Connect with us


Variant of photovoltaic power could generate 24 hours a day



Enlarge / A test of radiative cooling panels at the University of Colorado.

Moving from the present world to one where renewable power dominates our energy economy is going to require some additional technologies. These may include storage, enhanced grid management, and demand-response power management, but they could also include something entirely new. Recently, a paper took a look at a technology I hadn’t realized even existed.

The paper evaluates the potential of what its authors are terming “nighttime photovoltaic power,” and the simplest way of thinking about it is “running solar panels in reverse”: generating electricity by radiating energy away into space. The efficiency is nothing like that of standard photovoltaics and can’t even get there except in unusual circumstances. But as the name implies, it can keep generating power long after the Sun goes down.

Photovoltaics at night

The easiest way to understand this tech is to think of a photovoltaic device in equilibrium with its environment. Here, incoming photons will occasionally liberate an electron, leaving behind a positively charged hole. These can then combine, radiating a photon back out of the device. When operating as a photovoltaic device, there’s a large excess of photons coming in, producing a corresponding excess of electrons and holes that can then be harvested as electricity.

Now envision setting up the reverse situation: there are no incoming photons, and instead we ensure that an excess of photons is radiated away as infrared radiation. An excess of electrons and holes will now form, and those can again be harvested. Except in this case, we don’t need any incoming light—instead, we need something to ensure that photons are extracted from the device at high efficiencies.

This latter requirement is something that researchers in a seemingly unrelated area of research has been working on. There’s a “window” of infrared wavelengths that aren’t absorbed by any of the gasses in the atmosphere. A carefully crafted material can absorb radiation at a variety of wavelengths but only radiate it back out at wavelengths that fit through this atmospheric window. People have been building devices that operate this way as a means of passively cooling buildings, and there are even ways of treating wood so that it operates in this manner.

Potentially, by linking a photovoltaic material that emits photons that are matched with a passively radiating device, it’s possible to build a “thermoradiative cell” that can extract some electricity while radiating photons out into space. In contexts where there’s a large cooling demand or a lot of waste heat, this could be an added benefit to the cooling that needs to be done anyway. But can it actually work in any practical way?

Running the numbers

That’s what Tristan Deppe and Jeremy Munday decided to find out. Their paper analyzes everything from the semiconductor bandgaps needed for this to work to the wavelengths normally present in the atmosphere.

The atmosphere is an issue because no material is completely transparent to all the wavelengths of light that are typically present in our atmosphere. That means that all the materials involved—the one radiating away the infrared and the one generating spare electrons—will absorb some of the stray photons, decreasing the overall efficiency of the device. The bandgap is an issue because the infrared wavelengths needed for this to work are relatively low-energy, so they need a much smaller bandgap than the silicon used in most photovoltaic cells. The researchers suggest that a family of mercury-cadmium-tellurium compounds appears to have the right properties.

For all their initial calculations, Deppe and Munday assume that the Earth will provide a constant source of 27°C (about 80°F) heat to drive the system. Under these circumstances, they estimate that these systems built with current technology can produce somewhere in the neighborhood of two to eight watts per square meter, with the value changing a bit based on season and location.

Compared to a photovoltaic panel, which typically hits in the area of 200 watts/meter2, that’s pretty pathetic. But this could potentially generate 24 hours a day, which a photovoltaic panel most certainly cannot, so that offsets some of the disadvantage. Since much of the infrastructure would be identical for photovoltaic and thermoradiative cells, they also did an estimate of the benefits of a system that could automatically switch panels when the Sun goes down. They calculate that this would increase the power output of a solar farm by 12 percent.

Low, low prices

For those sorts of incremental gains, the thermoradiative cells would need to have incredibly low prices to make economic sense. But when there are co-benefits, like cutting down the cooling bills for buildings in hot climates, the economics might shift a bit.

The really interesting part, however, comes when Deppe and Munday look into what can be done with waste heat. With a starting heat source of 170°C, a thermoradiative cell could produce roughly the same number of watts/meter as a solar panel. While that temperature is hot—it’s well above the boiling point of water—it’s within the range of what might be considered waste heat for industrial plants and steam generators. And if linked to things like geothermal or solar-thermal plants, it would provide a way of extracting more energy from an existing renewable resource.

