Buying a house with pre-installed Solar-PV feed in?

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 wintertree 07 Sep 2014
A question for the UKC collective, as some quick googling has not provided a definitive answer. I probably don't know the terms to search for.

If you wish to buy a house where the seller has previously installed Solar-PV on the roof with a feed in tariff, are you as the purchaser under any obligations to continue with the feed in?

I'm asking because quite a few potential purchases come with a roof covered in solar panels these days and I assume it is all feed in. I do not want to be the recipient of a regressive stealth tax.

My preference would be to remove them from the grid and connect them to a battery/inverter system for some redundancy, with a sensor controlled automatic transfer switch running lighting and key sockets from the redundant system when the batteries are above some charge level.

Lusk 07 Sep 2014
In reply to wintertree:

Ask the PV guys on the Electricians Forum.
They're a sound, knowledgeable lot and should give you a definitive answer.
KevinD 07 Sep 2014
In reply to wintertree:

You definitely need to be careful and find out whether the seller actually owns the solar panels or is leasing out the roof.
The latter apparently being lots of fun with the mortgage companies.
OP wintertree 07 Sep 2014
In reply to dissonance:

> ... seller actually owns the solar panels or is leasing out the roof.

interesting, I hadn't considered that possibility at all. Thanks.
OP wintertree 07 Sep 2014
In reply to Lusk:

Great, thanks for the pointer.
Lusk 07 Sep 2014
In reply to wintertree:

Give them as much info as possible up front, makes life a lot easier!
 Richard Wilson 07 Sep 2014
In reply to wintertree:

You should be under no obligation to continue with the FITS as long as its not one of the free installs.

Now to put a nail in your coffin. The running costs of an off grid battery based system is in the region of 8p per kWh used just for the battery replacement costs. Add in the inverter changes & the cost of getting the system set up in the first place & you would be mad to even consider it.

We have been living off grid now for about 6 years. Had there been a grid connection I would have used it. To give you an idea of costs, our inverter costs over £3k compared to about £500 for a grid connected one. We also need a solar charge controller which cost over £600. The battery system would have cost aprox £5k if it was new (its an ex forklift bank). This is for a daily usage of less than 4kWh per day which is well below normal usage.

If you dont want the FIT's then just cancel it but keep the system connected to the grid. Then get an EMMA type unit that will maximise the onsite usage of the solar elec so that you export as little as possible. The excess will go into heating your domestic hot water.
OP wintertree 07 Sep 2014
In reply to Richard Wilson:

> You should be under no obligation to continue with the FITS as long as its not one of the free installs.

Thanks. It seems the free installs are something I didn't know about, a good question to ask the estate agents up front. Thanks also for the numbers. I'm only after ~1KWh of capacity from the solar - enough to run lights, a fridge freezer and the pump on a stove boiler if/when the grid starts crapping out.

 John2 07 Sep 2014
In reply to wintertree:

Why would you not wish to continue with the FIT, assuming it is paid to the current owner? It's tax-free income.
OP wintertree 07 Sep 2014
In reply to John2:

> Why would you not wish to continue with the FIT, assuming it is paid to the current owner? It's tax-free income.

Because I find it an offensive, stealth, regressive tax. If I receive it, that money comes out of the charges on everyone's electricity bills, many of whom are struggling with their bills. Between that and my view that FITs are market manipulation that fail to address the coming electricity crisis, I want nothing to do with them.
 Richard Wilson 07 Sep 2014
In reply to wintertree:
Whilst your energy consumption might be 1kWh (very unlikely as the freezer will need about 0.5kWh if its a new one & lots more if its not. However the inverter will need to be on 24/7 & use about 1kWh for its own consumption) the fact that you want to run a freezer means that you need a substantial inverter to get the motor to start (when our main inverter was in for repair we killed 2 500 watt inverters trying to run a freezer that has a 80 watt motor). Substantial inverters need big battery banks. It prob has about a 100watt motor but it will need about 1200watt inverter to be able to start it.

I would guess that the install is about 4kWp. So it can make upto 30kWh per day in summer. Just using 1 or 2 kWh of that would be madness.

You will be much better off staying fully grid tied & using the power as its made. Doing it that way will cost you nothing & save you about 13p for every unit used from the solar.

If you cant be in then an EMMA type unit will do it for you putting heat into your hot water tank. Or just export the energy for the greater good.

Edit to add.

