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Solar On Commercial Buildings | Earth Wise

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The United States installed 3.6 gigawatts of photovoltaic solar capacity in the first quarter of this year to reach a total installed capacity of 81.4 GW.  That is enough to power about 16 million American homes.  More than 2/3 of that capacity has been installed during the past five years.  

There has been a boom in solar installations in recent years and, until the Covid-19 pandemic stuck, 2020 was expected to be the biggest year yet.  Now the unprecedented health, social, and economic conditions in our country creates great uncertainty in such forecasts.

Nevertheless, the opportunities for growth in solar power continue to be substantial.  A new report from the energy research firm Wood Mackenzie looked at the prospects for using the roof space of commercial buildings for solar power.

Currently, just 3.5% of commercial buildings in the U.S. have solar panels on their roofs.  Another 1% of those buildings are attached to solar projects located off-site.  The report looked at how many buildings are potential targets for solar projects.

After accounting for buildings that are too small or that use too little electricity to make solar power a worthwhile investment, the report estimated that 70% of commercial buildings in the U.S. – amounting to some 600,000 sites – are candidates for solar installations.  Doing this would provide 145 GW of new solar capacity, which is nearly twice as much as currently exists in this country. 

Commercial solar installations have their own unique logistical and financial challenges.  While utility solar can scale to lower costs and residential solar has financing opportunities, commercial solar has neither.  But ultimately, it represents an important opportunity for our future energy system.

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U.S. Commercial Rooftops Hold 145 Gigawatts of Untapped Solar Potential

Photo, posted June 25, 2014, courtesy of Rob Baxter via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Roofs Going Green

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Green roofs are roofs on buildings that are partially or completely covered with vegetation and a growing medium, generally planted over a waterproofing membrane.  The modern version of these roofs began in Germany in the 1960s and spread to many other European countries over time.  With concerns about climate change and shrinking natural resources rising, green roofs are becoming increasingly popular across North America.  The Toronto-based organization Green Roofs for Healthy Cities estimates that the number in North America has increased by about 15% since 2013.

Replacing black asphalt and shingles with plants can lower the surrounding air temperature, filter dirty storm water, and reduce building energy use.  The National Research Council of Canada estimates that a green roof can reduce air conditioning use in a building by as much as 75%.  The roofs also help to reduce air pollution and greenhouse gas emissions according to the EPA.

As the benefits of green roofs become more widely known, cities around the world are passing green roof legislation.  Copenhagen passed a law in 2010 requiring all new commercial buildings to have green roofs if their roofs are not sloped too much.  Toronto was the first city in North America to pass a green roof law in 2009.  Over 640 green roofs covering more than five million square feet have since been constructed in Toronto.

Apart from the environmental benefits, green roofs are providing pleasant spaces in the urban environment that may include flower beds, trees, herb gardens, gazebos and picnic tables.  As for the economics, studies show that over the course of a roof’s lifetime, green roofs are actually considerably cheaper than conventional roofs taking into account energy savings.

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The Green Revolution Spreading Across Our Rooftops

Photo, posted July 15, 2014, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Capital Region Community Solar

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New York’s Capital Region is getting a major new community solar farm.  A community solar farm is a solar power installation whose output is shared by multiple community subscribers who receive credit on their electricity bills for their share of the power produced.  The primary purpose of community solar is to allow members of a community to have the benefits of solar power even if they cannot or prefer not to install solar panels on their own property.

US Light Energy has broken ground on the Sugar Hill Solar Farm, to be located on 40 acres of land on the Sugar-Hill/Sugar-View Farm in Clifton Park.  The 7-megawatt, ground-mounted solar project will include nearly 20,000 solar modules.  When fully operational later this year, the facility is expected to produce more than 8.6 million kilowatt-hours of energy a year.

The farm will be part of New York state’s Community Solar Program, and the electricity it generates can be supplied to customers anywhere in National Grid’s existing distribution system.  Residential and commercial properties in Clifton Park will have 30 days to subscribe before the solar energy generated by the farm is opened to the general public.  Subscribers of community solar farms typically save 10% on their electricity bills.

There are already community solar programs in operation in several Capital Region communities, but this is the first one in the Clifton Park Area.  Apart from providing savings on utility bills, community solar allows consumers to support clean, locally generated power with little or no upfront costs.  Not everyone is in a position to put solar panels on their roof, but community solar is increasingly an option for New York residents.

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Construction begins on 7-MW community solar farm in New York

Photo, posted March 19, 2012, courtesy of Kate Ausburn via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Schools And Solar Power

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A new study from Stanford University looked at the benefits of installing solar panels on the rooftops of schools.  According to the study, taking advantage of all the viable space for solar panels could allow schools to meet up to 75% of their electricity needs and reduce the education sector’s carbon footprint by as much as 28%.

Given the long list of spending priorities for schools, solar power seems like a luxury item.  But the Department of Energy estimates that K-12 schools spend more than $6 billion a year on energy and, in many districts, energy costs are second only to salaries.  In the higher education sector, yearly energy costs add up to more than $14 billion.  In total, educational institutions account for approximately 11% of energy consumption by U.S. buildings and 4% of the nation’s carbon emissions.

The Stanford study suggests that investments in the right solar projects combined with the right incentives from states could free up much-needed money in school budgets.

To no surprise, the study finds that three large, sunny states – Texas, California, and Florida – have the greatest potential for generating electricity from solar panels on school rooftops.

