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Solar Power At Night | Earth Wise

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The use of solar power has grown tremendously in recent years as it has declined in price and become far more competitive with other forms of electricity generation.  Its fundamental drawback, of course, is that it only works when the sun is shining.  Solar panels don’t produce any power at night.  That is, until now, apparently.

A team of engineers at Stanford University have developed a new kind of solar cell that is capable of generating at least some electricity at night.  Published in the journal Applied Physics Letters, the research describes a device that can be a continuous renewable power source for both day and nighttime.

The device incorporates a thermoelectric generator that produces electricity from the small difference in temperature between the ambient air and the solar cell itself.  The amount of power produced is far less than the solar cell generates from sunlight, but the device can provide nighttime standby lighting and power in off-grid and mini-grid applications.

Mini-grid applications are independent electricity networks that are used for small populations that may be too isolated to be connected to the main power grid.  Nearly 600 million people in Africa currently live without access to electricity, primarily in rural areas.  A standalone solar system operating independently of any power grid can meet many electricity needs such as phone charging and lighting, but such systems may not be able to handle large electrical need such as powering machinery and agricultural equipment.  Mini-grids are larger installations that can provide power to a small rural community.

With innovations like the new Stanford device, a solar mini-grid may be able to keep running at some level even at night.

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Solar panels that can generate electricity at night have been developed at Stanford

Photo, posted December 15, 2021, courtesy of Pete via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Progress On Perovskite Solar Cells | Earth Wise

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Perovskites are semiconductors with a specific crystal structure.  Their properties make them well suited for making solar cells.  They can be manufactured at room temperature, using much less energy than it takes to make the silicon-based solar cells widely used today.  As a result, perovskite solar panels would be cheaper and more sustainable to produce.  Manufacturing silicon solar cells takes a lot of energy because silicon is forged at around 3000 degrees Fahrenheit. In addition, perovskites can be made flexible and transparent, making it possible to use them in ways unavailable with silicon solar technology.

But unlike silicon, perovskites are very fragile.  The early solar cells made from perovskites in 2009 and 2012 lasted for only minutes.  Lots of potential, but little practicality.

Recently, Princeton Engineering researchers have developed the first perovskite solar cell with a commercially viable lifetime, which is a major breakthrough.  The team projects that the device can perform above industry standards for about 30 years, which is much more than the 20 years designated as a viability threshold for commercial cells.

The research team has developed an ultra-thin capping layer between two of the layers of a perovskite solar cell.  The layer is just few atoms thick but has been demonstrated to dramatically increase the durability of the device. 

There is great potential for the new solar cell technology.  It has efficiency to compete with silicon cells but can be tuned for specific applications and can be manufactured locally with low energy inputs.  If successfully commercialized, the result will be solar panels that are cheaper, more efficient, and more flexible than what are available today.

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Once seen as fleeting, a new solar tech shines on and on

Photo, posted January 8, 2020, courtesy of David Baillot/UC San Diego Jacobs School of Engineering via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

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The World’s Largest Tidal Device | Earth Wise

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Most of the world’s activity in renewable energy is focused on solar and wind power.  The use of both is expanding rapidly. But there is also marine energy to be exploited.  Ocean waves and tidal movements hold huge amounts of energy.  Estimates are that the European Union could get 15% of its power from marine sources.  But ocean energy is currently expensive and there are significant technical challenges still to be overcome.

The world’s largest tidal power device will soon begin testing off the coast of Scotland.  The 680-ton, 240-foot-long, airplane-shaped device will be connected to the European Marine Energy Center for testing. 

The device, built by the Scottish company Orbital Marine Power, is designed to produce 2 megawatts of electricity, enough to power 2,000 homes.   It has a pair of 52-foot-long turbines attached to two wings.

Compared to wind and solar power, the marine energy sector has been much slower to develop because of the many difficulties of working in harsh marine environments as well as the technical challenges associated with harnessing power from waves and tides. But ocean waves and tidal movements hold enormous amounts of energy and have the advantage that they are available at all times, unlike wind and solar energy, which are variable in nature. 

Experts say that the future of tidal energy lies with arrays of floating or sea-bottom-mounted turbines that capture the energy of tidal currents in unobstructed waters.  There are various places around the world where this is an attractive opportunity, most notably in Nova Scotia’s Bay of Fundy, where the world’s most extreme tides – rising and falling more than 50 feet – contain vast amounts of power.

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The World’s Largest Tidal Power Device Will Soon Begin Testing Off Scotland

Photo, posted May 18, 2017, courtesy of Chris via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A High-Tech Fire Alarm | Earth Wise

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In recent years, wildfires have been a global problem, notably in California, Brazil, and Australia.  It has become increasingly important to be able to respond to new fires as soon and as quickly as possible.  Such response can make the task of extinguishing them easier, thereby reducing the amount of damage and the loss of property and life.

