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OAXACA

Rancho Los Cazahuates – Renewable Resource Case Study
by Dan Ellsworth

OAXACA WIKI
MEXICO FORUM

PHOTO GALLERY: Energy

For a transplanted Alaskan, the abundant sunshine of Oaxaca during the winter months is a gift. Coming from a place where the sunlight briefly crests the horizon for four hours before subsiding to the arctic cold, the 10-hour solar days of Oaxaca fueled my imagination.

Researching the availability of solar energy products I discovered that for all the hype of the last few years they were just not available in southern Mexico. Those that were commanded prices 200 to 300 percent more than the equivalents in the United States.

Although not an expert, I could see that a number of installations are poorly designed. I obtained some used solar panels from one place that was so badly designed the components were destroyed by an "expert" who rewired the system. The homeowner had given up and installed a "pole" from the electric company – an option most campesinos and other poor folks don't have available to them.

Three years later another project he was asked to look at – setting up a PV system for remote tourist cabins – was designed to maximize the income for the company in Monterrey that sold it to them. For the cost of a mere $100 dollars the system would have served four cabins rather than two and saved an additional $600 on a project with a budget of $3500.

The components from the company were 300% above retail cost and to serve the other cabins would run thousands of dollars more. To add insult to injury the installation of the single panel for each cabin was under shade trees and everyone ignored the fact that a 10-inch water pipe descending from the mountains above to supply villages below would have provided enough turbine energy for the entire small village.

RANCHO LOS CAZAHUATES

The Rancho Los Cazahuates project – started three years ago is a work in progress – like most homebuilt operations.

The location is on the opposite side of the Pan-American Highway from the village of San Francisco Lachigolo two kilometers from the nearest transmission pole. It started with the used solar panels cited above and was augmented with a pickup truck load of other components from the United States. Buying, importing and then reselling the pickup paid for the cost of transportation.

The project is not entirely about PV systems but is more about blending new and old technology with the environment to utilize readily available resources and to save and extend expensive ones. The physical property is a ridge of rocky land with copal and morning glory (cazahuates) trees and cacti that locals are happy to be rid of since it was not viable farmland. This ridge is used to great advantage for the water distribution system and the views are wonderful.

The buildings consist of two 5-meter square adobe cabins and two palapa style structures. All these structures are designed to provide cooling during the days. In the evening the one adobe cabin that is used for a dwelling releases heat into the room during the night that the adobe bricks have absorbed during the day – thus providing a constant living temperature. The second is used to store tools, batteries, and the usual PV support devices and provide a roof for the 960 watt, 24 volt system PV array built on a sun tracker and the telephone antennae.

One palapa is the "bathhouse" which has a laundry room on one side of a center wall, a shower and tub on the other side, and a compost toilet at the end. There are low adobe walls for the compost toilet but the entire structure has no outer walls to provide the ambient cooling so aptly done by these structures more common in the tropical regions. It is built into the side of the ridge which provides a handy "haul out" access for the compost compartments. This ridge also services as a handy built in niche for the solar hot water heater that is just above the bathhouse. Further above that hot water heater is a 25,000 liter cement tank that provides all the water for human consumption.

The solar hot water heater is simply three 4-feet square by 6-inch deep welded stainless steel sheets painted black that are interconnected with copper pipe. It is all built into a stone frame with hinged glass panels.

Below the bathhouse about 30 meters is another palapa which services as a kitchen and dining room and well below that at the bottom of the ridge is a grey water collection system that filters the water from everything above and stores it in a 40,000 liter cistern. Vegetable waste goes into a compost box in a chicken coop where a few chickens are busily working daily to produce soil for the small vegetable garden. Much of the cooking is done using two solar ovens.

The bottom grey water cistern has a solar water pump driven by two 75 watt panels mounted on a solar tracker installed immediately above. During available solar hours the water is slowly pumped to a small 2,500 liter holding tank at the very highest point of the ridge. The holding tank has a float cutoff switch that is tied into a pump control panel. Also in the pump control panel is a water low sensor switch for when the tank is out of water.

Pipes distributed about the hillside descend from the holding tank to various standing spigots that are used for irrigation, making adobe, making cement, and other non human consumptive purposes. After the grey water system was completed the 25,000 liter tank went from being filled every month to about every six months.

During the dry season the 40,000 liter grey water system gets augmented by purchased water from water trucks – depending upon the amount of construction being done. During the wet season the grey water tank is filled by rain water catchments system built into stone runoffs around the kitchen palapa. Because the catchments system is built into the ground rather than into the roof it also captures water filtering down a system of stone pathways from the hillside above.

A final touch is a well that produces water during the rainy season but dries up later in the year – between November and February depending upon the quantity of rain during the wet season. This well also has a solar pump, a single panel, a control box and the associated dry well and tank full switches but this tank is the 25,000 liter tank used for human consumption.

A recent laboratory test pegged the grey water bacteria count at 1800 parts per million and the well water within 1,000 parts per million which classifies it as safe for human consumption.

In synopsis the above described system was homebuilt entirely constructed by knowledge gleaned from mostly internet sources and U.S. alternative energy companies. Trial and error was the biggest teacher and the system has plenty of room for improvement.

LOCAL OPTIONS

Alternative energy is not rocket science and the mostly simple components can be put together by anyone willing to spend a bit of time and energy getting their hands dirty. The buildings were all constructed with age-old knowledge of local people with the addition of plumbing and electrical systems using current technology.

The next projects are the construction of a more "normal" house utilizing the same techniques, creating garden terraced beds with drip water technology, creating worm soil, expanding the tree planting efforts with more local varieties, building a straw bale workshop and storage facility, and finally three or four small cabins with a large open workshop for groups to use the facility for advancing their own inspirations. Experimentation is just starting on creating solar panels from scratch from purchased cells and another project is to create local produced solar trackers.

Getting acquainted with renewable resource technologies has inspired other ideas. One is to set up a small system in the northern Sierra. Solar energy is viable in the extended Oaxaca valley but is questionable in the cloudy high mountains. At the very minimum this project could document over a multiyear period the actual solar power possibilities for the Sierra.

Wind tracking is another renewable resource that is under-utilized. It would be interesting to set up a non-profit oversight group consisting of local people, not for profit eco tourism and alternative energy groups, an alternative energy company, and a government agency tasked with developing energy access to individual villages and local farmers. This group would be available to anyone and would be mandatory for projects developed with government funding. Also of interest would be a demonstration site for solar well pumping and drip systems for local farmers.

AUTHOR

Daniel Ellsworth is a software developer who decided to create a resource project to see how existing technology could be used to improve life in the poor southern state. Daniel can be reached via email.