For help, advice and discussion about stuff not related to aviation. Play nice: no religion, no politics and no axe grinding please.
By simon32
#1848685
Energy saving is not as easy as it seems. I wonder about the maintenance costs of PV panels and their associated circuitry.
I have been using thermal solar panels for 40 years and at my latitude (44°N) we have free hot water for 8-9 months of the year. The initial installation cost was high, but was probably amortised within 10 years. Maintenance is not negligible. I had to pay a roofïng contractor a significant sum to change the panels for newer more efficient ones (they are too heavy for me to get on and off the roof) and now the problem is too much hot water in the summer. The water temperature often rises above the thermal cutoff for the water heater and when the winter comes round I wonder why the resistance heater is not working. Just have to take the cover off and poke the reset button with a screwdriver.
The other problem is frost. The primary circuit has antifreeze in it, but over the years due to leakage this becomes diluted. It is not a trivial task to top up with antifreeze as it means climbing on to the roof and having a helper drain out a bit while filling from a a funnel.
For the moment I get round the over heating and over cooling by running the circulating pump continuously in very hot and very cold weather. The resistance heater is controlled automatically by a microcontroller board with a real time clock. It has worked 24/7 for 25 years and the RTC still keeps good time, long may it last. The only problem is that altering the program or the date requires hook up to a laptop with a serial port. My last one gave up the ghost this year.
Simon
Paultheparaglider liked this
#1848689
@simon32 , that is interesting to read. It strikes me most of your issues are specific to heated panels rather than pv. I have heard of pigeons getting under pv panels and damaging wiring, but otherwise the panels themselves seem to be pretty reliable. And, of course, the pv panels are much lighter to lift up if they need replacing. My biggest concern panel wise is that if one failed it might prove hard to get a matching replacement. I'm touching wood as I type, but I've had no issues with my panels so far, and my only maintenance is that I like to get up on a ladder and give them a good wash most years.

That said, my inverter might need replacing soon as it is coming up to the ten year mark.
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By Morten
FLYER Club Member  FLYER Club Member
#1848699
Lots of interesting info here, thanks all.
Just as another input, though, conventional systems are also not maintenance or trouble free, so a full comparison should take the broad picture into account.

It seemed (and still seems) to me that the power production is quite accurately predictable, but the value of that production much less so, with eg FIT changing and dependent on own usage. As mentioned, one of the interesting effects is that you become much more aware of how /when /what power you use, which in itself is a good thing...
I do think that to get the best out of a PVA or wind system, you do need some local storage such as batteries. It's the same problem which the national grid has - non - availability of power when you need it and a surplus when you don't... That of course adds to the initial cost and any payback period. However, the power storage technology is advancing rapidly (much more so than the PVA tech) so that may change in a few years.
For new builds, adapting the whole heating (and other consumers) system from the beginning makes all this much easier. Doing the same with an 18th century cottage is a much more challenging task...
Colonel Panic liked this
#1848704
Morten wrote:As mentioned, one of the interesting effects is that you become much more aware of how /when /what power you use, which in itself is a good thing..

Very much so; we have reduced our expenditure on electricity more by being aware of usage than we have by generating.
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By Rjk983
FLYER Club Member  FLYER Club Member
#1848988
Morten wrote:
…I do think that to get the best out of a PVA or wind system, you do need some local storage such as batteries. It's the same problem which the national grid has - non - availability of power when you need it and a surplus when you don't... That of course adds to the initial cost and any payback period. However, the power storage technology is advancing rapidly (much more so than the PVA tech) so that may change in a few years...


If you have an electric vehicle then there are chargers available that will let you charge the car as a battery store and draw from it when generation dips. The car needs to be compatible and there needs to be a means of controlling and setting protocols.
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By Morten
FLYER Club Member  FLYER Club Member
#1849048
Indeed. It's quite interesting to be able to mix the technologies like that and that particular combo is quite neat. However, if you want to use your car in the morning after it has been slowly discharging overnight to keep the heating pump running and to boil your morning tea... the peaks and troughs of consumption/production are not quite synced ;)
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By riverrock
FLYER Club Member  FLYER Club Member
#1849068
Lol - indeed - but you can set it to have a minimum charge, for your morning drive.
My car isn't compatible, but some people have been looking at buying electricity from the grid at the very cheap overnight rates when the wind is blowing, and selling it back during the evening peak. There will be money to be made there somewhere.
By Rjk983
FLYER Club Member  FLYER Club Member
#1849091
@Morten :D very true

@riverrock when I last looked at PV for our house a year or so ago there were tarrifs available on the market that encouraged you to do that, I think it may have been octopus but I could be wrong.
By avtur3
FLYER Club Member  FLYER Club Member
#1849134
Slightly off the main topic but still sort of relevant, I think. There is a report in today's Telegraph that government will influence banks to discourage mortgage lending on homes that don't have at least an ECP rating of C or better by 2030.

