Solar Thermal Panel Performance

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Solar Thermal Panel Performance

Goals of Lab

  • Measure performance of panels in heating season.
  • Determine whether or not solar panels will sufficiently heat building throughout season; try to quantify and characterize deficit.
  • Optimize operation of panel system for heating season.

Decisions to be made from Lab

  • When to begin and end the heating season for system scheduling (tank changeover from heating to cooling and vice versa).
  • When to activate the solar panels for heating the tanks (daily basis).
  • When to activate the Altherma for tank heating.
  • How long should cloud delay be?

Expected Outcomes

  • Verify that panels are performing as expected.
  • Verify if panels will produce enough heat on a consistent basis to heat the building "x" amount of time. (CHECK CALCULATIONS TO SEE IF WE HAVE PARAMETERS)
  • Inform operation of Altherma.



  • Review control programming for solar thermal system and parameters that activate and deactivate system.
  • Observe and collect data on how parameters used for control trend over time and in various conditions.
  • Establish parameters to measure if adjustments made to system in future improve efficiency and/or operations.
  • Analyze collected data.
  • Propose adjustments to system to improve performance.
  • Observe and collect data to check improvement success.
  • Continue iterations until optimized.
  • Establish continuous commissioning parameters that may be monitored on a continuous basis to maintain optimal system performance.
  • Develop energy dashboard information.

Process Measurements

  • DDC Measurements used for actual control:
    • T1-A solar panel array core air temperature (located at top of one panel)
    • T2 tank temperature (located in lower part of tank 2)
    • T1-B solar panel array water temperature out (located on metal part of PEX tee fitting in Annex below roof)
  • DDC Measurements used for monitoring in addition to control parameters:
    • T1-C solar panel array water temperature in (located on metal part of PEX tee fitting in Annex below roof)
    • P-9 status on used for assumed water flow of 10 gpm (verified by circuit setter in solar panel return line)
  • Data Logger Measurements collected for analysis:
    • Solar array tank bypass line temperature (mounted on PEX line, so some time delay in registering temp changes expected) - check for errant bypassing of solar heated water through bypass
    • Tank temps at various locations (high and low in tank 1 and high in tank 2) - check magnitude of stratification to determine validity of using T-2 to control system adequately
    • Optimize system by checking start and stop of system to see if improvements can be made to setpoints.
  • Other measurements or observations:
    • Water flow test kit to read flow at circuit setter (confirm 10 gpm flow with P-2 on and P-2 off)
    • Solar Thermal Data Logger Plan - Media:2012 02 Solar Thermal Data Logger Location Plan.PNG
    • Thermal image of solar panels
      • Check after shutdown to verify complete drainage
      • Check during initial start-up to see what tube temperatures in panels reach when water introduced and how quickly temperature stabilizes with water flowing.
      • Check during established operation to get a sense of stratification of temperatures within panels top to bottom and within the array right to left due to distribution, location, and tilt of panels.

Resources Required

  • Training on how to set up temporary trend logs in DDC so we can do short term studies on different system parameters and components with different time increments on the trends, then put back to general terms when complete so system does not bog down - Cochrane
  • Data Loggers for trending points where no DDC sensors provided - LL Catey Engineering Services
  • Differential pressure manometer for water DP readings on circuit setters (verify water flow)
  • Water flow test kit - LL Catey


  • Labs Team
  • Joe


  • GG Services
  • Building Systems Commissioning

Help Wanted

  • Analysts
  • Track solar insolation

Scheduling & Sequencing

  • Unable to get control of trend logging until after first critical heating season over. Use data loggers for now.
  • Cold weather testing prior to January - March
  • Shoulder season testing March - April



  • Solar Panel Disable Checks - Why is comparison made between T-2 (tank temp)and T-1B (panel water out temp)? Why not T-1C and T-1B (panel in to panel out)? This seems like it would be a bit more direct as long as both sensors are reading accurately.
  • Depending on how often the panels cycle on and off during a day, what is the potential benefit vs. risk of improving air control of the system (adding air vent at high point and/or vacuum breaker)? Potential for freeze up and consequences if do freeze?


  • Plan / Do / Study / Act / Repeat

Interim Data and Analysis