Home energy use - best way forward?

[Cloudscape]

Biff's energy and climate-change threads have definitely got me thinking.

I moved away from the press-button simplicity of a mains-gas combi-boiler. The ease of use encourages you not to even imagine the stuff that's coming through the pipe and being burnt.

Now in a gas-free area, I have a solid-fuel Rayburn, and an antiquated oil boiler. I'm much more conscious of the resources I'm using. I'm used to the Rayburn (heats kitchen, and used for cooking and hot water). I'm quite fond of it, even if the dust fallout covers the entire kitchen and beyond. The oil tank for the boiler is large, metal and indoors. My first thought is that it would be better if it was smaller, plastic and outdoors. But I quite like the idea of getting rid of it altogether.

I don't think I'd easily get away with swathes of solar panels. I don't really have the funds needed for geothermal wotsits, or the space for a windfarm.

In the medium term, would a wood gasification boiler (replacing all heating and hot water) improve my energy efficiency or make things worse? I wish they didn't need electricity, but I wondered if I could have enough solar panels to run that part of the equipment.

I would still need to cook on something.

As a "boy's toy" , a wood gasification boiler looks like the more exciting end of home heating:

http://www.youtube.com/watch?v=2jm7_h6HZF0 (there are lots of refs and videos online about these boilers)

Would a boiler like this have higher running costs, or involve a lot more work than I am doing at the moment?

 

[MdB]

Available in the UK solar photo voltaic are currently ungreen products to my current belief. They are improving all the time, but typical energy used in construction compared to energy produced is not favourable. I've yet to hear of a solar PV factory that runs off its own products to power the complete construction of the devices. I would very much welcome being corrected on this as it would suggest things have improved.

I would therefore currently suggest you forget about solar PV. Solar hot water on the other hand is I believe well worth considering.

I also consider small scale wind generation as ungreen. The energy produced versus the cost (and hence energy used in construction) of wind generation goes up with the size of the blade, so the bigger the better as far as the economics go.

For heating your home I would suggest you look into heat pumps as a heat source. It is not for every situation but they are something like 150% efficient at turning oil/gas at the power station into heat in your home. The best gas / oil boilers are something like 80% I believe. I can't give an exact figure but I believe that heating my 4 bed detached house is approx £300 using the heat pump. It was around £800 on gas. Installation was approx 20% higher than the equivalent oil based system but this will pay back in about 2 years.

 

[Flyfisher]

Shame you're so far away Cloudscape - I'm open to offers for a 2500 litre plastic outside tank with about 1500 litres of oil left over from when we sold our Rayburn. Not that it would solve your longer term concerns, of course.

I share your concerns too and often find myself going round in circles thinking about the options; from woodburners with back-boilers, gas boilers, heat pumps and even using our paddock to grow hay, short-rotation willow/hazlenut coppice or something else for a biomass boiler. Current thinking is the wood burner/back boiler option to start with as it's relatively cheap and simple. Looks like I'm running out of time for this winter though - where does the time go?

MdB's heat pump figures look impressive though, but I don't think underfloor heating (which is best, I've read) is really an option for us.

 

[Cloudscape]

Shame, Flyfisher, but thanks for thinking of it. Anything larger than a 1000-litre tank would be hard to hide. :?

MDB, I've only read a bit about heat pumps. I don't really understand what's required. Does the heat pump work with a conventional system, or is it a completely different system? Is yours ground or air source? Is air source viable in the UK?

 

[biffvernon]

We use a straw-burning boiler to heat our house (along with a couple of woodburning stoves). I bought the straw-burner 22 years ago and the only thing that's gone wrong so far is that a bit of chain connecting the thermostat to the air inlet flap rusted through and was replaced by a piece of baler twine about five years ago. (I've no idea how civilization will survive in the post-oil era with no baler twine.) I'd recommend a straw-burner if you leave near a source of cheap straw, have no immediate neighbours, have a shed to store the straw, have space to dump the ash, don't mind the work of stacking straw once a year, carrying straw every day, clearing out the ash every week and waking up to a cold house. To many ifs for most people but it works well for us.

 

[Penners]

Cloudscape - the problem you;re faced with is not limited to the fuel that you burn.

If your house is already equipped with a solid fuel Rayburn and an oil-fired boiler, both of which are functional, then you have to take into account the environmental impact of scrapping those devices and asking mankind to build you a new heat source of some kind - all of which involves the donation of more carbon to our already overfull atmosphere.

