Any reports on domestic wind-turbine cost/benefits?

[RogerS]

Currently mulling over the next ten/fifteen year plan and as the preference is to stay put, I'm looking at energy efficiency.

Carried out an Energy Survey from the EnergySavingTrust website and frankly most of the recommendations are

EITHER:

a no-no since they wil require the removal/destruction of original features (it's an old, old house with original features, oak beams and cornices) and/or major redevelopment such as radiator resiting/replumbing etc

OR

not cost-effective even over a ten year time frame (such as a new boiler). In any event we run the room stat at a low 16 degrees and augment the rooms that the two of us use mainly in the evenings with logfires.

Fitting additional loft-insulation will be a nightmare as the twin gabled roof has zero headroom since the first floor ceilings are at purlin level. Which also implies that there is a slope to the ceiling and getting any insulation down there is nigh on impossible.

Replacing all the windows with wooden double-glazed windows is on the cards ...well, a bit of a no-brainer really for a woodworker......as would be replacing the draughty wooden floorboards in the main reception room with new ones and insulation underneath (other ground floor rooms have solid floors but no insulation there either) but that's about it unless ........

ground source heat pump...but all the literature says that these are only suitable for a well-insulated house...but if I can generate a lot of the electricity and only use the heat pump to augment the existing boiler then maybe that might make sense.....but am I talking tosh? As I type this, the cost-benefit-equation for simply replacing the existing boiler starts to make sense....

and no grants for doing anything renewable as far as I can make out..too busy bailing out banks, I guess.

Comments?

 

[TrimTheKing]

No helpful ones from me I'm afraid, but I am starting to look at both wind turbines and ground source heat pumps myself as my electricity bill is shockingly high.

I have found a kit turbine that will generate 2KW and costs around £800, and you get a 40% grant so not too bad. Just need to work out the logistics and speak to planning (we are in green belt and our planning office are notorious for allowing things that should never be allowed and blocking obvious improvements!!!).

Will let you know what comes from my investigations.

 

[RogerS]

Is that grant local to you? I was thinking about maybe a 6kw turbine but have no idea as to size/practicality. Planning...yes, wondered about that and I can see objections from the local populace. Other concern is noise from the turbine. Does it go 'woov..woov..woov' as the blades go round?

have you checked your average guesstimated windspeed for your location? There is a link on the energysavingtrust.org.uk website..

 

[dickm]

Have looked into most of these things for our house, although the situation is very different in that it's already highly energy efficient, with high insulation, triple glazing and mechanical ventilation with heat recovery. So total heat demand at about -5C outside is around 5kW. BUT, because of the low total demand, previous owner fitted just electric panel radiators and even on a three period so-called cheap tariff, it's not cheap.

I looked at heat pumps, but energetically, they are a nonsense unless you have a renewable electricity source - think about it; at best, they give 4 units of heat for 1 unit of electricity BUT that electricity is generated with, at best 30% efficiency. You would be better off burning the oil directly. And, because the heat pumps run continuously, you end up spending much more than the theoretical 1/4 of the electricity needed.

When we had an old house like your's with sloping ceilings it was difficult, but not impossible, to insert glassfibre into the space below the slates, and definitely helped. Biggest improvement though was probably draught proofing. If I'd known then about heat recovery and mechanical ventilation, would probably have tried it.

Boiler change economics depends on what boiler you have. If it's already more than 10 years old, I'd go for replacement with the most efficient unit you can find, using gas if you've got it (we are 1/4 mile from the main St Fergus high pressure gas line that probably supplies all Scotalnd, but we can't get gas in the village )
Solar heating panels probably make sense if you are working on the plumbing anyway.
Solar voltaic is speculative - efficiencies and prices will probably improve a lot in the next few years.
Wind is certainly worthwhile up here (I've seen the local big wind turbines stationary twice in two years!) but problematic from planning and neighbourliness viewpoint if you have close neighbours.

Enough for now

 

[Night Train]

I am studying a MSc in Architecture, Environment and Energy at CAT and so know a bit about this.

The best thing is always to reduce losses as that in turn reduces energy demand.

