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Why Do Trees Change Color? | Earth Wise

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We had a particularly colorful fall in the Northeast this year.  Almost everywhere you looked, there were brilliant displays of yellow, orange, and red.  The colors of fall are a result of chemistry and environmental events that may have taken place many months in the past.

The color of leaves comes from 4 pigments whose effects are governed by photosynthesis.  The one that is actually used in photosynthesis is chlorophyll and it causes leaves to be green.  But when a tree begins to prepare for dormancy, it stops producing chlorophyll, the green pigmentation fades, and the other pigments that were already in the leaves become visible.

There are xanthoplylls, which are the yellow pigments that are seen the most in fall trees.  They are the same pigments that color egg yolks and sometimes parts of the human eye.  They are only produced by plants and appear in humans and animals only through consumption.

There are carotenes, which are the orange pigments found in fruits and vegetables, such as carrots, oranges, some bell peppers and squashes.

And there is anthocyanin, which is the pigment found in blueberries, blackberries, and red or violet roses.  Its color depends on the pH level of the plant; higher pH leads to darker color.  This is the pigment seen in red maples, black cherry trees, Shumard oaks, and more.  Only 10% of trees in temperate climates produce anthocyanin and its red pigmentation and most of those trees are in New England.

All these pigments serve purposes.  They help trees absorb light energy, prevent sun damage, and even regulate how much energy chlorophyll produces.

There are complicated chemical and environmental factors at play in fall foliage but when they come together like they did this year, it’s a magnificent spectacle.

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Why Do Trees Change Color?

Photo, posted October 17, 2020, courtesy of John Brighenti via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Better Paint For Cooler Buildings | Earth Wise

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A research team led by scientists at UCLA have developed a super-white paint that reflects as much as 98% of incoming heat from the sun.  Such paint, if used on rooftops and other parts of buildings, could have a major impact on reducing the costs of keeping buildings cool.

Passive daytime radiative cooling is a well-known method to keep buildings cooler.  By having building surfaces reflect sunlight and radiate heat into space, building temperatures can be significantly lowered.  This in turn cuts down on air conditioner use and associated carbon emissions.

A roof painted white will result in lower indoor temperatures than a darker roof.  But a white roof will do even more:  it can reject heat at infrared wavelengths that are invisible to our eyes.  This results in even more radiative cooling.

The best performing white paints currently available reflect about 85% of incoming solar radiation.  The rest is absorbed by materials in the paint.  The new research has identified simple modifications in paint ingredients that lead to a major increase in reflectivity.

Current reflective white paints use titanium dioxide, which absorbs UV radiation and therefore heats up under sunlight.  The researchers studied replacing it with other substances such as barite – an artist’s pigment – or with powdered Teflon, both of which allow the paint to reflect more of the sun’s radiation. 

Many cities are encouraging the use of cool-roof technologies on new buildings.  Using the most reflective coatings possible on rooftops, if applied on a sufficiently large scale, could have a real impact on climate change as well as saving significant amounts of energy used for running air conditioners in buildings.

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UCLA-led Team Develops Ways to Keep Buildings Cool with Improved Super White Paints

Photo, posted August 15, 2012, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Massachusetts And Energy Policy | Earth Wise

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The transition to a renewables-based energy future continues to accelerate, but there are still many forces that can slow it down.  Government policy has a major role to play.  At the moment, the federal government is trying to prop up the fossil fuel industry with financial incentives and rampant deregulation.  So more than ever, innovative policies at the state level are essential drivers for revolutionizing the energy system.

One state where policy is trying to make a big difference is Massachusetts, which has created the Clean Peak Energy Standard or CPS, finalized and approved in late March and now taking effect.   A clean peak standard is a regulatory tool to reduce the costs and environmental impact of periods when electricity demand is highest, and generation tends to be the most polluting.  The CPS requires electric retailers to procure a minimum percentage of their annual electricity sales from renewable generation or energy storage.  That minimum amount will increase each year.

The CPS is formulated to incentivize better utilization of clean energy technologies to supply power when energy demand is high.  The problem is that there are times when the sun is not shining and the wind isn’t blowing, but energy demand is at its highest.  The solution is to use energy storage technologies that can supply power when it is needed.  Furthermore, storage can be relied upon during times of extreme weather that cause power outages.

