Energy Basics: Sources of Energy

Where does energy come from?

In the U.S., most of our energy comes from nonrenewable sources.

Nonrenewable energy sources cannot be replenished in a short period of time.

Fossil fuels - coal, petroleum (oil, gas and propane), and natural gas - formed over millions of years from the remains of plants and animals. They are considered nonrenewable sources along with uranium, which is mined and converted to nuclear power.

We use these sources on a vast scale to generate electricity, heat our homes, fuel vehicles and manufacture all sorts of products.

Renewable sources of energy are replenishable relatively quickly.

Solar, wind, geothermal, biomass, hydropower, tidal power and fuel cells are sources of renewable energy that can be restored relatively quickly. Currently, renewable energy is used primarily to generate electricity, but its usage is growing.

Why isn't renewable energy used more widely?

There are several hurdles that make using renewable energy on a large scale a challenge:

• Intermittency: Wind power only generates electricity when the wind blows; solar power only works when the sun shines. However, we use energy around the clock.
• Efficiency: Getting sufficient power from renewable sources is challenging. Solar photovoltaic panels typically convert up to 18% of the sunlight that strikes the panels into electricity, and often less. Similarly, hydropower delivers large amounts of electricity, but electricity production must be balanced with water needs for irrigation and fish preservation.
• Geography: Renewable energy sources are generally better suited to different regions of the country and geographical features. In many cases, they require large areas of remote land and new transmission infrastructure to deliver power to population centers.
• Costs: Renewable energy sources often entail emerging technologies that compete economically against established commodities and delivery systems.

Solar Energy

For millions of years the sun's energy has powered life on Earth.

How does it work?

Solar energy comes from the sun. The sun's rays (solar radiation) can be used in two ways - as both a heat source, and as an energy source.

• Thermal (or heat) energy: Solar thermal collectors absorb the sun's heat energy to warm water or air for heating homes, offices, and other buildings.
• Electricity: Photovoltaic cells (PV) change sunlight directly into electricity. Photovoltaic systems can range from tiny amounts of power for watches and calculators to large amounts that can power hundreds of homes.

Advantages

• Solar energy is renewable.
• Solar energy systems do not produce air pollutants or carbon dioxide.
• Solar installations have minimal impact on the environment. Solar generation can be used as a locally distributed resource and help eliminate the need for additional electric system infrastructure.
• Solar electricity generation has the lowest ongoing operation and maintenance costs compared to other technologies.

Challenges

• The amount of sunlight reaching the Earth's surface is not constant. It varies depending on location, time of day, time of year, and weather conditions.
• Because the sun doesn't deliver that much energy to any one place at any one time, a large surface area is required to collect energy at a useful rate.
• While solar energy is technically free, it's expensive to make a lot of electricity using photovoltaics because initial installation costs are higher than conventional generation, and a lot of open land is needed.

Spotlight on Connecticut

Solar energy is becoming more affordable for homeowners. Many state and federal tax incentives are available. Leasing options and financing programs also make solar energy a more viable option.

Natural Gas

Approximately 85% of the natural gas consumed in the U.S. is produced domestically.

How does it work?

Like other fossil fuels, natural gas formed millions of years ago from organic matter trapped beneath thick layers of rock and transformed by heat and pressure. It is extracted by drilling deep wells and transported through pipelines.

Natural gas is used to generate electricity. It is also used widely to heat homes and to fuel stoves, water heaters, clothes dryers, and other household appliances. Increasingly, it is used as transportation fuel.

Advantages

• Natural gas is highly-efficient, economical, and reliable.
• When burned, it produces virtually no emissions of sulfur dioxide or particulate matter (found in acid rain) and far lower levels of greenhouse gases than oil or coal.
• Natural gas can also be stored for times of peak demand.

Challenges

• Many areas being explored for natural gas production are relatively pristine. Development could impact the area's environment, wildlife, and human populations.
• Natural gas is made up mostly of methane, a greenhouse gas. Natural gas can leak into the atmosphere from oil and gas wells, storage tanks, pipelines, and processing plants.
• Hydraulic fracturing, or "fracking", requires large amounts of water and if mismanaged, can contaminate surrounding areas.

Spotlight on Connecticut

Connecticut's Comprehensive Energy Strategy plans to expand access to natural gas to homes, businesses, and other facilities across the state.

What is LNG?

