Appropriate Technology

Appropriate technology, glossary article
Sustainable Civilization: From the Grass Roots Up
Appropriate Technology Appendix - 2 - 3
Technology is the total collection of tools and knowledge used by a population to alter aspects of the environment to meet human desires. Technology must be appropriate for the location, the capabilities of the population, and the available resources. Building a waterwheel in the sands of a desert would be useless, as would handing control of a nuclear reaction to some remote un-educated tribe, or giving the tribe gasoline fueled pumps. 
The U.S. patent office estimates 1 patentable invention per year, per every 1,000 people in the population. But don't let statistics mislead you into believing that mere number of people will mean progress. Knowledge and technology tend to feed back into each other toward more complex systems.
It takes creative people, educated and with extra time and resources for significant advances. It takes easy access to previous knowledge, tools, expert assistance, etc. An information and goods exchange among a network of communities should be expected to yield far more new inventions each year than the same communities in isolation. Communication and trade must be maintained, which in a low energy environment probably means being physically nearby.
Not every invention is in the best interest of civilization (think of a device that could destroy every living thing, so simple to make any kid could do it...) Even without posing a physical threat, inventions are not necessarily welcomed with open arms. There are always those who oppose anything new. With innovation the demand for a product or service may wane (buggies and horsewhips after the auto). 
Not every site has the same resources. Not every group of people has the same capabilities or interests. Specialization nurtures expertise. Trade nurtures specialization. But it also nurtures the "theft" of inventions, reducing the reward for the inventor’s efforts, and encouraging the natural protection of an invention, secrecy. 
We need an environment that nurtures positive creativity, avoiding careless waste of resources, contamination of the environment, and unacceptable risks. Thoughts?
INTRODUCTION
Can you obtain and manage sufficient water to not only sustain your present direct use, but also provide for a subsistence garden, or more? What else would make your life "better"? This appendix presents simple concepts useful to sustain a higher standard of living in the absence of our present high energy globally connected infrastructure.
The definition of appropriate technology readily changes with your local situation. P/V modules are great for the desert, but of questionable vale in an area of constant overcast or precipitation. What it is NOT is designed in weaknesses such as easy to wear out parts or construction of poor quality materials. 
It must be something that can be understood, maintained, repaired or replaced locally, or something where such can be obtained from elsewhere by assured sustainable trade.
It is that which is available, affordable, and sustainable in the most likely situations. 
It needs to be designed with recycling in mind. This consideration is something that has been essentially ignored in our century+ long oil party.
Individual invention needs to be integrated into a larger view throughout the relevant organizations with readily available communication, to avoid the situation where numbers of people are over and over "reinventing the wheel".
In smaller communities technology might degrade to the extent that it is mere handicraft of some naturally grown object. 
SUGGESTED SOURCES
Numerous articles on creating your own "home grown" technology are available online at http://www.vita.org and at http://www.itdg.org. When the functional lifespan of your purchases ends, will you still have a need for the product or service? If so, can you repair or replace it with what you have remaining? The greatest source of energy on Earth, is the sun. It evaporates water for rain, powers worldwide thermal currents in the air and water, and thru photosynthesis provides all of the food consumed.
TECHNOLOGY PLANNING
If solar panels have a useful life of 20 to 30 years, and I anticipate a continuing need for electrical power, I have that long to find an alternative. Silicon cells are a high tech process. Low tech p/v cells can however be made from blackened copper, and thermocouples also offer direct sunlight (heat) to electrical power conversion.
The turn of the millennium technology and infrastructure is dependent on fossil fuels for power and feedstock. Potentially during the lifespan of the young of today, any significant use of fossil fuels will end. 
TOOLS
With a modest collection of quality hand tools, even a neophyte can make modest repairs, disassemble obsolete equipment, or fashion vital devices. Imagine trying to "double dig" your garden without a shovel, or loosen a bolt without a wrench. Obsolete devices are a potential "goldmine" of parts and raw materials.
AIR TECHNOLOGY 
Choking smoke or dust, too much , too little O2, biological threats, poisonous gas, or other toxic or dangerous substances. You could easily find you need to at least temporarily seal yourself inside a bubble of clean air. 
 filtration: Appropriate technology engineering example of a homemade re-breathing device. Two liter soda bottle of , which should absorb 2.1 qt of . This is roughly 10% of what a person exhales in an hour, or 6 minutes. To avoid going below 15% O2, this unit needs to start with about 1.2 cubic ft. (8.98 gallon) of air. I could easily envision a backpack with two 2 liter bottles of water, and a plastic bag of 2.4 cubic feet (around 18" wide, 24" high, and 10" thick), to provide an expedient 12 minute supply of self-contained air.
