Energy-efficient cooking methods

Abstract

Energy-efficient new cooking techniques have been developed in this research. Using a stove with 649 ± 20 W of power, the minimum heat, specific heat of transformation, and on-stove time required to completely cook 1 kg of dry beans (with water and other ingredients) and 1 kg of raw potato are found to be: 710 (±24) kJ, 613 (±20) kJ, and 1,144 ± 10 s, respectively, for beans and 287 ± 12 kJ, 200 ± 9 kJ, and 466 ± 10 s for Irish potato. Extensive researches show that these figures are, to date, the lowest amount of heat ever used to cook beans and potato and less than half the energy used in conventional cooking with a pressure cooker. The efficiency of the stove was estimated to be 52.5 ± 2 %. Discussion is made to further improve the efficiency in cooking with normal stove and solar cooker and to save food nutrients further. Our method of cooking when applied globally is expected to contribute to the clean development management (CDM) potential. The approximate values of the minimum and maximum CDM potentials are estimated to be 7.5 × 10¹¹ and 2.2 × 10¹³ kg of carbon credit annually. The precise estimation CDM potential of our cooking method will be reported later.

Appendices

Appendix 1

Table 11 Reference cooking time table (accounting time from first exhausting gas of cooking (i.e., first whistling))

Appendix 2

σ:

Stefan–Boltzmann constant (5.67 × 10⁻⁸ W/m²K)

L _v :

Latent heat of vaporization (2.26 × 10⁶ J/kg or 540 cal/kg)

c _w :

Specific heat capacity of water (4,200 J/kgK)

c _p :

Specific heat capacity of the pot (896 J/kgK; Eckert and Drake 1972)

P _o :

Atmospheric pressure (101,325 Pa)

ε :

Emissivity of the pot (assumed to be 1)

g :

Acceleration due to gravity (10 m/s²)

m _p :

Mass of the pot with cover (1.45 kg) and without cover (0.85 kg)

h :

Height of the pot (14 cm)

r :

Radius of the pot (10 cm)

d :

Thickness of the pot (3 mm)

r _n :

Nozzle’s valve radius (0.19 cm)

m _h :

Mass of the head of pressure limit valve (71.1 g)

T _p :

Pot’s external temperature (degree Celcius)

T _a :

Initial temperature of the pot (degree Celcius)

T _i :

Pot’s internal wall temperature after on-stove time (degree Celcius)

t _i :

Total on-stove time

m _w :

Mass of water used

m _f :

Mass of rice plus water after time t _i of cooking

Δm :

Amount of water lost (≈10⁻³ kg)

A _v :

Area of the nozzle’s valve: $\pi {{\mathrm{r}}^2} = 1.135 \times {10^{{ - 5}}}{{\mathrm{m}}^2}$

A _p :

Area of the pot = 2πrh = 0.088 m²

W _h :

Weight of the head of pressure limit valve: mg = 0.711 N

Appendix 3

The approximate estimation is made as follows: according to Sohel et al. (Ref. a) the approximate firewood (biomass) consumption for a family in Bangladesh for cooking can be taken as 6.5 kg per family. This translates to roughly 1 kg per person per day. Now it is estimated (Ref. b) that in 2020, approximately 2.7 billion people will be dependent on biomass for cooking. Using the carbon factor of firewood as 1.835 (Ref. c) we estimate the total CO₂ emission to be $= 2.7 \times {10^9} \times 1{\mathrm{kg}} \times 1.835 \times 365 = 1.8 \times {10^{{12}}}{\mathrm{kg}}$.

Ref. a: SI Sohel, P Rana, and Syma Akther. Linking biomass fuel consumption and improved cooking stove: a study from Bangladesh.www.worldenergy.org/doments/congresspapers/65.pdf

Ref.b: gtz/HERA-Household Energy Programme. energy for cooking in developing countries, chapter 15, p. 419. www.iea.org/publications/freepublications/publication/cooking.pdf

Ref.c: Rupert Oliver Forest Industries Intelligence Ltd for AHEC. Carbon factor of forest wood. A preliminary assessment of the carbon foot print of American hard wood Kiln dried lumber supplied to distribution in the European Union. 4 March 2010