For now, this is all purely hypothetical; many of the numbers in the paper are from idealized situations, and we have no idea how close to those we can get in the real world or how cheaply these devices could be manufactured. But the idea is a clever extension of existing technology that could potentially integrate with a variety of existing systems.

ACS Photonics, 2020. DOI: 10.1021/acsphotonics.9b00679  (About DOIs).

Continue Reading


Scientists are figuring out how to destroy “forever chemicals”



Enlarge / How long do we really need chemicals to last?

PFAS chemicals seemed like a good idea at first. As Teflon, they made pots easier to clean starting in the 1940s. They made jackets waterproof and carpets stain-resistant. Food wrappers, firefighting foam, even makeup seemed better with perfluoroalkyl and polyfluoroalkyl substances.

Then tests started detecting PFAS in people’s blood.

Today, PFAS are pervasive in soil, dust, and drinking water around the world. Studies suggest they’re in 98 percent of Americans’ bodies, where they’ve been associated with health problems including thyroid disease, liver damage, and kidney and testicular cancer. There are now over 9,000 types of PFAS. They’re often referred to as “forever chemicals” because the same properties that make them so useful also ensure they don’t break down in nature.

Scientists are working on methods to capture these synthetic chemicals and destroy them, but it isn’t simple.

The latest breakthrough, published August 18, 2022, in the journal Science, shows how one class of PFAS can be broken down into mostly harmless components using sodium hydroxide, or lye, an inexpensive compound used in soap. It isn’t an immediate solution to this vast problem, but it offers new insight.

Biochemist A. Daniel Jones and soil scientist Hui Li work on PFAS solutions at the Michigan State University and explained the promising PFAS destruction techniques being tested today.

How do PFAS get from everyday products into water, soil, and eventually humans?

There are two main exposure pathways for PFAS to get into humans—drinking water and food consumption.

PFAS can get into soil through land application of biosolids, that is, sludge from wastewater treatment, and they can leach out from landfills. If contaminated biosolids are applied to farm fields as fertilizer, PFAS can get into water and into crops and vegetables.

For example, livestock can consume PFAS through the crops they eat and water they drink. There have been cases reported in Michigan, Maine, and New Mexico of elevated levels of PFAS in beef and in dairy cows. How big the potential risk is to humans is still largely unknown.

Cows were found with high levels of PFAS at a farm in Maine.
Enlarge / Cows were found with high levels of PFAS at a farm in Maine.

Scientists in our group at Michigan State University are working on materials added to soil that could prevent plants from taking up PFAS, but it would leave PFAS in the soil.

The problem is that these chemicals are everywhere, and there is no natural process in water or soil that breaks them down. Many consumer products are loaded with PFAS, including makeup, dental floss, guitar strings, and ski wax.

Continue Reading


Rocket Report: Europe wants a super-heavy lifter, Starship nets launch contract



Enlarge / Skyrora announced this week it has completed a hot fire test of its XL rocket’s second stage.


Welcome to Edition 5.07 of the Rocket Report! We are now just 11 days away from NASA’s first attempt to launch its SLS rocket and Orion spacecraft. I’ve reported this story for more than 11 years and can hardly believe we’ve reached this moment. Starting Monday, I’ll have a lot of coverage—good and bad—on Ars to put this moment into context. Be sure to check it out.

As always, we welcome reader submissions, and if you don’t want to miss an issue, please subscribe using the box below (the form will not appear on AMP-enabled versions of the site). Each report will include information on small-, medium-, and heavy-lift rockets as well as a quick look ahead at the next three launches on the calendar.

Really—the Electron is going to Venus. Rocket Lab announced this week plans to self-fund the development of a small spacecraft and its launch on an Electron rocket. The craft will send a tiny probe flying through the clouds of Venus for about five minutes at an altitude of 48-60 km. Rocket Lab founder Peter Beck has joined up with several noted planetary scientists, including Massachusetts Institute of Technology professor Sara Seager, to design this mission, Ars reports.