On a larger scale if you wanted to absorb the for a person for the entire day it would take around 480 liter (about 127 gallon). Circulate this water in a "waterfall" such that a full day of in home circulation is run the next day in the greenhouse area.
 biological exchange. Studies have shown that essentially equal photosynthesis takes place in 5 grams of plant mass distributed in a square meter of open water, and in 10 kilograms of plant mass in a square meter of forest e3nvironment. A clear implication is that while plants growing in "air" provide a larger standing mass, aquatic plants are a greater source of oxygen regeneration. (Draw your own conclusions about damage we're causing to the ocean's ecosystem.)
NASA studies indicate that one cubic meter of actively growing wheat, grown hydroponically under 24hr/day light, can meet the oxygen needs for one person, while producing the food value of about 1/3 of a bowl of cereal per day. The NASA research conflicts though with the lower technology 2 year experience at "Biosphere II", where 3+ acres was not sufficient, when a relatively extensive soil biosystem was included in the container. (Microorganisms in the soil, and the concrete structure were found to be absorbing oxygen.)
Other experiments show that approximately 8 gallons of well aerated algae in sunlight balances the breathing of a typical human. (Remember, you need enough "extra" air volume to carry you past periods of dark/dim light.) If you're not bubbling the air thru the algae, set up a "surface area" of water for the 8 gallons at about 8 meters square. (A square about 9 feet on a side) Since the water alone weighs 64 lbs., if this is to be a portable unit, you'll want some type of cart.
Some plants such as cacti, aloe vera, etc. produce oxygen in the dark, vs the light.
COMPENSATING FOR ATMOSPHERIC PRESSURE VARIATION
An airtight home must have a flexible lung (see Biosphere II) to allow internal/external air pressure to remain equal, without actual exchange of air. It can be as simple as a large trash bag on one end of a pipe that penetrates a wall. Typical atmospheric pressure changes do to weather may amount to 2% to 5% of the volume of the sealed container. If you have a 1200 ft. sq. home (above), the "lung" should be between 168 and 420 cubic feet. (Don't panic, that's only a box 8 foot on each side max) The device must account not only for the pressure changes due to weather, but from heating and cooling of the air inside the sealed area.
ELIMINATING TOXIC GASES
Filtering thru biologically active soil removes significant contamination. Further processing thru sealed areas of selected plants, and activated charcoal. 
KILLING GERMS
Envision a device where all of the air being taken in must pass thru a relatively small opening. The device has a lens or mirror that will concentrate intense sunlight into the hole when the device is positioned aimed at the sun. This should cause a small very high temperature zone where the air must pass thru, killing germs. In that ultraviolet kills more readily, are there lenses that concentrate U/V?
KNOWLEDGE
Web and computer files are the fastest means of finding and gathering information, but rely on continued computer technology. Unfortunately for surviving humanity, the web may be an early victim of the collapse. Download to local storage any file you file valuable, and print all of those you find essential.
Microfiche is a means of storing a great deal of information in a small package, that can be read with a child's toy microscope
Books probably remain the most practical means of gathering, storing, and passing on knowledge. Your local library should be able to order for you on "interlibrary loan" virtually any book. Read, please! A potential sustainability library (with a lean toward a desert environment) is in the Bibliography Appendix. Used bookstores, several of which have online search functions, can yield may priceless "gems".
COOKING
Every day, the sun provides to virtually every square yard on earth more energy that a person needs to cook a meal, or heat water for pasteurization. There are many approaches to concentrating and using this energy. A relatively portable yet easy to construct is to form a reflector like a giant funnel, with a black cooking vessel at the bottom of the funnel. To build up the heat without letting the air cool it, contain the vessel in clear plastic or glass. 
A piece of flat cardboard (if you are going to glue shiny stuff onto it) or reflective substance about 2 feet wide by 4 feet long. (The length should be just twice the width. The bigger, the better.) 
At the middle of either long edge, cut a half circle out of the cardboard, along the bottom.
When the funnel is formed, this becomes a full-circle and should be wide enough to go around your cooking pot. 
For a cooking vessel, consider a canning jar. 