Whether your subsequent use of a more friendly fuel would offset this is (ha-ha) a burning question.

 

[JoceAndChris]

I would still need to cook on something.

I don't dispute you do my dearie, and having read of your wonderfully imprecise cooking style in the last aga thread I'm sure the results would be very interesting!

However I would like to take the opportunity to lament the passing of The Chop House. In Dickens, and all other major literary works of the eighteenth and nineteenth centuries, the gents are always calling out for lightly grilled soles and devilled eggs. It wasn't always perfect, in Great Expections the smallness of the room imposes "on the waiter the wandering habits of putting the melted butter in the armchair, the bread on the bookshelves, the cheese in the coalscuttle, and the boiled fowl into the bed in the next room" (which sounds a lot like me on a dizzy day).

How could we replace this with take away pizza. :evil: :evil: :evil: Why must we be so self sufficient? Think of the industry, the employment, that would be created if simple, cheap, nutritious meals could be delivered thrice daily as a matter of course from prosperous inns and coffee houses to the hapless bachelor or overworked wife. And it would surely have a highly beneficial environmental impact as well.

Being freed from the impetus to cook, we could all get on with far more exciting things, such as writing our autobiographies or taking up fencing.

 

[Cloudscape]

At the moment, the Rayburn chuntles along, producing (usually) sufficient hot water and being the oven, hotplate and kitchen heater. I got a strong hankering for properly grilled cheese on toast the other day, and we don't have a grill. Anyway... this "hapless bachelor" (thanks for that image, Joce :roll: ) would once in a while like to cook something that requires more-precise heat control, but I could live without that if I must. Pass me another bowl of gruel! My misgivings about the Rayburn are the fuel, the gases given off and the ash that would poison the garden if I spread it about.

I take your point/s, Penners. The oil boiler is functioning - just using about twice as much oil as a modern one. I can't see any way of improving its performance. The tank must be moved (currently internal) sometime, so I could get rid of the oil tank altogether, if I had a Plan B.

Hmmm... since everything I might do to use fuel more efficiently involves scrapping something, and therefore wasting resources, then the best plan of action is to do nothing at all. :? Actually, I quite like that plan. I'll just put my feet up and read a book.

Can anyone explain how a heat-pump improves boiler performance, what the heat pump looks like, and where it is normally situated?

And is a wood gasification boiler even a step in the right direction?

 

[robgil]

Shame you're so far away Cloudscape - I'm open to offers for a 2500 litre plastic outside tank with about 1500 litres of oil left over from when we sold our Rayburn. Not that it would solve your longer term concerns, of course.

I share your concerns too and often find myself going round in circles thinking about the options; from woodburners with back-boilers, gas boilers, heat pumps and even using our paddock to grow hay, short-rotation willow/hazlenut coppice or something else for a biomass boiler. Current thinking is the wood burner/back boiler option to start with as it's relatively cheap and simple. Looks like I'm running out of time for this winter though - where does the time go?

MdB's heat pump figures look impressive though, but I don't think underfloor heating (which is best, I've read) is really an option for us.

oooh , sorry to butt in guys but is this tank bunded?
do you have the dimensions for it Flyfisher?

 

[Flyfisher]

Cloudscape, simplistically, a heat pump is the same your fridge, which has two 'radiators'; the one inside the fridge collects heat from the inside of the fridge and the heat pump dumps this heat to the radiator on the outside of the fridge, usually at the back. That's why the rear of fridges get warm - it's the heat from the cool box being dumped.

In a heating system, the 'hot' radiator remains inside the house (often in the form of underfloor heating pipes) and the cold radiator (often in the form of long pipes buried in the ground) is outside the house. Effectively, the heat pump cools down the outside ground and moves the heat indoors, so your house becomes a sort of 'reverse fridge'.

The units I've seen look similar to a large boiler (i.e. a fairly nondescript white cabinet) and can be located indoors or in an external 'boiler house' Their innards are quite different, of course, and the main component is an electric motor to drive the compressor and pumps that make the whole thing work. So, you use electricity to run the motors but you get more energy from the outside ground (or air or water) than you consume, and that extra energy comes from cooling the outside. The ratio of what you use to what you get back is the efficiency, which I understand is at least 300% these days. There is certainly no issue with the basic physics of the things.

 

[Flyfisher]

oooh , sorry to butt in guys but is this tank bunded?
do you have the dimensions for it Flyfisher?