A bold self-bet … Electron will deliver the spacecraft into a 165 km orbit above Earth, where the rocket’s high-energy Photon upper stage will perform a number of burns to raise the spacecraft’s orbit and reach escape velocity. Assuming a May 2023 launch—there’s a backup opportunity in January 2025—the spacecraft would reach Venus in October 2023. Once there, Photon will deploy a small 20 kg probe into the Venusian atmosphere. If Beck succeeds with a Venus mission, he’ll certainly catch the attention of scientists, NASA, and others interested in what would be a promising new era of low-cost, more rapid exploration of the Solar System.

Small rocket industry growth slows. Fewer new small launch vehicles are entering the market, and more vehicles are going defunct as demand for such vehicles lags expectations, Space News reports. In a presentation at the Small Satellite Conference, Carlos Niederstrasser of Northrop Grumman discussed the latest version of an annual survey of the small launch vehicle industry, focused on vehicles capable of placing up to 1,000 kg into low-Earth orbit and available commercially.

Ride share may threaten small launch demand … The survey now includes 166 launch vehicle projects, far higher than the 31 the same survey identified in 2015. However, growth in the number of those vehicles is now slowing. “There is no longer the crazy growth we were seeing back in ’16 or ’17,” Niederstrasser said. In addition, the number of systems that have gone defunct for technical, financial, or other reasons has grown. “We are definitely seeing significant attrition,” he added. “That should surprise no one.” (submitted by Mike Richards, EllPeaTea, and Ken the Bin)

The easiest way to keep up with Eric Berger’s space reporting is to sign up for his newsletter, we’ll collect his stories in your inbox.

Rocket Lab hits milestones with next launch. The company’s next mission, a launch in mid-September from New Zealand’s Mahia Peninsula, is a dedicated launch for Japanese Earth-imaging satellite constellation operator Synspective. It will also be Rocket Lab’s 30th launch. Rocket Lab notes that, in addition, the mission will deliver its 150th payload and 300th Rutherford engine to space. Nine Rutherford engines power the Electron’s first stage, and a single one powers the upper stage.

Breaking a cadence record … The single StriX-1 satellite manifested on this Electron launch will bring Rocket Lab’s tally of satellites delivered to orbit to 150, with a quarter of those delivered to space in the past three months alone, including the CAPSTONE satellite to the Moon for NASA. This will be the seventh launch of the year for Rocket Lab, and if all goes well it would set a new record for successful missions in a calendar year. (submitted by Ken the Bin)

Skyrora completes second stage test. The United Kingdom-based launch company announced Thursday the completion of a static fire test of the second stage of its Skyrora XL orbital rocket. Completing the test brings Skyrora closer to entering commercial operations, with the rocket’s inaugural orbital launch scheduled for 2023 from the Saxa Vord Space Centre in northern Scotland. The 20-second test burn of a single 70 kN liquid engine operated within design margins and achieved the expected thrust, the company said.

Quick setup … The three-stage XL launch vehicle is a small rocket, with a lift capacity of about 300 kg to low-Earth orbit, and is of modular design so that it can be easily transported to the launch site. Skyrora previously tested the third stage of its XL launch vehicle in December 2020. The first stage of Skyrora XL is currently in construction, with hot-fire tests due to take place in mid-2023. “Our Skyrora team went from clean tarmac to a full static fire test in just 2.5 days,” said the company’s chief operating officer, Lee Rosen. (submitted by Ken the Bin)

SpaceX aims to double Vandenberg cadence. Following an August 12 launch of another batch of Starlink satellites, SpaceX has extended its annual Falcon 9 launch record from Vandenberg Space Force Base in California. This was the eighth Falcon 9 launch from the spaceport this year. The company’s previous high-water mark from Vandenberg was six launches, in 2018.

Are you tenacious? … But the company is not stopping there. In a post on LinkedIn, SpaceX’s manager of Falcon 9 operations, Steven Cameron, said the company is hiring to support a higher launch cadence. “We are hiring skilled technicians as we move to increase the launch cadence on the West Coast by more than double,” Cameron wrote. “Dont [sic] have the background we are looking for? Thats [sic] ok, are you tenacious? We will train you.” (submitted by MB)

Europe looks to SpaceX to fill interim launch need: The European Space Agency (ESA) has begun preliminary technical discussions with SpaceX that could lead to the temporary use of the company’s rockets after the Ukraine conflict blocked Western access to Russia’s Soyuz rockets, Reuters reports. ESA is looking for alternative launch options because of delays to its Ariane 6 rocket, which remains in development and probably will not fly for the first time until at least the middle of 2023.

