This week was crucial in terms of finalizing the design we wanted to use and gathering all the materials to build that design. We decided to make the shape of the solar concentrator a dome shape, with wood sticks being angled less and less steep until it reaches the horizontal at the top, and then steeper again to reflect the other side. The materials we got were three 8 foot long pieces of wood for the main structure (each cut into two pieces as shown below, ultimately making six 4 foot pieces of wood), eight thin 3 foot pieces for internal support, and two thin 2 by 4 feet pieces of plywood for external support.
The rough dome-shaped design, made with the wood purchased, is shown below.
Below is some research on the lenses used in this design:
Fresnel Lens
- Little light is lost due to absorption because the lens itself is very thin.
- A Fresnel lens works by have many grooves in place of a conventional lens. These grooves act as reflecting surfaces that bend and focus the light.
- Have optical uses and magnification uses.
- Can also be used for projection and displaying images as a screen
- Linear
- Long length-wise beam
- Generates less heat
- Less chance to be damaged
- Spot
- Can set a lower focal length
- Can melt metals
- Is more focused on a point
- Can be damaged by evaporating water
Focal Length
- Can be calculated with lasers
- The Fresnel lens that we bought had a shorter focal length then was advertised
- Advertised as 30 cm. Was measured in the 20s.
- 30 cm advertised focal length
- 0.3 mm groove pitch
- Groove pitch determines the diffraction
- 0.4 mm thickness
- http://www.edmundoptics.com/optics/optical-lenses/fresnel-lenses/fresnel-lenses/2040
- http://www.greenpowerscience.com/LINEARSPOT.php
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