10 Homebuilt Tech Tools for the Developing World

It's tough to get a side-by-side Frigidaire when you live in North Darfur in Sudan. Even if you could get one, you wouldn't be able to power it. So what's a family to do when fruits and vegetables, exposed to the extreme heat, spoil in one or two days? Thanks to Practical Action, a U.K.-based nonprofit focused on using technology innovation and dissemination to reduce poverty, many African farmers and villagers use an amazingly simple clay refrigerator known as a zeer pot.

In its finished form, the refrigerator consists of one earthenware pot nestled inside a second larger pot, with a layer of sand in between. Making one requires little training and just a few easy steps. First, villagers use clay and water to make molds, which they dry in the sun. Then they press fresh clay around the molds to form the desired pots. After adding a base and rim to each, they dry the pots in the sun and then fire them in a pit of hot ashes. After cooling, the pots are ready for assembly. A layer of sand is placed in the bottom of the larger pot. The smaller pot rests on this layer. And, finally, sand fills the space between the two. To make the pot functional, villagers wet the sand, fill the smaller pot with vegetables and then place a wet rag over the whole thing. Once built, they place the pot on a stand for maximum air flow.

Twice a day, they must return to the pot and add more water to the sand, but the effort has a significant payoff, extending the life of vegetables two to three weeks. How does it work? By evaporative cooling: As water evaporates from the sand, through the porous outer pot, it pulls heat from the inner chamber, dropping the temperature several degrees. As a result, more food fills up hungry bellies instead of refuse piles.

The people of many developing nations still use biomass -- wood, charcoal, dung or crop byproducts -- as fuel for cooking. In Mexico, for example, 95 percent of rural households cook with wood on open fires [source: Ashden]. Unfortunately, woodsmoke contains toxins that have been linked to a number of health problems, including pneumonia, lung cancer, chronic obstructive pulmonary disease and heart disease.

Well-designed stoves, such as rocket stoves, can improve the efficiency of wood burning. Rocket stoves use a vertical combustion chamber and a horizontal fuel and air inlet at the bottom. The design improves heat transfer and makes it possible to direct hot gases to the cooking pot or griddle. Families that cook with rocket stoves consume far less wood and expose themselves to less smoke.

But why not eliminate biomass altogether? That's the benefit of solar cookers, which concentrate the sun's energy to slow-cook food. Box cookers -- the most basic type -- can be built using simple, easy-to-find materials. One basic design requires just two cardboard boxes (one smaller than the other), a small piece of glass, black paint and newspaper. Cut the box sides at an angle of 30 to 40 degrees, making sure the front of the larger box has a lip. Then nest the smaller box inside the larger, fill the gap between the two boxes with newspaper or other insulating material, paint the inside black and set the glass on top so it rests against the lip. When you place this cooker in the sun, it will heat up to about 250 degrees Fahrenheit (121 degrees Celsius).

An improved design uses sturdier materials, such as wood instead of cardboard and foam instead of newspaper. It also adds four foil-coated panels to act as reflectors to concentrate the sun's energy. The result: a cooking temperature of 350 to 400 degrees Fahrenheit (177-204 degrees Celsius) -- hot enough to roast a whole chicken!

The sound of Archie Bunker's flushing toilet was always good for a chuckle or two. But in many rural communities across the world, sanitary waste disposal is no laughing matter. According to the World Health Organization (WHO), nearly 2 billion people live without appropriate sanitation facilities and services. As a result, bacteria and viruses from human waste ends up in the water supply, leading to a number of diseases, including dysentery, typhoid and cholera. Two million people, mostly children, die from these diseases every year, says WHO.

Flushing toilets, which require large amounts of water and a complex sewage system, aren't the answer. A truly effective solution will require no electricity and will be both inexpensive and easy to construct from readily available materials. Enter the composting toilet, a bioreactor system that converts waste to biogas, which is then burned and superheated by a heat exchanger to sterilize the treated effluent. The concept is the brainchild of Duke University scientists Marc Deshusses and David Schaad, who won a $100,000 Gates Foundation grant in 2011 to develop the idea.

Although the design hadn't been finalized at the time we wrote this, the system will contain a sealed chamber, likely made of $100 worth of PVC, which will receive solid waste. In this oxygen-free environment, anaerobic bacteria will chow down, breaking down the waste and producing methane gas. Instead of releasing the gas, however, the system captures it and burns it. This final step is important because it does two things -- it kills harmful pathogens and keeps methane, a powerful greenhouse gas, out of the atmosphere. So we can treat our poop without pooping on the environment.

Nearly 70 percent of the Earth may be covered in water, but try telling that to a landlocked farmer trying to eke out an existence in Africa. According to the Food and Agriculture Organization (FAO) of the United Nations, 1.6 billion people live in regions where water is extremely scarce. By 2025, two-thirds of the world's population -- nearly 4.5 billion people -- could face severe water shortages. One of the biggest issues is irrigation. Agriculture is responsible for 70 percent of all freshwater and groundwater withdrawals worldwide, says the FAO, and yet it's essential if rural farmers are to feed their communities. In fact, irrigating a farm can vastly increase the amount of food it produces.

