[Stoves] Why is it still so difficult to design cookstoves for 3 billion people?
crispinpigott at outlook.com
Sun Jun 19 01:17:22 MDT 2016
That was informative. Thanks.
I would like to bring to everyone’s attention a type of gasifier that is bottom-lit, updraft, that is used to make a high energy wet gas. CAU grad student Riaz Ahmad has been working on one and has been able to produce a gas capable of working in a standard gas burner. He is using forced draft both to run the gasifier and to produce a pre-mixed gas. The major advantage of such a layout is that it can be continuously or episodically refuelled indefinitely. This type of gasifier is made by Hirendra Chakrabarti in India (and his company).
As the fuel is pyrolysed, the ash (or char) can be removed from the bottom while the hot zone is moving upwards. As the hot zone rises above the middle of the vertical height, the ash (or char) an be removed from the bottom and additional fuel added through an airlock at the top.
Riaz has been creating usable gas from a variety of materials including large pellets (small briquettes) made from agricultural waste.
The advantages of being able to refuel the stove while it is running are obvious.
TLUDs were developed in China. Note intense tall flame, the Chinese developed this advanced secondary combustion over primary combustion technology specifically for wok cooking, their preferred cooking methodology. In fact more TLUDs are produced in China than anywhere else in the World. Natural draft TLUD's have been utilized in China for over a century from what we can determine. Unfortunately no documentation exists. The stoves are found in old homes throughout China that have fallen down decades ago.
If you explore ancient Chinese homes, you'll find natural draft wood burning TLUD configurations in numerous homes. The top burning gasification was referred to as 2nd wind. This additional firepower is highly desired and intended to maximize temperatures required for wok cooking. While great discussions have been going on regarding turn down power designs as a relatively new innovation, it is not.
We have been selling both a natural draft TLUD with primary air dampner for 4 years now, and a forced air fan stove with a pulse width modulator (interrupts electrical signal to create fan speed to regulate firepower) since 2012, in addition to rocket stoves. The TLUDs cook faster and hotter than the rocket stove, but actually complement each other for different styles of cooking.
Although a TLUD can easily return to high firepower with the addition of new fuel, there is also a cadence to cooking with a TLUD that occurs over time. The turn down control when cooking with a TLUD is a natural process over time, with or without a mechanical damper. That seems to be a nuance missed by many.
Todd Albi, SilverFire
On Thu, Jun 16, 2016 at 10:47 PM, Mangolazi <mangolazi at yahoo.com <mailto:mangolazi at yahoo.com> > wrote:
How about China? There are hundreds of millions of farmers and rural dwellers there, most of them still using firewood or biomass for cooking and heating. LPG is used mainly in urban areas and it's mainly piped gas, not canisters.
I've yet to see any TLUD stoves during my travels there, despite most of the EBay woodgas stoves being made there. Most farm houses use simple chimney stoves or 3-stone fires. I've seen nomadic herders up in the Tibetan plateau using cast iron chimney stoves but even those were smoky, filling up tents with choking soot. TLUDs running on wood and dung could provide interior and cooking heat with much lower emissions, provided they can work at high above 4000 m.
Anyway, just my 2c...
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