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The world has been relying on oil, coal, and natural gas as the main sources of electricity for over 150 years. We prepared an easy guide with everything kids need to know about fossil fuels, from what types there are to their detrimental effects on our planet. -
Fossil fuels are used to produce the electricity we need to run most machines of modern life. From heating our homes to fueling cars, about 80% of the world's energy currently comes from fossil fuels. These energy sources are not renewable, meaning that once we use them up, they are gone forever.

Like fossils, they are the remains of organisms like plants, animals, and other living things that lived millions of years ago. Once dead, these organisms sank into the ground and were slowly covered by many layers of rock. Over the centuries, their remains changed in form, turning into different kinds of fossil fuels as we know them today. In order to release the energy stored inside them, fossil fuels are mined and burned.

3 Types of Fossil Fuels
1. Oil
Oil comes from microscopic organisms such as algae. It is often reached in places under the oceans using drills and oil rigs and it makes its way up to the surface through pipes. Oil is used to make gasoline for vehicles and heating systems and it is also used to manufacture common products such as paints and a lot of cosmetics, from lip balms to eyeliners!

Extracting oil from the ground and transporting it poses major environmental threats. are a recurring event. When oil is dispersed in the environment, it pollutes oceans, wetlands, freshwater sources, and other ecosystems and often puts even human health at risk.
Check This Out Next: 2. Coal How Do Oil Spills Affect the Environment?
Coal was formed from layers of dead plants over the course of millions of years. After being extracted from the earth, coal is burned at power stations to generate electricity and it is also used to produce plastics, fertilisers, and some medicines.
3. Natural Gas
Coal mining is an extremely harmful process as it disturbs the land and affects biodiversity. The burning process generates a variety of air pollutants that harm humans and the environment. Moreover, the ash that is created through coal combustion is extremely toxic and, when dispersed in the atmosphere, it pollutes waterways.

Similar to oil, natural gas also comes from microscopic organisms such as algae. It is a mixture of different gases - the main one being methane - that formed beneath the Earth's surface over millions of years and it is mainly used to heat buildings and water, provide outdoor lighting, dry clothes and cook. Natural gas is extracted from underground through a process called hydraulic fracturing, or fracking .

Despite leading to fewer emissions than coal, the process of generating electricity from natural gas is still responsible for the release of a lot of toxic gases into the atmosphere. One of them is methane, which is 25 times as potent as carbon dioxide at trapping heat in the atmosphere.

Why Are Fossil Fuels So Bad for the Environment?

As countries burn fossil fuels to generate electricity, they release immense quantities of greenhouse gases such as carbon dioxide and methane. These stay in the atmosphere, trapping heat from the sun and leading to global warming .

According to scientists, the earth's average surface temperature has increased by 1C (1.8F) in the last 150 years, with over half of the rise occurring since the mid-1970s. Although this doesn't sound like a lot, this seemingly small increase in the average global temperature has a huge impact on weather patterns and wildlife around the world!

Do We Have Alternatives?

Absolutely! Fossil fuels are not the only way we have to generate electricity. Cleaner technologies such as renewable energy can support a more sustainable energy system without emissions. The world is finally investing in these infinite sources of energy and today, of the global electricity is generated from renewables such as solar, wind, hydroelectric, and geothermal power.

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Fossil Fuels Explained to Kids - Earth.Org Kids

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We prepared an easy guide with everything kids need to know about fossil fuels, from what types there are to their detrimental effects on our planet.

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What types of energy are available, and how do we choose the best one for our future? This question will guide our exploration and discussion today.

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Students will independently research one type of energy, focusing on its feasibility for future use, and prepare a short presentation.

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When you think of energy, what do you think of - the Sun, gasoline or maybe electricity? All of these are forms of energy, but there are other kinds of energy too. Energy is all around you. It is the force that allows things to move and happen.

Even when you're asleep or just reading a book, your body uses energy to make your heart beat, your blood flow and your muscles move.

Energy can be changed from one form to another. Coal can be burned to make heat or electricity. Natural gas and wood also make heat when they burn. Think about plants. The Sun gives them energy to grow. We eat them and they give us energy.

Fun Facts about Energy for Kids

Coal, oil and gas are stored in the ground. Coal and oil come from the remains of fossilized animals.

Food gives you energy. Some foods give more energy than others. Snack foods like cookies, donuts or even white bread, turn quickly to energy. Your body burns through these foods very fast. Whole-grain foods like whole-wheat bread and foods with protein like yogurt or turkey make energy that lasts longer.

Gas, oil and coal will eventually run out. Scientists are working hard to find other kinds of energies. These are called alternative fuels.

In our country, we have plenty of energy. Sometimes we use more than our fair share. Other people in the world don't have the energy they need. Tell your parents to help conserve and share energy. Don't drive a bigger car than you need. Don't buy a bigger house than you need.

In windy areas, scientists build huge windmills. These windmills can harness the energy of wind to make electricity.

Waterfalls can also be used to make power.

The Sun makes solar energy.

Energy Vocabulary

Learn More All About Energy and Its Different Forms

Watch this video all about energy and its form:

A video explaining the forms of energy.

Energy Q&A

Question: Are there any problems with energy?

Answer: Some kinds of energy like coal and gasoline cause pollution as they burn. When we use too much of these kinds of energy, the temperature of our planet rises. This is called the greenhouse effect.

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Question: What can I do to help?

Answer: Right now, you can use energy carefully. Turn off the lights when you leave a room. Ride your bike or walk to your friend's house or soccer practice instead of asking your mom to drive you.

Enjoyed the Easy Science for Kids Website all about Energy info? Take the FREE & fun all about Energy quiz and download FREE Energy worksheet for kids. For lengthy info click here.

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Facts About Energy for Kids - Easy Science

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When you think of energy, what do you think of - the Sun, gasoline or maybe electricity? All of these are forms of energy, but there are other kinds of energy too. Energy is all around you. It is the force that allows things to move and happen.

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All the machines of modern life require energy to make them run. About 90 percent of that energy comes from burning fossil fuels. Fossil fuels include petroleum (oil), coal,...

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The amount of future renewable energy sources is expected to expand 50% between 2019 and 2024, led by solar power! A report by The International Energy Agency found that solar, wind and hydro power projects are being developed at their fastest rate in four years. - Renewable Energy: How Will it Grow?
Today, 26% of the world's electricity is generated from renewable energy sources! The IEA predicts that it will reach 30% by 2024. This rise in renewable energy follows a global coal slowdown last year as technology costs have dropped and there are growing concerns for the environment. It is predicted that the world's solar energy capacity will also grow by 600 GW, which is double the installed total electricity capacity of Japan.
Solar Becomes Cheaper
Experts predict that the US will their solar installations to four million by 2023. In 2018, the UK had over one million solar panel installations, which is a 2% increase from the year before and Australia also reached two million solar installations in the same year!

This increase is largely because of the fall in prices to install the panels. In 2018, the cost of solar PV-based power declined by 13% and Carbon Tracker predicts that 72% of coal-based power will become globally unprofitable. As renewable energy is becoming more accessible, solar energy will likely account for 60% of the growth in renewable energy use. The cost of solar power is expected to further decrease by 15-35% by 2024.

Solar power is more reliable and accessible compared to wind and hydropower as the sun rises and sets on a predictable schedule and does not require users to live in specific locations. Governments are now looking to incorporate more solar power to generate their electricity. California has said that solar panels must be installed on new homes and buildings of up to three storeys after 2020, while China is expected to register the largest installed residential solar capacity in the world by 2024!
Wind Energy
The use of wind power is becoming more important due to the growth in capacity. Japan is experimenting with the idea of installing offshore turbines to replace many of their nuclear reactors, as a result of the country's 2011 nuclear disaster in Fukushima. A recent project agreement has been signed to build offshore wind farms in northern Japan, with each farm capable of producing 140 MW of power.

Around the world, onshore wind capacity is expected to expand by 57% to 850 GW by 2024 with annual additions led by the US and China. Offshore wind capacity is predicted to increase by 3 times to 65 GW by 2024.
Check This Out Next: Antarctica Heatwave: When, Why and What It Means Hydroelectric Power Rises
According to the IEA, hydropower will continue to be the world's main source of renewable power in 2024. It is expected to increase by 9% (121 GW) in capacity over the forecast period, led by China, India and Brazil.

