Tag Archives: sunlight

Wide-scale use of solar technology in cities would almost cover their full energy needs

Fully-integrating solar panels into buildings could make cities almost self-sustaining, according to new research.

Image credits Ulrike Leone.

Solar panels get a lot of bad press for having a low energy output; individually, that may be so. A small, single panel will not be able to keep your home lit, warmed, and all the appliances running. But the secret with solar energy is to think at scale, a new paper suggests, and to make the most of every bit of free space. According to the findings, the City of Melbourne could generate 74% of its electricity needs if solar technology was to be integrated into the roofs, walls, and windows of every building.

This study is the first to estimate the viability and impact of integrating several types of solar technology including window-integrated and rooftop-mounted photovoltaics on a city-wide scale. The results are promising, suggesting that the City of Melbourne could greatly reduce its reliance on energy produced through the burning of fossil fuels.

Lighting the way

“By using photovoltaic technology commercially available today and incorporating the expected advances in wall and window-integrated solar technology over the next ten years, we could potentially see our CBD (central business district) on its way to net zero in the coming decades,” said lead author Professor Jacek Jasieniak.

“We began importing coal-fired power from the LaTrobe Valley in the 1920s to stop the practice of burning smog-inducing coal briquettes onsite to power our CBD buildings, and it’s now feasible that over one hundred years later, we could see a full circle moment of Melbourne’s buildings returning to local power generation within the CBD, but using clean, climate-safe technologies that help us meet Australia’s Net Zero 2050 target.”

The authors report that existing rooftop photovoltaic technology alone could dramatically reduce Melbourne’s carbon footprint. If technologies that are still being developed, such as high-efficiency solar windows or facade-integrated panels, are also taken into account, solar energy can become the leading source of energy in the city. These estimates hinge on the assumption that such technologies are integrated on a wide scale across the city.

For the study, the team compared the electrical energy consumption in Melbourne in 2018 to an estimate of the energy that could be produced through wide use of building-integrated solar systems. Consumption figures were obtained from Jemena and CitiPower & Powercor distribution companies through the Centre for New Energy Technologies (C4NET), an independent research body in Victoria, Australia. The production estimates were based on city-wide mathematical modelling.

Out of the total potential energy that solar power could provide, rooftop-mounted solar panels could generate 88%, with wall-integrated and window-integrated solar delivering 8% and 4% respectively. However, wall- and window-mounted solar technologies lost a lot less of their efficiency during the winter months relative to rooftop-mounted panels, the models showed. In other words, although they have a lower total output potential, these two types of technology deliver power more reliably and at more constant levels throughout the year.

Building height had a particular impact only on window-integrated solar technologies; in highrise neighborhoods, its potential rose to around 18% of the total generated energy. In areas with low average building height, the total wall and window areas available are small, reducing their overall potential to generate power. The window-to-wall surface ratio also tends to be greater in commercial buildings compared to residential buildings.

The modeling took into account the impact of shadows cast in the city by elements such as buildings, shading systems, or balconies, and natural factors such as sun incidence angle and total solar potential of different areas across Melbourne. The technologies used as part of the simulations were selected based on their technical characteristics, limitations, and costs of installation and operation.

All in all, the study worked with the 37.4 km2 area of central Melbourne, which consists mainly of residential and commercial buildings. In 2019, a total of 35.1 km2 of the studied perimeter was built floor area. This area was selected because it offered one the greatest potential for window-integrated solar in Melbourne, the team explains.

“Although there’s plenty of policies supporting energy-efficiency standards for new buildings, we’re yet to see a substantial response to ensuring our existing buildings are retrofitted to meet the challenges of climate change,” says co-author Dr. Jenny Zhou. “Our research provides a framework that can help decision-makers move forward with implementing photovoltaic technologies that will reduce our cities’ reliance on damaging fossil fuels.”

“In the near future, market penetration and deployment of high-efficient solar windows can make a substantive contribution towards the carbon footprint mitigation of high-rise developments,” adds first author Dr. Maria Panagiotidou. “As the world transitions towards a net-zero future, these local energy solutions would play a critical role in increasing the propensity of PVs within urban environments.”

The paper “Prospects of photovoltaic rooftops, walls and windows at a city to building scale” has been published in the journal Solar Energy.

Climate change is making the Earth dimmer, which, in turn, warms up the climate

In an unexpected turn of events, climate change seems to be making the Earth a little bit dimmer, according to new research.

