What key definitions/terms apply?

• Various definitions aid in understanding renewable and alternative energy.

Biofuels: Liquid fuels and blending parts made from biomass feedstocks, utilized mainly for transportation.

Biochar: A type of charcoal made by burning biomass (organic material) in an environment that is low oxygen. This process changes the carbon in the biomass to a kind that withstands decay.

Biogenic: Made by biological actions of living organisms.

Biomass gas: A medium British thermal unit (Btu) gas with methane and carbon dioxide. It arises from microorganisms acting on organic matter such as a landfill.

Biomass waste: Organic non-fossil matter that is a byproduct or a rejected product. Biomass waste includes community solid waste from biogenic origins, gas from landfills, sludge waste, byproducts from agricultural crops, straw, and further biomass solids, liquids, and gases. It does not include wood and wood-derived fuels, biofuels feedstock, biodiesel, and ethanol fuel.

Cells: Un-enclosed semi-conductor parts of the module that turn solar energy into electricity.

Conventional hydroelectric plant: A plant in which all the power is made from natural streamflow as managed by accessible storage.

Green power: Electricity that is produced from renewable energy sources.

Green pricing: It signifies a solution to the different problems related to regulatory cost of the nonmarket renewables’ benefits. Green pricing programs help electricity consumers show their desire to buy renewable energy development through payments on their utility bills each month.

Heat pump (geothermal): A heat pump in which the refrigerant trades heat with a fluid flowing through the ground or ground water. The fluid is held in various loop (pipe) configurations based on ground temperature and available ground area. Loops can be installed in the ground horizontally or vertically or immersed in a water body.

Net metering: A metering and billing arrangement made to compensate distributed energy generation system owners for any generation that is sent out to the utility grid.

Photovoltaic cell (PVC): An electronic device with layers of semiconductor matter created to develop layers of materials with various electronic traits and contacts that can turn incident light into electricity.

Photovoltaic module: A meeting of connected photovoltaic cells that bring a chosen level of voltage and current.

Solar thermal panels: A system that concentrates thermal energy coming from the sun through solar collector panels. The panels usually have large, sun-oriented boxes with clear covers, with water tubes of air baffles under a black-colored heat absorbent panel. The energy is generally used for space heating and water heating.

Water turbine: A turbine that utilizes water pressure to turn its blades. The main kinds of water turbines are the Pelton wheel, for high pressure, the Francis turbine, for low to medium pressure, and the Kaplan for a large span of pressure. These are mainly used to power electric generators.

Wind power plant: A collection of wind turbines connected to a utility system through an arrangement of transformers, distribution lines, and typically one substation.

Wind turbine: Wind energy conversion apparatus that makes electricity. It usually has three blades that turn about a horizontal axis and that is positioned up-wind from the supporting tower.

Types of renewable energy

• The main kinds of renewable energy sources are biomass, geothermal, hydropower, solar, and wind.
• Businesses can obtain renewable energy in three different ways.

Renewable energy is from sources that naturally replenish but are flow limited. Renewable resources are essentially inexhaustible in time. But they are restricted in the quantity of energy that is available per that unit of time.

The main kinds of renewable energy sources include:

• Biomass
• Geothermal
• Hydropower
• Solar
• Wind

Wood was the source of almost all the energy needs of the United States up until the mid-1800s. From the late 1800s until now, fossil fuels, which include coal, petroleum, and natural gas, have been the main energy sources. Out of all the renewable energy resources, hydropower and wood were the most used until the 1990s. Since that time, the quantities of U.S. energy use from biofuels, geothermal, solar, and wind energy have grown.

In 2020, renewable energy supplied roughly 11.59 quadrillion British thermal units (Btu)—equal to 12 percent of the entire U.S. energy use. The electric power sector was responsible for about 60 percent of the entire U.S. renewable energy consumption in 2020. About 20 percent of the entire U.S. electricity generation was due to renewable energy sources.

The Public Utility Regulatory Policies Act (PURPA) of 1978 is one portion of the National Energy Act. PURPA has measures set up to positively influence energy conservation, more efficient resource use, and fair rates. Chief among these were proposed retail rate reforms and alternative incentives for the development of electricity by cogenerators and renewable resource users.

