Solar Hot Water Systems - PV vs delta T control [RE-wrenches]
Jeffrey Wolfe, Global Resources
global at sover.net
Thu May 9 19:16:41 PDT 2002
David,
After some practical field problems, we developed the following standard
for deciding when to install PV direct vs controller systems in cold
climates:
- when the SDHW is heating a tank with no other source, then we will power
with a PV direct (unless the piping run is too long)
- if there is any other heat source to the tank (which we do frequently,
since we use those dreaded Thermomax tubes on quite a few of our josb),
then we always put a controller in. We don't want to take fossil heated
water and cool it in the collectors, and more significantly, in the
connecting piping.
No matter what you do, you're going to get some losses in the winter due to
pipe runs and collector warmup. This is one of the factors in the evacuated
tube technologies superior performance in the winter.
Jeff
-----Original Message-----
From: David Blittersdorf [SMTP:davidb at nrgsystems.com]
Sent: Thursday, May 09, 2002 9:20 AM
To: RE-wrenches at topica.com
Subject: Solar Hot Water Systems - PV vs delta T control [RE-wrenches]
Question:
We are in Vermont which gets real cold in the winter and SHW systems are
antifreeze
loop types. I have a Heliodyne system with AC pumps and a differential
temperature
sensor controller. I am looking at the trade-offs of going to the PV
powered pump
system vs the delta T control. I like the temperature sensor system as it
will not turn on
the pump when the stored hot water is warmer than the collector
temperature. I have
noticed in the very cold winter months that the pumps cycle on and off to
make sure the
incoming collector water is at a higher temperature than the tank.
I can forsee a problem with the PV powered pump happly pumping cold water
into a hot
tank because the PV panel is very efficiently running the pump (cold temp.)
but the
collectors are not warm yet. I also notice that my PV panels shed snow
quicker than my
hot water collectors.
Any experience out there?
Thanks,
David Blittersdorf
NRG Systems, Inc.
110 Commerce Street
Hinesburg, VT 05461 USA
Tel: 802-482-2255
Fax: 802-482-2272
email: davidb at nrgsystems.com
Web:http://www.nrgsystems.com
- - - -
To send a message: RE-wrenches at topica.com
Archive of previous messages: http://www.topica.com/lists/RE-wrenches/
List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm
Check out participant bios: www.mrsharkey.com/wrenches/index.html
Hosted by Home Power magazine
Moderator: michael.welch at homepower.com
- - - -
To send a message: RE-wrenches at topica.com
Archive of previous messages: http://www.topica.com/lists/RE-wrenches/
List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm
Check out participant bios: www.mrsharkey.com/wrenches/index.html
Hosted by Home Power magazine
Moderator: michael.welch at homepower.com
==^================================================================
This email was sent to: michael.welch at homepower.com
EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9
Or send an email to: RE-wrenches-unsubscribe at topica.com
T O P I C A -- Register now to manage your mail!
http://www.topica.com/partner/tag02/register
==^================================================================
More information about the RE-wrenches
mailing list