Image credits Arek Socha.

One of the properties that define planets throughout space is their ‘albedo’. Multiple different elements factor into this property which, in its simplest definition, is the measure of how much incoming light a planetary body reflects. A planet’s albedo can thus have a significant effect on environmental conditions across its surface.

But the opposite is also true, and climate conditions on the surface can influence a planet’s overall albedo. New research explains that climate change is already affecting Earth’s albedo, causing a significant drop in our planet’s ability to reflect light over the last 20 years or so.

No beam-back

“The albedo drop was such a surprise to us when we analyzed the last three years of data after 17 years of nearly flat albedo,” said Philip Goode, a researcher at New Jersey Institute of Technology and the lead author of the new study.

The authors worked with earthshine data recorded by the Big Bear Solar Observatory in Southern California from 1998 to 2017. Satellite readings of earthshine over the same timeframe were also used in the study. Earthshine is the light reflected from the Earth into space, and it is what makes the Moon so bright in the night’s sky.

All in all, the team reports, the Earth is beaming back roughly one-half of a watt less per square meter of its surface than it did 20 years ago. For perspective, the typical lightbulb uses around 60 watts. A single LED uses around 0.015 watts. The authors explain that it’s equivalent to a 0.5% decrease in the Earth’s reflectance.

The two main components deciding how much sunlight reaches the Earth are how bright the Sun shines, and how reflective our planet is. But the team reports that the drop in albedo they’ve observed did not correlate with any periodic changes in the Sun’s brightness — meaning that the drop was caused entirely by changes in how reflective the Earth is.

This drop is mostly powered by warming ocean waters. The authors point to a reduction in bright, reflective low-lying clouds over the eastern Pacific Ocean over the last two decades, as shown by measurements taken as part of NASA’s Clouds and the Earth’s Radiant Energy System (CERES) project. Sea surface temperature increases have been recorded in this area following the reversal of the Pacific Decadal Oscillation (PDO).

A dimmer Earth means that the planet is absorbing much more of the incoming solar energy into Earth’s climate systems. Here, it’s likely to contribute to global warming. The authors estimate that this extra sunlight is on the same magnitude as the sum of anthropogenic climate forcing over the last two decades.

“It’s actually quite concerning,” said Edward Schwieterman, a planetary scientist at the University of California at Riverside who was not involved in the new study. For some time, many scientists had hoped that a warmer Earth might lead to more clouds and higher albedo, which would then help to moderate warming and balance the climate system, he said. “But this shows the opposite is true.”

The paper “Earth’s Albedo 1998–2017 as Measured From Earthshine” has been published in the journal Geophysical Research Letters.

New study shows sunlight can inactivate SARS-CoV-2

Increasingly, it is being shown that COVID-19 tends to spread faster and easier indoor than outdoor.

Previous studies have demonstrated that SARS-CoV-2, the virus that causes COVID-19, is stable on surfaces for extended periods of time, under indoor conditions.

A research from China showed that coronavirus transmission still takes place despite changing weather conditions in different parts of the country — ranging from cold and dry to warm and humid. A study in Hong Kong using SARS-CoV-2 in a lab solution showed that increasing temperature decreased the amount of viable virus that could be detected. No infectious virus remained after 30 minutes at 56° Celsius and five minutes at 70°C was enough to inactivate the pathogen.

Now, a new study by researchers at the National Biodefense Analysis and Countermeasures Center, a government biodefense research laboratory created by the U.S. Department of Homeland Security, shows that natural sunlight can rapidly inactivate SARS-CoV-2 on surfaces.

The findings, which come with caveats, suggest that the potential for fomite transmission may be significantly reduced in outdoor environments exposed to direct sunlight.

Sunlight vs COVID

To evaluate the influence of simulated sunlight on the persistence of SARS-CoV-2 on surfaces, the researchers exposed concentrated virus suspended in either simulated human saliva or culture media and then dried on stainless steel coupons mounted in a chamber to a light spectrum designed to represent natural sunlight. The coupons were exposed to the simulated sunlight for differing exposures, ranging from 2 to 18 minutes, to allow estimation of the viral inactivation rate. For comparison, the researchers also exposed a series of contaminated coupons in the chamber with no simulated sunlight for 60 minutes.

