Draft Minutes of Meeting with Dr. Strobl, ASE on August 12, 1997
Meeting time: 90 minutes
Regina Hagen, Darmstädter Friedensforum
Wolfgang Schlupp-Hauck, Friedens- und Begegnungsstätte Mutlangen
Dr. Gerhard Strobl, Head of Development High Efficiency Solar Cells at Angewandte Solarenergie - ASE GmbH, Heilbronn
At the beginning of the meeting, Dr. Strobl gave information about ASE. ASE was a joint venture of NUKEM GmbH and Damiler-Benz Aerospace AG (DASA) from 1994. Since 1996, ASE has been a 100 % subsidiary of NUKEM and therefore of the Rheinisch-Westfälische Energieversorgung (RWE) [one of the major German electricity companies].
At the Heilbronn location, solar cells for space missions have been produced since 1964; shortly afterwards they started development and production of solar cells for terrestrial applications. Aerospace applications are a separate ASE profit center. Germany is a rather small market for terrestrial applications. Wordwide, about 50 % of the silicon solar cells for space missions are supplied by ASE. To gain a larger share of the US market for terrestrial applications, ASE took over a US company and founded ASE Americas Inc.
Next, we discussed current possibilities for using solar energy for deep space missions. The sequence of the various topics was random. We discussed the following issues:
The ESA press release of 1994 which has been mentioned so often referred to the technical breakthrough that 25 % efficiency had been reached under deep space conditions.
Due to the distance from the sun (earth: 1 AU [astronomical unit], Jupiter 5.2 AU, Saturn 9.54 AU), only 3.7 % of the light that reaches earth is available at Jupiter; at the distance of Saturn appr. 1 % of earth’s light intensity is left. In 1994, ASE managed to solve the problem of the feared „broken knee" effect, which usually occurs under LILT (low [light] intensity, low temperature) conditions. Since the 70s, this effect had caused the failure of all attempts to develop solar cells for deep space missions. Therefore, electricity for deep space missions could only be provided with RTGs prior to this breakthrough.
To develop the Si cells, ASE’s R&D team had an ESA (appr. DM 2 million) as well as an additional ASE research budget. The R&D effort resulted in single specimens of the new Si cell. By „stripping" this cell of specific features, a whole product family for various applications may be established. The most complex „king version" of this product family, the HI-ETA® NR LILT cell [NR for non-reflective], will be offered to ESA for the Rosetta mission to the comet Wirtanen.
In parallel to ASE’s research effort, GaAs cells were developed by CISE, an Italian research institute. This research was also contracted by ESA with ASE as the prime contractor. (CISE is located in Milano, Italy, and have their focus on research; they have but a small production line.) The GaAs cells developed by CISE have the same efficiency as ASE’s SI cells, but they weigh considerably more.
In the meantime, ASE produced 1,000 of the HI-ETA solar cells which will be used by ESA for the formal qualification program under realistic conditions. No decision has been taken yet as to which cells will be used for Rosetta. For the production and test phase, part of the Rosetta budget has been provided by ESTEC (the Dutch development section of ESA).
ASE has only a few competitors in the solar cell market for space missions. There is one competitor in Japan and two or three in the US. To date, ASE is the only company which is rigorously engaged in the field of solar cell production for space missions. As a result of the satellite technology, this market has been mostly commercialized. Yearly ASE output of solar cells for space missions amounts to appr. 500,000.
[Some comments in square brackets were included during translation to help non-German readers understand the context.]
Published online with permission of the author.