Solar energy is a no brainer for most people. However, it has a reputation for being expensive and not very efficient. At the heart of these two facts is silicon. This element and others that go into solar panels are rare and difficult to work with. Scientists are now closer to finding replacements for silicon and improving the efficiency of solar panels. This could lead to the mass produced plastic solar cells and make solar power a global energy resource.
The key to a less expensive solar panel is to replace the silicon with a more common element. Silicon makes up 25.7% of the Earth's crust and is the second most abundant element in the crust, after oxygen. However, solar panels require pure silicon and these are rarely found in nature. Today solar panels are not exactly the most efficient in taking light energy and producting electrical energy.
Besides the finding less expensive materials, scientists and engineers are working to get more electricity out of solar panels without silicon.
Solar sandwich: Hold the silicon, please
By layering plastics and other materials, Canadian researchers are extracting electricity from the sun without expensive silicon. The Canada’s National Institute for Nanotechnology (NINT) and the University of Alberta have engineered an approach that is leading to improved performance of plastic solar cells (hybrid organic solar cells).
Jillian Buriak, the NINT principal investigator uses a simple analogy to describe the approach:
“Consider a clubhouse sandwich, with many different layers. One layer absorbs the light, another helps to generate the electricity, and others help to draw the electricity out of the device. Normally, the layers don’t stick well, and so the electricity ends up stuck and never gets out, leading to inefficient devices. We are working on the mayonnaise, the mustard, the butter, and other ‘special sauces’ that bring the sandwich together and make each of the layers work together. That makes a better sandwich, and makes a better solar cell in our case.”
After two years of research, these Canadian scientists have, by only working on one part of the sandwich, seen improvements of about 30% in the efficiency of the working model.
Ultimately, their goal is to produce plastic solar cell material that ink-jet printers will make cheaply, quickly, and in massive quantities. if that happens, we coul find solar skins on cars and trucks and perhaps even entire buildings.
What if Solar Energy became the dominant globla energy source?
The Solar Energy Industries Association based in Washington, D.C., reported the photovoltaic market in the U.S. grew by more than 48% in 2007, and U.S. solar manufacturing grew by 74% in 2007. The U.S. currently ranks fourth in the world for installed solar power (behind Germany, Japan, and Spain). Solarbuzz, an international solar energy research and consulting company based in San Francisco, reported the photovoltaic industry generated $17.2 billion in global revenues in 2007.
While the industry growth has been impressive, one has to wonder whether it would be sustainable if solar became a global source of energy. The most popular solar materials in use today are silicon and thin films made of CdTe (cadmium telluride) and CIGS (copper indium gallium selenide). While these materials have helped elevate solar to a major player in renewable energy markets, they still suffer from manufacturing challenges. Silicon is expensive to process and mass produce. Furthermore, it has become increasingly difficult to mine enough silicon to meet ever-growing consumer demand.
Scientists at the University of California Berkeley evaluated 23 promising semiconducting materials and discovered 12 are abundant enough to meet or exceed annual worldwide energy demand. Of those 12, nine have a significant raw material cost reduction over traditional crystalline silicon, the most widely used photovoltaic material in mass production. Even thin films, while significantly less costly than silicon and easier to mass produce, would rapidly deplete our natural resources if solar energy became a global energy resource and had to scale to terawatt hours of annual manufacturing production. A terawatt hour is a billion kilowatt hours.
“It’s not to say that silicon won’t play a significant role,” Wadia added, “but rather, if our objective is to supply the majority of electricity in this way, we must quickly consider alternative materials that are Earth-abundant, non-toxic and cheap." These nine materials can help us realize our goals more rapidly.”
The California team showed iron pyrite is several orders of magnitude better than any alternative in terms of both lower cost and greater abundance. In the report, the team referenced advances in nanoscale science to argue they could offset the modest efficiency losses of unconventional solar cell materials by the potential for scaling up while saving significantly on materials costs.