However, there has been a slow down in the two largest markets, China and Brazil.This is because of the rising investment costs as a result of limited remaining economical sites and extra money used to address social and environmental impacts.
Geothermal Experiences a Surprising Boost
As demand for efficient heating solutions increases, the US market for geothermal heat pumps will be greater than $2 billion by 2024 . Geothermal capacity is anticipated to grow 28%, reaching 18GW by 2024, with Asia responsible for one-third of global expansions. During the forecast period, Kenya's geothermal capacity is expected to overtake Iceland's! According to the Department of Energy, geothermal solutions will generate 8.5% of all electricity in the US by 2050.
A Promising Outlook for Green Power
Renewable energy will continue to rise in the upcoming years, pushing out fossil fuels as an electricity source and reducing greenhouse gas emissions. It is important for governments to continue to take on renewable energy as their main generators of electricity and phase out fossil fuels for a sustainable future.

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What is the Future of Renewable Energy? - Earth.Org Kids

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The amount of future renewable energy sources is expected to expand 50% between 2019 and 2024, led by solar power! A report by The International Energy Agency found that solar, wind and hydro power projects are being developed at their fastest rate in four years. - Renewable Energy: How Will it Grow?

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We prepared a kid-friendly guide with all you need to know about what is wind energy, how it works to why is it so important.

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Solar power is a valuable energy source that can be used to heat buildings and produce electricity. It is the most abundant, fastest, and cheapest energy source on earth, and it generates minimal greenhouse gas emissions. Countries around the world are planning to achieve net-zero emissions in the upcoming decades and solar energy could be the secret weapon to reach this ambitious goal. -
Ancient Egyptians were the first people known to use the energy from sunlight to heat their homes. Fast forward to today, societies around the world have developed innovative technologies that allow us to turn the sun's energy into electricity that powers heating and cooling systems, transportation, lighting, and ventilation, just to name a few. China is by far the largest investor, but the United States, Japan, Australia, and India are also betting on this incredible resource.

Before we move on to some of the advantages and disadvantages of solar, it is worth answering a question: how does solar energy work?

What is Solar Energy and How Does It Work?

Humans install solar panels in places where they are mostly exposed to the sunlight, for example on the roof of a house. The sun shines directly on so-called photovoltaic (PV) panels, which contain cells that can capture the sunlight's energy. This energy generates electrical charges that move around the cells, causing electricity to flow.

Believe it or not, solar panels can even work on cloudy days when the sun is not visible at all!

Advantages of Solar Energy

Solar is a renewable energy source: As the name suggests, solar power is a resource that never runs out. Renewable energy sources are not only cleaner but also cheaper and easier to produce than any fossil fuel.

Solar energy is immensely abundant: In fact, solar is the most abundant energy source on the planet and throughout the years, we managed to develop innovative technologies that could allow us to depend entirely on solar for the rest of our existence. Surprisingly enough, an hour and a half of sunlight that reaches the planet's surface generates enough power to meet all of humanity's energy consumption for an entire year!

Solar Technologies Are Getting More Efficient: Over the years, scientists have made some important advances in the development of solar technologies, improving the efficiency of solar panels, which can now last up to 30 years!

Solar Panels Are Getting Cheaper: While the cost of panels itself is the most critical part of the overall equation, solar is definitely a cheap source of power that can considerably lower the electricity bill in the long run.

Solar Life Cycle Generates Minimal Greenhouse Gas Emissions: solar power produces no emissions during generation itself and it has a considerably smaller carbon footprint than fossil fuels.

Disadvantages of Solar Energy

Solar Energy is Still Expensive for Households: Did we not just say that solar energy is getting cheaper? Well, it is true. However, purchasing a solar system requires a significant amount of money at the beginning to cover the costs of panels, inverter, batteries, wiring, and the installation of the system itself.

Solar Energy is Weather Dependent: this technology is not equally efficient around the world. While solar power can be generated on a cloudy day, some level of daylight is still required in order to capture the sun's energy, and the amount of energy that can be produced varies greatly depending on the amount and quality of direct sunlight that the panels receive as well as the size, number, and locations of the panels.

Solar Power Plants Are Not the Most Environmentally Friendly Option: First and foremost, solar power plants require space. Another factor to consider is the management and disposal of dangerous materials such as metals and glass needed to build some components of solar infrastructure. Indeed, producing them pollutes the environment.

Should We Still Use Solar Energy?

Solar energy is an incredibly valuable and infinite resource that can play a huge role in the world by helping to reach the goal of zero-net emissions that many countries have set. This renewable resource, along with all others, certainly has undeniable potential and it is still a better alternative to environmentally unfriendly fossil fuels, beyond being the best chance we have at stopping global warming.

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Solar power is the most abundant, fastest, and cheapest energy source on earth. It can be used to heat buildings and produce electricity.

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Fun Kids - the UK's children's radio station

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How do you generate electricity from water? What is hydroelectric power?

Here's the need-to-know stuff about the energy source, hydroelectric power!

Description

Hydroelectric power harnesses the energy in running water!

Where can you find hydroelectric power?

Hydroelectric dams can be found all over the world, where large amounts of water can be trapped behind a reservoir.

How is it made into electricity?

Most hydro schemes create a reservoir, usually by building a large dam to flood a valley. This trapped water is allowed to escape through pipes in the dam. When the water flows through the pipes, it turns a turbine that is linked to a generator that produces electricity.

'Run of the River' hydro systems don't use a dam and reservoir, but harness the energy in fast-flowing rivers!

What are the advantages of using hydroelectric power?

Water is plentiful, free, and renewable.

Hydro-electric power does not produce any carbon dioxide emissions when using water to produce electricity.

Electricity can be generated 24 hours a day as long as there is enough water. But this can't happen every day as the reservoir needs time to fill up again from time to time.

The dam gates can be opened and closed to control when the electricity is made.

The amount of electricity produced can also be controlled by changing how much water can flow.

It is much more reliable than wind and solar power, although it does depend on enough rain, especially for 'run of the river' systems.

What are the disadvantages of using hydroelectric power?

It is very expensive to build a dam, and construction can produce a lot of emissions.

When a dam is built, a huge area is flooded to make a lake. The water displaces the people and animals living there.

It can be difficult to find a suitable site for a reservoir or a dam. There are very few available sites for new plant in the UK.

There can be negative environmental impacts. Water quality and quantity downstream can be affected.

Click here for more energy facts!

We've got a whole series about energy, electricity, and power generation! It's called Curious Kate, and you can listen to it below!

EXPLORE THIS SERIES

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Hydroelectric Power: Energy Source Fact File! - Fun Kids - the UK's children's radio station

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Here's the need-to-know stuff about the energy source, hydroelectric power! Description Hydroelectric power harnesses the energy in running water! Where can you find hydroelectric power? Hydroelectric dams can be found more "

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Hydropower is energy in moving water

People have a long history of using the force of water flowing in streams and rivers to produce mechanical energy. Hydropower was one of the first sources of energy used for electricity generation and is usually the largest single renewable energy source of annual electricity generation in the United States.

n 2022, hydroelectricity accounted for about 6.2% of total U.S. utility-scale electricity generation and 28.7% of total utility-scale renewable electricity generation. ¹ Hydroelectricity generation varies annually, and it's share of total U.S. electricity generation generally decreased from the 1950's through 2020, mainly because of increases in electricity generation from other sources. Hydroelectricity's percentage share of total annual U.S. electricity generation in 2001 through 2022 averaged about 6.7%.

Hydropower relies on the water cycle

1. Solar energy heats water on the surface of rivers, lakes, and oceans, which causes the water to evaporate.

2. Water vapor condenses into clouds and falls as precipitation-rain and snow.

3. Precipitation collects in streams and rivers, which empty into oceans and lakes, where it evaporates and begins the cycle again.

The amount of precipitation that drains into rivers and streams in a geographic area determines the amount of water available for producing hydropower. Seasonal and long-term changes in rain and snowfall, such as droughts, have a big effect on hydropower production.

