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RE: [EnergyPlus_Support] problems with the example file "SolarCollectorFlatPlateWater.idf"?
The problem with the "SolarCollectorFlatPlateWater.idf" example is that the gas burner capacity is vastly undersized. If you look at the "Water Heater Tank Temperature" variable, you'll see that it nevers reaches the setpoint temperature of 60 C (140 F), even though the burner is fully on. The burner was intentionally undersized to check the behavior of the tank temperature as it changes with domestic hot water (DHW) demand and solar collector supply. If the burner is large enough to quickly heat the tank back up after a significant demand, then the solar collectors never really have a chance to do anything. For instance, consider the scenario where there is a big DHW demand (several hot, hot showers) early in the morning before the sun comes up. If the burner is "normal" capacity, I would think that the burner would completely heat the tank back to its set point within an hour or two at most. This is still before the solar collectors have really started providing any h
eating. So it would be very hard to see their effect.
I've uploaded a new example file to EnergyPlus_Support called "SolarCollectorFlatPlateWater2.idf". This example modifies the previous example to show something more like what you are expecting. There is a single big DHW demand in the morning, but now I've used the optional "Nominal Capacity Operating Schedule" field of the WATER HEATER:SIMPLE to shut off the gas burner during the day. So if you look at the "Water Heater Tank Temperature" variable, you'll see a big drop in the morning followed by heating due to the solar collectors until the evening when the gas burner comes on to make up any remaining temperature difference to reach the setpoint. The summer design day actually only needs the gas burner to offset the skin losses from the tank. The winter design day needs a little more help from the gas burner. Look at the REPORT VARIABLEs for "Water Heater Burner Heating Energy" and "Water Heater Heat Recovery Supply Energy" to see the energy contributions from gas burne
r and solar collectors, respectively.
Peter G. Ellis
National Renewable Energy Laboratory
Center for Buildings and Thermal Systems
1617 Cole Blvd
Golden, CO 80401
-----Original Message-----
From: iaccabr [mailto:iaccabr@xxxxxxxxx]
Sent: Thursday, December 09, 2004 7:57 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] problems with the example file "SolarCollectorFlatPlateWater.idf"?
Dear all,
I think maybe there are some problems with the example
file "SolarCollectorFlatPlateWater.idf", because when i finished the
hour-by-hour simulation,I checked the Meter file,all the 'DHW:Gas [J]
(Daily)' are equal,as we all know, the solar radiation is much
different from every day, the gas consumption should also be
different,why?
Is there anyone can answer my question?
thinks
Hoozor
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