High efficiency concentrating solar cells move to the rooftop

Via Penn State University.

Ultra-high efficiency solar cells similar to those used in space may now be possible on your rooftop thanks to a new microscale solar concentration technology developed by an international team of researchers.

“Concentrating photovoltaic (CPV) systems leverage the cost of high efficiency multi-junction solar cells by using inexpensive optics to concentrate sunlight onto them,” said Noel C. Giebink, assistant professor of electrical engineering, Penn State. “Current CPV systems are the size of billboards and have to be pointed very accurately to track the sun throughout the day. But, you can’t put a system like this on your roof, which is where the majority of solar panels throughout the world are installed.”

Giebink notes that the falling cost of typical silicon solar cells is making them a smaller and smaller fraction of the overall cost of solar electricity, which also includes “soft” costs like permitting, wiring, installation and maintenance that have remained fixed over time. Improving cell efficiency from about 20 percent for silicon toward greater than 40 percent with multi-junction CPV is important because increasing the power generated by a given system reduces the overall cost of the electricity that it generates.

To enable CPV on rooftops, the researchers combined miniaturized, gallium arsenide photovoltaic cells, 3D-printed plastic lens arrays and a moveable focusing mechanism to reduce the size, weight and cost of the CPV system and create something similar to a traditional solar panel that can be placed on the south-facing side of a building’s roof. They report their results today (Feb. 5) in Nature Communications.

“We partnered with colleagues at the University of Illinois because they are experts at making small, very efficient multi-junction solar cells,” said Giebink. “These cells are less than 1 square millimeter, made in large, parallel batches and then an array of them is transferred onto a thin sheet of glass or plastic.”

To focus sunlight on the array of cells, the researchers embedded them between a pair of 3D-printed plastic lenslet arrays. Each lenslet in the top array acts like a small magnifying glass and is matched to a lenslet in the bottom array that functions like a concave mirror. With each tiny solar cell located in the focus of this duo, sunlight is intensified more than 200 times. Because the focal point moves with the sun over the course of a day, the middle solar cell sheet tracks by sliding laterally in between the lenslet array.

Previous attempts at such translation-based tracking have only worked for about two hours a day because the focal point moves out of the plane of the solar cells, leading to loss of light and a drop in efficiency. By sandwiching the cells between the lenslet arrays, the researchers solved this problem and enabled efficient solar focusing for a full eight hour day with only about 1 centimeter of total movement needed for tracking.

To lubricate the sliding cell array and also improve transmission through the lenslet sandwich they used an optical oil, which allows small motors using a minimal amount of force for the mechanical tracking.

“The vision is that such a microtracking CPV panel could be placed on a roof in the same space as a traditional solar panel and generate a lot more power,” said Giebink. “The simplicity of this solution is really what gives it practical value.”

Because the total panel thickness is only about a centimeter and 99 percent of it — everything except the solar cells and their wiring — consists of acrylic plastic or Plexiglas, this system has the potential to be inexpensive to produce. Giebink cautions, however, that CPV systems are not suitable for all locations.

“CPV only makes sense in areas with lots of direct sunlight, like the American Southwest,” he said. “In cloudy regions like the Pacific Northwest, CPV systems can’t concentrate the diffuse light and they lose their efficiency advantage.”

The researchers tested their prototype concentrator panel outside over the course of a day in State College, Penn. Even though the printed plastic lenses were not up to specification, they were able to demonstrate over 100 times solar concentration.

Others working on this project include Jared Price, graduate student, Penn State; Xing Sheng, postdoctoral fellow; John A Rogers, professor of materials science and engineering, University of Illinois, Urbana Champaign; and Bram M. Meulblok, technical representative, LUXeXcel Group B.V., The Netherlands.

The U.S. Department of Energy funded this research.

Modeling Nutrient Loss from Midwest Crop Fields

Read the full story from the Agricultural Research Service.

In many Midwestern crop fields, excess water laden with nitrates drains into subsurface tile pipes and then flows into surface streams and rivers in the Mississippi River watershed. When the nutrient-rich field drainage reaches the Gulf of Mexico, it supports algal blooms that lower water oxygen levels and contribute to the development of the economically and environmentally devastating “dead zone.”