Businesses can obtain renewable energy in three different ways:

1. Owning renewable energy systems and using the energy those systems generate,
2. Buying renewable power from various third-party-owned systems, or
3. Buying unbundled renewable energy certificates (RECs).

Regardless, an organization must own and retire the RECs connected to the power in order to make renewable energy claims. Renewable energy generation can take place onsite (e.g., solar panels on rooftops, micro-wind turbines) or offsite (e.g., utility-scale renewables, community solar). A company’s renewable energy portfolio may have one or a mixture of these procurement options to hit a larger goal.

Types of alternative energy

• Nuclear energy and natural gas are two examples of alternative energy sources.

There are further alternatives to conventional energy that are not necessarily renewable. Even though these are alternative energy instead of renewable energy, they use energy more efficiently than historic technologies. In doing this, they assist in making energy supplies that are already present last longer. They provide more time before stored fossil and atomic fuels run out. Nuclear energy and natural gas are two such examples of alternative energy sources.

Nuclear energy

Nuclear energy is carbon-free. A nuclear power plant does not release any carbon dioxide, or any other types of greenhouse gases. It is not renewable because nuclear reactors use uranium, and if uranium gets used up, humans cannot get it back.

Natural gas

Most of the natural gas in the United States is classified as a fossil fuel since it is created from sources developed over millions of years through heat and pressure applied on organic matter. The majority of natural gas is taken from wells or removed together with crude oil generation. Additionally, natural gas can be excavated from subsurface porous rock reservoirs through mining methods like hydraulic fracturing. Renewable natural gas or biogas is an alternative energy source and a renewable source, dissimilar to nuclear energy or conventional natural gas.

What are the benefits of each type of renewable energy?

• Renewable energy can lower greenhouse gas emissions, diversify energy supply, and encourage economic development and job creation.

Environmental and financial benefits of using renewable energy include the following:

• Producing energy that does not emit greenhouse gas emissions from fossil fuels and lowers different kinds of air pollution.
• Diversifying energy supply and lowering dependence on fuels from abroad.
  • Fossil fuels and renewable energy sources differ in that renewable energy can be made in a large range of areas. Fossil fuels can only be in particular locations and are one of the United States’ main imports from other countries, particularly the Middle East.
  • Other countries can adjust the price of their fossil fuels at any given moment, leaving the U.S. and its people at risk of price increases that can really damage the economy.
• Crafting economic development and jobs in production, installation, and more.
  • Job creation for renewable energy is usually in rural or economically depressed locations, and further assists in sustaining local economies through capital investments, taxes, and other associated economic actions.
  • The development of massive renewable energy plans can also give rise to other infrastructure investments that supply added benefits to local communities, like roads and communication infrastructure.

What are the drawbacks of renewable energy?

• Renewable energy can face high costs, poor utility rate structures, lack of interconnection standards, barriers in environmental pretermitting, and lack of transmission.

High cost

• Cost competitiveness is a clear hurdle for renewable energy installations. The consumer price of self-creating power through nearby windmills or solar panels places these options into the luxury and higher-class product bracket. Some tax credits and help are available to cover a portion of the buying cost, but the price of these smaller systems is a constraint even with those. Zoning and contract restrictions could add to the possible costs of installing renewable local energy production equipment.
• In a lot of situations, hurdles to growing renewable energy are regulatory and thus in a state’s control.

Utility rate structures

• Poor utility rate structures have been a hurdle to greater use of renewable energy technologies. Unless cautiously watched to help the production of distributed generation, rate structures can raise the cost of renewables (for example through stand-by rates, insufficient net metering) or they can totally bar connection to the electrical grid.

Lack of interconnection standards

• The lack of standard interconnection rules, or consistent procedures and requirements for connecting renewable energy systems to the electric utility’s grid, can cause it to be challenging or impossible for renewable systems to connect.
• Often, transmission lines and the connections among them are far too tiny for the quantity of new renewable power that corporations want to add. The U.S. Department of Energy predicts that roughly 2,100 miles of new line will be required to hit the goal of serving 20 percent of the nation’s energy users with access to renewables.