Forgot to cover the grid crapping out bit. You would be better off using a small cheap genny to cover grid outages. No on going costs if there are no outages unlike a battery system that will still need new bats even if not used much.
Post edited at 18:59
Lusk 07 Sep 2014
In reply to wintertree:

> Because I find it an offensive, stealth, regressive tax. If I receive it, that money comes out of the charges on everyone's electricity bills, many of whom are struggling with their bills. Between that and my view that FITs are market manipulation that fail to address the coming electricity crisis, I want nothing to do with them.

Doffs cap!
OP wintertree 07 Sep 2014
In reply to Richard Wilson:

Interesting. Thanks for the reality check on numbers. The standby power draw of the inverters does seem to be a killer - I hand't considered the need for a beefy inverter because of start-up draw vs steady state. I suppose you could have a relay switch the big inverter on with a low duty cycle matched to the fridge's typical pattern, but that's getting yet more complicated.

Re: start-up current and batteries, how about building a 24V, 3000 Farad capacitor using the same cells as these? http://www.bimblesolar.com/supercap12v - that should avoid the battery size problem and would also allow you to vaporise large pieces of metal if you get bored...

Thanks for the comments
WT
 JJL 07 Sep 2014
We have an Apollo GEM (a type of EMMA). They're about £400 but, with a bit of trial and eror with our boiler controls, has meant that we've used almost all the 4kWp we generate.

We looked into how to ensure we would continue to be ok if the grid was out - we have LOTS of pumps etc - but it was just crazy what was required to buffer a rare event.

To OP: as long as the FIT is direct to current owner and not to a third party you are ok.
 John2 07 Sep 2014
In reply to wintertree:

'My preference would be to remove them from the grid and connect them to a battery/inverter system for some redundancy, with a sensor controlled automatic transfer switch running lighting and key sockets from the redundant system when the batteries are above some charge level'

That may well be so, but the reality of solar electricity is that the vast majority of it is generated in the daytime in summer, whereas the majority of your electricity consumption will be in winter when the sun is not shining. There are battery storage systems available, but they are extremely expensive and I doubt that they would store the summer-generated electricity for long enough to enable it to be used in winter.
OP wintertree 07 Sep 2014
In reply to John2:

> That may well be so, but the reality of solar electricity is that the vast majority of it is generated in the daytime in summer, whereas the majority of your electricity consumption will be in winter when the sun is not shining. There are battery storage systems available, but they are extremely expensive and I doubt that they would store the summer-generated electricity for long enough to enable it to be used in winter.

Indeed. I'm only interested in something that can supply about 1kWH per day, and batteries rated for that aren't so expensive, and I'd be surprised if you can't pull that much out of Solar-PV on a sunny day in winter. If the system is primarily sitting there as a back up, the numbers seem workable. I'm happy to accept that using the Solar-PV power when its sunny and using a separate backup generator when needed is cheaper though.
Lusk 07 Sep 2014
In reply to wintertree:

Instead of batteries, use the power to heat your water.
Tanks required, obviously!
 Richard Wilson 07 Sep 2014
In reply to wintertree:

Ok, next nail.

The efficiency of using a battery will work like this.

DC Power from array converted to AC via inverter (85-90%)
Ac from inverter converted to DC at voltage suitable for charging bats (85-90%)
Battery charge efficiency (50-85% dep on depth of discharge)
DC from battery to AC via inverter (85-95%)

So thats roughly a round trip total efficiency of 50% ish.


Next nail, If your using FLA's (flooded lead acid) bats then you want to be looking at using no more than 50% of total capacity. You also want to be able to use the system for a few days in a row with no solar input. So again roughly you want a battery that is around 5 or 6 times the daily usage. If you use a 12v system thats about 450ah of deep cycle bats you need. Again roughly thats £500 worth for a reasonable brand.

On average in Dec Jan & Feb you will be lucky to get a weeks worth of power all month. In March through to Nov you will be wasting 20 to 30 times what you will put into your battery bank.

I understand your position but the kit is there already, its been paid for financially by the previous owners, to now stop it paying for its embodied energy would be madness. You want the system to produce the most energy that it can.

There are some new to market small systems that will allow it to keep working in a power cut. However they do cost to buy & install & in reality how often do you get a power cut & how long is it off for?


Re the super caps. You do realise that you would need at least SIXTY (thats £11,700 worth) of them to provide the 1kWh that you want?
OP wintertree 07 Sep 2014
In reply to Richard Wilson:

Fair point with all your nails bar one, it does sound like a small generator would make far more financial sense for backup power.

