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Wind turbines and solar panels are an increasingly common sight. But why? What are the benefits of renewable energies-and how do they improve our health, environment, and economy?

This page explores the many positive impacts of clean energy, including the benefits of wind, solar, geothermal, hydroelectric, and biomass. For more information on their negative impacts-including effective solutions to avoid, minimize, or mitigate-see our page on The Environmental Impacts of Renewable Energy Technologies.

Less global warming

Human activity is overloading our atmosphere with carbon dioxide and other global warming emissions. These gases act like a blanket, trapping heat. The result is a web of significant and harmful impacts, from stronger, more frequent storms, to drought, sea level rise, and extinction.

In the United States, about 29 percent of global warming emissions come from our electricity sector. Most of those emissions come from fossil fuels like coal and natural gas [ 1, 2].

What is CO2e?

Carbon dioxide (CO2) is the most prevalent greenhouse gas, but other air pollutants-such as methane-also cause global warming. Different energy sources produce different amounts of these pollutants. To make comparisons easier, we use a carbon dioxide equivalent, or CO2e-the amount of carbon dioxide required to produce an equivalent amount of warming.

In contrast, most renewable energy sources produce little to no global warming emissions. Even when including "life cycle" emissions of clean energy (ie, the emissions from each stage of a technology's life-manufacturing, installation, operation, decommissioning), the global warming emissions associated with renewable energy are minimal [ 3].

The comparison becomes clear when you look at the numbers. Burning natural gas for electricity releases between 0.6 and 2 pounds of carbon dioxide equivalent per kilowatt-hour (CO2E/kWh); coal emits between 1.4 and 3.6 pounds of CO2E/kWh. Wind, on the other hand, is responsible for only 0.02 to 0.04 pounds of CO2E/kWh on a life-cycle basis; solar 0.07 to 0.2; geothermal 0.1 to 0.2; and hydroelectric between 0.1 and 0.5.

Renewable electricity generation from biomass can have a wide range of global warming emissions depending on the resource and whether or not it is sustainably sourced and harvested.

Increasing the supply of renewable energy would allow us to replace carbon-intensive energy sources and significantly reduce US global warming emissions.

For example, a 2009 UCS analysis found that a 25 percent by 2025 national renewable electricity standard would lower power plant CO2 emissions 277 million metric tons annually by 2025-the equivalent of the annual output from 70 typical (600 MW) new coal plants [ 4].

In addition, a ground-breaking study by the US Department of Energy's National Renewable Energy Laboratory (NREL) explored the feasibility of generating 80 percent of the country's electricity from renewable sources by 2050. They found that renewable energy could help reduce the electricity sector's emissions by approximately 81 percent [ 5].

Improved public health

The air and water pollution emitted by coal and natural gas plants is linked with breathing problems, neurological damage, heart attacks, cancer, premature death, and a host of other serious problems. The pollution affects everyone: one Harvard University study estimated the life cycle costs and public health effects of coal to be an estimated $74.6 billion every year. That's equivalent to 4.36 cents per kilowatt-hour of electricity produced-about one-third of the average electricity rate for a typical US home [ 6].

Most of these negative health impacts come from air and water pollution that clean energy technologies simply don't produce. Wind, solar, and hydroelectric systems generate electricity with no associated air pollution emissions. Geothermal and biomass systems emit some air pollutants, though total air emissions are generally much lower than those of coal- and natural gas-fired power plants.

In addition, wind and solar energy require essentially no water to operate and thus do not pollute water resources or strain supplies by competing with agriculture, drinking water, or other important water needs. In contrast, fossil fuels can have a significant impact on water resources: both coal mining and natural gas drilling can pollute sources of drinking water, and all thermal power plants, including those powered by coal, gas, and oil, withdraw and consume water for cooling.

Biomass and geothermal power plants, like coal- and natural gas-fired power plants, may require water for cooling. Hydroelectric power plants can disrupt river ecosystems both upstream and downstream from the dam. However, NREL's 80-percent-by-2050 renewable energy study, which included biomass and geothermal, found that total water consumption and withdrawal would decrease significantly in a future with high renewables [ 7].

Inexhaustible energy

Strong winds, sunny skies, abundant plant matter, heat from the earth, and fast-moving water can each provide a vast and constantly replenished supply of energy. A relatively small fraction of US electricity currently comes from these sources, but that could change: studies have repeatedly shown that renewable energy can provide a significant share of future electricity needs, even after accounting for potential constraints [ 9].

