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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Dear Paul<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">There was a lot of work done on this matter at Eindhoven University in the early 80’s. They published a list of foods and the energy requirement to cook them. It is not obvious but as chemical transformations
take place in the food, the temperature drops as the reactions are endothermic. So even then energy is going in, they do not rise in temperature some of the time.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">You can take foods to be wet, so using water mass is not far wrong. Cabbage requires one of the greatest inputs of energy to cook.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Regards<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Crispin<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Stoves <stoves-bounces@lists.bioenergylists.org>
<b>On Behalf Of </b>Paul Arveson<br>
<b>Sent:</b> Wednesday, October 16, 2019 6:04<br>
<b>To:</b> stoves@lists.bioenergylists.org<br>
<b>Subject:</b> Re: [Stoves] Energy requirement<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thanks for those who responded to my question, how much energy is required to cook a typical meal?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span lang="EN-US">I need more information. The way we would calculate the basic energy requirement is:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">E = q m dT <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Where q = heat capacity of food<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">m = mass of food<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">dT = temperature change <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Example (in metric units):<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Let's assume a meal is 1 kg of water. = m<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Water has a higher heat capacity than solid foods, so water is the worst case.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">It takes 4186 J to heat 1 kg of water 1 deg. C. = q<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Suppose we want to heat the water from 27 to 77 deg. C, or 50 deg. increase. = dT<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">So the energy required is 4186 x 50 deg. = 209,300 Joules.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">This is only the energy required to heat the food. But cookers are not 100% efficient, since some energy goes to heat the pot, the stove parts, etc. Also there is some heat loss during cooking due to conduction, convection
and radiation. <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Apparently efficiency is low for most stoves, so most of the energy doesn’t go into cooking the food. So the “steam cooker” was quoted by Frans as 1.2 MJ, which is 17% efficient (assuming he was heating 1 kg of water,
which was not stated). This in turn drives the fuel requirement. <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">What then are some typical numbers for cookstove thermal efficiency?
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Paul Arveson<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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