Barriers in environmental permitting

• Huge renewable energy technologies are prone to the same required environmental permits as main industrial facilities. Renewable energy production using new technologies can have issues with permitting until permitting officers are knowledgeable on the environmental effects of the production.

Lack of transmission

• Often, renewable resources are found in remote locations that do not have ready or profitable access to transmission. States that have not set transparent utility regulations that allow investments in transmission to be refunded (i.e., cost recovery), nor organized planning and permitting procedures, slow the production of utility–sized renewable projects in the area.

Solar

• Solar photovoltaics are commonly used for electricity production.
• The availability and strength of solar radiation differs by time of day and area.

More energy from the sun lands on Earth in a single hour than is used by the entire human population in a year. Different technologies change sunlight to usable energy for all kinds of buildings. The most used types of solar technologies for businesses are solar photovoltaics used for electricity production, passive solar design meant for space heating and cooling of a building, and solar water heating.

Businesses and industry implement solar technologies to expand their energy sources, gain better efficiency, and lower overall costs. Energy developers and utilities utilize solar photovoltaic (PV) technologies to make electricity on a large scale to power parts of cities and small towns.

The availability and strength of solar radiation differs by time of day and area. Typically, the strength of solar radiation at any area is the highest when the sun is at its tallest apparent location in the sky, which is at solar noon and on clear, cloudless days.

Latitude, climate, and weather patterns are main aspects that affect the quantity of solar radiation obtained during a particular amount of time. Lower latitude locations and climates found in arid areas usually get larger amounts of solar radiation than other areas. Clouds, dust, volcanic ash, and atmospheric pollution affect solar radiation surface levels. Buildings, trees, and mountains can shade a location at various times of the day in various months of the year. Seasonal differences in solar resources grow as the distance from earth’s equator increases.

Where solar energy is used

Solar radiation levels are crucial for the performance of solar energy systems. The availability of financial incentives for solar energy are also key aspects that impact the location where solar energy systems are installed. Net metering has been very important in positively influencing the installation of PV systems on businesses.

Wind

• Wind is a kind of solar energy resulting from a mixture of three simultaneous events.
• Most wind turbines fall under two simple kinds.

Wind turbines work based on a basic idea. Rather than using electricity to create wind—like a fan does—wind turbines utilize wind to produce electricity. Wind moves the blades of a turbine around a rotor, which turn a generator, which then produces electricity.

Wind is a kind of solar energy resulting from a mixture of three simultaneous events:

1. The sun unequally heats the atmosphere;
2. There are asymmetries with the surface of the Earth; and
3. The Earth rotates.

Wind flow patterns and speeds differ vastly across the United States. They are altered by bodies of water, plants, and terrain differences. Humans utilize this wind flow, for many reasons: sailing a boat, flying a kite, and even creating electricity.

Wind energy and wind power describe the operation by which the wind is used to mechanical power. This mechanical power can be used for certain processes like crushing grain or pumping water or a generator can turn this mechanical power into electricity.

A wind turbine converts wind energy into electricity using force from the rotor blades, which function similar to an airplane wing. When wind moves across the blade, air pressure on one side lowers. The variation in air pressure across the two blade sides produces lift and drag. The lift force is greater than the drag and this makes the rotor spin. The rotor ties to the generator, either directly or through a shaft and a series of gears that increase the rotation speed and make a smaller generator possible. This conversion of force is what makes electricity.

Most wind turbines fall under two simple kinds:

1. Horizontal-axis wind turbines- These are what many people imagine when picturing wind turbines. Typically, they have three blades and run upwind, with the turbine moving at the top of the tower so the blades face toward the wind.
2. Vertical-axis wind turbines- These turbines don’t need to be modified to point into the wind to run.

Hydro

• Hydropower depends on the water cycle.
• Seasonal differences in precipitation and long-term variations in precipitation patterns have big influences on the availability of hydropower generation.

In 2020, hydroelectricity was responsible for roughly 7.3 percent of the entire U.S. utility-scale electricity production and 37 percent of the entire utility-scale renewable electricity production. Hydroelectricity’s share of U.S. electricity generation altogether has lessened over time, primarily due to growth of other sources of electricity generation.

