Going greener with wood gasification

[chrick]

I recently bought a house (in Chester, NS, Canada) which is heated with in-floor radiant with an electric (slant-fin) boiler. The hot water is an electric 40 gallon tank. There is a small wood stove in the living room (DutchWest 1000, the plate steel model) which has been keeping up with the load so far, but once it gets a little colder it will fall behind and we'll have to fire up the boiler. The house is ~2000 sq. ft., and pretty well insulated (R-40 with no thermal bridging in the roof, R20 in the walls, double-pane modern windows).

We also have a fairly large outbuilding (~1400 sq. ft.) with electric baseboard upstairs and an oil stove downstairs. It is also R40 in the roof and R20 in the walls, with double pane windows. We have a second small outbuilding ((~200 sq. ft.) which is not yet insulated or heated, but I'd like to do so in the next couple of years.

I had been considering solar hot water panels to supplement the various systems, but it turns out that we have poor exposure due to trees both on our property (that we don't want to lose) and on neighbour's properties (that they don't want to lose!).

I'm now considering geo-thermal (we're on a lake) and a wood boiler.

The wood boiler system I'm envisioning would have the boiler in the large outbuilding (downstairs is my workshop) with a large, very well insulated heat storage tank in an appendage to the space that I'd build. I would put a smaller storage tank in the house (space limited, no basement, small utility rooms) which would get it's heat from the big tank as needed. Once I put heat in the smaller outbuilding it would do the same, on a smaller scale.

Heat into the outbuilding would come from some hydronic loops I'd mount on the walls and ceiling downstairs, or alternately some low-temperature radiators. Heat in the house would still be the radiant slab, but the heat for it would come from the remote tank instead of the electric boiler (electric boiler would still be there for times when we were away and didn't have a fire going in the outbuilding's boiler). Domestic hot water (in both the outbuilding and the main house) would be pre-heated by the hot water tanks through a heat exchanger, but would still be electric tanks (the one in the outbuilding is usually off, however). Heat into the small outbuilding would be low-temperature radiators.

Does this sound like an over-complicated system? It would require trenching in lines from the outbuilding to the house, and eventually to the small outbuilding. It would require multiple storage tanks and sensors, and a control system which I can't imagine would be off-the-shelf. And it would require a really well insulated main storage tank to be useful in the shoulder seasons when we wouldn't need to run the boiler that often, to prevent losing the heat before we can use it.

To me it doesn't seem much/any worse than a solar system or geothermal - but I haven't installed something like this before (my last house had a wood stove large enough to be the primary and electric baseboard for when we were away), and I don't know if it's over the top.

Any thoughts would be greatly appreciated!

Thanks,

Chris

 

[pybyr]

If you are considering building an "appendage" to a building for a tank, anyways, I have a one word answer for you: GARN. That way your boiler and storage are simple and robust, both in the extreme.

From there, you can tie in the various heat loads as and when you please.

 

[Hunderliggur]

And no matter where you burn the wood, one storage tank is sufficient. Well insulated underground lines are the answer. My boiler is is a building 80 feet from the house, and other 80 feet in the basement to the tanks.

 

[benjamin]

That seems reasonable to me. Makes way more sense than all of that electric heat.

I'm glad you decided against the solar heat. There's very little solar available when we typically need heat, that's why we need the heat, right?

Hopefully you meant geothermal OR wood, geothermal is so expensive that it doesn't make sense to install it as a backup.

Otherwise I think everything makes sense. It might not even be that complicated to control, depending on how you want to do it. The small remote tank in the house isn't needed unless that's the heat exchanger for the domestic hot water? The electric water heaters will work fine for storage tanks with built in back up. I certainly wouldn't call it an over the top solution for what you are trying to do.

 

[Como]

I would agree with the above. The unnecessary complication seems having multiple storage tanks.

Essentially you do have multiple zones with different heat loads, several in the house, maybe one each for the outbuildings.

Your hot water requirement will require a tank in the house, maybe in the other buildings?

First thing is you need is numbers, the heat load for the three buildings. I am going to guess somewhere in the 150,000 btu area peak? Maybe half that normal?

The Garn site has a couple of spreadsheets that might help, simple but would get you going.

 

[rkusek]

Yes, cut the storage tanks back to just one location, probably adjacent to the boiler. Read the primary secondary sticky at the top of this page. I think that may be the easiest way to connect all the loads and should make the control scheme easier to manage. Foamed in trench pex or Thermopex would lose very little heat from the main tank. Geothermal would be a pretty expensive backup even with a lake nearby. I would bet that would cost $25,000 for 5 ton system very similar cost wise to the kind I see here with the return wells or the veritical "slinkys". Relatives of mine in the middle of Nebraska have more abundant ground water and are allowed to use the "pump and dump" setups were the extra wells or pipe loops are not necessary. This brings cost down considerably (way less than 1/2) since you only need the indoor unit and can utilize the existing well. The amount of water discharged is hardly noticeably too and most of them can provide almost free hot water in summer. But I'm guessing your cooling needs in summer are almost nil in NS not making it a very good fit for you. If you have the wood supply, I think you are on the right track. Maybe just plain old electric baseboard would get the job done for vacations, etc. The storage would help keep the fire tending to a minimum the rest of the time.