Solar Parties Put Heads Together to Advance Renewable Energies

At this point in the photovoltaics industry, there is a wealth of variety in technologies - bulk crystalline silicon, including monocrystalline and multicrystalline varieties; and thin-film techniques based on amorphous silicon, CdTe, CIGS; and more. At this relatively pre-competitive stage in the game, PV players seem more interested in winning the war against fossil fuels than they are in beating out their PV neighbors, or even other renewable energy alternatives.

Aaron Hand, Executive Editor, Electronic Media -- Semiconductor International, 9/4/2008 8:48:00 AM

At this point in the photovoltaics industry, there is a wealth of variety in technologies — bulk crystalline silicon (c-Si), including monocrystalline and multicrystalline varieties; and thin-film techniques based on amorphous silicon (a-Si), CdTe, CIGS (with their own range of varieties); and more. At this relatively pre-competitive stage in the game, PV players seem more interested in winning the war against fossil fuels than they are in beating out their PV neighbors, or even other renewable energy alternatives.

The opportunities in PV are enormous, noted Jeannine Sargent, CEO of Oerlikon Solar, in an interview. The fight should not be bulk vs. thin-film solar, or solar vs. wind, but rather renewable energies vs. fossil fuels. “The focus needs to be to advance the thinking of the adoption of renewables,” she said, and how to ensure the world has a viable supply of cost-effective renewable energies.

Sargent’s sentiments have been echoed throughout the week at the European Photovoltaic Solar Energy Conference (EU PVSEC) in Valencia, Spain, with many discussions turning to concern about changes in government incentive programs, as well as the relatively low goals being set by the renewable energies sector as a whole. During the European PV Industry Forum, presented yesterday by the European Photovoltaic Industry Association (EPIA), there was further talk of the European Union’s Strategic Energy Technology (SET) plan to have 20% of the EU’s energy coming from renewable sources by 2020 — mostly geared toward the need and sure capability to reach far beyond that goal.

“We believe actual market potential is much higher,” said Anton Milner, CEO of Q-Cells and an EPIA director. He noted that 40-50 industry CEOs gathered the previous night to discuss the issue, using the short amount of time they have left (just until the end of September) to redirect the plan. “We must not allow marginalization of this industry.”

Winfried Hoffmann, a vice president of EPIA and past president, looked beyond 2020, talking about the PV potential to provide 60% of the world’s energy by the year 2100, with 75% coming from renewable energies. Although each renewable field would like to be the best, he said, they need to first come together and discuss how to deliver that 75%. “Then we can go and each one take the big steps forward.”

Hans-Josef Fell, a member of the German Parliament, said there needs to be an end to the huge subsidies for nuclear and fossil fuels, and it’s “high time” to establish an international renewable energy association. He called on attendees to urge their respective governments to join IRENA, which is founding in February 2009 to organize know-how transfer, education and research, capacity building, and political strategies on a global basis.

Celebrating progress

Celebrating a 30-year history, PVSEC has a strong tradition as a scientific meeting with non-competitive cross-fertilization, according to Daniel Lincot, general chairman of this year’s conference and research director at CNRS Institute for Research and Development of Photovoltaic Energy (IRDEP, Paris). Photovoltaics is a multicultural domain in all senses, he said, noting the coming together not only of chemists and physicists, experts in organics and electronics, but also the strong correlation between research, development and industry, as well as politics.

For years, conference organizers refused to run parallel sessions so that scientists from all disciplines would learn more about the advances in other areas. That has since changed, with parallel tracks running on advanced PV, wafer-based technologies, thin films, PV systems, system components and PV deployment. But the plenary sessions still offer opportunities to share significant developments on a broader scale with the larger PV community, since they do not compete with other tracks running in parallel.

For PV, in many ways it’s a celebration for the whole industry when one of its proponents crosses an important cell efficiency threshold. Lincot noted, for example, a plenary presentation this week by Spectrolab Inc. (Sylmar, Calif.), which detailed its relatively recent achievement of >40% solar cell efficiency. This was a significant achievement that is important for the whole industry, Lincot said. The achievement comes, along with work done with the National Renewable Energy Laboratory (NREL), by way of a thin-film multi-junction solar cell, which enables more efficient use of the photons coming from the sun’s spectrum. In the work presented by Richard King, Spectrolab used a three-junction solar cell based on III-V materials to achieve a cell efficiency of 40.7%, which has been furthered more recently by NREL to 40.8%.

Although c-Si cells currently hold close to 90% of the PV market, thin-film varieties are on the rise primarily because of their ability to come in at a lower cost per watt for the final system. However, they take a hit in conversion efficiencies, with some of the best ranging around 11% efficiency, while c-Si reaches into the low 20s. But one major advantage that thin-film technology has in the way of efficiency is its ability to make use of multi-junction technology. The theoretical limit of a single-junction cell is ~28-29% conversion efficiency, and for a tandem cell (two junctions) it’s ~38%. But a multi-junction cell could theoretically achieve >50% efficiency.

A single-junction cell is generally efficient at collecting the more energetic blue part of the sun’s spectrum, which produces a higher voltage, but less current makes it through as much of the rest of the spectrum is lost. Put simply, the addition of more junctions enables the collection of other colors in the spectrum by having a different bandgap at each junction — for example, catching the blue light at the first junction, green light at the second, and red light at the third in a more efficient way, and gathering more current within the thin films.

Spectrolab was able to cross the 40% threshold with a metamorphic multi-junction cell of GaInP/GaInAs/Ge. The company has continued to work toward a 50% efficiency goal, as have other companies in the industry.

Although some suppliers are holding certain process details close to their vests, the PV industry is still relatively young — where the semiconductor industry was perhaps 25 years ago — and is in a pre-competitive mode of sharing. It is an exciting time to be part of PV, with those involved exuding a passion not only for their technology but also for being part of a movement to help to save the planet from itself.