Hydropower depends on the water cycle. Understanding the water cycle is critical to comprehending hydropower. There are three steps in the water cycle:

1. Solar energy heats water on the surface of rivers, lakes, and oceans, this makes the water evaporate.
2. Water vapor condenses into clouds and drops as rain and snow.
3. Rain and snow gather in streams and rivers, which unload into oceans and lakes, where it then evaporates and starts the cycle over.

The quantity of precipitation that goes into rivers and streams in an area decides the quantity of water available for making hydropower. Seasonal differences in precipitation and long-term variations in precipitation patterns, like droughts, can have big influences on the availability of hydropower generation.

Since the source of hydroelectric power is water, these power plants are typically found on or near a source of water. The amount of water flow and the elevation difference or fall from one point to another decides the quantity of available energy in flowing water. Overall, the higher the water flow and the greater the fall, the more electricity a hydropower plant can generate.

At hydropower plants, water moves through a pipe then pushes up against and rotates blades in a turbine to turn a generator to make electricity.

Biomass

• Biomass has stored chemical energy that comes from the sun.
• Biomass sources for energy include wood and wood processing wastes, farming crops and waste matter, biogenic matter in community solid waste, and sewage.

Biomass is renewable organic matter that originates from plants and animals. Biomass was the greatest source of U.S. energy use until the mid-1800s. It remains a crucial fuel in many developing countries, particularly for cooking and heating. Biomass fuel use for transportation and electricity production is growing in many developed countries as a way of steering clear of carbon dioxide emissions from fossil fuels. In 2020, biomass supplied almost 5 quadrillion British thermal units (Btu) and roughly 5 percent of the entire main energy use within the United States.

Biomass has stored chemical energy that comes from the sun. Plants make biomass through a process called photosynthesis. Biomass can be ignited directly for heat or changed into renewable liquid and gaseous fuels through different methods.

Biomass sources for energy include the following:

• Wood and wood processing wastes—firewood, pellets, wood chips, lumber and furniture mill sawdust and waste, and black liquor from pulp and paper mills
• Farming crops and waste matter—corn, soybeans, sugar cane, switchgrass, woody plants, algae, and food processing residues
• Biogenic matter in community solid waste—paper, cotton, wool goods, and food, yard, and wood wastes
• Animal dung and human sewage

Biomass is turned into energy through different methods, including the following:

• Direct burning to make heat
• Thermochemical transformation to create solid, gaseous, and liquid fuels
• Chemical transformation to create liquid fuels
• Biological transformation to create liquid and gaseous fuels

Geothermal

• Three kinds of technologies utilize heat from the Earth: ground source heat pumps, direct-use geothermal, and deep and enhanced geothermal systems.
• Commercial uses of geothermal energy include food dehydration, gold excavating, and dairy pasteurizing.

Geothermal technology captures Earth’s heat. Only several feet below the surface, the Earth keeps a near-constant temperature, unlike the summer and winter temperature extremes of the air above ground. Even deeper below the surface, the temperature grows at an average rate of roughly 1°F for every 70 feet gained in depth. In certain areas, tectonic and volcanic activity can deliver greater temperatures and patches of superheated water way closer to the surface.

Three prominent kinds of technologies utilize Earth as a heat source:

• Ground source heat pumps,
• Direct-use geothermal, and
• Deep and enhanced geothermal systems.

Ground source heat pumps

A ground source heat pump uses the naturally existing variation between the air temperature above-ground and the soil temperature below the surface to transport heat to aid end uses such as space heating, air conditioning, and water heating. A ground source system has a heat pump tied to a sequence of buried pipes. The pipes can be installed in horizontal trenches just under the surface of the ground or in vertical boreholes that go a few hundred feet underground. The heat pump continually moves a heat-conveying fluid, occasionally water, through the pipes to transfer heat from one spot to another.

Direct-use geothermal

Direct-use geothermal systems utilize groundwater that is warmed by naturally occurring geological actions under the Earth’s surface. This water can reach temperatures as great as 200°F. Bodies of hot groundwater can be in numerous regions with volcanic or tectonic processes. In an area like Yellowstone National Park, groundwater reservoirs can go up to the surface, making geysers and hot springs. Hot water may be pumped from the surface or underground for a vast array of helpful applications.

