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spunko2010

Anyone got solar panels...?

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I'm considering solar pv panels, having moved recently and the new house has an electric AGA and electric underfloor heating (£££ running costs). The AGA is supposed to run on Economy 7 / night storage. I've been researching solar panels for a while, and want to use them to be as offgrid as possible. Will continue to use heating oil (kerosene) for upstairs central heating and hot water, but want to run everything else through the PV panels (100% usage).

A few things I can't seem to understand despite reading loads:

1. Is it actually possible to have 100% solar power electricity in the SE of the UK in 2017? Nobody seems to want to answer this, so I'm assuming 'no'. What is the typical usage? My site is pretty ideal in terms of direction/location/angle etc.

2. I've been looking at getting 8KW/h sized freestanding units which is about 35 panels, but according to this page, the AGA alone is going to be using 224 KW/h a week... a WEEK. What is the normal yield? I don't mind about FIT etc, just want to save money on my electricity bills which I am assuming will be well over a grand a year.

Anyone here got PV panels?

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Just now, The Knimbies who say No said:

Suspect you'll be on a loser trying to run the AGA, especially as the times you appreciate it most are during winter.

The obvious question is why persist with the AGA if you want to save money?

I've never had one before, I hated it at first, but I've started to appreciate how well it cooks food, so want to give it a try. There's another hob, and a microwave/grill which I intend to use on those rare hot summer days.

I'm going to wait a few months anyway, before making any plans, but just wanted to see if there was a possibility of running it through solar. If there isn't, I'll very likely get rid.

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Kurt will along soon!

The Aga will certainly be less efficient than the underfloor heating (if that is combined with an air source heat pump), do you have that in your system? That and panels  might be a better purchase than the solar panels on their own. Inlaws have largish bungalow, underfloor heating and a few panels and bills very low.

 

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Just now, spunko2010 said:

I've never had one before, I hated it at first, but I've started to appreciate how well it cooks food, so want to give it a try. There's another hob, and a microwave/grill which I intend to use on those rare hot summer days.

I'm going to wait a few months anyway, before making any plans, but just wanted to see if there was a possibility of running it through solar. If there isn't, I'll very likely get rid.

They have a certain charm, doubtless, and I can see why people like them. Guess if you spec the PV system to run it in winter the problem then becomes how to manage the excess during summer. Cover off some panels, or create a thermal battery for winter, which in theory ought to help with eg your kerosene bills if used for water preheating, or as a source for a heat pump for heating. Would be a great challenge to have a go at, best of luck.

Will be wrestling with a related but smaller challenge in due course as I bought a thermal panel on EBay, plus an old hot water cylinder, and will be trying to construct a solar water preheater. Dunno if I've got a large enough cylinder, I suspect not, but it is a 'proof of concept' and I'll take it from there if some success is had. We'll see how that goes.

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41 minutes ago, spunko2010 said:

2. I've been looking at getting 8KW/h sized freestanding units which is about 35 panels, but according to this page, the AGA alone is going to be using 224 KW/h a week... a WEEK. What is the normal yield? I don't mind about FIT etc, just want to save money on my electricity bills which I am assuming will be well over a grand a year.

Anyone here got PV panels?

You seem, no offense, to be a little green on this subject.

PV panels would not be rated energy-wise, but rather, power-wise.

Power = Energy / Time

So power is measured in Watts or kilo-watts : ie kW

Energy is the consumption of power over time, so energy is typically measure in kilo-watt-hours : ie kWh

So a 1kW bar fire will consume 1kWh for every hour you run it.

Your solar array is probably delivering 8kW

Your AGA is consuming 224 kWh per week. Seeing as there are 168hrs in a week, that means your AGA is rated at 224/168 = 1.333 kW

So in theory your solar array should be just fine.

However, there will be peaks of consumption (power requirement). That 1.333 is likely made up of downtime (0kw) and uptime (??kW).

Central heating boilers (gas) run at the equivalent of maybe 25kW when running full pelt. I don't think the AGA will be that highly rated as it would fry household cabling (equiv of 100 amps!!!), but what I'm saying is it will be higher than that 1.333 figure.

You need to know the power rating on your AGA (and underfloor heating etc) before you can work out whether the array will do all your requirements. That should be marked on the equipment.

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39 minutes ago, spunko2010 said:

 

2. I've been looking at getting 8KW/h sized freestanding units which is about 35 panels, but according to this page, the AGA alone is going to be using 224 KW/h a week... a WEEK. What is the normal yield? I don't mind about FIT etc, just want to save money on my electricity bills which I am assuming will be well over a grand a year.