The one nail:
> Re the super caps. You do realise that you would need at least SIXTY (thats £11,700 worth) of them to provide the 1kWh that you want?

I meant use the minimum number of cells (6 or 12) to buffer the startup current of a fridge motor so you can rate the batteries for steady state and not start up. So that's one or two of the linked units,

> how often do you get a power cut & how long is it off for?

Very rarely these days, but if we don't start getting more wide spread power cuts this winter, it will be one soon, with grim times a few years down the road. Perhaps,
 Philip 07 Sep 2014
In reply to Richard Wilson:

SMA do a grid connected invereter with a built in 2kWhr battery. I can't find a price for it, and I think it's not G83/2 certified yet. But as it's built on the normal sunny boy 3600TL it should available soon.

I disagree about fit being a nasty tax on electricity users. I think the current level (14p + half of 4.7p) is just enough to make it worth doing. Cheaper battery systems would make it better.
 John2 07 Sep 2014
In reply to Philip:

The FIT is, as he says, a tax on electricity users. Solar panels will never generate electricity at time of maximum demand, in the cold of winter, therefore alternative methods of electricity generation will still be needed. However, his one-man campaign against the FIT will make no difference to anything (other than his personal income).
 Richard Wilson 07 Sep 2014
In reply to wintertree:

For the cost of 2 (£400) of the limited use caps you could have full use bats.

Roughly your freezer is going to start up 20 time per day. Each start say takes 2 seconds. Still adds up to a lot of extra start up caps needed.

Also if you have as a 1500 watt inverter at some point you will want to use more of its capacity. That will need a real battery system & not some poncy caps that cost mega bucks. I guess for the specialised system they have re the sound system is money well spent but in a typical domestic system its costly tech you dont need. You will also need to wire it with thick cables for its full capacity or you will end up with a fire.


I agree with the grim times will be coming thoughts.
 Richard Wilson 07 Sep 2014
In reply to Philip:

A 2kWh bat is a waist of time for anything more than a short grid outage.

SMA also do a Sunny Island system that you can add to an ongrid system. The units bare rated at 4-8kW & cost about £3k plus bats.

Victron do units that will also provide the same function.

Until we have more power cuts its just not cost effective. One big issue is the current battery tech is just not cheap enough long term.
OP wintertree 07 Sep 2014
In reply to John2:

> However, his one-man campaign against the FIT will make no difference to anything (other than his personal income).

Refusal to participate is not a campaign against. My one-man refusal would make a difference to more than the household income, it would avoid me being in the repugnant position of being a hypocrite. Maybe I shouldn't care, but that is important to my happiness.

More generally it seems daft to have a roof taken up with the things, and have them be no use in a power outage. I was interested to read on this thread that certified, grid tie inverter/battery systems are coming to the UK soon.
 Richard Wilson 07 Sep 2014
In reply to John2:
> Solar panels will never generate electricity at time of maximum demand, in the cold of winter, therefore alternative methods of electricity generation will still be needed.

The biggest issue is that energy is still too cheap & that we waste it 24/7.

We need to reduce our consumption drastically. The cheapest unit is the one we dont use.


Then we can use a range of power sources to meet the reduced needs.
Bring back the rolling power cuts of the 80's lol. That might shake a few people up & get them to use less. That or reverse the way power is charged for. Give every household an allowance of say 1000kWh per year that they get cheaply. Then for every 1000kWh they use over that the charge doubles.

Use more pay loads more. Could also be tied in to time of usage like economy 7 now but tied to the times that solar produces power.
Post edited at 22:04
OP wintertree 07 Sep 2014
In reply to Richard Wilson:

> Roughly your freezer is going to start up 20 time per day. Each start say takes 2 seconds. Still adds up to a lot of extra start up caps needed.

12V and 3,000 farad is 1kw for 36 seconds. So they could more or less cover all the freezer starts even without topping of from a battery. Chuck in a battery good for the steady state wattage. As you say though, you could just get beefier batteries for a similar price.

> Also if you have as a 1500 watt inverter at some point you will want to use more of its capacity.

True. If only 24V fridges and heating pumps were affordable and commonplace, the trap of startup current rated inverters would be gone, along with some losses. Thick cables though.

> You will also need to wire it with thick cables for its full capacity or you will end up with a fire.

Amen. I'd almost certainly not use the bimblesolar pre- build modules as I don't like having the terminals near each other with no barrier in between. Their resistance is low enough to sustain 36KA for a second into a disrespectfully placed hammer. Bad bad bad.

