PV Manufacturing Topics Covered at EHS Symposium
On July 16, SEMI EHS held an informational seminar on photovoltaic manufacturing at SEMICON West 2009 in San Francisco, California. Five key speakers presented their views:
- Vasilis Fthenakis, Brookhaven National Laboratory
- Lisa Krueger, First Solar
- Ben Ighani, CH2M Hill
- Eugene Ngai, Chemically Speaking
- Bruce Klafter, Applied Materials
Aaron Zude from SEMI opened the symposium by commenting that PV EHS is at a crossroads and that the decisions made now will affect how the industry takes shape in the future. Zude also pointed out that companies in the PV sector need to enact effective EHS practices so that it is clear that the industry itself believes in an environmentally sustainable future.
Some highlights from the presentations are summarized below. All PowerPoint presentations from these speakers are available at: http://www.semi.org/en/issues/ehs/ctr_028733
Photovoltaics— Enabling Sustainability of Very Large Growth: Vasilis Fthenakis, Brookhaven National Laboratory
Fthenakis touched on many subjects about PV including the costs, impacts, and myths about solar energy. He focused in on the issue of affordability for crystalline-Si PV. He looked at historical costs for PV modules against module price (in 2006 $/Wp), and asked if perhaps there really is a “Moore’s Law for PV”— a “20% price reduction with every doubling of capacity every 2 years.”
Regarding cost reduction drivers in thin-film PV, he cited:
- Materials: (approximately 50% of module cost): Volume, Efficiency, Thickness
- Energy: Throughput, Efficiency
- Labor: Throughput, Automation, Efficiency
- Depreciation: Throughput, Efficiency
Getting into the issue of metal availability (abundance in the continental crust (ppm) vs. world primary refinery production), Fthenakis said there is no problem with silicon, yet there are rare elements in thin-film PV, including: Te, In, Ge, and Ga. The material constraints in thin-film PV are: Te in CdTe; In in CIGS; and Ge in a-SiGe.
For each PV type (CdTe, CIGS, and a-Si-Ge), Fthenakis detailed both the efficiency in terms of percent and the layer thickness (um)— with his estimates for conservative, most likely and optimistic scenarios.
Extensive land use is one of the myths of PV. In fact, the energy output area of PV power plants is equivalent, if not better compared to the use of coal mining for power.
Greenhouse gases is one of the major advantages of PV since the amount of GHG released into the atmosphere per unit of energy produced is 500 times less then coal. He also delved into some of the other environmental considerations for PV: energy use, greenhouse gases, EHS risks, end-of-life disposal, and recycling.
First Solar and Sustainability: Lisa Krueger (VP, Sustainable Development), First Solar
Lisa Kruger gave an overview of First Solar’s mission, explained the life cycle of PV, and talked about the recycling program of solar cells. Founded in 1999, First Solar is the world’s largest thin-film solar module manufacturer. It is also the world’s lowest cost solar module manufacturer at $0.93/W, breaking the $1 per watt price barrier in Q4 last year.
Kruger focused on Life Cycle Assessment (LCA), a quantitative, cradle-to-grave assessment of environmental impacts of a product. This approach allows the comparison of the competing alternatives with a systematic and quantitative approach.
She also compared alternative energies from a carbon footprint standpoint: carbon footprints of coal (900), oil (850), gas (400), PV multi-Si (25), nuclear (24), PV CdTe (15), and wind (11). PV has tremendous potential to help us address climate change.
Another important concept that Kruger discussed is Energy Payback Time (EPBT) or the amount of time a system must operate to produce the amount of electricity that was used to fabricate the system. The goal is to minimize EPBT because this supports rapid scalability.
