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Published on August 25th, 2015 | by Tina Casey

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Concentrated Solar PV Not A Unicorn, Sez Energy Dept.

August 25th, 2015 by  


Concentrated solar PV is a highly efficient but highly complex form of cleantech and it has had its share of doubters, mainly due to its high cost and relatively large footprint. Well, along comes the Obama Administration to erase your doubts. Yesterday, the Department of Energy announced a whopping $24 million in funding for technologies leading to a whole new class of concentrated solar modules that could beat conventional solar modules on cost and performance, all while maintaining a slim flat-pack profile.

concentrated solar glint photonics

Concentrated Solar PV Gets Its Moment In The Sun

For those of you new to the topic, concentrated solar PV (CPV, for concentrated photovoltaic) refers to a system in which a large array of reflecting surfaces focuses the sun’s rays on a smaller array of solar cells. That’s not to be confused with concentrating solar power technology, in which heliostats (that’s fancyspeak for special mirrors) or trough-shaped structures focus solar energy to heat a liquid, which is then used to generate steam for a turbine. The US Department of Energy is already a huge fan of concentrating solar power (for the record, so is Saudi Arabia), and now it’s getting around to concentrated solar PV.

The general idea is to shrink concentrated solar arrays down to a micro scale, high-performance configuration that has a cost and footprint similar to a conventional flat solar module.

The platform for all this is MOSAIC, a concentrated solar program administered by ARPA-E, the Energy Department’s financing agency for cutting-edge research.

The task is pretty formidable — in order to succeed, you need to herd thousands of tiny lenses together in a common cause, and you also need to work around the expensive tracking mechanism used in conventional concentrated solar systems — but ARPA-E has already assembled 11 concentrated solar projects to tackle the problem, and that’s where the new $24 million in funding will go.



 

11 Concentrated Solar Projects

MOSAIC (short for Micro-scale Optimized Solar-cell Arrays with Integrated Concentration) divides the field into solutions that have the best potential for two regions of the US, those being the Southwest and parts of the Northeast and Midwest.

You can get all the details on the concentrated solar projects from ARPA-E, but for those of you on the go, here’s a quick rundown on the MOSAIC projects, starting with these three aimed at high direct sunlight regions:

1. Panasonic Boston Laboratory in Massachusetts is developing micro-tracking systems with rooftop solar applications.

2. Pennsylvania State University is also working on a new tracking system, something they call Angle Planar Microtracking Microcell CPV. Here’s the rundown from ARPA-E:

The team will use a combination of refractive and reflective plastic lenslet arrays to concentrate sunlight onto a corresponding array of micro – PV cells , which will be transfer – printed on to a transparent sheet that slides between them. Tracking will be accomplished by incrementally moving the middle microcell sheet laterally as the sun shifts, allowing the system to operate throughout the entire day without tilting the panel.

3. New York State’s University of Rochester has a Planar Light Guide Concentrated Photovoltaics project in the works, the end result of which will bee a lightweight module only three millimeters thick, tops. This project is specifically aimed at providing a solution for urban areas, where space for rooftop arrays is limited.

The following group is focusing on regions that don’t have the advantage of high direct sunlight:

4. The California Institute of Technology–Pasadena is doing something called Low Direct Normal Incident (DNI) Solar Radiation Technologies, which deploys quantum dots to take full advantage of relatively low amounts of sunshine. As with the Rochester project, this one is perfect for small spaces.

5. Massachusetts Institute of Technology is tasked with a system that captures both direct and diffused sunlight in module called Integrated Micro-Optical Concentrator Photovoltaics with Lateral Multijunction Cells. This will give you an idea of the game-changing efficiencies ARPA-E expects from MOSAIC:

The team’s micro – optical lens system will be ultra – compact and highly efficient, quadrupling the concentration of direct sunlight and tripling and the concentration of diffuse sunlight. This optics system will act as a prism to split the solar spectrum into different wavelengths, which will then be collected by laterally arranged solar cells appropriate to each wavelength. Conventional PV cells will be integrated benea th this array to capture diffuse sunlight.

6. A second MIT project, Wafer-Level Integrated Concentrating Photovoltaics, involves using conventional silicon solar cells to simplify the needs of the tracking system.

7. Semprius, Inc. of North Carolina is highlighted in ARPA-E’s press materials for its Micro-Scale Ultra-High-Efficiency CPV/Diffuse Hybrid Arrays Using Transfer Printing. The name pretty much says it all.

8. Sharp Laboratories of America in Washington State has a High-Efficiency Flat Plate PV with Integrated Micro-PV atop a 1-Sun Panel in the works, featuring a waveguide to add an extra level of concentration. This system also collects direct sunlight from the sky, and diffuse sunlight from the ground.

9. Texas A&M University Engineering Experiment Station also takes the waveguide approach with its Waveguiding Solar Concentrator project:

To significantly increase concentration of sunlight onto the PV cells, the team will arrange the concentrating lens arrays in a cascading fashion and align the arrays to a secondary concentrator using tapered waveguides. The waveguide concentrators, which are similar in performance to lens or other imaging optics, will enable the multi-junction solar cells to efficiently convert diffuse sunlight, enabling the system to be used in less sunny regions.

Half A Concentrated Solar Loaf Is Better Than None

MOSAIC also includes a third area of interest that involves anything that could help overcome technological obstacles, even if it addresses only part of the system:

10. The Palo Alto Research Center  in California will deploy something called a Chiplet Printer, aimed at high-volume printing of micro-solar cell arrays for concentrated solar systems.

11. Glint Photonics, Inc. of California, under the Small Business Innovation Research program, will develop a Stationary Wide-Angle Concentrator PV System that eschews bulky trackers in favor of a system that involves moving sheets of receivers within the concentrated solar module. The ultimate goal is a compact, lightweight system that can be installed on rooftops.

Obama Solar Policy Heating Up

Not for nothing but the new MOSAIC funding announcement comes fast on the heels of last week’s major shift in energy policy, in which a federal hydropower marketing agency launched its first ever solar energy buy with many more to come.

Add the just-announced federal adoption of PACE solar financing and the new solar incentives in the recently announced Clean Power Plan, and it seems that the Obama Administration’s solar policy is cooking with gas, as the saying goes.

Speaking of the Clean Power Plan, just before it was released, we noted that it seemed to be giving natural gas the bum’s rush in favor of renewables. That’s all the more obvious give the flurry of federal solar policymaking since the plan was announced earlier this month.

You can also check out Hawaii Governor Ige for another clue as to where US natural gas policy is heading.

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Image via Glint Potonics, Inc. 
 

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.



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