> I agree with the grim times will be coming thoughts.

That's why I want to get something sorted. No point in having ranted about their arrival for 5 years if I can't have a backup...
Post edited at 22:12
 jkarran 07 Sep 2014
In reply to wintertree:

> I'm asking because quite a few potential purchases come with a roof covered in solar panels these days and I assume it is all feed in. I do not want to be the recipient of a regressive stealth tax.

Tax? I like the idea of negative tax. They pay you for the size of it, you use the electricity it makes or don't you still get paid, your call.

> My preference would be to remove them from the grid and connect them to a battery/inverter system for some redundancy, with a sensor controlled automatic transfer switch running lighting and key sockets from the redundant system when the batteries are above some charge level.

Nothing to stop you doing that assuming you buy them outright rather than them having been installed and paying to a third party. Either way it's a stupid plan, grid connection makes most sense by a country mile. You'd never make back the cost of the storage in the saved energy that would have been exported and you'll be living with it degrading, depreciating, eating space and costing you maintenance time.

Buy the house you like.

jk
 Richard Wilson 07 Sep 2014
In reply to wintertree:


> I was interested to read on this thread that certified, grid tie inverter/battery systems are coming to the UK soon.


Yes but they are driven by the system you dont want to support. People want them to maximise the amount of energy they can use on site whilst still being paid for it. Makes a mockery of the FIT system as it should be about Feeding in the energy to the grid yet the system encourages onsite use & you still get paid for the export that never happened.

A better system would have been to pay nothing for total production & paid more than the import cost for any exported. That would encourage people to allow energy to be exported to the grid. Units like the EMMA would not have been created to cheat the system.

One thing that must be done with these systems that will keep the panels working in a power cut is to completely disconnect you from the grid or you could be responsible for killing a line worker.


I bet that power outages are less than 0.1% of the grid up time. Solar only works for 33% of the grid up time so I dont think that a 1/3rd of 0.1% is worth worrying about.
 jkarran 07 Sep 2014
In reply to wintertree:

> Indeed. I'm only interested in something that can supply about 1kWH per day, and batteries rated for that aren't so expensive, and I'd be surprised if you can't pull that much out of Solar-PV on a sunny day in winter. If the system is primarily sitting there as a back up, the numbers seem workable. I'm happy to accept that using the Solar-PV power when its sunny and using a separate backup generator when needed is cheaper though.

If that's all you want from it why the hell wouldn't you export the rest? Give the FIT to charity if it really makes you feel that grubby. Seems to me you're tying yourself up in knots over something trivial. Buy the house that suits you. If you don't need off grid power then don't waste your time and money on batteries, spend it on insulation, you'll get a much bigger ROI.

jk

OP wintertree 07 Sep 2014
In reply to jkarran:

Thanks for the comments. I'm coming up with a resounding No for getting a usable backup power source from solar and storage.

> Buy the house you like.

That's the plan. I'm starting to think if it is one with a roof of solar PV, that I remove the panels and kit and sell them and use the money to buy a little generator, the currently hypothetical surveyors report is probably going to say that the roof trusses aren't spec'd for all the weight etc.

Our bills are low enough that free solar power doesn't make a dent in the finances, and personally I don't want to receive a feed in. I've also got no idea what the long term complications of having a roof covered in heavy glass and metal units are, other than not being able to visually inspect the roof as it ages.

> If that's all you want from it why the hell wouldn't you export the rest?

I've got no problems exporting it without the FIT, I had just assumed that it was either/or with the backup. If the DC side can be switched to charge batteries, and then export, or a grid tie inverter can manage the batteries, it can export away.

> Give the FIT to charity if it really makes you feel that grubby. Seems to me you're tying yourself up in knots over something trivial. Buy the house that suits you. If you don't need off grid power then don't waste your time and money on batteries, spend it on insulation, you'll get a much bigger ROI.

It's hard to get an ROI on heating or power if you're as stingy as me, so I've never been looking for a return, just a viable backup source. I'm not tied in knots on it, but I do immensely dislike the idea of various people I know, who really struggle with their bills, funding my (currently hypothetical) subsidy. Grubby is a good word for it.
Post edited at 22:40
OP wintertree 07 Sep 2014
In reply to Richard Wilson:

> A better system would have been to pay nothing for total production & paid more than the import cost for any exported. That would encourage people to allow energy to be exported to the grid. Units like the EMMA would not have been created to cheat the system.

