Our Solar System
Over two weekends in November 2010 we installed an
hot water system on our house with the help of volunteers from
SEAREI and David Glover of Glover Plumbing.
We are using a
Resol BS differential temperature controller with a
Datalogger DL2 linking it to our home network, where some scripts
add the temperatures into a database and creates these graphs.
The graph below shows the temperatures through a 24 hour period. The red line is the solar
tube temperatures on the roof. The green line is the temperature in the bottom of the
hot water tank - dips in the green line are us using hot water in the house. When
the collector is hotter than the tank the hot glycol circulates, warming our
hot water and saving us money. The dark blue line is the top of the tank - when it's hotter
than light blue line (the boiler fired tank) the second pump comes on and we're
saving even more money :D
This is where the geekiness begins. This is the difference in the temperatures of
the collector and the water tank plotted against the pump speed.
The Resol controller adjusts the pump speed to maximize transfer of heat to the
This is the pump for the solar loop which runs from the roof top collector to the
solar tank heat exchanger.
When the solar tank is 10°F warmer than the boiler tank this pump circulates
the warming water.
Outside Temp: 31°F
Paying the Bills