[Stoves] Efficiency of clean fuel

[Philip Lloyd]

I don't recall a proposition that "an electric hob transfers 40% of the
thermal power into the pot." 

What we have measured is an 80+/-1% efficiency of transferring electrical
energy received by the hob into thermal energy in the pot.  This efficiency
was measured with a voltmeter and wattmeter on the electrical feed to the
stove, and the mass of water turned to steam during boiling, at close to sea
level. The hob was a simple resistance element coiled into a spiral, such as
is widely available as a cheap cooking device, and drew about 0.9kW at peak
power.  The pot was a simple, flat-bottomed aluminum pot.

For a power station at 37% thermal efficiency, and losing 8% of the
electrical energy in transmission and distribution, that works out as 27.2%
overall efficiency from heat energy supplied at the power station to heat
energy into the pot, which is better than most.

Hope that clarifies things!

Happy New Year.

(Dr)Philip Lloyd
Energy Research Centre
University of Cape Town
Private Bag Rondebosch 7701
South Africa
Tel +27 (0)21 650 3896
Fax +27 (0)21 650 2830

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of andrew
Sent: 31 December 2007 03:52
To: Discussion of biomass cooking stoves; bioconversion at listserv.repp.org
Subject: [Stoves] clean fuel

On Sunday 30 December 2007 16:57, Tom Miles wrote:

In deference to Paul I'll attempt to move this bit of the discussion to
[biconversion], though it will still reference the [stoves] thread. All such
attempts have failed in the past because that list hasn't achieved critical
mass and it spans a broad spectrum that people already discuss on other
forums.

I think establishing the relative total efficiencies of competing
technologies is relevant to [stoves], especially following Sharon Gordon's
recent query. With Philip Lloyd's proposition that an electric hob transfers
40% of the thermal power into the pot and Steve's 30% grid delivery from a
thermal power station (inc transmission losses) that gives an overall 12%,
doesn't even a 3 stone fire beat that?