Solar: how much you paid (£) how much you have generated (kWh) and date of install.

zeupater

Sterlingtimes wrote: »

... Would you suggest that the under-powering of my inverters only serves to limit the peak output in the picture below where the curve is flattened? In other words, where the "curve is a curve" the only loss imposed by the inverter is the "efficiency loss", e.g. 97%.
So if each of my inverters where half the power again, where the "curve remains a curve", I would see no difference, i.e. there would be a a few more flattened bars but everything else would be unaltered ...

Hi

Without a scale and associated data it would be hard to say whether it's temperature, irradiation, capping or even the resolution (rounding) of the chart scale ....

... To give an example, I've just analysed the generation from our system for 6/6, which was just above a 7kWh/kWp day ...

In cool conditions with cloud-edge our system can peak at 10% above nominal for a short time before the inverter ramps back and then panel temperatures ramp-back even further - it was observed to be doing this on Saturday as intermittent clouds passed overhead, however, with data recorded in 5 minute intervals these peaks never show ... here's a breakdown of the total (5 minute interval) recorded generation above the 50%kWp threshold ....

Above : %Generation
95% : -
90% : 0.9%
85% : 3.0%
80% : 5.4%
75% : 8.7%
70% : 11.5%
65% : 14.4%
60% : 17.9%
55% : 22.5%
50% : 27.1%

... meaning that on an excellent day, 72.9% of the total was still generated below 50% of the system's nominally rated kWp .... of course, there is still the inherent inaccuracy from recording in 5 minute time-slices, but the effect of accounting for this is likely to be no different unless calculating the above to (at least) a second decimal position ...

HTH
Z

cepheus

zeupater wrote: »

Hi Cepheus ..

I don't know what you're attempting to do here .... effectively, if someone is currently looking to install a system it's the performance in terms generation, the current system price and FiT returns which they'd be interested in, not the price that someone paid five-or-so years ago and the return on those systems ...

If you're looking for data, then why not look for masses of data ... PVOutput ( http://pvoutput.org/ ) has somewhere around 20,000 systems registered globally, with a couple of thousand being in the UK, of which around 300-400 submit data on a live basis in timeslots down to every 5 minutes. You may even find that some have registered their installation dates & system prices ...

If you want to compare, it's all there to cut&slice it as you want .... nothing hidden and I doubt that anyone would have the time or inclination to sit and fiddle the figures ... pick a system local to yourself with a roof which faces the same direction and has a similar inclination and check the monthly output against either the SAP figures upon which installers base the estimates on quotations or compare it against PVGIS ( http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php ) which is the EU's official calculator ....

As for area, no problem there either, I fail to see the relevance but here goes .... Panels are around 15% efficient at converting light to electricity at a standard unit temperature of 25C and a 250Wp (15%Efficient) unit will be around 1.6sqm (1.6mx1m), with inverter efficiencies being around 95% - UK insolation is somewhere around 1000kWh/sqm per annum ( http://re.jrc.ec.europa.eu/pvgis/cmaps/eu_cmsaf_opt/G_opt_UK.png ) .... armed with this you can play with the figures however you want ...

... for example, take a 4kWp system facing south somewhere in 'average' UK in an 'average' year .... 1sqm of roof would receive 1000kWh if insolation, the panels would convert this to 150kWh of DC (1000x15%), which after system losses would be ~142.5kWh of AC (150x95%) ... 16 panels rated at 250W would make 4kWp and would cover ~25.6sqm(16*1.6) ... 25.6sqm should therefore, on average, generate 3648kWh per year (25.6sqm*142.5kWh) which, considering the simplicity of the calculation, is in line with what people are actually seeing ....

There's the physics and the resources, play with them as you will ...

HTH
Z

Thanks, I'll take a look.

I'm trying to cut through all the manufactures hype to see what their performance is in practice, and how competitive and cost effective they are as a serious means of supplying electricity for our economy.

The problem is, that manufacturers and installers (generally) can compromise the quality to attain low prices for anything. If they haven't with photovoltaics they must be less susceptible than with other types of energy saving measure such as insulation and double glazing for example. I certainly wouldn't accept theoretical figures for these. Neither do we know how well these systems would work in ten years time, and how much maintenance is necessary. Therefore, I'm a bit reluctant to assume a current price and brand new performance for an estimate of a 25 year system.

