| Yet another cookstove piece appeared in my Google News alert, this one from Science Alert. It's tightly focused on a particular technology and is written in an over the top style, sprinkled with "brilliant", "genius" and other superlatives in so many places that it could have been written by one of the subjects' mothers. Anyway, the point of the article is to describe a stove that burns rice husks and its developers. And this is quite interesting, as it involves some clever engineering.
One of the fuels the stove can burn is rice husks, which are plentiful in many developing nations. Husks are often burned in the field as a way of reducing their volume and helping the soil, but this leads to air quality problems, both locally (toxins) and globally (black carbon). With this stove, the ash remaining from the husks can then be spread on the fields, giving the same result as if they were burned in situ.
The stove's efficiency is greatly enhanced by a small electric fan that drives fresh air across the burning biomass, providing a steady stream of oxygen for the combustion process. But wait a second, you might think, many villages don't have electricity, so how will this work? Steve Garrett of the Pennsylvania State University has a solution: thermo-acoustics, in which heat is converted to sound, which is then converted to electricity. Garrett is a specialist in thermo-acoustics and has designed these generators for such clients as NASA (for use on spacecraft) and Ben and Jerry's (ice cream freezers). |
The high efficiency is a great feature of the design but is also its biggest weakness: with an electric fan and thermo-acoustic generator comes a relatively high price ($20-25) and potential reliability problems. But that electrical generator is what might ultimately make this stove a big hit:
Garrett points out: "Take a look on the internet at the dark areas of the planet at night. These are the places where there is no electricity, where people burn biomass to cook or warm their homes. That is where most of the black carbon comes from. In Asia, unlike the developed world, one half of the global warming potential is due to black carbon and other products of incomplete combustion such as methane, carbon monoxide and ozone precursors.
"It is also a big deal using a simple stove to put electricity into people's lives in areas that may never be on the grid. They can also use it to charge a battery to light their home, or to power a cell phone."
With the world's focus on climate change and the significant role of household cooking, we'll probably be seeing more articles on the subject, ideally ones that follow up on interesting ideas like the stove described in the Science Alert article.
For more background on black carbon, check out the testimony of black carbon experts at a March 16 hearing of the House Select Committee on Energy Independence and Global Warming and a workshop on short-lived climate forcers sponsored by the U.S. EPA (which includes a presentation by Kirk Smith about cookstoves, PDF).
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