$1000 Solar Water Heater -- Does it meet the objectives?



These are my thoughts on how well the design have been met (or not) so far:



Cost $1000 or less

I believe that this objective has been met.  
The cost summary gives dollar costs for all the components.

My system has been completed and is operating, and the estimated materials cost is less than $1000

Work in a Cold Climate

I believe that its likely that this objective will be met.

The system uses a drain back design, which has a proven record of working well in cold climates.
My drain back space heating system has been in operation for 2 winters, and been subjected to -30F with no ill effects.
The only negative I see is that the serpentine pattern used on the PEX version may not drain back as well, but the tests indicate that it will likely be fine.

High Performance

Its a bit early to be know on this.
Based on the performance testing I've done so far, and performance of the system so far (only 2 weeks), I think there is a good chance of meeting the performance objective of achieving a solar fraction greater than 75%.
By the end of the winter, it should be pretty clear how well it does.


Long Life

Only time will tell.

I have tried to select high quality materials, that will hold up to the conditions the collector subjects them to:


Glazing -- SunTuf polycarbonate --while this material is guaranteed for "life", I think that its likely that reglazing may be needed in about 15 years (but hard to tell). 


Tank -- EPDM lined tanks have a track record of 15 year life, especially when temperatures are kept below 170F.  The wood frame and sides should last a very long time as long as they are kept in a reasonably dry environment (not sitting in a puddle).
They can be inspected from time to time, and steps can be taken if deterioration is observed.  Conditions that are bad enough to lead to wood integrity problems in the tank cannot be good for your crawl space or basement either, and need to be corrected.


Collector frame -- If the collector frame is painted and perhaps repainted once in a while, I don't see why its any different than all the rest of the wood on your house.  NZ Mike reports very good results with a "two pot" epoxy paint, and this might be a way to get longer life and less maintenance.  But, I've not been able to find a US source for this material.


Collector internals -- The copper, aluminum, and silicone used in the copper version are all high temperature, high durability materials, and should live longer than you. 
The PEX in the PEX collector is a bit more of a question mark.  My gut says that it will do very well as long as its protected high temperature stagnation events, but only time will tell.


Pump -- The pump is still an open issue.  I would like to find a pump that can be counted on to operate for 15+ years and not cost an arm and a leg.  In this system, the tank temperature is kept down to 140F, so life is not so hard for the pump in this regard.

If you know of any good candidates, please let me know.


Controls -- The differential controller should have a fairly long and boring life.  The temperature sensors that report to the controller may have a somewhat shorter life, but I am not certain of this.  But, these components would be the same ones used in the best of commercial systems.

Easy To Build

You can evaluate the how-to picture sequences and judge for yourself.  I think that the construction is fairly simple.


But, while no single component is that difficult to build, there are several major components, so the total time adds up.

Its not a one weekend project -- at least not for me.


Not Ugly

Well, I guess ugly is in the eye of the beholder -- I think it looks beautiful :)



Comments welcome...



Gary September 25,  2008