Continued from CONTOURS: New, Energy-Efficient Technologies, Part 1:

This week, we examine some very advanced technological developments on the active technology front that may potentially lead to more efficient and cheaper photovoltaic panels.

For decades there has been talk about how photovoltaics could explode onto the mainstream market once they crossed the performance and efficiency coefficient. Once their efficiency, or output power v. input power of sunlight, overtakes the levels of energy put into manufacturing them, we are headed into positive territory for more widespread applications. This, of course, assumes that one of the main impediments to  general applications is first cost. So the problem is being approached from two directions: getting first costs down and increasing lifecycle efficiency.

Toward this end,  two teams at MIT, one in the Physics department, and one in Engineering, have both been using a similar overall approach that seeks ways to overcome the limitations of traditional PV panels. Specifically, they have been looking closely at a branch of material science dealing with what are called metamaterials. These are basically artificial materials that exhibit supranatural properties. In other words, can PV panels perform better by exceeding natural material constraints?

What the two teams have been discovering is that such metamaterials might be the key to pushing PV into the positive efficiency range and thus changing the PV game for the better. 

PV panels, as we know them, are not very efficient . In fact, “devices that turn sunlight into heat and then into electricity in this way do not get much warmer than boiling water when they are exposed to direct, unconcentrated sunlight. The reason is that at temperatures significantly higher than this the laws of thermodynamics dictate that they shed heat as fast as they absorb it.” The result is that the conventional materials used in today’s PV panels are only about 10.5% efficient. What’s more, they’re expensive. Which is why so many clients are reluctant to use them, and coincidentally, why passive technologies are often perceived as good alternatives. 

However, these researchers think they have a way of not only boosting efficiency, but in so doing they will also hopefully reduce material and production costs. The metamaterials used by both teams include tungsten thin films, phototonic crystals, and electromagnetic materials. 

The Physics team employed tungsten thin films and phototonic crystals to limit the problem of radiation exchange. In the process, they demonstrated that not only did using these metamaterials increase efficiency to 37%, but that they could make a cheaper panel because less material was needed. 

The Engineering team began with a different premise based on the idea of using electromagnetic metamaterials and photonic crystals to transform devices normally used for capturing waste heat. Electromagnetic metamaterials have a lower density so they can potentially fabricate a lighter smaller PV panel that will perform better than the current models. But more importantly, given their supranatural structure, they can convert a wider range of sunlight into power. In short, the combined materials make them more efficient and smaller, lighter and hence cheaper to make. 

The key, of course, is when will these two innovations come to market? Well, that is what these teams are trying to determine. For now, however, they are still in the research phase and they are producing a lot of peer-reviewed papers to illustrate their findings. Hopefully in the not-too-distant-future, we will begin seeing feasible, marketable prototypes. 

Whether passive or active, the determining factor for getting to that point where a sea-change in applications can come about is based on this type of front-loaded research and methods of institutionalization--political and economic. Even then, when these super PVs do come online, to confuse availability with widespread, institutionalized use is to conflate two very different issues. Making them available will be half the battle.