AIUI it is essential to improve insulation in order to make heat pumps viable in a home, I would imagine that achieving a C rating is going to be quite a challenge in many properties.

Is there an accepted correlation between EPC rating and the likelihood that heat pumps will be an adequate source for heating?
By riverrock
FLYER Club Member  FLYER Club Member
#1849137
Rjk983 wrote:
@riverrock when I last looked at PV for our house a year or so ago there were tarrifs available on the market that encouraged you to do that, I think it may have been octopus but I could be wrong.

Every time I've looked, they were always "soon", "trials" or just about to happen.

Eg - article from 2 months ago https://www.drivingelectric.com/your-qu ... -back-grid

Different if you are storing enough to deal with the grid directly.
By Rjk983
FLYER Club Member  FLYER Club Member
#1849216
I didn’t look too deeply into it, but this is the one I saw when I looked recently.

In no way is this an endorsement or recommendation for them, I’m not with Octopus but they seem to get an alright reputation compared to other suppliers.

https://octopus.energy/blog/outgoing/

Meet the UK’s first ever smart export tariff: Outgoing Octopus.

As Feed-In Tariffs (FiTs) come to an end, we're the first UK energy supplier to launch a true export tariff that settles export real time with the grid.

Put simply, it means that if you have solar power, we’ll buy the energy you generate, sell it to the grid, and give you the money we make on your behalf. So that instead of you paying us for energy, we pay you for it. No tricks. No catch.

Better – our export tariff is smart. The price you get paid for what you generate changes half-hourly in line with the wholesale price of energy. That means at times of the day when energy is most in demand (generally around dinner time) you’ll get paid more to export, helping to reduce strain on the grid by supporting it with clean energy at times when there’s generally a lot of fossil fuels in the mix..


What can I use an export tariff for?
×
We haven’t put a limit on this. Export via any source capable of feeding energy back to the grid. So that’s not just solar PV…

YOU CAN: get a micro-wind turbine installed, charge up home batteries when energy’s cheapest to feed back into the grid later, or (if you’ve managed to get your hands on a vehicle-to-grid charger) use your electric car’s spare battery
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By PeteSpencer
FLYER Club Member  FLYER Club Member
#1849269
ISTR a few years ago at the Saucats fly-in, I was talking to someone (a mate of Simon M who flew in in the Lt Snoring C172) who was intimately involved in energy supply both from the grid and solar panels/wind farms.

He told me that electrical energy does not actually physically flow from yer private sources back into the grid and that the 'repayment' calculations made to punters are based on theoretical formulae.
Can someone actually confirm that your surplus energy produced at home really does flow back into the grid or is it as Simon's mate suggested?

Or have things changed since Saucats...............

I've read a couple of articles about 'Net metering' but they lacked clarity of detail...........

I find it hard to understand how 'my' (theoretically speaking-I don't have solar power) spare 'kilowatt hour' can make any inroads into the thousands of kilowatts sloshing along the pylons at the bottom of my garden and..... past my front door under the streets.

I'd really like to know.

Peter
#1849278
If one is generating more power than consuming on site, then that excess power does go back to the grid - modern meters tend not to "go backwards", but they would if they could.

Most residential installations of PV only have one meter, which measures generation. AIUI the power companies decided that it wasn't worth measuring the exact export figure so no export meters are installed on typical residential installations (less than 10kWh). Instead, they "deem" that 50% of what is shown on the generation meter is "probably" exported, and if you have a FIT that pays a subsidy, this 50% deemed export is what is paid out.

The game is therefore to utilise as much generated power on site as a) it is "free", and b) it doesn't reduce the amount of subsidy paid.

Before I installed a battery, I used ~50% of what I generated, shoved about half of the remainder in to my HW tank, and exported the final 25% - whilst being paid for the 50% deemed export.
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