Traditional methods for detecting forest fires include satellite monitoring, ground patrols, and watch towers, all of which have high labor and financial costs but suffer from low efficiency.  Remote sensing technologies are becoming increasingly common but rely on batteries for power, requiring servicing in remote locations to replace depleted batteries.  Solar cells represent an alternative to batteries, but it is challenging to use them in forests because of shading and foliage coverage.

A team of researchers at Michigan State University has developed a remote forest fire detection and alarm system powered by nothing more than the movement of tree limbs in the wind.  The device is known as an MC-TENG, which is an acronym for multilayered cylindrical triboelectric nanogenerator.  The triboelectric effect is a phenomenon where certain materials become electrically charged when they separate from a second material with which they were previously in contact.  In the new device, two cylindrical sleeves fit within one another – one anchored and the other free to slide.  The device is tied to a tree branch and when the branch sporadically moves in the wind, electricity is generated and stored in a carbon-nanotube-based micro supercapacitor.  This powers a sensing system that can continuously monitor environmental conditions without requiring any maintenance.

A combination of carbon monoxide and temperature sensors provides a high-tech fire alarm that can operate continuously in the most remote forest.

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Self-Powered Alarm Fights Forest Fires, Monitors Environment

Photo, posted August 3, 2012, courtesy of Lukas Schlagenhauf via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Solar-Powered Desalination | Earth Wise

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About 1% of the world’s population is dependent on desalinated water to meet daily needs, but water scarcity is a growing problem that experts believe will affect 14% of the world’s population within the next five years.

Desalination takes much more energy than, for example, transporting fresh water over large distances.  In general, desalination costs are much higher than those associated with fresh water, but beyond costs, freshwater is simply not always available.

Researchers at MIT and Shanghai Jiao Tong University in China have developed a completely passive solar-powered desalination system that could provide more than 1.5 gallons of fresh drinking water per hour for every square meter of solar collecting area.   Such a system could provide an efficient, low-cost water source for coastal areas that are off the grid.

The system uses multiple layers of flat solar evaporators and condensers topped with transparent aerogel insulation.  The key to its efficiency is the way it uses each of its multiple stages to desalinate water.  At each stage, heat released by the previous stage is harnessed instead of wasted.  The proof-of-concept device, which was tested on an MIT building rooftop, produced more than twice as much water as the record amount produced by any previous passive solar-powered desalination system.

The researchers plan further experiments aimed at optimizing the choice of materials and configurations and to test the system under realistic conditions.  The hope is to have a technology that can play a role in alleviating water scarcity in parts of the world where electricity is scarce, but seawater and sunlight are abundant.

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Simple, solar-powered water desalination

Photo courtesy of MIT/researchers.

Earth Wise is a production of WAMC Northeast Public Radio.

Saving Energy At Data Centers | Earth Wise

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A data center is a building, dedicated space within a building, or a group of buildings used to house computer systems and associated components, such as telecommunications and data storage systems.  Data centers are the backbone of internet services and cloud computing, which together are increasingly dominant elements of modern life.

Energy use is a central issue for data centers. Power used by them ranges from a few kilowatts for a rack of servers in a closet at a local business to several tens of megawatts for large facilities. Some data centers have power densities more than 100 times that of a typical office building and use as much electricity as several thousand homes. For such facilities, electricity costs are a dominant operating expense and account for over 10% of the total cost of ownership of a data center.  These centers, with their numerous racks of computer servers, consume 90 billion kilowatt-hours of electricity each year in the United States, as much as all of our residences use for lighting. 

A research group at Princeton University is developing a family of devices that can dramatically reduce power consumption at data centers.  The team’s technology focuses on the process by which the AC power from the grid is converted to the low-voltage direct current used by computer equipment.  With existing technology, this power conversion takes place in each individual computer, which ends up wasting about 40% of the original energy.   The new device aggregates power conversion into a single unit, which then distributes the power to the individual computers and storage units.

As data centers get bigger and more numerous, the opportunity to save a lot of energy becomes increasingly important.

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New technology boosts energy efficiency in data centers

Photo, posted June 8, 2007, courtesy of Sean Ellis via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A New Way To Remove CO2 From The Air

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Researchers at MIT have developed a new way of removing carbon dioxide from a stream of air that could be a powerful tool in the battle against climate change.  The new system can pull carbon dioxide out of almost any concentration level of the gas, even including the roughly 400 parts per million level currently found in the atmosphere.

