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Plants are often thought of as sources of food, oxygen, and decoration, but not as a source of electricity. However, scientists have discovered that by harnessing the natural transport of electrons within plant cells, it is possible to generate electricity as part of a green, biological solar cell. In a recent study published in ACS Applied Materials & Interfaces, researchers for the first time used a succulent plant to create a living “bio-solar cell” that runs on photosynthesis.

Photosynthesis is how plants and some microorganisms use sunlight to synthesize carbohydrates from carbon dioxide and water.

The Space Solar Power Project (SSPP) began in 2011 when Donald Bren — philanthropist, chairman of the Irvine Company, and a lifetime member of the Caltech Board of Trustees — and Caltech’s then-president Jean-Lou Chameau came together to discuss the potential for a space-based solar power research project. By 2013, Bren and his wife (Caltech trustee Brigitte Bren) began funding the project through the Donald Bren Foundation, which will eventually exceed $100 million. As Bren said in a recent Caltech press release:

“For many years, I’ve dreamed about how space-based solar power could solve some of humanity’s most urgent challenges. Today, I’m thrilled to be supporting Caltech’s brilliant scientists as they race to make that dream a reality.”

While the technology behind solar cells has existed since the late 19th century, generating solar power in space presents some serious challenges. For one thing, solar panels are heavy and require extensive wiring to transmit power, making them expensive and difficult to launch. To overcome these challenges, the SSPP team had to create a satellite that would be light enough for cost-effective launches yet strong enough to withstand the extreme environment of space. This required envisioning and developing new technologies, architectures, materials, and structures.

A new type of solar panel has achieved nine percent efficiency in converting water into hydrogen and oxygen through a process known as artificial photosynthesis.

This is a major breakthrough as it is nearly ten times more efficient than previous solar water-splitting experiments, according to a press release by the University of Michigan published on Wednesday.

Space Solar Power Demonstrator (SSPD) launched on January 3rd may be a breakthrough for harvesting solar energy from space.


A Caltech-designed prototype satellite containing an experiment, the Space Solar Power Demonstrator (SSPD), was launched on January 3rd of this year in what could prove to be a breakthrough for harvesting the energy of the Sun from space. The satellite goes by the name Momentus Vigoride and hitched its ride into space on a SpaceX Falcon 9 rocket.

Solar energy from space has been the dream of science fiction writers beginning with Isaac Asimov back in 1941 in a short story called Reason which later was included in a collection that Asimov published in 1950 entitled I, Robot. In the story, Asimov described a space station that collected energy from the Sun and transmitted it by microwave beam to various locations. Asimov recognized the distinct advantage of building solar power generating stations in space out of the Earth’s shadow and therefore continuously being able to harvest the energy of the Sun.

When the first telecommunication satellites were launched into geosynchronous orbits around Earth, it became obvious that not just communications could be offered in a continuous stream using satellite technology. A photovoltaic array parked in a similar orbit would stream electrical energy to Earth ground receivers. And depending on the size of an array deployed at that altitude, a satellite or a few of them to ensure no single failure, could become an endless supplier of all the energy the planet would need. There were technical problems still to work out.

The way electrons interact with photons of light is a vital part of many modern technologies, from lasers to solar panels to LEDs. But the interaction is inherently weak because of a major mismatch in scale: the wavelength of visible light is about 1,000 times larger than an electron, so the way the two things affect each other is limited by that disparity.

Now, researchers at The University of Hong Kong (HKU), MIT and other universities say they have come up with an innovative way to make more robust interactions between photons and electrons possible, that produces a hundredfold increase in the emission of light from a phenomenon called Smith-Purcell radiation. The findings have potential ramifications for both and fundamental scientific research, although it will require more years of investigation to put into practice.

The findings are published in Nature by Dr. Yi Yang (Assistant Professor of the Department of Physics at HKU and a former postdoc at MIT), Dr. Charles Roques-carmes (Postdoctoral Associate at MIT) and Professors Marin Soljačić and John Joannopoulos (MIT professors). The research team also included Steven Kooi at MIT’s Institute for Soldier Nanotechnologies, Haoning Tang and Eric Mazur at Harvard University, Justin Beroz at MIT, and Ido Kaminer at Technion-Israel Institute of Technology.

Chemists from Rice University and the University of Texas at Austin discovered more isn’t always better when it comes to packing charge-acceptor molecules on the surface of semiconducting nanocrystals.

The combination of organic and inorganic components in hybrid nanomaterials can be tailored to capture, detect, convert or control light in unique ways. Interest in these materials is high, and the pace of scientific publication about them has grown more than tenfold over the past 20 years. For example, they could potentially improve the efficiency of solar power systems by harvesting energy from wavelengths of sunlight—like infrared—that are missed by traditional photovoltaic solar panels.

To create the materials, chemists marry nanocrystals of light-capturing semiconductors with “charge acceptor” molecules that act as , attaching to the semiconductor’s surface and transporting electrons away from the nanocrystals.