Appendix D - EMP - Protect Family, Homes and Community

EMP - Protect Family, Homes and Community

This is the beginning of Appendix D of the 3rd edition of EMP - Protect Family, Homes and Community.

This Appendix will be an online extension of the book. The book was written for engineers, community planners and the general public. With such a broad target audience, it was impossible to include a fraction of the details that we would have like to have included. Anything close to being a complete work on this subject would include several volumes with many thousands of pages. By including this online Appendix D, I hope to be able to fill in some of the gaps.

Shielded solar panels constitute a major part of the plan outlined in the book along with shielding on all auxiliary solar components. Ideally, these shielded solar panels should be made by the solar panel manufacturers. There are solar manufacturers who appear to be willing to do this, especially for consolidated orders for multiple residential houses or commercial buildings. It is also possible to make a shielded home solar panel system as a do-it-yourself project, although this requires time and strict attention to detail that really should be done at the factory.

A major problem with the book has been that, in some respects, it was written too soon. It is better, though, to be too soon than too late. The problem has been that suppliers of both thin-film solar panels and high-transparency wire mesh have been terribly slow a getting their products to the consumer market. Thin-film solar panels using cadmium telluride (CdTe) are important because any wire mesh shielding will typically block ten percent or more of the incoming solar light. This reduction in sunlight hitting the solar cells affects the output of CdTe solar panels significantly less than with conventional silicon solar panels.

CdTe solar panels have been in mass production for many years. The problem for the individual consumer is that the primary maker of CdTe solar panels, First Solar of Tempe, Arizona, has been selling its solar panels exclusively to large utility-scale solar projects. This may change soon.

A similar problem has occurred with high-transparency wire mesh for shielding the front of the solar panels. This wire mesh has been produced for decades. The problem is that the principal user of high-transparency wire mesh has been military and government contractors, who are willing to pay a very high price for a product that costs very little to make. Most sellers of high-transparency wire mesh literally don't know how to sell their product to an individual homeowner.

Nevertheless, a do-it-yourself EMP-protected home solar installation is possible given enough knowledge, diligence and determination. There are some smaller distributors of solar components that cater specifically to the do-it-yourself individual homeowner.

Using wire mesh for electromagnetic shielding is something that has been done for decades. Both the theory and practice are well known, and it is a fairly straightforward process for an electromagnetics engineer to design a screen room with more than 100 db. of shielding at the relevant EMP frequencies. The complication for solar panels is the necessity for the shield to have a very high transparency to sunlight. The wire mesh ordinarily used in screen rooms will block more than half of the sunlight going to a solar panel. This leads to the requirement for special high-transparency wire mesh. Much of the "high-transparency" wire mesh currently available is designed for applications where 50 db. of shielding is adequate. Although 50 db. is useful for many shielding applications, better shielding is desirable for protecting solar panels from EMP. A higher level of shielding using a high-transparency wire mesh is well within the scope of current technology.

A starting point for shielded solar panels is the use of high-transparency stainless steel mesh covering the front of the panel and bonded securely to the frame of the panel. Stainless steel is the material most readily available in a high-transparency mesh because a high-transparency mesh is necessarily made from very fine wires. These very fine wires are easily subject to deformation and distortion. Stainless steel is much less subject to this deformation than either copper or aluminum.

Since solar panel frames are commonly made of aluminum, this would be the best metal to use for a high-transparency mesh shielding in a manufacturing environment. Aluminum screen would also give a better shielding effectiveness at most frequencies. The use of aluminum mesh, however, is something that is best left to the solar panel manufacturers since high-transparency aluminum mesh is easily deformed compared to stainless steel. This is because the property of aluminum that causes metal mesh to become permanently deformed is nearly three times as great for aluminum as for stainless steel. Factories are much better equipped for the special handling of high-transparency aluminum mesh than the homeowner.

As soon as there is sufficient demand, EMP-shielded solar panels will become available from solar panel manufacturers. It is up to the individual homeowner and business owner to create this demand. If this demand does not occur, the results could be truly catastrophic on a scale that few of us can imagine.

The high-transparency stainless steel mesh, pictured above in front of a computer screen, is a 3-inch x 3-inch piece of 50 mesh stainless steel wire cloth. It is what is between the two strips of brown tape.

