Solar Cooker

Introduction Nowadays, popularity of solar cooker is widespread from Europe to Asia. Our group wants to find out what the structure of the solar cooker is, and how it works, so we do a project of solar cooker, in order to know these things.

Material Used Black paper Inside cotton Slide Rope (X2) Paper box(X2) Coke cans ： (wrapping the water container with the black paper) Metal foil

Application of physical principle This design aims ： 1.To absorb more sunlight from the Sun. → We use a rope to fix the top and the lower lid to make sure the angle of reflection and angle of incidence are the same. →To ensure that sunlight can reach the metal foil above. 2. To prevent heat loss by conduction →Outside the box, we cover the box with some black papers for better absorption of heat. →Inside the box, we use silver metal foil to cover the box. →we put some cotton under the aluminum can and in the space between the inner and outer box. Sun

Result of the experiment (1) Time Temperature Initial temperature 28 ℃ 5mins later 29 ℃ 10mins later 30 ℃ 15mins later 30.5 ℃ 20mins later 31 ℃ 25mins later 32 ℃ 30mins later 34 ℃ 35mins later 35 ℃ 40mins later 37 ℃ 45mins later 39 ℃ 50mins later 39 ℃ 55mins later 40 ℃ 60mins later 41 ℃

Improving the performance 1.We place a plastic colourless lid on the solar cooker. →To reduce heat loss to the surroundings by convection. →To produce a greenhouse-like environment. 2. We use thicker paper boxes to construct the body of the cooker. →To reduce heat loss by conduction and convection. 3. We put the cotton wool in the solar cooker. →To reduce heat loss by conduction. 4. We paste some smooth metal foil onto the inner surface of the solar cooker. → the heat energy will be reflected more in our solar cooker. 5. We use a magnifying glass. → To focus the solar energy. 6. We wrap a piece of black paper around the water container. → To absorb heat more efficiently.

Result of the experiment (2) Time Temperature Initial temperature 23 ℃ 5mins later 25 ℃ 10mins later 26.5 ℃ 15mins later 28 ℃ 20mins later 30 ℃ 25mins later 32 ℃ 30mins later 34 ℃ 35mins later 35.5 ℃ 40mins later 37 ℃ 45mins later 38 ℃ 50mins later 40 ℃ 55mins later 42 ℃ 60mins later 44 ℃

Discussion 1.How can we use reflection to gather more solar energy? 2. What kind of materials should be used to construct the body of the solar cooker? Why? 3. What other measure can help to reduce heat loss by conduction and convection? 4. How can we make use of greenhouse effect to trap more solar energy? 5. How should the container of water look like? 6. When and how the solar cooker should be used to enhance its performance?

Conclusion To sum up, in making this solar cooker, we know that there are many theories and principles behind. For example, we learnt that black paper can absorb more heat energy; using colourless plastic as a covercan trap the heat inside the cooker etc. We also have difficulties in division of jobs and in determining the time of completion of the project. However, we have lots of fun in the process!

Chan Sau Ling (3) Chan Wai Lan (4) Chung Wing Yin (6) Hui Siu Ki (7) Hui Siu Shuen (8) Members

Thank you!