Liquefied natural gas, or LNG, is natural gas in liquid form. Since it occupies only a fraction (1/600) of the volume of natural gas, LNG is more economical to transport across large distances and can be stored in larger quantities.

Typically, LNG is warmed to produce natural gas for heating, cooking, electricity generation, and other industrial uses. LNG can be used in liquid form in natural gas vehicles, although it is more common for vehicles to use compressed natural gas.

Oil

In 2012, the U.S. relied on net imports for about 40% of the petroleum used.

How does it work?

The word petroleum means rock oil or oil from the Earth. Crude oil is a liquid usually found in underground areas called reservoirs that must be accessed by drilling wells - on land and offshore.

Crude oil is "refined" or broken down into components and reconfigured into new products such as gasoline, diesel or propane. These liquids are stored and then transported from tank to tank or through pipelines across the country.

Advantages

• Products from oil such as gasoline, diesel, and propane, help us do many things. They fuel airplanes, cars, and trucks; heat homes; and are used to make products like plastics, tires, computers, and medicines.
• Petroleum products can be stored and used on demand to fuel a wide variety of needs on a large scale.
• Crude oil is produced in 31 states and U.S. coastal waters.

Challenges

• Drilling, processing, transporting and using (burning) petroleum products can harm the environment through air and water pollution, including greenhouse gases, acid rain, ozone, and lead.
• Oil spills and leaks from storage tanks or pipelines can harm wildlife and cause water and ground contamination.

Spotlight on Connecticut

The state receives petroleum products at the coastal ports of New Haven, New London, and Bridgeport. Nearly one-half of Connecticut households use fuel oil or other distillates as the primary energy source for home heating.

Coal

Coal is used to produce about 39% of all the electricity generated in the U.S.

How does it work?

Coal is sedimentary rock that formed millions of years ago from dead plants transformed by heat and pressure under layers of water and dirt.

Surface mining or underground mining are the two ways to remove coal from the ground. It is then cleaned, processed, and transported.

Most coal consumed in the U.S. is used for electric power. Coal is also used as a basic energy source in many industries including the steel, cement, and paper industries.

Power plants make steam by burning coal. The steam turns turbines to generate electricity.

Advantages

• Currently, coal is an abundant fuel, mined in 25 states.
• It is relatively inexpensive to produce and convert to useful energy.

Challenges

• About 70% of coal mined in U.S. is surface mined, which alters the landscape. Water draining form valleys may contain pollutants that can harm aquatic life and wildlife.
• Underground mining emits methane, a strong greenhouse gas. Mines also can collapse and give miners black lung disease.
• Emissions from burning coal adversely affect the environment and human health. Emissions contribute to acid rain, smog, respiratory illnesses, and greenhouse gas emissions.

Spotlight on Connecticut

Coal was once a prominent source of energy in Connecticut, but very little coal is used now in the state.

Nuclear Energy

Nuclear power plants generate about one-fifth of U.S. electricity.

How does it work?

Nuclear energy is found in the core or nucleus of an atom. Uranium is the primary fuel used to start a nuclear reaction or fission. Fission splits atoms apart to form smaller atoms, which releases tremendous energy. The process repeats itself over and over again.

Most power plants, including nuclear plants, use heat to produce electricity. They rely on steam from heated water to spin large turbines, which generate electricity. Instead of burning fossil fuels to produce the steam, nuclear plants use heat given off during fission.

Advantages

• Although nonrenewable, Uranium is a common metal found in rocks worldwide.
• Nuclear power plants do not emit carbon dioxide or air pollution while operating.

Challenges

• Radioactive waste is the main environmental concern for nuclear power. It can remain radioactive and dangerous to human health for thousands of years.
• Nuclear power plants use large quantities of water for steam production and for cooling, which can affect fish and aquatic life.
• Nuclear plants are highly regulated and secured. However, an accident can have catastrophic human, environmental and economic impacts.

Spotlight on Connecticut

Connecticut embraced nuclear power early, developing facilities to manufacture components and to provide power for submarines, in addition to electric generating plants. Almost half of Connecticut's electricity generation comes from nuclear power.

Propane

Propane accounts for less than 2% of all energy used in the U.S.

How does it work?

Propane occurs naturally as a gas but becomes a liquid at higher pressure or lower temperatures. Liquefied gases, including propane, ethane and butane, are separated from natural gas at natural gas processing plants, or from crude oil at refineries.

