Solar

[Due to the increasing size of the archives, each topic page now contains only the prior 365 days of content. Access to older stories is now solely through the Monthly Archive pages or the site search function.]

“Project Volt Gas Volt” proposes long-term financing plan to support widespread implementation of power-to-gas systems

June 02, 2013

Project Volt Gas Volt is based on a long-term financing plan and the use of existing technologies for the large-scale conversion of surplus renewable electricity to methane, with subsequent reuse. Diagram: Isabelle Plat. Click to enlarge.

Corinne Lepage, Member of the European Parliament (and former French Minister of the Environment) and Professor Robert Bell, Brooklyn University, City University of New York, are proposing Project Volt Gas Volt (VGV) as a technology pathway for using renewable energy to “keep the lights on” on the broadest scale without disruption, together with a long-term financing proposal for the project. Although they are targeting an initial implementation France, they see it as broadly applicable.

Project VGV uses surplus electricity generated by renewable and nuclear sources to produce hydrogen via electrolysis. The hydrogen is combined with CO₂ to produce methane, which is pumped into and stored in the existing natural gas grid and used like natural gas for use in power generation, transportation, or other thermal and industrial uses. The concept is the same embodied in Audi’s e-gas project (earlier post), to which the VGV proposal makes continued reference.

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German researchers improve catalyst for steam reforming of methanol with salt coating; enabler for renewable energy storage systems

April 19, 2013

Researchers at the University of Erlangen-Nürnberg (Germany) report in the journal Angewandte Chemie their development of an enhanced platinum catalyst for the steam reforming of methanol to release hydrogen.

A central problem of renewable energy technology lies in the great variation of energy generated (i.e., intermittency). One proposed solution is methanol-based hydrogen storage. In this scenario, excess renewable electricity can be used to electrolyze water to produce hydrogen. The hydrogen, in turn, is then reacted with carbon dioxide to make methanol and water, thus allowing it to be stored as a liquid. The hydrogen can be released from the methanol at a later time to power a fuel cell.

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PNNL solar thermochemical reaction system can reduce fuel consumption in natural gas power plants by about 20%; future potential for transportation fuels

April 11, 2013

PNNL’s thermochemical conversion device is installed in front of a concentrating solar power dish. Photo: PNNL. Click to enlarge.

A new concentrating solar power system developed by Pacific Northwest National Laboratory (PNNL) can reduce the fuel consumption of a modified natural-gas combined-cycle (NGCC) power plant by about 20%. The system converts natural gas into syngas—with higher energy content than natural gas—using a thermochemical conversion device installed in front of a concentrating solar power dish. The power plant then combusts the more energy dense syngas to produce electricity.

PNNL’s system uses a mirrored parabolic dish to direct sunbeams to a central point, where the thermochemical device uses the solar heat to produce syngas form natural gas. About four feet long and two feet wide, the device contains a chemical reactor and several heat exchangers. Concentrated sunlight heats up the natural gas flowing through the reactor’s channels, which hold a catalyst that helps turn natural gas into syngas.

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Stanford GCEP awards $6.6M to 7 projects; focus on combining energy conversion with carbon-neutral fuel production

March 13, 2013

Stanford’s Global Climate and Energy Project (GCEP) is awarding $6.6 million to seven research teams—six from Stanford and one from Carnegie Mellon University—to advance research on technologies for renewable energy conversion to electricity or fuels and for capturing CO₂ emissions and converting CO₂ to fuels.

The 7 awards bring the total number of GCEP-supported research programs to 104, with total funding of approximately $125 million since the project’s launch in 2002.

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Stanford study quantifies energetic costs of grid-scale energy storage over time; current batteries the worst performers; the need to improve cycle life by 3-10x

March 10, 2013

A plot of ESOI for 7 potential grid-scale energy storage technologies. Credit: Barnhart and Benson, 2013. Click to enlarge.

A new study by Charles J. Barnhart and Sally M. Benson from Stanford University and Stanford’s Global Climate and Energy Project (GCEP) has quantified the energetic costs of 7 different grid-scale energy storage technologies over time. Using a new metric—“Energy Stored on Invested, ESOI”—they concluded that batteries were the worst performers, while compressed air energy storage (CAES) performed the best, followed by pumped hydro storage (PHS). Their results are published in the RSC journal Energy & Environmental Science.

As the percentage of electricity supply from wind and solar increases, grid operators will need to employ strategies and technologies, including energy storage, to balance supply with demand given the intermittency of the renewable supply. The Stanford study considered a future US grid where up to 80% of the electricity comes from renewables.