Stainless steel mesh is the only high-transparency mesh that is readily available to the individual purchaser (from suppliers such as TWP). The very thin high-transparency 50-mesh stainless steel mesh that is commonly available may not be quite adequate to meet the standard EMP specifications over some of the frequency range of interest for EMP protection. In the book, we recommend a 20 mesh (20 openings-per-inch) wire mesh.

The much thinner wires in the commonly available 50 mesh stainless steel wire mesh means that the shielding may be less than optimal, and (according to my rough calculations and also according to actual data published by one manufacturer) it may not meet the standard (80 db.) military specification over one particular critical range of frequencies. Even a very thin 50 mesh shield, however, is likely to protect against all but the most maximally effective EMP attack. Considering the fact that photovoltaic cells are not as sensitive to EMP as microelectronics, the 50 mesh shield is likely to be sufficient. It is difficult to say exactly what will be sufficient for solar panel EMP protection when solar cell technology is rapidly changing, and therefore the breakdown voltage of the solar cells is also likely to change.

One Chinese wire mesh manufacturer that sells products in North America produces stainless steel mesh that appears to be better than the commonly available 50-mesh shielding. One is a 16-mesh product with an open space area of 95 percent. The other is a 25-mesh product with an open space area of 88 percent. The 16-mesh product has such thin wires that I suspect that it would be so fragile that it would be very difficult to handle (in addition to being barely thick enough for adequate shielding at all frequencies). The 25-mesh product has wires that are 50 percent thicker than the 16-mesh product, and it should have adequate shielding effectiveness, although I have not seen the data. Communication with some of the Chinese manufacturers is very difficult, and I have not been able to find out any information on price and availability.

It should also be noted that wire mesh as coarse as 4 mesh is adequate for shielding an EMP pulse that conforms to the IEC standard EMP waveform. Coarser mesh sizes are not necessarily helpful for this application, though, since all of them that I have seen use much thicker wire and, therefore, have open area percentages of 76 percent or less. (In other words, a rather low transparency for solar panel shielding)

Bonding stainless steel mesh to the aluminum frame of a solar panel requires some special precautions due to the dissimilar metal problem. Making a good electrical connection between dissimilar metals tends to invite corrosion. Fortunately, both stainless steel and aluminum are much more resistant to corrosion than most metals. If the contact area between the aluminum and the stainless steel are carefully sealed to protect them from moisture, they are likely to last for a very long time without enough corrosion to affect the shielding. Adding a strip of solid stainless steel over the area where the mesh meets the aluminum frame would make a more solid connection between the mesh and the frame and would also make it much easier to seal the connection between the mesh and the frame against moisture.

Many people have exaggerated the dissimilar metals problem. It is a real potential problem, but it is also one that is easily handled with careful waterproofing techniques.

Moisture is also a major enemy of the solar cells themselves. Be very careful not to do anything to compromise the moisture resistance that is built into the assembled solar panel. Moisture is one of the major causes of solar panel failure.

Unless you live next to the ocean where your home may be subject to saltwater spray, overcoming the dissimilar metal problem in this application is fairly straightforward.

Since transparency is unimportant on the back side of the solar panel, many kinds of conductive wire mesh can be used for the back side. A much thicker bright aluminum screen may be used for the back side of the solar panel to avoid the dissimilar metal problem. If you have stainless steel frames on your solar panels, then nearly any stainless steel mesh can be used on the back of the solar panels.

The dissimilar metal problem can be avoided altogether when using stainless steel mesh simply by using panels with stainless steel frames. Such frames would cost more than aluminum, but stainless steel would be a better frame material overall. Some of the smaller solar panel companies that specialize in solar do-it-yourself projects for the homeowner make their own frames, and could provide stainless steel frames at an additional cost.

It is imperative that any solar power system be treated as a system. Every part of that system must be carefully shielded, and the shielding must be done in a way that the entire system as a whole is securely shielded. Wherever any wire exits the shielded system, or may in any way risk exposure to external electromagnetic fields, those wires must be subject to adequate filtering and transient suppression at the entry/exit point.

If you do not completely shield all of your house or building, then you must carefully define the shielded volume and insure that all wires penetrating that shielded volume have adequate transient protection at the point of entry into the shielded area. Do not forget to account for all of the wiring hidden inside of your walls.

The matters discussed above will be discussed later in more detail in subsequent books. The first of those more detailed books, EMP Protecting Housing and Solar, was just released in August of 2014.