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1961Nick

zeupater wrote: »

:think: .... Odd, how do you define inefficient ?? ....

Inefficient for the occupier.

An old 2kW array may be great for the 'Rent a roof' company receiving over 40p FIT, but that same area would now accommodate a 3-4kw system.

zeupater

1961Nick wrote: »

Inefficient for the occupier.

An old 2kW array may be great for the 'Rent a roof' company receiving over 40p FIT, but that same area would now accommodate a 3-4kw system.

... so two measures then ...

'inefficient for the occupier' to me would logically mean that the occupier was inefficient in using what's being generated, ie, only consuming ~25% of total generation? ... as for the panel efficiency in terms if generation per unit area - I doubt that many 'rent-a-roof' companies would have installed amorphous silicon panels and that's probably the only technology which you could replace and double generation for any given area. The majority of pv panels installed are likely to be around 13%-14% efficient by area, with high efficiency hybrid panels being about 19%, so the potential would be around 40% greater generation on the same area ... however, the cost, when measured in either £/Wp or £/area becomes higher, so a less efficient use of capital .... In terms of the efficiency of panels which were generally available when the FiT was introduced and what you can get today there's been little change in the technology/efficiency of panels, inverters, mounting systems or cables, the only real change being price ...

HTH
Z

1961Nick

zeupater wrote: »

... so two measures then ...

'inefficient for the occupier' to me would logically mean that the occupier was inefficient in using what's being generated, ie, only consuming ~25% of total generation? ... as for the panel efficiency in terms if generation per unit area - I doubt that many 'rent-a-roof' companies would have installed amorphous silicon panels and that's probably the only technology which you could replace and double generation for any given area. The majority of pv panels installed are likely to be around 13%-14% efficient by area, with high efficiency hybrid panels being about 19%, so the potential would be around 40% greater generation on the same area ... however, the cost, when measured in either £/Wp or £/area becomes higher, so a less efficient use of capital .... In terms of the efficiency of panels which were generally available when the FiT was introduced and what you can get today there's been little change in the technology/efficiency of panels, inverters, mounting systems or cables, the only real change being price ...

HTH
Z

However....panels have got smaller for a given output & that could easily make the difference between 2 rows & 3 rows of panels (50% increase). Add in an extra column or two & a given area (roof) that a few years ago could generate 2kW may now be able to make 3-4kW.

Returning to the original point.....would I pay more, less or the same for a house with an early 'rent a roof' array? Probably less & that would depend on how much it cost to be released from the contract.

Some of those early installations were pretty ugly & being tied to one for the next 15 years might be an issue for some house buyers.

zeupater

1961Nick wrote: »

However....panels have got smaller for a given output & that could easily make the difference between 2 rows & 3 rows of panels (50% increase). Add in an extra column or two & a given area (roof) that a few years ago could generate 2kW may now be able to make 3-4kW ...

Hi

If there's been no major difference in the efficiency of a cell over the past 4 years-or-so, then how can "panels have got smaller for a given output" ... 5 years ago there were panels rated at various power levels, for example 180W and 230W, which used the same cells, just a different number, and were therefore different sizes ... nothing has really changed ...

As for high efficiency panels, Sanyo made hybrid panels when FiTs were introduced and still do, it's just that Panasonic bought their pv business ... panel efficiencies may have improved a little due to manufacturing process improvements, but that's just reflected in the panel rating - for example, manufacturers now offer panels rated at 250W which are exactly the same physical dimensions as what would have previously been made/tested/offered at a lower rating (say 235W) ...

HTH
Z

ed110220

1961Nick wrote: »

Inefficient for the occupier.

An old 2kW array may be great for the 'Rent a roof' company receiving over 40p FIT, but that same area would now accommodate a 3-4kw system.

As far as I know, almost all the rent a roof schemes were for 4 kW systems as the smaller systems are more expensive per watt as the fixed or nearly fixed costs such as labour, scaffolding etc are the same. The rent a roof companies could and did choose just the roofs that faced close to South and had enough room for 4 kW of standard efficiency panels. Can't see why they would take such a roof and only put 2 kW on.

