This article is in response to the Saba Electric Company (SEC) statement printed in The Daily Herald of Monday, March 9-2-015.
The main theme of the article concerns the consideration to attempt to use Solar Photovoltaic Panels (SPP) in order to generate electrical power using direct sunlight.
At issue is the last part of the article that states ”….the proposal for wind turbine generation of electrical energy never saw the light of day.” This statement is completely false as the proposal was available to Saba, then GEBE, from 1999 to 2004. Five years is a lot of daylight.
The reasons given are also false. The towers were engineered to withstand 200 mph. The land available was sufficiently large to accommodate the whole project including the state of the art engine house and battery bank contained in the revised proposal requested in 2003.
The proposal was terminated when the management of GEBE St. Maarten said, that they had no items in dispute, but had been requested to “go slow” on the wind. The then Saba Government did not want electrical generation by wind, but did not wish to say so in public.
Development of wind turbines has now enhanced their capability to withstand high wind conditions with the fully featherable and variable pitch vanes producing no torque force on hub or tower.
The personnel, who are said to manage SEC on a day to day basis, have enough talent to know when a wrong direction is indicated and, if left to common sense, could solve this alternative energy problem. It is when they get bad directions from above, then bad results are in store for population of Saba.
It is agreed that alternative energy should be found, but NOT the wrong one.
Now let us consider photovoltaic panel or panels coupled to give a desired output. The panels should be located with the greatest exposure to the arc east to west, close to 180 degrees and tilted to be at 90 degrees to the sun’s daily route. These factors are of great importance in allowing the panels to produce their full rating according to the bell curve provided by the manufacturer.
SPP’s come in many grades depending on the materials used and the construction method. Efficiencies of up to 40% have been reported in the lab under ideal conditions. But industrially manufactured panels usually are rated at 10-15% efficiency. The panels must be installed in such a way that they are secured from uplift in high winds and they need protection of their receiving surface from being damaged by debris under those conditions.
SEC has stated its objective is to generate one megawatt by direct sunlight. This would require 4000 panels. They also stated that the tracking system used to keep all panels in focus for maximum output is impractical due to the cost and the conditions on Saba. It is also impractical to protect the panels during hurricane conditions due to cost and manpower calculations.
No mention has been made of the amount of cloud the island is subject to, nor, that for approximately three months of the year, the sun is to the north of the island.
Hence for rigid fix panels, subject to the above conditions daylight produce would be expected to be no more than one third.
These operational conditions can only be expected if a system is misapplied in an unsuitable location. This is why it was not proposed in 1999 when the change to alternative generation first came up.
The challenge to take the above described negatives and turn it into an economically viable working system such that SEC could show a positive profit on investment are not obvious. Hence the relief in costs to Saba residents could well be far away.
This proposal may be so misapplied in an unsuitable location that this is an engineering impossibility
For further reference on SPP:
Dresselhaus & Thoma, Nature 414 P333-337 & Nature 4454 p802
Lewis, Science 315 p89-801