Posted by Jake on October 12, 2007, 8:10 am
I live in a house that is primarily heated by passive solar with wood stove
for back up. I am also off the grid with Photovoltaic for electricity.
Three areas of the house do not get much passive solar. Two rooms in the
back of the house and the basement.
I have four 4x8 foot thermal pannels, which I would like to use to heat
these areas. I do not plan to store heat, and would like to pump glycol
from the panels directly through radiators using a DC motor powered
directly from a photovoltaic panel or panels. The total distance for the
glycol loop would be fairly great, about 100 feet or so. I would like to
use fairly small radiators with small electric fans to distribute the heat.
I live in an area that has lots of Sun in the Winter (South Park Colorado).
Often we have to deal with fairly cold temperatures here, minus 20 Celcius.
First I am looking for a good source of information on such a system,
books, Web Sites, etc.
Second some specific questions are:
1) Need a formula for calculating the power for the punp motor and ideas on
how to handle startup current.
2) Do I need an expansion tank and if so how big or how do I calculate the
size?
3) Since the pump would stop when Sun isn't available would residual heat
be a problem?
4) Are there any systems that cover the panels automatically when the
panels get too hot, or perhaps during low Sun Conditions when there is
insuffecient Photo Voltaic to power the pump?
Any advice or suggestions that you may have will be appreciated..
JakeInHartsel
Posted by Jake on October 18, 2007, 8:55 am
On Fri, 12 Oct 2007 18:57:11 -0500, David Williams wrote:
> -> I have four 4x8 foot thermal pannels, which I would like to use to heat
> -> these areas. I do not plan to store heat, and would like to pump glycol
> -> from the panels directly through radiators using a DC motor powered
> -> directly from a photovoltaic panel or panels. The total distance for the
> -> glycol loop would be fairly great, about 100 feet or so. I would like to
> -> use fairly small radiators with small electric fans to distribute the heat.
> -> I live in an area that has lots of Sun in the Winter (South Park Colorado).
> -> Often we have to deal with fairly cold temperatures here, minus 20
> Celcius.
>
> Are you sure you want to use glycol? It gets fairly viscous at low
> temperatures, which makes it more difficult to pump around.
>
> Have you thought about a solution of calcium chloride? The freezing
> point can easily be depressed below -20C, and the viscosity stays low.
>
> dow
I am open to anything that will work. Is corrosion a problem with calcium
cloride? What types of pipes could be used with it? We do get some pretty
cold temeratures up where I live, -30 C. is not uncommon.
Jake
Posted by gary on October 19, 2007, 10:33 am
> I live in a house that is primarily heated by passive solar with wood stove
> for back up. I am also off the grid with Photovoltaic for electricity.
> Three areas of the house do not get much passive solar. Two rooms in the
> back of the house and the basement.
> I have four 4x8 foot thermal pannels, which I would like to use to heat
> these areas. I do not plan to store heat, and would like to pump glycol
> from the panels directly through radiators using a DC motor powered
> directly from a photovoltaic panel or panels. The total distance for the
> glycol loop would be fairly great, about 100 feet or so. I would like to
> use fairly small radiators with small electric fans to distribute the heat.
> I live in an area that has lots of Sun in the Winter (South Park Colorado).
> Often we have to deal with fairly cold temperatures here, minus 20 Celcius.
> First I am looking for a good source of information on such a system,
> books, Web Sites, etc.
see links below
> Second some specific questions are:
> 1) Need a formula for calculating the power for the punp motor and ideas on
> how to handle startup current.
The best way to do this is to find out what the collector manufacturer
wants for flow rate through the panels. If you can't find this, you
might use something like 0.05 gpm per sqft of panel or a bit less.
Once you know the flow rate, you need to calculate the pressure drop.
This means adding up the pressure drop through the 100 ft of piping,
collectors (usually not to large) and radiators.
Having flow rate and prssure drop in hand you can select a pump using
the head vs flow curve for the pump.
March and Ivan Technology (ElSid) are popular pumps for what you want
to do (see link below). Most of the places that sell these tell you
how large a PV panel is needed to drive each pump model.
If this seems like more than you want to get into, I'd just estimate
the flow rate needed, and call one of the pump suppliers with the flow
rate and a description of your system and see what they recommend. It
not important to get it perfect.
> 2) Do I need an expansion tank and if so how big or how do I calculate the
> size?
Yes -- see links to basics articles below for some good plumbing
diagrams.
> 3) Since the pump would stop when Sun isn't available would residual heat
> be a problem?
I don't think so. If there is not enough sun to run the pump there is
probably not enough to overheat the collectors.
> 4) Are there any systems that cover the panels automatically when the
> panels get too hot, or perhaps during low Sun Conditions when there is
> insuffecient Photo Voltaic to power the pump?
I have seen such a system, but I don't believe they are common.
I would worry more about the situation where either there is a failure
in the pumping system, or its so hot inside that you shut down the
pump to prevent overheating the interior of your house.