Hydroelectric power is produced with moving water

Because the source of hydroelectric power is water, hydroelectric power plants are usually located on or near a water source. The volume of the water flow and the change in elevation (or fall) from one point to another determine the amount of available energy in moving water. In general, the greater the water flow and the higher the fall, the more electricity a hydropower plant can produce. A big river, such as the Columbia River that forms the border between Oregon and Washington, carries a great deal of energy in its flow. Water descending rapidly from a high point, such as Niagara Falls in New York, also has substantial energy in its flow.

At hydropower plants, water flows through a pipe, or penstock, then pushes against and turns blades in a turbine to spin a generator to produce electricity.

Conventional hydroelectric facilities include

Run-of-the-river systems, where the force of the river's current applies pressure on a turbine. The facilities may have a weir (a short or low dam) in the water course to divert water flow to hydro turbines.

Storage systems, where water accumulates in reservoirs created by dams on streams and rivers and is released through hydro turbines as needed to generate electricity. Most U.S. hydropower facilities have dams and storage reservoirs.

Pumped-storage hydropower facilities are a type of hydroelectric storage system where water is pumped from a water source up to a storage reservoir at a higher elevation and is released from the upper reservoir to power hydro turbines located below the upper reservoir. The electricity for pumping may be from hydroturbines or from other types of power plants including fossil fuel or nuclear power plants. They usually pump water to storage when electricity demand (or use) and prices are low and release the stored water to generate electricity when electricity demand and prices are higher. Pumped-storage hydroelectric systems generally use more electricity to pump water to the upper water storage reservoirs than they produce with the stored water.

History of hydropower

Hydropower is one of the oldest sources of energy for producing mechanical and electrical energy. Hydropower was used thousands of years ago to turn paddle wheels to help grind grain. Before steam power and electricity were available in the United States, grain and lumber mills were powered directly with hydropower. The first industrial use of hydropower to generate electricity in the United States was in 1880, when 16 brush-arc lamps were powered using a water turbine at the Wolverine Chair Factory in Grand Rapids, Michigan. The first U.S. hydroelectric power plant opened on the Fox River near Appleton, Wisconsin, on September 30, 1882. Most U.S. hydroelectricity is now produced at large dams on major rivers, and most of these hydroelectric dams were built before the mid-1970s.

Most U.S. hydroelectricity generation capacity is in the West

There are hydropower facilities in nearly every state. Most hydroelectricity is produced at large dams built by the federal government, and many of the largest hydropower dams are in the western United States.

About half of U.S. hydroelectricity generation capacity ² is in Washington, California, and Oregon. Washington has the most hydroelectric generating capacity of any state and is the site of the Grand Coulee Dam, the largest hydropower facility in the United States. New York has the largest hydroelectricity generation capacity of all states east of the Mississippi River, followed by Alabama.

In 2022, total U.S. conventional hydroelectricity net summer electricity generation capacity 79,980 megawatts (MW)-or about 80 million kilowatts.

Hydroelectricity generation varies with precipitation levels

Because hydroelectricity generation depends on precipitation, and precipitation levels vary seasonally and annually, the ranking of each state in annual hydroelectricity generation may be different from its ranking in generation capacity.

In 2022, total U.S. conventional hydroelectricity generation was equal to about 6.2% (about 262 billion kilowatthours [kWh]) of total U.S. utility-scale electricity generation

Most dams were not built for electricity generation

Only a small percentage of the dams in the United States produce electricity. Most dams were constructed for irrigation and flood control and do not have hydroelectricity generators. The U.S. Department of Energy estimated that in 2012, non-powered dams in the United States had a total of 12,000 megawatts (MW) of potential hydropower capacity.

Hydropower generators produce clean electricity, but hydropower does affect the environment

Most dams in the United States were built mainly for flood control, municipal water supply, and irrigation water. Although many of these dams have hydroelectric generators, only a small number of dams were built specifically for hydropower generation. Hydropower generators do not directly emit air pollutants. However, dams, reservoirs, and the operation of hydroelectric generators can affect the environment.

Did you know?

A dam that creates a reservoir (or a dam that diverts water to a run-of-river hydropower plant) may obstruct fish migration. A dam and reservoir can also change natural water temperatures, water chemistry, river flow characteristics, and silt loads. All of these changes can affect the ecology and the physical characteristics of the river. These changes may have negative effects on native plants and on animals in and around the river. Reservoirs may cover important natural areas, agricultural land, or archeological sites. A reservoir and the operation of the dam may also result in the relocation of people. The physical impacts of a dam and reservoir, the operation of the dam, and the use of the water can change the environment over a much larger area than the area a reservoir covers.

Manufacturing the concrete and steel in hydropower dams requires equipment that may produce emissions. If fossil fuels are the energy sources for making these materials, then the emissions from the equipment could be associated with the electricity that hydropower facilities generate. However, given the long operating lifetime of a hydropower plant (50 years to 100 years) these emissions are offset by the emissions-free hydroelectricity.

Greenhouse gases (GHG) such as carbon dioxide and methane form in natural aquatic systems and in human-made water storage reservoirs as a result of the aerobic and anaerobic decomposition of biomass in the water. The exact amounts of GHG that form in and are emitted from hydropower reservoirs is uncertain and depend on many site specific and regional factors.

Fish ladders help salmon reach their spawning grounds

Hydropower turbines kill and injure some of the fish that pass through the turbine. The U.S. Department of Energy has sponsored the research and development of hydroturbines that could reduce fish deaths to lower than 2%, in comparison with fish kills of 5% to 10% for the best existing turbines.

Many species of fish, such as salmon and shad, swim up rivers and streams from the sea to reproduce in their spawning grounds in the beds of rivers and streams. Dams can block their way. Different approaches to fixing this problem include the construction of fish ladders and elevators that help fish move around or over dams to the spawning grounds upstream.

The gravitational pull of the moon and sun along with the rotation of the earth cause the tides. In some places, tides cause water levels near the shore to vary up to 40 feet. People in Europe harnessed this movement of water to operate grain mills more than a 1,000 years ago. Today, tidal energy systems generate electricity. Producing tidal energy economically requires a tidal range of at least 10 feet.

Tidal barrages

One type of tidal energy system uses a structure similar to a dam called a barrage. The barrage is installed across an inlet of an ocean bay or lagoon that forms a tidal basin. Sluice gates on the barrage control water levels and flow rates to allow the tidal basin to fill on the incoming high tides and to empty through an electricity turbine system on the outgoing ebb tide. A two-way tidal power system generates electricity from both the incoming and outgoing tides.

A potential disadvantage of tidal power is the effect a tidal station can have on plants and animals in estuaries of the tidal basin. Tidal barrages can change the tidal level in the basin and increase turbidity (the amount of matter in suspension in the water). They can also affect navigation and recreation.

Several tidal power barrages operate around the world. The Sihwa Lake Tidal Power Station in South Korea has the largest electricity generation capacity at 254 megawatts (MW). The oldest and second-largest operating tidal power plant is in La Rance, France, with 240 MW of electricity generation capacity. The next largest tidal power plant is in Annapolis Royal in Nova Scotia, Canada, with 20 MW of electricity generation capacity. China, Russia, and South Korea all have smaller tidal power plants.

The United States does not have any tidal power plants, and it only has a few sites where tidal energy could be economical to produce. France, England, Canada, and Russia have much more potential to use tidal power.

Tidal turbines

Tidal turbines look similar to wind turbines. They can be placed on the sea floor where there is strong tidal flow. Because water is about 800 times denser than air, tidal turbines have to be much sturdier and heavier than wind turbines. Tidal turbines are more expensive to build than wind turbines but capture more energy with the same size blades. A demonstration tidal turbine project is under development in the East River of New York.

Tidal fences

A tidal fence is a type of tidal power system that has vertical axis turbines mounted in a fence or row placed on the sea bed, similar to tidal turbines. Water passing through the turbines generates electricity. As of the end of 2021, no tidal fence projects were operating.