I like your perspective here and earlier on pricing. As for people cheating a rigged market? I'm shocked.

> One thing that must be done with these systems that will keep the panels working in a power cut is to completely disconnect you from the grid or you could be responsible for killing a line worker.

Indeed. I had in mind having critical systems on a separate ring that uses a certified automatic transfer switch to go from grid to backup. I don't know if that's enough or if there are fault conditions in the ATS or household wiring that could energise grid connected circuits. Any affordable backup system is not going to be big enough for all domestic loads.

> I bet that power outages are less than 0.1% of the grid up time. Solar only works for 33% of the grid up time so I dont think that a 1/3rd of 0.1% is worth worrying about.

I hope you are right.
Donnie 07 Sep 2014
In reply to wintertree:

No. You're not obliged but even if you were just send the money back to the treasury or give it to charity... plus the more green energy on the grid the less fossil fuels burned...
 Philip 08 Sep 2014
The aim of the subsidy should have been to make local generation a possibility, cash neutral regardless of scale, and not a profitable business.

To that end they should not have paid for export. Payment for generation should allow the recovery of the panel cost + installation. The saving for the user is not buying. Then they should have subsidised battery technology to encourage storage.

The way to do this would have been to split the tariff and get rid of export. So for up to 4kW I would have paid 16.5p/unit (14p + half of the export 4.77p). Then once you exceed 4kW if you have an export limiter you get the same rate, if you don't you drop to 13p and no export payment.

Those numbers don't work out right, but they need tweaking so that a 2-10kWhr battery is a more sensible option than anything else.




 timjones 08 Sep 2014
In reply to wintertree:
> That's the plan. I'm starting to think if it is one with a roof of solar PV, that I remove the panels and kit and sell them and use the money to buy a little generator, the currently hypothetical surveyors report is probably going to say that the roof trusses aren't spec'd for all the weight etc.


If you believe that we are heading for an energy crisis then isn't it a slightly bizarre ethic to remove a renewable resource and replace it with one that relies on finite supplies of fossil fuels?

 timjones 08 Sep 2014
In reply to wintertree:
> That's the plan. I'm starting to think if it is one with a roof of solar PV, that I remove the panels and kit and sell them and use the money to buy a little generator, the currently hypothetical surveyors report is probably going to say that the roof trusses aren't spec'd for all the weight etc.


If you believe that we are heading for an energy crisis then isn't it a slightly bizarre ethic to remove a renewable resource and replace it with one that relies on finite supplies of fossil fuels?

OP wintertree 08 Sep 2014
In reply to timjones:

> If you believe that we are heading for an energy crisis then isn't it a slightly bizarre ethic to remove a renewable resource and replace it with one that relies on finite supplies of fossil fuels?

If I remove and sell it, someone else will still be feeding it in to the grid. Moving on from that, it's the ethic of "If we get another winter down to -18oC I want to be able to keep my family and I warm."

As far as I can tell, the short term energy crisis (that may be) that concerns me has nothing what so ever to do with the finiteness of fossil fuel supplies and a lot to do with the failure of governments for the last 20 years to keep the total generation base in the UK at a sufficient level, with the emphasis on renewables making a nice smokescreen that makes people think enough is being done.

Longer term, there is enough coal in the UK to last a long long time, and it can be mined largely without people with modern steam fracturing techniques, but I would rather see some new fission plants built instead. As the later isn't happening it probably won't be to long before the coal gets mined, at the rate we're going.
In reply to wintertree:

The surveyor's perspective:

A friend who is a surveyor tells me that many of these houses are unsaleable, because there is a legal issue with the contract on installer or govt. paid panels, and also the installation on many roofs is rubbish and they are not watertight, requiring extensive repairs. Someone quoted 4 hours to install an array of panels on my roof - I can see that would be a cowboy job and would require restorative roof work down the line. Also the panel efficiency diminishes rapidly apparently.
DC.
 jkarran 08 Sep 2014
In reply to wintertree:

> If I remove and sell it, someone else will still be feeding it in to the grid. Moving on from that, it's the ethic of "If we get another winter down to -18oC I want to be able to keep my family and I warm."

No they won't or if they do you'll get buttons. You find someone that will do the paperwork required to access FIT on second hand panels of unknown provenance, I bet you can't. And without FIT there's next to no point in fitting solar PV, I know I've looked into it.

