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RE: [EnergyPlus_Support] Re: solar collector to sky radiator



I haven't looked at the model in detail, but I suspect that the solar collectors in Energy Plus are glazed. If so, they would not be able to take efficient advantage of radiation into the atmosphere as a mechanism of heat disposition for nighttime cooling.

The solution would be creation of a solar collector model for Energy Plus that is based on an unglazed collector. This could be an example of PV-thermal - a PV panel which has been fitted with heat transfer plates and tubing to collect heat during the daytime. See http://www.pv-t.org for examples. Danny Parker at Florida Solar Energy Center developed a very interesting schema of nighttime heating using a "Cool Roof" concept. He showed that one could expect cooling of approximately 75 W/m2 in typical conditions in many locations in the U.S. This is not a huge amount, not nearly as much as the amount of heat available during the day, but could be significant with sufficient area, especially if it is "free".

Ed Cox

--- On Fri, 11/28/08, Yuen Liu <yli006@xxxxxxxxxxx> wrote:
From: Yuen Liu <yli006@xxxxxxxxxxx>
Subject: RE: [EnergyPlus_Support] Re: solar collector to sky radiator
To: "Linda" <energyplus_support@xxxxxxxxxxxxxxx>
Date: Friday, November 28, 2008, 6:11 PM

Hi, Ian
 
If you have already run the simulatin as is, you may have noticed that the capacity of the panels is about 6 kW for heating.  The night time heat loss was a small fraction of this number.  I may be wrong in reading the result. as  I have just installed  the Version 3.0, and some of the variables have different names.
 
If you are still interested in knowing what is wrong with your IDF file, I suggest that you up-load the IDF file to this group.  Some one may have a look at it.
 
I have students working on solar panels at the University of Malaya, Kuala Lumpur, years ago (1960's).  The panel temperature was not very low at night.  The panel temperature follows the outdoor temperature and lower by about 3 to 5 °C.  The day time panel temperature can reach about 80°C.  
 

Regards,
Dr. Li.



To: EnergyPlus_Support@ yahoogroups. com
From: ian8512@yahoo. com.hk
Date: Fri, 28 Nov 2008 19:39:57 +0000
Subject: [EnergyPlus_ Support] Re: solar collector to sky radiator


Dr. Li,

Thanks you for helpful advice on the simulation of sky radiator!
As i am trying to investigate the feasibilty of using sky radiator,
therefore, the idea of flat plated being buried underground doesn't
work for me. But anyway, thanks for your reply, it has inspriated me.

Best Regards
Ian

--- In EnergyPlus_Support@ yahoogroups. com, Yuen Liu <yli006@...>
wrote:
>
>
> In a situalation you described, I usually change the equipment
availability schedule and leave all the equipment as is.
>
> For example, if you set the 'heater on' temperature below the night
temperature, it will not come on. I assume that the water usage can
also be shut off during the day.
> Do the changes one at a time and study the result.
>
> You also need to make sure that the DesignDay temperature will give
you the cold period between 9 am and 6 am.
>
> I have not looked at the actual example file, you may have problem
turning off the circulation between the plate and the tank during the
day. However, this problem will still be there, even if you remove
the heater completely.
>
> Your condition seems to be that when the outdoor temperature is
higher then the 16°C the circulation is cut off. The original
condition is for the sun to heat the panel to above a certian
temperature and then circulate. This is the part I think is causing
the problem.
>
> If you are thinking of using this system to collect free cold
water, it may work using the ground temperature which does not
change very much, and can be left connected the whole day, with the
flat panel buried below ground.
>
> Regards,
> Dr. Li
>
>
>
> To: EnergyPlus_Support@ ...: ian8512@...: Fri, 28 Nov 2008 10:55:34
+0000Subject: [EnergyPlus_ Support] solar collector to sky radiator
>
>
>
> I am going to stimulate a sky radiator using an existing example in
energy plus - solar collector.In the solar collector, there are 4
components, they are the flat plate, storage tank, heater and water
use connections objects.I am trying to change it to 2 components,
falte plate and a storage tank. And the operation time will be at
night(21:00 to 6:00)and the set point temperature of the storage tank
will be around 20 deg. celeus to 16 deg. celeus.However, everytime,
there are so many errors after I attempted to change those parameter
and setting.Could somebody lend a helping hand??
>
>
>
>
>
> ____________ _________ _________ _________ _________ _________ _
>




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