It’s Not Easy Being Green!

Actually it is easy. We’re talking about saving energy and preserving the environment here, of course. Having said that, most people want to save energy because it will save them money, especially in the current financial climate.

Since I was a teenager, I experimented with PV (Photo-Voltaic) solar cells, using motors to generate electricity etc. Of course, it was all on a very small scale – the solar cells gave enough power to drive a small 1.5 volt motor, and the motor when used as a generator could run an LED (Light Emitting Diode).

The thing is, back in those days, solar cells were phenomenally expensive and quite inefficient. You would need a huge array of them to generate any useful electricity, which would not only take up a lot of space, but would be prohibitively expensive.

Today, solar cells are still expensive, but much less so. They are also a lot more efficient than before. It is now possible to supply a house’s requirements for electricity if its roof is covered in solar cells. Some power companies even pay you for generating your own electricity due to various governemt “feed-in tariff” schemes. These feed-in tariff payments are a good subsidy for offsetting the initial outlay for the solar panels. Note: In the UK, you qualify for feed-in tariffs only if you buy your solar panels from an approved dealer/installer. Home-made ones don’t qualify, but you do get the benefit of free electricity.

As a life-long DIY enthusiast, I’m all for making my own energy systems. I’m not planning on installing PV solar panels on my roof just yet, but I am working towards the construction of a solar water heater.

Green Energy Blueprint

Basically, this is an array of pipes enclosed in a box with a glass front, which is exposed to the sun. The sun heats up the pipes and the liquid within them. This liquid is then pumped into the heat exchanger coil of a hot water tank to heat up the water inside. The pump is electrically operated, powered from a modest solar panel. Some simple electronics measures the temperature of the heater and the temperature of the water tank and compares them. If the water needs to be heated, the pump is switched on, otherwise it remains off.

The liquid inside the water heater can be water, but if you live in an area that gets frost and/or snow as I do, it will freeze and stop working. Instead, a non-toxic anti-freeze is used. Alternatively, mineral oil may be used as it doesn’t freeze and is non-corrosive as some anti-freezes are.

This is only a water heater – it doesn’t generate electricity. But as my water is currently heated by electricity, this solar water heater will save me a lot of electricity and money.

I have spoken to the vendor of some commercial solar water heaters and their price was in the order of £7,500, installed. I believe I can make an equivalent water heater for around £500, including the necessary hot water tank, expansion tank, pipework etc.
Construction will require basic carpentry and plumbing skills.
I honestly believe that the prices of commercial units are artificially over-inflated. if enough people made their own and demonstrated how cheap and easy it can be, I’m sure the commercial units would come down in price.

Installation is not going to be difficult as I have a south-facing, low, flat roof that I can mount it on.

I plan to write more about this project on this site.

September 9, 2011 · Phil Rogers · 2 Comments
Tags: , ,  · Posted in: DIY - Home Improvement

2 Responses

  1. Carolyn - September 16, 2011

    Instead of building a solar water heater, go for the solar electric panels. You don’t have anything that will freeze and burst, will heat water in an electric water heater plus you will have savings on your overall electric bill. Maybe add a small windmill to the array and have enough electric to power every thing.
    Most of the programs I have looked at included solar and wind diagrams for construction and installation.
    Very nice site. You have been working!

  2. Phil Rogers - September 16, 2011

    Thanks for your comment.
    With non-toxic antifreeze or mineral oil as the heating medium, the system will not freeze.
    PV panels are very expensive here (UK), and I don’t have the resources to buy them. I can make the solar water heater very cheaply – about one fifteenth of the price of an equivalent commercial one, so it’s something that’s definitely worth doing. And if I make it myself, I can maintain and repair it myself should that become necessary.

    There are companies here that will install PV panels for free. They get their money back from the “feed-in” tariffs that the power companies and the government have set up. In the meantime, you get to use the free electricity. I may consider this and wind power in future, in addition to the water heater.

    As I understand it, crystalline silicon PV cells have a theoretical efficiency of 29%. A Flat Plate solar water heater has an efficiency as high as 60% (better in some cases). As I need hot water, it doesn’t make sense to use sunlight to make electricity and then heat water electrically (which has further losses in it).

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