Renewables: "talking 'bout my generation"

KevinG

Fruit_and_Nut_Case wrote: »

I'm glad I investigated more thoroughly and took the plunge. I think the "south-facing" roof requirement is over-emphasized sometimes.

Agreed, if you look at the figures, anywhere between West and East via South is viable assuming there is no significant shading.

EricMears

Our roof is South facing for reasons of thermal gain rather than SP performance. When designing it, SP payback period was measured in centuries rather than years.

If SP had been a consideration I'd have tried for a slghtly steeper roof.

The_Green_Hornet

Here are the results from North Bucks:

May 2012 generation is 98% of PVGIS prediction and 84% of May 2011 generation.

2012 year-to-date generation is 103% of PVGIS prediction and 95% of 2011 YTD generation.

http://www.pvoutput.org/aggregate.jsp?id=7259&t=m

Martyn1981

Fruit_and_Nut_Case wrote: »

My roof is WSW (-68 degrees) so like yours is far from the "ideal" orientation. When I was first researching solar PV I was concerned about this and assumed that it wouldn't be worthwhile; even some installers were dubious.

I'm glad I investigated more thoroughly and took the plunge. I think the "south-facing" roof requirement is over-emphasized sometimes.

Absolutely F&N. At -70 I'm down about 10%, -90 would be down about 15%. But ..... actually have a big BUT....

I argued a long time back, perhaps Xmas, that as panel prices drop, a non south roof may be an advantage (or at least, less of a disadvantage). Fixed Install costs are pretty high, so fitting more panels helps to 'dilute' them within the total cost. So, fitting panels on both E&W roofs doubles the potential size, but for a lot, lot less than double the cost.

Crucially, because they are not producing high generation at the same time, this won't cause problems when dealing with the DNO, and will allow a single inverter with a 3.68kW cap to operate happily, and hopefully without ever actually capping. Eg 6kWp spread evenly over 2 roofs, with something like a SB5000TL capped to 3.68kW. Simples!

Recently priced up a system for my Aunt, but will depend on when she gets the house she's moving into. Package was 3.2kWp ESE + 2.1kWp WNW with a SB5000TL, installed for £8k. Estimated generation with PVGIS climate was 3,950kWh's pa. Equal to a very good 4kWp South system, but with a slightly longer and flatter generation curve. Lots of generation, right through the day.

Does anyone know where I can find a description for the oft touted '20% of UK properties are suitable for PV'. I'd like to know if there is a roof orientation factor included, possibly SE to SW?

Mart.

GaryMo_2

KevinG wrote: »

I'd agree with that. After all, if I were to adjust my PVGIS estimates by using the maximum inverter output rather than peak panel power, it would reduce them considerably and I would have exceeded PVGIS by an even larger amount than I already have!

Is your inverter rated higher than the peak power of your panels?
Surely the limiting part of your installation should be the governing factor (Declared Net Capacity)?
I'll never see more than 3.7ish kW from my system yet others that have inverters capable of 4kW outputs (G59) report seeing 4kW and above (not just peaking for minutes) on cool bright days.

Oscargrouch

A mere 7.00 today

EricMears

Oscargrouch wrote: »

A mere 7.00 today

An even merer 5.4 Kwh ( & from a system that is rated at nearly twice as much as Oscar's !).

But of course even that was twice what I needed to make up for lost interest.

Martyn1981

Met Office maps for May are ready, already! Usually takes a few days longer.

http://www.metoffice.gov.uk/climate/uk/anomacts/

Numbers look to stack up as usual once sunshine levels are taken into account. After a poor start, it looks like most of the country managed to make it back up to average or slightly better, but the S. East fell behind a bit in May.

Mart.

KevinG

GaryMo wrote: »

Is your inverter rated higher than the peak power of your panels?

No, lower, hence my point.

Oscargrouch

EricMears wrote: »

An even merer 5.4 Kwh ( & from a system that is rated at nearly twice as much as Oscar's !).

So, according to the quick calculation, without rubbing anything in, result v’s size; I more than doubled your result Eric! :rotfl:
Obviously a brighter day here.