What happens to a solar power microgrid in a hurricane

A news bulletin from Kiva:

As you may know, Hurricane Matthew, a category 4 storm, made landfall in Les Anglais [Haiti] at the beginning of October [2016].* In the run up to the storm, our staff members told the community that they should charge their electronics soon as they would have to turn off the grid. They then secured the generation site with sandbags and found safe spaces for staff.

After the storm hit, the community was devastated. As most of the houses in Les Anglais are made with straw or sheet metal, virtually all of those houses lost their roofs. About 30% of the community completely lost their homes and some have left the area to stay with family elsewhere. Even worse, about 90 people in the entire commune of about 30,000 people lost their lives.

Within a few days of the hurricane, humanitarian relief was able to arrive by barge and a week later the roads were opened up to allow relief by trucks. People are slowly starting to rebuild. Aside from re-building homes, much work will have to be done to restore agriculture in the area as many crops have been destroyed.

The microgrid fared comparatively well. About 40% of the panels were lost, but the battery bank, inverters and generator were left unscathed. The worst damage was to the distribution system and home installations. When roofs were torn off due to the winds, most of the wires, light sockets and outlets that comprised the home installations were blown away as well.

The community is eager for the grid to be up and running again and we are putting in place a plan to rebuild as the community is able to rebuild their homes. We anticipate this taking about 6-9 months to finish.

Kiva, if you don’t know it, is an international microfinance charity lending to small borrowers in (mostly) developing nations. They do good work – read more here – but my interest in this bulletin was how the solar power facility fared in the hurricane. The short answer: not too badly at all. In fact, it sounds like it could have been operational again, albeit with fewer panels and a severely limited distribution network, a couple of days after the storm passed.

That kind of resilience will be needed everywhere, and especially in developing nations, to cope with extreme weather events increasing because of climate change.

* More on Hurricane Matthew in Haiti: wikipedia

Home solar update

The 1.5 KW solar system on our roof has just passed a good round number in its total output – 12 000 kWh, or 12 MWh – and that’s a good enough excuse for another update.

We installed the system in May 2011 so it has produced an average of 6.26 kWh per day for five years. That’s a useful percentage of a household’s consumption: according to Ergon’s figures on the back of our power bill, the average consumption for a household like ours is about 20 kWh per day, so our panels are producing nearly a third as much as we use.

Of course, we use some of our solar power during the day and export the rest of it, and then use Ergon’s power all night, so our net benefit doesn’t quite reflect those numbers. I did the sums a year after the installation and came up with a figure of $700 p.a., with the expectation that that would increase if power prices increased. Using the same logic now for the five year period, we find:

  • Total produced = 12 000 kWh (6.26 kWh/day)
  • Total exported to grid ~ 5200 kWh, for ~ $2300 income
  • Total PV power used at home ~ 6800 kWh, for ~ $1700 savings
  • Total benefit ~ $4000

In 2011 I said:

All in all, making the best guesses I can for the unknowns, pay-back time for the whole project (PV system and switchboard) looks like being in the 5 – 8 year range. That’s perfectly acceptable … Of course, if the electricity tariff rises (hands up everyone who thinks it is going to fall? No, my hand didn’t go up either), pay-back time will drop accordingly.

The cost for the system was $3500. Even if my new figures on exports and savings are on the optimistic side, it looks like our system has paid for itself, just a few months ahead of the earliest date I anticipated.

That’s pleasing, of course. The thought that it will continue to  bring us that $800 p.a. benefit indefinitely is even more pleasing. So is the thought that we have done our little bit to reduce CO2 emissions, and that it has basically cost us nothing to do so.

Was there any downside?  Maintenance costs? Repair costs after the cyclone? None at all. It just sits there quietly on the roof, collecting photons and turning them into useable electricity, day after day.

For the record, the general tariff was 19.4 c/kWh when we installed the system five years ago, had risen to 30.8 c/kWh by July 2014 and has now (surprisingly) dropped back to 22.3 c/kWh. In May 2011 the “service fee” or “daily supply charge” was only $23 per quarter, whereas by May 2014 it had risen to 55 cents per day ($49 per quarter). It has continued to rise and is now $1.07 per day, closing in on $100 per quarter. The supplier is simply trying to maintain revenue in the face of flat or falling demand and the service fee is a favoured strategy – but that’s a topic for another day.

PV solar from toy-size to utility-scale

Tandy 'Science Fair' Solar Power Lab, c. 1978
Tandy ‘Science Fair’ Solar Power Lab, c. 1978

We came across a time capsule when we were clearing out a spare room a few months ago: a ‘Solar Power Lab’ given by one family member to another nearly forty years ago and passed down through the family ever since.

Project list
Project list

Photovoltaic cells were cutting-edge technology back then. The cells in the  kit – four of them, each about 5 x 1 cm, in a line along the back of the circuit board – were novel enough to be the selling point of an otherwise unremarkable electronics construction kit, and may well have accounted for half the cost of the kit.

The introduction to the manual, like the box, was all about the ‘space age’ technology used to power satellites – which were big news themselves in those days.

The ingenious recipient could construct any of twenty-odd projects, from logic gates (these were the days when home computers with 64KB of memory were considered powerful) to LED demonstration gadgets (LEDs were new, too) to transistor radios.

Construction manual
Construction manual

Moore’s Law was relatively new back then, too. I wonder how many people had any idea what its impact would be over the ensuing forty years? The purely quantitative differences have been so large that they have led to qualitative differences (from “big data” to the ubiquity of mobile phones.)

And solar power has grown almost beyond belief, too, on a similar path of dramatically falling costs and steadily improving efficiency. This ThinkProgress article presents a good overview of the current state of play, with one chart which sums it up beautifully:

Solar’s exponentially declining costs and exponentially rising installations (the y-axis is a logarithmic scale)
Solar’s exponentially declining costs and exponentially rising installations (the  vertical axis is a logarithmic scale)

Progress hasn’t been as rapid in solar power as in computing (Varun Sivaram explains why here, if you’re interested) but has been enough to overtake older technologies and to transform our future.

Once again, quantitative improvements have led to qualitative changes. Solar power is no longer a novelty and no longer a last resort for difficult situations such as satellites, but a realistic, cost-effective solution for all sorts of applications. Garden lights? Solar, of course – it saves wiring them in. Bore pumps? Solar, of course – no need to cart diesel down to the pump every few days. New suburbs? Solar with grid backup – not even vice versa. Parking meters? Lanterns for remote PNG villages? Traffic hazard warning signs? Domestic hot water systems? Solar, solar, solar.

Having kittens

It is an embarrassingly long time since my last post but a large part of the reason is that I was busy doing other good things, so I don’t feel quite so bad about the gap as I would otherwise have done. My major project was setting up the website for Kittens for the Reef, a cute video which I think everyone should watch:

Kittens for the Reef was launched on May 31 by one of its stars, Dr Charlie Veron (Fluffy couldn’t make it) at Townsville’s Eco-fiesta, an annual event which brings together all sorts of greenies. I attended and enjoyed it, as I have in previous years.

There is usually a new gadget or idea which catches my attention more than the others, and this year it was a cleverly designed and engineered portable solar power system from SolairForce. Continue reading “Having kittens”