The cooking container should be black on the outside. Scrape off a vertical stripe so that you have a clear glass "window" to look into the vessel, to check the food or water for boiling. 
Set the cooking container on an insulator. Put a plastic bag around the cooking-jar and insulator to provide a green-house.
HEATING
Think Outside the Box - Strange Thought on Heating… An experiment I never got around to trying… use of a small propane powered fridge as a heater… A gas powered fridge is a heat pump. Say the fridge is framed into a south facing wall, and instead of the solid door it has glass. Inside the fridge are containers of water. The flame, while vented, is inside the home envelope, as is the coil that radiates heat. The cooling system trys to take heat out of the fridge, which ends up inside the house. Whatever the COE, it SEEMS logical that it is going to provide more heat than the flame alone could. In a more normal use, the fridge can be driven by any concentrated heat source, even focused sunlight. 
THERMAL STORAGE
Heat energy moves by conduction (hot objects touching each other), convection (physically moving flows of heated mass, water, air, etc.), or radiation (infrared light). Water stores, conducts, and convects heat well. An advantage of water for moving heat is that although it does convect, the density difference is not so great that a low power pump cannot move "hot" water to a physically lower position. 
Earth tubes are an approach combining conduction and potentially convection to provide not only ventilation for a structure, but storage / moderation of heat. The "traditional" approach is a grid of buried tubes, about 4' apart. Using air as the exchange medium, the tubes need to be at least 4" in diameter, and 60 feet long. Multiple tubes provide "extra" surface area to contact the earth, and exchange thermal energy. The volume of soil available for thermal storage is essentially limited by how deep you are willing to dig you trenches. (With lots of backfill of course.)
Heat energy moves by conduction (hot objects touching each other), convection (physically moving flows of heated mass, water, air, etc.), or radiation (infrared light). Water stores, conducts, and convects heat well. An advantage of water for moving heat is that although it does convect, the density difference is not so great that a low power pump cannot move "hot" water to a physically lower position.
We've only done this with a model solar home. In the model, the pump was powered by the amount of solar panels that would fit on a 3x5 index card. That water flow should be sufficient though for one actual heat exchanger tube.
On a real-life scale, say:
4" diameter outer tubes, open at the top, sealed at the bottom.
1" diameter inner tube, open at the top and bottom
Filled with water to the top.
Pump "X" only needs to move a trickle of water from top surface of outer to inner pipe. Due to volume difference, warm water moves down center pipe much faster than it returns up larger outer volume, warming the soil as would any other earth tube.
With a modest well-drill, suitable for a shallow hand-pump well, drill multiple holes say 20 to 30 feet deep, on a grid of about 4'. Put one of these water filled heat exchangers in each hole.
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WATER TECHNOLOGY
Water Collection from "Dry" Air. Before modern dehumidifiers, there were methods shown usefull in precipitating water from the air.
Dew ponds appear to predate history. They are large but shallow artificial pools, smooth rock to protect the water tight layer, with the entire pond insulated from the ground below and around. 
 
A pond described in Popular Science (September 1922 is a concrete cistern about 5 feet deep, with sloping concrete roof, above which is a protective fence of corrugated iron said to aid in collecting and condensing vapor on the roof and prevent evaporation by the wind. The floor of the cistern is flush with the ground, while sloping banks of earth around the sides lead up to the roof. Moisture draining into the reservoir from the low side of the roof maintains the roof at a lower temperature than the atmosphere, thus assuring continuous condensation. At one side of the reservoir is a concrete basin set in the ground. By means of a ball valve, this basin is automatically kept full of water drawn from the reservoir. 
 
In 1932, Achille Knapen built an "air well" in France. The structure was described in Popular Mechanics Magazine to be about 45 feet tall with walls 8 to 10 feet thick. The claim is the aerial well will yield 7,500 gallons of water per 900 square feet of condensation surface. 
 
At night, cold air pours down the central pipe and circulates through the core... By morning the whole inner mass is so thoroughly chilled that it will maintain its reduced temperature for a good part of the day. The well is now ready to function. Warm, moist outdoor air enters the central chamber, as the daytime temperature rises, through the upper ducts in the outer wall. It immediately strikes the chilled core, which is studded with rows of slates to increase the cooling surface. The air, chilled by the contact, gives up its moisture upon the slates. As it cools, it gets heavier and descends, finally leaving the chamber by way of the lower ducts. Meanwhile the moisture trickles from the slates and falls into a collecting basin at the bottom of the well.