The results showed that under levels of simulated sunlight representative of midday on the summer solstice at 40°N latitude (the 40th Parallel), 90% of infectious virus is inactivated every 6.8 minutes in simulated saliva dried on a surface and every 14.3 minutes in cultured media dried on a surface. Significant inactivation also occurred under lower simulated light levels but at a slower rate. Inactivation rates were near zero on the coupons not exposed to sunlight.

The inactivation rate of SARS-CoV-2 was approximately two-fold greater in simulated saliva than in culture media. However, the researchers say it is unclear if the viral concentrate in simulated salvia is representative of contaminated saliva from an infected individual. This is good news but do not assume that summer months will be safer.

Sunlight has been in the COVID-19 news cycle for another reason – it is a great natural source of vitamin D, which has several health benefits, including an increased resistance to infectious diseases. When it comes to COVID-19, research is limited but clinical trials have started in Spain and France to see if vitamin D improves outcomes for COVID-19 patients. Both studies are expected to end in July 2020. In the meantime, continue to take appropriate steps to protect yourself and those around you.

Roughly 98% of plastic waste in the ocean dissolves due to sunlight

Around 98% of all the plastic waste going into the ocean is unaccounted for. A new paper looks into where it winds up, and its effect on marine life.

It’s hard to overstate just how much plastic humanity has dumped into the ocean. Trillions of bits of plastic float into massive “garbage patches” along the subtropical gyres (rotating ocean currents). These patches have a dramatic impact on ocean life, ranging from the largest mammals to the humble bacteria.

And yet, these immense plastic patches only account for 1% to 2% of all the plastic going into the ocean. Which is quite a scary thought. One promising theory is that sunlight-driven chemical reactions break the materials down until they lose buoyancy, or become too small to be captured by researchers. However, direct, experimental evidence for the photochemical degradation of marine plastics remains rare.

Where’s the plastic?

“For the most photoreactive microplastics such as expanded polystyrene and polypropylene, sunlight may rapidly remove these polymers from ocean waters. Other, less photodegradable microplastics such as polyethylene, may take decades to centuries to degrade even if they remain at the sea surface,” said Shiye Zhao, Ph.D., senior author of the paper.

“In addition, as these plastics dissolve at sea, they release biologically active organic compounds, which are measured as total dissolved organic carbon, a major byproduct of sunlight-driven plastic photodegradation.”

The team, which included members from Florida Atlantic University’s Harbor Branch Oceanographic Institute, East China Normal University, and Northeastern University wanted to verify the theory. They selected polymers that are often seen in the garbage patches, and plastic-fragments collected from the surface waters of the North Pacific Gyre, and irradiated them for approximately two months using a solar simulator.

During this time, the team captured the kinetics of plastic degradation. To assess degradation levels, they used optical microscopy, electron microscopy, and Fourier transform infrared (FT-IR) spectroscopy.

All in all, the team reports, plastic dissolution led to an increase in carbon levels in their surrounding water and reduced particle size of the plastic samples. The irradiated plastics fragmented, oxidized, and changed in color. Recycled plastics, overall, degraded more rapidly than polymers such as polypropylene (e.g. consumer packaging) and polyethylene (e.g. plastic bags, plastic films, and containers including bottles), which were the most photo-resistant polymers studied.

Based on the findings, the team estimates that recycled plastics tended to degrade completely in 2.7 years and that plastics in the North Pacific Gyre degrade in 2.8 years. Polypropylene, polyethylene, and standard polyethylene (which see ample use in food packaging) degrade completely in 4.3, 33, and a whopping 49 years, respectively, the team estimates.

The compounds leaching out of the plastic as it degrades seem to be broadly biodegradeable, the team reports. While levels of plastic-sourced carbon in ocean water pale in comparison to natural marine-dissolved organic carbon, the team found that it can inhibit microbial activity. The carbon from degraded plastics was readily used by marine bacteria, the team adds.

“The potential that plastics are releasing bio-inhibitory compounds during photodegradation in the ocean could impact microbial community productivity and structure, with unknown consequences for the biogeochemistry and ecology of the ocean,” said Zhao.

“One of four polymers in our study had a negative effect on bacteria. More work is needed to determine whether the release of bioinhibitory compounds from photodegrading plastics is a common or rare phenomenon.”

Samples in the study included post-consumer microplastics from recycled plastics like a shampoo bottle and a disposable lunch box (polyethylene, polypropylene, and expanded polystyrene), as well as standard polyethylene.