Typically, propane is transported by pipeline to terminals across the country. Railroads, barges, trucks, and supertankers also ship propane to bulk distributors. Local propane dealers fill small tank trucks at bulk plants and deliver propane to large storage tanks for home use.

People use propane to heat homes and water, and for cooking food, drying clothes, and fueling gas fireplaces and grills. Only a small amount of propane is used for transportation.

Advantages

• Propane is highly portable.
• Propane is the most common source of energy in rural areas that do not have natural gas service.
• Propane produces much fewer emissions of carbon monoxide and hydrocarbons compared to gasoline engines.

Challenges

• Like all fossil fuels, propane emits greenhouse gases.

Spotlight on Connecticut

Propane is widely used in Connecticut for cooking and to fuel hot water heaters, fireplaces, and electricity generators, particularly in locations where a natural gas connection is unavailable.

Wind

The U.S. is home to one of the largest and fastest growing wind markets in the world.

How does it work?

For thousands of years, wind-powered machines have ground grain and pumped water. Wind is simply air in motion, caused by the uneven heating of the Earth's surface by the sun. Today, the movement of air (wind power) is used to turn an electrical generator to produce electricity.

Advantages

• Wind power is plentiful, replenishable, and can be harnessed almost anywhere.
• Wind power does not emit pollutants or greenhouse gases.
• Operational costs are relatively low.
• Although wind turbines can't be placed too close to each other, the land in between can be used for other purposes.
• Wind generation can be used as a locally-distributed resource and help eliminate the need for additional electric system infrastructure.

Challenges

• Wind fluctuates and varies depending on location, time of day, time of year, geography and weather conditions. Because it is not steady, it is not suited to meet base load energy demand.
• Wind turbines can be a threat to wildlife (e.g., birds, bats). Noise can be a nuisance to neighboring homes.
• Transporting wind-generated electricity from favorable sites to urban areas requires the siting and building of high-voltage transmission lines.
• The manufacturing and installation of wind turbines requires heavy upfront investments - both in commercial and residential applications, although prices are decreasing.

Spotlight on Connecticut

Installation of utility-scale wind turbines will require acceptance by localities due to high population densities throughout Connecticut.

Geothermal

Geothermal heat pumps can significantly reduce the fuel needed to heat and cool homes.

How does it work?

Geothermal energy uses heat from the Earth. Sources of heat range from shallow ground to hot water and rock a few miles beneath the Earth's surface, and even deeper to the extremely high temperatures of molten rock called magma.

We use geothermal energy in three main ways:

• By transferring heat from or to the ground through a series of looped pipes buried underground to heat or cool a building.
• By drilling wells into the Earth and piping steam or hot water to turn a turbine and generate electricity.
• By drilling wells into deep reservoirs and using the hot water to produce heat directly.

Advantages

• Heat is produced continuously inside the Earth; it's reliable and renewable.
• The upper ten feet of the Earth's surface maintains a nearly constant temperature between 50° and 60°F. Geothermal heat pumps can tap into this resource to heat and cool buildings almost everywhere.
• Geothermal energy is safe, clean, and reliable.
• Geothermal power plants do not generate waste or greenhouse gases.
• Geothermal power plants only require a small environmental footprint for development.

Challenges

• Geothermal power is not easy to transport like oil or wood; it must be used near where it is extracted.
• The costs to install looped pipes that transfer geothermal energy to building heating and cooling systems vary according to specific site characteristics.
• In the U.S., most geothermal reservoirs of hot water are located in the western states, Alaska, and Hawaii.
• Geothermal power plants are costly to install.

Spotlight on Connecticut

Geothermal heat pumps are primarily used in Connecticut to heat and cool buildings and heat hot water.

Biomass Energy

Burning municipal solid waste reduces the volume of waste by about 87%.

How does it work?

Imagine sitting by a campfire. You are actually watching biomass energy in action.

Biomass is organic material that comes from plants and animals. When it is burned, the chemical energy of the materials is released as heat. Wood chips, bark, sawdust, leftover crops, and even trash, tires, and manure can all be used to make electricity.

Biomass also can be converted to other useable forms of energy like electricity and methane gas, or transportation fuels like ethanol and biodiesel.

