For help, advice and discussion about stuff not related to aviation. Play nice: no religion, no politics and no axe grinding please.
#1848373
Morten wrote:When we looked at this it was much more for the feel good factor of independence


Morten, you may or may not know this, but solar panels are wired such that if the power supply from the grid fails, your panels also stop generating. This may sound silly, but I think this is to ensure your surplus generation that is back fed up the line doesn't give the line engineers a shock when they fix the grid problem. So, you don't really have independence.

In theory, you could shut off your supply from the grid totally with battery storage, but because of low generation in the winter months when consumption is high even battery backup isn't likely to be sufficient.
By Rjk983
FLYER Club Member  FLYER Club Member
#1848493
A couple of points on the air source heat pump.

A few people have commented on how noisy they are. Well it really depends on how well you site it. Ours is at the back of the detached garage, we never hear it in the house, you can hear it if you are at the back of the house, but it isn’t constant, even when running at high demand. And it is much quieter than the neighbours lawn mower or the cars and motorbikes on the road.

As for getting the heat out of the system, it very much depends on the design of your home and how well insulated it is. Ours was designed to Passivehaus standards, so has higher than normal insulation and is well sealed. The ground floor has underfloor heating and most of the rooms are tiled. Upstairs we have normal domestic heating radiators. They do run at a lower temperature than an older system, but you just have to alter your mindset for heating the home. When we had a house with gas central heating we had it set to come on for a few hours morning and evening and to blast out heat. With ASHP we turn it on at the end of September and it runs until the end of April. After a couple of days to get each zone up to temperature, the system just runs to top up heat as required, the only bit of the system that is constantly running is the water pump that is circulating the water in the system. It works well for us because we work from home (since before it was fashionable :lol: ) but even if the house is empty for a lot of the day it doesn’t make sense to turn off the system as most of the energy is used getting the space generally up to temperature, it then uses a little and often to keep it going.

One point to note is that if you are going to be using ASHP to heat your hot water tank for the water that runs out of the taps then you should have an immersion heater in the tank and have it set to run at a regular interval (I think it is weekly but I know there are heating bods on the forum who will know the rules better) this is used to bring the water in the tank up above 60 degrees C for a short period to kill off any legionella that may be developing.
#1848499
Colonel Panic wrote:That was certainly true until we installed a Tesla Powerwall, but I am now 99% sure that now we can continue to use solar during a power cut.


I found this an interesting read, CP. In brief, some battery systems do have the capability you suggest, including the latest versions of the Powerwall 2.0 with a back up gateway, although not earlier versions.

You may be interested to note the comments regarding restricting load during powercuts.

https://www.solarguide.co.uk/solar-back ... wer-cuts#/
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#1848510
George wrote:The thought of having a substantial dent taken off what I’m paying for power is enough.

I'm sure you don't mean that literally? :wink:

George wrote:The company have been very honest about projections too but will know for certain when I get the quote in the next few days!

I'd be interested in knowing what they say, if you are inclined to share? :thumright:

Having a quick browse over the last 15 mins or so I still predominately see estimates north of 10yrs for payback.

I haven't had time to read the Which article, however I get the impression all is not yet as it appears.

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Another thought that struck me is whether the feel good factor is increasingly becoming self deception? :D For example with Scotland running at 97% renewable electricity that's surely where the feel good factor is now? :D I think I'll leave the money in the bank and focus on the feel good factor of not having the environmental impact of manufacture and installation. :wink: Joking aside that is now worthy of consideration.

Also had a quick search and found the last time I considered it was 2015, when there was an interesting thread. Not that the numbers will be comparable today.
#1848518
Miscellaneous wrote:Another thought that struck me is whether the feel good factor is increasingly becoming self deception? :D For example with Scotland running at 97% renewable electricity that's surely where the feel good factor is now? :D I think I'll leave the money in the bank and focus on the feel good factor of not having the environmental impact of manufacture and installation. :wink: Joking aside that is now worthy of consideration.

Also had a quick search and found the last time I considered it was 2015, when there was an interesting thread. Not that the numbers will be comparable today.


Misc,

Do you think Scotland would have reached 97% of renewable energy without the manufacture and installation you now decry? It didn't happen in a vacuum.

And, as a further point on this, most of that comes from wind generation which almost certainly has higher environmental impact from installation, manufacture, and especially ongoing maintenance costs than solar.

Reading that old thread was indeed interesting. The two main advocates of pv back then, CP, and myself, seem to have no regrets. I certainly don't.
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By Pete L
FLYER Club Member  FLYER Club Member
#1848519
What about the noise impact on others of an air-source heat-pump? The traditional gas boiler is (a) indoors (b) fairly quiet and (c) any pump noise under the direct control of the persons affected.
By Rjk983
FLYER Club Member  FLYER Club Member
#1848524
Pete L wrote:What about the noise impact on others of an air-source heat-pump? The traditional gas boiler is (a) indoors (b) fairly quiet and (c) any pump noise under the direct control of the persons affected.


As I said above Pete, it is important to properly site the pump, but my experience is that it is quieter and less intrusive than the traffic on the road going past our house, and certainly quieter and shorter duration than the neighbours cutting their grass.

