Thursday, December 22, 2011

Gaviotas Engineering

"Development means making people happy. Before you spend your money on roads and factories, you should first be sure that those are what your citizens really need." -Father Francis Lebret

Gaviotas engineers have been designing implements of sustainable technology for many years. They refuse to patent their inventions, believing that the importance of making sustainable technology available far exceeds the temptation of profit. The sleeve pump, solar kitchen, and solar kettle comprise only three examples of their collective ingenuity.

Water Technology
"Civilization has been a permanent dialogue between human beings and water." -Paolo Lugari

Sleeve Pumps
From soil studies undertaken the year after he founded Gaviotas, Lugari had learned that the region of the llanos was like a gigantic mattress suspended above a huge underground reservoir of clean, sand-filtered runoff water from the Andes. Nevertheless, eighty percent of the maladies suffered by llaneros and local indígenas were caused by water contamination near the surface. The first important task was to get at the pure water below.

Alonso Gutiérrez, one of the mechanical engineers at Gaviotas, found the solution when he was thinking about the inherent problems of piston-driven water pumps. One problem, for example, was the seal created by the water against the sides of the sleeve. To move a piston in a piston-driven water pump in order to make the enclosed water rise, you spent energy lifting it against the pressure of that seal, as well as against the weight of both the water and of the rod and piston. Instead of wasting energy by lifting a heavy piston, why not leave the piston in place within a lightweight plastic sleeve, and lift the sleeve instead? During the dry season the water table in the llanos usually dropped below the limit of conventional hand pumps, leaving disease-ridden surface streams as the only water source. But because Gutiérrez's sleeve pump didn't require applying force against atmospheric pressure, he was certain that it could pump water from a much deeper well. The sleeve would be so light that even a small child could work the pump.

When Luis Robles, another engineer, was explaining the concept of a pump handle to some children at the Gaviotas school, one of them observed that it was similar to half a seesaw. Robles then built a seesaw and attached it to a sleeve pump outside the kindergarten so that when children played on the seesaw, they also pumped water for the school. In the late 1980s, Gaviotans brought their sleeve pumps and other appropriate technology to more than 600 villages as part of the Colombian government's Agua Para Todos (Water for Everyone) program.
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Solar Energy
"With more people using more oil than ever, [petroleum] won't last forever. . . . Not everyone can afford an oil well: they're in just a few places. But everyone has a sunshine well. Someday they'll have to go to it." - Mario Calderón

Solar Kitchen
During the 1980s, Gaviotas designed and built a new hospital to serve Gaviotans and people in surrounding villages. They used solar technology and adapted various techniques in order to make the hospital energy- and self-sufficient. The engineers decided to circulate solar-heated, low-viscosity cottonseed oil around the pressure cookers in the kitchen because oil presented fewer problems than water in maintaining the necessary high temperatures.
As sunlight super-heated the oil, a heat siphon sucked it into a holding tank. At the flip of a toggle switch, a forty-watt micro-pump, run on batteries charged by photovoltaic cells, forced the hot cottonseed oil through coils that looped around six stainless-steel pressure cookers, then back up to the roof to re-heat. Insulation in the roof-top oil tank kept the closed system hot enough to operate twenty-four hours a day, and there was adequate charge left in the battery bank to illuminate the hospital all night with compact fluorescent bulbs, designed to operate on twelve-volt direct current.
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Solar Kettle
Gaviotas engineers also designed a solar kettle for the hospital. According to engineer Jaime Dávila, "the principle begins with an old country custom: boil water one day to drink the next, after it cools." 

Dávila's goal was an inexpensive solar-operated system that would give unlimited boiled drinking water, already cooled to room temperature, straight from a tap any time of day. Furthermore, the device had to work under cloudy skies. Using an oxidized copper formula already developed, Gaviotas solar collectors already heated water to 120 degrees Fahrenheit under diffused light. Increasing their normal operating temperature just 10 percent would eliminate many unwanted microbes. From there, the Gaviotas engineers calculated that they would need to raise the water to full boiling temperature for at least two minutes to kill all pathogens.

They accomplished this with a very efficient heat exchanger. As untreated water was pumped into the solar panel, it traveled through one chamber of a double copper pipe. At the same time, water that was already boiled was flowing in the opposite direction through the pipe's other chamber, toward a reservoir tank connected to the tap. When the hot and cold water passed each other with just a thin copper membrane between them, the boiled water cooled down and the "raw" water warmed up—the heat exchange. Once inside the solar panel, the untreated—but now preheated—water's temperature rose quickly; from there, it only needed a little push from direct sunlight to boil. Whenever a burst of sunshine brought the temperature to boiling, pressure forced the steam that formed through a one-way valve into an upper tank. From there, it condensed back into water, which flowed down through the heat exchanger to the faucet tap. Using a one-meter-square solar collector as its heat source, the kettle needed only one minute of direct sunlight to make water start to boil and pass through the one-way heat valve. Because the upper tank couldn't fill unless direct sunlight actually pushed purified water vapor through the valve, any water reaching the tap was always trustworthy. The storage capacity was great enough that, even allowing for days when the sun never broke through, the kettle delivered about eight gallons daily of pure drinking water—more than enough for an average family—only two degrees warmer than when it left the ground.
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from: Weisman, Alan. Gaviotas: A Village to Reinvent the World. White River Junction, Vermont: Chelsea Green Publishing, 1998.


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