In fact, a major government-sponsored study found that clean energy could contribute somewhere between three and 80 times its 2013 levels, depending on assumptions [8]. And the previously mentioned NREL study found that renewable energy could comfortably provide up to 80 percent of US electricity by 2050.

Jobs and other economic benefits

Compared with fossil fuel technologies, which are typically mechanized and capital intensive, the renewable energy industry is more labor intensive. Solar panels need humans to install them; wind farms need technicians for maintenance.

This means that, on average, more jobs are created for each unit of electricity generated from renewable sources than from fossil fuels.

Renewable energy already supports thousands of jobs in the United States. In 2016, the wind energy industry directly employed over 100,000 full-time-equivalent employees in a variety of capacities, including manufacturing, project development, construction and turbine installation, operations and maintenance, transportation and logistics, and financial, legal, and consulting services [ 10]. More than 500 factories in the United States manufacture parts for wind turbines, and wind power project installations in 2016 alone represented $13.0 billion in investments [ 11].

Other renewable energy technologies employ even more workers. In 2016, the solar industry employed more than 260,000 people, including jobs in solar installation, manufacturing, and sales, a 25% increase over 2015 [ 12]. The hydroelectric power industry employed approximately 66,000 people in 2017 [ 13]; the geothermal industry employed 5,800 people [ 14].

Increased support for renewable energy could create even more jobs. The 2009 Union of Concerned Scientists study of a 25-percent-by-2025 renewable energy standard found that such a policy would create more than three times as many jobs (more than 200,000) as producing an equivalent amount of electricity from fossil fuels [ 15].

In contrast, the entire coal industry employed 160,000 people in 2016 [ 26].

In addition to the jobs directly created in the renewable energy industry, growth in clean energy can create positive economic "ripple" effects. For example, industries in the renewable energy supply chain will benefit, and unrelated local businesses will benefit from increased household and business incomes [ 16].
Listen to energy expert Paula Garcia talk about renewable energy progress in the US on the Got Science? Podcast:
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Local governments also benefit from clean energy, most often in the form of property and income taxes and other payments from renewable energy project owners. Owners of the land on which wind projects are built often receive lease payments ranging from $3,000 to $6,000 per megawatt of installed capacity, as well as payments for power line easements and road rights-of-way. They may also earn royalties based on the project's annual revenues. Farmers and rural landowners can generate new sources of supplemental income by producing feedstocks for biomass power facilities.

UCS analysis found that a 25-by-2025 national renewable electricity standard would stimulate $263.4 billion in new capital investment for renewable energy technologies, $13.5 billion in new landowner income from? biomass production and/or wind land lease payments, and $11.5 billion in new property tax revenue for local communities [ 17].

Stable energy prices

Renewable energy is providing affordable electricity across the country right now, and can help stabilize energy prices in the future.

Although renewable facilities require upfront investments to build, they can then operate at very low cost (for most clean energy technologies, the "fuel" is free). As a result, renewable energy prices can be very stable over time.

Moreover, the costs of renewable energy technologies have declined steadily, and are projected to drop even more. For example, the average price to install solar dropped more than 70 percent between 2010 and 2017 [ 20]. The cost of generating electricity from wind dropped 66 percent between 2009 and 2016 [ 21]. Costs will likely decline even further as markets mature and companies increasingly take advantage of economies of scale.

In contrast, fossil fuel prices can vary dramatically and are prone to substantial price swings. For example, there was a rapid increase in US coal prices due to rising global demand before 2008, then a rapid fall after 2008 when global demands declined [ 23]. Likewise, natural gas prices have fluctuated greatly since 2000 [ 25].

Using more renewable energy can lower the prices of and demand for natural gas and coal by increasing competition and diversifying our energy supplies. And an increased reliance on renewable energy can help protect consumers when fossil fuel prices spike.

Reliability and resilience

Wind and solar are less prone to large-scale failure because they are distributed and modular. Distributed systems are spread out over a large geographical area, so a severe weather event in one location will not cut off power to an entire region. Modular systems are composed of numerous individual wind turbines or solar arrays. Even if some of the equipment in the system is damaged, the rest can typically continue to operate.

For example, Hurricane Sandy damaged fossil fuel-dominated electric generation and distribution systems in New York and New Jersey and left millions of people without power. In contrast, renewable energy projects in the Northeast weathered Hurricane Sandy with minimal damage or disruption [ 25].

