Energy nanotech: thinking small to solve a big problem

Image courtesy BP

While photovoltaics - the generation of electricity from light - currently comprises only 0.1 per cent of the world energy capacity, it is expected to take on a much more significant role in the near future.

Solar energy is perhaps the only long-term solution, David Carlson, chief scientist at BP Solar, told a recent energy nanotech meeting at the Massachusetts Institute of Technology. “I think we’ll see the peaking of oil and natural gas sooner than most of those in the fossil fuel industry think,” he said. “By 2035 photovoltaics could produce about 10 per cent of the world’s electricity and play a major role in reducing CO2 emissions.”

The photovoltaics market has been growing at about 35 per cent annually over the past few years, Carlson said. “A lot of revenue is being generated by incentives by the governments of Japan and Germany,” he added. Analysts put the total solar market at $8 billion to $10 billion now, with expectations of growth to between $30 billion and $40 billion by the end of the decade.

Attracting venture capital

Although the market is in the early stages of development companies including Konarka Technologies, of Lowell, Massachusetts, as well as Nanosys and Nanosolar, both of Palo Alto, California, have caught the eye of the venture capital community with their new light-weight, flexible polymer photovoltaic products.

Nanosolar in June completed a Series C financing for more than $75 million that included existing investors such as MDV-Mohr Davidow Ventures and Mitsui of Japan, as well as new investors Swiss RE and Christian Reitberger, the original backer of Germany’s Q-Cells, one of the largest independent silicon cell photovoltaic manufacturers in the world.

And in February, Konarka raised $20 million in venture financing led by 3i, plus existing investors including Chevron Technology Ventures. That adds to the $60 million in funding since the company started in 2001. Previous investors include Silicon Valley Bank, Zero Stage Capital, the École Polytechnique Fédérale de Lausanne, Electricité de France and the Massachusetts Green Energy Fund.

Konarka also acquired Siemens AG’s organic photovoltaic research activities and its team of scientists in 2004. It also has a partnership with Leonard Kurz GmbH & Co. for printing technology.

Konarka makes polymer photovoltaic products called Power Plastic that come in a roll. It already has begun producing hundreds of feet of the product, and is beginning to ramp up manufacturing, said Stuart Spitzer, vice president of materials and engineering.

The advantages of the plastic are that unlike silicon solar cells, it is flexible and can be cut to length, is low cost, lightweight and versatile. Spitzer said the material also is sensitive to low light, so it can produce from 5 to 20 per cent more energy than other technologies. “It collects more power in the early morning hours than other technologies,” he said.

In Europe, Germany has led in the solar cell and alternative energy fields, backed by government and industry support for such efforts. Large silicon solar cell maker Q-Cells recently said it would invest about €7 million into Swiss company VHF Technologies (trading as Flexcell). The money will be used to industrialise a new thin-film photovoltaic technology on Flexcell’s production line in Yverdon-les-Bains, Switzerland.

Nanotechnology could make solar the number one

The ultimate goal of solar energy research is to have the average cost of solar energy come closer to that for traditional fossil fuel sources, which is $1 per watt today. According to The Energy Foundation, the current cost of solar energy is between $4 and $5 per watt, and that for nanotech solar panels is estimated to be $2 per watt.

“Energy is the one of the greatest challenges of the century," said Claude Canizares, a professor of physics at MIT. "We need significant breakthroughs in science and technology. The promise of nanotechnology provides fertile ground for such breakthroughs.”

Some of those advances include nanotechnology-based solar photovoltaic devices and methods for making energy nanotechnology devices, such as work being done in the lab of MIT associate professor of electrical engineering and computer science Vladimir Bulovic, to fabricate quantum dot photovoltaics using a microcontact printing process.

Bulovic said nanotechnologies such as nanodots and nanorods are potentially “disruptive” technologies that could cause a major switch in a primary energy source and potentially be more efficient than the silicon used in most solar energy devices today.

MIT has been proactive in energy research, having set up the Energy Research Council in June 2005 at the behest of MIT President Susan Hockfield. The council released its first report recently, calling for an energy-focused lab or research centre to be established within five years. The report was compiled by 16 academics at all five MIT schools.

Energy companies seek new technologies

Industry has looked to universities for new technologies. BP is one of the major energy companies putting money into alternative energy research. It has two major projects in house and is funding 10 more externally.

One of the major projects is a five-year endeavour started with Imperial College London, UK, in January 2002 and funded at $300,000 per annum, BP Solar’s Carlson said. The aim is to develop organic solar cells made of polymers rather than silicon, and to have such cells operating at 6 per cent conversion efficiency beyond 2006. The ultimate aim is to have the efficiency of solar modules exceed 20 per cent in the next decade. Silicon makes up 90 per cent of the photovoltaic business currently.

BP recently teamed up with the California Institute of Technology in a multi-million-dollar research program focused on a new way to produce solar cells that could make the cost of solar electricity more competitive and the cells themselves more efficient.

For the initial five-year period the collaboration will explore a concept of growing silicon by creating arrays of nanorods. Today’s methods involve casting ingots and cutting silicon wafers, which means some silicon is wasted. Nanorods are small cylinders of silicon that can be a hundredth the width of a human hair and that would be tightly packed in an array, much like bristles in a brush.

Such a solar cell should be able to absorb light along the length of the nanorods, collecting the electricity generated by sunlight more efficiently than in a conventional solar cell.

“Nanorod technology offers enormous promise. However, like any new technology, challenges remain to make it commercially viable at scale,” Lee Edwards, president of BP Solar, said in a statement when the deal what announced.

At Caltech, two scientists will be involved in the project: Nate Lewis, professor of chemistry and an expert in surface chemistry and photochemistry, and Harry Atwater, professor of applied physics and materials science and an expert in electronic and optoelectronic materials and devices. In addition, eight postdocs and graduate students will work on the project.

“Nanotechnology can offer new and unique ways to make solar cell materials that are cheaper, yet that could perform nearly as well as conventional materials,” Lewis said.

Atwater said that nanostructures in photovoltaic cells must significantly outperform current silicon technology in the cost per watt, and that the timeframe for research in the area already has shrunk to 15 years because of the need for alternative technologies. "There is a 15-year time scale for academic research. The question is can we develop a [nanotech] photovoltaic technology that is scalable to the terawatts range," he said. The United States currently uses 3 terawatts of power a year compared with a total of 13 terawatts for the entire world. That translates into 5 per cent of the world’s population using 25 per cent of the energy.