Subject: Inexpensive Solar Water Heater

From: dale <[email-masked]>
Date: Fri, 05 Apr 1996 18:18:48 +0000

I want to build a solar hot water heater. I have seen some very 
expensive systems sold commercially, but we need something much cheaper 
(we are a foundation running a children¹s camp in Poland).

I have seen lots of designs for inexpensive units, but they all seem to 
have been done by people who have not actually built or tested such a 
unit, but rather have just dreamed one up. 
Some of the designs I have seen come with no information about why 
various choices were made. I would like to start a discussion on this 
subject, and would hope that someone with experience as well as some 
theoreticians would join the discussion.

I want to consider two systems. One for household hot water, and the 
other for heating a small pool or hot tub. 

I want to eliminate a two fluid system because it would be too 
complicated and expensive. I want to solve the freezing problem by 
putting the collector in a glass porch which is attached to the house, 
or perhaps just under the roof behind a purpose built skylight rather 
than on the roof, or in the case of the hot tub, for summer use only. We 
are at 54 degrees north, in the coldest part of Poland.

Although we have electricity on the site, we cannot rely on it.

I have two ideas for circulating the water.  
One is to pump it with a low voltage volt pump which is run directly off 
a solar cell array. No batteries involved. It will only pump during the 
day, but that¹s ok since the water will be heated only when the sun is 
out anyway.

Another possibility, suggested by a badly written book on the subject, 
is to place the collector below the storage, and let convection move the 
hot water up to the storage tank or hot tub.

Some questions.
Would this latter system really work in practice? Is there anyone out 
there with experience with such a system? If so what diameter pipes were 
used? What sort of collector? What distance between the collector and 
the storage? Where was this done? What temperatures were achieved, and 
at what times of year?

With the former system, does anyone know of any pumps that will work 
this way, driven only by sun power without intervening batteries? Do you 
know of such a pump that could be purchased in Europe, or better do you 
know of anyone who would donate one to us?
What is the best collector to use?  We have lots of space, but not lots 
of money. Covering the unit with an expensive insulating glass would 
certainly give higher temperatures and faster heating, but would the 
price difference be worth it? Or without a glass cover, would the 
temperature be too low to be useable? (I am advised that here, in 
Holland, where I live, government regulations require a minimum 
temperature in the hot water tank of 60 degrees C. Otherwise bacteria 
can grow, creating health problems.) 
Would plastic sheeting at less than $1. per sq meter be a better deal 
than double insulated glass at $150. or more per square meter, or  would 
it not work? What about insulating bubble plastic used by some green 
houses, a kind of bubble wrap which givers modest insulation at a very 
low price? Would plane single glass be best?

What kind of collector should we have? What kind and diameter of pipe is 
best? Cheap black plastic hose seems like a good solution, but such 
plastics often disintegrate rapidly at high temperatures. Is there 
anyone out there with experience in this, or who has a knowledge of 
plastics and what to look for and what to avoid?

How about just letting the water spill over a trough and flow down over 
black plastic sheeting place under glass.?

Anyway these are some of the questions I have as I start this quest. 
Perhaps there is a FAQ that I don¹t know about. If so and the answers 
are there, please direct me to it. Likewise if there is a good book on 
the subject, with answers to these sort of questions please direct me 
too it.

In any case I would like to hear from people who have had experience in 
this or are in a position to do some experimenting and calculating for 
us.

You can answer to this news group, or write me directly, or better do 
both. 

Thanks,
dale