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Solar Collector outputs -100C water in San Diego

I am modeling a SolarCollector:FlatPlate:Water and the temperatures don't seem quite right. Here is a day from the output variables.

image description

I am using some EMS to control the pump for the solar collectors. When the incident solar radiation on the panel is greater than 0, then the pump turns on. I figured that turning the pump on with any amount of sunlight on it would be a good place to start for making sure only heated water went into the storage tank. The temperatures look a little off though. The water coming into the solar panel is the temperature of the storage tank, which makes sense. The water coming out of the panels when sunlight is 200C most of the time, which is also reasonable since I think my flow is low. The temperature at the outlet of the solar panels when the pump is off is also reasonable.

The one that gets me is when the -100C that occurs for more than an hour (I checked with the Output:Variable reporting every timestep) when the pump is on and there is considerable sunlight on the panel.

The only other thing unusual about my model is I combined all the solar panels together since simulating one giant panels is much faster than simulating many regular sized panels.

image description

Here is a google drive link to my files.

I would really like to be able to consolidate the panels like I have, but the -100C is a deal breaker. Am I stretching the model too far by having a very large solar thermal collector, or is there a way I can fix it?

Solar Collector outputs -100C water in San Diego

I am modeling a SolarCollector:FlatPlate:Water and the temperatures don't seem quite right. Here is a day from the output variables.

image description

I am using some EMS to control the pump for the solar collectors. When the incident solar radiation on the panel is greater than 0, then the pump turns on. I figured that turning the pump on with any amount of sunlight on it would be a good place to start for making sure only heated water went into the storage tank. The temperatures look a little off though. The water coming into the solar panel is the temperature of the storage tank, which makes sense. The water coming out of the panels when sunlight is 200C most of the time, which is also reasonable since I think my flow is low. The temperature at the outlet of the solar panels when the pump is off is also reasonable.

The one that gets me is when the -100C that occurs for more than an hour (I checked with the Output:Variable reporting every timestep) when the pump is on and there is considerable sunlight on the panel.

The only other thing unusual about my model is I combined all the solar panels together since simulating one giant panels is much faster than simulating many regular sized panels.

image description

Here is a google drive link to my files.

I would really like to be able to consolidate the panels like I have, but the -100C is a deal breaker. Am I stretching the model too far by having a very large solar thermal collector, or is there a way I can fix it?

POST SCRIPT
I started looking more closely at the SolarCollectorFlatPlateWater.idf example file and the Engineering Reference for the Solar Thermal panels. The equation is linear with the outdoor air temperature and the incident solar radiation.

image description

Then I found these three rows in the output of the example file output variables.

image description

I tried to find rows with similar differentials between inlet water temp and outlet water temp, as well as incident solar radiation. Taken altogether, the relationship doesn't look linear, especially the last two rows, which have a 2C versus 8C jump in the water temperature for approximately the same outdoor temperature, water inlet temperature, and incident solar radiation.

Solar Collector outputs -100C water in San Diego

I am modeling a SolarCollector:FlatPlate:Water and the temperatures don't seem quite right. Here is a day from the output variables.

image description

I am using some EMS to control the pump for the solar collectors. When the incident solar radiation on the panel is greater than 0, then the pump turns on. I figured that turning the pump on with any amount of sunlight on it would be a good place to start for making sure only heated water went into the storage tank. The temperatures look a little off though. The water coming into the solar panel is the temperature of the storage tank, which makes sense. The water coming out of the panels when sunlight is 200C most of the time, which is also reasonable since I think my flow is low. The temperature at the outlet of the solar panels when the pump is off is also reasonable.

The one that gets me is when the -100C that occurs for more than an hour (I checked with the Output:Variable reporting every timestep) when the pump is on and there is considerable sunlight on the panel.

The only other thing unusual about my model is I combined all the solar panels together since simulating one giant panels is much faster than simulating many regular sized panels.

image description

Here is a google drive link to my files.

I would really like to be able to consolidate the panels like I have, but the -100C is a deal breaker. Am I stretching the model too far by having a very large solar thermal collector, or is there a way I can fix it?

POST SCRIPT
I started looking more closely at the SolarCollectorFlatPlateWater.idf example file and the Engineering Reference for the Solar Thermal panels. The equation is linear with the outdoor air temperature and the incident solar radiation.

image description

Then I found these three rows in the output of the example file output variables.

image description

I tried to find rows with similar differentials between inlet water temp and outlet water temp, as well as incident solar radiation. Taken altogether, the relationship doesn't look linear, especially the last two rows, which have a 2C versus 8C jump in the water temperature for approximately the same outdoor temperature, water inlet temperature, and incident solar radiation.