Low-cost, human-operated pumps offer an ideal solution to this paradox. They enable small villages to get the water they need for drinking and irrigation without putting unnecessary stress on an area's water reserves. Over the years, farmers have experimented with many types of water-pump technologies, including rope pumps, treadle pumps and rower pumps. Many of these designs require some machining and welding experience, as well as access to sheet steel, valves and other components. That's what makes the EMAS-Flexi water pump such an attractive technology. Originally developed in Bolivia by the Mobile School for Water and Sanitation (EMAS, in Spanish) to serve extended families or small groups with no more than 50 people, the EMAS-Flexi pump uses readily available components -- PVC pipes, galvanized iron pipe, thread adapters and two glass marbles -- and can be assembled quickly and easily.

Here's how it works. One PVC pipe, slightly smaller, fits into a second pipe. At the bottom of each pipe, a glass marble acts as a valve. The inner pipe attaches to a metal T-shaped handle that is blind on one side and open on the other to form an outlet. The pumping movement raises and lowers the inner pipe, which moves within the stationary outer pipe. An upward stroke creates suction, drawing water into the cylinder. A downward stroke displaces water from the cylinder, forcing it out at the top. The operator can pump about 4 to 8 gallons (15 to 30 liters) of water per minute, which is enough to provide drinking water and irrigate a small garden.

Harvesting rainwater is an ancient practice that's seen a revival in recent years. In developing countries, where people often hoof it for H₂O, it's attractive because relatively simple and inexpensive systems can provide clean water for a household or even a community. In industrialized nations, it's attractive because it reduces stormwater runoff and eases homeowner water bills.

A typical harvesting system has three basic parts:

Luckily, most modern houses come equipped with a catchment surface -- the roof -- and an adequate supply of gutters and downspouts (although one critical addition for rainwater harvesting is a system of filters and screens to keep debris out of the water supply). That leaves the storage tank, or cistern. In more sophisticated systems, cisterns can be large structures made from concrete or galvanized steel, sometimes located underground, sometimes not. Simple, homebuilt cisterns, however, are both possible and extremely functional.

The most basic designs use plastic barrels for water storage. A popularchoice is a 55-gallon (208-liter) barrel made out of high-density polyethylene, or HDPE, plastic, although even Rubbermaid trash cans can be transformed into an effective, albeit small, storage tank. Either way, the barrel must be opaque to prevent algae growth.

After that, it's a simple matter of retrofitting the container so it can function as a water collector. This may involve drilling two holes, one at the bottom to hold a faucet and one at the top to act as an overflow valve. Then you cut a hole in the top of the barrel, near the back, to receive a downspout. Attach some window screen over this opening to catch debris and foil pesky mosquitoes, and you have a perfectly serviceable rain barrel -- and a ready supply of water for gardening.

Like rainwater harvesting, composting has been popular on small farms for centuries. The process involves converting organic debris -- vegetation, food scraps and manure -- into a rich, all-natural fertilizer. Farmers use high-quality compost because it enables soil to hold more water and provides nutrients to crops, eliminating the need for synthetic fertilizers. This in turn increases the productivity of their land and leads to higher profits. It also reduces the amount of solid waste entering processing facilities and landfills.

Biological decay occurs whether you want it to or not, but the idea behind composting is to make the process happen more rapidly. One technique, known as heap composting, doesn't require a structure. You simply throw organic material into a pile, about 3 feet (1 meter) high and 3 feet wide, and then turn the material regularly using a pitchfork. You can increase the efficiency of composting, however, if you use a compost bin -- a structure to hold and concentrate organic debris and to provide a suitable home for the organisms that make the decay possible. The easiest structure to make is a wire-mesh holding unit, which requires a 10-foot (3-meter) length of 36-inch (91-centimeter) wide galvanized chicken wire, heavy wire for ties and three or four wooden posts. You simply form the length of chicken wire into a cylinder, connect the ends together with wire and then attach the whole thing to posts driven in the ground.

Bins that can rotate work even better because they mix the organic material more thoroughly and speed up the decaying process. It's possible to build a horizontally mounted rotating barrel, but it requires a significant input of time and energy. Another solution is to buy a food-grade plastic barrel, with a removable lid, and then drill a series of holes across the entire surface. After filling the barrel with organic material, you simply lay it on its side and roll it regularly over a level surface. Using this method, a large volume of yard waste can be composted in three weeks to six months.

Air conditioning may seem like a luxury, not a necessity, but some studies have shown that productivity increases dramatically if workers do their jobs in cooler spaces. What does that say about places such as Brazil and India, where just 11 percent and 2 percent of households, respectively, have air conditioning [source: Rosenthal]? It says that people living in developing nations will need A/C as much as they need clean water and better access to health care.

Most of us think of units filled with refrigerants, especially chlorofluorocarbons like Freon, when we think of air conditioning, but some cooling systems work on a different principle. Evaporative coolers, also known as swamp coolers, take advantage of water's ability to change from a liquid to a gas. Heat is required for this state change to occur, so if you can get water to evaporate, you can cool something down. Swamp coolers do just that by blowing dry, hot air over a moist fabric. As the hot air encounters the fabric inside the unit, it evaporates the water, losing some of its heat in the process. A blower then forces cool, humid air out into the room.

