solar panel confusion

counting_down_the_days...

EricMears wrote: »

It's probably not a 'conventional' DHW tank fed by a cold water storage tank in loft as generally fitted pre-1970s.

Combi boilers were a step forward from that in that they saved storage space and give more or less instant hot water. However, if you want mains pressure hot water at a reasonable flow rate you really have to go back to storing heat in a well insulated tank. Storing it as pressurised hot water is one option but I've gone for storing in a vented tank at elevated tempertures then using that store to feed DHW via a heat exchanger. That of course allows you to mop up huge amounts of free electricity by aiming for a tank temperature of >90 deg C

OK

I don't know if I'm just too tired, but that confused me :cool: I'll have another read tomorrow! Thanks

EricMears

counting_down_the_days... wrote: »

I don't know if I'm just too tired, but that confused me

Sorry - but it's really not a simple subject and the rest of the team would probably fall asleep if I went into much greater detail.

counting_down_the_days...

Still don't understand, sorry! We have a pressurised tank, so the solarimmersion will do us fine, any excess free electric from the solar pv will be used to heat the water tank. In summer, I should be able to turn my boiler off completely

silverwhistle

dreaming wrote: »

:j:j:j:T:T:T

Yay - installation completed today.

Thanks for coming back to let us know how it went. I'm doing my own research at the moment (and have visited a less than helpful thread!), but as someone in a similar situation (semi-retired, some savings) it's been useful.

I'm slightly worried about the proposed import tariff on chinese panels, and whether degression will impact me (and how) if I can't install by July (?) but your reasoning about the suppliers seemed sound, and it seems like you're happy with your decision.:-)

I'm used to Italian leccy installations which normally are a maximum of a nominal 3kw (actual 3.3kw), so perhaps 4kw would be too much for me as I'm well used to keeping my maximum demand below 3kw! A UK electric kettle is too much here, although a cheapo Wilko version at 1.8kw is ideal. My water heating for shower and bath is electric (!), but fortunately the local product is designed for local conditions, even if it takes ages to heat a (small) tank..

Martyn1981

silverwhistle wrote: »

I'm slightly worried about the proposed import tariff on chinese panels, and whether degression will impact me (and how) if I can't install by July (?) but your reasoning about the suppliers seemed sound, and it seems like you're happy with your decision.:-)

Hiya silverwhistle, the import tariff is already biting hard, and it hasn't even been set yet. Just the threat of imposing it, and backdating to early Mch means that the importers can't import - what do they charge, if they may at a later date have to pay extra duties. Clever move by the EU, but the solar industry isn't happy. No idea when this'll get sorted.

Degression - FIT rate won't drop on 1/5/13 (next review date), but will drop on 1/7/13 by at least 3.5%. The 1/8/13 review has been brought forward a month to bring several review dates into line.

The FIT rate drops based on a degression rate, which in turn is based on the installs in each 3 month period. The tipping point is 100MWp of installs in the qtr one before the review date. So for 1/7/13 it'll be based on the installs 1/2/13 to 30/4/13.

They are running close to that 100MWp point, but it doesn't really matter, since the rules also say that we can't have 3 consecutive qtr's without a drop, so a mandatory 3.5% reduction will kick in, in July anyway, so 15.44p down to 14.9p (ish!?!?).

Small enough to ignore I think? So that takes you to the end of Sept if you need time to thunk.

Please note, that whilst these calcs seem simple/predictable, that doesn't mean I've got them right. I've tried to track down a webpage I found a while back with all the info, but can't find it - maybe someone else can?

In the meantime, from memory, I think the degression table was:
less than 100MWp - no degression (but mandatory 3.5% if no drop in 3 qtrs)
100MWp to 200MWp - 3.5%
200MWP to 250MWp - 7%
250MWp to 300MWp - 14%
over 300MWp - 28%

Apologies if memory is wrong.