Advantages

• The major advantage of burning waste to generate electricity is that it reduces the need for landfills and the fossil fuels that would otherwise be used.
• Eliminating the potential release of methane by burning biomass is a net benefit because methane is a stronger greenhouse gas than CO2.
• Compared to petroleum diesel, biodiesel combustion produces less sulfur oxides, particulate matter, and carbon monoxide.

Challenges

• Wood smoke contains harmful pollutants like carbon monoxide and particulate matter.
• Like power plants that burn coal, waste-to-energy plants produce air pollution when the fuel is burned to produce steam or electricity.
• Large areas of natural vegetation and forests have been cut down to grow sugar cane for ethanol and soybeans and palm-oil trees to make biodiesel.

Spotlight on Connecticut

Trash-to-energy plants in Connecticut process about 2 million tons of waste and generate about 630 million kWh per year of electricity - more than any other state.

Hydropower

Hydropower is the largest renewable energy source for electricity generation in the U.S.

How does it work?

Go with the flow. Hydropower, one of the oldest sources of energy, captures energy from moving water.

The amount of available energy in moving water is determined by its flow or fall. Water turns the blades of a turbine to produce electricity.

A typical hydropower plant has three parts: an electric plant where the electricity is produced; a dam that can be opened or closed to control water flow; and a reservoir where water can be stored.

Hydroelectric power provides almost one-fifth of the world's electricity.

Advantages

• Hydropower is a clean energy source that is renewable through snow and rainfall.
• Hydropower is the cheapest way to generate electricity today.

Challenges

• Hydroelectric dams can obstruct the migration of fish and change water temperature, chemistry, and flow, which can alter ecology and negatively impact plants and animals.
• Greenhouse gases, carbon dioxide and methane can form in reservoirs and be emitted to the atmosphere.
• Transporting hydroelectric power from favorable sites to urban areas requires the siting and building of high-voltage transmission lines.

Spotlight on Connecticut

There are 13 hydroelectric power plants in Connecticut with a total capacity of about 145 MW.

Tidal Power

There are only a few sites in the U.S. where tidal energy could be produced economically.

How does it work?

The tides of the sea go in and out twice a day, responding to the gravitational pull of the moon and sun, and rotation of the Earth. They can drive turbines too.

Tidal turbines are basically wind turbines in the water that can be located anywhere there is strong tidal flow. Some turbines are placed underwater and others ride on top of waves.

Currently, there aren't any tidal plants in the U.S.

Advantages

• Tidal energy is naturally occurring and renewable.
• Tidal energy is more predictable than wind energy and solar power.

Challenges

• A large enough tidal range - 10 feet - is needed to produce tidal energy economically.
• Tidal turbines are heavier and more expensive to build than wind turbines but they capture more energy.
• A tidal station can be detrimental to plants and animals in neighboring estuaries.
• Tidal barrages (dam-like structures) can change the tidal level in basins and increase turbidity (the amount of matter in suspension in the water).
• Tidal barrages can also affect navigation and recreation.

Spotlight on Connecticut

The tidal range in Connecticut is not great enough to economically produce energy at this time.

Fuel Cells

Fuel cells are a promising technology for use as a source of heat and electricity in buildings, and as an electrical power source for vehicles.

How does it work?

Fuel cells generate electricity and heat from a chemical reaction in which oxygen and hydrogen combine to form water.

Fuel cells come in many varieties but all consist of an anode, a cathode and an electrolyte that allow charges to move between the two sides of the fuel cell.

Emerging markets for fuel cells are transportation, portable power for handheld electronics (laptops, cell phones, heating aids), and stationary power. Fuel cells can provide a clean, reliable source of on-site power to hospitals, banks, airports, military bases, schools, and homes.

Advantages

• Fuel cells generate electricity with very little pollution and are very efficient.
• Small fuel cells can power electric cars. Large fuel cells can provide electricity in remote places with no power lines.
• Hydrogen is also the most plentiful gas in the universe.

Challenges

• Hydrogen fuel cells are very expensive to build; large plants will not be built for a while.
• Few hydrogen refueling stations in the U.S. make it hard for those with hydrogen vehicles to refuel.

Spotlight on Connecticut

Since the 1950s, Connecticut has been a leader and innovator in fuel cell research and development, pioneering applications for spacecraft, submarines, stationary power, and transportation. Fuels cells are considered a viable renewable energy option in Connecticut.