[Stoves] solar cooker response (changing thread name)

Mon Jun 12 16:00:20 CDT 2017

Crispin:

I see no thinking behind this obsession with physical efficiencies.
Induction stoves caught on in some segments of the Indian urban middle
class because of convenience, in particular if there was only one cook in
the house and s/he had other responsibilities such as children or a jpb
outside.

Another was that it puts out less heat to the room than does a flame. Makes
a difference in Indian summers 10a-6p at least.

I have used induction stoves and am mostly happy with it because I have
gas, microwave, toaster, kettle, coffeemaker on the side.

The binding constraint in modern energy transition is financing the
investment on the individual user side, not the corporate supply or user
sides. Physical efficiencies play some role at different points in the fuel
cycle, but their relative economics vary, depending on the cost structures
of other inputs.

The sooner we dump physical efficiency as a key guiding metric, the better.

Enough of physics mania.

Nikhil

------------------------------------------------------------------------
Nikhil Desai
(India +91) 909 995 2080
*Skype: nikhildesai888*

On Tue, Jun 13, 2017 at 2:09 AM, Crispin Pemberton-Pigott <
crispinpigott at outlook.com> wrote:

> Dear Andrew
>
> When we were looking at the claim that simmering a pot could produce an
> 'efficiency' and fuel consumption 'per litre simmered', Yixiang and I
> investigated induction cookers in the 1800-2100 W range. All were single
> plate, like a gas fired wok cooker. Some have six settings for power, down
> to 300 W.
>
> The 88% efficient were marked C, the 90% were marked B and the 92% were
> rated A. That is a Chinese national rating system.
>
> ‎In Canada there were, for a time, no powerful ones. All were under 1 kW.
> It could easily be run on a 1 kW inverter. Given the coincidence  of the
> voltage being half and the power being half, I am wondering it the guts are
> same, just that it runs on a lower voltage. They are still rare in Canada
> except for expensive built-ins, 4 or 5 plate glass tops.
>
> That is all an aside. What we measured was the direct heating of the water
> and it was a lot less than 90% efficient. The stability of the power
> consumption was excellent. Yixiang reported the efficiency in the 70's.
> ‎It is possible that the pot itself has an effect of the efficiency of the
> induction. That is going to affect the battery life.
>
> Regards
> Crispin
>
>
>
> On 12 June 2017 at 20:35, Crispin Pemberton-Pigott
> <crispinpigott at outlook.com> wrote:
>
> > There are two kinds of induction heater that I have seen at the bottom
> of the market: single and double plates. The double one has a high power
> (often 1000-1100 W) and a 700 W one. Both plates on is about ten amps.
>
> Mine was the cheapest I could find locally and is rated at 2100W but
> you seldom use high power, indeed my first few tries I burned food
> when frying
>
> https://www.amazon.co.uk/Tefal-Everyday-Induction-
> IH201840-Ceramic/dp/B00ER445UQ
> >
> > ‎The efficiency of the single plate units is 88-92%. That is much higher
> than an electric hot plate.
>
> Yes and because it heats the pan directly there is no loss involved in
> heating the hob, it does have the parasitic load of a cooling fan for
> the electronics.
>
> >
> > So running the big plate for 30 minutes is 0.5 kWh. 500 Watt-hours. That
> is roughly a quarter of a regular car battery (1800 Wh). Is that reasonable?
> >
> > A large car battery can store about 4.8 kWh. It is fine for cooking, but
> not heating water.
>
> Because it is fast you don't need it on for long, it also has various
> sensors and a timer for things like gently heating milk, or porridge,
> without it burning on the bottom of the pan.
>
> If no one else has figures I will try and monitor its electricity
> consumption, we tend to only have two for meals in this household and
> I don't believe I have ever used it for more than 15 minutes at a
> time.
>
>
> A typical lead acid battery for a large diesel engined car is about
> 95Ah but you seriously damage it's life if you run the voltage below
> 11.5V, in practice as long as you have the capacity for the peak load
> you would use a similar rated leisure battery but still only get about
> 24Ah from it, so about 0.5kWhr. This just about matches your
> calculated usage.
>
> My panels actually run at 300V and I would be looking to a lithium ion
> storage battery if I were not grid connected.
>
> I guess this sort of thing is for the remote but middling affluent
> users rather than the sort of people we normally think would benefit
> from improved stoves as the capital investment is large.
>
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