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MIT team outlines path to low-cost solar-to-fuels devices; the artificial leaf

March 05, 2013

(A) Block diagram for providing power to an electrochemical cell (EC), using a photovoltaic (PV) device via direct coupling, as well as (B) experimental examples, including an interdigitated contact geometry that minimizes solution resistance. Source: Winkler et al. 2013 Click to enlarge.

A team of researchers at MIT has described a framework for efficiently coupling the power output of a series-connected string of single-band-gap solar cells to an electrochemical process that produces storable fuels. The open access paper, published in the Proceedings of the National Academy of Sciences (PNAS), offers a roadmap for direct solar-to-fuels devices.

The new analysis follows up on 2011 research that produced a proof of concept of an artificial leaf—a small device that, when placed in a container of water and exposed to sunlight, would produce bubbles of hydrogen and oxygen. (Earlier post.) The new work outlines a research program to improve the efficiency of these systems, and could quickly lead to the production of a practical, inexpensive and commercially viable prototype.

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Researchers at UC Santa Barbara develop efficient and stable plasmonic water splitter; potential alternative to semiconductor-based solar conversion

February 25, 2013

Researchers at UC Santa Barbara have developed an efficient, autonomous solar water-splitting device based on a gold nanorod array in which essentially all charge carriers involved in the oxidation and reduction steps arise from the hot electrons resulting from the excitation of surface plasmons in the nanostructured gold (plasmonic water-splitter).

In a paper in the journal Nature Nanotechnology, they report that each nanorod functions without external wiring, producing 5x 10¹³ H₂ molecules per cm² per s under 1 sun illumination (AM 1.5 and 100 mW cm^-2), with unprecedented long-term operational stability.

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Volkswagen inaugurates 9.5 MW solar park at Chattanooga plant in US; key element of VW Group’s strategic sustainability targets

January 24, 2013

The 9.5 MW solar park at Chattanooga is owned and operated by Silicon Ranch; VW has signed a 20-year power purchase agreement. Click to enlarge.

Volkswagen inaugurated its largest solar facility in the world—also the largest solar facility operated by an automaker in the US—at its plant in Chattanooga, TN, which produces the Passat model for North America. The Volkswagen Chattanooga Solar Park has a peak output of 9.5 MW. The power will be used directly in production; solar power will provide up to 12.5% of the electric power required in full-capacity operation and 100% of demand when the plant is not in production.

The new solar park is an integral part of Volkswagen’s worldwide sustainability strategy, which includes generating more power within the Group from renewable energy sources, said Volkswagen Group Officer for the Environment, Energy and New Business Areas, Wolfram Thomas.

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Spatially explicit life cycle assessment of 5 sun-to-wheels pathways finds photovoltaic electricity and BEVs offer land-efficient and low-carbon transportation

January 04, 2013

Direct land use, life cycle GHG emissions (excluding indirect land use change), and life cycle fossil fuel requirements to generate the transportation services provided by 17.8 × 1012 MJ NCV of gasoline, the amount used in transportation in the US in 2009. Credit: ACS, Geyer et al. Click to enlarge.

A new spatially-explicit life cycle assessment of five different “sun-to-wheels” conversion pathways—ethanol from corn or switchgrass for internal combustion vehicles (ICVs); electricity from corn or switchgrass for battery-electric vehicles (BEVs); and photovoltaic electricity for BEVs—found a strong case for PV BEVs.

According to the findings by the team from the University of California, Santa Barbara and the Norwegian University of Science and Technology, published in the ACS journal Environmental Science & Technology, even the most land-use efficient biomass-based pathway (i.e., switchgrass bioelectricity in US counties with hypothetical crop yields of more than 24 tonnes/ha) requires 29 times more land than the PV-based alternative in the same locations.

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US/China research team proposes “solar energy funnel” to harness photons for electricity; using elastic strain to capture a wider spectrum

November 26, 2012

A visualization of the broad-spectrum solar energy funnel. Image: Yan Liang. Click to enlarge.

Researchers from Peking University in China and MIT are proposing using elastic strain as a viable agent to create an optoelectronic material with a spatially varying bandgap that is tunable for use in photovoltaics, photocatalysis and photodetection. In a paper published in Nature Photonics, they propose that a photovoltaic device made from a strain-engineered MoS₂ monolayer will capture a broad range of the solar spectrum and concentrate excitons or charge carriers.

