Solar cookers & dryers part 2
- 1. Energy & Environment This PowerPoint presentation is developed and created By:
- 2. When you annotated your drawing did you think about these ways of converting the 30-40°C heat into 100 °C heat: • Concentrating the sun rays • Converting the light energy into heat energy • Trapping heat • Using certain materials for their beneficial properties. • Using the greenhouse effect
- 3. Lets look at how a solar cooker can concentrate the sun rays: 10% 10% 10% 10% 10% 10% 10% 10% 100% 10% 10% 10% 10% 10% The suns rays are What is hotter than one ray scattered from the Many rays! So we need to concentrate these rays to get more source heat But how can we concentrate the rays? We can do this by reflecting the rays Name a material that is good at reflecting: Mirrors (or any other reflective material) ________________
- 4. Now let’s look at how a solar cooker can convert light energy into heat energy: The light energy needs to be absorbed, it is then converted into heat energy. What colour is good at absorbing energy? Black __________ Light colours reflect light Dark colours absorb light, it is then converted into heat. So rays are reflected So no rays are reflected
- 5. Let’s now look at how a solar cooker traps heat. A solar cooker traps heat by preventing convection Convection is when hot air particles travel to cool areas Warm air Hot air Cold air
- 6. Finally lets now look at how a solar cooker can use the greenhouse effect to convert the 30-40°C heat into 100 °C heat. The greenhouse effect is when light energy passes into a glass container and then is not able to leave. This trapped energy builds up and is converted into heat energy. Glass allows visible Glass blocks thermal light to pass through radiation from escaping.
- 7. Warm air 10% 10% 10 Hot air % Cold air Trap heat Concentrate rays Convert light energy to heat energy Greenhouse Effect
- 8. It’s now time for our second activity!
Editor's Notes
- #4: Concentrating sunlight: Sun’s rays are scattered from source, need to concentrate for higher temperature & heat. Mirrors or reflective metal is used to concentrate light and heat from the sun into a small cooking area.
- #5: Converting light to heat: Sunlight heats the pan. A black pan will absorb almost all of the sun's light and turn it into heat. Solar cooker tried to absorb maximum heat from sunraysWhy? How does this work?Complex: Due to the atoms that make up the colour. Atoms in the colour black take in energy and so heat up. This is called Light absorption??