[RE-wrenches] solar hot water nighttime recirc

[Darryl Thayer]

Yes it is done, there are controllers that do this.  For an effective design the system should be able to collect and store the day time energy with out getting to hot.  Perhaps a larger tank is required in most cases.  The nightime loss could be estimated by the length of time of heat dump multiplied by the temperature difference, and the loss coefficent Frul for the collector.  
Darryl  


--- On Thu, 12/17/09, Phil Undercuffler <solarphil at gmail.com> wrote:

> From: Phil Undercuffler <solarphil at gmail.com>
> Subject: Re: [RE-wrenches] solar hot water nighttime recirc
> To: nponzio at buildingenergyus.com, "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Date: Thursday, December 17, 2009, 12:20 AM
> Nighttime cooling is possible, it works,
> and there's some pretty good data being collected about
> it recently.  The actual amount of energy that you can
> radiate out depends on many factors, including ambient
> nighttime air temperatures, the dew point in your area, and
> the emissivity of your collectors.  I'd suggest you
> contact Boaz at Cedar Mountain Solar -- his team has been
> doing some pretty brilliant designs and research using this
> approach, both for collector cooling but more interestingly
> for cooling the living space.
> 
> Phil Undercuffler
> Conergy
> 
> 
> 
> 
> 
> 
> On Wed, Dec 16, 2009 at 8:53 PM,
> Nicholas Ponzio <nponzio at buildingenergyus.com>
> wrote:
> 
> Apologies if this has
> already been discussed here.
> 
> 
> 
> One heat diversion method I hear suggested often is
> recirculating
> through the collectors (flatplate) at night. Are there any
> data,
> calculations or anecdotal evidence on the effectiveness of
> this approach? That is, can I really radiate as much energy
> back to a dark sky as I collect during the day?
> 
> 
> 
> Thanks for any feedback.
> 
> 
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