Harnessing the sun at the Brac High School

Year 8 student Kodie Scott and the school’s
aquaculture system.

Cayman Brac High School students Joshua Baker (left)
and Kodie Scott feed the Tilapia fish in the fish farm.

Science teacher Clive Baker is showing members of
the Brac High School Agriculture Club how to harness
the sun’s energy to prepare them for tomorrow’s
world.

By Nicky Watson

Friday,  June  17, 2005

The core of the whole agriculture project at the Cayman Brac High School (CBHS) and a focus of the science curriculum is sustainability. And so, the school’s highly successful Agriculture Club branched out this school year into alternative energy, and learned the capabilities and limitations of solar generated power.

“As highlighted in the recent conference on Grand Cayman on sustainability, we cannot, as a planet, maintain the present use of our resources. As a consequence, we need to educate the next generation to be less wasteful,” CBHS Head of Science Clive Baker told Cayman Net News.

Mr Baker explained that, in the production of solar energy, solar cells, otherwise known as photovoltaic or photoelectric cells, convert light directly into electricity.

Solar cells are made of special materials called semiconductors (silicon is currently the most commonly used). When light strikes the cell, a certain portion of it is absorbed within the semiconductor material. This means that the energy of the absorbed light is transferred to the semiconductor.
The energy knocks electrons loose, allowing them to flow freely. Solar cells also all have one or more electric fields that act to force electrons freed by light absorption to flow in a certain direction. This flow of electrons is a current, and by placing metal contacts on the top and bottom of the cell, we can draw that current off to use externally.

Solar generated power was originally developed in order to provide electricity for satellites, but has now become commonplace, especially with the proliferation of calculators powered by solar cells.

Now the school club has set out to demonstrate how this technology can be incorporated into traditional farming, and for the past five months, 18-volt solar panels have been used to power the pumps for the hydroponics and aquaculture programmes – at least during the day.

The CBHS Agriculture Club started with a few grow-boxes in 1999, and has steadily expanded each year since then, with practical and financial assistance from the Department of Agriculture and the local community.

In 2000, the club started growing crops using a hydroponics system supplied by DoA. Hydroponics is a method of growing plants without soil, in which the roots of the plants are fed with a nutrient rich solution.

This proved very successful for the young farmers at the school, as demonstrated by a string of ribbons and awards from that year’s Agriculture Show on Grand Cayman.

Progressing from a hydroponics kit, the Club followed this with the construction of a do-it-yourself hydroponics system from material bought at the local hardware store on Cayman Brac.

“The entire set-up cost less than $100 and was done to convince local people that a hydroponics system was an economically viable option,” explained Mr. Baker.

Aquaculture was the next main extension of the Club, and members successfully began to raise Tilapia fish, again with the assistance of the Agriculture Department, which supplied the fingerlings and the feed.

The solar panels now used to run these projects charge deep cycle truck batteries. These can withstand discharging and recharging more than a normal battery. At night, the system is currently switched back to mains electricity, because the panels would discharge the battery.

“However, some of the students, notably Year 11 student Alexander Randall, are building a control box to stop the reverse flow and smooth the charge,” said Mr Baker.

Incorporating technology into their projects has always been an intrinsic part of the Club. Digital testing and recording of the quality of the nutrient solution (data logging) has been used extensively from the start, and Club members regularly download the information for analysis, said Mr. Baker.
The Club needed a cheap and effective method of obtaining fresh water, and so this year, they also invested in a reverse osmosis filter, which can produce 100-gallons per day of desalinated water from well water.

“The solar project has been very successful. Even when it’s cloudy, the panels are getting enough charge to run the system during the day. So this means that, with the addition of the control box, the garden and fish farm will be independent of the main grid,” said Mr Baker.

“It is also a demonstration of the valid use of sustainable solar power. There has been lots of interest by local people, particularly those with land on the Bluff where mains electricity is not available, who need to run pumps for irrigation,” he added.

According to Mr Baker, the solar panels are not that expensive. The panels they are using were generously donated by the Agriculture Department which showed its customary support of their agriculture and aquaculture projects, he said.

The panels they use are very low wattage, and can be purchased for between US$150 to US$200, or even less second hand. High powered panels that can generate 100 to 150 watts cost around $600 to $700, he said.

The most expensive part of their power set up is the battery, but this should last a long time. The system has no maintenance costs and can easily be used for off the grid, low wattage use, such as lights, television, and radio.

For larger power needs, such as air conditioning, hairdryer, stoves, mains power would be required, said Mr Baker, but he noted that technology is improving all the time and that this might change.

“With the spiraling cost of fuel and consequently the spiraling cost of electricity, the generation of tomorrow needs to be open to consideration of cleaner, sustainable, and ultimately cheaper forms of electrical generation,” explained Mr Baker.

He pointed out that, as with all things, students learn more effectively by getting practical experience of what they are taught in class, and they need to know the advantages and disadvantages of various forms of alternative energy.

“For example, from our use of solar energy in the garden and fish farm, they have learned that it is clean, effective and non-polluting, but is limited in its power out-put.”

The next major plan for the CBHS Agriculture Club is to build a windmill at the school, a form of energy used to pump water for irrigating crops for more than 4,000 years, and harnessed to sail boats for very much longer.

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