Deep and enhanced geothermal systems

Deep geothermal systems utilize steam from way under the Earth’s surface for applications that need temperatures of a few hundred degrees Fahrenheit. These systems usually insert water into the ground through a single well and deliver water or steam to the surface through a different well. Other adaptations can gather steam right from underground. Dissimilar to ground source heat pumps or direct-use geothermal systems, deep geothermal systems can include drilling a mile or further under the Earth’s surface. At these great depths, high pressure holds the water in a liquid state despite temperatures reaching a few hundred degrees Fahrenheit.

Ground source heat pumps and direct-use geothermal technologies provide heating and cooling uses. Deep and enhanced geothermal technologies usually use a significantly deeper and greater temperature as a geothermal resource to make electricity.

Commercial uses of geothermal energy include the following:

• Food dehydration,
• Gold excavating, and
• Dairy pasteurizing.

Photovoltaics

• PV cell efficiency differs by the kind of semiconductor material and technology used.
• PV cells and modules make the greatest quantity of electricity when they face the sun directly.

A photovoltaic (PV) cell, or solar cell, is a nonmechanical device that changes sunlight into electricity. A handful of PV cells can turn artificial light into electricity.

PV cell efficiency differs by the kind of semiconductor material and technology used. The efficiency of commercially accessible PV modules averaged lower than 10 percent in the mid-1980s. It grew to about 15 percent by 2015. It is now nearing 20 percent for state-of-the art modules. Different kinds of experimental PV cells and ones for niche markets, for example space satellites, have an efficiency of almost 50 percent.

How photovoltaic systems operate

The PV cell is the starting point of a PV system. Individual cells can differ in size from roughly 0.5 inches to roughly 4 inches across. But one cell can only make 1 or 2 Watts, which is just enough electricity for minimal applications, such as powering calculators or watches.

PV cells are electrically bound in a weather-tight PV module or panel. PV modules differ in size and in the quantity of electricity they can make. The capacity of PV module electricity generating grows as the number of cells in the module or in the module surface area increases.

Photovoltaic cells produce a type of electricity called direct current (DC). This DC electricity can power up batteries that then charge devices that use direct current electricity. Almost all electricity is provided as alternating current (AC) in systems of electricity transmission and distribution. Devices named inverters are used to change DC electricity to AC electricity.

PV cells and modules make the greatest quantity of electricity when they face the sun directly. PV modules and arrays can utilize different tracking systems that turn the modules to always face the sun, but these are costly. The majority of PV systems have modules in a fixed position. The modules face directly south in the northern hemisphere and north in the southern hemisphere. They are put at an angle that maximizes system performance.

Concentrating

• CSP technologies may be used to make electricity by turning energy from the sun into power for a turbine.
• CSP technology uses three technological approaches: trough systems, power tower systems, and dish/engine systems.

Concentrating solar-thermal power (CSP) technologies may be used to make electricity by turning energy from the sun into power for a turbine. The same simple technologies can also be used to bring heat to a wide array of industrial applications, such as water desalination, better oil recovery, food processing, chemical manufacturing, and mineral processing.

CSP plants make electric power by using mirrors to focus energy from the sun and change it into high-temperature heat. That high-temperature heat is then directed through a conventional generator. The plants have two parts:

• One that gathers solar energy and changes it to heat, and
• Another that changes the heat to electricity.

CSP technology uses three technological approaches:

• Trough systems,
• Power tower systems, and
• Dish/engine systems.

Trough systems use huge, U-shaped focusing mirrors that have oil-filled pipes running along their center. The mirrors are tilted toward the direction of the sun. They focus sunlight on the pipes to heat the inside oil to as high as 750°F. Then, the hot oil is used to boil water. This produces steam to power conventional steam turbines and generators.

Power tower systems use many big, flat mirrors to track the location of the sun and focus its rays onto a receiver. The receiver sits on a tall tower, here concentrated sunlight heats a fluid as hot as 1,050°F. The hot fluid can be used right away to create steam for electricity generation or stored for use later. So, electricity can be made during periods of high need on cloudy days or even a few hours after sunset.