Apart from measurable effects on air pollution and electricity bills, solar installations at schools can also provide new learning opportunities for students.  In fact, some schools are already using data from their on-site solar energy systems to teach students basic ideas about fractions, as an example, as well as more sophisticated concepts such how shifting solar panel angles can affect power production.

According to the study, nearly all states could reap value from school solar projects.

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What happens when schools go solar?

Photo, posted February 28, 2011, courtesy of Black Rock Solar via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Solar Equity for Low-Income Communities

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A couple of years ago, the number of American roofs covered with solar panels passed the one million mark and the numbers keep growing.  But nearly half of U.S. households – accounting for more than 154 million people – aren’t able to host their own solar arrays because they lack suitable rooftop space, or they rent their homes.  But millions more simply can’t afford to spend tens of thousands of dollars to buy or lease solar panels.

In recent years, community solar has become popular.  These are projects where multiple participants own or lease shares in a mid-sized solar facility and receive credits that lower their monthly utility bills.  Community solar in the U.S. has more than quadrupled just since 2016.

However, the majority of community solar subscribers to date have been businesses, universities, government agencies, and higher-earning households.  These users can generally pay steep project enrollment fees or meet various financial requirements.  Meanwhile, those who could benefit most from access to renewable energy and lower utility bills – low-income residents – have largely been left out.

Low-income households on average spend over 8% of their income on utility bills, about three times more than moderate- to high-income households.  So, reducing electricity bills with community solar power is a big deal for them.

Given this situation, there are now a growing number of programs that make use of community solar to reduce living expenses for low-income households.  In a dozen states, new programs include a variety of mandates, financial incentives, and pilot programs targeting benefits for people with low incomes.  These programs will allow them to participate in both the environmental and economic benefits of renewable energy.

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Energy Equity: Bringing Solar Power to Low-Income Communities

Photo, posted November 27, 2012, courtesy of Oregon State University via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Another Way To Make Solar Cells

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Millions of rooftops now contain solar panels and the majority of the solar cells that make up those panels today are made from silicon.  Silicon solar cells require expensive, multi-step processing conducted at very high temperatures in special clean room facilities.  Despite these complications, the price of solar panels has continued to drop dramatically over the years.

But even as the price of solar cells gets lower and lower, there are still widespread efforts to find even better ways to make them.   One of those ways is with perovskite solar cells.  Perovskites are materials with a characteristic crystal structure and are quite common in nature.  Perovskites can be formed with a wide range of elements and can exhibit a variety of properties.

They were first used to make solar cells about 10 years ago and those first cells were unimpressive in most respects.  However, there has been steady progress since that time.  The potential advantages of perovskite solar cells are that they can be made from low-cost materials and can be manufactured using liquid chemistry, a far cheaper process than what is used to make silicon cells.

Researchers at MIT and several other institutions have recently published the results of research on how to tailor the composition of perovskite solar cells to optimize their properties.   What used to be a trial-and-error process can now become much more engineered and should lead to perovskite solar cells with performance that could exceed that of silicon cells.

Silicon solar panels are a huge, worldwide industry and displacing them in favor of an alternative technology is a tall order.  But if perovskite cells can be optimized for large-scale manufacturability, efficiency and durability, they could definitely give silicon a run for its money.

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Unleashing perovskites’ potential for solar cells

Photo courtesy of Ken Richardson/MIT.

Earth Wise is a production of WAMC Northeast Public Radio.

Cleaning Up Storm Water

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Storm water reclamation is an important activity for cities with limited water resources, such as those in Southern California.   Many places have small-scale reclamation efforts using rain gardens and bioswales.  Collecting storm water on a large scale faces a number of problems.

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Making Cities Cooler

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Cities are particularly miserable during heatwaves.   With lots of concrete and asphalt surfaces, they soak up lots of heat and re-radiate it.  Lots of tall buildings block cooling breezes.  Factor in car exhaust and heat from air conditioners and it all adds up to the urban heat island effect.  Cities can be several degrees warmer during the day and as much as 20 degrees warmer at night.  All of this extra heat is not just a comfort issue, it is a serious health problem.

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Cooling Cities With White Roofs

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The phenomenon of urban heat islands has been well known since the 19th century.  The materials from which city buildings and roads are made reflect much less solar radiation and absorb more of it than the vegetation they have replaced.  The absorbed energy is then radiated in the form of heat into the surrounding air making cities warmer.

[Read more…] about Cooling Cities With White Roofs

Spray-On Solar Cells

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One of the most exciting possibilities for future solar energy technology is that of solar cells that can be sprayed or printed on to surfaces like the windows of skyscrapers, the roofs of sports utility vehicles, or the walls of houses.  And the expectation is that such technology would be far cheaper than today’s silicon-based solar panels.

[Read more…] about Spray-On Solar Cells

One Million Roofs

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Sometime early in May, the United States installed its one millionth solar energy system.  Achieving this milestone took the solar industry about 40 years to accomplish.  Because of the phenomenal growth of solar power in this country, industry experts predict that it will only take two more years to reach the second million and there are predictions that by the year 2025, there will be one million new installations in the U.S. each year.

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Mandatory Solar In San Francisco

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California leads the nation in the use of solar energy with well over half the country’s solar electric capacity. The state is the home of several of the largest thermal solar generating plants in the world and between those and multiple utility-scale photovoltaic plants, California utilities get more than 5% of their power from the sun.

[Read more…] about Mandatory Solar In San Francisco

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