Water scarcity is another risk for non-renewable power plants. Coal, nuclear, and many natural gas plants depend on having sufficient water for cooling, which means that severe droughts and heat waves can put electricity generation at risk. Wind and solar photovoltaic systems do not require water to generate electricity and can operate reliably in conditions that may otherwise require closing a fossil fuel-powered plant. (For more information, see How it Works: Water for Electricity.)

The risk of disruptive events will also increase in the future as droughts, heat waves, more intense storms, and increasingly severe wildfires become more frequent due to global warming-increasing the need for resilient, clean technologies.
Learn more: References:
[1] Environmental Protection Agency. 2017. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2015.

[2] Energy Information Agency (EIA). 2017. How much of the U.S. carbon dioxide emissions are associated with electricity generation?

[3] Intergovernmental Panel on Climate Change (IPCC). 2011. IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation. Prepared by Working Group III of the Intergovernmental Panel on Climate Change [O. Edenhofer, R. Pichs-Madruga, Y. Sokona, K. Seyboth, P. Matschoss, S. Kadner, T. Zwickel, P. Eickemeier, G. Hansen, S. Schlömer, C. von Stechow (eds)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1075 pp. (Chapter 9).

[4] Union of Concerned Scientists (UCS). 2009. Clean Power Green Jobs.

[5] National Renewable Energy Laboratory (NREL). 2012. Renewable Electricity Futures Study. Volume 1, pg. 210.

[6] Epstein, P.R.,J. J. Buonocore, K. Eckerle, M. Hendryx, B. M. Stout III, R. Heinberg, R. W. Clapp, B. May, N. L. Reinhart, M. M. Ahern, S. K. Doshi, and L. Glustrom. 2011. Full cost accounting for the life cycle of coal in "Ecological Economics Reviews." Ann. N.Y. Acad. Sci. 1219: 73-98.

[7] Renewable Electricity Futures Study. 2012.

[8] NREL. 2016. Estimating Renewable Energy Economic Potential in the United States: Methodology and Initial Results.

[9] Renewable Electricity Futures Study. 2012.

IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation. Prepared by Working Group III of the Intergovernmental Panel on Climate Change. 2011.

UCS. 2009. Climate 2030: A national blueprint for a clean energy economy.

[10] American Wind Energy Association (AWEA). 2017. AWEA U.S. Wind Industry Annual Market Report: Year Ending 2016. Washington, D.C.: American Wind Energy Association.

[11] Wiser, Ryan, and Mark Bolinger. 2017. 2016 Wind Technologies Market Report. U.S. Department of Energy.

[12] The Solar Foundation. 2017. National Solar Jobs Census 2016.

[13] Navigant Consulting. 2009. Job Creation Opportunities in Hydropower.

[14] Geothermal Energy Association. 2010. Green Jobs through Geothermal Energy.

[15] UCS. 2009. Clean Power Green Jobs.

[16] Environmental Protection Agency. 2010. Assessing the Multiple Benefits of Clean Energy: A Resource for States. Chapter 5.

[17] UCS. 2009. Clean Power Green Jobs.

[18] Deyette, J., and B. Freese. 2010. Burning coal, burning cash: Ranking the states that import the most coal. Cambridge, MA: Union of Concerned Scientists.

[20] SEIA. 2017. Solar Market Insight Report 2017 Q2.

[21] AWEA. 2017. AWEA U.S. Wind Industry Annual Market Report: Year Ending 2016. Washington, D.C.: American Wind Energy Association.

[22] UCS. 2009. Clean Power Green Jobs.

[23] UCS. 2011. A Risky Proposition: The financial hazards of new investments in coal plants.

[24] EIA. 2013. U.S. Natural Gas Wellhead Price.

[25] Unger, David J. 2012. Are renewables stormproof? Hurricane Sandy tests solar, wind. The Christian Science Monitor. November 19.

[26] Department of Energy. 2017 U.S. Energy and Employment Report

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Wind turbines and solar panels are an increasingly common sight. But why? What are the benefits of renewable energies-and how do they improve our health, environment, and economy? This page explores the many positive impacts of clean energy, including the benefits of wind, solar, geothermal, hydroelectric, and biomass.

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How physical activity affects academic performance

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How physical activity affects academic performance

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Phospholipid bilayers? Pythagorean Theorem? The Lusitania? Kennedy Who?