 

Your units are confused.  The solar panels will be 8kW.  So, if in summer there are 5 hours of usable sunlight over 7 days, that'll be 8x5x7 kWh, or 280kWh.  

The Aga will be 224kWh (not per-hour -- that's a crazy amount of power).  So, over summer they'll take an amount of energy about equal to the solar panels provide.

But.  Run the Aga (if you want it) max 9 months of the year -- don't bother June/July/Aug.  Just use the hob and work around the oven requirement.

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Should say that if you go down the road of a heat battery, it is not to be assumed that it's as simple as hooking 8kW panels up to an 8kW immersion element and that's it, as I understand it significant losses can be incurred if the element's power rating is not well matched to the panel's output at a particular moment.

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great minds dgul 'n' all, ...

 

Of the OP, remember as alluded above, power of array is measured under ideal conditions (sun at right angles, ideal temperature (not too hot)).

Obviously this is unrealistic in our country, especially at night!

You'll need storage, which is v expensive for large wattage. Being Economy 7 compliant, the AGA should be able to supply some heat outside sunlight hours, but you'd have to look into how it dumps that heat and when it's likely to be stone cold w/o battery backup. Reference to how it works under economy 7 will provide the answers. Underfloor heating should work similarly depending on the type of underfloor heating. If it's heating a big concrete block you may be better off than one might imagine.

I'm afraid it's a case of knuckling down and doing the research and 'math', unless you can find someone with a similar setup in a similar area. Doubtful.

 

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2 minutes ago, The Knimbies who say No said:

Should say that if you go down the road of a heat battery, it is not to be assumed that it's as simple as hooking 8kW panels up to an 8kW immersion element and that's it, as I understand it significant losses can be incurred if the element's power rating is not well matched to the panel's output at a particular moment.

I think we're all agreed that this is an enthusiasts project rather than something the average joe could hope to wing, just cos he wants cheap heating.

That said, it could be fun ...

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10 minutes ago, Sledgehead said:

I think we're all agreed that this is an enthusiasts project rather than something the average joe could hope to wing, just cos he wants cheap heating.

That said, it could be fun ...

Would be fun alright, hopefully with some success too. With PV output feeding into the mains though, I'd get professional input.

I decided to have a go with thermal rather than PV as, despite the installation advantages that PV enjoys wrt the lack of plumbing, the eleccy side of it seems far from straightforward. As I'm only interested in water preheating it seemed an unnecessary complication to add electricity into the mix, rather than just heat the fluid directly. However I may end up running a small 12V pump or pumps off a PV panel so I might not avoid it completely. Might just be easier to get a mains adapter though tbh.

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4 minutes ago, The Knimbies who say No said:

Would be fun alright, hopefully with some success too. With PV output feeding into the mains though, I'd get professional input.

I decided to have a go with thermal rather than PV as, despite the installation advantages that PV enjoys wrt the lack of plumbing, the eleccy side of it seems far from straightforward. As I'm only interested in water preheating it seemed an unnecessary complication to add electricity into the mix, rather than just heat the fluid directly. However I may end up running a small 12V pump or pumps off a PV panel so I might not avoid it completely. Might just be easier to get a mains adapter though tbh.

Would agree with that.

Not au fait with any of this. Re PV, can you tell me what the legal issues are in keeping the thing separate from the grid? Presumably you still need compliant circuitry anyhow, tie-in or no tie-in?

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No idea, but I'd work off the assumption that you would need the work completed to certain standards and/or ratified in some way, if only for the buildings/contents insurance side of things in the events of a problem. I may be wrong. Several kW is a serious amount of juice in a domestic setting.

This might be what pushes me to get a 12V mains adapter rather than a PV panel for pumping duties, as trivial as it seems by comparison.

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I have a 4kw system at a near optimum angle about as far south as you can go in mainland Britain.  I would estimate the electricity saving as about 20 - 25 quid a month averaged so 250 a year; suggesting that your system will save double that so half what you're thinking.

The off grid thing seems odd - how do you wire that all up?  Power dips massively when a dark cloud goes over so you'll find your computer dying on a regular basis if you haven't got the grid making up the shortfall.  Battery storage is not yet good enough to act as an overnight store; the expected usage of the (very pricey) batteries is about 30 times a year not 365 so I doubt they'll last long if you use them on a daily basis. 

Improvements to the battery storage should be there in a few years but the big problem with your proposed system is that if you are trying to get entirely offgrid you'll be fine in the summer but get a few grey overcast days in the winter and the generation will be pretty much non-existent.  The batteries won't get enough to recharge on the few light days so you will find yourself sat by a candle with a blanket wrapped round you from late November to early February.

