Green Building Forum - Solar PV questions + ASHP or GSHP?

Solar PV questions + ASHP or GSHP?

philedge — Wed, 01 Mar 2023 16:39:40 +0000

Posted By: djhAIUI, you have to do the notification to the FIT licensee whatever you modify, Whether on the DC or AC side. Any time you make any change at all.

Only upstream of the generation meter on the AC side. Downstream is the rest of the house

Solar PV questions + ASHP or GSHP?

Jeff B — Wed, 01 Mar 2023 17:23:11 +0000

Philedge - by "original specification", yes, I did mean what is written on the MCS Certificate. This is referred to on the certificate as "Declared Net Capacity", which in my case is 3.88. I know that the panels have never generated more than 150W each (spec is 180W) so 21 panels would generate 3.15kW or about 80% of the maximum possible.

I was just toying with the idea that I could put some extra panels on, to get closer to the 3.88 but having seen the comments on the thread I think I will forget it, as I don't want any hassle with my F.I.T. provider!

If I win the lottery one day then I would put some extra panels on the SW facing roof and get a storage battery system to go with it.

Thanks to you others for your comments.

Solar PV questions + ASHP or GSHP?

djh — Wed, 01 Mar 2023 17:40:44 +0000

Posted By: philedge
Posted By: djhAIUI, you have to do the notification to the FIT licensee whatever you modify, Whether on the DC or AC side. Any time you make any change at all.

Only upstream of the generation meter on the AC side. Downstream is the rest of the house

Indeed yes. Perhaps I should have explicitly stated that when I said 'modify' I meant 'modify any part of the generation system'. Specifically, changing the meter is notifiable.

Solar PV questions + ASHP or GSHP?

WillInAberdeen — Thu, 02 Mar 2023 10:03:54 +0000

As another option, these people are offering shares in a co-op solar farm (they already built a couple of co-op wind turbines).
https://rippleenergy.com/

Seems like it will cost about Â£1k per 1kW of PV capacity you buy. Once built, you get electricity equivalent to your share of however much the farm generates, you can have it anytime of day/night at whatever kW rate you need. It's unaffected if you move house and you can sell on your share if you no longer need/want it, and it doesn't affect existing FITs. Any excess generation that you don't use, is paid as a credit.

But you still have to pay for transmission charges, metering, green levies, operating costs, so it ends up being about half price electricity.

That is a bit more expensive than buying into a commercial solar farm company, presently about Â£800 per kW afaict.

Others here have previously invested in this coop and can probably send a referral link.

(Disclaimer: this is not investment advice, if you wanted clever advice then ask someone clever, I've no connection to anyone, the sun can go up as well as down, etc etc etc)

Solar PV questions + ASHP or GSHP?

philedge — Thu, 02 Mar 2023 10:35:48 +0000

Posted By: Jeff BI know that the panels have never generated more than 150W each (spec is 180W) so 21 panels would generate 3.15kW or about 80% of the maximum possible.

I think that yours is quite an early FIT system and I dont know if there was any performance warranty for panel output but our panels installed in 2016 have a guaranteed 80% output at 25years. If yours have only ever managed 80% from new it might be worth looking into any warranty you got as 21 new panels will likely lift your generation!!

Solar PV questions + ASHP or GSHP?

Peter_in_Hungary — Thu, 02 Mar 2023 11:47:49 +0000

Posted By: philedgeIf yours have only ever managed 80% from new it might be worth looking into any warranty you got as 21 new panels will likely lift your generation!!

The output of PV panels are quoted as the max. for that panel - given ideal conditions. If panels at installed at less than in an ideal position (angle / direction) then you will never get the max quoted output.

I was told by the installer of my PV that to get close to your allowable limit then you should install a few more panels than the theoretical max output.

Solar PV questions + ASHP or GSHP?

djh — Thu, 02 Mar 2023 12:01:47 +0000

There's concern among some Ripple members about the possible partners that might be involved in their solar project. I haven't looked into it, so just to say caveat emptor.

Solar PV questions + ASHP or GSHP?

bhommels — Thu, 02 Mar 2023 12:07:28 +0000

Posted By: Peter_in_Hungary
The output of PV panels are quoted as the max. for that panel - given ideal conditions. If panels at installed at less than in an ideal position (angle / direction) then you will never get the max quoted output..

The kWp (kiloWatt peak) rating of a panel is verified in a so-called flash test: the panel is sitting at 25 deg C and its power output is measured when it is illuminated at a standardized spectrum and an intensity of 1000W/m2. The test does not last long to avoid heating up the solar cells as these derate with temperature.
Most manufacturers 'overrate' their panels so they deliver at least the stated output under these conditions.
It is very hard to achieve peak output in real conditions as the panels will almost always be warmer than in the test. You get the best chance at reaching peak output when the sun comes out from behind a rain cloud in otherwise cool and clear conditions. We might get some of that this month.

Solar PV questions + ASHP or GSHP?

Peter_in_Hungary — Thu, 02 Mar 2023 15:42:42 +0000

So is there an easy way to assess the performance of a typical string of PV panels as a quick (instant?) measurement?

I could see a long term test e.g. take the expected PVIGS output / month plotted against your obtained output and a consistent low result could / would indicate degraded performance, but how would you do a test at an inspection?

Solar PV questions + ASHP or GSHP?

revor — Thu, 02 Mar 2023 15:42:56 +0000

Posted By: Peter_in_HungaryI was told by the installer of my PV that to get close to your allowable limit then you should install a few more panels than the theoretical max output.

