Renewable heating dilemma

[skier-hughes]

I reckon I get through 2 x tonne builders bags of wood each week

Lordy!

When you are in the house all day and tending to be sitting at a pc working it gets a bit cold when it's -7' outside and blowing a gale I can use nearly a whole bag in two days. Luckily Jo goes away now and then and I do some proper work, like building so the fire only gets lit at night

 

[dalivar]

Oh yes 30m, I did mean 30metres but apparently its more like 100metres and I underestimated! I will plan to speak to the suppliers and see what they say, and skier thankyou for all the details, I will come back with questions shortly!

 

[dalivar]

Now, I have thought of one problem with the gas main and that is by extending it they would need to disrupt a major A-road from Wales towards Chester, the A494 for the locals. That wouldn't go down well and but apparently if enough of the neighbours want it, it could be done, so says my immediate neighbour. I imagine that most people currently without gas have got perfectly functional oil boilers and wouldn't be in a rush to get connected. So, I will carry on and discuss it with the gas board.
Skier - is your accumulator upstairs and burner downstairs? Do you have a pump to distribute the water from the back boiler? Currently, because the downstairs ceiling is the upstairs floorboards we are pondering running the water pipe directly up the chimney into the loft space and across and down to the accumulator in the bathroom. This would need to be done before the chimney is lined and filled with vermiculite.
Is that a stupid idea?

 

[AMc]

And in addition to those valid points, what about the technology variables? Will PV systems generally become cheaper and more efficient, thereby significantly reducing the payback times?

During the lifetime of the 1st wave of FIT the cost of PV panels worldwide dropped substantially and due to increased demand and competition in the UK the price here dropped even further. This was one of the reasons the FIT rates were dropped. At one point a 4Kwhp system was returning >9% on the capital investment (IIRC).
My pals who are MCS installers both said that the payback remains attractive, but not as nice as it was when the installers were fighting to the bottom and the FIT still assumed 10K for a 4K system. The one thing that is a given is that electricity will get more expensive and I would hazard well ahead of inflation for the foreseeable future. At the moment the domestic PV market is dead but there is a lot of commercial installation, which I think tells you the bonanza is over on FIT but the long term economics remain sound.

I've been watching PV for many years, the technology is mature with university materials research projects getting <0.1% improvements in efficiency which make them newsworthy in the field. The chances of a great leap forward in efficiency are pretty remote. I suspect that transparent PV, printable and curved panels will help to make more installations possible but I doubt there will be a dramatic improvement in the amount of electrical energy we can get out of a roof mounted array.

My Dad was looking into solar thermal to try and reduce his oil hours out of winter, I pointed out that he could use the surplus PV he generates to run an immersion without any captial investment - you get paid for generation even if you use it on site. If you're prepared to invest a few hundred quid there are devices that control the heater linked to generation so you only heat water when you have spare juice. He has been tracking his generation and was surprised that last March was his best month, better than high summer thanks to a lot of cold, clear days.

 

[Flyfisher]

Interesting points - thanks for that.

I accept that there may be no great breakthrough in PV technology on the horizon but conversion efficiency is not really that important when the actual energy source itself is free, i.e. the sun. So, even if the conversion efficiency remains constant, it's really the basic cost of the panels that can have the biggest impact to the overall economics. I'd be more confident of manufacturing costs coming down as volumes increase, rather than technical breakthroughs increasing the conversion efficiency.

Having said that, if the panel costs do drop significantly, the available roofspace may soon be filled and then we'll need higher conversion efficiencies to increase capacity - though I suspect we're a way off that point just yet.

Funny you should mention using solar PV to power electrical heating as I've often wondered about that myself. We tend to think of electricity as too expensive for heating but if we're making our own surplus anyway then why not?

Interesting times.

 

[Flyfisher]

Now, I have thought of one problem with the gas main and that is by extending it they would need to disrupt a major A-road from Wales towards Chester, the A494 for the locals.