Waves have a lot of energy

CETO underwater wave energy device

Waves form as wind blows over the surface of open water in oceans and lakes. Ocean waves contain tremendous energy. The theoretical annual energy potential of waves off the coasts of the United States is estimated to be as much as 2.64 trillion kilowatthours, which is equal to about 64% of total U.S. utility-scale electricity generation in 2021. ( Utility-scale generation is from electric generators/power plants with at least one megawatt of generation capacity.) The west coasts of the United States and Europe, and the coasts of Japan and New Zealand, have potential sites for harnessing wave energy. Many different methods and technologies for capturing and converting wave energy to electricity are under development. These methods include placing devices on or just below the surface of the water and anchoring devices to the ocean floor.

Different ways to channel the power of waves

One way to harness wave energy is to bend or focus waves into a narrow channel to increase their size and power and to spin the turbines that generate electricity. Waves can also be channeled into a catch basin or reservoir where the water flows to a turbine at a lower elevation, similar to the way a hydropower dam operates.

The U.S. Department of Energy's Marine and Hydrokinetic Technology Database provides information on marine and hydrokinetic renewable energy, in the United States and around the world.

Ocean thermal energy conversion produces energy from temperature differences in ocean waters

Ocean thermal energy conversion (OTEC) is a process or technology for producing energy by harnessing the temperature differences (thermal gradients) between ocean surface waters and deep ocean waters.

Energy from the sun heats the surface water of the ocean. In tropical regions, surface water can be much warmer than deep water. This temperature difference can be used to produce electricity and to desalinate ocean water. Ocean Thermal Energy Conversion (OTEC) systems use a temperature difference (of at least 36° Fahrenheit or 20° Celsius) to power a turbine to produce electricity. Warm surface water is pumped through an evaporator containing a working fluid. The vaporized fluid drives a turbine/generator. The vaporized fluid is turned back to a liquid in a condenser cooled with cold ocean water pumped from deeper in the ocean. OTEC systems using seawater as the working fluid can use the condensed water to produce desalinated water.

The United States became involved in OTEC research in 1974 with the establishment of the Natural Energy Laboratory of Hawaii Authority. The laboratory is one of the world's leading test facilities for OTEC technology. The laboratory operated a 250 kilowatt (kW) demonstration OTEC plant for six years in the 1990s. The United States Navy supported the development of a 105 kW demonstration OTEC plant at the laboratory site. This facility became operational in 2015 and supplies electricity to the local electricity grid.

Other larger OTEC systems are in development or planned in several countries, mostly to supply electricity and desalinated water for island communities.

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People have a long history of using the force of water flowing in streams and rivers to produce mechanical energy. Hydropower was one of the first sources of energy used for electricity generation and is usually the largest single renewable energy source of annual electricity generation in the United States.

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Energy from the sun

The sun has produced energy for billions of years and is the ultimate source for all of the energy sources and fuels that we use today. People have used the sun's rays (solar radiation) for thousands of years for warmth and to dry meat, fruit, and grains. Over time, people developed technologies to collect solar energy for heat and to convert it into electricity.

Collecting and using solar thermal (heat) energy

An example of an early solar energy collection device is the solar oven (a box for collecting and absorbing sunlight). In the 1830s, British astronomer John Herschel used a solar oven to cook food during an expedition to Africa. People now use many different technologies for collecting and converting solar radiation into heat energy for a many uses.

Water for use in homes, buildings, or swimming pools

The inside of homes, greenhouses, and other buildings

Fluids to high temperatures in solar thermal power plants

Solar photovoltaic systems convert sunlight into electricity

Solar photovoltaic (PV) devices, or solar cells, change sunlight directly into electricity. Small PV cells can power calculators, watches, and other small electronic devices. Arrangements of many solar cells in PV panels and arrangements of multiple PV panels in PV arrays can produce electricity for an entire house. Some PV power plants have large arrays that cover many acres to produce electricity for thousands of homes.

Solar energy has benefits and some limitations

Solar energy systems do not produce air pollutants or carbon dioxide.

Solar energy systems on buildings have minimal effects on the environment.

The amount of sunlight that arrives at the earth's surface is not constant. The amount of sunlight varies depending on location, time of day, season of the year, and weather conditions.

The amount of sunlight reaching a square foot of the earth's surface is relatively small, so a large surface area is necessary to absorb or collect a useful amount of energy.

Solar energy is sunshine

Sunshine is radiant energy from the sun. The amount of solar radiation, or solar energy, that the earth receives each day is many times greater than the total amount of all energy that people consume each day. Use of solar energy, especially for electricity generation, has increased a lot in the United States and around the world in the past 30 years.

Latitude, climate, and weather patterns are major factors that affect insolation -the amount of solar radiation received on a given surface area during a specific amount of time. Locations nearer the equator and in arid climates generally receive higher amounts of insolation than other locations. Clouds, dust, volcanic ash, and pollution in the atmosphere affect insolation levels at the surface. Buildings, trees, and mountains may shade a location during different times of the day in different months of the year. Seasonal (monthly) variations in solar resources increase with increasing distance from the earth's equator.

The type of solar collector also determines the type of solar radiation and level of insolation that a solar collector receives. Concentrating solar collector systems, such as those used in solar thermal-electric power plants, require direct solar radiation, which is generally greater in arid regions with few cloudy days. Flat-plate solar thermal and photovoltaic (PV) collectors are able to use global solar radiation, which includes diffuse (scattered) and direct solar radiation. Learn more about solar radiation.

Solar thermal collectors

Low-temperature solar thermal collectors absorb the sun's heat energy to heat water for washing and bathing or for swimming pools, or to heat air inside buildings.

Concentrating collectors

Concentrating solar energy technologies use mirrors to reflect and concentrate sunlight onto receivers that absorb solar energy and convert it to heat. We can use this thermal energy for heating buildings or to produce electricity with a steam turbine or a heat engine that drives a generator.

Photovoltaic systems

Photovoltaic (PV) cells convert sunlight directly into electricity. PV systems can range from systems that provide tiny amounts of electricity for watches and calculators to systems that provide the amount of electricity that hundreds or thousands of homes use. Millions of houses and buildings around the world have PV systems on their roofs and there are many large PV power plants.

Use of solar energy

The U.S. Energy Information Administration (EIA) estimates that total solar energy use in the United States increased from about 0.06 trillion British thermal units (Btu) in 1984 to about 1,870 trillion Btu in 2022. Solar electricity generation accounted for about 97% of total solar energy use in 2022 and direct use of solar energy for space and water heating accounted for about 3%.

Total U.S. solar electricity generation increased from about 5 million kWh in 1984 (nearly all from utility-scale, solar thermal-electric power plants) to about 204 billion kWh in 2022. In 2022, utility-scale PV power plants accounted for 70% of total solar electricity generation, small-scale PV systems accounted for 29%, and utility-scale solar thermal-electric power plants accounted for 1%. Utility-scale power plants have at least 1,000 kilowatts (kW) (or one megawatt [MW]) of electricity generation capacity. Small-scale PV systems have less than one MW generation capacity.

According to EIA's International Energy Statistics, total world solar electricity generation grew from 0.4 billion kWh in 1990 to about 1.306 billion (about 1.3 trillion) kWh in 2021. The top five producers of solar electricity and their percentage shares of world total solar electricity generation in 2021 were:

Photovoltaic cells convert sunlight into electricity

A photovoltaic (PV) cell, commonly called a solar cell, is a nonmechanical device that converts sunlight directly into electricity. Some PV cells can convert artificial light into electricity.

Photons carry solar energy

Sunlight is composed of photons, or particles of solar energy. These photons contain varying amounts of energy that correspond to the different wavelengths of the solar spectrum.

A PV cell is made of semiconductor material. When photons strike a PV cell, they may reflect off the cell, pass through the cell, or be absorbed by the semiconductor material. Only the absorbed photons provide energy to generate electricity. When the semiconductor material absorbs enough sunlight (solar energy), electrons are dislodged from the material's atoms. Special treatment of the material surface during manufacturing makes the front surface of the cell more receptive to the dislodged, or free, electrons so that the electrons naturally migrate to the surface of the cell.

