Upgrading the Flow Sensor at Duke University

We went back out to visit our solar hot water system at Duke University this week. One of the major objectives of this trip was to swap out the original 2″ Btu meter with a 1.5″ Btu meter. This is because the larger meter was not as sensitive as the smaller one. The data that we were analyzing from the original meter was missing a lot of the low flow activity. After re-evaluating the new data using the smaller flow meter, our average daily volume increased by 36%!

We also moved the incoming cold water sensor 2′ back up the cold water line and placed it on a horizontal section of pipe. It turns out that when the sensor was on the vertical section of pipe closer to the tank it was affected by warm water thermo-siphoning back up the cold water line. We should get a more accurate reading of the incoming cold water temperature now.

Both of these parameters are critical when you are billing the user for energy. Similar upgrades are under way at several of the other locations where we are operating under a Solar Thermal Purchase Agreement, or STPA.

As always, we love to hear your feedback!
Dr. Ben