Robgil, I've sent you a PM.

 

[MdB]

The bit that most people don't get is that a heat pump is called a heat pump becomes it pumps heat. It takes heat from something making it cooler and moves it to somewhere else, making it hotter. Moving heat is far more efficient than generating it directly.

In our case, our back garden is where the heat comes from. Water is pumped into it at 5°C and it is returned at about 7°C. i.e. the warmth of the ground is transferred into the water cooling the ground a bit. (The ground itself gets its heat from the sun during the summer.)

The compressor + refrigerant loop in the heat pump cools the water coming from the ground by 2°C before returning it. It uses this energy to heat the underfloor heating loop. It leaves the heat pump and enters the house at around 40°C and returns at around 30°C.

This is me switching on our heat pump for the first time.

As you can see, there isn't much to it.

This is it with the lid on. (outside loop pipes not fitted)

It is up high to avoid air locks and isn't strictly necessary.

The above unit uses 1.5kW of power to run it and produces 6kW of heat. 400% efficient.

It is about as noisy as a loud fridge so we have it installed in the garage. I did the complete install myself and didn't find it difficult. Getting the pipes in the garden was hard work though...

Cost for heat pump, pipes, coolant, underfloor pipes, manifolds etc was approx £6.5k less £1.2k grant from the government making it £5.3k. An oil boiler + tank + radiators was about £4.5k.

Downsides to heat pumps:

1) Your house needs to be very well insulated. With a normal boiler, its output temperature power rating is high so (if you can afford it) you can keep chucking heat out to get the house to a sensible temperature. With a heat pump, the rating will be a lot lower as there is a limit to the amount of heat you can get into the underfloor system due to the low operating temperature. You therefore need very good insulation so as to keep the heat in. We have 100mm celotex in the floor and in the front wall and currently about 300mm in the roof. The rest of the walls are currently uninsulated though this will change sometime into the future.

2) It doesn't work sensibly with radiators. Due to the low operating temperature you would need x3(?) more radiators for the same heat output which isn't really sensible. Underfloor is the way to go which is fine for downstairs but isn't great for upstairs. We have gone down the route of having no heating at all upstairs (apart from towel rail in the bathroom). So far this looks like it will be OK due to the insulation keeping the rising heat in. The house isn't finished yet so we may have to review this.

3) With current gas / electric prices, if you have access to mains gas, this is likely to be cheaper way to heat a house.

 

[JoceAndChris]

At the moment, the Rayburn chuntles along, producing (usually) sufficient hot water and being the oven, hotplate and kitchen heater. I got a strong hankering for properly grilled cheese on toast the other day, and we don't have a grill. Anyway... this "hapless bachelor" (thanks for that image, Joce :roll: )

I didn't mean it personally.

I think this is a very useful thread. I've also battled with the same issues, and have the same unfulfilled longings for cheese on toast!

 

[Schoolmarm]

Flyfisher, what can be done with heat produced from that set up? Is it only for underfloor heating or can it heat radiators?

I am unhappy with our oil boiler even though it is only about 6 years old and far better than our last one. Well actually the boiler is great but I hate using oil




ooops crossposted with Mdb's very informative post.

 

[MdB]

The advantages of heat pumps can be seen here: http://www.playtheregs.com (use bill@microsoft.com as the email address)

If you put in the worst possible values for U values, window size etc into the calculation, you can still pass the regs by having a heat pump fitted due their high efficiency.

 

[worms]

I'm a bit surprised that there has been no mention in this thread of building in an accumulator tank as a universal recipient of the heat output of the various devices that can generate our domestic heat. Looks to me like a good option for coping with the different temperature outputs and requirements and cope with the differing times of heat demand and supply (including Biff's cold morning scenario).

Is there a problem with this approach that I am missing?

 

[MdB]

I'm a bit surprised that there has been no mention in this thread of building in an accumulator tank as a universal recipient of the heat output of the various devices that can generate our domestic heat. Looks to me like a good option for coping with the different temperature outputs and requirements and cope with the differing times of heat demand and supply (including Biff's cold morning scenario).

Is there a problem with this approach that I am missing?

This link might be of interest to people looking into this further. Gives a feel for some of the complexities anyway with a mixed system. Ours was a lot lot simpler.
http://www.kensaengineering.com/Library/AIS%20sheets/AIS%20Space%20heating%20and%20DHW%20with%20buffer%20vessel-01.pdf