The flow of electricity

The movement of electrons, each carrying a negative charge, toward the front surface of the cell creates an imbalance of electrical charge between the cell's front and back surfaces. This imbalance, in turn, creates a voltage potential like the negative and positive terminals of a battery. Electrical conductors on the cell absorb the electrons. When the conductors are connected in an electrical circuit to an external load, such as a battery, electricity flows in the circuit.

The efficiency of photovoltaic systems varies by the type of photovoltaic technology

The efficiency at which PV cells convert sunlight to electricity varies by the type of cell material and technology. The efficiency of PV modules averaged less than 10% in the mid-1980s, increased to around 15% by 2015, and is now approaching 20% for state-of-the art modules. Experimental PV cells and PV cells for space satellites are nearly 50% efficient.

How photovoltaic systems operate

The PV cell is the basic building block of a PV system. Individual cells can vary in size from about 0.5 inches to about 4 inches across. However, one cell only produces 1 or 2 Watts, which is only enough electricity for small uses, such as for powering calculators or wristwatches.

PV cells are electrically connected in a packaged, weather-tight PV module or panel. PV modules vary in size and in the amount of electricity they can produce. PV module electricity generating capacity increases with the number of cells in the module or in the surface area of the module. PV modules can be connected in groups to form a PV array. A PV array can be composed of two or hundreds of PV modules. The number of PV modules connected in a PV array determines the total amount of electricity the array can generate.

Photovoltaic cells generate direct current (DC) electricity. This DC electricity can be used to charge batteries that, in turn, power devices that use direct current electricity. Nearly all electricity is supplied as alternating current (AC) in electric power lines. Devices called inverters are used on PV modules or in arrays to convert the DC electricity to AC electricity.

PV cells and modules will produce the largest amount of electricity when they are directly facing the sun. PV modules and arrays can use tracking systems that move the modules to constantly face the sun, but these systems are expensive and are mostly used in large PV power plants. Most PV systems on buildings have modules in a fixed position with the modules facing directly south (in the northern hemisphere-directly north in the southern hemisphere). Learn more about PV collector tilt angles and PV collector tracking systems.

Did you know?

Applications of photovoltaic systems

The smallest photovoltaic systems power calculators and wristwatches. Larger systems can provide electricity to pump water, to power communications equipment, to supply electricity for a single home or business, or to form large arrays that supply electricity to thousands of electricity consumers.

PV systems can supply electricity in locations where electricity distribution systems (power lines) do not exist, and they can also supply electricity to an electric power grid.

PV arrays can be installed quickly and can be any size.

The environmental effects of PV systems located on buildings is minimal.

History of photovoltaics

The first practical PV cell was developed in 1954 by Bell Telephone researchers. Beginning in the late 1950s, PV cells were used to power U.S. space satellites. By the late 1970s, PV panels were providing electricity in remote, or off-grid, locations that did not have electric power lines. Since 2004, most of the PV panels installed in the United States have been in grid-connected systems on homes, buildings, and central-station power facilities. Technical advances, lower costs for PV systems, and financial incentives and government policies have helped to greatly expand PV use since the mid-1990s. Hundreds of thousands of grid-connected PV systems are now installed in the United States.

EIA estimates that electricity generated at utility-scale PV power plants increased from 6 million kilowatthours (kWh) in 2004 to 143 billion kWh in 2022. Utility-scale power plants have at least 1,000 kilowatts (or one megawatt) of electricity generating capacity. EIA estimates that 59 billion kWh were generated by small-scale grid-connected PV systems in 2022, up from 11 billion kWh in 2014. Small-scale PV systems are systems that have less than 1,000 kilowatts of electricity generation capacity. Most small-scale PV systems are located on buildings and are sometimes called rooftop PV systems.

Solar thermal power systems use concentrated solar energy

Solar thermal power (electricity) generation systems collect and concentrate sunlight to produce the high temperature heat needed to generate electricity. All solar thermal power systems have solar energy collectors with two main components: reflectors (mirrors) that capture and focus sunlight onto a receiver. In most types of systems, a heat-transfer fluid is heated and circulated in the receiver and used to produce steam. The steam is converted into mechanical energy in a turbine, which powers a generator to produce electricity. Solar thermal power systems have tracking systems that keep sunlight focused onto the receiver during the day as the sun changes position in the sky.

Solar thermal power systems may also have a thermal energy storage system component that allows the solar collector system to heat an energy storage system during the day, and the heat from the storage system is used to produce electricity in the evening or during cloudy weather. Solar thermal power plants may also be hybrid systems that use other fuels (usually natural gas) to supplement energy from the sun during periods of low solar radiation.

Types of concentrating solar thermal power plants

Linear concentrating systems

Linear concentrating systems collect the sun's energy using long, rectangular, curved (U-shaped) mirrors. The mirrors focus sunlight onto receivers (tubes) that run the length of the mirrors. The concentrated sunlight heats a fluid flowing through the tubes. The fluid is sent to a heat exchanger to boil water in a conventional steam-turbine generator to produce electricity. There are two major types of linear concentrator systems: parabolic trough systems, where receiver tubes are positioned along the focal line of each parabolic mirror, and linear Fresnel reflector systems, where one receiver tube is above several mirrors to allow the mirrors greater mobility in tracking the sun.

A linear concentrating collector power plant has a large number, or field, of collectors in parallel rows with a north-south orientation so that the mirrors track the sun from east to west and concentrate sunlight continuously onto the receiver tubes during the day.

Parabolic troughs

Parabolic trough power plant

A parabolic trough collector has a long parabolic (curved-shaped) reflector that focuses the sun's rays on a receiver pipe located at the focus of the parabola. The collector moves to focus sunlight on the receiver as the sun moves through the sky during the day.

Because of its parabolic shape, a trough can focus the sunlight from 30 times to 100 times its normal intensity (concentration ratio) on the receiver pipe, located along the focal line of the trough, achieving operating temperatures higher than 750°F.

Parabolic trough linear concentrating systems are used in one of the longest operating solar thermal power facilities in the world, the Solar Energy Generating System (SEGS) located in the Mojave Desert in California. The facility has had nine separate plants over time, with the first plant in the system, SEGS I, operating from 1984 to 2015, and the second, SEGS II, operating from 1985 to 2015. SEGS III-VII (3-7), each with net summer electric generation capacities of 36 megawatts (MW), came online in 1986, 1987, and 1988. SEGS VIII (8) and IX (9), each with a net summer electric generation capacity of 88 MW, began operation in 1989 and 1990, respectively. SEGS 3, 4, 5, 6, 7, and 8 all ceased operation in 2021, leaving only SEGS 9 in operation as of December 31, 2021.

Solana Generating Station: a 296 MW project in Gila Bend, Arizona

Mojave Solar Project: a 275 MW project in Barstow, California

Genesis Solar Energy Project: a 250 MW project in Blythe, California

Nevada Solar One: a 69 MW plant near Boulder City, Nevada

Linear Fresnel reflectors

Linear Fresnel reflector (LFR) systems are similar to parabolic trough systems in that mirrors (reflectors) concentrate sunlight onto a receiver located above the mirrors. These reflectors use the Fresnel lens effect, which allows for a concentrating mirror with a large aperture and short focal length. These systems are capable of concentrating the sun's energy to about 30 times its normal intensity. Compact linear Fresnel reflector (CLFR)-also referred to as a concentrating linear Fresnel reflector-are a type of LFR technology with multiple absorbers within the vicinity of the mirrors. Multiple receivers allow the mirrors to change their position so they do not shade other reflectors. This improves system efficiency and reduces costs. A demonstration CLFR solar power plant was built near Bakersfield, California, in 2008, but it is currently not operating.

Solar power towers

A solar power tower system uses a large field of flat, sun-tracking mirrors called heliostats to reflect and focus sunlight onto a receiver on the top of a tower. Sunlight can be concentrated as much as 1,500 times. Some power towers use water as the heat-transfer fluid. Advanced designs are experimenting with molten nitrate salt because of its superior heat transfer and energy storage capabilities. The thermal energy-storage allows the system to produce electricity during cloudy weather or at night.