And so it goes. Students in every grade level at schools across the country are struggling in class. It's not because they're underachievers, or they're not smart, or they don't care. It's because we're working against them. The longer children and teens are forced to sit and grow roots in their chairs, the harder it will be for them to bloom.

There is myriad research that proves that students need adequate amounts of physical activity throughout the school day-not only do they prevent obesity and obesity-related issues, but they perform better academically also.

Just ask the CDC, Columbia University, the New York City Health Department and Department of Education, the Universities of Illinois, West Virginia, and California.

They've all published research that stands behind the need for physical education in the school system.

The CDC states, "...physical activity can have an impact on cognitive skills and attitudes and academic behavior, all of which are important components of improved academic performance. These include enhanced concentration and attention as well as improved classroom behavior."

And there's more. Active Living Research says, "In some cases, more time in physical education leads to improved grades and standardized test scores." In schools that are under government mandates to bridge the achievement gap (and when those mandates encourage "teaching to the test"), physical education can actually help improve the students' scores.

Unfortunately, many schools cut physical education and PE funding with the belief that more rigid classroom time would somehow stimulate students to learn more. It's an incorrect belief, and there's scientific evidence to prove it.

Exercise directly impacts the behavior and development of the brain. "It is likely that the effects of physical activity on cognition would be particularly important in the highly plastic developing brains of youth," according to a 2010 essay penned by Charles Basch of Columbia University.

He summarized how exercise may affect executive functioning:

Increased oxygen flow to the brain

Increased brain neurotransmitters

"[Increased] brain-derived neurotrophins that support neuronal differentiation and survival in the developing brain." Neurotrophins assure the survival of neurons in areas responsible for learning, memory, and higher thinking.

Physical activity has benefits beyond improved grades, too. Basch extrapolates current research and connects physical activity to absenteeism, drop-out rates, and social connectedness.

"Drop-out rates were lower for youth who consistently participated in interscholastic sports," he writes, though he cautions that forcing kids to join sports won't solve the drop-out problem that plagues many inner city schools, it simply may foster an environment of connectedness that could keep at-risk students attending school.

That's the core of it all; that's why we're here. We want our students to get a quality education, even though their life situation or choices often make it difficult. But every child, regardless of financial background, should have equal access to excellent education.

It's not good enough to push them through the school system and let them fend for themselves in the real world. We must use their formative years to give them the tools they can use to survive and provide for their own families. When they have children, they'll be able to pass on knowledge we gave them. We're creating a positive future for generations to come.

So what can school districts do to inject more activity and movement into the school day?

First, administrators must let go of the dated idea that PE must take a backseat.

"There is currently no evidence indicating that this strategy is, in fact, effective in increasing standardized test scores," according to the Columbia University essay. "In fact, a growing body of evidence shows that increased time for physical education and other school-based physical activity programs is associated with either a neutral or positive impact on academic outcomes."

By the way, Columbia University is ranked among the leaders in the top-tier of best research universities in the U.S.

The evidence is clear. Physical activity should have a place in the curriculum of every school that's serious about teaching its kids.

The National Association for Sport and Physical Education recommends 60 minutes a day for children and adolescents. Schools should provide 150 minutes per week of instructional physical education for elementary school children, and 225 minutes per week for middle and high school students throughout the school year.

Adequate PE curriculum can help children achieve these numbers, in turn creating healthy bodies and eager-to-learn minds. Adequate physical education doesn't stop there; it sets children up for a healthy adulthood, perpetuating a cycle of well-being for generations to come.

What's the missing link between reducing obesity and increasing America's ability to compete in a tough global economy? Physical education.
Want to learn more about the link between Academics and Physical Activity? Click Here to access a collection of Articles/Publications/Webinars on the subject.

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How Physical Activity Affects Academic Performance

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Phospholipid bilayers? Pythagorean Theorem? The Lusitania? Kennedy Who? And so it goes. Students in every grade level at schools across the country are struggling in class. It's not because they're underachievers, or they're not smart, or they don't care. It's because we're working against them.

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What research says about the value of homework

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What research says about the value of homework

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Whether homework helps students-and how much homework is appropriate-has been debated for many years. Homework has been in the headlines again recently and continues to be a topic of controversy, with claims that students and families are suffering under the burden of huge amounts of homework. School board members, educators, and parents may wish to turn to the research for answers to their questions about the benefits and drawbacks of homework. Unfortunately, the research has produced mixed results so far, and more research is needed. Nonetheless, there are some findings that can help to inform decisions about homework. What follows is a summary of the research to date:

The link between homework and student achievement is far from clear. There is no conclusive evidence that homework increases student achievement across the board. Some studies show positive effects of homework under certain conditions and for certain students, some show no effects, and some suggest negative effects (Kohn 2006; Trautwein and Koller 2003).