Mart.

dreaming

silverwhistle wrote: »

... your reasoning about the suppliers seemed sound, and it seems like you're happy with your decision.:-)

I'm used to Italian leccy installations which normally are a maximum of a nominal 3kw (actual 3.3kw), so perhaps 4kw would be too much for me as I'm well used to keeping my maximum demand below 3kw! A UK electric kettle is too much here, although a cheapo Wilko version at 1.8kw is ideal. My water heating for shower and bath is electric (!), but fortunately the local product is designed for local conditions, even if it takes ages to heat a (small) tank..

Thanks Silverwhistle. One of my questions was over the size - whether you could have "too much" generation as I am a light user (I think) and it was kindly explained that any "excess" would just be exported back anyway so decided to go for the maximum.
I'm very happy with my installer - they have been very communicative and helpful (mind you I haven't paid yet), and very happy with the installation. I have done 2 loads of washing (1 lot of towels so dried as well), 1 lot of dishwashing plus the usual stuff this weekend and my import meter went backward most of the time. Only when I put the toaster on for lunch when the drier was going did it go forwards (hmm - shall have to plan that better in future) but it is quite interesting seeing how different things affect it. From yesterday morning to this morning my import went down from 27561 to 27555, and my generation meter up from 3520 to 4834. I know this all means something-all I know is I'm saving money.

Dave_Fowler

dreaming wrote: »

Thanks Silverwhistle. One of my questions was over the size - whether you could have "too much" generation as I am a light user (I think) and it was kindly explained that any "excess" would just be exported back anyway so decided to go for the maximum.
I'm very happy with my installer - they have been very communicative and helpful (mind you I haven't paid yet), and very happy with the installation. I have done 2 loads of washing (1 lot of towels so dried as well), 1 lot of dishwashing plus the usual stuff this weekend and my import meter went backward most of the time. Only when I put the toaster on for lunch when the drier was going did it go forwards (hmm - shall have to plan that better in future) but it is quite interesting seeing how different things affect it. From yesterday morning to this morning my import went down from 27561 to 27555, and my generation meter up from 3520 to 4834. I know this all means something-all I know is I'm saving money.

I expect you'll find there is a decimal point between the 48 and the 34. In other words the generation meter went up from 35.20 to 48.34 ie a generation of 13.14kWh. That's worth just under £2.50.

Dave F

zeupater

silverwhistle wrote: »

.... so perhaps 4kw would be too much for me as I'm well used to keeping my maximum demand below 3kw! ....

Hi silverwhistle

The issue with the above is that a 4kWp system will very rarely achieve 4kW generation ... in sunny conditions around 3.0kW to 3.6kW would be more likely, depending on how clear the sky actually is along with panel operating temperatures.

It's mostly cloudy (but bright) here today and we're mainly generating at somewhere around 1.1kW from a 4kWp system, dropping to ~800W and occasionally rising to around 3.3kW for a few minutes .... the important thing to consider is that today is a bright day ....


(935W now).
HTH
Z

dreaming

Dave_Fowler wrote: »

I expect you'll find there is a decimal point between the 48 and the 34. In other words the generation meter went up from 35.20 to 48.34 ie a generation of 13.14kWh. That's worth just under £2.50.

Dave F

Thanks - I did say earlier my eyesight is a bit dodgy.

That's pretty good generation then isn't it? Have been at work all day today so my import meter has gone waaay back. Have notified Scotttish Power and their auto-response is to reply in 5 days.

silverwhistle

Thanks for all those posts. I'm pretty keen on getting PV so as long as the housing association hand my house back on time and with a roof, and if the potential providers work quickly I might even get in before the July degression.

I'm a light user too (no TV, efficient lights etc.) and I'll have to get new white goods when I move back anyway, so will get efficient ones. Following Dreaming's comments I might get a washer/dryer as I'd forgotten that it can sometimes difficult to get things _properly_ dry in the UK! I used to work for a REC many, many years ago, and I remember in one of my first jobs explaining to monthly billing (maximum demand) customers that the possible reasons they'd had a higher bill were their poor power factors and/or switching on a bank of machinery etc. before another spike had finished, so I reckon I could be quite good at adjusting demand to output limits.:-)

Fortunately 'Ampshire on the coast isn't too bad according to PVGIS so I could get reasonable results.