Conferences & Events

Scialog: Solar Energy Conversion

2nd Annual Conference (2011)

Keynote Presentations

Nate Lewis, "Improving on Photosynthesis"

Dan Arvizu, "The Rise of Renewables"

Jim McCusker, "More Cost-Effective Solar Panels"

Krishnan Rajeshwar, "Semiconductor Electrochemistry"

Tom Peterson, "Federal Government Presence"


Improving on Photosynthesis

Nate LewisCaltech chemistry professor Nathan S. Lewis delivered a project report to Scialog participants on the $122-million JCAP project, which he directs.

The DOE-funded “innovation hub,” is located in two California-based sites, and is operated under a unified management structure, Lewis said. The Southern California site is on the Caltech campus in Pasadena, and the Northern California site is at Lawrence Berkeley National Laboratory.

JCAP’s goal, Lewis said, is to develop and demonstrate a manufacturable solar-fuels generator, made of Earth-abundant elements, that will take sunlight, water and carbon dioxide as inputs, and robustly produce fuel from the sun 10 times more efficiently than natural photosynthesis in typical current crops.

“Finding a cost-effective way to produce fuels, as plants do, by combining sunlight, water, and carbon dioxide, would be a transformational advance in carbon-neutral energy technology,” Lewis said.

To accomplish this daunting task within the project’s 5-year time frame, JCAP must have goal-oriented programs and strong central management, Lewis said.

He said JCAP’s “accelerated discovery department” is focused on the means to accelerate the rate of discovery of light absorbers, catalysts, and membranes. Meanwhile the “scale?up department” is focused on the scientific underpinnings for linking various nano?components into fully functional artificial photosynthetic systems on a length scale of centimeters, and incorporating these photosynthetically active elements into fully operational solar?fuels generators on the 10 cm x 10 cm scale.

Lewis said that in addition to creating theoretical tools for guiding discovery and scale-up efforts, JCAP is developing high?throughput systems for quantitatively evaluating the performance of new light absorbers, photocatalysts and catalysts; it is also developing methods and standards for benchmarking the performance of everything involved in photosynthetic systems.

Because JCAP is aimed at producing workable and efficient artificial photosynthesis in a limited amount of time, Lewis said, once various benchmarks are achieved, researchers will halt their work in those areas and focus will be intensified in remaining areas.

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The Rise of Renewables

Dan ArvizuDan Arvizu, director and chief executive of the National Renewable Energy Laboratory (NREL), capped off the Scialog keynote addresses on the third day of the conference.

Arvizu, a presidential appointee to the National Science Board, is one of the world’s leading experts on renewable and sustainable energy. His talk, “Beyond Energy Innovation,” provided an overview of the current state of renewable energy globally and in the U.S. The challenges America faces – economic, security and environmental – all have an element related to energy, Arvizu said.

“We have to put together our strategies for research in the context of all these problems,” he said. “We can’t just solve one at the expense of the others.”

Arvizu recently administered the solar energy section of a United Nations report on the global renewable energy situation. He quoted the report as noting 12.9 percent of worldwide energy production currently comes from renewable resources, but more than 10 percent is comprised of “traditional biomass” --  wood-burning, animal waste and “really hazardous-to-your-health kind of stuff.” All other renewable energy-producing technologies globally amount to less than 3 percent of total production, he said, adding there is tremendous potential for renewable technologies to produce a much greater share of the world’s energy.

Currently China is the largest producer of renewable energy that is not hydroelectric; meanwhile, Germany has the largest percentage of renewable energy produced by solar technology. “Interestingly, China is the major exporter of solar technology, but the installations are all in Germany,” Arvizu said.

“Germany has the same solar insolation as Anchorage, Alaska, just to show there is plenty of opportunity for everybody else,” he said. (“Insolation” refers to solar radiation energy received on a given surface area in a given time.)

Global investment in renewable energy industries currently amounts to $268 billion annually, he said. By 2010 total global installation of wind-generated energy amounted to 194 gigawatts, up from a total of 17 gigawatts in 2000; meanwhile, photovoltaic installations went from less than a gigawatt in 2000 to more than 35 gigawatts globally in 2010.

Photovoltaics

Focusing on photovoltaic solar cells, Arvizu noted that it has taken decades for fundamental research advances to reach the commercial market. “And part of my job is to make sure that it doesn’t take 30 years for things that we’re working on in the lab today to make it to our rooftops. We can’t wait 30 years. That’s a key point.”

In an effort to speed up the deployment of photovoltaics, the U.S. Department of Energy has instituted the SunShot Initiative. Arvizu said it is a collaborative effort to make solar energy cost competitive with other forms of energy by the end of the decade. This would require reducing today’s average installed cost of solar energy systems by about 75 percent, according to DOE estimates.