Massachusetts has already started using energy storage in its grid.  The small town of Sterling installed an energy storage system in 2016 that provides crucial backup power to the police station and emergency dispatch center, thereby keeping first responder operations running even during extended power outages.

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Massachusetts is setting the benchmark for nationwide clean energy transformation

Photo, posted March 30, 2012, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Side Effects Of Geoengineering | Earth Wise

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As the world struggles to reduce the greenhouse gas emissions that are warming the global climate, some researchers are exploring proposals to deliberately engineer climate changes to counteract the warming trend.  One of the most widely discussed approaches is to shade the Earth from a portion of the sun’s heat by injecting the stratosphere with reflective aerosol particles.  Proponents of this idea point out that volcanoes do essentially the same thing, although generally for only a limited amount of time.  Particularly large eruptions, such as the Krakatowa eruption of 1883, wreaked havoc with weather around the world for an entire year.

Schemes to launch reflective aerosols – using planes, balloons, and even blimps – appear to be quite feasible from the standpoint of physically accomplishing them. But this says nothing about the political, ethical, and societal issues involved.  The point is that such an approach could indeed lower global temperatures and thereby potentially offset the warming effects of greenhouse gases.

A study by scientists at MIT looked at what other effects such a solar geoengineering project might have on the climate.  Their modeling concluded that it would significantly change storm tracks in the middle and high latitudes.  These tracks give rise to cyclones, hurricanes, and many more ordinary weather phenomena.

According to the study, the northern hemisphere would have weakened storm tracks, leading to less powerful winter storms, but also stagnant conditions in summer and less wind to clear away air pollution.  In the southern hemisphere, there would be more powerful storm tracks.

Aside from turning the world’s weather patterns inside out, solar geoengineering would do nothing to address the serious issue of ocean acidification caused by increasing carbon dioxide levels.

As many have pointed out, playing the geoengineering game would have many unintended consequences.

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Study: Reflecting sunlight to cool the planet will cause other global changes

Photo courtesy of MIT.

Earth Wise is a production of WAMC Northeast Public Radio.

Powering Amazon By The Sun | Earth Wise

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Amazon.com is a multinational conglomerate company that sells nearly $300 billion dollars a year worth of products, employs over 800,000 people, and by any measure, consumes a tremendous amount of resources.  In terms of its environmental impact, Amazon is estimated to be responsible for the emission of 50 million tons of CO2 annually, which is more than the yearly total for countries like Switzerland, Ireland, New Zealand, Denmark, and about 140 other countries.

Amazon is trying to reduce its environmental impact.  The company recently announced five new renewable energy projects in China, Australia and the U.S. as part of its commitment to reach 80% renewable energy by 2024, 100% renewable energy by 2030, and to reach net zero carbon by 2040.

The projects include a 100 MW solar project in Shandong, China, a 105 MW solar project in New South Wales, Australia, two solar projects in Ohio (one 200 MW and one 80 MW), and a 130 MW solar project in Virginia.

To date, Amazon has announced 31 utility-scale wind and solar renewable energy projects as well as 60 solar rooftops on fulfillment centers and sort centers around the world.  Taken together, these projects provide almost 3 GW of capacity and will deliver more than 7.6 million MWh of renewable energy annually.

In order for the world to meet the climate goals set by the Paris Agreement, it will take more than just countries to make and keep commitments.   Whatever else one may think about Amazon’s place in the world, their latest efforts for the environment are a big step in the right direction.

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Amazon announces five new utility-scale solar projects to power operations in China, Australia, and the US

Photo, posted November 16, 2018, courtesy of Todd Van Hoosear via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Figuring Out Photosynthesis | Earth Wise

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Plants have been harnessing the sun’s energy for hundreds of millions of years. Algae and photosynthetic bacteria have been doing the same for even longer, all with remarkable efficiency and resiliency. 

People have used the energy of the sun in one way or another for millennia, but only recently have we gotten sophisticated about it by using devices like solar panels and sensors.  And we still have a long way to go to get anywhere close to the efficiency of plants. It’s no wonder, then, that scientists have long sought to understand exactly how photosynthesis works.