Ivanpah Solar Power Facility: a facility with three separate collector fields and towers with a combined net summer electric generation capacity of 393 MW in Ivanpah Dry Lake, California

Crescent Dunes Solar Energy Project: Crescent Dunes Solar Energy Project: a 110 MW one-tower facility with an energy storage component in Tonapah, Nevada

Solar dish/engines

Solar dish/engine systems use a mirrored dish similar to a very large satellite dish. To reduce costs, the mirrored dish usually has many small flat mirrors formed into a dish shape. The dish-shaped surface directs and focuses sunlight onto a thermal receiver, which absorbs and collects the heat and transfers it to an engine generator. The most common type of heat engine used in dish/engine systems is the Stirling engine. This system uses the fluid heated by the receiver to move pistons and create mechanical power. The mechanical power runs a generator or alternator to produce electricity.

Solar dish/engine systems always point straight at the sun and concentrate solar energy at the focal point of the dish. A solar dish's concentration ratio is much higher than linear concentrating systems, and it has a working fluid temperature higher than 1,380°F. The power-generating equipment of a solar dish can be placed at the focal point of the dish, making it well suited for remote locations, or the energy may be collected from many dishes and converted into electricity at a central point.

There are no utility-scale solar dish/engine projects in commercial operation in the United States.

Heating with the sun's energy

People use solar thermal energy to heat water and air. The two general types of solar heating systems are passive systems and active systems.

Passive solar space heating happens when the sun shines through the windows of a building and warms the interior. Building designs that use passive solar heating usually have south-facing windows that allow the sun to shine on solar heat-absorbing walls or floors during the day in the winter. The absorbed solar energy heats the building by natural radiation and convection at night. Window overhangs or shades block the sun from entering the windows during the summer to keep the building cool.

Active solar heating systems use a collector and a fluid that absorbs solar radiation. Fans or pumps circulate air or heat-absorbing liquids through collectors and then transfer the heated fluid directly to a room or to a heat storage system. Active solar water heating systems usually have a tank for storing solar heated water.

Solar collectors are either nonconcentrating or concentrating

Nonconcentrating collectors-The collector area (the area that intercepts the solar radiation) is the same as the absorber area (the area absorbing the radiation). Solar systems for heating water or air usually have nonconcentrating collectors. Flat-plate collectors are the most common type of nonconcentrating collectors for water and space heating in buildings and are used when temperatures lower than 200°F are sufficient.

A flat metal plate that intercepts and absorbs solar energy

A transparent cover that allows solar energy to pass through the cover and reduces heat loss from the absorber

A layer of insulation on the back of the absorber to reduce heat loss

Solar water heating collectors have metal tubes attached to the absorber. A heat-transfer fluid is pumped through the absorber tubes to remove heat from the absorber and transfer the heat to water in a storage tank. Solar systems for heating swimming pool water in warm climates usually do not have covers or insulation for the absorber, and pool water is circulated from the pool through the collectors and back to the pool.

Solar air heating systems use fans to move air through flat-plate collectors and into the interior of buildings.

Concentrating collectors -The area intercepting the solar radiation is greater, sometimes hundreds of times greater, than the absorber area. The collector focuses, or concentrates, solar energy onto an absorber. The collector usually moves so that it keeps sunlight focused on the absorber. Solar thermal power plants use concentrating solar collector systems because they can produce high temperature heat.

Solar energy systems/power plants do not produce air pollution, water pollution, or greenhouse gases. Using solar energy can have a positive, indirect effect on the environment when solar energy replaces or reduces the use of other energy sources that have larger effects on the environment.

Some toxic materials and chemicals are used to make the photovoltaic (PV) cells that convert sunlight into electricity. Some solar thermal systems use potentially hazardous fluids to transfer heat. Leaks of these materials could be harmful to the environment. U.S. environmental laws regulate the use and disposal of these types of materials.

As with any type of power plant, large solar power plants can affect the environment near their locations. Clearing land for construction and the placement of the power plant may have long-term effects on the habitats of native plants and animals. Some solar power plants may require water for cleaning solar collectors and concentrators or for cooling turbine generators. Using large volumes of ground water or surface water in some arid locations may affect the ecosystems that depend on these water resources. In addition, the beam of concentrated sunlight a solar power tower creates can kill birds and insects that fly into the beam.

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The sun has produced energy for billions of years and is the ultimate source for all of the energy sources and fuels that we use today. People have used the sun's rays (solar radiation) for thousands of years for warmth and to dry meat, fruit, and grains.

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Energy from moving air

Wind is caused by uneven heating of the earth's surface by the sun. Because the earth's surface is made up of different types of land and water, it absorbs the sun's heat at different rates. One example of this uneven heating is the daily wind cycle.

The daily wind cycle

During the day, air above the land heats up faster than air over water. Warm air over land expands and rises, and heavier, cooler air rushes in to take its place, creating wind. At night, the winds are reversed because air cools more rapidly over land than it does over water.

In the same way, the atmospheric winds that circle the earth are created because the land near the earth's equator is hotter than the land near the North Pole and the South Pole.

Wind energy for electricity generation

Today, wind energy is mainly used to generate electricity. Water-pumping windmills were once used throughout the United States and some still operate on farms and ranches, mainly to supply water for livestock.

How wind turbines work

Wind turbines use blades to collect the wind's kinetic energy. Wind flows over the blades creating lift (similar to the effect on airplane wings), which causes the blades to turn. The blades are connected to a drive shaft that turns an electric generator, which produces the electricity.

Electricity generation with wind

Total annual U.S. electricity generation from wind energy increased from about 6 billion kilowatthours (kWh) in 2000 to about 435 billion kWh in 2022. In 2022, wind turbines were the source of about 10.2% of total U.S. utility-scale electricity generation. Utility scale includes facilities with at least one megawatt (1,000 kilowatts) of electricity generation capacity

New technologies have decreased the cost of producing electricity from wind, and growth in wind power has been encouraged by government and industry incentives.

Wind power plants require careful planning

Operating a wind power plant is more complex than simply erecting wind turbines in a windy area. Wind power plant owners must carefully plan where to position wind turbines and must consider how fast and how often the wind blows at the site.

Good places for wind turbines are where the annual average wind speed is at least 9 miles per hour (mph)-or 4 meters per second (m/s)-for small wind turbines and 13 mph (5.8 m/s) for utility-scale turbines. Favorable sites include the tops of smooth, rounded hills; open plains and water; and mountain gaps that funnel and intensify wind. Wind resources are generally more favorable for electricity generation at higher elevations above the earth's surface. Large wind turbines are placed on towers that range from about 500 feet to as much as 900 feet tall.

Wind speeds are not the same across the country

Wind energy resources vary hourly and seasonally throughout the United States. For example, in Tehachapi, California, where numerous wind turbines are located, the wind blows more frequently from April through October than it does in the winter, and the wind is usually strongest in the afternoon. These fluctuations are a result of the extreme heat of the Mojave Desert during summer months. As the hot air over the desert rises, the cooler, denser air above the Pacific Ocean rushes through the Tehachapi mountain pass to take its place. In Montana, strong winter winds channeled through Rocky Mountain valleys create more intense winds during the winter.

Fortunately, the seasonal variations in wind speeds in California and Montana match the electricity demands of consumers in those states. In California, people use more electricity in the afternoon and during the summer. In Montana, people use more electricity, in general, during the winter.

Locations of U.S. wind power projects

In 2022, 42 states had utility-scale wind power projects, which together produced about 10% (435 billion kilowatthours [kWh]) of total U.S. utility-scale electricity generation. ¹ The five states with the most electricity generation from wind in 2022 were Texas, Iowa, Oklahoma, Kansas, and Illinois. These states combined produced about 57% of total U.S. wind electricity generation in 2022

International wind power

World wind electricity generation has also increased substantially in recent years. In 1990, 16 countries generated a total of about 3.6 billion kWh of wind electricity. In 2010, 105 countries generated about 340 billion kWh, and in 2020, 129 countries (includes Puerto Rico) generated about 1,597 billion kWh of wind electricity

Offshore wind power

The waters off the coasts of the United States have significant potential for electricity generation from wind energy. There are currently two operating U.S. offshore wind energy projects: the Block Island wind farm off the coast of Rhode Island, with 30 megawatts (MW) of electricity generation capacity, and the Coastal Virginia Offshore Wind pilot project with 12 MW electricity generation capacity. As of December 2022, wind project developers reported plans for about 7,500 MW of nameplate wind electricity generation capacity in waters off the coasts of Maryland, Massachusetts, New Jersey, Rhode Island, and Virgina, and about 20 MW in Ohio state waters on Lake Erie. European countries and China lead the world in offshore wind electric generation capacity. Many other countries have and are developing offshore wind energy projects.

