Solar Water Heating Lessons

Solar Water Heating bookI just got back from an 8-hour training in solar water heating offered through the Indiana Office of Energy and Defense.  My brain is a little oversaturated but it was a good course and I’m glad I went.  We even got a really cool book published by Mother Earth News!  Solar water heating is one of those technologies that makes infinite sense to me – capture the sun’s rays to heat our water?  Of course! – but I wanted to learn how they actually work.

The class was taught by a solar system installer from Wisconsin who is associated with the Midwest Renewable Energy Association, which is an awesome resource for sustainable living ideas in the Midwest.  They run a Renewable Energy Fair every year that covers a wide range of topics from constructing a windmill for water pumping to making window quilts to growing food organically.  There’s also a trade show featuring fascinating products like a whole range of hand-operated kitchen appliances and solar ovens that were developed to purify water in third world countries.  I’ve been twice and highly recommend it.

Anyway, in the solar water class we talked about several types of systems and their various benefits and drawbacks.   The  simple DIY version is a black 55-gallon drum enclosed in a glass box (to provide some insulation) mounted somewhere in your yard with good solar exposure.  You run pipes to carry water from your water supply through the drum (where it’s heated) and then back into your house (to your hot water tap).  It’s simple, it’s cheap, and it works pretty well during the summer.

One major drawback is that this system is very vulnerable to freezing so you really can’t use them during the fall, winter, or spring.  The solution is to set up what’s called a closed system.  Instead of running your water directly through the collector (the black drum), you run a propylene glycol solution outside to the collector and then back into the house where it goes through a heat exchanger (picture your car radiator) and transfers its heat to your potable water before returning to the collector. The gylcol solution will stay liquid to a temperature of negative thirty degrees so you can use it all winter long and take advantage of those clear, sunny, cold days.

I found the class very inspiring but I’m still put off by the cost of purchasing a professionally installed system – approximately $10,000 for a family of four.  The instructor ran some calculations showing that if electric rates keep increasing by 7% a year, the system will pay for itself within 20 years.  It’s true but 20 years seems like a long time.  So I’m rather tempted to try the drum-in-a-box version for awhile and see how that goes during the summer.  I also question their estimates on how much hot water people use on average.  20 gallons per person per day seems like a lot of hot water.  Granted, we wash our laundry using cold water and take short showers every 2-3 days so we’re definitely going to be below average but I figure we use less than a third of that.  Do you know how much hot water you use?  And how to measure it?  The book suggests that if you have a plug-in electric water heater you can use a kill-o-watt but ours is hardwired (and isn’t working very well right now anyway – I think it’s 75% full of lime) so I’m not sure what else to try.

There will be two more renewable energy classes this spring so I’m excited.  It’s not often the government throws education and books my way so I plan to take advantage of all of it.  Oh, and for those of you who are curious about the Indiana Department of Energy and Defense, my understanding is that someone somewhere figured out that one of the biggest weaknesses of Homeland Security is the fact that we’re highly dependent on foreign oil (I know you’re all shocked) so they decided to merge Energy with Defense.  I guess it kinda makes sense and if we can divert some tax money away from building bombers and towards building solar panels, I’m all about it. this!

3 Responses so far »

  1. 1

    Amy said,

    March 8, 2008 @ 6:02 am

    Which utility are you on? I used to work for the DSIRE Project at the NC solar center, which tracks incentives to renewable energy and energy efficiency at the state, local and utility levels. Maybe there’s a rebate out there if you were to install a system like this – it would be exempt from property tax 😉

  2. 2

    Will said,

    March 8, 2008 @ 4:39 pm

    We use Duke Energy. According to Choose Renewables there aren’t any incentives for wind/solar in the area. On the other hand, there seem to be a lot of rebates for geothermal heat pumps, so that might be worth looking into. I have no idea how much those cost, though.

  3. 3

    solar said,

    October 9, 2008 @ 9:42 am

    Yes! Keeping in mind the drastic environmental changes and rising fuel prices going Solar is one option open to all at minimal investments. The Solar Water heating systems are so easy to install and most of them come in a Do-it Yourself kit, With the technological advancement the once heavy, bulky hard to move panels are now available widely in light weight easy to carry by one personal only packages. The advancement in technology is not only limited to light weight, but for those concern about the aesthetics of the panels, the good news is that the panels are now available with a variety of trim colors to choose from and can be easily matched to your roof. Saving about $25.oo on ones electricity bill every month on a residence of 4. We all use hot water, as one of our basic needs and what can be a better way, than helping our environment, saving our resources and ourself’s some money other than by investing in a Solar Water Heating System.
    There are a couple useful websites I’m aware off, that I would like to share with you
    1. – is a comprehensive source of information on state, local
    , utility ans federal incentives that promote renewable engery ans energy efficieny.
    2. – one of the many manufacturers of certified Solar Water Heating Systems available. One place I saw the light weight panels and trim color options I was mentioning earlier.
    Lastly, the local utilites in some areas also provide additional rebates and incentives for adding a Solar Water Heating Sytem to your exisitng water tank.
    Keep the look out on. Feel Good and save- money for you, environment for us.

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