The paper “Photochemical dissolution of buoyant microplastics to dissolved organic carbon: Rates and microbial impacts” has been published in the Journal of Hazardous Materials.

Sunlight might affect gut microbiome diversity

Researchers at the University of British Columbia in Canada have found a significant link between exposure to ultraviolet rays and an increase in gut bacterial diversity. The findings could prove important in managing autoimmune diseases known to be associated with gut bacterial diversity, such as inflammatory bowel disease.

Credit: Pixabay.

Ultraviolet (UV) designates a band of the electromagnetic spectrum with wavelengths ranging from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. Our senses cannot detect UV rays — not until the damage is done — which is why they can be especially dangerous. Too much time in the sun causes sunburns, eye damage, accelerate aging, and skin cancer.

There are 2 main types of UV rays that interact with our skin.

  • UVB, which is responsible for the majority of sunburns, and
  • UVA, which penetrates deep into the skin. It ages the skin, but contributes much less towards sunburn.

Although prolonged exposure to UV radiation can be very harmful, we also require moderate exposure in order to live healthily. Research has shown a link between UV exposure and the synthesis of vitamin D, which promotes the formation and strengthening of bones (a deficiency will cause bone softening diseases, which then causes rickets in children and osteomalacia in adults), strengthens the immune system, and offers protection against some cancers.

In the study, 21 female participants received three 60-second full-body UVB exposure sessions over the course of one week. The researchers drew blood and fecal samples from each subject at the beginning and end of the trial in order to analyze changes in vitamin D and gut bacteria. Half of the participants had taken vitamin D supplements during the prior three winter months.

The subjects who didn’t take vitamin D supplements experienced an increase in alpha and beta gut microbiome diversity. They also experienced a 10% increase in blood serum vitamin D concentration after the week-long UVB exposure. On the other hand, those who took vitamin D supplements did not experience an increase in gut microbiome diversity. This suggests that vitamin D is the mediating factor between UVB exposure and gut microbial activity.

“Prior to UVB exposure, these women had a less diverse and balanced gut microbiome than those taking regular vitamin D supplements,” says lead-author Bruce Vallance, from the University of British Columbia. “UVB exposure boosted the richness and evenness of their microbiome to levels indistinguishable from the supplemented group, whose microbiome was not significantly changed.”

Although the researchers haven’t identified a formal mechanism, they think that the initial exposure to UVB light alters the immune system — first at the level of the skin, then more systematically throughout the body, affecting how bacteria interact with the environment inside the intestines. Previously, studies have shown that inflammatory bowel disease symptoms can worsen when the body experiences vitamin D deficiency, which strengthens the idea sunlight exposure and gut health are somewhat connected.

Next, the team plans on performing similar studies on a larger cohort of subjects in order to investigate this link better.

“The results of this study have implications for people who are undergoing UVB phototherapy, and identifies a novel skin-gut axis that may contribute to the protective role of UVB light exposure in inflammatory diseases like MS and IBD,” says Vallance.

The findings appeared in the journal Frontiers in Microbiology.

natural light led

The LED sun: artificial light completely mimics properties of natural sunlight

natural light led

In many ways, society was transformed by the advent of the light bulb. Suddenly, people could now stay up late, work, study or enjoy each other’s company without being at the mercy of the sun. A side effect, however, is that our bodies natural wake/sleep patterns have been considerably altered and artificial light is nothing like the real deal — the sun’s life-nurturing rays which are known to have a significant impact on our health and mood. In an effort to help people who spend long hours in poorly lit offices or live in areas with little sunlight (Beijing, anyone?), a team of Italian engineers has developed a remarkable LED-based lighting system which mimics natural sunlight. Yes, this is a low-input LED sun!

led sun

The sunshine we love to greet each morning isn’t exactly the same as the rays leaving the sun. In between the outer atmosphere and Earth’s surface, the properties of light become altered through a process known as Rayleigh scattering. Ever wonder why the sky is blue? That’s Rayleigh scattering at work — the scattering of light due to molecules in the air, which can be extended to scattering from particles up to about a tenth of the wavelength of the light. This phenomenon is most effective at short wavelengths (the blue end of the visible spectrum), hence the color of the sky. Red just goes through.

natural light

CoeLux, the company behind the project, developed a thin coating of nanoparticles to simulate Rayleigh scattering. This way, miles of atmospheric scattering has been replicated within a few millimeters of space between the coating and the LED white light source.  Professor Paolo Di Trapani of Italy’s University of Insubria is the mastermind behind the 10-year-long project. By tweaking the shape, size and aspect ratio of the nanoparticles, Trapani’s team was able to replicate natural light from color and saturation to light quality. The result is spectacular — a LED light that looks like a skyline!

natural light

According to CoeLux, the light is indistinguishable from natural light for humans, cameras or computers alike. I’m as skeptical as you are, but allegedly all of these photos are unaltered.