Dish/engine systems use mirrored dishes to focus sunlight onto a receiver. The receiver is fixed at the focal point of the dish. To get the greatest quantity of solar energy, the dish assembly tracks the sun. The receiver is combined with a high-efficiency combustion engine. The engine has narrow tubes with hydrogen or helium gas that go along the exterior of the engine’s four piston cylinders and open into those cylinders. As sunlight falls on the receiver, it heats the gas in the tubes to great temperatures. This results in hot gas expanding in the cylinders. The expanding gas drives the pistons, which rotate a crankshaft, which then drives an electric generator. The receiver, engine, and generator are one integrated assembly fixed at the focus of the mirrored dish.

System integration

• Solar systems integration involves creating technologies and tools that help bring solar energy onto the electricity grid, while conserving grid reliability, security, and effectiveness.
• The electrical grid is divided into two different systems: transmission and distribution.

Solar systems integration involves creating technologies and tools that help bring solar energy onto the electricity grid, while conserving grid reliability, security, and effectiveness at the same time.

The electrical grid

For the majority of the past century, electrical grids had large-scale, centralized energy creation located far from purchasers. Modern electrical grids are a lot more complicated. Alongside large utility-scale plants, modern grids also involve different energy sources such as solar and wind, energy storage systems, power electronic devices such as inverters, and small-scale energy production systems such as rooftop installations and microgrids. These smaller-scale and scattered energy sources are typically called distributed energy resources (DER).

The electrical grid is divided into two different systems: transmission and distribution. The transmission grid is the lattice of high-voltage power lines that bring electricity from centralized sources such as big power plants. These high voltages allow power to be carried far stretches without great loss. The distribution grid refers to low-voltage lines that end up going to businesses. Substations and transformers change the power from high to low voltage. Historically, electricity only had to flow one direction through these systems: from the central generation source to the purchaser. But systems such as rooftop solar now need the grid to juggle two-way electricity flow, since these systems can inject the surplus power that they produce back into the grid.

Power electronics

Growing solar and DER on the electrical grid means merging additional power electronic devices, which change energy from one type to another. This may include changing between high and low voltage, monitoring the quantity of power flow, or changing between direct current (DC) and alternating current (AC) electricity, based on where the electricity is going and its use. The inverter is a kind of power electronic device that is very critical for solar energy integration. Inverters change DC electricity, what a solar panel produces, to AC electricity, what the electrical grid utilizes.

Solar plus storage

Because solar energy can only be produced when the sun is shining, the opportunity to store solar energy for future use is crucial. It supports the fine balance between electricity production and consumer demand.

Grid resilience and reliability

The electrical grid needs to consistently supply power. It’s critical for utilities and to have real-time data on the amount of electricity solar systems are generating. Growing quantities of solar and DER on the grid result in opportunities and difficulties for grid consistency. Intricate modern grids with a mixture of traditional generation and DER can make replying to atypical scenarios such as storms or blackouts more challenging. But power electronics have the possibility to gather real-time data on the grid and aid in maintaining grid operations.

Conventional

• Conventional hydroelectric facilities include run-of-the-river systems and storage systems.

While many individuals might associate hydropower with the Hoover Dam—a large facility mobilizing the power of an entire river —hydropower facilities come in many sizes. Some may be quite big. But they can be very small too, taking advantage of flowing water in community water facilities or irrigation ditches. They can also be damless with diversions or run-of-river spaces that channel a portion of a stream through a powerhouse before the water reunites with the central river. Regardless of the technique, hydropower is a lot simpler to get and more extensively used than the majority of people think. All except two states, Delaware and Mississippi, use hydropower.

Conventional hydroelectric facilities include the following:

• Run-of-the-river systems, where the river’s current puts pressure on a turbine. The facilities can have a dam in the water course to redirect water flow to turbines.
• Storage systems, where water builds in reservoirs made by dams on streams and rivers and is let out through hydro turbines as necessary to produce electricity. The majority of U.S. hydropower operations have dams and storage reservoirs.

The idea is to develop a dam on a big river that has a substantial drop in elevation. The dam keeps large amounts of water behind it in the reservoir. The water intake is close to the bottom of the dam wall. Gravity makes it fall through the gate in the dam. At the end of the gate there is a turbine propeller. This propeller is moved by the flowing water. The turbine’s shaft goes up into the generator, which makes the power. Power lines are tied to the generator that brings electricity to a business. The water goes on past the propeller into the river beyond the dam.