There is a lot more to it than the number of panels. It needs considering as a complete system. That means quality of cable, fittings workmanship e.g. crimping of terminals minimising voltage drops by cable CSA and length of runs. The spec for solar is a voltage drop of < 1%, typical 230v wiring can be 3 or even 5 %. The MC4 connectors are not all the same you need to keep to the same make. Staubli are considered the best and are pre-fitted to quality panels in the factory. If an installer fits a different make to them then the system is compromised from the quality of the connect and potential corrosion issue in the future due to galvanic corrosion as result of different metals in the connectors. I think there is more variability in the quality of installs that the output of the panels.

Solar PV questions + ASHP or GSHP?

philedge — Thu, 02 Mar 2023 20:25:42 +0000

Posted By: Peter_in_Hungary
The output of PV panels are quoted as the max. for that panel - given ideal conditions. If panels at installed at less than in an ideal position (angle / direction) then you will never get the max quoted output.

I'm sure you should be seeing more than a max of 80% output. Our original 4kw FIT system is split 3kw facing SE and 1kw facing SW and that produces 3.5kw max. When collecting and testing bits for our second system last year I had 3kw of panels producing 2.6kw in Feb.

Unless there's some quirk of Jeff's SE facing install, a max of 80% output of the panel rating seems low.

Solar PV questions + ASHP or GSHP?

revor — Fri, 03 Mar 2023 08:26:52 +0000

Posted By: philedgeI'm sure you should be seeing more than a max of 80% output. Our original 4kw FIT system is split 3kw facing SE and 1kw facing SW and that produces 3.5kw max. When collecting and testing bits for our second system last year I had 3kw of panels producing 2.6kw in Feb.

Earlier this week we peaked at 5.1 kw from our 6kw array at about 12:30 hrs and yesterday @ 15:30 when sun came out briefly 4.5Kw facing SSW. Could have been slightly more recording only samples every 5 mins.

Solar PV questions + ASHP or GSHP?

djh — Fri, 03 Mar 2023 10:27:30 +0000

One feature I see as an advantage of microinverters is that I can see the output of every panel individually. So if there was a partial fault of a panel or microinverter I should be able to see it fairly easily. Each panel is different because of different shading and because each row is at a different angle because of our curved roof. Here's a view of yesterday:

Solar PV questions + ASHP or GSHP?

cjard — Fri, 03 Mar 2023 18:28:04 +0000

"But with ground mount you get to install at the optimum angle and direction which is unlikely on a roof"

The solar calculator I used when investigating this didn't indicate it making a huge difference?

Solar PV questions + ASHP or GSHP?

djh — Fri, 03 Mar 2023 19:50:01 +0000

Posted By: cjard"But with ground mount you get to install at the optimum angle and direction which is unlikely on a roof"

The solar calculator I used when investigating this didn't indicate it making a huge difference?

It depends on how far off the optimum you are; the curves are pretty flat near the optimum and get steeper further away. Most people don't control what aspect their house faces, so that can be a long way off. Things might get better if the latest proposals to loosen restrictions come to pass regarding the distance above the roof that the panels can project.

Solar PV questions + ASHP or GSHP?

gustyturbine — Tue, 06 Jun 2023 12:32:07 +0100

So after having many (mostly NIMBY) objections my planning has been approved Now it gets serious!! So, obviously I am building the most efficient structure that I can afford so my question is this- Living on the coast in Ceredigion I am installing 10kw of PV ground mounted with battery storage. I'm also installing heat recovery this build. However, as I am installing PV would solar thermal be pointless? Secondly, as I'm on the coast would an ASHP or GSHP make more sense? I currently have a GSHP (boreholes and does my DHW) and running costs are fairly high with a family of 5 (3 females with long hair, me, no hair) Mains gas isn't an option and I'm in Renewables so I believe in the Green way of doing things. Would the GSHP (without the DHW load) be better in winter than the ASHP? I'm thinking it would due to ambient temp so I'm leaning towards the following - PV + battery, Heat recovery plus GSHP trusting the PV would take most of the annual DHW load through the new emersions etc available. Thanks all.

Solar PV questions + ASHP or GSHP?

djh — Tue, 06 Jun 2023 15:33:35 +0100

Posted By: gustyturbineas I am installing PV would solar thermal be pointless?

Yes, unless there are some exceptional circumstances (restricted space for mounting is the most common)

Secondly, as I'm on the coast would an ASHP or GSHP make more sense?

Depends on costs and the microclimate. It can be expensive to put a ground source in.

Posted By: gustyturbinetrusting the PV would take most of the annual DHW load

Except maybe in the depths of winter, when your HP is doing the most.

Solar PV questions + ASHP or GSHP?

gustyturbine — Thu, 08 Jun 2023 12:15:53 +0100

Thank you djh. That confirms my thinking. I've got a GSHP currently but I am thinking I'd go ASHP next time. It might cost more to run than a GSHP on some winter days but not many I don't think. Then, during warmer, sunnier months the ASHP shouldn't really be needed at all. I'm hoping that Heat recovery will improve things still further.

Solar PV questions + ASHP or GSHP?

cjard — Mon, 12 Jun 2023 18:16:33 +0100

"Then, during warmer, sunnier months the ASHP shouldn't really be needed at all"

I wish I'd built my setup so the house air could be ducted through the ashp and back into the house in hot weather, that way I'd get the double benefit of taking my excess house heat and stashing it in the hot water tank. As is, I'm looking for a second ASHP unit to put inside the house to get rid of the excess solar gain

Solar PV questions + ASHP or GSHP?

Peter_in_Hungary — Mon, 12 Jun 2023 20:26:15 +0100

Posted By: cjardAs is, I'm looking for a second ASHP unit to put inside the house to get rid of the excess solar gain

Can't you reduce solar gain with shading or use passive air change - low vents on north side high vents on south side to create air flow rather than buy an ASHP then spend energy running it.