Horizontal-axis turbines

Vertical-axis turbines

The size of wind turbines varies widely. The length of the blades is the biggest factor in determining the amount of electricity a wind turbine can generate. Small wind turbines that can power a single home may have an electricity generating capacity of 10 kilowatts (kW). The largest wind turbines in operation have electricity generating capacities of around 15,000 kW, and larger turbines are in development. Large turbines are often grouped together to create wind power plants, or wind farms, that provide power to electricity grids.

Horizontal-axis turbines are similar to propeller airplane engines

Horizontal-axis turbines have blades like airplane propellers, and they commonly have three blades. The largest horizontal-axis turbines are as tall as 20-story buildings and have blades more than 100 feet long. Taller turbines with longer blades generate more electricity. Nearly all of the wind turbines currently in use are horizontal-axis turbines.

Vertical-axis turbines look like egg beaters

Vertical-axis turbines have blades that are attached to the top and the bottom of a vertical rotor. The most common type of vertical-axis turbine-the Darrieus wind turbine, named after the French engineer Georges Darrieus who patented the design in 1931-looks like a giant, two-bladed egg beater. Some versions of the vertical-axis turbine are 100 feet tall and 50 feet wide. Very few vertical-axis wind turbines are in use today because they do not perform as well as horizontal-axis turbines.

Wind power plants, or wind farms, produce electricity

Wind power plants, or wind farms, are clusters of wind turbines that produce large amounts of electricity. A wind farm usually has many turbines scattered over a large area. One of the United States' largest wind farms is the Horse Hollow Wind Energy Center in Texas, which at the end of 2021, had 422 wind turbines spread over about 47,000 acres. The project has a combined electricity generating capacity of about 735 megawatts (or 735,000 kilowatts).

People have been using wind energy for thousands of years

People used wind energy to propel boats along the Nile River as early as 5,000 BC. By 200 BC, simple wind-powered water pumps were used in China, and windmills with woven-reed blades were grinding grain in Persia and the Middle East.

New ways to use wind energy eventually spread around the world. By the 11th century, people in the Middle East were using windpumps and windmills extensively for food production. Merchants and the Crusaders brought wind technology to Europe. The Dutch developed large windpumps to drain lakes and marshes in the Rhine River Delta. Immigrants from Europe eventually took wind energy technology to the Western Hemisphere.

American colonists used windmills to grind grain, to pump water, and to cut wood at sawmills. Homesteaders and ranchers installed thousands of windpumps as they settled the western United States. In the late 1800s and early 1900s, small wind-electric generators (turbines) were also widely used.

When power lines were built to transmit electricity to rural areas in the 1930s, wind pump and small turbine use began to decline. However, some ranches still use windpumps to supply water for livestock. Small wind turbines are becoming more common again, mainly to supply electricity in remote and rural areas.

Wind energy use expanded in the wake of oil shortages and environmental concerns

The oil shortages of the 1970s changed the energy environment for the United States and the world. The oil shortages created an interest in developing ways to use alternative energy sources, such as wind energy, to generate electricity. The U.S. federal government supported research and development of large wind turbines. In the early 1980s, thousands of wind turbines were installed in California, largely because of federal and state policies that encouraged the use of renewable energy sources.

In the 1990s and 2000s, the U.S. federal government established incentives to use renewable energy sources in response to a renewed concern for the environment. The federal government also provided research and development funding to help reduce the cost of wind turbines and offered tax and investment incentives for wind power projects. In addition, state governments enacted new requirements for electricity generation from renewable sources, and electric power marketers and utilities began to offer electricity generated from wind and other renewable energy sources (sometimes called green power) to their customers. These policies and programs resulted in an increase in the number of wind turbines and in the amount of electricity generated from wind energy.

The share of total U.S. electricity generation from wind energy has grown from less than 1% in 1990 to about 10.2% in 2022. Financial and other incentives for electricity generation with wind energy have resulted in a large expansion of wind energy use in the United States and Europe. China has invested heavily in wind energy and is now the world's largest wind electricity generator. In 1990, 16 countries generated a total of about 3.6 billion kWh of wind electricity. In 2021, at least 128 countries (including Puerto Rico) generated about 1,808 billion kWh of wind electricity.

Wind is an emissions-free source of energy

Wind is a renewable energy source. Overall, using wind to produce energy has fewer effects on the environment than many other energy sources. Wind turbines do not release emissions that can pollute the air or water (with rare exceptions), and they do not require water for cooling. Wind turbines may also reduce the amount of electricity generation from fossil fuels, which results in lower total air pollution and carbon dioxide emissions.

An individual wind turbine has a relatively small physical footprint. Groups of wind turbines, sometimes called wind farms, are located on open land, on mountain ridges, or offshore in lakes or the ocean.

Wind turbines have effects on the environment

Modern wind turbines can be very large machines, and they may visually affect the landscape. A small number of wind turbines have also caught fire, and some have leaked lubricating fluids, but these occurrences are rare. Some people do not like the sound that wind turbine blades make as they turn in the wind. Some types of wind turbines and wind projects cause bird and bat deaths. These deaths may contribute to declines in the population of species also affected by other human-related impacts. The wind energy industry and the U.S. government are researching ways to reduce the effect of wind turbines on birds and bats.

Most wind power projects on land require service roads that add to the physical effects on the environment. Producing the metals and other materials used to make wind turbine components has impacts on the environment, and fossil fuels may have been used to produce the materials. Although most of the materials used to make wind turbines can be reused or recycled, turbine blades, as most are currently constructed, cannot be recycled. Researchers at the National Renewable Energy Laboratory (NREL) established an approach to manufacturing wind turbine blades, employing a thermoplastic resin system. These thermoplastic resins enable a manufacturing process that allows wind turbine blades to be recycled at their end of life and also reduces the energy required to manufacture blades.

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Wind is caused by uneven heating of the earth's surface by the sun. Because the earth's surface is made up of different types of land and water, it absorbs the sun's heat at different rates. One example of this uneven heating is the daily wind cycle.

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Hydroelectric power, also called hydropower, is the process of using the energy of moving water to create electricity. The water cycle and gravity come into play when it comes to moving water, so teachers can tie this article to those studies.

People have harnessed the energy from water for thousands of years. For example, we know that more than 2,000 years ago, people used water wheels to grind corn and wheat. Tidal water and river water were both used to power water wheels, which were connected to other wheels and gears to power millstones and sawmills. It was in the mid-1770s when a French engineer named Bernard Forest de Bélidor described the first modern turbine. The turbine pretty much took the place of the water wheel and was eventually involved in almost every kind of electrical power.

The new invention inspired engineers to come up with a plan to create a lot more energy from water using water turbines. The theory was to build a dam on a large river, one that has a large drop in elevation. The dam stores water in a reservoir behind it. There is a water intake close to the bottom of the dam that leads to a penstock, which is a channel for conveying water. Gravity causes the water to drop down the penstock where it heads through a turbine propeller. The turbine is turned by the moving water, causing it to produce mechanical energy, just as the water wheel did. The mechanical energy in this case is kinetic energy (the energy of motion). That energy goes into a generator, where it is converted into electricity. Power lines carry the electricity to where it is needed. The plan worked. Hydroelectric power systems at dams could soon generate enough electricity to power factories, communities, cities, and eventually, entire regions.

As of 2014, according to the Business Council for Sustainable Energy, the U.S. has over 100,000 megawatts of conventional hydropower. 1 megawatt is enough to power about 1,000 homes, so this would be enough electricity to supply 75-101 million homes. While that's only about 7 percent of the country's total electricity generation from all energy sources, the amount accounts for about 52 percent of the renewable electricity generation.
It's pretty easy to see the *pros* when it comes to hydropower:

It only requires moving water in order to work.

