I'm looking to get some ventilation and solar heating in my rather cold house in Karori. I already have gas central heating but I'd rather avoid using fossil fuels unless really necessary.
I quite like the idea of a box on the roof to capture solar heat and dump it into the house at the same time as providing ventilation. As far as I can tell there are two competing products .. solarventi from the DVS group, and solamate from the HRV crowd.
Using the neat calculator from http://mapserve3.nrel.gov/PVWatts_Viewer/index.html it seems the average maximum energy I can capture is 4.4kwh/m2/day. So, for the largest Solarventi panel which claims to be able to recirculate air for 140 m2, and dimensions of 300 cm x 100 cm, then that's 3 m2, so max I can expect at say 70% efficiency is 9.24 kWh in an average day or less than 4 hours of a 2kW heater running.
I expect that would take the chill off the air, and the drying out of the ambient air would reduce my heating costs.
Anyone have any experience with these units? And would there be any heat on a day like this which is completely overcast. Some solar radiation is clearly reaching the ground ... I asked the DVS guy who came round yesterday and he didn't think they had any installations of the SolarVenti yet in Wgton .. it being a new product.