It took Yogi Goswami a moment to remember that he had spoken at Montana State University in 1998. But Nicomedes Alonso, who teaches mathematics at the University of Delaware and has a keen interest in solar energy, remembered the lecture quite clearly – and he stood in line Friday, Sept. 23, to congratulate the solar pioneer after Goswami accepted the 13th Karl W. Böer Solar Energy Medal of Merit at UD.

Alonso was just starting his graduate studies at Montana State when he heard Goswami speak, and he marveled at how far his research in solar thermal power and photocatalytic processes had advanced over the years.

"He has moved this research forward a tremendous amount," Alonso said.

Indeed, Böer – the distinguished UD professor emeritus for whom the medal is named – proclaimed Goswami the most comprehensive representative of the medal's objectives to date, excelling in all areas.

"You have surpassed all the criteria," Böer said to Goswami after UD President Dennis Assanis presented the medal in a ceremony at the Harker Interdisciplinary Science and Engineering Laboratory. "And more work is coming for you in the future."

The Böer Medal, which comes with a $60,000 prize, recognizes an individual who has made significant contributions in solar energy, wind energy or other forms of renewable energy through research, development or economic enterprise, or has made extraordinary, valuable and enduring contributions to the field in other ways.

Goswami's work checks all of those boxes.

• The Goswami Cycle he developed converts heat from solar collectors and geothermal or waste heat to produce power and cooling in the same cycle.

• Goswami developed a process to clean water or air using sunlight or artificial light. This invention was the first commercial solar application in microbiology.

• With almost 20 patents and more than 400 publications – including the textbook "Principles of Solar Engineering," now in its third edition – he is a prolific scholar, editor in chief of the Solar Energy journal and Progress in Solar Energy, and has contributed much to solar policy development in the United States and around the world.

He has seen many changes, too, in the work around solar as a renewable source of energy.

Cost has been an obstacle in solar technology, especially the cost of storing energy in batteries. His work using thermodynamic cycles and salt capsules for storage of solar energy suggests potential cost reductions of 50-80 percent, he said.

On another front, Goswami has been developing technology that uses sunlight to detoxify and disinfect wastewater and contaminated groundwater, breaking up such compounds as dioxins and PCBs. Using titanium oxide as a catalyst, photons from the ultraviolet light are absorbed and break up the chemical bonds.

He has worked on similar technology to clear indoor air of many pollutants, a problem he became interested in when he couldn't find an air cleaner that made a difference for his son, who has asthma and other allergies.

Using ultraviolet light and a specially coated filter, he developed a process that he says destroys airborne pollutants, including mold, viruses, bacteria, pollen, pet dander, dust, and other volatile organic chemicals. Molekule licensed the technology, he said. A website describes his device and notes that the first round of manufacturing has sold out, with a waiting list now forming.

Goswami said he sees future opportunity in nanoscale antennas for energy conversion and plasmic emitters for deep-space radiation cooling.

"There are opportunities we have not imagined," he said. "We may eventually be cooling surfaces by radiating the heat to deep space."

Ajay Prasad, Alumni Distinguished Professor of Mechanical Engineering and director of the Center for Fuel Cell Research, found the discussion fascinating.

"I'm really impressed the award was made to somebody with such a diverse range of applications – air purification, water purification, solar thermal energy," said Prasad. "I was expecting a discussion of quantum physics and photovoltaic semiconductor materials. For me as a mechanical engineer, this was very refreshing."

Goswami is distinguished professor of chemical engineering at the University of South Florida, where he directs the Clean Energy Research Center. He was inducted this year into the Florida Inventors Hall of Fame, a list that includes the likes of Henry Ford and Thomas Edison.

He said it was a privilege to visit the University, with its rich history and research.

"In solar energy research we all look towards the University of Delaware to see what's coming out of that campus," he said.

He turned to Böer with gratitude.

"Karl, you have been an inspiration to a lot of solar researchers and scientists around the world – and I am one of those," Goswami said.

Now 90 and living in Florida, Böer continues his work, with recent publications in the Journal of Applied Physics and Annalen der Physik. He is Distinguished Professor Emeritus of Physics and Solar Energy at UD and founder of the Institute of Energy Conversion (IEC).

Since its founding in 1972, IEC has been a leader in photovoltaic research. It is the oldest solar cell institution in the world and is designated a University Center of Excellence for Photovoltaic Research and Education by the U.S. Department of Energy.

"You never put down your mind," Böer said. "You always keep going to do something that is practical, something that can be patented, something that brings the solar energy field further."

Former U.S. President Jimmy Carter was the first recipient of the Böer Medal, presented in 1993, for his success in promoting development of solar energy technology.

Previous medal winners

• 2015, Antonio Luque (Spain), for inventing the intermediate band solar cell, which raises the efficiency limit from 41 percent to 63 percent.

• 2013, Zhores I. Alferov and Viacheslav M. Andreev (Russia), for their contributions to the investigation and development of semiconductor device technology and physics, which have led to greater performance and efficiency of solar cells and arrays.

• 2011, Richard M. Swanson (USA), for his innovation in the field of photovoltaics and for his tenure as president of SunPower Corp.

• 2009, Hermann Scheer (Germany), for his long-lasting and worldwide commitment to the dissemination of solar energy.

• 2007, Lawrence Kazmerski (USA), for his leadership in the field of solar electricity from its infancy.

• 2005, Yoshihiro Hamakawa (Japan), for his significant pioneering contributions to the development of high-efficiency thin-film solar cells and the advancement of solar photovoltaic science and technology as a clean energy source.

• 2003, Martin A. Green (Australia), for his innovative research efforts in the development of high performance crystalline silicon solar cell technology.

• 2001, Allen M. Barnett (USA), for his pioneering high-performance, thin-crystalline silicon solar cells, and outstanding continuing service to the solar electric power community.

• 1999, Stanford R. Ovshinsky (USA), for pioneering the science of amorphous semiconductors resulting in the development of low-cost thin-film silicon solar cells.

• 1997, Adolf Goetzberger (Germany), for his leadership in the international solar energy community, his research accomplishments and for founding the eminent Fraunhofer Institute for Solar Energy Systems.

• 1995, David E. Carlson (USA), for the discovery and commercial development of thin film amorphous silicon cells for converting sunlight to electrical energy.

• 1993, President Jimmy Carter (USA), for spurring development and focusing world attention on the relatively unknown technology for safe and environmentally sound energy production from the sun.