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More adventures in solar power

I'm happy to say we've been able to run a 20W halogen lamp and charge mobile phones & other batteries off the renewable energy system I set up a few months ago. While it's nice to be able to use the system, I've also learned a few lessons about the practicality of our current setup, and have ran into a few limitations:

  1. The battery bank can only store 24Ah of energy, which isn't all that much

  2. The 15W amorphous solar panels aren't that efficient - they gather maybe 1-5Ah/day, which means it can take weeks to fully charge the batteries

  3. You loose a lot of energy converting the power:

    The 12V DC - 230V AC power inverter consumes ~0.7A @ 12V = 8.4W!

    The transformers that most devices require use even more power (I've not measured how much)

  4. We had no way of tracking how much power we were generating & consuming

  5. When the inverter is close to running out of power it complains with a rather loud beep!

  6. It's very inconvenient to use something when you have to worry about turning the inverter on & off

Altogether, this makes our initial setup rather impractical. That's why I decided a few weeks ago to try and solve these problems by increasing capacity, decreasing consumption, and introducing a monitoring system. My goal is to produce a practical & convenient system that we'll use on a day-to-day basis.

Adding a monitoring system was the first step, and the easiest one. After an extensive research effort I decided the Steca PR1010 was the best fit for what I was trying to do. The best price I could find for it was on the Alternative Energy Store for £62. They were extremely helpful there, and delivered the item within 2 days - consider me a happy customer! Installing it was also a breeze, and instantly gave me the information I was looking for.

Next, I focused on increasing capacity. So far that's also been relatively easy, though again I spent a lot of time researching the options. While wind power is interesting, I decided to shelve the idea for now - it's either a lot more expensive to buy turbines, or a lot more effort to make them. Not that solar panels are cheap, mind you - this has probably been the most expensive part of my experiment. After shopping around, I opted for 2x 40W panels from a well-known brand, Kyocera (the KC40T modules). The best prices I found were from a company called Bright Green Energy, and the person I dealt with (named Alex) was extremely helpful... he went out of his way to ensure the panels were delivered within 2 days - again, a happy customer.

I've not yet bought a bigger battery, but I've got my eye on a Numax XV31MF sealed lead acid battery from Soapy Smith's. 113Ah would give us almost 5x the capacity we have at the moment! Unfortunately, since we've moved homes recently I've had to dismantle the whole system. Getting a new battery can wait until I've had a chance to settle in!

Still, with the 2 new panels hooked up, I was able to fully charge the batteries within 2-3 sunny days (with the position of the panels we only got 3-4hrs sunlight). With all 95W of panels I've seen 5-6 Amps going into the batteries which is a lot better than the 1A max I saw with only the 3x 5W panels. So I'm on the right track.

Decreasing consumption has proven to be the most challenging step, and I'm still experimenting with things. The key challenge is that most consumer devices are shipped to work at mains voltage (230V @ 50Hz AC in the UK). While cars, caravans & boats tend to operate on 12V or 24V DC, they're backed by an engine-powered alternator which means product designers don't have to be as worried about energy consumption. I've decided to tackle lighting first as they've proven to be the biggest consumers I have.

Anyways, more on that later.


Oct. 24th, 2007 04:59 pm (UTC)
Sounds awesome, Steve! You seem really interested in this stuff. Have you considered working for a company that consults/advises re: alternate energy or something of that sort? I think it'd be right up your alley. Or is this more of a hobby sort of thing?

How's the new place, by the way?
Oct. 25th, 2007 03:11 pm (UTC)
Well, I consider it more of a hobby at the mo, but who knows, maybe I'll get sick of IT and change careers? ;-)

The new place is much more homey than the last... we're still settling in (and completely sick of boxes). Will post some pics once we get internet sorted.