Subject: solar Water Heater

From: dale <[email-masked]>
Date: Wed, 20 Mar 1996 08:42:25 +0000

Sometime this summer I hope to begin building some log cabins at our 
children¹s farm camp. I would like include some solar energy features in 
these cabins. 

One system I am interested in is a solar water heater, to be used both 
for heating water for baths and also possibly providing warmth in 
certain parts of the house during the day or to a hot tub, etc.
 
I would like to use long coils of black hose as the primary collector. 

The problem is that in a cold climate, we are in NE Poland,  the water 
can freeze in the pipes during the winter. Most systems compensate for 
this by an elaborate and expensive dual (alcohol-water) system or an 
expensive insulated glass system. I would like to do with with a simpler 
system, and my idea is to place the absorption coils inside the house, 
in a sera (glass sun porch) attached to the south end of the house. The 
porch would not be heated as thoroughly as the rest of the house, just 
keep above freezing during the winter, unless the sun warmes it further.  

Another idea is to use as the primary heat absorbing coils, a black 
plastic hose that could handle the expansion that would occur when the 
water froze. In this case, only the pump would have to be protected from 
freezing by keeping it indoors. 

Further, I would like to pump the water in this system with a low 
voltage water pump that could be connected directly to a set of solar 
cells without any intervening battery. After all there is no sense 
pumping water when there is no sun. Does such a pump exist?

 Finally, is there any reason why the system shouldn¹t drain from the 
collector coils whenever the system shuts down, thereby providing 
further protection from freezing?

Using one, or a combination of these ideas, I would hope to be able to 
construct a very inexpensive system.

Can anyone suggest how much and what kind of hose would be required for 
such a system? Are there charts available for calculating this?

Can anyone recommend a good book on this subject?

Is there anyone who has any experience with this sort of system. What 
problems might you foresee? And does anyone know of a pump that could be 
driven directly from solar cells without intervening batteries or 
electronics?

Finally, is there an FAQ for this group?

Any comments would be appreciated.

Dale

---

From: Wirral Energy Advice Centre <[email-masked]>
Date: Fri, 22 Mar 1996 16:58:53 +0000

In article <[email-masked]>, dale <[email-masked]> writes
>
>
>One system I am interested in is a solar water heater, to be used both =
>
>for heating water for baths and also possibly providing warmth in =
>
>certain parts of the house during the day or to a hot tub, etc. =

> Generally, it is very difficult to space heat from active solar
heating since the solar energy supply ( daytime & summer ) is out of
phase of the demand ( nightime & winter ). Whereas it is striaght-
forward to supply domestic hot water since the heat can be stored easily
and the demand is more in phase with supply. I have fitted space-heating
>from  solar water heating but only as excess heat-dumps for drying
clothes which automatically cut in when the solar store reaches 70 C.
>
>I would like to use long coils of black hose as the primary collector. =
>
>A similar principle is used by a few commercial manufacturers in the
U.K. for swimming pools. However an unglazed collector is only suitable
for sub 30 C. water temperatures and become wildly ineffecient at normal
domestic bath temperatures. These are mainly direct systems and
occasionally of the drain-back type.

>The problem is that in a cold climate, we are in NE Poland,  the water =
>
>can freeze in the pipes during the winter. Most systems compensate for =
>
>this by an elaborate and expensive dual (alcohol-water) system or an =
>
>expensive insulated glass system. I would like to do with with a simpler =
>
>system, and my idea is to place the absorption coils inside the house, =
>
>in a sera (glass sun porch) attached to the south end of the house. The =
>
>porch would not be heated as thoroughly as the rest of the house, just =
>
>keep above freezing during the winter, unless the sun warmes it further.  =
>
Technical problems here may include any flexible pipes collapsing from
negative pressure if a pump is used depending on hight levels. Also how
are you supporting the pipes and at what inclination to the horizon. If
horizontal, you will need a glass roof to get realistic performance.

>
>Another idea is to use as the primary heat absorbing coils, a black =
>
>plastic hose that could handle the expansion that would occur when the =
>
>water froze. In this case, only the pump would have to be protected from =
>
>freezing by keeping it indoors. =
>

Interesting, but if you have a pumped system there may be problems with
part freezing during a thaw. The pump may try to operate with a blocked
pipe. 
>
>Further, I would like to pump the water in this system with a low =
>
>voltage water pump that could be connected directly to a set of solar =
>
>cells without any intervening battery. After all there is no sense =
>

Certainly does .  German manufacture, 5 Watt consumption , Impedance
matched for direct operation from a PV module. Aprox. £200 in U.K.
>
> Finally, is there any reason why the system shouldn=B9t drain from the =
>
>collector coils whenever the system shuts down, thereby providing =
>

None, provided the collector is higher than the store and an open vent
or automatic bleed vent is used ( but only float types )
>
>Using one, or a combination of these ideas, I would hope to be able to =
>
>Can anyone suggest how much and what kind of hose would be required for =
>

>
>Is there anyone who has any experience with this sort of system. What =
>
>problems might you foresee? And does anyone know of a pump that could be =
>
>driven directly from solar cells without intervening batteries or =
>
>electronics?

None of my designs in this area have come to fruition but I have already
researched a lot of what you are proposing.  Post some more details and
I return some more.

-- 
Wirral Energy Advice Centre