Zero Carbon?

Zero Carbon?  Before too many people get hot under the collar about this, let’s be clear what I mean by this.

The plan—and we won’t know for at least a year whether we’ve succeeded—is to build a house which is neutral in terms of the CO2 it emits.  The solar thermal panels  contribute to the heating of the domestic hot water (DHW) and of the house without emitting any carbon.  Of course CO2 was generated in their manufacture—and I’m not counting that.

The solar photovoltaic (PV) panels should generate at least as much electricity , measured in kilowatt– hours (kWhr) as the house uses over the course of a year.  Some will be used immediately, but the rest will be fed back into the mains supply—particularly during the summer—and if the calculations are correct, the amount of power drawn from the mains supply at night and during the winter will be equal to this or, better, less.  Essentially, the mains supply is being used as though it were a battery.  And yes, the PV panels needed quite a lot of energy in their manufacture.

The log burner burns logs (!) and emits the carbon that was stored in the wood while it was growing.  This is neutral as the wood cannot emit more carbon than is in it.

Some will point out that there’s a lot of concrete in the ground slab and that concrete is a very energy demanding product—cement requires much energy in its manufacture.  True.  Limecrete would have been better—but less satisfactory as a thermal mass, and more expensive.  I have to cut my coat according to my cloth.  The solid wall between dining room and bathroom is there for thermal mass reasons. It’s partly made of second hand bricks and it also incorporates some other old heavy blocks in the part that’s rendered.


2 Responses to Zero Carbon?

  1. Alexander says:

    I don’t think your explanation of why burning wood is carbon neutral is quite sufficient. Saying that it is neutral because the wood cannot emit more carbon than is in it is like saying burning coal is carbon neutral. Surely to be neutral you have to ensure that the growing wood is being replaced at the same rate as you are burning logs? I know that your wood comes from your garden, but do you not have to show that you are only burning wood which would otherwise have fallen off and rotted?
    A x

    • davidl says:

      I think it is generally accepted that burning wood counts as carbon neutral, whereas burning coal – which, in common with oil (and gas) – was once some form of wood millions of years ago does not. If we do accept that we can burn very very old wood – coal – then we have to be happy to return the earth to what we think it was in the carboniferous era. Much hotter, much more CO2 and much less O2.
      But I’ll accept that there’s some doubtful activities going on – grow wood, to turn it into wood dust, to turn it into wood pellets, to ship it to this country, to turn it back into wood dust, to blow it into power stations mixed with coal dust. I wonder about the energy involved in the processes and the “wood miles”.
      And yes, I should be planting trees to replace those I’m using – though I have to point out that the wood I’m using was, largely, planted and grown by me in the last 25 years or so. Whether I or some else planted it, or is planting it, it’s a short term balance!
      PS No gas connected to this house.

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