Hi,
Further thoughts... Thanks again for your data point.
My plans are a mixture of theory (what might be possible in order to go zero or negative carbon), and more practical (what I might do at my current tiny house or if we move to somewhere close by larger).
Your 67% figure is quite interesting, ie 2/3rd of year-round DHW and CH from solar thermal, with the balance from another fuel source.
If I aimed for that with solar thermal with protection from overheating, then I could in principle (though expensively) make up some of the gap with solar PV and a plain ground-source heat-pump and/or a more moderate thermal store than I was planning before (eg 20kl rather than 60kl). A good CoP on the heat-pump might compensate for much of the relative inefficiency of PV compared to thermal for energy capture.
And the big potential advantage of solar PV is that I can safely just not use any excess, eg in summer, or even export it to the grid. Overheat is not an issue.
I'm trying to work through making some of these ideas a bit more practical on this page:
http://www.earth.org.uk/towards-a-LZC-home.html
though please bear with me since I'm still mid-thought, so maybe check by later today.
Rgds
Damon