[Stoves] Powering a TLUD Fan

Thu Aug 30 16:29:25 CDT 2012

Crispin,

On Thu, Aug 30, 2012 at 10:22 PM, Crispin Pemberton-Pigott <
crispinpigott at gmail.com> wrote:

> Dear Friends of Fans (FoF)
>
> Thanks Frans and Phil. I think the fan power can be reduced on Paul O's
> stove by increasing the length of the outer sleeve providing secondary air.
>

I have experimented with changing the length of the burner housing,
 and this is such a delicate undertaking.

> There is little flow resistance to secondary air flow and it can be used to
> draft primary air flow to a certain extent.
>
> The vertical height of a stove directly affects the requirement to provide
> primary air pressure. As the fuel packing also affects this, several
> solutions are available to reduce the need for pressure. My point is that 2
> watts is a lot of power for a stove fan and it is worth looking at the
> overall design to see if it is needed at all, and when. For example, it may
> be required for 5 minutes in the beginning but not after that, or 15
> minutes, or for 1/2 the burn etc. This need impacts the battery life
> requirement. It may be that a 'fan powered stove' only needs fan power part
> of the time. That being the case, a super capacitor might be a worthy
> candidate because it can be charged in a few seconds.
>

In the case of rice hulls, very little power is required at the beginning
of the burn.
But toward the end of the burn, the power requirement at least doubles.
Rice hull biochar provides far more resistance to the flow of air than rice
hulls.
Thanks.
Paul Olivier

>
> Regards
> Crispin
>
>
>
> Phil,
>
> 3x LiION  =3,7Vx3=11,1V  Charger needs 4,2x3=12,6 maximum or EXPLOSION RISK
> 2W motor at 12V-------->0,1666 A 8h xO,166A =1,8Ah Laptop cells are 3,6 Ah
> and more Sun cell 15,6V---------> 12,6 V +3V for charging  regulator LM317
>
> PC  uP fans exist at 5V x0,2A=1W you could power with 2 cells; Also a dual
> fan of 2x 1W
>
> Regards
> Frans
>
> I see Paul Oliver's work to be excellent and appreciate how a variable
> speed
> fan can offer excellent control over TLUD operation. My reservation is that
> there are many places where even the small power requirement (Paul says 1-2
> watts) just isn't available. Lots of people here in Nicaragua are totally
> off-grid and don't have reasonable access to a way to charge a battery. So,
> I am been thinking about options. Being, among other things, an electronics
> geek, here is what I have been thinking about.
>
>
> Running the TLUD 8 hours a day at "average" fan speed means 12 watts per
> day. At 12 volts that's one ampere hour. I have been thinking about a
> couple
> of approaches. One is "higher tech" but may be a better solution at an
> equivalent or lower cost. In both cases I am just thinking of a
> photovoltaic
> panel to charge the battery. The difference is the battery voltage.
>
> Small PV panels are pretty common on the surplus market. For example,
> Electronic Gold Mine (http://www.goldmine-elec.com/) offers an assortment.
> The specifications vary from 7 to 35 volts open circuit with output power
> in
> the range of 1-3 watts. Prices are from $4.50 to $15. As this is quantity
> one retail price information, it is likely the could be found at
> significantly lower costs.
>
>
> As any PV-based system will need some sort of charge controller for the
> battery and what PV cells (in particular, what voltage) will be available
> at
> the best price point, I am thinking that using a single-cell Lithium Ion
> battery (3.7 volts nominal) would make the most sense. Units with a
> capacity
> of 2.2 ampere hours and more are commonly used in laptop computers. They
> offer reasonable life, low cost and the possibility of finding them on the
> surplus market. The cells can be paralleled if higher capacity is needed.
>
> A switching "up-converter" would be needed to supply the 12 volts needed
> for
> the fan. The speed control could be incorporated into the up converter
> which
> would reduce the cost and increase the efficiency.
>
> The alternative would be to use a more or less 12 volt battery (three
> Li-Ion
> cells in series) so that the up-converter could be eliminated. My initial
> guess is that the reduced electronics cost would not be as much as the
> increased battery cost but it is a viable alternative as long as higher
> voltage surplus PV panels are available.
>
> While this sounds like a lot of electronics, this is all very common stuff
> that you find in, for example, cellular phones. There is some design work
> needed but the actual component costs will be very low.
>
> Comments?
>
> --
> Phil Hughes
> nicafyl at gmail.com
>
>
>
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-- 
Paul A. Olivier PhD
27C Pham Hong Thai Street
Dalat
Vietnam

Louisiana telephone: 1-337-447-4124 (rings Vietnam)
Mobile: 090-694-1573 (in Vietnam)
Skype address: Xpolivier
http://www.esrla.com/
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