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

Wed Jul 5 07:56:09 CDT 2006

 Agreed, Steven.  Solar systems of any kind, electric or thermal, still
collect energy on cloudy days, just not as much.  It is easy to read on
an electric solar panel, you still get a few amps out of them on a
cloudy day. 

-----Original Message-----
From: Steven Shepard [mailto:sbtdesigns at earthlink.net] 
Sent: Thursday, June 29, 2006 10:57 AM
To: Lawrence Lile; GREENBUILDING at listserv.repp.org
Subject: RE: [BULK] [Greenbuilding] Experience with Dawn Solar DHW
systems?
Importance: Low

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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