Dennis Heidner
  • Kirkland, WA
  • United States
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Latest Activity

Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"Photocatalytic materials often have titanium oxide or other substances in them as part of the trigger to break down materials when hit with the UV in the sunlight.  Adding to paint - is generally an ineffective ensure the proper application of…"
Jan 2
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"Radiant barriers - especially paints and foils... have been tested many times by various labs and shown to be less than cost effective.  Then simply good old fashion insulation and air sealing. As for new special radiant materials.... indeed…"
Jan 2
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"I had noted, and show with graphs that there was some cooling because of the shading of panels.  But it was small compared to the reduction as a result of insulation - more insulation and not just code minimum. The original posters was from the…"
Jan 2
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"Generally when PV modules are added to a roof, the installers are supposed to ensure that AT LEAST fifteen years remain on the roofs life span (more likely they'd look for 20 years). It would be difficult to do an adequate job that a roofer…"
Jan 1
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"PV modules are going to be in full sunlight (if possible),  worrying about the heat on panels is secondary to the good sunlight and secure mounting on the roof.   The original post is now nearly three years ago, at the time he was…"
Jan 1
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"The radiation "effectiveness" doesn't change with temp... its the heat flow that changes with the delta-T.    Q = U x A x T   where Q is the heat flow (either direction), U=1/R with R being the insulation R value…"
Dec 28, 2018
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"ALL building materials are thermal bridges which allow for the flow of heat in either direction.  Concrete foundations will act as a thermal bridge and provide a good path for heat loss (or gain) unless the interior floor and space is isolated…"
Dec 28, 2018
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"Correct,  but drywall is a essentially a thermal bridge... with lots of surface area.  You can model it easily with Therm.  I believe they have a dry wall material layer already including in Therm.  I did not want to put thermal…"
Dec 28, 2018
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"After re-reading this I realized that I forgot to explain that in colder temps the voltage across each PV cell increases by about 0.1 Volt (roughly),  in most common roof top applications the module will have 60 cells,  so the cold temps…"
Dec 26, 2018
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"These are notes for my reply down below on the thread.  Better description of the temps in the attic under solar panels. The house faces SSW,  with the long axis east/west.  About 25 degrees off due south.  The panels are on the…"
Dec 26, 2018
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"The house faces SSW,  with the long axis east/west.  About 25 degrees off due south.  The panels are on the south side of the roof. This roof is a LOW pitch torch down!  E.g.  roof membrane has good contact with the plywood…"
Dec 26, 2018
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"Dannie said: " As the temperature of the solar panel increases, its output current increases exponentially,"  No.   As the temperature of the panel increases there is a tendency for increase recombination (leakage) of…"
Dec 20, 2018
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"PV modules are "current" devices.  The temperature doesn't alter the resistance,  instead it increases the recombination of electrons with the "holes" reducing the electric current that is able to flow out of the…"
Dec 18, 2018
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"Here come the batches of charts.  The data was collected almost nine years ago..  I've included a weather capture (roof top weather station),  chart from sensors in the attic,  and a chart that shows the temperature and…"
Dec 18, 2018
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"Here come the batches of charts.  The data was collected almost nine years ago..  I've included a weather capture (roof top weather station),  chart from sensors in the attic,  and a chart that shows the temperature and…"
Dec 18, 2018
Dennis Heidner replied to Tim Kendzia's discussion Cooling effect from solar panels
"Here come the batches of charts.  The data was collected almost nine years ago..  I've included a weather capture (roof top weather station),  chart from sensors in the attic,  and a chart that shows the temperature and…"
Dec 18, 2018

Profile Information

Company
Rextorgroup
Professional Interests
Energy efficiency, building envelop, renewables, building modeling

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At 3:25pm on March 21, 2013, Diane Chojnowski said…

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