the statement 'the percentage use could be 100% for some users' - it would certainly be very easy to arrange. But saying those are 'typical' percentages is a different matter and, from my work in the esi over many years, I'd say a 50% usage is not typical at all.

Still, I hope the Energy saving trust will detail the calculations and rational for their new estimates, and also explain the calcs and rational of their previous estimate and why it was so incorrect relative to their new estimate.

Hi

The issue is that the EST have changed their estimates and published the change, however, they've just been lazy and not reviewed all of the previous articles which are on their site and updated them (typical public sector ) ....

To make it worse this has been an issue for a while ... for example (July) ...

zeupater wrote: »

Hi

That's old information, the EST now base their average electricity saving advice on a £70/year saving based on 75% of generation being exported on a 2.7kWp system ..... they just need to update the abovementioned webpage to bring it inline with current advice ... (link £70/75%) http://www.energysavingtrust.org.uk/Generate-your-own-energy/Sell-your-own-energy/Feed-in-Tariff-scheme#howitworks

If the householder is at home all day I believe that working on a £100/year saving is nearer the mark ...

HTH
Z

Someone really needs to get in there and shake the EST up a little, most of the information which they do provide is of little use because of the way it's presented and what looks to be useful is likely out of date .... apart from that I wonder what the FSA would think of inconsistent or incorrect financial advice being given .... .

HTH
Z

keith_r59

alterego wrote: »

Clearly this is an extreme example, but solar panels do need to be kept clean, which isn't always easy if they're on the roof.

My own experience indicates that normal rainfall does an acceptable job of keeping my panels sufficiently clean to maintain their performance.

However, if I see a significant drop in performance I will use my water fed telescopic window cleaning pole to give them a little wash.

orrery

grahamc2003 wrote: »

The problem is, in all likelyhood, they have no one suitably qualified (that is, a Chartered or European Engineer) to examine whatever scientific data or other reliable evidence they do hold, and make a reaonsable deduction from that. I'm afraid that is a typical situation these days with 'green' organisations.

Well, I'm both a CEng and a EurIng and I wouldn't attempt to make any estimate of what I'll achieve when my system is installed in 3 weeks time. There is a grave danger when presenting such estimates that the truth can be very misleading for those that don't understand what it means, so is likely to be very conservative.

The payback is so variable and depends on so many dynamic variables - including how serious an effort you (or in my case, my wife) are going to make to maximise it.

zeupater

keith_r59 wrote: »

..... However, if I see a significant drop in performance I will use my water fed telescopic window cleaning pole to give them a little wash.

Just remembered, I've got on of those too .... found it was better at drenching the armpits than cleaning the windows so it was only used a few times, but it'll still be in the garage somewhere if needed ....

Z

alterego_2

I think people's usage patterns will vary so much that it's impossible to give a sensible figure. Still, if you get the FiT both for supplying the grid and for using it yourself, then presumably it doesn't matter too much? Encouraging people to use their tumble driers on sunny days probably isn't ideal though.. :-)

Cardew

grahamc2003 wrote: »

Thanks. i don't know what their original estimate of savings was, but I'd like to see their reasoning of how they worked out £70pa and secondly the evidence and reasoning they used to up that estimate to £90 to £180.

Seems to me that one of those figures must have been plucked out of the air. Certainly their credibility has dropped imo, simply because it's proof they don't mind advising people with information they haven't estimated by some sort of verifiable evidence based means (at least one of their estimates is wrong by a large margin).

The problem is, in all likelyhood, they have no one suitably qualified (that is, a Chartered or European Engineer) to examine whatever scientific data or other reliable evidence they do hold, and make a reaonsable deduction from that. I'm afraid that is a typical situation these days with 'green' organisations.

They say 'the percentage use could be 50% for some users'(or similar). That is correct, as is the statement 'the percentage use could be 100% for some users' - it would certainly be very easy to arrange. But saying those are 'typical' percentages is a different matter and, from my work in the esi over many years, I'd say a 50% usage is not typical at all.

Still, I hope the Energy saving trust will detail the calculations and rational for their new estimates, and also explain the calcs and rational of their previous estimate and why it was so incorrect relative to their new estimate.

It wouldn't even need the consumption to be estimated if they did some trials of houses with export meters fitted: i.e. generate 3,000kWh pa, export 2,000kWh pa means(if my arithmetic is correct!) 1,000kWh pa used in the house.

The other point is that even some while ago the EST used the figure of 14p/kWh for savings, which was the approved figure taking the total price of electricity taking into account standing charges/tier 1 price; the figure is possibly above 14p now. Savings should be calculated using the tier 2 price only.

It seems to me that the EST are reluctant to give explanations on how they derive estimates. They appear to feel their role is to encourage anything 'green' regardless of its cost effectiveness.

Examples:

1. Solar thermal.

Despite a Government funded trial of lots of systems that gave an average annual output of 1,000kWh(worth about £40 if you have gas and £50 with off-peak electricity) they are not prepared to say spendin £thousands on such a system is madness.

2. Small wind turbines

An extensive trial that showed they were a complete waste of time, with many using more electricity than they generated. Again no warnings and condemnation.

3. Air Source Heat Pumps

They commissioned a trial of 29 ASHP systems, the results of which were disappointing to say the least. No technical data given about the individual systems - not even the manufacturers or installers(for fear of upsetting the manufacturers?)

It is quite clear that someone spending many thousands of pounds on an ASHP is just taking 'pot luck' if he gets a poor or good system.

Yet no general 'health warning' from EST.


4. 'Silver paper panels' behind radiators.

Despite outrageous claims of savings being queried on MSE with the EST, they refused initially to refute these claims. Long story, but when absolutely pinned down with evidence from a report they themselves had quoted, they conceded that they might save a few pence per year(for the whole house) if used on a cavity wall and a couple of pounds on solid walls.

People should be able to turn to the EST for objective advice. IMO they lose all credibility if they continue with the 'Green is Good' approach.

whasup

Cardew wrote: »

They appear to feel their role is to encourage anything 'green' regardless of its cost effectiveness.

Agree. Not sure about the greenness though. It amazes me the scant evidence needed to convince the eco industry of the greeness of something. For example, what plans are being made for the disposal of solar panels and who will cover the cost? (don't underestimate that - it's likely to be a massive sum of money) Obviously I know who will cover the cost - it will be us of course. Add wind turbines to the mix and the future looks anything but green.

keith_r59

whasup wrote: »

Agree. Not sure about the greenness though. It amazes me the scant evidence needed to convince the eco industry of the greeness of something. For example, what plans are being made for the disposal of solar panels and who will cover the cost? (don't underestimate that - it's likely to be a massive sum of money) Obviously I know who will cover the cost - it will be us of course. Add wind turbines to the mix and the future looks anything but green.

I would imagine that like all waste these days strenuous efforts will be made to re-cycle them.

http://www.pvcycle.org/

alterego_2

Cardew wrote: »

People should be able to turn to the EST for objective advice. IMO they lose all credibility if they continue with the 'Green is Good' approach.

I quite agree, Cardew. The elephant in the room is CO2, which is pretty harmless (and keeps plants alive) and has been at much higher levels prehistorically, with no ill effect. Indeed, CO2 levels tend to follow temperature, not precede them, but as long as the myth that it causes climate change persists, we are stuck with daft policies that try to limit it.

Incidentally, most people don't know the difference between CO and CO2, and having heard that CO is poisonous, readily get the two confused...