When a typical boiler is running in hydronic systems, the water returning from space
heaters (AHU, unit heaters, baseboard elements, radiators or others) may be
warmer than the water in the solar storage tank. For this reason, the solar tank and
the auxiliary boiler are installed in parallel.
The solar tank is given the first chance to meet the heating load. If it cannot
maintain the desired temperature, the water flow is diverted through the auxiliary
boiler. Solar energy is not used for preheating, and the two systems perform
independently (Figure 2-7).
Again, a two stage thermostat is used, but stage one is cut off whenever stage two
comes on (Figure 2-7).
A Hydronic Heating
Solar heat is used for space cooling with, absorption chillers. These chillers use
heat energy to drive the refrigeration cycle, rather than electrical or mechanical
energy. These systems require fairly high temperatures (160F-200F), so they use
either very efficient flat-plate or evacuated tube collectors.
In a solar cooling system, the solar tank and the auxiliary boiler are installed in
parallel. This is because when the auxiliary boiler is operating, the water returning
from the generator is almost always warmer than the water in the solar storage tank.
2.1 BASIC SYSTEM CONFIGURATION