Only SpaceX has the capacity right now … ESA Director General Josef Aschbacher said he is also considering Japan’s H3 rocket, which is also in the final stages of development, as well as India’s fleet. But only SpaceX has the capacity with its reusable Falcon 9 rocket to meet near-term demand. “The likelihood of the need for backup launches is high,” he said. “The order of magnitude is certainly a good handful of launches that we would need interim solutions.” OneWeb and Northrop Grumman have also recently booked launches on the Falcon 9 after Ukraine-related issues with Russian rockets and engines. (submitted by Ken the Bin)

Canadian spaceport has a potential US tenant. Maritime Launch Services, which is attempting to develop a spaceport in Nova Scotia, Canada, reported a quarterly loss of $4.3 million for the three-month period that ended June 30, 2022, SpaceQ reports. The spaceport firm also says it has a “letter of intent” for an alternative medium-class launch vehicle for the site. Originally, it had intended to launch the Ukrainian Cyclone 4M booster, with a lift capacity of 5 metric tons to low-Earth orbit. But there are concerns about the availability of the rocket due to Russia’s war against Ukraine.

Mum’s the word from Maritime … In its document, Maritime Launch Services states, “If it is required, the medium-class launch vehicle capability of the Cyclone 4M can be replaced with at least two others that are in development in the United States, one of which with we have a letter of intent.” Presumably this refers to rockets under development by Rocket Lab and Firefly, but for now the Canadian company isn’t saying. (submitted by JS)

NASA rolls SLS rocket to the launch pad. The Space Launch System rocket has reached its pad at Kennedy Space Center and remains on track to attempt a liftoff no earlier than August 29 at 8:33 am ET (12:33 UTC). The rocket’s rollout follows completion of a flight termination system test over the weekend. This was the final major test of the launch system and spacecraft prior to rollout, and it marks the completion of all major pre-launch activities, Ars reports. NASA continues to target three dates to attempt the Artemis I launch: August 29, September 2, and September 5.

Orion to fly a long time … Each of the three upcoming launch opportunities would allow for a “long-class” mission for the Orion spacecraft, which will be uncrewed and fly into lunar orbit for several weeks before returning to Earth and splashing down in the Pacific Ocean. The missions would range in length from 39 to 42 days. The Artemis I mission represents a significant step forward for NASA and its ambitions for a deep space human exploration program. The rocket’s next launch will carry four astronauts around the Moon, and its third launch is scheduled to enable a human landing there, possibly in the mid-2020s.

Europe looking at developing reusable heavy lifter. A deadline is coming up for European countries and companies to respond to an “Invitation to Tender” for a new heavy lift rocket. The European Space Agency issued the tender on June 28, 2022 and plans to close it on September 12. The space agency is seeking preliminary ideas for a “European reusable and cost-effective heavy-lift” rocket. The initial contracts will be small, valued at 200,000 to 500,000 euros.

A huge leap in performance … “This analysis has as its purpose to develop an adapted and more performant transport means to accommodate large space infrastructures (e.g. space-based solar power, space data centre, etc.) and deep space missions,” the document states. “It is foreseen that after 2035, with the European Green Deal initiative, current European launch vehicles will not be able to transport large payloads with the necessary cadence.” This could be a reference to Europe’s interest in space-based solar power. The goal of this vehicle will be to deliver “at least” 10,000 metric tons to orbit a year. That’s, umm, a lot.

Starship inks first commercial satellite customer. Asia’s largest satellite operator, SKY Perfect JSAT Corporation, announced Thursday that it plans to launch its Superbird-9 communications satellite on SpaceX’s Starship rocket. “Superbird-9 will be launched by SpaceX’s Starship launch vehicle in 2024 to geosynchronous transfer orbit,” the company’s news release states. “SpaceX’s Starship is a fully reusable transportation system that will be the world’s most powerful launch vehicle.”