Other hydro

• A two-way tidal power system produces electricity from the arriving and outgoing tides.
• One way to channel wave energy is to focus waves into a thin channel to expand their size and power and to turn the turbines that produce electricity.

Tidal

The United States has no commercially functioning tidal energy power plants, but there are a few demonstration projects that are in different developmental stages. One kind of tidal energy system uses a structure comparable to a dam called a barrage. The barrage is placed across an inlet of a coastal bay or lagoon that makes a tidal basin. Sluice gates on the barrage control water levels and flow rates. The gates help the tidal basin fill during high tides and drain through a turbine system during the outgoing ebb tide. A two-way tidal power system produces electricity from the arriving and outgoing tides. Tidal turbines are like wind turbines in that they have various blades that move a rotor to charge a generator. They can be positioned on the sea floor where the tidal flow is powerful. Since water is roughly 800 times denser than air, tidal turbines need to be heavier than wind turbines. Tidal turbines are more costly to develop than wind turbines but can obtain greater energy with the exact same size blades.

Waves

Waves develop as wind sweeps over the surface of open water. Ocean waves hold large amounts of energy. The speculative annual energy potential of waves off coastal U.S. is thought to be as great as 2.64 trillion kilowatt-hours, or equal to roughly 64 percent of the total U.S. electricity production in the year 2019. Many various techniques and technologies for obtaining and converting wave energy to electricity are under way. These techniques include putting devices on or just under the surface of the water and securing devices to the ocean floor.

One way to channel wave energy is to focus waves into a thin channel to expand their size and power and to turn the turbines that produce electricity. Additionally, waves can be channeled into a reservoir where the water moves to a turbine at a smaller elevation, like the way a hydropower dam works.

Nuclear

• Nuclear energy is when atoms split apart and make electricity.
• Nuclear reactors do not create air pollution or carbon dioxide while running, unlike power plants fired by fossil fuels.

Nuclear energy is when atoms split apart and make electricity. All power plants change heat into electricity with the help of steam. At nuclear power plants, the heat used to create steam is made during fission, which is when atoms break apart. The atoms release heat during this split. It is called a chain reaction, when the method is repeated. In a nuclear power plant, uranium is used in the process of fission.

The heat produced from fission boils water and makes steam to rotate a turbine. As the turbine turns, the generator rotates, and its magnetic field makes electricity. Electricity can then be brought to a business for energy use.

Nuclear energy accounts for roughly 20 percent of the electricity in the United States. So, one out of every five homes in the nation can switch on their lights because of a minuscule atom! The U.S. Nuclear Regulatory Commission (NRC), monitors and controls nuclear power plants. They ensure that they are safe for workers and those who live close by, and for the overall environment.

Nuclear reactors do not create air pollution or carbon dioxide while running, unlike power plants fired by fossil fuels. Although, the methods for excavating and refining uranium ore and creating reactor fuel all need big energy quantities. Also, nuclear power plants have great quantities of metal and concrete, which need a lot of energy to produce. If fossil fuels are used for excavating and refining uranium ore, or if fossil fuels are used when making the nuclear power plant, then emissions from igniting those fuels could be linked to the electricity that nuclear power plants create.

A main environmental issue connected to nuclear power is the production of radioactive wastes such as uranium mill tailings and used reactor fuel. These materials can stay radioactive and a human health hazard for thousands of years. Radioactive wastes are subject to unique rules that regulate their handling, transportation, storage, and disposal to safeguard the health of humans and the surrounding environment.

Natural gas

• Natural gas is a gaseous combination of hydrocarbons.
• Biogas can come from landfills, livestock functions, wastewater treatment plants, and even crop residue and woody biomass.

Natural gas is odorless. It is a gaseous combination of hydrocarbons—mostly comprised of methane. Natural gas accounts for roughly 30 percent of all the energy consumed in the nation. Nearly 40 percent of the fuel goes to electric power generation. The rest is divided among residential and commercial purposes, like heating and cooking, and industrial actions.