If they have a 25 year warranty perhaps that provides some confidence they are durable, but who is guaranteeing it, the company? What if they go bust?

Martyn1981

cepheus wrote: »

Neither do we know how well these systems would work in ten years time, and how much maintenance is necessary.

First UK grid connected PV system 95% efficient 20 years later

The inverter lasted 14 years, though the article refers to an upgrade, so not clear if it failed or not.

Mart.

zeupater

cepheus wrote: »

Thanks, I'll take a look.

I'm trying to cut through all the manufactures hype to see what their performance is in practice, and how competitive and cost effective they are as a serious means of supplying electricity for our economy.

The problem is, that manufacturers and installers (generally) can compromise the quality to attain low prices for anything. If they haven't with photovoltaics they must be less susceptible than with other types of energy saving measure such as insulation and double glazing for example. I certainly wouldn't accept theoretical figures for these. Neither do we know how well these systems would work in ten years time, and how much maintenance is necessary. Therefore, I'm a bit reluctant to assume a current price and brand new performance for an estimate of a 25 year system.

If they have a 25 year warranty perhaps that provides some confidence they are durable, but who is guaranteeing it, the company? What if they go bust?

Hi

Then you're exactly where I was regarding grid-connected pv systems about 6 years ago ! ... in the intervening time I've seen little to be too worried about. On panels the only 'iffy' manufacturer claims seem to be when comparing relative efficiencies outside the standard controlled flash-test (1000W/sqm @ 25C ) and relative degradation profiles (straight line vs step change). Overall the UK market seems to have decent protection against poor product through the MCS certification requirements in order to qualify for FiT ... if there is a potential for future issues it's probably more likely that it will manifest in cheaper mounting systems and/or inverters.

In emerging technologies there are manufacturers intent to maximise returns at all costs and there are ones with brand names and reputations to protect, so for peace of mind it might be better to stick with those with track-records and a broad technology base, but then again, at the moment, who knows ? ...

As Mart mentions in the above post, there are systems which have been around for years, after-all the technology isn't new, just the scale of production & installation .... some time ago there was a discussion on these boards which referenced a paper on longevity and degradation which included a remote system in a pretty harsh environment (Africa?) which had been running continually since the mid '70s ....

Regarding pv performance claims being seen as similar other 'iffy' products, well, unlike the 'official' MPG figures for cars the estimates for annual system generation stand up well and in most cases are reported to be accurate or bettered by a significant degree, there's also the ability with most systems to monitor & record performance down to a tremendous level of detail .... With the double glazing and insulation you mention there's very little you can actually do to monitor to an accurate level, therefore theoretical and long-term trend is all that's generally available .... it's currently 10:50(BST) and my system is generating 2.02kW with the house consuming 190W, whereas both the level of solar gain through the windows and heat-loss through the heavily insulated structure is unknown, apart from a modelled theoretical calculation ...

Regarding 'Neither do we know how well these systems would work in ten years time, and how much maintenance is necessary.' ... well, actually we probably know more than you would give credit. As already mentioned, the technology isn't new, it's just manufactured on a much larger scale, bringing in volume related manufacturing economies. Ten years ?, well our system is half of that already and 4 of the best 20 generating days have already been recorded this year, so unless the panels are removed from our roof and subjected to the same condition controlled flash-test as they were when manufactured any degradation-to-date must be considered in our case to be negligible, despite a film of dirt/dust which has accumulated ...

HTH
Z

zeupater

zeupater wrote: »

... Ten years ?, well our system is half of that already and 4 of the best 20 generating days have already been recorded this year, so unless the panels are removed from our roof and subjected to the same condition controlled flash-test as they were when manufactured any degradation-to-date must be considered in our case to be negligible, despite a film of dirt/dust which has accumulated ...

Correction, including today it's now 5/20 ....

cepheus

This was written back in 2006 so perhaps the inverter issues are solved now. It demonstrated that PV systems couldn't be just left without periodic checks. Hence my questions regarding real in service performance are very reasonable. Unfortunately, those who have lost interest in their hobby won't check or report. This (in addition to economies of scale) is another advantage of a PV array being operated by a professional business outfit.

