DIY Solar & Steam power via Fresnel Lens and Paraboloid

The Fresnel Lens:

The Fresnel lens is named for its inventor, French physicist Augustin Jean Fresnel. Fresnel studied light and optics in the 19th century.

If you have ever looked at the lens of a magnifying glass, you know that it is thick in the middle and tapers down to nothing at the edges. In other words, it is shaped like a lentil, which is where the word lens comes from. It would not be very easy to make a big magnifying glass lens for your RV because it would be thick, heavy and hard to mount.

The thin piece of plastic you are using is called a Fresnel lens. It is flat on one side and ridged on the other. Fresnel lenses we first used in the 1800s as the lens that focuses the beam in lighthouse lamps. Plastic Fresnel lenses are used as magnifiers when a thin, light lens is needed. The quality of the image is not nearly as good as that from a continuous glass lens, but in lots of applications (like your RV), perfect image quality is not necessary.

The basic idea behind a Fresnel lens is simple. Imagine taking a plastic magnifying glass lens and slicing it into a hundred concentric rings (like the rings of a tree). Each ring is slightly thinner than the next and focuses the light toward the center. Now take each ring, modify it so that it's flat on one side, and make it the same thickness as the others. To retain the rings' ability to focus the light toward the center, the angle of each ring's angled face will be different. Now if you stack all the rings back together, you have a Fresnel lens. You can make the lens extremely large if you like. Large Fresnel lenses are often used as ­solar concentrators.

http://www.youtube.com/watch?v=A_AFnW1bZL8
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Parabolic Mirror; aka Paraboloid:

A parabolic mirror is a specially shaped object designed to capture energy and focus it to a single point. It may also work as a way of distributing energy from the focus point back outwards. Parabolic mirrors may also be referred to as parabolic dishes or parabolic reflectors.

Parabolic mirrors are a specific type of paraboloid, known as a paraboloid of revolution. This is a type of elliptical paraboloid that is rotated around its axis and may also be referred to as a circular paraboloid.

One of the earliest uses of the parabolic mirror was in Isaac Newton's reflecting telescope of the 17th century. By using a parabolic mirror, reflecting telescopes correct some of the aberrations which existed in older refracting telescopes. With the use of parabolic mirrors, however, some other problems are introduced. This includes a problem called coma, which exists in all telescopes using parabolic mirrors. Coma causes any objects viewed through the telescope which are not at the center of the field of vision to look slightly wedge-shaped. The further outside the field they are, the more distorted they appear.

Parabolic mirrors are usually made of a low expansion glass, similar to Pyrex glasses. The mirrors are kept as fine as possible to reduce distortion in the image. The processes used to produce extremely high-end parabolic mirrors can take months and cost thousands of dollars.

Aside from amateur telescopes, many people have interacted with a parabolic mirror in the form of a popular optical illusion toy. This small pans has two parabolic mirrors attached to one another and a hole in the top to allow placement of a small object. When an object is placed between the two parabolic mirrors, it appears that the object is in fact resting in the air a few inches above where it actually is.

During the world Olympics, the flame used for the Olympic torch is lit using a large parabolic mirror. This parabolic mirror collects ambient sunlight and focuses it to an intensity sufficient to ignite the torch material.

A most likely apocryphal tradition has it that parabolic mirrors have been used in the past as a way of gathering sunlight to spontaneously ignite enemy ships, or to heat up the armor of the enemy to a point where they were forced to remove it.

http://www.youtube.com/watch?v=qbKtXdD5CBI
http://www.youtube.com/watch?v=Ij1YvJT5tLQ
http://www.youtube.com/watch?v=4AsnE9kwyDw

http://www.greenpowerscience.com/