Warm? I'd get a log burner and more insulation before I got a generator.

jk

OP wintertree 08 Sep 2014
In reply to jkarran:

> No they won't or if they do you'll get buttons. You find someone that will do the paperwork required to access FIT on second hand panels of unknown provenance, I bet you can't. And without FIT there's next to no point in fitting solar PV, I know I've looked into it.

Okay, bang goes that idea. I seem to be thanking people on this thread for a lot of reality checks.

> Warm? I'd get a log burner and more insulation before I got a generator.

That's the first item to go in. A nice stove with external air intake and a hot plate on top. Still, beyond that it would be nice to be able to run the lights, a pump for a back boiler, a fridge and a laptop. Ideally someone would sell a little stove mounting stirling generator....
OP wintertree 08 Sep 2014
In reply to Dave Cumberland:

> The surveyor's perspective:

Thanks for that. I've been a bit skeptical of the average quality of installations, given the number I've seen pointing in the wrong direction or largely sheltered by trees etc. That and the bit where double glazing companies fit them...

 Philip 08 Sep 2014
In reply to wintertree:

You won't get much selling it second hand. To claim payment you need the MCS certificate of the installer. So you'll be paying a professional installer to install a 2nd hand bit of kit. Not likely.

Better you don't waste the money removing it, and think about how to insulate and heat the house effectively. If for (in my opinion misguided) ethical reasons you don't want payment for generating or feeding in, you could still use the panels to heat your hot-water via immersion, saving you some cost.

 timjones 08 Sep 2014
In reply to wintertree:

> If I remove and sell it, someone else will still be feeding it in to the grid. Moving on from that, it's the ethic of "If we get another winter down to -18oC I want to be able to keep my family and I warm."

That is probably one of the things that has changed. How about putting on extra jumpers or using blankets etc?

> As far as I can tell, the short term energy crisis (that may be) that concerns me has nothing what so ever to do with the finiteness of fossil fuel supplies and a lot to do with the failure of governments for the last 20 years to keep the total generation base in the UK at a sufficient level, with the emphasis on renewables making a nice smokescreen that makes people think enough is being done.

> Longer term, there is enough coal in the UK to last a long long time, and it can be mined largely without people with modern steam fracturing techniques, but I would rather see some new fission plants built instead. As the later isn't happening it probably won't be to long before the coal gets mined, at the rate we're going.

Maybe the answer is not for a growing population to demand more power but to learn to get more efficient in how we use what we already have?
OP wintertree 08 Sep 2014
In reply to Philip:

> you could still use the panels to heat your hot-water via immersion, saving you some cost.

I'd like to get some solar thermal panels installed, and one of the properties I'm interested in has the entire roof covered in PV. The solar thermal wold need a lot less space, be a lot more efficient, work better in cloudy weather and wouldn't degrade significantly over the next 15 years. Perhaps remove enough for some solar thermal and leave the rest feeding in without a FIT, as long as it's not degrading the roof.
OP wintertree 08 Sep 2014
In reply to timjones:

> That is probably one of the things that has changed. How about putting on extra jumpers or using blankets etc?

Have you ever lived in a house without any heating for several days when the night time temperature is dropping below -15oC? I have. It wasn't fun. Jumpers barely helped. Sleeping in jumpers in a down sleeping bag didn't help much. If there is no source of heat in a property, insulation can't keep it in. It was bad for the house, and it was bad for me. Back in the good old days, people had independent heating that wasn't tied to the grid. This is something I can't shoe-horn into my current house, but will in my next.

> Maybe the answer is not for a growing population to demand more power but to learn to get more efficient in how we use what we already have?

You're preaching to the converted. I use a lot less energy than many people I know. In the mean time, I would like a robust backup. Small wind turbines are out if you want a small property, solar-PV is not shaping up well. So generator it is. If I put a heat exchanger on the exhaust and perhaps run the cooling loop through an immersion tank, it's might even be more efficient than grid connected fossil plants as well.
Post edited at 10:51
 timjones 08 Sep 2014
In reply to wintertree:

> Have you ever lived in a house without any heating for several days when the night time temperature is dropping below -15oC? I have. It wasn't fun. Jumpers barely helped. Sleeping in jumpers in a down sleeping bag didn't help much. If there is no source of heat in a property, insulation can't keep it in. It was bad for the house, and it was bad for me. Back in the good old days, people had independent heating that wasn't tied to the grid. This is something I can't shoe-horn into my current house, but will in my next.

The idea wasn't to live without heating, it's to think smarter. It's a small house that can't find enough space for a standalone gas heater to heat a room in any emergency. Certainly if you've got space for a gennie you've got space for a heater. It seems crazy to be entirely reliant on electricity to run all your heating.