The French inventor L. Chaptal built a small air well near Montpellier in 1929. The pyramidal concrete structure was 3 meters square and 2.5 meter in height (10 x 10 x 8 ft), with rings of small vent holes at the top and bottom. Its 8 cubic meters of volume was filled with pieces of limestone (5-10 cm) that condensed the atmospheric vapor and collected it in a reservoir. The yield ranged from 1-2.5 liters/day from March to September. The total weight of water was 190 lb; the maximum yield was 5.5 lb/day. Chaptal found that the condensing surface must be rough, and the surface tension sufficiently low that the condensed water can drip. The incoming air must be moist and damp. The low interior temperature is established by reradiation at night and by the lower temperature of the soil. Air flow was controlled by plugging or opening the vent holes as necessary. 
Calice Courneya patented an air well in 1982 (USP #4,351,651): A heat exchanger at or near subsurface temperature... is in air communication with the atmosphere for allowing atmospheric moisture-laden air to enter, pass through, cool, arrive at its dew point, allow the moisture to precipitate out, and allow the air to pass outward to the atmosphere again. Suitable apparatus may be provided to restrict air flow and allow sufficient residence time of the air in the heat exchanger to allow sufficient precipitation. Furthermore, filtration may be provided on the air input, and a means for creating a [negative] movement pressure, in the preferred form of a turbine, may be provided on the output... The air well is buried about 9 feet deep. The entrance pipe is 3-inch diameter PVC pipe (10 ft long), terminating just near the ground... This is an advantage because the greatest humidity in the atmosphere is near the surface." (7, 8) (Figure 4) 
 
Air flows through the pipes at 2,000 cubic feet per hour at 45oF with a 5 mph wind. This translates to about 48,000 ft3/day (over 3,000 lb of air daily). Courneya’s first air well used a turbine fan to pull air through the pipes. Later designs employed an electric fan for greater airflow. At 90oF and 80% Relative Humidity (RH), the air well yields about 60 lb water daily. At 20% RH, the yield is only about 3 lb/day. The yield is even lower at lower temperatures. The yield depends on the amount of air and its relative and specific humidity, and the soil temperature, thermal conductivity, and moisture. 
Acoustic resonance within the pipes might enhance condensation. The more recent invention of acoustic refrigeration could be used to advantage, as well as the Hilsch-Ranque vortex tube. 
It is necessary to cool the air to the "Dewpoint". All of the preceding devices appear to rely on night cooled mass to provide the needed temperature difference, yet leave the device open to daytime heating by the sun. I find indications that even in the daytime in certain conditions it might be possible to radiate to the sky 100 to 200 BTU per hour, which strictly in math could represent 1 pint or so of operation for every 10 square foot or radiation area.
Once the water has condensed the "dry" air, now cool, needs to be exhausted. This points out the flaw in all of the above. None of the above low-tech devices provide for heat exchange directly between the incoming and outgoing air , therefore the "coolness", essential to precipitation, imparted to the incoming air is directly exhausted, and rapidly eroded. 
Ideally, there should be sufficient heat exchange between intake and exhaust air that at the pipe open ends, they are virtually at the same temperature, despite being cycled thru a chilled spot. The transition between liquid and vapor water is, absent unknown science or magic, a matter of the transfer of 970 BTU per each pint condensed. (7760 BTU per gallon) 
Using a sky radiation approach to cooling your condenser core, if the latent heat of vaporization of water is 2.26 × 106 J/kg a 1 m2 radiator can provide 50 W/m2 of cooling, enough to condense 1 g of water in 45 s; 1 kg in 12.6 hr; or 1.9 kg per day. Reportedly production rates in the Southwest U.S. can average about 2 liters per day in the winter to over 6 liters per day during the summer, per square meter.” At the low end 10 m2 (1/4 acre) of radiators cooling humid air could produce 19 L of water per day. The humid air must of course be moved thru the cooling unit, and the “coolness” used to change air temperature recovered during expulsion of the “dried” air. 
A commercial, powered water condenser is sold under the name Aqua-Cycle, invented by William Madison, introduced in 1992. It resembles a drinking fountain and functions as such, but it is not connected to any plumbing. It contains a refridgerated dehumidifier and a triple-purification system (carbon, deionization, and UV light) that produces water as pure as triple-distilled. Under optimal operating conditions (80o/60% humidity) the unit claims to produce up to 5 gallons daily. 
Appropriate Technology Appendix - 2 - 3