Rancho Los Cazahuates Renewable Resource Case Study
by Dan Ellsworth
Publication date: 2005
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
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
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.
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.
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