Scientists from the U.S. Department of Energy’s (DOE) Argonne National Laboratory, and collaborators at Washington University in St. Louis, recently solved a critical part of the age-old mystery of photosynthesis, studying the initial, ultra-fast events through which photosynthetic proteins capture light and use it to initiate a series of electron transfer reactions.  Electrons in plants have two possible pathways to travel but only use one.   

But as a result of their efforts, the scientists are now closer than ever to being able to design electron transfer systems in which they can send an electron down a pathway of their choosing. 

By gaining the ability to harness the flow of energy, it may be possible to incorporate new design principles in non-biological energy systems. This could allow us to greatly improve the efficiency of many solar-powered devices, potentially making them far smaller. Understanding the intricacies of photosynthesis creates a tremendous opportunity to open up completely new disciplines of light-driven biochemical reactions, perhaps even ones that haven’t been envisioned by nature.

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Scientists unravel mystery of photosynthesis

Photo, posted June 14, 2017, courtesy of Alex Holyoake via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Clouds And Global Warming | Earth Wise

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Recent climate models from multiple organizations project that the amount of warming that doubling atmospheric carbon dioxide would cause would be much more than previously estimated.  And one of the significant changes to the models relates to the role of clouds.

Clouds have long been a major uncertainty in climate calculations.  Clouds can shade the earth and thereby provide cooling.  But clouds can also trap heat.  Which effect dominates depends on how reflective the clouds are, how high up they are, and whether it is day or night.  The dynamics of clouds are complicated.

If you fly across the ocean, you will see blankets of low clouds extending for hundreds of miles.  These marine stratus and stratocumulus clouds predominantly cool the Earth.  In fact, they shade roughly a fifth of the oceans and reflect 30-60% of the solar radiation that hits them back into space.

Recent studies indicate that as global temperatures rise, these clouds are likely to become thinner or burn off entirely, leaving more clear skies through which the sun may add another degree Celsius or more to global warming.

The concerns about clouds are part of the larger issue about feedbacks in warming the world.  It has long been clear that the greenhouse effect of doubling CO2 levels in the atmosphere would raise global temperature.  But there are amplifying feedback effects.  Melting large areas of snow and ice reduces reflectivity and allows the land and oceans to absorb more heat.  More water vapor entering the atmosphere traps more heat.  And now clouds are another concern.

Overall, these effects are leading to climate models predicting much larger global temperature increases, which is a scary prospect for the world.

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Why Clouds Are the Key to New Troubling Projections on Warming

Photo, posted September 10, 2006, courtesy of Nicholas A. Tonelli via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A Possible Storage Breakthrough: Solar Energy | Earth Wise

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Solar energy is a nearly unlimited resource, but it is only available to us when the sun is shining.  For solar power to provide for the majority of our energy needs, there needs to be a way to capture the energy from the sun, store it, and release it when we need it.  There are many approaches to storing solar energy, but so far none have provided an ideal solution.

Scientists at the Chalmers Institute of Technology in Sweden have developed a way to harness solar energy and keep it in reserve so it can be released on demand in the form of heat—even decades after it was captured. Their solution combines several innovations, including an energy-trapping molecule, a storage system, and an energy-storing laminate for windows and textiles.

The energy-trapping molecule is made up of carbon, hydrogen, and nitrogen.  When hit by sunlight, the molecule captures the sun’s energy and holds on to it until it is released as heat by a catalyst.  The specialized storage unit is claimed to be able to store energy for decades.  The transparent coating that the team developed also collects solar energy and releases heat.  Using it would reduce the amount of electricity required for heating buildings.

So far, the team has concentrated on producing heat from stored solar energy.  It is unclear whether the technology can be adapted to produce electricity, which would be even more valuable.  In any event, the team does not yet have precise cost estimates for its technology, but there are no rare or expensive elements required, so the economics seem promising.  There is much more work to be done, but this could be a very important technology for the world’s energy systems.

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An Energy Breakthrough Could Store Solar Power for Decades

Photo courtesy of 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.

