Inexpensive Solar Collector


I was reading an article in Popular Mechanics about solar energy when I came up with this idea.   Solar panels are generally made out of relatively rare and expensive materials and have other drawbacks that, given our current technology, keep solar panels from being economically competitive with other methods of generating electricity such as coal and natural gas.  While it is possible that improvements in solar panel technology may change this in the future, a more cost effective method of converting sunlight to electricity would reduce our toll on the environment.  This is where solar collectors come into the equation.  Is it possible to gather sunlight in such a way that could be used to generate electricity and be cheaper than current methods?

A company in New Mexico is working on reducing the cost of creating energy from sunlight. reflecting light onto a small area.  The energy harnessed in turn powers a Stirling Engine which then creates electricity  (pictured on the left).  As I read the article I was impressed with this different approach to the problem.  Honestly, I didn’t even know how a Stirling Engine worked.  They could really be onto something here.  The article mentioned the company has worked out all the technological issues, now they are focusing on reducing the cost of building these devices.   The article noted that each of these dishes can power roughly 12 houses with electricity.

So I thought about it for a while, and I think there is a much less expensive way to achieve the same results.  Here is how I would build a cheaper solar collector:

Step one: Acquire an OLD satellite dish.  Not one of the 18 inch models that are currently in use.  You need an old school dish that is several feet in diameter.  Here is a good example:

Step Two: Acquire/buy several hundred blank CDs.  Back in the day you could ask AOL for as many as you wanted, but I’m not sure that would fly today.

Step Three: Line the entire inside of the dish with CDs, with the exception of the very center, making sure the sure the most reflective side is facing up.  This will allow for the sunlight to be concentrated at the focal point.  Attach the CDs to the dish with bolts (in case they need to be replaced in the future), or Lee press on nails (if that’s all you have in your purse).

Step Four: Place a large sized convex mirror, maybe one from a truck side mirror, at the focal point of the dish.  This is made easier by using the existing support structure of the dish.  The purpose of the mirror is to focus the light back onto the exact center of the dish.  (This will be where the engine is eventually placed).  Finding a mirror with the correct curvature could take some work.

Step Five: Build a level circular base out of concrete.  The diameter should be at least as large as the diameter of the top edge of the dish.

Step Six: Place the Sterling Engine in the center of the base.

Step Seven: Build a support structure for the dish.  When finished, the base needs to be able to rotate freely in two dimensions in order to track the sun.  It also must be able to accommodate the engine in the center of the dish that keeps the top of the engine at the center of the dish.

Step Eight: Build a mechanism for tracking the sun.

So how is this method better than what has already been built?  The main improvement is moving the engine from the focal point of the dish to a stationary position underneath the dish.  This reduces overall center of gravity and complexity since only the dish itself is moving.  It also shades most of the engine, which relies on temperature differentials to produce energy.  Also, the smaller scale would allow individual homeowners to build this device from a kit to provide some or all of their home’s energy needs.

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