I'm certainly no expert but I wouldn't automatically assume that. They used a 'mole' for parts of our installation and it may be possible they could do something similar to get under the road with no disruption at all. But I don't know enough about the technique to understand its limitations.

 

[skier-hughes]

Skier - is your accumulator upstairs and burner downstairs? Do you have a pump to distribute the water from the back boiler? Currently, because the downstairs ceiling is the upstairs floorboards we are pondering running the water pipe directly up the chimney into the loft space and across and down to the accumulator in the bathroom. This would need to be done before the chimney is lined and filled with vermiculite.
Is that a stupid idea?

A 900l accumulator is quite heavy and physically large. Ours is 2m tall and about 1m in diameter. 900l of water is 900Kg, then you've got the tank weight etc. You'd need a good upstairs floor to support it.
We have a low loft, which is upstairs to the fuel store, but as unlived in space we erected Oak supports under where the tank is.
The low loft is adjacent to the lounge where the boiler is, so it is a short 2m run of pipework.
We have a million and two pumps.
The fire has a sensor that turns on the pump when the water in the back boiler reaches a certain temp.
The same goes for the solar thermal.
There is a pump for the heating and there are two pumps for the oil fired rayburn, which heats the water via a heat exchanger as well.

 

[skier-hughes]

This si what the fire looks like after fitting the surround, it now also has two oak shelves and we store wood either side.

 

[AMc]

Having said that, if the panel costs do drop significantly, the available roofspace may soon be filled and then we'll need higher conversion efficiencies to increase capacity - though I suspect we're a way off that point just yet.

Funny you should mention using solar PV to power electrical heating as I've often wondered about that myself. We tend to think of electricity as too expensive for heating but if we're making our own surplus anyway then why not?

Interesting times.

From what I've read the panel costs have more or less halved, I'd be surprised if they went down much more in the depressed UK market unless there is a change in the underlying tech. - I was once quoted £14K for 3.6Kwhp (2008?) and the last time I looked into it in late 2011 it was £5.5-£6K. A substantial part of the cost being the scaffolding and installation work rather than the hardware.

To be honest running the immersion off the PV is more a quirk of the FIT distorting the true cost of power than an efficient way to heat water. Solar thermal should out perform PV, m2 for m2 but if you're being paid for the electricity and you get to use it for nothing it makes financial sense to do it. In that particular case there was also the issue that the hot water cylinder was at one end and the most suitable roof was at the far end of the house. Using the existing wiring, panels and heater makes a lot more sense than running new pipe 20m or so through the house or relocating the cylinder etc.

I originally intended to put PV and solar thermal on this house but the project straddled the point when the grant funding for Clearskies was stupidly over subscribed and the FIT wasn't defined. In the end my MCS installers both said that the service costs associated with solar thermal would probably outweigh the cost savings of running my air source heat pumps in the summer. While solar thermal is free energy it does rely on mechanical pumps etc. which need to be looked after, vacuum tubes that can fail etc. PV is simpler in that it has no moving parts, the service life of the modules is pretty carefully defined and while the invertors are potentially expensive points of failure they don't need to be maintained.

 

[skier-hughes]

I need to maintain my solar thermal?
I've not done anything to it in the last 5 years.......
What do i need to do?
It has some electronics to tell it when to switch the pump on and off and (what appears to be a pretty much self contained) pump?

 

[DJH]

I've just come across this in the Daily Mail :roll:

http://www.dailymail.co.uk/news/article-2273321/Residents-eco-friendly-homes-5-6million-complex-complain-annual-2-000-electricity-bill.html

Doug

 

[agbagb]

I'm certainly no expert but I wouldn't automatically assume that. They used a 'mole' for parts of our installation and it may be possible they could do something similar to get under the road with no disruption at all. But I don't know enough about the technique to understand its limitations.

