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Solar hot water delivered quicker and cheaper

Posted by Cathy Debenham on 20 July 2010 at 9:10 am

A system that delivers solar water heating at a lower cost, quicker installation and with no need to buy a new cylinder was one of the finalists in the 2010 Ashden Awards for sustainable energy.

John Willis invented the Willis Solasyphon because he found that the cost and disruption of installing solar water heating was a barrier to take-up. He was also dismayed by the number of perfectly serviceable cylinders he was removing to install a new twin coil cylinder for a traditional solar hot water system.

The Solasyphon is a small heat exchanger that can be installed on the outside of an existing cylinder. This reduces installation time by at least a day, and makes it a much simpler job. So, as well as the cost savings for consumers, installers can put it in without disturbing the existing plumbing system.

Water is heated faster with the Solasyphon, as it heats small amounts of water at a time in the heat exchanger, and delivers it to the top of the cylinder where it stratifies ready for use. Standard European tests found that it produces a higher water temperature compared to conventional technology. A benefit of this is that it heats water to useable temperatures in marginal conditions (such as autumn or winter).  

In the commonly used dual coil cylinder, a much greater amount of water is heated, more slowly, by the coil. This means that rather than having water hot enough to use at the top of the cylinder, the solar panels raise the temperature of all the water in the cylinder, but in marginal conditions it still needs to be boosted by the boiler or immersion to reach a usable temperature.

“Weve had the Solasyphon in place for three years, now and it’s been absolutely fantastic,” says Liz McElkerney, a Willis customer. “We have piping hot water all day long. It starts working as soon as the sun hits the solar panel. It’s brilliant in winter as it activates with the winter sun, so we’re not dependent on a really hot sunny day.”

The Willis Solasyphon can be used as part of a MCS accredited solar hot water installation. Section 442 of the MCS has been amended to allow for an external heat exchanger to be used on an existing cylinder, as long as the cylinder meets the stated standards. It is also included in a field trial of solar hot water systems currently being undertaken by the Energy Saving Trust, which is expected to report next year.

Using a Solasyphon saves between £600 and £1,200 on installation costs compared to a conventional system. By

If you have a question about anything in the above blog, please ask it in the comments section below.

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2 comments - read them below or add one

Jayhawk International Ltd

Jayhawk International LtdComment left on: 20 July 2010 at 1:04 pm

Unlike the Willis system which may be excepted within the MCS scheme, our Solarthermix system from under £1,000 for the complete system package that is designed for 150 litre vented copper cylinders will not be approved becouse its not seen as of a higher enough standard as the existing tank is used with 50% of the industries solar related componant parts deleted in our design to keep it simple, safe and service free

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Jayhawk International Ltd

Jayhawk International LtdComment left on: 20 July 2010 at 1:00 pm

I agree with Willis about the wastefullness we now have from the disposal of perfectly good copper cylinders, often only a few years old even months depending if like me I bought a new house and the first thing to go was the cylinder as I wanted instead a thermal store so my solar collectors could support my space heating, not just deliver a tank of water.

Later this year Jayhawk International Ltd will be marketing its own new freeze free solar collector and its proven Solarthermix valve which converts an existing copper vented cylinder to solar direct and no need for 2-3 year servicing as will be needed for a closed loop Gylcol filled system.

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