Cob: cob/ thermalMass

[Matthew HALL(SED)]

If you try to make a storage heater using cob with heated elements buried deep inside it the
expansion/contraction of the water-carrying vessel (steel pipe?) will crack and ultimately destroy
the cob. Fired clay pipes may solve this, eg recycled underground pipes if you can find them. 

How about a trombe storage heater? If you are not familiar with the trombe wall concept here goes...
Place a thick thermal mass wall (eg cob) a short distance behind plain glass and paint the surface
of the wall black. The direct sunlight will heat the black wall intensely, and the backscattered
infrared radiation emitted by the glass will also provide an intense heating effect of the earth
mass wall. 

Now
Perhaps you could incorporate a storage/water heater within a trombe wall concept, the effect of
thermal expansion would not be so severe and possibly not cause cracking if the heat had to travel
through the earth mass first to get to the water to heat it, see what i mean? I envisage a sealed
water container within the earth mass wall.
Comments?
Cheers
Matthew