Page 266 - ISES SWC50

Thorsten Trupke
Country: Australia
Year joined industry: 1994
Company first worked for: BT Imaging
Technology area: PV
Still active in the industry: Yes

Thorsten Trupke is a Professor at the School for Photovoltaic (PV) Renewable Energy Engineering at UNSW, where
he leads a research team of approximately 15 staff, students and postdoctoral fellows. He is also co-founder and
Chief Technical Officer of BT imaging, a Sydney based technology company providing high-end photoluminescence
imaging systems to the Photovoltaic R&D community and to PV manufacturers. Thorsten started his career in PV
research in 1994, at the University of Karlsruhe, Germany, with a thesis on the electroluminescence of silicon solar
cells, performed under the supervision and guidance of Prof Peter Würfel. Thorsten has performed leading-edge
and widely published research on numerous PV related topics across many different areas. As a postdoctoral Fellow
he proposed, theoretically analysed and first demonstrated the concepts of combining solar cells with luminescence
up- and/or down conversion. His work on the design and development of novel characterisation methods, including
the invention and first demonstration of photoluminescence imaging in 2005, has revolutionized the measurement
and characterization of silicon samples and devices. This work has had wide-ranging implications and benefits
for PV research and development worldwide. The methods developed by Thorsten and his team, as well as the
instruments commercialized by BT Imaging, have become standard tools across the world and are used on a daily
basis, both in research labs and in high volume manufacturing. They continue to be crucial elements in the rapid
improvement of silicon solar cell technology and associated cost reductions. Thorsten’s impact and the quality
and relevance of his work have been recognized by numerous awards, including the 2017 Engineers Australia
Entrepreneur of the Year Award and most recently the prestigious 2019 Clunies Ross Innovation Award. Thorsten
has been a Fellow of the Australian Academy of Technology and Engineering (ATSE) since 2016.

Klaus Vajen

Country: Germany
Year joined industry: 1990
Company first worked for: Wagner Solartechnik
Technology area: Solar Thermal
Still active in the industry: Yes

In the late 1980s the solar thermal community discussed the “low-flow” concept as a promising new approach to
decrease investment and backup heating demand of solar domestic hot water systems. In January 1990, Vajen
started to develop a low-flow solar heating system for single family houses at the company Wagner Solartechnik,
one of the largest and most innovative solar technology suppliers at the time. Low-flow meant more than just
decreasing the flow rate through the collector field, we had to implement structural changes of collector and
hydraulics. Another challenge was to reach distinguished stratification in the storage tank. The low-flow concept
caused a nearly “holy” discussion in the early 1990s. Numerical evaluations put forward thermodynamic advantages
of the low-flow concept, but unfortunately, this could not be validated with measured data to the same extend.
At the end, practical problems prevailed: To avoid uneven flow distribution through collectors they needed to be
connected in series. This led to rather high pressure losses and demanded special displacement pumps, which
were noisy as well as expensive. Some devices to reach a good stratification in the storage tank were expensive, or
didn’t work, or even both. Furthermore, new highly efficient pumps decreased the potential savings of electricity. In
total, the overall system concept was, other than expected, in practice slightly more expensive and at the same time
slightly less efficient than systems with the traditional “high flow” operation. Today, “low-flow” technology doesn’t
play a perceptible role on the market of small SDHW-systems anymore, but it is still present in very large solar
thermal systems, as here it can decrease cost of hydraulic parts significantly. Wagner Solartechnik is still present on
the market as very experienced and innovative supplier of advanced solar technology. Vajen left industry after 1.5
years to start a PhD on another solar topic.

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