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How to retrofit solar panels: Steve Harris responds to Bill Gething

As part of AJ's Sustainability in Practice series, Bill Gething of Feilden Clegg Bradley Studios outlined a method of retrofitting solar thermal panels (AJ 12.06.08). Steve Harris of ZEDfactory believes there is a more efficient way: here he outlines his dos and don'ts.

Bill Gething’s system (AJ 12.06.08) is great but he has spent over £3,000 and still needs a boiler in the summer. He claims that solar thermal can provide 60 per cent of your hot water, while at ZEDfactory, we believe it can also provide most of your heat. If you are going to spend £3,000, do it right!

Don’t waste your time messing about with inefficient, (roof) space-hungry flat-plate collectors that don’t work in the autumn/winter and spring.

Don’t mess about with small twin-coil tanks that only preheat your water, meaning that you still have to run a boiler to boost the temperatures, even on a sunny day.

Do install proper twin-wall evacuated tube systems. Twin-wall tubes can give you 70-degree heat on a sunny, frosty day.

Do use a heat store rather than a hot-water cylinder.


You will need:

2 no. ZEDfabric (or equal) 16 tube twin-skin U-tube solar arrays: £900 +VAT

A ZEDstore thermal store £1,350 +VAT

A 30W ZEDfabric PV panel to run the pump and controller £125 +VAT

15mm copper pipe is about £2 a metre, high-temperature insulation about £5 a metre.

Either a local plumber who doesn’t mind going on roofs or a local roofer who doesn’t mind joining pipes together to put the panels on your roof, run the pipes up and down from the store and connect the PV panel and sensor.

If you are brave, you could even DIY! That is what it’s designed for.

Payback

Assuming your outlay is £3,000, the value of the heat you harvest in a year will be greater than the annual cost of servicing the loan to pay for your panels within five years.

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