After finishing the final plumbing of our solar thermal array, we have been anxious to get some sunny days to observe how well the panels will heat our 500 gallon storage tank.  So far, we have only been available to measure temperatures throughout the day on some partly cloudy days and we have seen the 500 gallons of water increase by around 50-60 degrees.  So we are pleased, although data logging in the near future will give us definitive answers as to how the system is performing.  We were concerned that our Taco 008 pump may not be large enough to transfer the heat fast enough from the large solar thermal system.  After a couple of these moderately sunny days, we have observed that the pump is doing its job and no temperatures have reached the point of stagnation where pressure relief valves have blown.  It is yet to be determined if this will continue to be the case as hotter and sunnier spring days come our way.  The large size of the system was engineered to get us through the cold winter months and the steep 65 degree angle at which the panels were mounted was for the optimization of collecting winter sun.  We will soon be without the need for our winter greenhouse solar thermal heat source, as the days are becoming warmer and warmer as spring approaches.  With that being said, before too long we will be installing shade cloth over the panels to prevent overheating and of course the cloth will be removed in the fall when temperatures start to get colder.  We do, however, use the solar thermal heated water for domestic water use and for heating vegetable oil in the biodiesel production process year round.  So the shade cloth should slow the absorption of heat into the panels to a rate at which our year-round heating needs for other processes will still be met.  We will be logging data over the next few days and producing graphs that we will post in upcoming weeks.  Keep checking in and soon you will be able to see our graphed data that will reveal irradiance, ambient temps., and  the resulting rises of temperatures in our solar thermal water storage tank.