If you could mount the panels vertically, this works out quite well
for winter space heating. Vertical panels collect a lot of heat in
the winter with a low sun, but much less in the summer with the high
sun. If there is a snow field in front of the collectors, vertical
panels get a good boost from reflection off the snow.
Some links from my site that might be helpful:
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm
(see the HP basics articles -- very good)
http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm
(see the basics and the active heating areas)
http://www.builditsolar.com/References/supplierrefs.htm
(this is a list of potential suppliers of pumps, controllers, ... --
no idea how good they are)
Gary
> Any advice or suggestions that you may have will be appreciated..
> JakeInHartsel
Posted by Jake on October 20, 2007, 9:21 am
On Fri, 19 Oct 2007 07:33:08 -0700, gary@builditsolar.com wrote:
>> I live in a house that is primarily heated by passive solar with wood stove
>> for back up. I am also off the grid with Photovoltaic for electricity.
>>
>> Three areas of the house do not get much passive solar. Two rooms in the
>> back of the house and the basement.
>>
>> I have four 4x8 foot thermal pannels, which I would like to use to heat
>> these areas. I do not plan to store heat, and would like to pump glycol
>> from the panels directly through radiators using a DC motor powered
>> directly from a photovoltaic panel or panels. The total distance for the
>> glycol loop would be fairly great, about 100 feet or so. I would like to
>> use fairly small radiators with small electric fans to distribute the heat.
>> I live in an area that has lots of Sun in the Winter (South Park Colorado).
>> Often we have to deal with fairly cold temperatures here, minus 20 Celcius.
>>
>> First I am looking for a good source of information on such a system,
>> books, Web Sites, etc.
>
> see links below
>
>>
>> Second some specific questions are:
>>
>> 1) Need a formula for calculating the power for the punp motor and ideas on
>> how to handle startup current.
>
> The best way to do this is to find out what the collector manufacturer
> wants for flow rate through the panels. If you can't find this, you
> might use something like 0.05 gpm per sqft of panel or a bit less.
> Once you know the flow rate, you need to calculate the pressure drop.
> This means adding up the pressure drop through the 100 ft of piping,
> collectors (usually not to large) and radiators.
> Having flow rate and prssure drop in hand you can select a pump using
> the head vs flow curve for the pump.
> March and Ivan Technology (ElSid) are popular pumps for what you want
> to do (see link below). Most of the places that sell these tell you
> how large a PV panel is needed to drive each pump model.
>
> If this seems like more than you want to get into, I'd just estimate
> the flow rate needed, and call one of the pump suppliers with the flow
> rate and a description of your system and see what they recommend. It
> not important to get it perfect.
>
>>
>> 2) Do I need an expansion tank and if so how big or how do I calculate the
>> size?
> Yes -- see links to basics articles below for some good plumbing
> diagrams.
>
>>
>> 3) Since the pump would stop when Sun isn't available would residual heat
>> be a problem?
> I don't think so. If there is not enough sun to run the pump there is
> probably not enough to overheat the collectors.
>>
>> 4) Are there any systems that cover the panels automatically when the
>> panels get too hot, or perhaps during low Sun Conditions when there is
>> insuffecient Photo Voltaic to power the pump?
>
> I have seen such a system, but I don't believe they are common.
> I would worry more about the situation where either there is a failure
> in the pumping system, or its so hot inside that you shut down the
> pump to prevent overheating the interior of your house.
>
> If you could mount the panels vertically, this works out quite well
> for winter space heating. Vertical panels collect a lot of heat in
> the winter with a low sun, but much less in the summer with the high
> sun. If there is a snow field in front of the collectors, vertical
> panels get a good boost from reflection off the snow.
>
> Some links from my site that might be helpful:
> http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm
> (see the HP basics articles -- very good)
>
> http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm
> (see the basics and the active heating areas)
>
> http://www.builditsolar.com/References/supplierrefs.htm
> (this is a list of potential suppliers of pumps, controllers, ... --
> no idea how good they are)
>
> Gary
>
>
>
>
>
>
>
>
>>
>> Any advice or suggestions that you may have will be appreciated..
>>
>> JakeInHartsel
Thank you Gary, you have been a great help.
JakeInHartsel
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> -> these areas. I do not plan to store heat, and would like to pump glycol
> -> from the panels directly through radiators using a DC motor powered
> -> directly from a photovoltaic panel or panels. The total distance for the
> -> glycol loop would be fairly great, about 100 feet or so. I would like to
> -> use fairly small radiators with small electric fans to distribute the heat.
> -> I live in an area that has lots of Sun in the Winter (South Park Colorado).
> -> Often we have to deal with fairly cold temperatures here, minus 20
> Celcius.
>
> Are you sure you want to use glycol? It gets fairly viscous at low
> temperatures, which makes it more difficult to pump around.
>
> Have you thought about a solution of calcium chloride? The freezing
> point can easily be depressed below -20C, and the viscosity stays low.
>
> dow