This Week in Green Tech: Energy Harvesting for IoT, Record-breaking Solar Cells, More States Committing to Renewable Energy, and Digital Twins
Tom Lombardo posted on April 21, 2020 |
Microwatt energy harvesting, megawatt solar arrays and digital twins—current green technology.

Green energy isn’t only about megawatts and gigawatts; harvesting microwatts to drive small-scale Internet of Things (IoT) devices also helps to shrink our ecological footprint. Let’s see what’s new in energy research and practice, from tiny transducers to big data.

Magnetic Energy Harvesting

The IoT plays a significant role in energy management through automated heating, cooling and lighting systems. Since many IoT devices are situated in remote locations, they’re often powered by batteries, which aren’t exactly made from eco-friendly materials. Luckily, engineers are developing electronic devices that use so little power that they can be driven by ambient energy, and they’re finding new ways to harvest that energy. 

Researchers at Penn State University have developed an energy-harvesting device that taps into stray magnetic fields, such as those near household power cords, and converts them into usable electricity. Rather than using an inductive coil, which works best with strong, high-frequency magnetic fields, the scientists employed a magneto-mechano-electric (MME) device, which is more efficient at converting weak, low-frequency magnetic fields into electricity. The transducer consists of a thin strip of piezoelectric material with a permanent magnet on one end. The permanent magnet vibrates in the presence of an AC magnetic field, causing the piezoelectric strip to bend back and forth, which generates an AC voltage. The researchers claim that the transducer is four times more efficient than current state-of-the-art energy harvesting technology.

When placed 10 centimeters (four inches) from a portable electric space heater’s cord, the MME generator delivered enough power to light a string of 180 LEDs. At twice that distance, it was able to drive a small digital alarm clock. We’re talking about microteslas of magnetic flux here, so an MME transducer won’t charge an electric vehicle, but it could power wireless, batteryless IoT sensors and associated circuitry, leaving more batteries available for that Tesla you’ve had your eye on.

Record-Breaking Solar Cell

Today’s silicon solar cells are about 25 percent efficient, which is better than internal combustion engines but still not great. Always trying to improve that number, scientists at the National Renewable Energy Laboratory (NREL) created a record-breaking solar cell with an efficiency of over 47 percent under concentrated light and 39 percent under normal sunlight. The multijunction cell includes six layers, each tuned to a specific part of the sun’s spectrum, allowing it to convert more sunlight to electricity than the single-junction silicon cells found in most solar panels today.

John Geisz and Ryan France built a solar cell that is nearly 50 percent efficient. (Image courtesy of Dennis Schroeder, NREL.)
John Geisz and Ryan France built a solar cell that is nearly 50 percent efficient. (Image courtesy of Dennis Schroeder, NREL.)

Multijunction cells are much more expensive, however, which currently relegates them to a niche market: space, where size and weight overrule cost. But some researchers hypothesize that concentrated solar—using lenses or mirrors to focus a large amount of light onto a small multijunction solar cell—could decrease the overall cost of an Earth-bound solar array since much less photovoltaic material is needed. The concept was demonstrated in 2017 using cells that were only 30 percent efficient. That system, which used a mechanical tracking device, generated 54 percent more energy than a commercial photovoltaic panel. If NREL can reduce the cost of manufacturing multijunction solar cells, we may see rooftop solar panels using tiny lenses to concentrate light onto very small multijunction cells. 

Largest Solar Project in Pennsylvania

The University of Pennsylvania (Penn) signed a power-purchase agreement (PPA) that will create two new solar arrays totaling 220 megawatts of power—the largest solar project in Pennsylvania. The array will produce 400 GWh of energy every year, providing roughly three-fourths of the university’s electricity demand. Array construction is slated to begin in the fall of 2021.

Keystone Solar in Pennsylvania. (Image courtesy of Community Energy, Inc.)
Keystone Solar in Pennsylvania. (Image courtesy of Community Energy, Inc.)

State-Level Green Initiatives

In 2002, a number of forward-thinking states formed the Clean Energy States Alliance (CESA), whose purpose is to coordinate efforts and share information among agencies looking to promote eco-friendly technologies and businesses. Given the lack of green energy initiatives at the federal level, 14 states and the District of Columbia have taken it upon themselves to pass legislation requiring the switch to 100 percent renewable energy over the next two to three decades. CESA recently launched its 100% Clean Energy Collaborative, an initiative aimed at helping these states collaborate on projects, share knowledge, and develop joint strategies. In addition to state officials, the collaborative includes representatives from utilities, industry and the general public.

“The rapid cost declines for wind, solar, and battery technologies, plus the growing threat of climate change, have motivated states to move aggressively to clean up their power supplies,” noted CESA Executive Director Warren Leon. “This new Collaborative will help states make more rapid progress towards their clean energy goals by engaging with other state leaders to form a peer network.” If you’re interested in learning more about the collaborative, CESA will be hosting a free webinar on May 11, 2020, at 3:00 p.m. ET.

The Virginia Clean Economy Act was recently signed by Governor Ralph Northam, setting a state goal of 100 percent renewable energy by 2050, including 21 gigawatts of solar and wind plus three gigawatts of energy storage. The act also establishes energy-efficiency standards, expands net-metering, and mandates the closing of virtually all of the state’s coal-fired plants by 2024. 

The states of Nevada and West Virginia are developing plans to convert abandoned mines into solar farms. More than a million acres of these “brownfields” exist in the two states, none of which are suitable for commercial or residential development, and all of which have the necessary infrastructure, such as roads and power lines, to make solar farms less costly to build. In addition to providing clean energy without destroying virgin land, these projects will create renewable energy jobs and deliver economic benefits to the regions in which they’re located.

Green Tech and Digital Twins

As renewable energy becomes a more significant part of the world’s electricity supply, the grid will need enhancements to account for fluctuations in both generation and consumption. This means incorporating big data into grid models and using real-time data to assess and predict both production and demand. To help prepare for this inevitable future, engineering.com released How a Digital Twin of Your Product Can Drive New Revenue Streams, which provides examples of using digital twins to maximize wind farm production, build smart cities, and enhance energy management.

As some researchers try to flatten the COVID-19 curve, others continue their efforts to flatten the duck curve—the discrepancy between energy supply and demand. Engineering.com will keep you informed of what’s happening on both fronts.

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