Heating water, drying fruit, illuminating a light bulb and even baking a cake are among feats performed entirely by the sun at the Universidad Nacional (UNA) solar energy lab. At the university’s annual Sun Day – held May 4 and 5 at its campus in Heredia, north of San José – scientists opened up the lab to the public to promote the use of this clean, renewable and inexpensive form of energy.
The open field outside UNA’s physics department houses the lab’s variety of solar energy equipment. A solar-powered oven absorbs sunlight with a black tarp and conducts heat with aluminum and copper wires (TT, Aug. 26, 2005). This heat then stays trapped between two glass panels and reaches up to 170 degrees Celsius, explained the lab’s director Shyam S. Nandwani.
Besides the oven, a water distiller heats water between similar glass panels. As the sun heats the water, it turns to vapor, causing minerals to separate and settle to the bottom and distilled water to collect in a separate container.
Nearby, a solar-powered fruit dehydrator uses large aluminum sheets to collect and transmit heat, shriveling bananas in a bed of sunlight.
Though UNA scientists research and develop this equipment, they don’t sell it, explained Nandwani, who is originally from India and has been in Costa Rica 27 years. “We promote solar energy by putting people in contact with businesses,” Nandwani said.
Along with a list of distributors who sell solar-energy equipment, UNA can provide do-it-yourself manuals for the ambitious (or those who wish to hire a carpenter) to build their own solar-powered ovens, fruit dehydrators and water heaters.
By far the lab’s most impressive example of the sun’s capacity is a small house that runs completely on solar power. Outside the house are 12 solar panels that collect the sun’s energy in its direct current (DC) form and store it in batteries. A converter then transforms this energy into its useable adaptable current (AC) form, which powers the house’s lights, refrigerator, coffeemaker, microwave oven, TV and fan, all of which the lab’s staff enjoy during their lunch hours.
Despite this efficient system, running a house on solar power is “not magic,” Nandwani said. “You have to be aware of what you’re consuming and calculate how much energy you’re using to make sure the batteries don’t run out. If it’s raining for several days in a row, you need to plan to have more batteries available.”
The UNA staff writes down how much energy they consume each time they use one of the house’s appliances.
Owning and running a solar-powered house like this one is not for everyone, but it may be a good option for those living in remote areas, such as parts of the Southern Zone’s Osa Peninsula, where the power lines of the Costa Rican Electricity Institute (ICE) do not reach, Nandwani explained.
The number of solar panels required to run a house depends on its size and how much its inhabitants consume, he said. One two-square-meter panel can power four light bulbs, an energy-efficient refrigerator and a television, and costs ¢400,000-¢500,000 ($790-$988).
Urban homeowners can benefit more from a hybrid system of traditional, ICE provided electricity and relying on energy from solar panels only for low-consumption appliances, Nandwani said. Switching to a solar-powered water heater is another feasible option for those near cities.
For more information about solar energy, call the Universidad Nacional solar energy lab at 277-3482 or 277-3345 or visit www.una.ac.cr/fisica/energiasolar.htm.