It is considered to be a green source of energy. It does not pollute itself. Only the construction of power plants can be potential sources of pollution.

It is a domestic source of energy.

It is a renewable resource.

It is the most affordable cost of power when spread out over the system's lifetime costs.

It is reliable. As long as there is water, electricity can be generated.

It is flexible. Water flow can be adjusted and even conserved according to the need for power.

It is safe! Compared with the use of fossil fuels and nuclear energy, hydropower is a much safer system.

There also some *cons* when it comes to hydropower:

There are numerous environmental consequences of damming water, flooding entire areas, creating massive reservoirs, changing water flow, blocking the natural course of rivers, and constructing power lines and roads.

There are only a limited number of places where these power plants can be built.

The initial expense is huge (though comparatively, so are other energy resources)

Lack of water. Droughts have a serious impact on how much hydropower can be produced.

Many of the negative impacts of hydropower center on what the damming of rivers does to the native plants and animals in the waterways that are affected. For instance, sediments build up behind dams, triggering oxygen-starved zones that can't support river life. Water temperature changes can also make survival difficult. Riparian channels and estuaries are also negatively affected.

One problem of major concern is the survival and passage of migratory native fish. Fish ladders have been installed next to dams and their designs have been improved over the years to make it somewhat easier for fish to migrate upstream where they will spawn. But the populations of native fish in the Pacific Northwest and other areas have drastically declined since rivers were dammed up to manufacture electricity.

Political pressure is building in some areas to give stronger consideration to the impact hydroelectric dams have on the ecosystem. Hundreds of hydroelectric dams have been removed in recent years, including the Elwha River project in Washington. It was determined that the small amount of energy these dams produced was not worth the damage being done to the environment.
Discussion and Research Projects:

Hydropower sounds like an excellent source for alternative energy! But the impact it has on the environment is important, too. Discuss the pros and cons presented here, and challenge students to come up with possible solutions. They should be armed with more information than we had room to include in this article.

Trace the history of hydroelectric energy in the world. Create a timetable that highlights the important discoveries.

Where are all the hydropower plants in the world today?

What is happening in areas where the dams have been torn down? Has it helped the environment? Where do people get their energy now?

How do people make use of other alternative energy resources - not just water, but solar, wind, wave, and geothermal?

Activity: How does hydropower work? Build a small waterwheel!
There are lots of designs for a simple waterwheel out there, most using cardboard, straws, and paper cups.
Here's a video showing a water wheel built from a pie tin and "other easy to find parts." Here's a more sophisticated design along with a nice lesson plan from the Maine Energy Education Curriculum:

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What's Good and What's Bad about Hydropower? - Kids Discover

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Hydroelectric power, also called hydropower, is the process of using the energy of moving water to create electricity. The water cycle and gravity come into play when it comes to

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Disadvantages of Solar Energy

The disadvantages of solar energy are becoming fewer as the industry advances and grows, creating economies of scale. Technological advances are helping solar go mainstream. Here are how the disadvantages of solar energy and the pros and cons stack up.

1. The high initial costs of installing panels

The most commonly cited solar energy disadvantage, cost, is declining as the industry expands. The initial cost to buy and install the equipment is not cheap. Still, if cost is an issue, leasing options may reduce the amount of your initial outlay. If you do choose to buy, you will need to live in your home for a number of years before the system pays for itself. It's a long-term investment better suited to property owners than renters.

2. Solar energy storage is expensive

Of the disadvantages of solar energy, the temporary decline in energy production during bad weather has been a major issue. Days with low solar energy, however, are having less of an effect due to advances in battery technology. Old technology for storing solar energy, like lead acid batteries are being replaced by alternatives. Lithium ion batteries offer greater power at a lower cost. Nickel-based batteries have an extremely long life. New technologies, like flow batteries, promise scale and durable power storage.

3. Solar doesn't work for every roof type

Not every room will work well with solar panels. Orientation matters. If your roof doesn't face the sun, you won't be able to capture enough solar energy. Roofs that angle into the sun tend to work better than flat roofs.

Roofing materials like asphalt shingles, metal and tiles make installing solar panels easier. If your room is made with other materials, installation may be more expensive. Part of what makes energy-efficient roofs is their ability to support solar panels.

4. Solar panels are dependent on sunlight

It's obvious that solar panels need sunlight to generate electricity. They won't produce electricity at night when you need it for light and they can be inefficient during storms and gloomy days. Your solar energy system needs batteries if you plan to fully depend on solar energy to power your home.

Batteries are one of the more expensive components of your system. Unlike solar panels, they do wear out and need careful maintenance to lengthen their lives. Comparing wind power vs. solar power, wind will keep generating electricity at night and during storms, as long as there is enough wind. Many people use both in residential systems.

Constellation Energy and Solar Energy

When weighing the pros and cons of solar energy for your home, there are additional options worth considering. Community solar projects are a great way to get the advantages of solar energy without buying and maintaining a system yourself.

If your home and roof won't support solar panels or if you don't have enough money to invest in one, community solar might be your answer. With this option, you agree to participating in a program that allows you receive credits for every kWh generated by the solar facility. You get a credit on your electricity bill proportional to your percentage of ownership in the project's energy.

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The Advantages and Disadvantages of Solar Energy

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Solar is a renewable energy source that can power your home, reduce your electric costs and maybe even earn you money back. Learn the pros & cons of solar energy here.

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Wind energy refers to any form of mechanical energy that is generated from wind or some other naturally occurring airflow. There are advantages and disadvantages to any type of energy source, and wind energy is no different. In this article, we'll review some of the top pros and cons of generating electricity from wind turbines.

Top pros and cons of wind energy

Wind energy is one of the most common types of renewable energy in the U.S. today, and also happens to be one of our fastest-growing sources of electricity. However, while there are a number of environmental benefits to using wind energy, there are some downsides. Here are a few of the top pros and cons:

Pros and cons of wind energy

Pros of wind energy

Cons of wind energy

Renewable & clean source of energy

Intermittent

Low operating costs

Noise and visual pollution

Efficient use of land space

Some adverse environmental impact

Wind energy is a job creator

Wind power is remote

On the pros side, wind is a clean, renewable energy source, and is one of the most cost-effective sources for electricity. On the cons side, wind turbines can be noisy and unappealing aesthetically, and can sometimes adversely impact the physical environment around them. Similar to solar power, wind power is also intermittent, meaning that turbines are reliant on weather and therefore aren't capable of generating electricity 24/7.

Below, we'll explore these pros and cons in further detail.

Advantages of wind energy

Wind energy is clean and renewable

Unlike coal, natural gas, or oil, generating electricity from wind doesn't result in greenhouse gas emissions. While there are some environmental considerations that come with building large wind farms, once operational, wind turbines themselves don't require burning any fossil fuels to operate.

Additionally, wind energy is completely renewable and will never run out. In opposition to traditional fossil fuels resources that replenish very slowly, wind naturally occurs in our atmosphere, and we don't have to worry about supply issues in the future.

Wind energy is a job creator

In terms of job creation, the wind energy sector is the fastest growing in the United States. Currently there are more than 100,000 workers in the field with the potential to support more than 600,000 in coming years.

Wind energy has low operating costs

As far as upfront costs go, wind farms or individual turbines can be expensive to install. However, once up and running, operating costs are relatively low; their fuel (wind) is free, and the turbines don't require too much maintenance over the course of their lifetime.

Wind energy is space-efficient

Cumulatively, wind farms can take up a lot of land space; however, the actual turbines and equipment don't use up a lot of real-estate. This means that land used for wind turbines can often also be used for other purposes, such as farming.

Disadvantages of wind energy

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Pros And Cons of Wind Energy | EnergySage

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There are many advantages and disadvantages to wind energy - from cost to land use and more.

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Pros and cons of fossil fuels & why can fossil fuels be good?

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What are the pros and cons of fossil fuels, why is fossil fuel good, and why don't we simply replace it with renewable energy?