Regarding installation and commissioning, there appears to be a multitude of short-cuts a dodgy outfit could use.

https://www.bre.co.uk/filelibrary/pdf/rpts/DFT_GoodPracticeGuidePart2_DTI.pdf

Sterlingtimes

cepheus wrote: »

It demonstrated that PV systems couldn't be just left without periodic checks.

Does any other equipment need periodic checks? Perhaps, cars, boilers, pressurised water cylinders, washing machines, kettles, ice-cream makers, hairdryers ...

In a "cotton wooled" world, everything could need periodic checks.

zeupater

cepheus wrote: »

This was written back in 2006 so perhaps the inverter issues are solved now. It demonstrated that PV systems couldn't be just left without periodic checks. Hence my questions regarding real in service performance are very reasonable. Unfortunately, those who have lost interest in their hobby won't check or report. This (in addition to economies of scale) is another advantage of a PV array being operated by a professional business outfit.

Regarding installation and commissioning, there appears to be a multitude of short-cuts a dodgy outfit could use.

https://www.bre.co.uk/filelibrary/pdf/rpts/DFT_GoodPracticeGuidePart2_DTI.pdf

Hi

Really can't see much in the report - plan the installation, buy a decent inverter with analytics & error reporting, watch out for shade, grid overvoltage could cause problems, connectors could corrode (but shouldn't) & panels could get dirty or vandalised .... it make you wonder how much the report cost to produce ....

We really need to place domestic systems into context .... the maximum power under ideal conditions isn't that much different to a kettle, microwave combination oven, single electric oven, a couple of rings on a hob or an electric immersion heater .... so the question revolves around the preventative maintenance regimes which are in place for the installations of any of these ?? .... Our inverter (SMA) provides masses of data regarding performance and error conditions are reported & logged, both on the inverter display (which the report mentions) and on a remote display which bleeps if it wants to tell me anything .... With two MPPTs you can monitor for an imbalance in generation caused by a panel problem or even corroded connectors just by comparing output from each array, with optimisers or micro-inverters you can even monitor the condition of individual panels ....

If you have grid overvoltage, as detailed as an example in the report, then the inverter will shut down until grid conditions return to in-tolerance conditions. High voltage conditions mainly exist where a property is on a long line and close to a transformer or substation, such as in a rural environment - in these cases the voltage will be 'tweaked' so that someone at the furthest point on the line still has their supply within tolerance .... I'm sure that anyone experiencing generation figures as low as the example in the report would at least notice that the FiT payments were low, or soon notice that the inverter is bleeping on a regular basis and displaying error conditions - finding a way to report this to the DNO for rectification would be pretty straightforward for most ...


HTH
Z

Martyn1981

cepheus wrote: »

This was written back in 2006 so perhaps the inverter issues are solved now. It demonstrated that PV systems couldn't be just left without periodic checks. Hence my questions regarding real in service performance are very reasonable. Unfortunately, those who have lost interest in their hobby won't check or report. This (in addition to economies of scale) is another advantage of a PV array being operated by a professional business outfit.

Regarding installation and commissioning, there appears to be a multitude of short-cuts a dodgy outfit could use.

https://www.bre.co.uk/filelibrary/pdf/rpts/DFT_GoodPracticeGuidePart2_DTI.pdf

You seem to be putting a lot of effort into anticipating/projecting problems with PV generation. I hope you are treating wind generation with the same skepticism.

But, back to your statement that PV isn't as cost-effective as wind, are you any closer to explaining that position yet?

I'm getting a few hints from some of your posts that you may try to twist the statement into supply side wind v's demand side PV, rather than the simple method of comparing current subsidies of wind and PV on each scale?

Alternatively, you could just say that you hadn't realised that PV had caught up (or in same cases overtaken) wind so soon, and that regardless of older assumptions, this can only be good news for UK renewables.

Mart.

Sterlingtimes

Concerning wind power, there's on old saying in engineering circles, "it's the volts that jolts but the mills that kills". Also wind turbines can fall down and kill people and they kill lots of birds.

At least wind turbines don't need regular maintenance audits. Do they?