Sarah Kurtz, National Renewable Energy Laboratory: Page 2 of 2

Making the World a Better Place, One Solar Cell at a Time

SP: Typically, large solar project developers and EPC firms have more resources and more extensive in-house module reliability datasets for fielded PV arrays than small solar integration companies do. What advice do you have for the latter when it comes to evaluating the reliability of a given manufacturer’s PV modules?    

SK: The intent in creating IEC 62941 and other standards was to make that evaluation easy for smaller companies. Instead of sending an inspector to camp out in the factory during the manufacture of the modules, the customer can ask to see the IEC 62941 certification, which an IECRE-accredited certifying body must issue. We have started developing a similar guide for inverter quality assurance. IEC has just released edition three of IEC 61215 and edition two of IEC 61730, which add very useful requirements and which customers should request.

The draft of the CSA Group standard will be out for public review this spring and should be published by August 2017. Along with IEC 62941, this test protocol, entitled “PV Module Accelerated Testing Protocol for Quality Assurance Programs,” should give smaller companies confidence in PV modules. If customers are installing in very hot climates or on hot roofs, they may want to explore requiring higher-temperature testing that the IEC is developing.

SP: Are there any notable technical developments or advancements in research laboratory settings that you expect to see in the PV module production environment in the near future?

SK: The market is slowly adopting glass-on-glass modules, bifacial modules and modules with smaller junction boxes. These have been on the market for several years, but still have limited market share. Manufacturers are also introducing modules with higher-efficiency cells, including more passivated emitter rear cell (PERC), heterojunction with intrinsic thin layer (HIT) and interdigitated back contact (IBC) designs. Several companies such as NuvoSun and SolarCity are developing building-integrated products. Additionally, manufacturers are integrating solar cells into a range of products, including Toyota’s Prius Prime, drones, hats, backpacks and even roads. Perovskite solar cells have made impressive increases in efficiency to rival those of CdTe and CIGS, and work is under way to make these cells stable in a large area before launching production. Tandem solar cells based on silicon have now passed 30% efficiency, but manufacturers must bring the cost down before implementing production. Regarding the technologies that are higher efficiency than silicon, Alta Devices is to my knowledge the only company moving into significant production.

SP: How important is the research and development that the National Labs conduct in the transition to a 21st-century economy and electric grid? Are these efforts a big part of the US Department of Energy (DOE) annual budget?

SK: Our extensive, reliable power grid has fueled the nation’s growth over the last century; however, the grid we have today does not have the attributes necessary to meet the demands of the 21st century and beyond.  We are seeing significant increases in the percentage of variable generation from wind and PV assets. The proliferation of new smart devices and related goods and services is making consumer demands for electricity more variable as well. A modernized grid will need much more flexibility to accommodate these new technologies without loss of the reliability and affordability of electricity supply we’ve come to expect.

The National Labs, through the DOE-supported Grid Modernization Laboratory Consortium, are working together with industry and academia to create the foundational science and technology innovations needed for a modernized grid.  In over 80 coordinated projects, the National Labs are bridging the early-stage research done by academia with the near-term needs of industry to design, plan and operate a future modernized grid. These efforts are a growing part of the DOE budget and have doubled in size over the last few years with bipartisan support from Congress.

SP: As a percentage of the workforce, women are often underrepresented in science and technology as well as in the building trades. To what extent has this situation changed over the course of your career? Do you have any advice for women seeking to enter or advance in the solar industry?

SK: The statistics for science and technology have changed. When I was in graduate school, I recall finding that each new class was about 10% female. I think that fraction has increased by something like a factor of three, though the statistic varies with discipline and school. Female participation in the PV industry is surprisingly low.

My advice to women is to identify what you’re good at and what you find satisfying, then focus on the work rather than on gender-influenced interactions. Working on renewable energy is satisfying to me because I feel like I can be a small part of the much larger effort to build a better world. Keep in mind that any meaningful career will have its tough moments. Hang in there until you’re successful, comfortable and oblivious to the gender balance. 

When I first started taking science classes in college, I would notice that I was the only female in the room. Recently, my daughter helped me organize a meeting, after which she noted, “Mom, did you realize that you were the only female in that meeting?” I replied, “No, I didn’t. When I was your age I noticed, but now I don’t.” Everyone should undertake a career that matches their capabilities and their interests without regard to their gender, and we’ll end up with a great world.

SP: You have had a long and distinguished career in the PV research field. What are some of the most noteworthy findings or developments during your tenure at NREL?

SK: The most important development in my 35 years of studying PV is definitely the growth of the industry. We cannot find any past projection that PV would grow so fast. Even the most optimistic of the World Energy Outlook projections have grossly underestimated the growth of PV. The costs have also dropped faster than expected, further encouraging growth. Profit margins are at an unacceptably low level for module manufacturers and some other businesses in the supply and project development chain due to a surplus market. However, companies continue to invest, presumably because people want jobs and clean energy, perpetuating the surplus market and lack of profit. Many believed that today’s low prices for silicon modules were not possible to achieve, but module efficiencies have increased while the prices have dropped.

While it’s tempting to say that PV is so successful we don’t need more research, in the lab we see that there are still many more opportunities for improvement: even higher efficiencies, reduced materials use, longer-life modules, lower module operating temperatures to increase the efficiency under operating conditions and so forth. The combination of the low profit margins and the phenomenal success of the industry is making it difficult to sustain the level of R&D that could help implement the remaining opportunities. At the same time, PV has demonstrated that it is on a path to providing low-cost electricity in a way that can bring prosperity to the whole world.

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