> You're preaching to the converted. I use a lot less energy than many people I know. In the mean time, I would like a robust backup. Small wind turbines are out if you want a small property, solar-PV is not shaping up well. So generator it is. If I put a heat exchanger on the exhaust and perhaps run the cooling loop through an immersion tank, it's might even be more efficient than grid connected fossil plants as well.

The logical answer would surely be a backup that doesn't rely on electricity. Burning fuel to turn into electricity which is then going to be turned back into heat isn't likely to win any awards for efficiency.
OP wintertree 08 Sep 2014
In reply to timjones:

> The idea wasn't to live without heating, it's to think smarter. It's a small house that can't find enough space for a standalone gas heater to heat a room in any emergency. Certainly if you've got space for a gennie you've got space for a heater.

Mid-terraced living in a tiny house has no secure yard space for a generator or gas store, no space for a coal store or log store, and no "outside" behind the fire place to put an air intake for a stove; so any stove you do fit will either be drawing buckets of cold air into the house, or suffocating you/going out. Things left in the little bit of yard space have a habit of walking off and never coming back.

> It seems crazy to be entirely reliant on electricity to run all your heating.

As I said, a wood burning stove is the main plan. It would be nice to plumb it in parallel with what-ever the main boiler is, and that would need a small electric pump. So "all your heating" we mean "a small electric pump".

> The logical answer would surely be a backup that doesn't rely on electricity. Burning fuel to turn into electricity which is then going to be turned back into heat isn't likely to win any awards for efficiency.

Indeed. A stove gets basic heat and cooking. Anything more complicated than a wood burner does tend to need a bit of electricity, even solar thermal. It's never turned in to heat, it just enables everything to run. Likewise as I said I'd like to be able to keep a freezer going, lights and a few other do-dads. I remember 12 days without power after the storm of 1987, and that was in a house with an open fire, a stove and a bottled gas hob. If the same was to happen now I'd have a mis-er-able time. Yes, the stove gets past the biggest problem, but if there is an affordable (in the context of buying a house) solution that keeps a pump running and a few other essentials, what's the problem?
Post edited at 11:15
 jkarran 08 Sep 2014
In reply to wintertree:
> I'd like to get some solar thermal panels installed, and one of the properties I'm interested in has the entire roof covered in PV. The solar thermal wold need a lot less space, be a lot more efficient, work better in cloudy weather and wouldn't degrade significantly over the next 15 years. Perhaps remove enough for some solar thermal and leave the rest feeding in without a FIT, as long as it's not degrading the roof.

Or fit the solar thermal panels to the walls or a garden fence, that way you can fit good sized panels working well in autumn to spring with the low sun but self limiting (shaded) during the summer months so you don't have to go for expensive self limiting tubes or worry about them boiling up your tank?

jk
Post edited at 11:40
 Greenbanks 08 Sep 2014
In reply to wintertree:

Have you seen this? Not read the thread but have had a fair run-around trying to unravel a relative's dealings with a cowboy installer

http://www.ukhillwalking.com/forums/t.php?t=565745
 timjones 08 Sep 2014
In reply to wintertree:

> As I said, a wood burning stove is the main plan. It would be nice to plumb it in parallel with what-ever the main boiler is, and that would need a small electric pump. So "all your heating" we mean "a small electric pump".

It's the reliance on an electric pump that frustrates me. Surely there has to be scope for some sort of thermo siphonic system with a bit of smart engineering and pipe routing. Or maybe the smart answer would be to use to use a small engine to run a pump directly rather than accepting the inefficiencies of a larger engine turning rotary motion into electricity and then back into rotary motion. Maybe it just needs the daughter on a suitably designed "excercise bike"
OP wintertree 08 Sep 2014
In reply to Greenbanks:

> Have you seen this? Not read the thread but have had a fair run-around trying to unravel a relative's dealings with a cowboy installer

I hadn't, thank you for the link, good reading.
OP wintertree 08 Sep 2014
In reply to wintertree:

Dear UKC collective, thank you for the many thoughts and comments.

The property with the entire south facing half of roof covered is done through a "rent-a-roof" firm. Bad news if you want to access your roof in the next 20 years for any reason, and doubly bad news if they are poorly installed. Triply bad news if you wanted roof top solar thermal (Although JKarran's comment about wall mounting seems sensible).


