General Director, Federal Environmental Agency, Germany 

1979-1984 
CERN/Geneva, Member of the UA1 Group unader Carlo Rubbia (Nobelprice 1984), discovery of the Z0, W+ and W- (Elemetary Particle Physics);

1984 - 1991 
Founder and owner of the Engineering Consultancy "UHL Data" for SystemsAnalysis and Simulation in the field of Energy and Environment; 

1985 - 1998          
Teacher at the Polytechnic of Aachen, Dpt. Jülich for "Numerical methods in environmental and energy planning" and "Solar Architecture for Engineers";

1991 - 2000           
Wuppertal Institute for Climate, Environment and Energy :Head of the Systems Analysis Group, 1999 - 2000 Research Director;

since 1987 
Eurosolar: 1987 - 1992 Member of the Board of the German Section,1992 - 1994 Vice president of the German Section,1994 - 2000 President of the German Section and Member of the European Board,2000 - 2006 Vice president of the European Board,since 2007 Member of the Scientific Board;

1996 
Prize-winner of the competition „best environmental book of the year“ of the German Foundation for Environment for the book: "Zukunftsenergien - Strategien einer neuen Energiepolitik”, together with T. Reetz;

1996 - 2000 
Member of the European Board of the”European Business Council for a Sustainable Energy\ Future E5”

since 1997 
Member of the Consultative Committee “100 Solar Districts” of the Building Ministry and the Ministry of Regional Planning of North-Rhine Westfalia;

since 1998 
Member of the „Factor 10/X Club“ for resource productivity and sustainable use ofnatural resources, since 2005 President;

1999 - 2003 
Member of the Enquete Commission “With new energy technologies in the nextcentury” of the Parliament of the state of Bavaria;

2000 - 2002 
Member of the Enquete Commission „Sustainable energy supply under the boundaries of globalisation and liberalisation“ of the German Parliament;

2000 - 2003 
Solutions and Innovations Unit Director, Greenpeace International;

since 2001 
Member of the “World Council for Renewable Energies”;

2000 - 2004 
Head of the “Institute for Sustainable Solutions and Innovations” (ISuSI);

since 2004 
General Director at the Federal Environmental Agency of Germany, Dessau,Head of Division Environmental Planning and Sustainable Strategies;

since 2005 
lectures “Renewable energy technologies” at the University Lüneburg;

since 2005 
Member of the scientific board of the “Umweltforschungszentrum Leipzig-Halle”since 2010 chairman;

since 2006 
Member of the scientific board of the “Solar Institute” of the Polytechnic of Aachen, Dpt. Jülich;

since 2007 
co-founder of the “Energy Watch Group” and chairman of the scientific board;

since 2008 
member of the climate board of the IBA Hamburg;