Solar-Powered Desalination

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Turning seawater into drinking water is an energy-intensive process and is therefore pretty expensive.  Worldwide, one third of people don’t have reliable access to safe drinking water and they are the least able to afford expensive ways to get it.   By 2025, half of the world’s population is expected to live in water-stressed areas.

At a newly-constructed facility in Kenya, a nonprofit company called GivePower has built a desalination system that runs on solar power.  The system started operating in the coastal area of Kiunga in July 2018 and can create nearly 20,000 gallons of fresh drinking water each day – enough for 25,000 people.

GivePower started in 2013 as a nonprofit branch of SolarCity, the solar-panel company that ultimately merged with Tesla in 2016.  However, GivePower spun off as a separate enterprise shortly before that.

GivePower mostly focuses on building solar-energy systems to provide electricity across the developing world. 

Desalination technology is not new, but it is notoriously energy-intensive because it requires high-power pumps.  The GivePower system is integrated with a solar microgrid that makes use of Tesla batteries to store energy for when the sun is not shining. 

Local residents pay about a quarter of one cent for every quart of water from the system.  The Kiunga community has faced ongoing drought and before the GivePower system was installed, was forced to drink from salt water wells, which present serious health risks.

The GivePower system cost $500,000 to build and is expected to generate $100,000 a year, to be eventually used to fund similar facilities in other places.

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A solar-powered system can turn salt water into fresh drinking water for 25,000 people per day. It could help address the world’s looming water crisis.

Photo courtesy of GivePower.

Earth Wise is a production of WAMC Northeast Public Radio.

Complications For New York Solar Farms

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A study by engineers at Cornell University looked at the implications of adding utility-scale solar farms throughout New York State.  Adding such farms could reduce demand for electricity from conventional sources by nearly 10% in some places.  But the engineers caution that winters in upstate New York could create some novel problems for the state’s power system.

Electrical energy demand tends to be low around midday when many people are not home.  Electrical production from solar farms is high at that time when the sun is at its highest position in the sky.  This can lead to what power system operators call “ramping”, which is the term for rapid increases or decreases in demand.

This sort of ramping was first discussed in California years ago.  When people wake up and prepare for the day, there is a morning peak in electrical load, which occurs before solar production ramps up.   When people get home from work in the evening, energy demands create a second peak.  A graph of this lack of synchronicity of load and supply looks a little like the shape of a duck and is popularly known as the duck curve.

The Cornell engineers figured out that maximum ramping in New York – where electrical demand and electricity supply from solar farms are out of synch- will take place in the winter.  In fact, when there are several days of sunshine in a row during winter, the largest ramping in the New York power system will take place.

The general issue of having solar energy available when it is most needed is one that is the driver for energy storage technology. If the energy can be provided when demand calls for it, there would be no more ramping.

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Winter could pose solar farm ‘ramping’ snag for power grid

Photo, posted September 8, 2015, courtesy of New York National Guard via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Sunlight As A Cash Crop

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It isn’t so easy to be a farmer these days.  Farming has always involved long hours, hard work and the uncertainties of weather and yield.  The 21st Century has added new and unique challenges such as increasingly unpredictable weather, insect infestation and disease, and low commodity prices.  Add in sudden tariffs and farmers struggle even more to make ends meet.  The default rate for farmers’ loans is the the highest in at least nine years.

One thing that remains reliable for farmers is the sun.  It rises in the morning and goes down at night.  The sun can be trusted, unlike politicians, rain, or commodity prices.  These days, many farmers are taking advantage of the dependability of the sun to make money from a new cash crop: solar energy.

The trend is spreading.  North Carolina has been a leading solar energy state for several years and a 2017 report found that solar energy generates 30% of the income of many farms.  Typical annual rent payments for farmland by solar companies range from $500 to $1,400 per acre in North Carolina.

A growing list of states have clean energy mandates targeting 100% use of renewable energy.   These mandates provide incentives for farmers that make installing solar a financially smart decision and falling prices for solar installations make it an even better deal.

Solar works well when co-located on a farm and can be built in ways that minimizes impact.  It is quiet, uses almost no water, doesn’t pollute, and if it is decommissioned, the land can go back to its previous use.  If the solar facilities are raised up, the same land can be used to graze livestock or grow shade-tolerant crops.

