I wondered if anyone had any advice to offer before we make a final decision.. We are converting a steading (Scottish for barn !! ) into a house. We have already decided to have geothermal heating running an underfloor heating system. Whilst looking at some of the leaflets we have acquired, one company recommends using a manifold similar to the UFH one and running all the taps etc off individual flexible plastic pipes. We can see the sense in this as it makes it easy to isolate one particular outlet and using flexible pipe means there will be few if any joints. But... we have been told horror stories of mice nibbling the said piping inside the wall cavities. Since it is almost inevitable we will have mice I wondered how great the risk was and if anyone had experienced it. Thanks in advance if anyone can help
Well we have 100% plastic pipe (water is so acidic copper pipe dissolves in
5-10 years) and regualr mice intrusions. There's lots of things they'd rather chew - Rockwool appears to be a favourite - so if you wrap the pipes in Rockwool they'll go for that first.
If you're really worried you could coat the pipe (but not the joints) in something like that non-drying anti-burglar paint but I doubt if it's required.
What heatpump are you using ? Looked at this a while back but even with subsidies the payback wasn't there.
We've got a quote from Geothermal Scotland of £8000 so with grant it will be about 5000. We are then thinking of looking at the domestic windmill which are just short of a grand (and there is a subsidy on them as well ) the windmill will provide more than enough electric to drive the pump so costs after that point should be negligible.
A windmill does change the equation if you can get about 3kW of free electricity out of it when you want. Our national park doesn't like windmills so we started looking at a hydroelectric generator to do the same thing but it just got more and more complicated getting the permits so eventually we went for oil.
When using a windmill you must use a largish thermal store or heat bank. This is to store heat for when the windmill is not turning. You want to store as much heat as possible and not waste free energy. The windmill just heats an immersion in the heat bank. Preferably have, "very" low temperature underfloor heating, so, that when not fully turning the heating may operate properly on low temperature water.
A windmill is preferable in a windy location, as they perform just as well in summer as in winter. Heat pumps underperform in winter, at time hardly capable of producing DHW hot enough.
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These are the windmills we were looking at. Not much larger than a satellite dish. There was a big publicity thing when one of the members of the Scottish parliament got one fitted to his house (Don't know who - don't do politics !! )
You can't get a windmill for £1k that outputs 3kW. You'd be looking at around £30k, and it would be very tall indeed. You'd also need a very large bank of batteries.
And, even if you could, a turbine is rated at its nominal maximum. A 1kW turbine will produce only 300W on average. Once the batteries are charged then any power generated is dumped (though you can use this dump in a reasonably configured system). In our high wind area we effectively get about 10% of the rated capacity out of our turbine. A lot of the time it just turns itself off because it has nowhere to put the energy.
Doubling the number of turbines without considering how you are going to use them is a false economy.
But could work out cheaper depending on how you use them. You also redundancy, which in an isolated location is desirable. Best not to have batteries. At the mo', expensive and don't last long - although battery technology is coming on brilliantly.
Couple the windmill directly to the immersion of a thermal store, then all the wind energy is transformed to heat energy, which is stored in the thermal store. When you use an intermediate battery you loose quite a bit of energy. Then this is used for low temperature UFH and DHW.
Redundancy comes at a price if it isn't needed. Our redundancy is having the fall back of two diesel generators and some solar PV panels. Redundancy needn't mean unnecessary duplication. Wind turbines need masts, planning permission, building mount points, charge controllers,...duplicating all this isn't straightforward. Also, the chances are if a storm is powerful enough to damage one turbine there's a good chance it will damage both.
If you are in an isolated location and you are using the turbine for electricity as well as heat then you need batteries (or some sort of pumped water storage system.) Yes batteries are expensive but used correctly they'll last 10 years or more
Yes, but when the thermal store hits its max the turbines are then doing nothing. That was my initial point. Having two turbines heat the water twice as quickly is of no use if you don't use the heat quickly. A second system such as direct solar water heating would make more sense here.
You lose energy in all processes. It's managing energy use and loss that makes the difference.
You size the thermal store to suit. Large enough so a windmill would not full heat it. The maxium heat store temeperaure copul be 90 degree C. That will take a lot of wind to heat up a large thermal store. Even over summer I doubt if a widnmill would full charge a correctly sized thermal store A windmill giving 1kW will take a time to heat a large thermal store. With stored water the hot water rises to the top. This means you always have a tap of hot water from the top and lots of cold water below for storage. A thermal store may have solar panels heating it.
You store the heat. A 1kW turbine is really not that big.
The windmill works in winter as well, while solar panels may be ineffective for days on end in winter and only work for a few hours on sunny winter days.
You loose far more with an intermediate battery between the generator and the element, than using a directly heated thermal store.
I think News was addressing your comment that it turns itself off as it has nowhere to put the power. Heating a thermal store of 1m^3 takes about 1Kwh per C. Going from 40C (UFH temps) to 95C would absorb some 4 days continuous output. And it's relatively easy to make larger thermal stores.
What we had been initially thinking of was a geothermal system with the windmill to help drive the pump running the geothermal. The windmill that was recommended plugs into the household mains and feeds any excess back into the grid. (I can't see there being much excess !! ) We had solar panels on the old house for 25 years but the amount of heat this house will need. Geothermal seemed the way to go.
But back to my original question :-) Has anyone any experience of mice chewing flexible plastic piping?
The underfloor heating company have a system where all the taps etc have their own outlet on a manifold and so there are few joins. But we have been told that mice might be a problem
A whole full solar roof is far different from a panel or two and may cost less than the 8k for a geothermal heat pump, which you have to pay to run. A solar roof is just the cost of running a pump. A windmill to give 3kW output to run the heat pump will be not be cheap either. At best a heat pump can compete with a natural gas boiler in running costs. You may, if lucky, drop the running cost by 1/3 by using the windmill. Still overall an expensive setup using a windmill/heat pump.
A heat pump may have a COP of say 3. That is for every kW you use it outputs
3kW. But in winter you will freeze, or make the ground very cold, so less heat is available to pump into the house. Then the COP drops. When the ground gets very cold around the bore pipe, the heat pump may not be capable of raising the water to DHW temperatures. For example, a heat pump with a COP of 4 takes 1 unit of electrical energy and pulls 3 units of heat energy from the ground, water, etc, to supply 4 units of heat energy where needed. If the heat pump cannot pull the heat energy from somewhere, the COP drops back to 1.
Then expensive to run electric immersions have to be used, as well aslso with a COP of 1.
This thread has thrown up alternatives and appear to be more economical options:
A full solar roof heating a thermal store that provides UFH and DHW. You may need a backup immersion in the thermal store for cloudy days.
A directly connected windmill constantly heating a large thermal store. There again some backup heating on windless days, but the thermal store sized large enough may hold enough energy to keep the house warm enough until the wind picks up. An immersion may be required for the hotter DHW.
If I was you I would reassess your proposed heating system.
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We've got miles of plastic pipe. And regular mice intrusions. But they prefer Rockwool. So wrap the pipe in Rockwool (which helps insulation) and you'll be fine.
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