Homework appears to have more positive effects for certain groups of students:

Older students benefit more from homework than younger students. Some studies have shown that older students gain more academic benefits from homework than do younger students, perhaps because younger students have less-effective study habits and are more easily distracted (Cooper 1989; Hoover-Dempsey et al. 2001; Leone and Richards 1989; Muhlenbruck et al. 2000).

Students from low-income homes may not benefit as much from homework as those from higher-income homes. Some researchers believe that students from higher-income homes have more resources (such as computers) and receive more assistance with homework, while low-income students may have fewer resources and less assistance and are therefore less likely to complete the homework and reap any related benefits (McDermott, Goldmen and Varenne 1984; Scott-Jones 1984).

Students with learning disabilities benefit from homework under certain conditions. Students with learning disabilities can benefit from homework if appropriate supervision and monitoring are provided (Cooper and Nye 1994; Rosenberg 1989).

Asian American students may benefit more from homework than do students from other ethnic groups. A national study of the influence of homework on student grades across five ethnic groups found that homework had a stronger impact on Asian American students than on students of other ethnicities (Keith and Benson, 1992).

Homework may have nonacademic benefits. Certain nonacademic benefits of homework have been shown, especially for younger students. Indeed, some primary-level teachers may assign homework for such benefits, which include learning the importance of responsibility, managing time, developing study habits, and staying with a task until it is completed (Cooper, Robinson and Patall 2006; Corno and Xu 2004; Johnson and Pontius 1989; Warton 2001).

Too much homework may diminish its effectiveness. While research on the optimum amount of time students should spend on homework is limited, there are indications that for high school students, 1½ to 2½ hours per night is optimum. Middle school students appear to benefit from smaller amounts (less than 1 hour per night). When students spend more time than this on homework, the positive relationship with student achievement diminishes (Cooper, Robinson, and Patall 2006).

The amount of homework completed by students seems to be more positively associated with student achievement than the amount of homework assigned by teachers. Some research has shown that students who spend more time on homework score higher on measures of achievement and attitude. Studies that have delved more deeply into this topic suggest, however, that the amount of homework assigned by teachers is unrelated to student achievement, while the amount of homework actually completed by students is associated with higher achievement (Cooper 2001; Cooper, Lindsay, Nye, and Greathouse 1998).

After-school programs that provide homework assistance may improve student behavior, motivation, and work habits but not necessarily academic achievement. Studies of after-school programs that provide homework assistance have found few definite links to improved student achievement. Several studies, however, noted improvements in student motivation and work habits, which may indirectly affect achievement (Cosden, Morrison, Albanese, and Macias 2001; James-Burdumy et al. 2005).

The effect of parent involvement in homework is unclear. Studies of parent involvement in homework have produced mixed results. Homework assignments that require interaction between students and parents result in higher levels of parent involvement and are more likely to be turned in than noninteractive assignments. Some studies have shown, however, that parent involvement in homework has no impact on student achievement. Other studies indicate that students whose parents are more involved in their homework have lower test scores and class grades-but this may be because the students were already lower performing and needed more help from their parents than did higher-performing students. (Balli, Wedman, and Demo 1997; Cooper, Lindsay, and Nye 2000; Epstein 1988; Van Voorhis 2003).

There is little research on connections between specific kinds of homework and student achievement. Most teachers assign homework to reinforce what was presented in class or to prepare students for new material. Less commonly, homework is assigned to extend student learning to different contexts or to integrate learning by applying multiple skills around a project. Little research exists on the effects of these different kinds of homework on student achievement, leaving policymakers with little evidence on which to base decisions (Cooper 1989; Foyle 1985; Murphy and Decker 1989).

The homework review was produced by researchers at Edvantia for the Center for Public Education. Edvantia, formerly the Appalachia Educational Laboratory, is an education research and development not-for-profit corporation founded in 1966. Posted: February 5, 2007

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What research says about the value of homework: At a glance

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Whether homework helps students-and how much homework is appropriate-has been debated for many years. Homework has been in the headlines again recently and continues to be a topic of controversy, with claims that students and families are suffering under the burden of huge amounts of homework.