Solar-powered computing feels so good: Next – the solar car…

Before the beginning of last winter, my wife Tanya and I decided to take the plunge and go solar in our home on the Hawaiian island of Kauai. It seems crazy that on a group of islands with this much sunshine and wind, 99% of the electricity used is generated from fossil fuels – which of course have to be imported.

We began by focusing on the largest use of power for most people on the islands – hot water. We had a new solar hot water tank installed, and two solar hot water panels put on the roof. It quickly became obvious that – except perhaps once or twice a year, in winter, if there were two or three weeks of constant rain (it does happen!) – we’d never again have to use electricity to heat our water.

Now, at this point you may be saying, “It’s OK for you – you’re in Hawaii!”. But the first solar hot water system we ever installed was in our home in Scotland in around 1983 – at the same latitude as Alaska. In summer, we got all the hot water we needed free. And if there was any sun on a winter’s day (it might have been minus six degrees centigrade at night) the system would still provide about ten degrees of heat. And systems have almost certainly improved since then…

Next stage was to tackle power itself. We found an experienced contractor (who became a friend). He came out with a meter which measured the amount of sunlight we’d be able to harness, and the calculations began.

Most people installing photovoltaic (PV) generation in their homes in Hawaii opt for “Net Metering”. Instead of a large bank of batteries, you use the utility company’s power grid as your battery. When you’re producing more than you’re using, your meter winds backwards. When you’re not – for example, at night – you take power from the grid.

Kauai Island Utility Co-operative (KIUC) is our local utility, and they’re a bit behind the curve. Uncertain as to the overall effect of net metering on their system, they had placed a cap on the percentage of customers who could be on Net Metering.

In any event, we didn’t want to instal a PV system and still be dependent on the grid. On an island like this, where the weather can change quickly, we used to have frequent but short power outages. I think that KIUC switches off power when there’s a thunderstorm passing over the island. It sounds inconvenient, but it does mean that you seldom see a blown transformer – which often happens in thunderstorms on the mainland, and takes much longer to fix.

So we opted for 24 PV panels, and a bank of 16 batteries – enough battery storage to last us for a couple of days without top-up. An Outback controller, and we were set.

We’ve been running the system for several months now. In all that time, we’ve used grid power for less than two hours.

Here’s a typical day. We wake up after running on batteries all night, and the indicator panel in the house tells us we have around 70-75% of power remaining. By around 8.30am (at the moment – perhaps 10am in winter), the panels kick in, and the meter tells us we’re charging again.

By around noon, the system is fully charged once more, and we continue to generate excess power for the remainder of the day. Great time to do a couple of loads of washing in the machine, or run any power tools. That’s also when the house begins to get hot and we need to run a fan. Doesn’t matter what we use – it’s all free power at this point!

The panels generate 3KwH. That may seem like we way over-engineered the system – but there’s method in our madness. Once practical plug-in electric cars hit the market, we intend to buy one – then we’ll never pay for fuel again. We don’t drive a lot of miles anyway. The longest trip is probably from here on the North Shore to Lihue, the largest town on the island – less than 50 miles, round-trip. The system has the spare capacity to keep an electric car fully charged.

We’re not power hogs. We run a couple of computers almost all day, a refrigerator, and not much else. We cook with propane. We watch DVDs at night (can’t stand network or cable TV).

It wasn’t cheap to install the system, and it will take a long time before we ever recover the installation cost. But money’s not everything. It feels great that we’ve reduced our carbon footprint this much, and that we’ve done something to reduce our dependency on fossil fuels – and will do more.

I received an electricity bill for one of the worst months of the winter. It rained a lot last winter, and we’d had to switch on grid power for about an hour and a half. The bill said it all:

Power usage for the same period last year: 710KwH
Power usage this year: 16KwH

Wow! The State of Hawaii should be encouraging this even more! (There are already tax incentives). KIUC should be encouraging it too – because it would save us all a fortune (They recently built a new fossil-fuel generating plant to add capacity).

And the best part of all. There may have been power outages this winter – but we’ve never noticed. The batteries just keep on going…


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