Monday, October 5, 2009

First Year Performance for $1K Solar Water Heating System

The first full year of performance for the $1K Solar Water Heating system is in the books.  The graph below shows Solar Fraction by month.

All the details, and detailed plots that show collector, tank top, tank bottom, and ambient temperature are here...

So, this is the end of the promised one year of logging -- I now get my loggers back for other projects!

I've also a added a page that describes how I estimate Solar Fraction,
and considers some sources of error, and describes how my method
differs from the SRCC ratings of solar water heating systems.



  1. Very nice Gary.
    I see you are short on monitoring/logging equipment. When I am finally finished doing this write-up on the One-wire sensors, I am sure you will want to try it. The most expensive parts are the sensors, at about $5 each. Second would be running a small computer all the time to monitor the sensors.

  2. Hi Doug,
    Yes -- I'd like to try the 1-wire approach.
    I do like my Hobo loggers, but it seems like the 1-wire would be perfect for long term monitoring as they are cheap enough you could just leave them in place indefinitely.

  3. Gary,
    I've been a builditsolar fan for awhile now but just started going through your blog.
    This is a really great post. I've done something related with energy consumption and outside temperature on my blog:
    Did you consider measuring flow rate at all during this experiment so you could see the BTU's your system produced?
    Would it be possible to re-post this on my blog giving all credit to you?

  4. Hi,
    That is interesting how well your power consumption tracks outside temperature.
    I have a TED, but have not made a lot of use of it -- mostly out of laziness. Its a very nice way to measure and log consumption.
    The thing I would really like to do with the TED is to move the little current transformer loops to each individual circuit in the house and track each circuit for a few days. The idea would be to get a better idea what all the loads in the house are, and how significant they are. When I turn off everything that is easy to turn off, I'm still left with a substantial amount of power use -- around 300 watts as I recall. I'd like to figure out exactly what this "base" load is and see if I can do something about it.
    If I ever build a new house, I'm going to review every single thing that goes into the house that used electricity and understand its power consumption -- I bet that this approach could save building in a lot extra consumption. I wonder about how much power things like that transformer for my door bell are using 24/7, day after day.
    I would like to have measured and logged flow rates for the solar hot water system, but the cost and effort to put in a flow meter were a bit more than I wanted to spend. It would be good data to have.
    Feel free to re-post this blog entry on your site -- and thanks for asking!

  5. Wow,Gary,
    Looks like you have very good result from using this solar water heating system.

  6. Hi,
    The performance has been very good.
    One thing to bear in mind is that there are only 2 of us, and our hot water use is pretty low -- so, most families would want more collector area.
    I'm actually in the process of replacing the collector with one that is about 2.5 times as large so that I can use the excess heat for space heating the bedroom area. Plan to keep the same tank and controls, so not too big a job.
    This did give me a chance to cut apart the old collector to see how everything was doing internally -- it all looked very good. No deterioration that I could see, and the PEX tubing was bonded very tightly and uniformly to the aluminum fins by the silicone. I'll put up some pictures in a while.


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