Solar Cookers in the Environmental High School Daniel Feuermann Hezi Yizhaqcooking-001.htm Solar Cooking A project within the Physics curriculum: Stages: Knowledge Design Construction Measurement Solar cookers: Only for refugee camps? Health issue (respiratory problems) Safety for women (wood gathering) Time for other occupation (teaching, small business) Energy savings, quality of cooked food, Bedouin society: environmental issue Modern society: why not? If it is possible. The box cooker: Simple design, Requires Alufoil, cardboard boxes, glue, some transparent glazing, newspaper for insulation, scissors, knife. Some commercial examples Parabolic cooker Lahsa, Tibet Box cooker with reflectors Village cooker Panel cookers, simpler than box cookers Radiation outside the atmosphere: The 1/R 2 - law Distance sun-earth: m Diameter of the sun: m The radiation is then: [(1.39/2)/149.5] 2 =1351 W/m 2 sun r R=149.5*10 9 m earth Surface temperature of the sun 5762K black body radiation: T 4 = 5.67*10 -8 (5762) 4 = 62.5*10 6 [W/m 2 ] Electromagnetic radiation Solar radiation Diffuse and direct radiation Direct radiation: W/m 2 Diffuse radiation: W/m 2 Solar radiation measurement Radiation on a horizontal surface Transmittance of non-absorbing glass covers Bougers law: where K is the extinction coefficient L is the optical path length g is the absorption coefficient L = d/cos t where d is the thickness of the layer Typically K=432 m -1 For example if K=32, d=0.005m, and normal incidence g = 0.15 i.e., 15% of energy is absorbed. Parabola y = a x 2 f = 1/4a tan( /2)=D/4f D Geometry of the parabola Cross section Leaves to construct the parobala Physics 1. ? . 2. ? 3. ? 4. ?