You can build a homemade swamp cooler using a cooling fan from an old computer, wooden craft sticks, an absorbent cloth and a small, 2-watt solar panel for power. First, you create a frame out of the craft sticks, with the fan supported at the top so it blows down and two decks below the fan to support strips cut from the fabric. Everything should be glued so the structure stands upright and sturdy. Then you connect the wires from the fan to the solar panel (or batteries as a not-so-green alternative), wet the fabric and let the cooling begin.

Believe it or not, more people in developing countries use cell phones than people in developed areas. According to some research, between 80 and 95 percent of the population of Kenya, Mexico and Indonesia send text messages on their mobile devices [source: Mlot]. But even if family members living in a poor African community have cell phones, they might not have electricity to charge them. So what do they do? Many must charge their phones at kiosks for a small fee.

With a little know-how and just a few materials, you can build your own bicycle-powered cell phone charger. In addition to a bicycle headlight generator, you'll need some basic electronics -- circuit board, rectifier, capacitor and voltage regulator. First, you attach the generator to either the front or back wheel of your bike. Next, you cut the cord on your cell phone charger to expose the positive and negative wires. Now mount the electronic components on the circuit board and wire everything together: generator to rectifier, rectifier to capacitor, capacitor to voltage regulator, voltage regulator to cell phone charger. Finally, cover the components with electrical tape and mount the circuit board just under the seat post. The charger itself can rest in a basket or in a bag attached elsewhere on the bike frame.

When it's time to hit the streets, attach your cell phone to the charger and start pedaling -- the faster or farther you go, the more juice your phone gets. Just remember not to bike and text at the same time.

Tour a middle-class home in the U.S., and you're sure to come across an old computer collecting dust in a closet. Not so in developing countries, where families have little hope of using a PC to get a weather forecast or do research for school.

Getting laptops to these regions is just part of the solution. The United Nations estimates that 1.5 billion people around the world still live far from their country's electric grid, which means powering electronics is almost a bigger problem than getting them in the first place [source: Rosenthal]. Small-scale renewable energy, especially solar, can provide a viable solution. Many families in Africa have installed small solar power systems on their huts, enabling them to charge a cell phone and run a few lights.

It's also possible to harness the sun's energy to charge a laptop, and a few off-the-shelf products make it easy to do. A typical offering comes with a 16-watt solar panel and a battery integrated into a laptop bag. You can make the same thing if you're handy and have access to a few tools. You'll need to acquire the core components of the charger: the solar panel, 12-volt battery packs, a 12-volt car power outlet and an old suitcase or briefcase slightly larger than the laptop. Then you'll need to remove the padding from the case to make some extra room. Next, mount the solar panel, the solar charge controller and the car power adapter to the outside of the case. You'll need to drill into the case frame to accommodate attachment screws and to create holes for wiring. After that, disassemble each battery pack and reconfigure the 10 cells so that they form long flat packs that fit easily in the case. Attach leads to the packs a, link all of them together and attach them to the positive and negative terminals on the solar charge controller. You can find detailed instructions here.

When the device is done, set it in the sun and let the batteries charge for several hours. Then you'll be ready to charge your laptop and anything else that can be plugged into a car adapter.

OK, so we've managed to power some laptops in developing countries. Now what? Using a computer these days means getting onto the Internet, and that means having access to broadband connectivity. Unfortunately, many people don't have that luxury. In places like South Asia, there are only 9 million broadband subscribers compared to 294 million and 211 million in the European Union and North America, respectively [source: Kim].

Wireless technologies offer a promising alternative to people living in rural communities, allowing residents to tap into conventional telecommunications infrastructure. This, however, requires an inexpensive way to increase the range of a wireless signal. That's where a tin can waveguide antenna -- or cantenna -- comes in handy. You can make one of these devices using an old soup, vegetable or coffee can (cleaned out, of course), an N-type female chassis connector, copper wire, a USB WiFi adapter with removable antenna and a special cable known as a "pigtail."

Assembling a cantenna is easy. First, cut a piece of copper wire about 1.25 inches (3.2 centimeters) long and solder the wire to the N-type chassis connector. While it's cooling, drill a hole in the tin can just large enough to accept the chassis connector. Then pass the connector through the hole so that the copper wire is inside the can. Bolt or screw the connector to the can to keep it secure. Next, remove the factory antenna from the USB WiFi adapter and screw the smaller end of the pigtail cable onto the adapter. The other end of the pigtail should attach to the N-type female chassis connector. Finally, insert the USB adapter into your computer, mount the can outside, point it to a likely signal and, voila, you have wireless Internet.

You should note that the reception of the cantenna depends on the dimensions of the tin can you choose. This Web site has a calculator to determine where the chassis connector should be located based on your can's diameter. Another important note: You may need a fairly long piece of pigtail depending on the distance between the cantenna and your computer.

Most of the "new" technologies presented in this article aren't new at all, but are based on centuries-old concepts. Makes you wonder how many great ideas have been lost to history.

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