[Default] On Mon, 6 May 2013 18:48:57 -0600,Ron <[email protected]> wrote:
>Martin > > B. I really like york idea of the aquarium pump, but ask you and others > knowledgeable on fans, blowers, pumps what might be the downsides. Where AC > electricity is no problem, and one has such pumps (I have several), can you > describe a scheme to both vary the output and measure the air flow > quantities? Ron, Martin and stovers, We have of course talked about, and Philips implemented, a TEG to provide electricity for air flow. To my mind ' especially given the various orifices and bluff bodies which act as restrictions and produce turbulence, if the primary air flow is forced the greater volume of offgas resulting can entrain its own secondary air. This is why I have tended to use centrifugal (snail like) fans. Metering the primary air to keep it constant as the fuel+char bed resistance changes has been a wish of mine. With a simple hot wire air mass meter and a feedback loop to change the air supply. I have recently been shown a TEG just 40mm square with a hot side that can stand 350C and Cold side 180C and a 140 Watts of heat throughput that can output a couple of Watts, now this low conversion of heat to electricity is only 4% but it's a lot better than previous ones I have seen and the thermal cost is small, unfortunately the capital cost makes it a toy for the first world. > > A few years ago, Andrew Heggie gave me a small homemade $1 or $2 device > to do this. Anyone found such in local hardware stoves? Wall dimmer > switches? A single speed device won't tell us enough. To be fair this prototype was donated by the maker, Steve Taylor, it's a brilliant little pulse width modulated voltage control, that means it is very efficient as it changes speed. It also is good in that it can operate, and be left set, at a low speed, many motors won't start at their final low speed but this one starts at high power and then immediately modulates down to the slow speed without stalling. I don't think it was quite as cheap as you remember because there was not much interest from[stoves] at the time Steve could not calculate a market rate with no known demand. Suffice it to say I still have the box of bits , less a few crucial capacitors, to make more but Steve would have to help me out with some instructions as I am not at all adept with a soldering iron. AJH _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org for more Biomass Cooking Stoves, News and Information see our web site: http://stoves.bioenergylists.org/