OP wintertree 08 Sep 2014
In reply to timjones:

> It's the reliance on an electric pump that frustrates me. Surely there has to be scope for some sort of thermo siphonic system with a bit of smart engineering and pipe routing. Or maybe the smart answer would be to use to use a small engine to run a pump directly rather than accepting the inefficiencies of a larger engine turning rotary motion into electricity and then back into rotary motion. Maybe it just needs the daughter on a suitably designed "excercise bike"

No reason to be a snob against electricity, just because. Electric transmissions in mechanical systems are the way of the future - look at the Freedom class cruise ships or type 45 destroyer. More efficient than mechanical systems in many cases. I suppose I could plumb a back boiler in with convection or a pump, controlled by valves, but it seems more than 1-2 rads benefits from a pump.
Post edited at 13:53
 Richard Wilson 08 Sep 2014
In reply to Dave Cumberland:

> Also the panel efficiency diminishes rapidly apparently.

> DC.

Sorry but thats complete rubbish.

All panels on the MCS approved list have to have a 25 year 80% or better performance guarantee.

Most of the loss is in the first few years say down to 90% then they slowly reduce over the next 20 odd years.

Its also woth knowing that the low light flexi type panels loose even more in the first few years but they are under rated to compensate this. Not many FIT install will use that type of panel.


Re using the second hand equipment. Its a no no as the FIT rules stipulate all kit must be new. As part of the paperwork all the serial numbers of the panels are registered to the install. If those numbers come up again they will know they are used panels.

 andrewmc 09 Sep 2014
In reply to wintertree:

As a person paying an electricity bill, I am happy to pay a bit more to buy your (potential) solar power... and if you feel that bad just give it to a charity, possibly even a charity helping people with energy bills!
 steveriley 09 Sep 2014
Sounds a bit like you're putting the ethical cart before the practical horse. For any shortcomings of the FIT scheme the upshot is every kWh your panels produce is one less kWh demanded from the grid from alternative means (and quite probably fossil fuel). Buy the house you most like, leave the panels on, use the power where you sensibly can, pocket the offset in what you *would* have been paying to import from the grid.

Then do something that makes you feel good with the FIT payments - local CAB, something specifically to do with fuel poverty, whatever. Interesting thread though, practical storage options have always been the missing link. Battery technology has changed so much in recent years, who knows what's next?
OP wintertree 09 Sep 2014
In reply to SteveRi:

> Sounds a bit like you're putting the ethical cart before the practical horse.

Indeed - although on the practical side it seems quite a few people have reservations about the installation quality and long term effects of some rooftop PV installations.

> For any shortcomings of the FIT scheme the upshot is every kWh your panels produce is one less kWh demanded from the grid from alternative means (and quite probably fossil fuel).

Yes. It's not much of an upshot though as the kWh from solar onto the grid from domestic PV is not a significant fraction of demand when the sun is out in summer, let alone on average. It's never going to be either, this is not California.

> Buy the house you most like, leave the panels on, use the power where you sensibly can, pocket the offset in what you *would* have been paying to import from the grid.

It looks like one of the houses we're interested in has pre-installed panels from a "rent-a-roof" company. This basically puts the house off our list, as we'd not have proper access to the roof for maintenance (or skylights!) for 20 year, and would have trouble selling as it sounds like its very hard for buyers to get a mortgage under a "rent a roof" scheme.

> Interesting thread though, practical storage options have always been the missing link. Battery technology has changed so much in recent years, who knows what's next?

Batteries have an awfully long way to go before they can compete on cost grounds and store a sensible amount of energy. If they do reach the needed power densities, I imagine they'll have truly frightful explosion potential. My interest in batteries stops at lighting, a laptop charger, an efficient fridge/freezer and central heating pumps etc. To actually run electric cookers, big TVs, domestic appliances and so on from a renewable+battery system seems as much of a pipe dream as ever.

> Then do something that makes you feel good with the FIT payments - local CAB, something specifically to do with fuel poverty, whatever.

It seems I could just cancel the payments and avoid becoming a hypocrite on the issue.

Considering the various comments on the thread, the current "best" plan I have to add backup batteries to a house with pre-installed feed-in panels is to leave the panels as they are, but to add a separate battery bank and inverter (not connected to the grid, just "reserve" sockets), with the batteries being trickle charged from the mains, perhaps under relay control so they only charge when the panels are running. I could always then install some DC switch gear and a charge controller to divert the panels to the battery bank in a long power cut. As others have said, it's probably cheaper to have a generator though!
Post edited at 11:00

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