 

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We’ve had an AGA for 30+ years and a 3.25 kWp PV array for three and a half.

Your 30-amp model uses some 224kW per week so on the basis of 7 hours consumption per day I guess the AGA is rated between 4.5kW and 5kW.

Our PV installation produced an average of 47 kW per week last year (obviously, far more in the Summer and less in the Winter) so a 16-20 kWp array should generate the electricity required by your AGA for much of the year.

If you were determined to be off-grid and willing to invest the substantial capital required for a battery bank, cabling, switchgear and grid-backup changeover switch (for multiple overcast days) I guess it could be made to work and with an even bigger array then no reason why the underfloor heating could not be included as well.

But wouldn’t it be a lot simpler to link into the gird as per standard PV installations then use immerSUN (or similar) switches to divert all generated power to the AGA and/or the heating?

Assuming you have enough room to install such a large array, everything will be much cheaper than going off-grid through using proven and straightforward technology, you have a built-in backup in case of PV problems (or bad weather) and although it was not your aim, there will be a FIT payment to sweeten the deal.

As for the AGA, as you have found, the cooking experience is very good and once you have lived with one for a few years it’s really hard to get rid of it.

In our case, the .5kW to 1kW radiant heat keeps the kitchen warm on even the coldest day, takes the chill off the hall and main bedroom above and means two of us can work from home without using any other heating until the evening.  

Recently installed double glazing, new doors and 600mm of attic insulation plus the PV’s mean we now spend 30% less on heating and lighting than we did 10 years ago but I still calculate the AGA costs us £8-£10 per week more than replacing it with a conventional stove and turning the heating up! 

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The difficulty with an off-grid system is how do you make most efficient use of the power. Battery storage is not really there yet, at least not at a sensible price. If you had an electric car which you could charge during the day, then that's one thing, but if not, you'll struggle to make much use of the panels.

If this is a business premises with high daytime electricity use, then you could move some onto panels, but it's a challenge to do this in a home environment.

There are significant hazards with PV systems, so you would be strongly advised to get any installation made to MCS standards, if only for your buildings insurance. Don't forget that batteries are also potentially hazardous - lithium batteries are highly flammable, and lead acid batteries are potentially explosive and full of corrosive acid. Do you really want this sort of thing in a home environment?

One thing to bear in mind is that your local fire service may have certain requirements, I'm aware of at least 1 house with solar panels, where the fire brigade just let it burn to the ground, because they didn't want to spray any water on the solar panels.

If you are going to get a proper system installed, you may as well get a grid-tie system. The standard inverters are all grid-code compliant, and just need to be commissioned by someone with MCS certification so as to be suitably grid friendly. Typically, for a domestic premises, the DNO will require an export limit of 4 kW. Some of the better inverters can be configured to limit exports, but allow the panels to generate more power, if you could use the power locally (i.e. you could have an 8 kW system, with a 4 kW export limit, and if you can use the energy as it is produced, you can benefit from it - again, however, this is difficult in a home environment, so inverters capable of doing this tend to be directed more at the light commercial market). Another option is to ask for a 400 volt mains connection upgrade, which will usually come with a 10 kW export limit - but this could be very pricey.

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thanks for all the replies. I'm considering freestanding because i have a largeish plot and the council are insistent on a lot of red tape if they're to be placed on the roof. i also think it'll spoil the roof if placed there as this is a feature of the house.

 

ill do some sums and see what i come up with. powering the aga and underfloor heating would take the bulk of the costs out, if i could power the hot water off of it that'd be a big plus as well. 

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Yes Spunky. I would like solar panels in the garden, not on the roof. Unfortunately I have run out of money and can't afford them.

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1 hour ago, spunko2010 said:

thanks for all the replies. I'm considering freestanding because i have a largeish plot and the council are insistent on a lot of red tape if they're to be placed on the roof. i also think it'll spoil the roof if placed there as this is a feature of the house.

 

ill do some sums and see what i come up with. powering the aga and underfloor heating would take the bulk of the costs out, if i could power the hot water off of it that'd be a big plus as well. 

How much do you expect to spend on kerosene btw?

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54 minutes ago, The Knimbies who say No said:

How much do you expect to spend on kerosene btw?

going by my back of fag packet calculations about 900 a year. 