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Harvesting the sun is the new cash crop

Photo, posted December 25, 2017, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Two Million Solar Installations

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Three years ago, we reported that the United States had installed its one millionth solar energy system, a feat that took 40 years to accomplish.  Recently, the Solar Energy Industries Association announced that there are now more than 2 million U.S. installations.

Analysts forecast that there will be 3 million installation in 2021 and 4 million in 2023.

California continues to lead the nation in installing solar power.  More than 50% of the first million installations were in that state and California accounted for 43% of the second million.  Its share is nevertheless slowly dropping with the growth of the residential solar sector that is rapidly diversifying across state markets.  Some places have seen extremely rapid growth.  In South Carolina, there were barely more than 1,000 cumulative installations in 2016; today, the state is home to more than 18,000 solar systems and expects to add 22,000 more over the next five years.

The five leading states in terms of number of solar installations are California, Arizona, New York, New Jersey, and Massachusetts.    Other states recently seeing rapid growth in solar installations are Texas, Utah, Florida, Rhode Island and Maryland.  Looking ahead, Illinois is forecast to grow from only 4,000 installations today to nearly 100,000 by 2024.  The top ten state markets apart from California expect to add nearly 750,000 installation over the next five years.

The United States is at least the third nation that is home to more than 2 million solar installations.  (Australia hit the milestone late least year and Japan actually topped 2 million in September 2014).

According to forecasts from analyst first Wood Mackenzie, by the year 2024, there will be on average one new solar installation every minute.

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The United States surpasses 2 million solar installations

Photo, posted January 11, 2012, courtesy of the Oregon Department of Transportation via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Rapid Antarctic Melting

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The Ross Ice Shelf in Antarctica is the world’s largest ice shelf, covering an area roughly the size of France.  Scientists have spent several years building up a record of how the northwest sector of the enormous ice shelf interacts with the ocean beneath it.  Their results show that the ice is melting much more rapidly than previously thought because of in-flowing warm water.

In general, the stability of ice shelves is thought to be mostly influenced by their exposure to warm deep ocean water.  But the new research has found that surface water heated by the sun also plays a crucial role in melting ice shelves.

The interactions between ice and ocean water that occur hundreds of meters below the surface of ice shelves have a direct impact on long-term sea level.  The Ross Ice Shelf stabilizes the West Antarctic ice sheet by blocking the ice that flows into it from some of the world’s largest glaciers.

When ice shelves collapse, the glaciers that feed them can speed up by a factor of two or three.  None of the collapsing shelves in the past have come anywhere close to the size of the Ross Ice Shelf, which is more than 100 times bigger.

The new study by New Zealand’s National Institute of Water and Atmospheric Research showed that sun-heated surface water flowing into the cavity under the ice shelf near Ross Islands caused melt rates to nearly triple during the summer months.  This indicates that the loss of sea ice resulting from climate change is likely to increase melt rates in the future.  While the Ross Ice Shelf is still considered to be relatively stable, the new findings show that it may be more vulnerable than previously thought.

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Rapid melting of the world’s largest ice shelf linked to solar heat in the ocean

Photo, posted February 15, 2009, courtesy of Alan Light via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A Giant Solar Farm In Dubai

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Like many places in the Middle East, Dubai made its fortune from oil.  But the Emirate’s oil resources are limited, and its economy has evolved in other directions.  Today, oil provides less than 5% of Dubai’s revenues; its economy relies on revenues from trade, tourism, aviation, real estate, and financial services.

Dubai is also away from fossil fuels to meet its energy needs. A monumental construction project is underway deep within Dubai’s desert interior which will be the largest solar energy facility in the world.

The Mohammed Bin Rashid Al Maktoum Solar Park – named after Dubai’s ruler – has been under development for 7 years.  Total investment in the project will be nearly $14 billion when it is completed in 2030.  It will have a total capacity of 5,000 megawatts, enough to power 1.3 million homes.  Only some large hydroelectric power plants, the largest nuclear power plants, and a couple of Asian coal plants have more generating capacity.

Phases one and two of the project are already complete and feature more than 2 million solar panels.  Phase three – well along the way in construction – will add another 3 million solar panels and should be completed next year.

