Solar Power Without Solar Cells

Solar power station graphic courtesy Scientific American

As most people know, electromagnetism manifests as both electric fields and magnetic fields. Yet the fact that the magnetic effects of (sun)light can be used to make an “optical battery” is one that even Michigan University’s (MU’s) Stephen Rand, a professor of applied physics, admits is counter-intuitive.

“We have been taught that this doesn’t happen,” Rand said recently, referring to the magnetic effect of light. “That’s why it’s been overlooked for more than 100 years.”

And that century-long gap between observation and realization – that intensely focused sunlight generates enormous magnetic effects – is what may propel this newest discovery to the forefront of solar power, because in fact sunlight may not need high-temperature superconductive elements like silicon, copper and gallium to achieve electricity generation.

In fact, Rand and colleagues, working at MU’s Electrical Engineering and Computer Science (EECS) Division, have discovered that the magnetic component of sunlight, delivered at the right intensity through a non-conductor like glass, is 100 million times greater than expected – a discovery they intend to shelter via patent protection.

What their discovery does, in essence, is bypass the photon absorption/charge separation aspect of solar. In other words, instead of solar cells taking in photons from sunlight and converting them to energy in the form of electrons, the direct-to-magnetic effects of focused light provide a sort of “instant” energy without the charge separation phase.

Of course, in order for sunlight to achieve this energy state, it has to be concentrated to 10 million watts per square centimeter (W/cm2). On its own, the sunlight reaching earth is only 0.136 W/cm2. In space, sunlight falling on planets like Venus (unshielded by an atmosphere, and second closest to the sun) is about 26 million W/m2, which is why space-based solar power is getting so much press lately.   

This intense focusing of (sun)light is also the principle behind concentrated photovoltaics, or CPV, and in fact both Rand and doctoral student William Fisher are engaged in the fields of nonlinear optics, photonics and electromagnetic energy. In fact, in the summer of 2011, the team plans to test its hypothesis using laser light first.

Eventually, if proven correct, their discovery could not only make solar cheaper by eliminating the rare earth minerals and the need to “fabricate” them, but could achieve efficiencies of 10 percent using nothing more than lenses to focus light and a fiber to guide it.

Current solar efficiencies in the field range from 14 to 17 percent for monocrystalline silicon cells to 5 to 7 for amorphous (a-Si, or gaseous deposition) silicon, with polycrystalline silicon falling nicely in the middle.