Achievement

Constructing our own table-top solar power beaming demonstration unit took quite a bit of work by a team of several people. From the Moon Society, Vice-president Charles F. Radley, and Chairman of the Board, R. Scott Gammenthaler, and Space Frontier Foundation member Phil Mills took the lead. But of course, this effort would never have been undertaken without the conceptual design at right above from USAF Colonel Peter Garretson. Thanks, Peter!

Our unit was finished in time for a grand debut at the National Space Society's 2008 International Space Development Conference in Washington DC, the weekend of May 29th- June 1st, 2008.

The unit has been displayed several times since, at the New Space Conference in Washington DC., and at two conferences in  Orlando, Fl (including ILEWG 2008 and ISDC 2009), and at the International Symposium on Solar Energy from Space in Toronto, Canada, September 10, 2009.

Our Follow-on Project: An Online Kit to help other groups to produce additional demo units

One unit is not enough! We need a lot of people to see this or similar demonstration units, if we are going to affect public opinion at large in the direction of support for Space-Based Solar Power as the most attractive and effective way to solve the World's increasing energy problems, in a way that respects and protects Earth's environment.

Thus, it has been our goal from the outset to produce an "Online Kit" so that many other groups could duplicate, and perhaps improve upon, what we have done. More Demo Kits in more hands means more people will have the opportunity to see one.

The Challenge

The Moon Society's desktop Solar Power Beaming Demonstration model was designed as one of a kind. Thus, it has taken some time to produce a set of diagrams, instructions, parts source lists, etc. that would allow others to closely replicate the model we produced, or to improve upon it.

A problem quickly became apparent with our very first assembly of the unit at ISDC 2008, and at every occasion since. The non-working superstructure if very gossamer and susceptible to damage in handling. We are constantly making quick repairs with Duck tape, Scotch tape, adhesive, and epoxy. This is our primary motive in encouraging others to re-brainstorm the design and come up with easier and more robust designs and components and assembly methods.

Common Problem 1: the solar cells are easily dislodged from the fishing line net of the Main Mirror Assemblies. Experimentation with alternative adhesives is recommended - see the advice on the Main Mirror Assembly Page.

Common Problem 2: the 2" long 1/8" diameter aluminum tubes mounted on the Solar Solar Disk (4) and on each of the Main Mirror Assemblies (4 each) at an angle are glued in place and easily knocked off. Experimentation is recommended with drilling holes of the proper diameter and at the proper angle into the Main Mirror Assembly frame and the Blue Solar Disk frame so that these tubes can be inset not only to secure their adhesion, but to secure their proper angle. We have tried "fast epoxies" which are no where near fast enough or solid enough. Recommend Plumbers Epoxy which gets rock hard in a hurry and sets for life (if not forever, i.e many lifetimes)

We further recommend securing a small surplus of these 1/8" diameter aluminum tubes.

We encourage others to try new materials, new ways of assembly, and to otherwise improve upon this "Mark I" design. But please send us the information on what you have done so that we can pass improvements on to others. We need more of the best iterations we can collectively produce.

Non-working parts

While our unit was designed to show the entire system, from power collection to power delivery, we chose to limit the operations to be demonstrated to the part that transmits collected solar power to the rectenna. The rest of the unit was to be just for show. Thus the two outrigger solar arrays do not actually absorb power and reflect it to the transmitter. That is all known technology, fairly well understood by the layman. That concession greatly simplified model making.

The parts used for this "superstructure" are thus not critical either as to material used or as to operability. This simplifies things for those who would duplicate or perhaps improve upon what we have produced. Our instructions, blueprints, and source information will then be just a guide. Those who wish to build their own SPB-Demo unit, can either use similar materials and parts or substitute at their convenience.

Working parts

Our previously published Project Status Page contains a record with ample illustrations of the electronic parts of our Desktop Solar Power Beaming Demo Unit.

NOTE: As the board which will light up three small diodes to demonstrate reception of the signal through the power beam, costs more money to have made one at a time, the Society has purchased several, for resale at a fraction of the one-unit price, which makes your task easier.

If you have any questions about these parts, how to obtain or produce them or test them,  please email Charles F. Radley at charles @ stratowave.com (this link is not active. When pasting it into your email program, remove the spaces to either side of the @ symbol.)

FCC Guidelines for Human Exposure to Radiofrequency  - added September 17, 2010

http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet65/

Here is an FCC standard which is entitled "Guidelines" but which might be legally enforceable to both controlled and uncontrolled situations involving the general public:

OET Bulletin No. 65 (August 1997)

Evaluating Compliance With FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields

Also see information at this website: The info is at this web link:

http://groups.google.com/group/wireless-power-transmission

There are multiple layers of regulation.  Pay particular attention to the so called "ISM" bands (Industrial, Scientific and Medical) which are suitable for power beaming.   Some of the ISM bands overlap with amateur bands, which are good candidates if you have an amateur
license.

Limits of Electronic Components and Allowable Power Range (from R. Scotty Gammenthaler)

The demonstrator was designed to show that power can be transmitted by wireless. 

While the receiver runs at reasonable efficiency, the transmitter is an off-the-shelf device that was not designed with efficiency as a goal.  (It is intended as an amplifier for wireless LAN communications and produces about 1 watt output power.) 

Also, the antenna coupling efficiency is not very good because of the limitations of a small-scale device. 

Finally, FCC safety regulations limit the amount of power that can be used without safegaurds.

The net result of all these limitations is that it is probably not feasible to build a demo system that can be used within FCC limits that operates at a higher power level than our system unless the system is used in a controlled environment that limits human access. 

Our system produces about 150 milliwatts output power (8 volts DC at 15 to 20 ma) and while it might be possible to increase this a little, I don't think it will be possible, for example, to light up a model railroad and city set.

There is quite a bit of documentation in the spb demo project area  at
http://www.moonsociety.org/projects/spb-demo/project-status.html
that discusses design and system issues.  I would encourage anyone interested in improving on our system to first review this material.

Shipping & Storage

Choosing and/or designing shipping and handling containers was not a part of the original project, but has been given considerable attention since then as the unit is fragile and susceptible to damage if not packaged appropriately. Our packaging system has improved quite a bit, but is not yet perfect.

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