If noise really is a problem (and may well be in some of the overcrowded modern housing developments) then the outdoor unit can be put in a housing. It needs to be big enough to allow air to circulate and heat to dissipate, it also needs to have a lot of open space in the walls to allow sufficient airflow, but careful design of louvres can do this while also acting as a baffle to the noise.
Last edited by Rjk983 on Sat May 22, 2021 12:06 pm, edited 1 time in total.
#1848525
A chap I met at the county agricultural show a couple of years ago said that he wouldn’t sell me a solar array as it was not going to pay back in my lifetime. Now that the FIT is gone and the pathetic price the electricity board pays for outgoing power I don’t think it is worth it - certainly not if doubling the cost by installing a Tesla Powerwall system. He does install them in the town though - he says they are more gullible.
#1848526
@Paultheparaglider where am I decrying the technology?

I think you misunderstand my point? I am not against renewable energy. Neither am I suggesting you or CP should not have bought them. My point back in 2015 was that they were being misrepresented and people were buying in to the hype on purely financial grounds. They were, IMO, being mis sold. That is my sole beef.

People were cashing in rainy day savings to buy panels, savings they then did not have when the rains came. Mr A I know cashed in an ISA to buy them, I guess in his mid 60s, Mr T I know bought them in his mid 70s(?). Both did so on financial grounds I'm not so sure they made wise decisions. :wink:

I still can't get it to work on financial grounds. I think @Colonel Panic's earlier post supports my position that they fall short of delivering and have maintenance costs. That fact, as I see it, is independent of the reasons he or you purchased your panels. Of course it's more complex than simple numbers, there are many considerations. The main factor being affordability.

Of course, as discussed it is not all about the financials and providing one can afford it and is fully aware of what they are doing it's fine to spend one's money based on emotion. Even when that emotion may be a little misplaced. I mean not many aeroplane owners buy them based on sound financial decision making. That's a good example of valuing other factors over pure cost and one I find easier to justify than the value in the car sitting at the door.

I'd support anyone buying solar panels as long as they are aware of what they are doing and the true financial implications. :thumleft:

As for not being able to fly at any 'reasonable' altitude without being in sight of a wind farm…. :evil: The point is they are there and me buying solar panels ain't going to change it one bit. :wink:[/quote]
Last edited by Miscellaneous on Sat May 22, 2021 11:54 am, edited 2 times in total.
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By George
FLYER Club Member  FLYER Club Member
#1848538
OK here's what I have been quoted for the panels only:

Equipment Description and Cost.
Equipment proposed is 15 x Longi 360 W all black mono panels (5.4 kWp) on Solis dual 3600 inverter with monitoring, Emlite generation meter, all roof fixings including Genius slate roof mats, PV and Part P cabling and electricals; all fully installed and commissioned for £5,880 inc vat.

And here's what they have estimated:

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#1848572
@George - run your numbers through the Energy Saving Trust's calculator; I have just done it for you (assuming your welsh postcode hasn't changed, and with a 6kW system they reckon you will get 5.09mWh / year, so perhaps 4.5mWh / year. https://www.pvfitcalculator.energysavingtrust.org.uk

The chances of you using 95% of production are slim to say the least, and even 75% is highly unlikely, but possible. You know our house, and Mrs Me and I were only able to use 50% of our production (plus an additional 25% going in to the HW tank via a smart switch (google Solar iBoost). But with a 5.4kW system our self usage would have been even less.

The Solar iBoost has paid for itself in spades, so DEFFO worth considering. Feel free to call me if you want to chat.
#1848654
@George , the days of pv being a good financial investment went out with the FIT payment. I was an early adopter so get the highest FIT rate, and mine took 8 years to payback.

I think your generation numbers look reasonable. I'm not very far from you, and my 4kw system averages about 3,800 kwh per year. So, the projections for a 5.4 kw setup seem OK. My shading, roof angle, and orientation aren't that different to your numbers.

As @Colonel Panic points out, the real sensitivity here is the usage. Without a battery system and the solar switch set up that CP suggests which add costs, you will be unlikely to get anywhere near those numbers. 50% would be high. Further, you need to factor in the inverter costs. Mine is still going strong, but average life is supposed to be about 10 years, and a good one isn't cheap.

Using 50%, a saving of just under £500 pa means 12 year payback not 10 - have they ignored the vat? However, see my points above on additional costs. And that doesn't include any cost of money - the return you might get investing the money elsewhere.

This doesn't really stack up as a financial investment, but if it is any consolation, your total installation cost is well under half what I paid in 2011. I personally like the green aspects, and being a nerdy numbers guy love keeping records which gives me hours and hours of spreadsheet fun. My illness extends that far that I could tell you my generation on any day since
I had my system commissioned. :wink:

If you are planning to stay in your home for a good while and can spare the cash, then I'd say go for it. But just don't make that decision based on financial returns.
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#1848680
If I was going to start anew with a new build I would attempt to tailor my energy requirements according to the seasons. You don’t need a heat pump thrashing away just to heat water in the summer. Solar energy, whether it be from PVs or flat plate / vacuum tube heaters may be good for heating water, but where does the energy get dissipated when the hot water tank is up to temperature - you wouldn’t want that boiling away and the grid connect export payment isn’t worth the expense of the system. I don’t see much research into Fresnel lenses as a means of heating water. I am surprised that the day of the central heating radiator has not passed. Heating air (indirectly) and ducting that via a heat recovery system is a much more efficient and rapid system.
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By George
FLYER Club Member  FLYER Club Member
#1848684
Thanks for all the comments so far. To be clear I am looking to be green first, and get a sort of return (or add value to the house) secondly.

However, I will have to add getting an immersion heater tank as the boiler is a combi type. If I decide to keep the boiler as back up and forego the expense of a heat pump…
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