As you are going to have a problem with reducing losses by conventional means then some less then conventional ones may be needed.
For insulation Airtec from Screwfix, AluThermo and similar products may be useful though do check on how effective it is for your application. I've not used either.
You can also reduce heat loss through windows by using thick heavy curtains and/or internal shutters.
You can also insulate your fridge. Add extra insulation around your fridge to reduce 'cold' loss through the case. Remember to keep the heat exchanger at the back open to the air.
Think about using a chest freezer as they tend to loose less 'cold' then a conventional upright.
Replace your kettle with one that only boils the water as you need it like the Tefal Quick Cup.

A replacement condensing boiler will be a lot more efficient and if you couple it with underfloor heating then it will be even better as it will run at a lower temerature.

Small wind turbines are often next to useless. If they are mounted too low down then the turbulent and gusty air around buildings prevents them from working effectively. They really need to be high up in a steady wind to work.
You will need to measure the wind speed at the height and location the turbine is to be fitted. Wind speed charts often give speeds that are at too high in altitude to be useful for a small turbine.

Solar water heating is good if you can get planning to install it on your house. The heated water can be used for preheating domestic hot water or for underfloor heating. It is one that really works in the UK if properly installed as it works even on cloudy days.

Solar photovoltaics can be useful but only generate in direct sunlight so cloud is a problem. However, you can use small solar PV to charge batteries for non essential lighting, maybe LEDs.

You can also increase the amount of hand working you do in your workshop and save in the electricity for your machines. :wink:

 

[TrimTheKing]

Is that grant local to you? I was thinking about maybe a 6kw turbine but have no idea as to size/practicality. Planning...yes, wondered about that and I can see objections from the local populace. Other concern is noise from the turbine. Does it go 'woov..woov..woov' as the blades go round?

have you checked your average guesstimated windspeed for your location? There is a link on the energysavingtrust.org.uk website..

Not sure about grant, mate told me about it so will look into it.

Noise would be a definite consideration. so need to look into it in a lot more detail.

A replacement condensing boiler will be a lot more efficient and if you couple it with underfloor heating then it will be even better as it will run at a lower temerature.

Hmmmm, I'm not sure I agree with this to be honest, or at least it creates its own issues. I have quite a big barn with underfloor heating at ground level. House was converted around 6 years ago and was massively overspecced in every area (Insulation is higher than guidelines etc.).

Problem with underfloor heating is that it runs 24/7 to keep the room at an ambient temp (usually controlled by a set back timer which allows -3 from your 'on' periods). My problem in this respect is that basically from Sept/Oct through to Feb/March the water pumps are running 24/7 using all that 'leccy (not to mention the gallons of oil too...)

I need to do something, and quickly, otherwise I am going to be working purely to pay for heat!
:shock:

 

[RogerS]

I am studying a MSc in Architecture, Environment and Energy at CAT and so know a bit about this.

Interesting course. Is it fulltime?

Good website of theirs and they do a book 'Choosing Windpower' - ordered.

 

[Ironballs]

There's a few folks with wind turbines round here as it's windy quite often (Windy Hill is a couple of miles up the road...). They do make a little bit of noise, but it's not too bad. From what I can gather they're fairly expensive to buy/install and don't give a continuous supply (obviously), so can only be considered as a top up and have a payback period of many years

 

[RogerS]

Think I may be onto a non-starter as have just discovered that we are just inside the Malvern AONB. Phone call to planning methinks.

 

[jasonB]

Probably best to just put an extra jumper on :wink:

Was talking to the client where I have been doing quite a bit of work lately and she mentioned that the gas bill for the last quater was £2400 :shock: Well what do you expect if the indoor pool is kept at 80deg and the poolroom 82deg.

Jason

 

[wizer]

the prices are just ridiculous atm. I just can't work out why ours is so high.

I doubt we'd be able to have a turbine here.

 

[Night Train]

A replacement condensing boiler will be a lot more efficient and if you couple it with underfloor heating then it will be even better as it will run at a lower temerature.