If you’re interested in adding something like this in your home, you can choose from three lighting settings: Mediterranean, Tropical, and Nordic. They are also working on additional offerings, including simulated daytime sequences (sunrise through sunset) and color variations to reflect different kinds of weather conditions. At a few tens of thousands of dollars per installation, this might be a bit stiff for the average buyer. Nevertheless, this is extremely impressive and once the pricing goes down, indoor lighting might be transformed forever.

lighting natural system

Check out Prof. Trapani’s explanation of how the system works below.


Semi-artificial photosynthesis points the way to a viable hydrogen economy

Researchers from the University of Cambridge look to plants for a new energy revolution.


Oxygen, hydrogen (left) and water molecules (right).
Image credits Luis Romero / Flickr.

Looking for new and more efficient ways of harvesting solar energy, a team of researchers from St John’s College has turned plants to the job. The team has successfully split water molecules into hydrogen and oxygen by altering and improving on natural photosynthetic processes. Photosynthesis is the process plants use to convert sunlight into energy.

Lettuce make fuel

Photosynthesis is arguably the most important process for life on Earth. The process — which uses energy in sunlight to break down water and carbon dioxide — provides the energy and building blocks that plants need to grow. In turn, plants act as primary producers: they form the first link of virtually every trophic network on the planet, essentially feeding the rest of the planet. Moreover, photosynthesis is the source of nearly all the oxygen in the atmosphere today. In its absence, oxygen (a very reactive gas) would bind with chemical compounds or would be used up in biological respiration pretty quickly, and we’d all choke to death. Which would be sad.

Not content to let the process drive just our biology, the team — led by St John’s College PhD student Katarzyna Sokół — worked on turning it into a power source.

Hydrogen has long been considered a viable — and powerful — alternative to fossil fuels. In fact, the first internal combustion engine ever built used a mixture of hydrogen and oxygen, not fossil fuels, to generate energy. It was designed by Francois Isaac de Rivaz, a Swiss inventor, all the way back in 1806. However, it never really caught on, as we didn’t know of any fast and cheap way of mass-producing the gas.

Artificial photosynthesis has yet to reach a point where it can supply enough hydrogen for wide-scale use, mostly because it relies on the use of catalysts, which are often expensive and toxic. On the other hand:

“Natural photosynthesis is not efficient because it has evolved merely to survive so it makes the bare minimum amount of energy needed — around 1-2 per cent of what it could potentially convert and store,” says Katarzyna Sokół, who is also the paper’s first author.

This means that neither can support an industrial-level economy based on hydrogen.


Experimental two-electrode setup showing the photoelectrochemical cell illuminated with simulated solar light.
Image credits Katarzyna Sokół.

The team’s new paper details their efforts to change this state of affairs. Using a combination of biological components and manmade technologies, they managed to convert water into hydrogen and oxygen at high efficiency using only sunlight — a process known as semi-artificial photosynthesis. As part of their research, the team had to remove genetic limitations on photosynthesis that had been imposed millennia ago.

“Hydrogenase is an enzyme present in algae that is capable of reducing protons into hydrogen. During evolution this process has been deactivated because it wasn’t necessary for survival,” Sokół explains, “but we successfully managed to bypass the inactivity to achieve the reaction we wanted — splitting water into hydrogen and oxygen.”

The team is the first to successfully create semi-artificial photosynthesis driven solely by sunlight. Their method was over 80% more efficient than natural photosynthesis.

The groundwork they laid down in integrating organic and inorganic materials into semi-artificial devices also provides new avenues of research into other systems for solar energy capture, they add.

“It’s exciting that we can selectively choose the processes we want, and achieve the reaction we want which is inaccessible in nature,” Sokół explains.

“This could be a great platform for developing solar technologies. The approach could be used to couple other reactions together to see what can be done, learn from these reactions and then build synthetic, more robust pieces of solar energy technology.”

The paper has been published in the journal Nature.