Higher efficiency panels have been available for some time which would typically allow 4 kW from the same area as 3 kW of standard panels, or 5.3 kW from the area of 4 kW, but they are significantly more expensive per watt.


Ed

1961Nick

Z & Ed, you must live in areas with big houses. Lots of arrays up north are limited by the physical dimensions of the roof. There are plenty of older 'Rent a roof' arrays under 3.0kW. The 40p+ FIT meant they were economically viable at that time. As time progresses more roofs can hit the 4.0kW target.

There was also the tendency to fit panels any which way just to get an extra one in - regardless of aesthetics.

To clarify my original point (I seem to have to do this a lot) - Today you can get more kWh on a roof than you could 5 years ago.

ed110220

1961Nick wrote: »

Z & Ed, you must live in areas with big houses. Lots of arrays up north are limited by the physical dimensions of the roof. There are plenty of older 'Rent a roof' arrays under 3.0kW. The 40p+ FIT meant they were economically viable at that time. As time progresses more roofs can hit the 4.0kW target.

There was also the tendency to fit panels any which way just to get an extra one in - regardless of aesthetics.

To clarify my original point (I seem to have to do this a lot) - Today you can get more kWh on a roof than you could 5 years ago.

Not especially, they are very standard local authority houses of the 1940s-50s. They do have the advantage for solar that the roofs are simple pitched with a gable at each end so no hips or anything complicated.

I'm rather surprised as I did look into it on behalf of my parents, who live in an older terraced house with a more complicated roof and less usable space (typical Victorian terrace with the roof in two parts, one over the main part of the house, and the other over the kitchen and bathroom sticking out at the back), and at the time (about three years ago) none of the rent-a-roof crowd were interested in anything under 4 kW. Do you know for certain that these are rent a roof?

I don't think you need to convince anyone here that rent-a-roof is not necessarily a good thing though!

Ed

ed110220

One nearby by A Shade Greener (rent-a-roof):-

zeupater

1961Nick wrote: »

Z & Ed, you must live in areas with big houses. Lots of arrays up north are limited by the physical dimensions of the roof. There are plenty of older 'Rent a roof' arrays under 3.0kW. The 40p+ FIT meant they were economically viable at that time. As time progresses more roofs can hit the 4.0kW target.

There was also the tendency to fit panels any which way just to get an extra one in - regardless of aesthetics.

To clarify my original point (I seem to have to do this a lot) - Today you can get more kWh on a roof than you could 5 years ago.

Hi

Maybe the issue around clarification is related to the possibility that the point is incorrect .... ??

I agree that many installations are sub 4kWp ... discussions we were having on these boards 4/5 years ago seemed to suggest that RaR installs averaged (from memory) something like 3.0/3.3kWp at the time and the roof area would have been a major contributing factor, as would the efficiency of standard poly-crystalline panels ... Because there's effectively an oversupply condition on applicants, RaR scheme operators were/are able to pick & choose where they install in order to maximise returns and therefore have no need to maximise generation/unit area ... they would also have a preference for poly panels over mono or hybrid simply because of the ROI ...

In case you still don't follow and maintain that efficiency has substantially improved, our 4kWp of panels were installed towards the beginning of the FiTs scheme and are 1652x994mm each .... the same manufacturer now makes/offers a 250W panel with the same dimensions - alternatively you could take something like a SolarWorld 250Wp mono panel as a direct comparison ... these are 1675x1001mm .... it's only when you spend extra and pay for higher efficiency that you can pack a higher generation density onto the same roof area, but you're likely to be paying around 70% more/Wp for the panels just to get a 30% increase in efficiency ...

I really do HTH
Z

1961Nick

zeupater wrote: »

.......... it's only when you spend extra and pay for higher efficiency that you can pack a higher generation density onto the same roof area, but you're likely to be paying around 70% more/Wp for the panels just to get a 30% increase in efficiency ...

I really do HTH
Z

.....which is possibly less than the cost of a standard panel 5 years ago?

Information is difficult to find & conflicting but the efficiency rates of mid-market panels seem to have improved from about 14% to 16% over the past 5 years, an increase of 15%. Some manufacturers claim 17% efficiency for a fairly small premium (not 70%), so that would be a 21% increase in efficiency over 5 years.