Krueger also emphasized the importance of recycling solar modules at the end of their life cycles, which is about 25 years. She discussed First Solar’s module collection and recycling program, which was designed to maximize collection rates and the amount of material recycled. Approximately 90% of the module weight is recovered; most of this is glass. Glass is reused in a new glass product. Estimated recovery of Te and Cd is 95%. Te and Cd is purified by a third party for reuse in First Solar modules. Financing is designed to ensure that the collection and recycling program is free of cost to end-users and users are protected if First Solar becomes insolvent.
Next, she discussed PV Cycle, an industry association focused on creating and implementing a voluntary, industry-wide take-back and recycling program for PV modules. It was founded in July 2007, committing to collect a minimum of 65% of photovoltaic modules installed in Europe and to recycle 85% of waste.
Even though PV is generally accepted as a low environmental impact industry, Kruger pointed out that the industry needs to focus on minimizing the life cycle impacts of energy production, and that producers need to embrace the concept of extended producer responsibility to include the recycling of their products.
Optimizing Sustainability of PV Manufacturing: Ben Ighani (director, Asia PV Technology & Manufacturing), CH2M Hill
Ighani talked greenhouse gas emissions and energy consumption benefits of PV use. Greenhouse gas emissions have increased tremendously since industry and population began to increase in the 20th century. Currently, buildings consume 48% of energy in the U.S., with industry accounting for 25% and transportation accounting for 27%. Four major ways to save energy in a PV fab: process tools (36%), HVAC-chilled water plant (25%), process mechanical systems (18%), and HVAC-air handling (15%).
The overall message was that reducing the amount of emissions and waste can result in much more efficient processes and reduced cost. CH2M Hill uses factory modeling to reduce electrical costs for companies. For example, with ventilation towers and low velocity fans, heat can be discharged vertically away from operators around tools. In addition, daylight modeling can be used to locate windows and reduce electrical lighting loads by using auto dimmers. He mentioned that redesigning or remodeling factories can dramatically reduce energy usage and increase efficiency. He cited one example where CH2M Hill helped decrease water usage by 28% and emissions by 34%. In addition, the fab reduced the number of boilers used by 30%, while achieving energy savings of 20%. He summarized by focusing on “whole system thinking,” where everything comes down to “reduce, reuse, and recycle” while continuously looking for opportunities to reduce CO2 emissions.
Sustainable Strategies of PV Materials Suppliers: Eugene Ngai, Chemically Speaking
Ngai talked about the use of hazardous gases in PV manufacturing and the potential dangers of mishandling materials. One of the materials he focused on was silane, a pyrophoric gas commonly used in PV manufacturing, due to its unpredictable behavior. In the past 40 years, six fatalities occurred when silane was released into a ventilated gas cabinet without immediate ignition and then exploded after a delay.
Ngai focused on safety, maintenance, and the overall improvement in efficiency in materials for PV manufacturing. He also touched on the issue of generating electronic specialty gases (ESG) on site as a way to reduce the risk (no transport risk; less quantity in the system at any time). Another aspect covered was bulk delivery systems, as they improve safety by increasing the time between cylinder changes by using ISO modules or mixing systems. They reduce cost and improve both safety and quality.
Sustainability Strategies of Equipment Manufacturers: Bruce Klafter (senior director, EHS), Applied Materials
Klafter talked about how PV manufacturing is different than traditional IC/semiconductor manufacturing:
- Participants are relatively inexperienced
- The factory “ecosystem” of suppliers, sub-suppliers, etc. is new and different
- Materials and equipment are different
- The processes, scale, pace and demands are different and/or are evolving, e.g. horizontal factory flows
- The locations and jurisdictions are new (at least to us, in some cases)
He discussed the issue of “factory startup” and the importance of getting it right. EHS is not just a departmental issue, but a company-wide responsibility, and that management and supervisors are also accountable for EHS policies and procedures. It’s important that EHS endeavors are both “data driven and transparent,” according to Klafter.
To learn more about SEMI EHS, visit www.semi.org/ehs. To view the PowerPoint presentations from these speakers, please visit:
For more information on the PV Group, visit www.pvgroup.org.
August 4, 2009