Thursday, 28 May 2009

Old watermill - reliable electricity - it works!

Last week Nikita and I visited Chris Geake and his family in the Green of Central Portugal, somewhere North of Coimbra in picturesque rolling hills and woodlands.

Chris is the first person I have yet come accross to have installed a micro-hydro electric system in an old watermill. I had to visit.

Like most old watermills in Portugal, there is a water channel running a hundred meters or so from a diversion weir on the main river. The channel carries around 100 litres per second (though we didn't measure it while I was there).

Also like most watermills here drop (head) between the water channel and the space where the horizontal wheel would have been (or where a hydro-turbine could be) is only about 1.6m, which is really low, too low for most hydro engineers to get very excited about.

But this is the challenge: finding a system that can generate enough power, or mechanical energy, to make the investment worthwhile.

Chris has shown that is is possible, viable and worth the investment. His enthusiam, vision and determination really help too. Here's what he has done:

- made contact with Powerpal's UK distributor. The Powerpal is a wonderfully simple system first designed in Canada by geologist David Seymour who says he was motivated "out of a desire to help bring some electricity to remote parts of the world where the residents considered even a few hundred watts of AC power quite a luxury". He has established a relationship with a workshop in Vietnam where the turbines are assembled.

- Powerpal UK's engineer agreed to come out to help with design and power connection and together with Chris he put it together.

As you can see from the photos, the installation of the turbine is really simple: just build a little channel that feeds into a trough, where the turbine sites. It works on "suction head": a flume below the turbine is set at least 20cm into the water at the bottom of the chamber, so there is a vacuum. The flume is slightly wider at the bottom, so there is a tremendous draw or pull on the water coming through the turbine. The spinning turbine provides rotational force to the generator which send power to the batteries, in a seperate building some 30 m away.

- The powerpal they selected is a 500w capacity system. That means it can generate up to 500 watt hours in one hour. Or 0.5 Kwh. Chris reckons he gets about 10Kwh a day, which is about 300 Kwh per month, potentially 3,600 per year (about the same as a small house might use in a year). As there are times when rainfall is lower, the amount of flow is less, so this cannot be expected year round, but still it's enough to run everything he has in the house, including a washing machine, fridge, low energy lights, etc.

- Their house is not connected to the grid, so instead of paying thousands to the national power company (EDP) to get linked up, they invested a few grand in batteries, invertor and all the other gear needed to provide 220 v power that most application need.

- If he were connected to the grid, and if he wanted to sell that power to EDP, on the new micro-generation tariff (for micro renewable energy systems) he could get 0.18 euros / kwh. So his 3,600 Kwh per year would be equivalent to around 650 euros a year. "Beer money" you might say, but it all adds up.

- Chris has pointed out that he could install a second unit beside the first, thus doubling his output, but as he doesn't really need all that much more, why bother?

- One option for such cases is to use the power to create heat - not in the usual way that dump loads work (heating up water with an element like a kettle does: 1kw in gives 1 kw out, probably less given some losses) but by running heat pump, which requires around 1kw of electrical energy to delivery approx. 3.6 kw of heat. This assumes a radiator or underfloor heating system is in place. In Chris's case, they have plenty of wood avaialble and a wood burning stove, and it probably isn't really worthwhile but for others, it could be more interesting. Knowing how much work it is to source, chop, dry, store and move wood all year for the winter fires, I could be interested, but that's another story.

- Using water from the river doesn't come without problems however. By its nature, it's full of leaves and other debris, as well as living things like fish and eels. These can get drawn down the channel and caught in the turbine blades - only very occassionaly the living things - the leaves and bits of wood are the problem. Without a good screen, he has to spend a fair bit of time clearing the debris from the turbine blades, although most of them, he says, just get flung through it.

He has set up a clever bit of wood that diverts surface floaters, but is keen to talk to someone who can design an angled screed which sits vertically beside the intake, like the one in the picture, with small enough holes to prevent debris coming through, large enough to allow sufficient flow, angled enough so leaves and stuff don't get stuck in the holes and create blockages. Ideas are welcome.


They have a lovely place, were so hospitable and friendly we felt as if we'd known them for years. They're heading back to their UK homeland later in the year (Chris is a firefighter - an honourable profession for sure) so their place will be up for short rents for those wanting to check out the system, have a break in a very peaceful part of the world beside a beautiful river, full with fish, turtles, otters and other characters.

More info on their blog here

More photos of their place here

2 comments:

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