The second day of the conference began with keynote presentations from the National Renewable Energy Laboratory and the Idaho National Laboratory.
Prof. Arthur Frank of the NREL gave some insight into the type of research they conduct on sensitized solar cells, both dye and quantum dot.
The NREL's research efforts on DSSC's focus on better matching dye absorption coefficients to the solar spectrum. The resulting improvements could lead to an increase of photocurrent by 40% and efficiencies going from 11% to 20%.
Comparisons between disordered and nanotube (NT) films have lead to the conclusion that the ordered nature of NT films are more efficient for use in photovoltaic thin films. The dyes cover the interior as well as the exterior of the NTs with recombination ten times slower in this ordered version of films and charge collection efficiency increased by 25%.
In the field of Quantum dot cells, the NREL is researching the quantum confinement effects of different sized InAs quantum dots and the changes in absorbance characteristics that can lead to the tailoring of the resulting cell properties.
Steven Novack of the Idaho National Laboratory (INL) presented on the work on antennas for energy harvesting. The INL is capable of producing antennas that can absorb electromagnetic radiation at the near and mid infrared part of the spectrum. Drawing from roll to roll processing expertise at Microcontinuum, a Cambridge based start up that spun out of Polaroid, INL is able to print (using e-beam UV lithography printing) millions of nano-sized antennas per square inch. The ability to harvest infrared energy means that these antennas can convert residual heat into electricity even after the sun has gone down with a collection that is 4 times more efficient than in conventional photovoltaics. There is a need for further work on the rectification of that signal though, as at IR wavelengths frequencies are in the range of 30 THz.
Vijay Kapur, president and CEO of International Solar Electric Technology (ISET) also presented at the event, showcasing the company's CIGS technology advances. Dr Kapur put numbers in perspective comparing material cost and utilization when compared to Silicon technologies: 55 gallons (270 kg) of ISET's ink yields 1.24 MW of PV cells, with a cost of $70,000. Equivalent power would be produced by silicon cells with the use of 7.4 tons of silicon (assuming 5gr of Silicon per watt produced) at a cost of $740,000.
ISET's usage of Indium, which is considered by some people an issue due to its rising price, is limited according to Dr Kapur (25 metric tons for 1 GW of cells produced) so for ISET, Indium supply is not an issue.
The company has also identified ways of increasing efficiency of their cells by ironing out issues relating to gallium distribution after selenization, which would allow average efficiencies of 14%.
Brad Hines of Soliant Energy described the innovations on concentrator technology that Soliant has introduced. The company is focusing on inventing new architectures rather than new technologies (e.g. tip-tilt tracking rather than azimuth tracking for optimization of usage of space) and thus decreasing the requirements for space of their technology. Brad described how the fact that their optics and solar cell arrays "park on their side" at night limit the effect of gathering dust and debris on the efficiency of the system, resulting in less residue than flat cells.
On other presentations, Robert Jan Visser of Vitex Systems presented details on their Barix™ and Flexible Glass™ encapsulants, giving costs of $0.05-0.10 /in2 and $5-50/m2 respectively, with the possibility of even lower costs once production levels and orders increase. Ray LaPierre from McMaster University described the research on nano-wires undertaken by his group, and the way they could be used to improve the performance of solar cells.
Ron Ott of the Oak Ridge National Laboratory introduced the Plasma Arc lamp technology that is developed there which can achieve heating rates of 600,000 ºC/sec and temperatures that can melt Rhenium at 3180 ºC. These kinds of heating rates can improve rapid annealing hence, impacting and improving technologies ranging from silicon all the way to thin film technologies. Examples of improvements include better hydrogenation of a-Si, refinement of grain boundaries and minimization of diffusion within grains, partial sintering for the production of sponge like structures required in DSSC's without affecting the polymer dye.
The conference closed with presentations on processing and manufacturing of PV equipment by companies like iTi, Northfield Automation and Optomec that presented their offerings to solar cell producers.
Attracting approximately 200 attendees with a high-quality program that promoted networking and interaction, with a lot of positive feedback already received, the conference which is likely to grow in attendance will return to Denver next year, shedding light on the progress of these emerging technologies.