I did some work on developing small horizontal directional drilling rigs many years ago, and spent a good few muddy hours down launch pits at the sides of roads. The main limitation is what the ground is like under the road and what buried services there might be. Hitting a boulder will send the head off course, sand is a pain to steer through and the hole colapses. But if there is plenty of room to work from bigger rigs (in common use these days) can steer deep and get better first time success.

 

[dalivar]

Thanks for that info agbagb, I checked the national grid website and one of the requirements for connection is that our boundary needs to be within 23metres of the main. I don't think we'll persue this, I just can't see them agreeing to do it without a massive cost to us. Also, being more sustainable is real appeal to me (maybe not so much to he who find and chops our firewood though!)
DJH - that article is shocking, how did they get that so wrong?

 

[Flyfisher]

Also, being more sustainable is real appeal to me (maybe not so much to he who find and chops our firewood though!)

The 'sustainability' thing can be quite interesting, depending how far you wish to dig. Is a solution that's not scalable really sustainable? And what about the 'high carbon western lifestyle' that will no doubt be enjoyed by the person who sells you the firewood?

I've read that DRAX is being converted to burn biomass, which sounds like a good idea until you read that most of it will have to be imported from around the world. http://www.bbc.co.uk/news/science-environment-20269615

It's not easy being green.

 

[skier-hughes]

Also, being more sustainable is real appeal to me (maybe not so much to he who find and chops our firewood though!)

The 'sustainability' thing can be quite interesting, depending how far you wish to dig. Is a solution that's not scalable really sustainable? And what about the 'high carbon western lifestyle' that will no doubt be enjoyed by the person who sells you the firewood?

Oh dear
Why can't he lead a simple lifestyle living in a homemade Yurt in the woods from which he maintains the number of trees carefully for a full biodiverse world?

 

[worms]

Why can't he lead a simple lifestyle living in a homemade Yurt in the woods from which he maintains the number of trees carefully for a full biodiverse world?

But only if it is a proper yurt made from hand-spun wool, not one of these modern fake canvas yurts made from industrial cotton... :roll:

 

[worms]

DJH - that article is shocking, how did they get that so wrong?

I'm afraid I would want to see more evidence and background on that story... The electricity bill shown seems to show a quarterly use of £220 for the sep to dec quarter which might not be too bad if that includes all the heating costs.

I believe it Is not uncommon for people to report high costs with new well-insulated houses and air source heating until they learn to use it properly and, if necessary, adapt their lifestyle to suit. For example, if you are used to leaving the back door open when you cook, you won't get the full benefit of a heat recovery system.

Having said that, the roof panels (presumably solar thermal) do look a bit tokenistic!

 

[skier-hughes]

Why can't he lead a simple lifestyle living in a homemade Yurt in the woods from which he maintains the number of trees carefully for a full biodiverse world?

But only if it is a proper yurt made from hand-spun wool, not one of these modern fake canvas yurts made from industrial cotton... :roll:

What else, as he does keep his own goats!

 

[AMc]

I need to maintain my solar thermal?
I've not done anything to it in the last 5 years.......
What do i need to do?
It has some electronics to tell it when to switch the pump on and off and (what appears to be a pretty much self contained) pump?

[Been away] It was a while ago but from memory you were supposed to have an annual check on the coolant levels, pump, thermostats etc. to maintain the warranties on the equipment and prevent failures due to leaks or sticking valves?
What I remember reading was that ST was worth installing if you were a competent DIYer but if you had to pay a "specialist" to look at it once a year it would offset the saving in using primary heating to do summer hot water.
As with many things I think I was being told one version of the story but as two independent installers both persuaded me not to spend money on it I never questioned it further - normally they're trying to talk you into spending money

 

[skier-hughes]

We saw direct energy savings straight away.
Our hot water was done mainly by immersion, and our electricity bill was about £135 per month, we reduced this by £50, with pv now installed we are down to £60 month.
I think we could afford a check from our £600 saving each year, but we weren't asked to do this by our installer to keep our guarantee.