Small satellite, big rocket … The first Starship missions will almost certainly carry the company’s own Starlink satellites into low-Earth orbit. There have also been human missions announced, including Polaris 3 with Jared Isaacman, and the Dear Moon project. But until now there had been no announcements of commercial satellite customers. It seems likely that Superbird-9 could be launched by a Falcon 9 or at least a Falcon Heavy, so perhaps SpaceX gave the Japanese company a discount for being a first mover. In any case, it’s a notable announcement for Starship as the program moves closer to an orbital launch attempt. (submitted by Ken the Bin)

Jacklyn recovery ship to be scrapped. We’ve previously reported that Blue Origin had moved from the large “Jacklyn” rocket recovery ship to a more economical option, similar to the autonomous drone ships that SpaceX uses for the Falcon 9 rocket. But now the Jacklyn ship is being sent from the Port of Pensacola in Florida to Brownsville, Texas, to be scrapped, Space News reports. Blue Origin had already put “tens of millions” of dollars into refitting the 180-meter long ship, which was to catch the first stage of the New Glenn rocket.

Sorry, mom … “Blue Origin is committed to safe and cost-effective access to space, and after careful consideration have made the decision to transition away from the Jacklyn as a landing solution,” a company spokesperson told the publication. A source said the costs of refitting “Jacklyn,” which was named after Blue Origin founder Jeff Bezos’ mother, were far higher than originally anticipated. This necessitated the move toward drone ships. The Brownsville port is a few miles away from where SpaceX is building its Starship vehicle. (submitted by Ken the Bin)

Next three launches

August 19: Long March 2D | Yaogan military satellite | Xichang Satellite Launch Center, China | 17:36 UTC

August 19: Falcon 9 | Starlink 4-27 | Cape Canaveral, Fla. | 19:24 UTC

August 28: Falcon 9 | Starlink 4-23 | Kennedy Space Center, Fla. | 01:52 UTC

Continue Reading


Library’s prized Galileo manuscript turns out to be a clever forgery



Enlarge / Annotations recording Galileo’s discovery of the four moons of Jupiter, from the single-leaf manuscript in the collection of the University of Michigan. The library recently discovered the manuscript is a 20th-century forgery.

Since 1938, one of the most prized items in the University of Michigan library’s collection has been a rare manuscript page allegedly written by Galileo. But after an internal investigation,  the library’s curators have concluded that the manuscript is in fact a fake—and most likely executed by a well-known 20th century forger. The curators were tipped off about the forgery by Georgia State historian Nick Wilding, who became suspicious of the manuscript’s authenticity while working on a biography of Galileo.

“It was pretty gut-wrenching when we first learned our Galileo was not actually a Galileo,” Donna L. Hayward, interim dean of the University of Michigan’s libraries, told the New York Times. Nonetheless, the library opted for transparency and publicly announced the forgery. “To sweep it under the rug is counter to what we stand for,” Hayward said.

The single-leaf manuscript in question purported to be a draft of an August 24, 1609, letter that Galileo wrote to the Doge of Venice describing his observations with a telescope (occhiale) he had constructed. (The final letter is housed in the State Archives in Venice.) Galileo first heard of a marvelous new instrument for “seeing faraway things as though nearby” in a letter from a colleague named Paolo Sarpi, who had witnessed a demonstration in Venice. Unsatisfied with the performance of the available instruments, Galileo built his own, even learning to grind his own lenses to improve the optics.

Portrait of Galileo Galilei by Justus Sustermans, 1636. Uffizi Museum, Florence.
Enlarge / Portrait of Galileo Galilei by Justus Sustermans, 1636. Uffizi Museum, Florence.

Public domain

The first object Galileo studied was the Moon, towards the end of 1609, when Jupiter was closest to the Earth and hence the brightest object in the evening sky (apart from the Moon itself, of course). He noted on January 7, 1610, that Jupiter appeared to have three fixed stars nearby. Intrigued, he returned to looking at the planet the following night, expecting the then-retrograde body to have moved from east to west, leaving the three little stars behind. Instead, Jupiter seemed to have moved to the east.

Puzzled by the planet’s behavior, Galileo returned to the formation repeatedly, observing several key details. First, the little stars never left Jupiter but appeared to be carried along with the planet. Second, as they were carried along, they changed their position with respect to each other and to Jupiter. Finally, he discovered a fourth little star.

