ISEC Archives

Resources from Insulated Solar Electric Cooking (ISEC):

Erythritol Properties

Solid Density: 1.48 g/cm3 at 20 ˚C

Liquid Density: 1.3 g/cm3 at 140 ˚C

Melting Point: 117-120 ˚C

Boiling Point: 330.5 ˚C

Heat of Fusion: 315-379.57 J/g

Solid Specific Heat: 1.38 J/g*K

Liquid Specific Heat: 2.76 J/g*K

Solid Thermal Conductivity: .733 W/m*K at 20 ˚C

Liquid Thermal Conductivity: .326 W/m*K at 140 ˚C,%C2%B1%200.1%20%E2%88%98C%2C%20respectively.


Here are other properties from a different publication. Note that the boiling point is 60 C hotter.


Video on how to spin aluminum pots

Matt Walker’s Senior Project (2020) on corrosion

Heating Element calculations, I calculated lengths and resistances of several electrical heating elements.

Parts list and brief instructions of how to make an ISEC with thermal storage and without thermal storage.

Not a publication: Matt Walker’s Independent Study Report (Winter 2019) outlines our first baking implementations as well as general improvements in ISEC using diode heating with 1N5402 rectifier diodes purchased through TME (Transfer Multisort Elektronik),  factory specifications. We’ve recently conducted experiments using Grape solar panels. See factory specifications: GS-STAR-100W.

Collaborators we’ve fallen out of touch with:

Ángel Marroquín de Jesús. PhD., Professor Energías Renovables, Universidad Tecnológica de San Juan del Río, Mexico

Sophie Brock, Solar Household Energy, SHE globally, but with operations in Oaxaca, Mexico


Archived Work

Immersion Heaters


There are 3 main components to Immersion Heaters:

  • – electrical heating element
  • – insulation
  • – external casing

Electrical Heating Element

The heating element consists of a string of diodes (to see the history of this design, click here):

  1. Diodes effectively pull power from a solar panel because the voltage on a diode stays relatively constant with changes in current, in contrast to a resistive heater that can only be optimized for one time of day.
  2. A string of diodes can act as a crude voltage controller for house-hold appliances such as charging for cell phones and lights. 

The diode chain is inserted into a food safe enclosure with a composite as shown below.

The small scale diode chains we test with, shown below, consist of 5 diodes, a thermocouple attached to the hottest point of the diode, and a bimetallic thermostatic switch with shutoff temperature of 160°C.

Heaters are made of a diode chain inside of a food safe housing. Wires protruding are applied voltage, thermocouple wires, and voltage controlled output.

Diodes present a thermal challenge because they get as hot as NiCr wire, which often runs glowing red hot. We use rectifier diodes (1N5408) costing about $0.02 each that are rated up to 150°C. Although we have found that the diode functions up to about 300°C, they still easily reach that heat, so we must make an effort to keep them cool. The challenge is to develop an electrically insulating composite that is thermally conductive (see how we measure the thermal conductivity of composites). We are presently using concrete.

We add bimetallic thermostatic switches to our diode chains, which open the circuit when the switch itself reaches its temperature rating: in our case, 150°C.

Small scale heater of 5 parts MgO powder and 1 part Cement. Peaks and dips indicate where the thermal switch turns on and off.

Heater ran in near boiling water, water is keeping the diodes cool enough for the thermal switch to not turn on. Shows how the diodes heat up and maintain a constant temperature.

External Casing

For the surrounding pipe, we use aluminum because it is safe for cooking and easier to work with than stainless steel. With aluminum, we are able to heat treat, bend into a U-shape, or seal the end of the tube with a vice in a toothpaste-like manner. For more information on how we work with aluminum, click here.

Manufacturing & Videos

In addition to choosing materials that can be found easily and affordably almost anywhere in the world, we created a manufacturing process that allows anyone to build these heaters with no heavy machinery and only very basic handheld tools. This allows them to be made in the village they are used in, creating sustainable, local economies.

  • Manufacturing Process and material list by Spring 2018 Appropriate Technology Class
  • Instructional How-To-Build video by 2018 Summer Research Team, special thanks to Grant Bortz for film & edit
  • Promotional Video: Why Should You Care? by 2018 Summer Research Team, special thanks for Grant Bortz for film & editt: graphic and explanation of what it does picture of diode chain, insertion process, and finished product. Analysis of related costs. Temperatuink you should spin the “how we got here onto a separate page “development process and  lessons learned,” onto different page.
  • A working paper on how we hope to bring solar electricity in Africa down to $0.02/kWh. We use a diode chain (explained below) instead of a resistive heater. This allows for us to utilize the solar electricity for charging appliances and cooking together. Using close to 100% of the solar electricity results in a very low cost of electricity in price per kWh used.

SuperGroup (includes laboratory and disseminating teams) meeting, Sept. 22

Inactive Collaborators: 

Clif Hiebsch, and Miranda Kelly of WAEV dedicated to empowering Masai women in Tanzania, please see WAEV project from Fall 2019.

John Mullett ( of SOWTech, UK and in Malawi

Ajay Chandak, PRINCE, India