Phase four will not involve solar panels but instead will make use of the world’s tallest concentrated solar power tower.  It will use mirrors to focus sunlight at the top of the tower to heat up molten salt that will power steam turbines to generate electricity and will be able to operate long after the sun goes down.

Currently, the Tengger Desert Solar Park in China is the largest photovoltaic park in the world, but a colossal farm in India will take its place in a few years.  Big solar is getting bigger all the time.

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$13.6B record-breaking solar park rises from Dubai desert

Photo, posted December 15, 2018, courtesy of Anoop S. via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

The World’s Largest Storage Battery

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Many homeowners are installing solar energy systems with battery backup.  Energy stored in the battery can be used when the sun isn’t shining.   As battery prices come down, utility-scale solar installations are also turning to battery-based energy storage.

Florida Power & Light has announced plans to build the world’s largest solar-storage combination facility in Manatee County.  The 409-MW Manatee Energy Storage Center will be the largest solar-battery system by a factor of four.  The specifics of the technology and source of the battery system components have yet to be announced.

The system, which is scheduled to be completed in late 2021, will be charged by a nearby FPL solar power plant.  The plan is to discharge batteries during times of higher demand, thereby offsetting the need to run other power plants.  As a result, there will be reduced emissions and customers will save as much as $100 million through avoided fuel costs.

Installing the mega-sized battery system will accelerate the retirements of two nearby 1970’s-era gas-fired generation units.  At peak efficiency, the Manatee energy storage system will be able to power 390,000 homes for up to two hours.

FPL has already been pursuing the use of battery storage technology.  Last year, they added a 10 MW battery storage system to its 74.5 MW Babcock Ranch Solar Energy Center in Charlotte County.

These large battery systems are increasingly practical because of dramatic reductions in lithium-ion battery costs.  The levelized cost of electricity from lithium-ion batteries has declined a remarkable 38% just since the beginning of 2018.  The economics of clean energy continue to get better and better.

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FP&L Plans World’s Largest Energy Storage Battery To Support Its Renewable Energy Goals

Photo, posted April 21, 2010, courtesy of Frank Starmer via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Trees And The Future Of Cities

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The shade of a single tree is a welcome source of relief on a hot summer day.  But even a relatively small patch of woods can have a profound cooling effect.  A new study at the University of Wisconsin-Madison looks at the role trees play in keeping towns and cities cool.

According to the study, the right amount of tree cover can lower daytime temperatures in the summer by as much as 10 degrees.  The effects are noticeable from neighborhood to neighborhood and even on a block-by-block basis.

Cities are well-known to be hot spots due to the urban heat islanding effect.  Using trees to keep temperatures more comfortable in cities can make a big difference for the people who live and work there.

The man-made structures of cities – roads, sidewalks, and buildings – absorb heat from the sun during the day and slowly release it at night.  Trees, on the other hand, not only shade those structures from the sun, but they also transpire -or release water in the air through their leaves – which helps to cool things down.

According to the study, to get maximum cooling benefits, tree canopies must exceed forty percent, meaning that city blocks need to be nearly halfway covered by tree branches and leaves.  To get the biggest bang for the buck, cities should start planting more trees in areas that are already near the forty percent threshold.  But

trees can’t just be in parks.  They need to be in places where people are active.

If we want the places where we live to be more comfortable and resilient in a warming world, we need to plant more trees.

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Study suggests trees are crucial to the future of our cities

Photo, posted May 26, 2012, courtesy of Mislav Marohnic via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Thoreau And Climate Change

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Henry David Thoreau was a 19th-century American naturalist, philosopher, poet, essayist, and social reformer.  He is best known for “Civil Disobedience,” an essay advocating for the rebellion against an unjust government, and for “Walden,” a book about his experiences living simply in nature.  Now, Thoreau’s observations from “Walden” are the foundation of a new study exploring the effects of climate change on tree leaf-out and the emergence of spring wildflowers. 

This research, which was recently published in the journal Ecology Letters, relies on Thoreau’s scientific observations gathered during the 1850s when he spent 26 months living in isolation at Walden Pond in Concord, Massachusetts.  These observations from Thoreau were combined with current research to measure tree and wildflower leaf-out dates for 37 different years between 1852 and 2018.  “Leaf out” refers to the time in spring when plants and trees begin producing leaves.  An alteration in this timing can have a domino effect throughout an ecosystem.