Galileo concluded that the objects were not fixed stars but small moons that revolved around the planet. And if Jupiter had four orbiting moons, then the Earth could not be the fixed center of the universe, as most scholars believed at the time. This observation provided the first empirical support for Copernicus’ theory that the Sun rather than the Earth was at the center of the solar system. Galileo published this groundbreaking observation in his book Sidereus Nuncius (Starry Messenger) in March 1610.

Galileo's "cannocchiali" telescopes at the Museo Galileo, Florence.
Enlarge / Galileo’s “cannocchiali” telescopes at the Museo Galileo, Florence.

The top half of the library’s manuscript is the alleged draft of Galileo’s letter to the Doge of Venice, dated circa August 9, 1609. The bottom half, supposedly written months later, contains a series of “doodles” that depict Jupiter’s moons—once thought to be original notes from Galileo’s observations in January 1610.

Enter Nick Wilding, who has exposed Galileo-related forgeries in the past, most notably a copy of Sidereus Nuncius in the possession of a New York City rare book dealer. This copy supposedly included an inscription by Galileo, as well as five of his watercolors of the moon. Although the paper and binding of Sidereus appeared to be genuine, Wilding eventually found that it, along with another copy listed in the 2005 Sotheby’s catalog, both had an identical blotch on the title page that could be traced back to a 1964 facsimile edition. “If [the forger] hadn’t been greedy enough to make two copies, I wouldn’t have been able to prove the forgery,” Wilding told the New York Times in 2012.

When he turned his attention to the Michigan manuscript, Wilding thought that some of the letter forms and word choices seemed odd, and the ink on the top and bottom halves seemed very similar, despite those sections having been (allegedly) written months apart. So he emailed the library requesting information about the document’s provenance, as well as an image of its watermark.

The University of Michigan library acquired the manuscript in 1938 as a bequest from a Detroit businessman named Tracy McGregor. McGregor had purchased the manuscript at auction four years earlier; it had previously belonged to a wealthy collector named Roderick Terry. According to the auction catalog, the manuscript had been authenticated by an archbishop of Pisa named Cardinal Pietro Maffi. The cardinal had two other documents in his collection purportedly signed by Galileo, and Maffi used those documents as comparisons.

But Wilding found that there is no record of the Michigan manuscript in Italian archives. Furthermore, Maffi had acquired the two documents he used for comparison from the notorious early 20th century counterfeiter Tobia Nicotra, calling the cardinal’s authentication into question.

Nicotra was quite the character, described as “perhaps the cleverest forger on record” in contemporary newspaper accounts. Not much is known about him, but he began selling forgeries in the 1920s, allegedly as a means of supporting seven mistresses, which he had deposited in apartments around Milan. (Nicotra also had a wife.) He was likely responsible for 500-600 forgeries of letters, music manuscripts, and other manuscripts attributed to such lofty personages as George Washington, Christopher Columbus, the Marquis de Lafayette, Martin Luther, Leonardo da Vinci, Mozart, Gluck, and Handel, among others.

Nicotra had written a biography of the conductor Arturo Toscanini and then sold the conductor’s son, Walter, a Mozart “autograph.” Walter eventually discovered the autograph was a forgery. He teamed up with Milanese detective Giorgio Florita to bring Nicotra to justice. The police who raided the man’s Milan apartment found a veritable “forgery factory,” per Wilding. On November 9, 1934, Nicotra was sentenced to two years in jail and then faded into obscurity. But his forgeries likely still circulate through collections around the world.

Michigan’s conservation laboratory determined that the ink and paper of its manuscript were consistent with the period when Galileo made his observations, but any hope of authenticity was dashed after Wilding’s investigations into the watermark. The watermark is a circle with a three-leafed clover, with the monogram “AS/BMO.” Wilding found that “BMO” referenced the Italian city of Bergamo, and the watermark matched documents dating back to 1790—150 years after Galileo made his discoveries. Another Galileo document (a 1607 letter) at the Morgan Library & Museum in New York also has this monogram, and is thus also a forgery, per Wilding.

Both the Morgan and the University of Michigan Library are updating their catalogs accordingly. “The library’s assessment of the letter in light of Wilding’s findings will require a reconsideration of its place in the collection, beginning with an update to its metadata,” the library said in its statement. “In the future, it may come to serve the research, learning, and teaching interests in the arena of fakes, forgeries, and hoaxes, a timeless discipline that’s never been more relevant.”

Continue Reading