Monday, March 23, 2009


I saw my first green flash for 2009 a few days ago. Most Caribbean people know what the green flash is. It’s the fleeting change of colour of the last sliver of a setting sun at a clear horizon – from red to green – and it’s gone in an instant.

The (totally exaggerated) green flash depicted in the movie “Pirates of the Caribbean: At World’s End”. The first of the “Pirates” series was filmed in St Vincent & the Grenadines and other Caribbean islands.
Photo: Wikipedia

Later that night, I wondered: is there a green flash at sunrise as well? I’m not a morning person, so I would hardly know. But I figured there should be, since the physics of it (as far as I can tell) would be the same.

In any case, here’s a prediction about solar energy in the Caribbean: sunrise is coming and we’re about to see our green flash. That’s because as oil prices climb back to uncomfortable levels; as energy policy in the Caribbean adjusts to the new global reality; as technology continues to improve and prices continue to fall, electricity generated by photovoltaics will become very popular in these parts.

Photovoltaics (PV) is the name for the process by which light is converted directly to electricity by a solar cell. We’ve got lots of PV-powered devices around already. Look at a pocket calculator. Instead of a battery, it’s got a solar cell on the front that provides the electricity it needs. The same basic technology, on a larger scale and with a few additional devices, is already being used to power homes and businesses worldwide.

A typical home PV system would consist of roof-mounted solar panels, connected to an inverter (a device that converts the direct current produced by the solar panels into an alternating current, which is the same as the electricity that you buy from your electricity company). The inverter is connected via a switch to the main circuit breaker panel that distributes electricity to the house.

So if you had a PV system installed at home: depending on the size of your system, its type (whether it had battery storage or not) and the amount of direct sunlight available at the location, your entire electricity needs could well be supplied from the sun!

This sounds great; so the question is, again (this question will be coming up a lot on this blog): why isn’t more of this renewable energy technology being used in the Caribbean?

There are two basic problems: the first is that the technology is expensive. A PV system of 2.4 peak kilowatts (kWp) capacity, enough to power my own two-occupant home in St Vincent (my electricity demand is pretty low – did I mention I’m an energy efficiency consultant?) could cost up to US$15,000 installed. On the other hand, electricity in these parts is also expensive and we’ve got great sunshine, so I would expect my system to pay for itself in 7 to 10 years or so. After that, I would be making my own electricity – for free.

Essentially, PV works out well on an individual scale, once the matter of the up-front cost can be sorted out. But in the Caribbean, there’s another issue: the utility connection. The best way to use PV is as a grid-connected system. This means that your PV system is connected to the electricity company’s system, so that whenever your system is not producing enough electricity for your needs, the difference comes from the electricity company. At those times when your system is producing more electricity than you need (eg: when it’s a bright sunny day and no one’s at home), the extra energy will actually go into the electricity grid and be used by someone else. You pay for any electricity you use from the grid and the electric company pays you for any electricity your system supplies to the grid. This grid connection and payment arrangement, called “net-metering”, is a well-established practice worldwide.

The problem is that electric utilities generally will not encourage this sort of thing on their own initiative, so what is needed are government policies that encourage customers to invest in PV and laws that require the utilities to work with customers that want to go green. This is exactly what happens in the countries with significant PV use, and what is not happening in the Caribbean – with a couple of exceptions.

Two of the bright spots are found in Grenada and the US Virgin Islands. The utilities in these countries have taken a progressive approach to the matter and as a result the numbers of grid-connected systems are growing nicely (I’ll try to get some actual numbers on this for a future post).

So, the bottom line is there’s no mystery here. PV is not some esoteric, experimental technology that’s not ready for real-world use. It is a well-established (and rapidly-growing) renewable energy technology, in use all over the world, even in not-so-sunny places as Germany and Japan, two of the world’s biggest PV users. We need to use more of it. To do this we need creative ways of dealing with the up-front costs of PV for prospective customers, and we need government policies and net-metering laws, directed at getting the utilities on board.

Meanwhile, PV prices are falling, and sun is shining!

You can find lots of detailed information on PV here