Upriver in Iowa, Agricultural Research Service scientists Rob Malone, Tom Kaspar, and Dan Jaynes are using the Root Zone Water Quality Model (RZWQM) to assess how using winter rye cover crops in corn-soybean rotations could mitigate nitrate loads in field drainage water. RZWQM is a field-scale computer model developed by the Agricultural Systems Research Unit in Fort Collins to simulate plant growth and the movement of water, nutrients, and chemicals within and around the root zones of agricultural crops.

R&D 100 Awards now accepting applications

Entry Deadline: April 20, 2015
For more information and to enter, visit http://www.rd100awards.com/

Known widely as “the Oscars of Invention,” the R&D 100 Awards allows you to stand shoulder-to-shoulder and compete with the elite of the research & development world. With the countless hours and substantial resources invested to bring it to market, your new product deserves to be showcased along with the year’s most significant new technology.

Winning an R&D 100 Award will enhance your product’s marketability and deliver a message that your organization and development team are leaders and innovators. An R&D 100 Award:

  • provides a positive initial marketing boost to many new technology innovations
  • recognizes the efforts of the development team and partners
  • signifies a mark of excellence known to industry, government, and consumers
  • tells potential customers that the product has successfully competed against other new technologies in open competition

This year, there are four Special Recognition Awards: Green Technology, Corporate Social Responsibility, and two “Market Disruptors,” one for products and one for services.

Entries submitted before February 6, 2015 are eligible for early review by R&D Magazine editors. Upon request, the editors will provide recommendations to improve the entry and increase your chances of winning an Award. Revised entries must be submitted by April 20, 2015.

U.S. Geological Survey National Climate Change and Wildlife Science Center and Climate Science Center Projects Announced

Fifty new research projects have recently been announced by the National Climate Change and Wildlife Science Center (NCCWSC) and Climate Science Centers. The Centers fund projects that align with a set of scientific priorities identified in consultation with management partners. Projects are reviewed with partners and funded based on their alignment with scientific priorities, the strength of the scientific proposal, and the project’s relationship to management decisions. These studies will focus on the impacts of climate change on wildlife, ecosystems, and communities and their ability to adapt to these changes.

Revving Up Energy Solutions Innovation

Read the full story in R&D Magazine.

During the 2014 R&D 100 Awards event, R&D Magazine expanded the banquet to hold four technology panels during the day. The last panel of the day focused on energy/environmental solutions and the innovation behind four R&D 100-winning technologies and the complexity of bringing such technologies to the market.

Speakers of the panel included Nicolas Dube, Distinguished Technologist, HP; Qichao Hu, Founder and CEO, SolidEnergy Systems; Ty McNutt, Director of Business Development, APEI Inc.; and Edward Williams, CEO, Novinda. Each gave feedback as to the issues of creating new energy/environmental solutions and the complexity of the innovation process.

Stockholm Environment Institute

From The Scout Report, Copyright Internet Scout 1994-2014.

The Stockholm Environment Institute (SEI) is an independent international research institute. For over 25 years SEI has been gathering data on the interrelated systems of development and ecology, bringing together diverse stakeholders for dialogues and partnerships. For the past several years, the organization has focused its efforts on four targeted activities: Managing environmental systems, Reducing climate risk, Transforming governance, and Rethinking development. Scout the site first by clicking on each of these categories to reveal theme summaries, sub-themes, and theme fact sheets. From there, have a look at the News & Media, Projects, Tools, and People tabs. One of the most exciting aspects of this site is the Recent Publications column, where you can read free empirical articles on such topics as “The economic case for low carb” and “A new era in the fight against deforestation in the Brazilian Amazon.” [CNH]

New Global Warming Remedy: Turning Rangelands into Carbon-Sucking Vacuums

Read the full story from UC Berkeley.

Studies conducted on a ranch in the heart of Marin County and led by UC Berkeley researchers and alums seem to confirm what home gardeners have long suspected: Compost really can save the world.