The technique is described in a new paper in the journal Energy and Environmental Science and is based on passing air through a stack of electrochemical plates. The device is essentially a large battery that absorbs carbon dioxide from the air passing over its electrodes as it is being charged up, and then releases the gas as it is being discharged.

To use it, the device would simply alternate between charging and discharging.  Fresh air or some other feed gas would be blown through the system during the charging cycle and then pure, concentrated carbon dioxide would be blown out during discharging.

The specialized battery uses electrodes coated with a compound called polyanthraquinone, which is composited with carbon nanotubes.  These unique electrodes have a binary affinity to carbon dioxide, which means that they either strongly want to capture carbon dioxide or not at all, depending upon whether the device is charging or discharging.

Carbon dioxide is important in many industries such as soft drinks and greenhouse agriculture.  With this device, the stuff could literally be pulled out of the air.  And, of course, in power plants where exhaust gas is dumped into the air, these novel electrochemical cells could be used to prevent the emission of CO2 into the atmosphere.  At the right price, this could be a game changer.

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MIT engineers develop a new way to remove carbon dioxide from air

Photo, posted August 9, 2007, courtesy of William Clifford via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Clean Gas From An Artificial Leaf

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Photosynthesis is the process used by plants, algae and certain bacteria to harness energy from sunlight and turn it into chemical energy.  It is often described as the green engine of life on earth.

For quite some time, there have been extensive research efforts around the world in the area of artificial photosynthesis.  The goal is to somehow mimic the behavior of plants in order to generate clean-burning fuels using nothing more than sunlight and the carbon dioxide in the air.

Researchers at the University of Cambridge have recently demonstrated a so-called artificial leaf that can directly produce syngas using sunlight.   Syngas is a fuel gas mixture consisting primarily of hydrogen and carbon monoxide.  Most people haven’t heard of syngas, but many products are created using it.  Being able to produce it sustainably would be a critical step to a far greener chemical and fuel industry.

The artificial leaf contains two light absorbers, similar to the molecules in plants that harvest sunlight, which are combined with a catalyst made from the naturally abundant element cobalt.  When the device is immersed in water, one light absorber uses the catalyst to produce oxygen.  The other carries out the chemical reaction that reduces carbon dioxide and water into carbon monoxide and hydrogen.  The result is the syngas mixture.

It turns out that even a rainy or overcast day provides enough light to drive the process.

Previous artificial leaf devices have mostly just produced hydrogen.  The Cambridge device produces syngas thanks to the novel combination of materials and catalysts it uses.

The researchers are now focused on finding ways to use the technology to produce a sustainable gasoline substitute.

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‘Artificial leaf’ successfully produces clean gas

Photo, posted August 15, 2014, courtesy of Mike Mozart via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Pulling Water From The Air

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A couple of years ago, we reported on the early development of a device that harvests water from the air that even works in the low humidity environment of a desert.  Since then, the researchers from UC Berkeley have continued to improve the device and it is now 10 times better than it was two years ago.

The harvester is based on a porous water-absorbing material called a metal-organic framework, or MOF.  The latest version can pull more than five cups of water from low-humidity air per day for every kilogram of the improved MOF material and that is more than enough water to sustain a person.  The harvester cycles around the clock and is powered by solar panels and a battery.

Previous techniques for condensing water from air at low humidity required cooling down the air to temperatures below freezing, which is not economically practical.  The MOF-based device does not require any cooling.

The Berkeley researchers have formed a startup company – Water Harvester, Inc. – which is now testing and will soon market a device the size of a microwave oven that can supply 7 to 10 liters of water per day, which is enough drinking and cooking water for two or three adults.

An even larger version of the harvester, which would be the size of a small refrigerator, would provide 200 to 250 liters of water per day, enough for a household to drink, cook, and shower.  The new company envisions a village-scale harvester that would produce 20,000 liters per day, still running off of solar panels and a battery.

Water Harvester believes the water needs for many people can come out of the thin air.

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Water harvester makes it easy to quench your thirst in the desert

Photo courtesy of Grant Glover (University of South Alabama) via UC Berkeley.

Earth Wise is a production of WAMC Northeast Public Radio.

A Prize For Water From The Air

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The XPrize competitions provide monetary incentives to crowdsource solutions to the world’s grand challenges.  Originally started in 1994 to spur the development of private spaceflight, the XPrize program now offers prizes for diverse fields including Oceans, Learning, Health, Energy, Environment, Transportation, Safety and Robotics.

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An App For Infection Testing

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Researchers at Washington State University have developed a low-cost, portable device that works with a smartphone to detect common viral and bacterial infections nearly as well as clinical laboratories.  Such a system could lead to faster and lower-cost lab results for fast-moving epidemics, especially in rural or lower-resource regions where laboratory equipment and medical personnel are not readily available.

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