Category:Parras Solar Hot Water
 Solar hot water systems in other locales
In may parts of the world, solar hot water systems are affordable and useful, for example in Israel and Greece. Even in the United State 1 in 50 homes has some sort of solar collector on the roof (Bull and Hazeltine 242). In Colombia, the Gaviotas Foundation installed many rooftop solar hot water systems on new apartment buildings and other structures (Wiesman).
 Solar hot water systems in Parras
There are three rooftop solar systems in Parras:
 Current water heating methods in Parras
Currently, most families heat their water using gas-fired water heaters. There is evidently some concern about the cost of gas, as many families use the hot water heater as part of a manual on-demand system, where they light the heater only immediately before it is needed. At Zaragoza #1, people already make use of solar radiation to heat their water. Señora Rosa Guadalupe Vinelna said that it is not necessary to turn on the gas hot water heater during the day. This could be because it retains heat, or because of solar radiation the outdoor water heater tank absorbs, or a combination of both.
An appropriate solar hot water implementation must be affordable enough for households to justify its cost on the basis of energy savings. See Effectiveness of Home Solar System for an evaluation of the Zaragoza system.
 Potential for solar hot water heating systems in Parras
 Year-round weather in Parras
Parras is a high desert oasis town in northern Mexico. The abundance of water combined with year-round sun exposure makes Parras an ideal location for solar hot water heating implementations
 July 9 2006 - materials heating performance comparison
This test was to determine which pipe materials and sizes absorb sunlight energy and transfer heat to water most effectively.
- mostly sunny
- Beginning ambient temperature
- 36° Celsius
- Ending ambient temperature
- 35° Celsius
 Test results table
|Material||Start time||End time||Time elapsed||Starting water temp (Celsius)||Ending water temp (Celsius)|
|1/2" Copper||1:00 PM||2:15 PM||1 hr 15 mins||30°||60°|
|3/4" Copper||1:00 PM||2:15 PM||1 hr 15 mins||30°||60.5°|
|1/2" Copper painted black||1:00 PM||2:15 PM||1 hr 15 mins||30°||61°|
|1/2" Black Plastic||1:00 PM||2:15 PM||1 hr 15 mins||30°||59°|
|1/2" Steel||1:30 PM||2:15 PM||45 mins||30°||57°|
|1/2" Steel painted black||1:00 PM||2:15 PM||1 hr 15 mins||30°||63°|
 16 July 2006 - time-based performance testing of black painted half inch copper
A half-meter length of half-inch black-painted copper pipe was filled with 30° water. The two ends of the pipe were sealed with duct tape. A multimeter with a thermocouple was insterted under the tape on one end of the pipe, allowing temperature measurements to be taken every minute. Weather conditions were full sun with an ambient temperature of 37°.
 Test results table
|Clock time||Minutes elapsed||Temperature (Celsius)|
 Graph of time versus temperature
The first two data points are not represented in the graph, and were not used to find the logarythmic model equation.
The Excel-generated logarythmic equation to describe this graph is: 10.058Ln(x) + 23.045. Again, the first two ungraphed data points, for 11:54 and 11:55, were not considered in generating this equation.
This information was converted to wikitext from Excel with the help of csv2wp.
Dear "Friends of Gaviotas,"
I am emailing from Parras, Coahuila Mexico where I am participating in a. For one of our more theoretical classes, we are reading and discussing the book Gaviotas by Alan Weisman [ISBN 0123351901]. In our other projects class, I am working with a group that is testing and refining some existing solar hot water heating systems developed in our program last year, and designing a new system to heat the water in a local hotel pool. After reading that Gaviotas engineers were able to oxidize copper to get an ultra-light absorbent black surface, we become curious if we, or others, could do something similar. In addition to using such a technique ourselves, we will also be writing a report on our efforts which will be put up at appropedia.org. This is intended to provide others with the tools to implement their own appropriate technology projects.
I have quoted one of the sections from Gaviotas which discusses the oxidation process used to blacken the copper pipe.
- "Then they learned about the British silica film with the ultra-black oxidized layer and ultra-high price tag. An hour at the London factory told them what they needed to know. Back in Colombia, Alfoso stripped a copper sheet clean in a bath of nitric acid, rinsed it, then violently oxidized it by dipping it into a solution of copper sulfate dissolved in sulfuric and hydrochloric acids. The result was a texture dense and velvety as a butterfly's wing, and black as fear itself. Since the oxidation was deposited directly on the copper without an intervening layer of film, it was, as Alonso had predicted, even more efficient than the British version. They tested it for a typical week of dank Bogotá weather; it was as though the warmest, most inviting place in town was their shower." (page 100 from the paperback version of Gaviotas)
Thank you for your time. We eagerly await your reply.
 Spanish-English glossary
- heat exchange
- intercambia de calor
- tubo, or pipa
- gas water heater
- Calentador de Agua
- water heater
- calentador de agua
- threading (on a pipe)
- flat roof
- Weisman, Alan. Gaviotas: A Village to Reinvent the World. Chelsea Green Publishing Company, 1999. [ISBN 1890132284]
- Bull, Chirstopher; Hazeltine, Barrett. Appropriate Technology. Academic Press; San Diego, 1999. [ISBN 0123351901]
"La termotransterencia." Curso sobre Instalaciones de Energia Solar Termica. 
"Water Heater Efficiency" 
"Energy From Natural Gas"