The “funnel” is a metaphor: electrons and their counterparts, holes—which are split off from atoms by the energy of photons—are driven to the center of the structure by electronic forces. However, the material actually does assume the shape of a funnel—a stretched sheet of thin material, nano-indented at its center by a microscopic needle that produces a curved, funnel-like shape.

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Rochester researchers demonstrate robust photogeneration of hydrogen in water using semiconductor nanocrystals and a nickel catalyst

November 09, 2012

Researchers at the University of Rochester (New York) have developed a robust and highly active system for solar hydrogen generation in water using semiconductor nanocrystals (NCs) and a nickel catalyst. The system uses no precious metals, and is based on light absorption and photoinduced electron transfer from the semiconductor nanocrystals that are photochemically stable.

In a paper published in the journal Science, they report that the precious-metal-free system, under appropriate conditions, generates more than 600,000 turnovers of H₂ (with respect to catalyst) without deterioration of activity; has undiminished activity for at least 360 hours under illumination at 520 nm; and achieves quantum yields in water of more than 36%.

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NREL modifies organism to produce ethylene via photosynthesis: alternative to fossil-fuel based ethylene for chemicals and transportation fuels

September 26, 2012

Scientists at the US Department of Energy’s National Renewable Energy Laboratory (NREL) have developed a new photo-biological process for the sustained production of ethylene from CO₂. The NREL team introduced a modified gene sequence encoding an ethylene-forming enzyme from Pseudomonas syringae pv. into a cyanobacterium—Synechocystis sp. PCC 6803—and demonstrated that the organism remained stable through at least four generations, producing ethylene gas that could be easily captured. Research results were published in the RSC journal Energy & Environmental Science.

Ethylene—a valuable commodity two-carbon chemical that can be oligomerized into transportation fuels—is the most widely produced petrochemical feedstock globally. The organism produced ethylene at a high rate and is still being improved. The laboratory demonstrated rate of 171 milligrams of ethylene per liter per day is greater than the rates reported for the photosynthetic production by microorganisms of ethanol, butanol or other algae biofuels.

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Solar fuels company Joule commissions first plant to demo commercial readiness, launches Joule Fuels subsidiary to advance direct solar-to-fuels platform

September 11, 2012

Joule has commissioned its first SunSprings demonstration plant in Hobbs, New Mexico (earlier post), where the company will prove its scalable platform for solar fuel production using a fraction of the land and capital investment required for algae-derived or agricultural biofuels.

Joule has developed a highly modular system using highly engineered photosynthetic organisms to catalyze the conversion of sunlight and CO₂ directly to liquid hydrocarbons and ethanol (earlier post). Unlike sugar-based biofuel producers, Joule directly and continuously converts solar energy into liquid fuels, without costly raw materials, pretreatment or downstream processing. The initial output of the SunSprings plant will be ethanol.

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Panasonic develops highly efficient artificial photosynthesis system with gallium nitride semiconductor for conversion of CO2 to formic acid

July 30, 2012

Schematic view of artificial photosynthesis system. Click to enlarge.

Panasonic has developed an artificial photosynthesis system using a gallium nitride photoelectrode and a metal catalyst which uses sunlight to convert CO₂ mainly to formic acid (an important intermediate in chemical synthesis) at an efficiency (solar energy to chemical energy) of 0.2%—a comparable level to that of plants.

The reaction rate is completely proportional to the light power due to the low energy loss with the simple structure; in other words, the system can respond to focused light. This will make it possible to realize a simple and compact system for capturing and converting wasted carbon dioxide from incinerators and electric generation plants, according to Panasonic. Panasonic partially presented the technology on 30 July at the 19^th International Conference on the Conversion and Storage of Solar Energy (IPS-19) in Pasadena.

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GM and OnStar sign on as official Pecan Street partners; studying EV services and smart grid interaction

July 24, 2012

OnStar and General Motors are partnering in the Pecan Street Inc.’s smart grid research project in Austin’s Mueller community, the Pecan Street Demonstration. Headquartered at The University of Texas at Austin, Pecan Street Inc. is a research and development organization focused on developing and testing advanced technology, business model and customer behavior surrounding advanced energy management systems.

Chevrolet made 100 Chevrolet Volts available for purchase on a priority basis last September to residents participating the Pecan Street Inc.’s demonstration project, which now has the nation’s highest residential concentration of electric-drive vehicles in place. OnStar and GM are now signing on as an official partner of Pecan Street Inc., to help shape future electric vehicle services.

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