The 34th IEEE
Photovoltaic Specialists Conference
Philadelphia, PA
June 7–12, 2009

Conference Highlights: Tuesday June 9

It was a busy day at the 34^th IEEE PVSC on Tuesday and there are many highlights to note.

Tuesday was kicked off with two extended oral sessions.  In the terrestrial systems session Matt Campbell of SunPower described methods for calculating levelized cost of ownership for solar power systems, primarily for large scale central power generation.  He showed a range of system options available from SunPower and emphasized the concept of capacity factor, giving the effective fraction of the rated power that is produced by a PV system.  Typical values cited ranged from ~26% for a fixed plate up to 34% for a tracking system.  The session continued with talks by N.H. Reich discussing use of CAD tools for simulation of irradiation patterns, Nicola Pearsall describing system monitoring guidelines in Europe, and Cecile Warner reviewing two solar building design competitions occurring soon: the 2009 Solar Decathlon and the 2010 European Solar Decathlon.

In the Space PV extended oral session Ryne Raffele described the future issues and opportunities in space PV.  Carla Signorini of the European Space Agency presented an overview of a variety of ESA mission plans for the next 10 years.  The types of arrays and the differences in their design for missions to the inner and outer solar systems were described.  In particular the thermal management issues for systems operating in the inner solar system were described.  In the outer solar system the devices cool to the point that their fill factors are degraded.  David Witt of the AFRL described the use of a III-V multijunction (“IMM”) device structures.  Degradation can be reduced considerably in many orbits by a thin cover glass where proton damage dominates but does not help much with electron-induced degradation. Emcore demonstrated 32.4% efficiency with their IMM solar cell under AM0, 1 sun simulated light.  Spectrolab demonstrated a semiconductor bonded cell with 31.7% AM0.  This technology could yield 34-36% AM0 with further improvements.

In the Area 2 session S. Ishizuka of AIST presented a discussion of a thin alkali glass layer (~460 nm thick) as a Na source for flexible solar cells.  The performance of a CIGS cell produced on the soda lime glass layer on a Ta foil showed an increase in efficiency for SLG thickness up to about 120 nm but the performance decreased above this value.  A 17% efficient flexible solar cell has been achieved.  Prof. Leonard Brillson of the Ohio State University described the use of CL spectroscopy with variation of the electron beam energy to provide an effective CL depth profile into the sample.  This allows separation of the ZnO and CdS behaviors from the CIGS behaviors.  The results show that there is a correlation between CIGS device performance and the apparent interaction of the ZnO and CdS, attributed to interdiffusion and formation of ZnS.  Less interdiffusion would yield better device performance.

Area 4 included many interesting papers.  For example, Dingemans showed that aluminum oxide has excellent stability with respect to heat and UV exposure.  As a result there has been significant transfer to industrial processes.  Wang described how other metal oxides such as HfO are also being successfully applied to the passivation of silicon solar cells. Alternatives to screen-printing include the use of inkjet printing as a substitute for photolithography as described by Mingirulli, and Nielson demonstrated of lift off of 20 um thick substrates. Hacke of Advent Solar showed that their Ventura cell designs that are optimized for the implementation into a module.

Most attendees joined the conference luncheon celebrating the Cherry Hill Workshop in 1973.  The celebration was organized by Dr. Lawrence Kazmerski and brought together five of the original workshop organizers.  One of these participants, Chuck Backus, described the celebration “It was nice to be reminded of the history of photovoltaics.”  He went on to describe the workshop saying, “The workshop set the basis of the first federal research program in photovoltaics.”  It is also notable that the materials identified at the workshop have proven interesting and valuable and continue to be studied and applied to this day.  One exception to this is amorphous Si, which was not on their ‘radar screen’.  The workshop further identified advantages and disadvantages of crystalline Si that have proven to be the same key issues today.

For Area 8, an interesting and thought-provoking discussion was provided of the ability of solar power and water heating to address the need for emergencies after natural disasters.  SunPower introduced a new class of polymer frame systems for silicon modules.  A new and truly “integrated” BIPV solution was presented that bridged solar performance, ease of installation, and architectural integrity.  During this session, Peter McNutt of NREL provided an overview of an ongoing study of voltage regulation on the SMUD distribution system, while Hiroyuki Sugihara showed effective means of voltage regulation through energy storage for a 2.13 MW residential community in Ota, Japan. For the US's largest PV installation, Robert Batista of Renewable Ventures reported a 99.5% system availability for the 14-MW SunPower T20 tracking system installed at Nellis Air Force Base.

At the same time in the Area 9 session, Dr. Marie Mapes opened the PV Velocity Forum giving a talk entitled "DOE Solar Energy Technologies Program: Update on Photovoltaic R&D" That covered not only the highlights of the existing program, but also plans from the newly released 2010 budget request. Opportunities for new work in PV manufacturing technologies and the formation of new "Innovation Hubs" drew considerable interest.  The Innovation Hubs, aimed toward disruptive innovation in PV and CSP, will be launched with funding of 25 million dollars per year for five years with an addition 10 million dollars in the first year for start up and construction.  The hubs are intended to assemble purpose driven teams to address the basic science ad technology issues needed to overcome barriers to transforming energy technologies into commercially deployable materials, devices and systems.

Dr. Kosuke Kurokawa provided a first look at Japan's new PV Technology Roadmap "2030 +" that has just been completed for NEDO.  This lays out a path to lower costs and builds capacity to supply 10% of the national electricity, about 102 GW installed, by 2030.  He also announced the new incentives for residential applications that will pay 70,000 yen per kWp towards system installations for systems costing less than 700,000 yen per kWp.

Continuing the afternoon the poster sessions presented a variety of research with many interesting discussions.  Some examples of posters include a work on thin crystalline silicon on insulating surfaces in a collaboration between the University of Delaware, Blue Square Energy, and Arizona State University.  A poster from Tokai University described the effects of inert gasses on crystallinity in amorphous Si-Ge alloys.  The technology incubator program at NREL was described in a poster from Area 9, and recrystallization of Ge substrates for III-V PV substrates from NASA, the Rochester Institute of Technology, and the Ohio Aerospace Institute.

The day finished with two events that celebrated members of our community.  Martha Symko-Davies presented awards to two high schools, The Central High School and the Science Leadership Academy with awards for their exhibits presented on Monday at the High School Science Competition.  First Prize went to Central High School for a demonstration entitled “Optimized power generation in organic photovoltaics”.

Finally the program wrapped up with the Cherry Award presentation, talk, and reception.  This year’s Cherry Award was introduced by Tim Coutts who described the history of the award and the career of Dr. Cherry.  The winner of the award this year is Stuart Wenham of the University of New South Wales (UNSW).  He presented a talk describing the record performance Si solar devices produced at Suntech and developed in collaboration with UNSW.  He discussed in particular the metal contact technologies and methods used to form them.  Following his talk he was presented with a plaque and the conference adjourned to the reception.