Edit: That's 900l so about £500. But that's probably not accurate, I'm basing it on what I used to spend in my old house which was EPC 'B' rated and multiplying it by 1.5x. I used to have ridiculously low running costs. This place is much harder to work out, as I've only been living here for a few weeks, and it's been very cold (I noticed -7 C a few nights ago), the loft insulation is about 50mm thick currently, 2 windows are so warped there may as well not be there, etc etc.

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3 hours ago, ChumpusRex said:

The difficulty with an off-grid system is how do you make most efficient use of the power. Battery storage is not really there yet, at least not at a sensible price. If you had an electric car which you could charge during the day, then that's one thing, but if not, you'll struggle to make much use of the panels.

If this is a business premises with high daytime electricity use, then you could move some onto panels, but it's a challenge to do this in a home environment.

There are significant hazards with PV systems, so you would be strongly advised to get any installation made to MCS standards, if only for your buildings insurance. Don't forget that batteries are also potentially hazardous - lithium batteries are highly flammable, and lead acid batteries are potentially explosive and full of corrosive acid. Do you really want this sort of thing in a home environment?

One thing to bear in mind is that your local fire service may have certain requirements, I'm aware of at least 1 house with solar panels, where the fire brigade just let it burn to the ground, because they didn't want to spray any water on the solar panels.

If you are going to get a proper system installed, you may as well get a grid-tie system. The standard inverters are all grid-code compliant, and just need to be commissioned by someone with MCS certification so as to be suitably grid friendly. Typically, for a domestic premises, the DNO will require an export limit of 4 kW. Some of the better inverters can be configured to limit exports, but allow the panels to generate more power, if you could use the power locally (i.e. you could have an 8 kW system, with a 4 kW export limit, and if you can use the energy as it is produced, you can benefit from it - again, however, this is difficult in a home environment, so inverters capable of doing this tend to be directed more at the light commercial market). Another option is to ask for a 400 volt mains connection upgrade, which will usually come with a 10 kW export limit - but this could be very pricey.

thanks for sharing that CR

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10 hours ago, spunko2010 said:

going by my back of fag packet calculations about 900 a year. 

Edit: That's 900l so about £500. But that's probably not accurate, I'm basing it on what I used to spend in my old house which was EPC 'B' rated and multiplying it by 1.5x. I used to have ridiculously low running costs. This place is much harder to work out, as I've only been living here for a few weeks, and it's been very cold (I noticed -7 C a few nights ago), the loft insulation is about 50mm thick currently, 2 windows are so warped there may as well not be there, etc etc.

I suppose a way forward might be to take care of the insulation side of things to start with, which would perhaps allow a PV system of a reduced size and cost depending on the (possibly considerable) impact of the low tech, easily installable measures. Seems like your place has scope to work on some of that, although I understand the willingness to crack on given the current cold weather. If the loft insulation is an easy installation, access wise, I'd be tempted to do that if you can source it on a good deal. Pipe lagging likewise, if none is in situ or it looks damaged etc.

Can you easily get access under the floors, in any parts which are not covered by the underfloor heating?

Cheaper 'seconds' insulation boards can be had from a place called 'seconds and co' who have an EBay shop, if these are of use. With good access I filled the underfloor between joists in my place, and have the material do inbetween the attic rafters too. Although there is fairly effective mineral insulation laid on the loft floor, I'd like to make use of the rest of the space which is very cool and draughty by comparison.

http://stores.ebay.co.uk/secondsandco/

 

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5 hours ago, The Knimbies who say No said:

I suppose a way forward might be to take care of the insulation side of things to start with, which would perhaps allow a PV system of a reduced size and cost depending on the (possibly considerable) impact of the low tech, easily installable measures. Seems like your place has scope to work on some of that, although I understand the willingness to crack on given the current cold weather. If the loft insulation is an easy installation, access wise, I'd be tempted to do that if you can source it on a good deal. Pipe lagging likewise, if none is in situ or it looks damaged etc.

Can you easily get access under the floors, in any parts which are not covered by the underfloor heating?

Cheaper 'seconds' insulation boards can be had from a place called 'seconds and co' who have an EBay shop, if these are of use. With good access I filled the underfloor between joists in my place, and have the material do inbetween the attic rafters too. Although there is fairly effective mineral insulation laid on the loft floor, I'd like to make use of the rest of the space which is very cool and draughty by comparison.

http://stores.ebay.co.uk/secondsandco/

 

Cheers for that, will check it out.

I can't get the insulation done sadly until April now because my attic is/was a bat roost, and the Bat Convervation Trust / Nature England have basically said no until then. It's quite a long story, I could risk it but it wouldn't pay off in the long run so will just have to wait.

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