A cold-caller has just told me that I could make up to £1700 p.a. from 'solar panels'. I have not yet calculated the size of array which would be required to generate that sort of FiT income, but I am sure my roof is not big enough..... Interestingly, they hung up as soon as I told them I was aware of the dramatic reduction in FiTs.

As I say, I had not even done a rough calc, but even assuming 900kWh/kWp p.a. I make it under £1300. And the firm was not, according to what the caller said, based in the balmy South!

I had a guy trying to sell me a thermodynamic heat pump on the doorstep the other day, and freely admitted that he didn't know what it was or how it worked. At least I assume it was a thermodynamic pump, as he said it had a panel and derived heat "from the air". Least convincing sales patter ever.

That's actually the second time I've had somebody try to sell me a heat pump after seeing the PV array on my roof, and both have tried to tell me that I could run the heat pump off the PV. I assume they do so by simply tilting the northern hemisphere back towards the sun in winter?

To be fair, I do have a little one-room ASHP that I do occasionally run off the PV in spring and autumn (only sucks 700W max), but it annoys me that these dodgy salesmen might be tricking less clued up folks into installing expensive kit on false promises. I suspect that any company resorting to doorstepping would be unlikely to be sympathetic after you'd paid up.

Posted By: SeretTo be fair, I do have a little one-room ASHP that I do occasionally run off the PV in spring and autumn (only sucks 700W max)...

Spring and autumn last a long time in Britain. There are about 8 weeks of real winter (some of the time between mid Nov to end Feb/mid March) and, if we're lucky, 8 weeks of summer (sometime between mid May and mid September). The remaining 36 weeks are just, meh spring/autumn. I'm a firm believer that you should make a house reasonably comfortable for the extremes¹ but energy optimization should focus on those 36 meh weeks. Running an ASHP off PV makes a lot of sense in that context.

That ASHP, is it an Ecocent or the like or something else?

¹ In particular, using thermal mass to carry you through knowing that the extremes don't last long.

Posted By: Seret: ”Tell that to my array, winter seems to be lingering a bit this year.”

The week or more up to about Monday this week has been very bright here (NE Scotland). Not all as bright as this but nearly: http://edavies.me.uk/2013/02/girnigoe/ Greyer now.

“Fimer Windy 3HP. It's a little Italian through-the-wall reversible air con jobby.”

Interesting. Obviously seen the mini-split units but not something that small. Does it heat the room air directly or does it just heat/cool the incoming air? I.e., does the 2 kW or so of output require a corresponding high air change rate? Its infrared remote control should make it quite controllable with sufficient hackage.

Posted By: SeretThere is opportunity for hackage, but it works well enough without me starting to disassemble things I might have to send off the Italy to get parts for ;) It's pretty dependent on the IR, no controls on the unit itself.

I wasn't thinking of disassembling anything; just sending appropriate blips of IR from some other control system.

It's just a reversible heat pump, so it heats/cools the room air.

And, presumably, cools/heats external air. What I'm not clear about is does any external air enter/leave the house or are the two air masses kept quite separate?

Posted By: Ed DaviesAnd, presumably, cools/heats external air. What I'm not clear about is does any external air enter/leave the house or are the two air masses kept quite separate?

Seperate. Mixing them would defeat the point of the refrigerant. Having said that, there is a wee draught that comes out of one spot in the case, so I wouldn't say it's 100% room sealed. I might pull the case off in summer and see if there's something in there that's not sealing as well as it should.

I suppose I could bodge up some more intelligent control using an RPi and something like LIRC. I've never really played with IR, I assume it wouldn't be too hard to capture the signals from the remote. Would one just use a video camera, or are the timings too fine for that?

Posted By: SeretI've never really played with IR, I assume it wouldn't be too hard to capture the signals from the remote. Would one just use a video camera, or are the timings too fine for that?

No, not played with it myself either but read a few articles about using Arduinos and the like with it. I think normally people record the signals in the first place with an ordinary IR receiver rather than a camera. I believe LIRC has facilities to do that.

Posted By: skyewright

Posted By: SteamyTea

Posted By: Seretoverall I'm at 62% of PVGIS

That is a long way off.

At close of play on Feb 13th we were on track for 60% of PVGIS in February. A week later we were on track for 110%, and we finsihed the month on 157%. Funny thing weather...

I think these winter months are probably much more liable to large swings than the summer months.

Based on just over 2 & a half years observations with our WSW array up here at 57N, in Nov/Dec/Jan/Feb it's perfectly possible to get an individual day that is 4 or even 5 times "an average day", whereas in May/June/July around 2 times average is as high as could possibly be achieved. In Nov/Dec/Jan/Feb it's also possible to get zero production days...

Agree! In Feb. we generated 0.1 and 10.2 kWh on consecutive days and had a range of 0.1 to 13.4 kWh for the whole month (average = 5 kWh/day). Whatever happened to those cold, crisp, blue-sky winter days? Perhaps the same as those endless blue sky summers when I was a kid in the late 50's/early 60's!

SteamyTea - yes, I have the sunshine data for the Aberporth weather station which is our nearest at about 40 miles north east of where we are. The data goes back to 1942. Looking at the sunshine hours data for last year it seems that the main shortfalls were in April, June and July (see summary below). The other months look to be about average to be honest.

Last April we had 113 hours (58 hours below average). The average (since 1942) is 171 and the minimum was 113, hence the equal lowest since 1942.

Last June we had 144 hours (62 hours below average). The average (since 1942) is 206 and the minimum was 134, hence this month had just 10 hours more sunshine than the minimum recorded since1942.

Last July we had 139 hours (50 hours below average). The average (since 1942) is 189 and the minimum was 112, hence this month had 27 hours more sunshine than the minimum recorded since1942.

So for the year (which for us is April 2012 to March 2013) I expect to have generated approx 2819 kWh as against 2969 for April 2011 to March 2012; this would mean we would have to generate about 15 kWh every day for the rest of this month to equal last year’s total – at the current March average of 6 kWh per day, I don’t think this is going to happen!