Hmmmm, I'm not sure I agree with this to be honest, or at least it creates its own issues. I have quite a big barn with underfloor heating at ground level. House was converted around 6 years ago and was massively overspecced in every area (Insulation is higher than guidelines etc.).

Problem with underfloor heating is that it runs 24/7 to keep the room at an ambient temp (usually controlled by a set back timer which allows -3 from your 'on' periods). My problem in this respect is that basically from Sept/Oct through to Feb/March the water pumps are running 24/7 using all that 'leccy (not to mention the gallons of oil too...)

I need to do something, and quickly, otherwise I am going to be working purely to pay for heat!
:shock:

I guess that you have a heated solid floor? If so then it will probably beset to come on for longer or around the clock to maintaing a low level of heat in the slab.

With wooden floors it would come on and off with a thermostat and timer. With under floor heating the water needs only to be a around 30-35deg C whereas with ordinary panel radiators it would be running at around 60-70deg C thus requiring more energy to raise the water to that temperature. The lower temperature required by underfloor heating would also make it more usable with solar hot water.

Roger, the MSc course I took can be full time or part time. The course consists of ten modules of which you have to complete eight. That can be done over one year full time or two years part time. Each module is a one week residential at CAT running from Wednesday to Sunday inclusive with some extra sessions or meeting on the Tuesday.
It is really good fun as well as educational. Classes start after breakfast at 9.30 and go on to 8.30-9.00pm each day and finishing early on Sunday so people can go home on the train. They also have a real boozing party on Saturday night.

 

[TrimTheKing]

I guess that you have a heated solid floor? If so then it will probably beset to come on for longer or around the clock to maintaing a low level of heat in the slab.

With wooden floors it would come on and off with a thermostat and timer. With under floor heating the water needs only to be a around 30-35deg C whereas with ordinary panel radiators it would be running at around 60-70deg C thus requiring more energy to raise the water to that temperature. The lower temperature required by underfloor heating would also make it more usable with solar hot water.

Nope, pipes laid in channels in some kind of insulation, looks like Kingspan. Saying that, we bought the house in December and I'm not altogether sure, based on some other things I've seen, that the heating is done as well as it could/should be.

I'm having a bit of trouble getting hold of anyone who deals with this kind of system to check it over for me and advise whether it's functioning as well as it could be...

 

[Night Train]

Hmmm, in that case it may be something else beyond my sparse knowledge as to why it is running like that.

The theory is that the temperature should be maintained by a thermostat so that the room has a nice even temperature gradient from the floor upwards. The floor should be an even, but low warmth so that it is comfortable to walk on in bare feet while the air is not being too warm at head height. It should click on and off to maintain this.

Of course it could have a slow flow rate so that the water gives up all of its heat by the time it returns to the boiler and so the boiler never stops running to put the heat back.

A heat store might be beneficial here. Use the fuel to rapidly heat a store to a high temperature and then shut down. The heating water can then transfer the heat to the floor at a controlled rate.
The heat store can be masonry or a water tank and you can heat it with a biomass batch boiler to burn your wood off cuts and use solar heating when it is available.

 

[MikeG.]

Mark,

it sounds like you have problems! Could you give a brief description of the build-up of the floor, and also your walls and windows?

-

Back to the original question:

Power output from a wind turbine has a cubed relationship to the area swept by the blades. Therefore, if you double the size of the swept area you get 8 times the power output. Triple it you get 27 times the power output, and so on.

Furthermore, turbines need to be in "clean" (ie non-turbulent) airflow, and windspeed at 10m above the ground is typically double what it is at ground level. Rooves and trees disturb windflow enormously.

So add this all together and it is quite clear that there is no case whatsoever for domestic scale wind-turbines (except for recharging caravan and boat batteries!). Wind-turbines should be done on a communal basis.........villages and towns could & should invest in their own turbines to serve the whole community. I think the government has just moved to sort out the payment for electricity sold back to the grid, so this is now, apparently, viable.

I know I have done a discourse on photo-voltaics on here previously (12 years on average before the energy that went into their production has been repaid by the energy output .........UK only!!..........these things are brilliant in sunny climates). With a 20 to 25 year useful life, the current generation of collectors is not the answer in our climate.

