[Greenbuilding] flat plat collectors

[Joe Killian]

  MTD = Modified Trickle Down  -  After Thomason's early designs as in 
the Vermont customs building which were named Trickle Down.

Thomason's design trickled water down the troughs in metal roofing, with 
a glazing a few inches above.  Many thought condensing on the glazing 
would render the approach useless, but it turned out to work quite well, 
albeit with temperatures lower than we are accustomed to in flat plate 
collectors.  The lower temperatures contribute to increasing the 
collecting efficiency.

There have been several designs under the MTD label, all of which 
capture the water between two sheets, both of which are usually behind 
glazing.  The object being to eliminate the issue of condensing water on 
your glazing surface and the accompanying losses.  I believe all these 
approaches have used some material between the two sheets to help 
distribute the water flow to better collect the heat - as Gary's piece 
in Build It Solar amply shows is needed.

These sheets are usually (always?) plastic, not much of a heat 
conductor.  But it's thin, with water immediately on the back side, so 
we're conducting heat through a few mils of plastic, not along several 
inches of the material as in copper fins in a flat plat collector.

Joe

On 10/11/2011 2:57 PM, Clarke Olsen wrote:
> What does MTD stand for? I would think that the absorber plate should not be a conductor, but a material keeping it's heat on the surface.
> Clarke Olsen
>
>
>
>
>
> On Oct 11, 2011, at 4:24 PM, Gary BIs wrote:
>
>> The MTD collector uses black polyester felt to spread the water across the full surface of a metal backing plate.
>> I've wondered about the life of the felt, but some of the MTD collectors are about 5 years old and the owners report they are doing well so far.
>>
>> Gary
>>
>> On 12:59 PM, Corwyn wrote:
>>> On 10/11/2011 10:56 AM, Gary BIs wrote:
>>>> Hi Joe,
>>>> Yes -- I'm eager to see how the traditional flat plate compares to the
>>>> MTD -- I think that the the MTD might do fine.
>>>>
>>>> I'm probably a bit prejudiced on this, but I think from a life and long
>>>> term maintenance point of view, the traditional flat plate may have some
>>>> advantages. I'm just a little concerned about keeping the trickle tube
>>>> trickling over 20 years.
>>> I suspect that a _mostly_ wet cotton towel would not have a very long lifespan.  And when it dies, it could well take the pump with it.
>>>
>>> Thank You Kindly,
>>>
>>> Corwyn
>>>
>>
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