Sustainable Design Update

Treadle Pump (Sierra Magazine)

Nearly two billion people live off the grid or with very limited access to electricity.  If you live in slum cities with limited power or in rural parts where the power lines don’t reach,  lack of power limits your options in life and it causes unique environmental problems.  For one, if you light your home with candles, kerosene or battery operated lights, you create pollution at an alarming rate.

Recently  Sierra Magazine ran an article about what can be done to provide opportunity for people without electricity while helping the environment.  Sierra also mentions our work at The Appropriate Technology Collaborative and our efforts to help people with economically viable and sustainable technologies.

WITH 1.6 BILLION PEOPLE LIVING OFF THE GRID, the financial and environmental costs pile up quickly. Residents of the world’s poorest nations sometimes spend a third of their income on kerosene, a fuel that poisons lungs and poses a fire hazard; a kerosene lantern emits 550 pounds of carbon dioxide every year. Battery-powered lights are an option, but could result in mountains of tiny cylinders of toxic waste. Inexpensive devices that harness the sun and wind can supply small amounts of power, come from local materials, and create local jobs. The developing world’s population is expected to grow by 2.5 billion over the next 40 years, so these innovative energy savers can’t come soon enough.

More at:  Sierra Magazine

Check out: The Ferris Files

Thermoacoustic Engine Schematic

We at the Appropriate Technology Collaborative have started work on a Thermoacoustic Engine to be powered by waste heat from wood (or charcoal) burning stoves in the developing world.  Our goal is to make a simple, easy to build and maintain power source that makes 20 watts for $20.00.  There is about 2000 watts of waste heat generated in the typical wood cooking stove used in millions of households around the world.  We also are looking at ways to increase the efficiency of wood stoves and at ways to use cleaner burning charcoal made from agricultural waste + create a home power system that can run LED lights, a radio and more.

The thermoacoustic engine is difficult to explain.  Because this is an important project in our office I find myself sketching on napkins and explaining the inner workings to a lot of people with mixed results.  Luckily David Ferris, who writes for Sierra magazine and other publications has taken on the task.  David has a gift for making complicated things easy to understand.

From the Ferris Files:

The thermoacoustic engine is one of the weirdest forms of renewable energy I’ve heard of, and I had to have it explained to me several times before I started to get it. No description I read on the Internet made any sense. After consulting with John Barrie, an inventor who is designing a low-cost model for use in rural Guatemala, I created a description the rest of us could understand.

In short: The thermoacoustic engine uses heat to create sound, and sound to create electricity.

How’s that again? For the statement above to make sense, one has to understand the intimate relationship between sound and heat.

Imagine an impatient driver honking as you amble across the street. As the purple-faced motorist presses his horn, your innocent ears perceive the honk as a sound wave. What is a sound wave? Though we perceive it as sound, in reality it’s a wave of pressure. The crest of the wave compresses air molecules as it travels, while the trough of the wave is a little decompressed. That pressure wave enters your ear and strikes the tympanic membrane like a drumstick on a drum, making you turn and glance at the driver.

Now here’s where the heat comes in. The high and low-pressure parts of a sound wave actually have different temperatures, like the difference in mood between the angry driver and your cool self. The high-pressure part is hotter and the low pressure part is cooler. It’s this gap between hot and cold that makes a thermoacoustic engine work.

More about the Thermoacoustic Engine by David Ferris

Check Out: The Ferris Files