Arvizu said a tremendous amount of innovation in creating renewable energy systems, including photovoltaics, is occurring in today’s world, “it’s just that most of it isn’t going on in this country.”

He said NREL has chosen to demonstrate the effectiveness of renewable energy by constructing a 330,000-square-foot, state-of-the-art research-support building to house 1,300 workers on its campus in Golden, CO.

“Forty percent of the energy consumption in the U.S. occurs in buildings, include roughly 70 percent of all electricity usage,” he said. That is why the new building is designed to rely mostly on sunlight for lighting. Also, a thick-walled “labyrinth” under the building stores warm air in the winter and cool air in the summer to reduce heating and air-conditioning costs. Arvizu said he received a special exemption from the U.S. government to allow the building’s windows to open and close, something that is not permitted in other government structures of this size. The roof of the building and its nearby parking garage are equipped with photovoltaic panels capable of generating 2.5 megawatts of electricity.

“It is the largest, most efficient building in the world,” Arvizu said. “On an annual basis, it generates as much energy as it consumes.” The average per capita consumption of energy for workers in the building is less than 300 watts, he added. (Some estimates put the average per capita consumption of electricity in the typical home at 2,000 watts.)

The total cost of the building was less than $289 a square foot, including the cost of the photovoltaic panels, he said, adding the building is a net exporter of electricity.

Arvizu said buildings like this can “change everything” in America. “But we need to invent the future that we want,” he said. “It’s not going to happen naturally.”

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More Cost-Effective Solar Panels

Jim McCuskerJim McCusker, a physical inorganic chemist from Michigan State University, is part of a collaboration of chemists, mathematicians and engineers at MSU that is striving to improve solar panel technology. The collaborative is supported by a $1.9 million grant from the NSF.

He told Scialog attendees that "for renewable energy to succeed, it has to get to a point where it is economically competitive with current technology. This means we need totally transformational technologies."

Today's solar panels are based on science worked out when the Beatles' "Good Day Sunshine" was new to the airwaves, he said. Their primary light absorber is extremely pure - and costly -- silicon. Electricity produced by solar panels today costs two or three times as much as energy produced by coal.

"With estimates showing global power consumption tripling by 2050, we need to have scalable approaches that balance cost efficiency with environmental stewardship," McCusker said. "Only solar can be scalable to the amounts required."

Solar energy is plentiful, if underutilized: The amount that hits the Earth's surface in one hour equals the energy humans consume in a year.

McCusker’s group is developing a solar cell based on a design that combines a dye with an inexpensive semiconductor -- titanium dioxide - instead of silicon. Titanium dioxide is an opaque white pigment commonly used in paint and other consumer products. Applying advanced materials and nanoparticle technology can make electron conduction more efficient, he said.

The efficiency of these devices is around 11 percent, McCusker noted, but that requires using a liquid electrolyte. His project will use a more efficient and inexpensive solid-state material.

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Semiconductor Electrochemistry

Krishnan RajeshwarKrishnan Rajeshwar, a distinguished professor in the department of chemistry, University of Texas at Arlington, spoke at Scialog on the history as well as the possible potential of inorganic semiconductor-liquid interfaces to produce liquid fuels.

“Despite impressive research advances, only a handful of semiconductor-coated surfaces have made successful transitions from the laboratory to the marketplace,” he said, adding those successes include dye-sensitized material for solar photon conversion as well as materials for self-cleaning and anti-fogging surfaces.

Rajeshwar, one of the top  eletrochemists in the U.S. focused primarily on energy issues, noted that when it comes to making efficient solar conversion materials, “the energy payback time -- the time it takes for the energy needed for material synthesis to be recovered back -- can be shrunk by deploying low-temperature synthesis methods.” One of those methods, he pointed out, is electrodepostion.

On the other hand, he noted, payback time can also be reduced by working to ensure that manufacture of semiconductor material is more efficient in terms of energy as well as time spent. One promising method to accomplish this, he suggested, is solution combustion synthesis.

Rajeshwar told Scialog fellows that he has also been exploring the potential and suitability of photoelectrochemical (PEC) methods to create in situ diagnostic tools for semiconductor film formation as well as spectroscopic probes of charge and mass transport at semiconductor/electrolyte interfaces.

Rejeshwar also briefly mentioned his lab’s exploration of the mechanisms of heterogeneous photocatalysis for possible toxic waste treatment and disinfection.

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Federal Government Presence

Tom PetersonTom Peterson, assistant director of the NSF’s Directorate for Engineering, discussed the federal funding agency’s current programs supporting interdisciplinary collaborations in solar research. He also took part in an hour-long discussion with Scialog fellows about possible ways to improve the NSF proposal review and funding procedures.

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