Green Energy Options in the Caribbean

Geothermal

Earth heat bases on the 9000° F inner Earth temperature and gradually reduces in temperature closer to the surfaces, but the temperature close to the surface varies greatly. Rainwater that sips in deeper parts of the earth gets hot and is called a geothermal source.

In some parts of the world this water finds its way back to the surface via cracks and faults, such as geysers (i.e. in Iceland) and hot springs. As with solar energy, the issue is how to tap that virtually unlimited source of green energy.

In most cases the trick is to drill to find and get access to the geothermal source. The hot water can than be used both direct and in geothermal power plants, which consists in three varieties. Steam can be used to generate electricity with a dry steam generator.

Water between 300-700°F can be used in a Flash Power Plant, where hot water is flashed into steam. Water with a temperature as low as 220°F can be used in a Binary Power Plant, where the hot water indirectly produces steam from a fluid with a lower boiling point using heat exchangers. The used water is fed back into the source for reheating. It is renewable in a sense, as the available heat capacity has its limits.

Currently, the worldwide capacity of geothermal power plants is over 9,000 MW. The energy cost of “easy access” geothermal energy power plants is comparable to wind energy. An MIT study showed that it is feasible to increase the capacity in the U.S. alone to at least 100,000 MW, requiring an investment of up to $1 Billion.

In the Caribbean the Lesser Eastern Antilles are known to have potential for geothermal energy. Guadeloupe has a 4 MW plant from shallow high temperature wells since 1984. Explorations have shown encouraging results in Dominica, Montserrat and St. Lucia, but no further initiatives have been taken yet.

Tidal Energy

If there is one thing we can safely predict and be sure of on this planet, it is the coming and going of the tide. While the energy capacity is reliable, converting it into electrical power is not easy. One option is to build a “tidal barrage” (compare to hydro lakes) which is not only complicated but also cause drastic changes to the currents in the estuary that could have huge effects on the ecosystem. Nevertheless, tidal barrages have a huge potential, worth while further exploration.

Another option is to use offshore turbines that work comparable to wind parks, but underwater and using the tides as a source. This technology brings no ecological issues, but as it is in an early stage, the cost is not yet competitive (like wind energy in the early days). Once cost gets competitive it offers a huge potential and can be applied anywhere where the tides are suitable, which includes the Caribbean.

Bio-Mass Energy

Wood used to be our main fuel, utilized to heat and cook. Wood still provides some of the energy we use, but its importance as an energy source is dwindling. Sugar cane can be fermented to make alcohol, which can be burned to generate power.

Alternatively, the cane can be crushed and the pulp (bagass) can be burned, to make steam to drive turbines. Other solid waste products can be converted into steam for a power plant as well.

The bioconversion process uses plant and animal wastes to produce fuels such as methanol, natural gas, and oil. Manure, corn stalks, wood chips, seaweed and other waste products can be used. A disadvantage is that burning causes greenhouse gases.

Conclusions

On a worldwide basis, green energy is a viable option, both on the short and long term, but requiring investments to achieve a substantial contribution. In the Caribbean, the options are essentially the same, but practically wind and solar energy are the most promising short term solutions.

Economically, wind energy has the best options at this time, with solar as the runner-up. A proven and widely spread economical model is where owners of windmills sell the excess energy to the electricity company at a price below their fuel cost. Once electricity companies in the Caribbean pick up this concept, major savings for both them and the owners of the windmills will apply.

James Post is a passionate advocate for green energy. He is also the owner of Paradise Bay Resort in Grenada, which opened in April 2007 and installed a windmill to generate better than a zero carbon footprint.