[Greenbuilding] [BULK] Experience with Dawn Solar DHW systems?

Fri Jun 30 17:45:12 CDT 2006

good for you steve, i agree both as an engineer and a 30 year user of solar 
thermal. for some real time data try http://www.infomonitors.com/swinter/

i'd venture to guess that 1/3 of the annual output comes from "cloudy days" 
solar dhw works and is cost effective thruout the us.  try www.findsolar.com 
for a persoanlized estimate.

----- Original Message ----- 
From: "Steven Shepard" <sbtdesigns at earthlink.net>
To: "Lawrence Lile" <LLile at projsolco.com>; <GREENBUILDING at listserv.repp.org>
Sent: Thursday, June 29, 2006 12:56 PM
Subject: RE: [BULK] [Greenbuilding] Experience with Dawn Solar DHW systems?

> Lawrence,
>
> I feel like I need to bring something to yours and the groups attention. 
> Solar hot water heating systems (more specifically solar thermal heating 
> systems) produce heat in two ways.  If and when the proper solar thermal 
> collector is used these devices produce heat by harvesting heat energy 
> from sunlight and from a "greenhouse effect" inside the thermal collector. 
> In that regard, it is possible to create solar heated water even on cloudy 
> days.  And I do mean water temperatures in excess of 120 degrees F.  It is 
> inaccurate to suggest that solar water heating is only a good and viable 
> idea in sunny climates.
>
> Now please don't bother asking me to produce reams of data to substantiate 
> this claim.  I am sharing with you the benefit of my 14 years of 
> experience in the solar industry and my personal experience as a solar 
> user.  If you require such data feel free to contact Sandia Labs in New 
> Mexico.  They have been conducting such research on solar for the last 30 
> years at the taxpayer's expense.  Besides, as a vendor supplying data is 
> not my role and I find that Americans make that request when they are 
> searching for an excuse to not do the right thing.
>
> Steve
>
>
> -----Original Message-----
>>From: Lawrence Lile <LLile at projsolco.com>
>>Sent: Jun 26, 2006 3:04 PM
>>To: GREENBUILDING at listserv.repp.org
>>Subject: RE: [BULK]  [Greenbuilding] Experience with Dawn Solar DHW 
>>systems?
>>
>>I would suspect that your coldest days might coincide with your
>>cloudiest days.  This isn't always true, but I'd be very leery of
>>depending on solar electric to produce heating energy.  Unlike cooling,
>>which is likely to be heaviest when the sun is shining.  You also suffer
>>an efficiency penalty with solar electric versus other methods of
>>harvesting the sun.
>>
>>After conservation (insulation and caulking), passive or active solar is
>>your best bet here.  If you already have radiant floor, then you are a
>>prime candidate for an active solar hot water system to tie into your
>>floor.  Using the huge mass in your concrete to store heat for cloudy
>>days makes sense.  If you make sure the edges are insulated down below
>>frost line, then you are also using the mass of the earth below the
>>radiant floor to store more heat.
>>
>>Solar hot water is also a good bet, if you live in an area with enough
>>sunny days.
>>
>>Unfortunately, you'll probably want some form of central heat if you
>>live in any normal building with plumbing inside.  With a lot of
>>collector area, you may not need it but a few times a year, but when
>>your pipes are about to freeze you'll be glad you had it.  It will work
>>the same with hot water, solar hot water heaters work best in the
>>summer, in northern winters you'll often not have enough sun.
>>
>>You can always use wood heat backup, that might help you sever the
>>petro-fuel umbilical.
>>
>>Is Propane available in your area?  I wonder if it is a less polluting
>>alternative to oil heaters?
>>
>>--Lawrence Lile
>>
>>
>>
>>
>>
>>
>>-----Original Message-----
>>From: greenbuilding-bounces at listserv.repp.org
>>[mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of Irina
>>Golfman
>>Sent: Sunday, June 25, 2006 11:12 AM
>>To: Greenbuilder list
>>Subject: [BULK] [Greenbuilding] Experience with Dawn Solar DHW systems?
>>Importance: Low
>>
>>Good afternoon,
>>
>>We are evaluating various solar technologies for our remodeling project
>>in Massachusetts. We have about 550 sq feet of South West facing roof at
>>about a 35 degree angle with a small amount of shade in the summer. In
>>my research I've stumbled on the company called Dawn Solar
>>(http://www.dawnsolar.com/) which uses radiant tubes placed under a
>>metal rood to collect the solar gain for DHW pre-heat. They also partner
>>with UniSolar that manufactures PV panels that can fit between the
>>ridges of the metal roof and contain 32(?) independent arrays, so that
>>the panel can still function even if a small part of it is shaded.
>>
>>I wondered if anyone on the list have any experience with Dawn Solar?
>>How does their efficiency and reliability compare to using Solar Panels
>>to heat the water? I know that Unisolar panels are not as efficient as
>>other solar panels at generating electricity. Does anyone have hard
>>numbers on this?
>>
>>As a follow up question I would love to hear people comments on the
>>viability of not having a conventional oil or propane boiler to heat a
>>house in the NE. We have to install a new heating system (combination of
>>radiant and forced hot water radiators and base board). Because of our
>>topology (the house is on a hill and the oil tank is at the bottom of
>>the
>>hill) we need to invest a serious amount of money to replace the aging
>>oil line. The thought of investing all this money to heat my house with
>>oil really troubles me. We'd be facing the same piping issues with
>>propane and natural gas.
>>
>>I've toyed with the idea of on-demand electric heaters to supplement
>>what we can get off the roof, augmented with a pellet stove in the
>>kitchen/living room area, but I've been told that this is not a
>>realistic option for this area where winters can be quite cold. Any
>>comments on this will be much appreciated.
>>
>>Thank you very much for the help,
>>-------------------------------------------------
>>Irina
>>
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>
>
> SBT Designs
> 25581 IH-10 West
> San Antonio, Texas 78257
> (210) 698-7109
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