Over the past century, temperatures in Concord, Massachusetts have warmed five degrees Fahrenheit.  As a result, leaf-out dates have changed significantly.  According to researchers, wildflowers are leafing out about one week earlier, while trees are leafing out about two weeks earlier than they did 160 years ago. 

Ground-dwelling plants like wildflowers have a narrow window to accomplish growth, photosynthesis, and reproduction, before the canopy trees leaf out and block the sunlight.  Temperature-driven shifts in the timing of tree leaf-out between Thoreau’s time and now are likely already hindering wildflower abundance and flowering. 

As the climate continues to warm, the already small window of time between wildflower emergence and tree leaf-out will likely shorten further. 

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Using Thoreau, scientists measure the impact of climate change on wildflowers

Photo, posted August 13, 2008, courtesy of Adam Pieniazek via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Shrinking Arctic Glaciers

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The glaciers on Baffin Island, located in Canada’s northeastern Arctic, have been shrinking as the climate warms.  The melting, receding glaciers have exposed fragments of ancient plants that had frozen in the places where they once grew.  New research has shown that these spots have not seen the light of day for at least 40,000 years.

The entire planet has been warming since humanity started flooding the atmosphere with greenhouse gases at the start of the Industrial Revolution, but the effects are not uniform across the globe.  Some regions – like the Arctic – are seeing temperature rises that are greater and faster than anywhere else in the world.  As a result, glaciers in the Arctic have been melting away at rates never before observed in modern human history.

Researchers at the University of Colorado performed radiocarbon dating experiments in order to find out when the last time was that the Arctic was as warm as today.   There have been natural variations in Arctic temperatures caused by the complicated way the Earth wobbles on its axis.  For example, 10,000 years ago the northern latitudes pointed at the sun more directly during the summer than they do now, providing about 9% more sunshine during the summer.

The results of the study showed that the newly-uncovered plants had died at least 40,000 years earlier, indicating that the glaciers had not melted back to today’s size for at least that long.  Global measurements indicate that the planet as a whole has not been as warm as it is today for about 115,000 years, back then again a result of the orientation of the Earth.

Well, the Earth hasn’t wobbled recently.  The Arctic is melting because we are dumping massive amounts of greenhouse gases into the atmosphere.

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These Arctic glaciers are smaller than ever before in human history

Photo, posted September 1, 2010, courtesy of Doryce S. via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

More Renewables Without Storage In Texas

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Texas has a Texas-sized appetite for electricity and relies most heavily on natural gas, coal and nuclear power to get it.  But in recent times, wind power has grown tremendously in the Lone Star State and it has already leapfrogged past nuclear power.  Coal could be the next domino to fall.

In the past few years, solar power has become competitive with wind in terms of price.  Texas is a large, coastal state in the sunny southwestern U.S. and has significant solar resources.  As a result, the amount of solar power in Texas is now growing rapidly.

In order for a combination of solar and wind power to address the bulk of electricity demand in Texas, there needs to be a way to provide reliability that these intermittent sources don’t necessarily provide.  Energy storage is a solution that ultimately is likely to be part of most electricity grids, but currently it is still expensive on a utility scale.

A new study from Rice University looked at the complementarity of solar and wind power in Texas.  Complementarity refers to balancing the output of solar and wind systems.  The peak performance of wind and solar occurs at very different times in different regions of the state.  The study suggests that the right mix of solar and wind systems in the right parts of Texas could provide a continuously reliable energy system.  On both a yearly and daily basis, wind and solar power resources in Texas complement each other in terms of peak performance.  It is a matter of locating the solar power and wind farms in the right places.

With the Texas solar industry really starting to boom, there is a real opportunity to integrate far more renewable energy into the Texas grid.

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More Renewables with Less Energy Storage: Texas Shows How

Photo, posted June 8, 2018, courtesy of Laura Lee Dooley via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

WAMC Northeast Public Radio

WAMC/Northeast Public Radio is a regional public radio network serving parts of seven northeastern states (more...)