But..........huge but......... solar hot water systems should be installed at every possible opportunity! They work brilliantly.

I have been a member of CAT for about 20 years, and seriously considered doing their course (MSc)..........but felt it may have been a case of preaching to the converted!

Mike

 

[dickm]

Don't entirely agree with you, Mike, about domestic turbines. There are several in our neighbourhood that are working well, and with the new feed-in tarriff will make even better sense. OK, we've got an enormous wind resource up here (just look at the flattened plants in our garden!) but an old colleague in East Anglia has a turbine which, after a whole series of mishaps, is also beginning to pay off.
Agree that if possible, the bigger the better, and with current technology, they are a complete no-no in towns, but don't just dismiss the domestic size in rural areas.

It will be interesting to see if Derek Taylor's idea of "aeolian roofs" has merit in urban areas.

 

[MikeG.]

Dick,

"working well" is fine..........but give us the figures!!! How much electricity are they producing in a year? What is their blade length/ swept area, and where are they mounted?

By "domestic scale" I am referring to the units sold for mounting on a roof, as opposed to those that can be independently mounted on towers. I would be extremely sceptical of the efficacy of any turbine with a diameter less that, say, 2.5m, on an independant tower less than 10m tall standing clear of trees and buildings.

Just as an indication of how powerful the cubed relationship between swept area and output is, one 6m diameter turbine potentially produces as much electricity as 729 2m turbines (and I bet doesn't cost anywhere near 729 times as much!).

Which would you rather see..............? Which solution is more efficient in terms of "materials in..........energy out"?

No, if you truly want to do something "green" (how I hate that word!!!) in terms of wind power, chat to all your neighbours and see if you can share a turbine.

Mike

PS (edit) I have just found some figures for a 5' diameter machine, at the higher end of the efficiency available. In a 10mph wind it will produce around 35W........enough to run 2 low energy lights. In a 20mph wind, 280W.............not enough to boil a kettle. These little things are just not the way forward!

 

[MikeG.]

OK, Ignore all of the above...........it serves me right from trying to do all these things from memory.

Power output varies with cube of the windspeed (not swept area). Power output to swept area is a linear realtionship (double the area, double the power output)...........so power output to radius/diameter is a squared relationship (double the diameter, 4 times the output, triple the diameter, 9 times the power output etc.).

So my earlier example of the 2m turbine and the 6m turbine...........the 6m one will turn out 9 times as much power. Your choice is one 6m turbine or nine 2m turbines.

Whatever you do, don't take any notice of the rated output of a turbine.............this is only a statement about the size of the generator.

Sorry for the conmfusion.............but the net effect is still that bigger is better.

Mike

 

[thomvic]

When you calculate the payback period for your investment don't forget the loss of interest on your investment (or cost of interest if you are borrowing). For example - you may be told by sellers that an installation costing £4000 will save you £400 p.a. (highly improbable anyway) so payback is 10 years. Not so at all. The capital payback period with average interest rates at, say, 4% would be in excess of 16 years. This may well exceed the life of the investment. In which case it is a loser! You also have to add the maintenance costs.
Perhaps more significantly for many of us, when you have spent the capital you have lost the opportunity to spend it on something else that you may prefer.

Richard

 

[Night Train]

Mike, you should look at doing the course, it is great fun as well as putting some up to date facts to support your thoughts.

Wind turbines on domestic urban houses are a waste of time unless they fall foul of planning ie: too big and too high.

People in towns and cities often don't know what real wind is, they experience the occasional gust but that is about it.
In the wilds of the countryside, on a hill top there is sometimes real wind, enough to run a turbine, if it is big and tall enough.
Scotland is a different matter altogether. Ther is wind there and the houses are designed to cope with it but even there the installation needs to be correct and suitable fo rthe location.

I have an ex student who got together with his neighbours to get permission fo a 6kw turbine. It will work for them because they are a line of cottages on the top of a hill in the middle of nowhere and they have spent over a year surveying the wind in the proposed location.