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[EnergyPlus_Support] Re: solar collector to sky radiator
Ed Cox
As I remeber, accroding to a book, I hv forgotten the title, a sky
radiator is covered with a 'screen' or glazed to prevent covective
heat gain fromm the surrounding air.
I dunno the energyplus can stimulate to what extent.....
Anyway, thanks for your advice, I will check out the EP v3 .
Ian
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Edwin Cox <ebcox@...>
wrote:
>
> 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@...> wrote:
> From: Yuen Liu <yli006@...>
> Subject: RE: [EnergyPlus_Support] Re: solar collector to sky
radiator
> To: "Linda" <energyplus_support@xxxxxxxxxxxxxxx>
> Date: Friday, November 28, 2008, 6:11 PM
>
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> 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? °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
>
>
>
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>
> 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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> Turn email contacts into buddies, and you could win. Enter today.
>
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