Most natural gas in the United States is classified as a fossil fuel because it originates from sources developed over millions of years through intense heat and pressure applied on organic matter. However, renewable natural gas (RNG), also called biomethane, is a pipeline-quality vehicle fuel made from organic matter—like landfill and livestock waste—through anaerobic (existing without oxygen) digestion. RNG can be considered an advanced biofuel under the Renewable Fuel Standard.

Because RNG is chemically interchangeable to fossil-attained conventional natural gas, it can use the already present natural gas distribution system. It needs to be compressed or liquefied for vehicle use. Natural gas made by renewable techniques gives added benefits. RNG is basically biogas—the gaseous result of the breakdown of organic material—that has been refined to purity standards. Obtaining biogas from landfills and livestock functions lowers emissions by staving off atmospheric methane release. Also, making biogas through anaerobic digestion lowers unpleasant odors. It makes nutrient-rich liquid fertilizer.

Biogas can come from different areas including the following:

1. Landfills
   • Landfills are selected areas for getting rid of waste gathered from residential, industrial, and commercial structures. Landfills are the third-greatest source of human-associated methane emissions in the nation.
2. Livestock functions
   • Biogas recovery systems happening at livestock functions can be used to make renewable natural gas. Animal manure is gathered and sent to an anaerobic digester (microorganisms break down organic waste) to fortify and enhance methane generation. The product, biogas, can be prepared into RNG.
3. Wastewater treatment
   • Biogas can be made during the digestion of solids taken out during wastewater treatment activities. Energy made at U.S. wastewater treatment plants could possibility meet 12 percent of the U.S. electricity need.
4. Other biogas sources
   • Other sources of biogas include organic waste, such as food producers and wholesalers, supermarkets, restaurants, hospitals, and educational establishments.
   • Biogas can also be made from lignocellulosic matter, such as crop residues, woody biomass, and energy crops. This is underway in Europe, with restricted applications in the United States.

Reduced environmental impacts

• Hydropower, solar, and wind do not emit pollutants into the air.
• Hydropower can protect water tables against drought and biochar from biomass can help soil preserve water.

Biomass

• Biomass energy use has the chance to significantly lower greenhouse gas (GHG) emissions. Burning biomass emits roughly the same quantity of carbon dioxide as burning fossil fuels. But, fossil fuels emit carbon dioxide gathered by photosynthesis millions of years prior—a basically “new” greenhouse gas. Biomass, though, emits carbon dioxide that is mainly balanced by the carbon dioxide captured in its own growth.
• Burning garbage in waste-to-energy plants could end in far fewer amounts of waste in landfills.
• Biochar (black carbon made from biomass sources) can help restore degraded soils, increasing agricultural productivity and aiding soils in preserving water.

Geothermal

• Geothermal power plants release 97 percent fewer acid rain-causing sulfur compounds and nearly 99 percent less carbon dioxide than fossil fuel power plants of the same size.
• Geothermal power plants use scrubbers to get rid of the hydrogen sulfide naturally located in geothermal reservoirs.
• The majority of geothermal power plants insert the geothermal steam and water used back into the ground. This recycling process helps to renew geothermal resources and to lower emissions.

Hydropower

• Hydroelectric power plant reservoirs gather rainwater, which can be utilized for consumption or farming irrigation. In storing water, hydropower plants protect the water tables against running dry and lower human risk to droughts.
• Dams may be used to control floods in an area if the dam release system is handled properly.
• The hydroelectric life cycle makes only very small quantities of greenhouse gases. In releasing less GHG than power plants fueled by gas, coal or oil, hydroelectricity can help delay global climate change further. Although merely 33 percent of the available hydroelectric capacity has been advanced yet, hydroelectricity stops the emission of GHG related to the burning of 4.4 million barrels of petroleum each day across the world. Hydroelectric power plants do not emit pollutants into the air. And hydroelectric developments do not give rise to toxic by-products.

Solar

• Solar energy systems do not create air pollutants or carbon dioxide, helping to reduce the human carbon footprint.
• Solar on buildings have minimal effects on the environment. Since the panels are placed on an already existing construction, there is no further habitat loss, like there is with building a fossil fuel power plant.
• Solar is reliable. Having it be reliable means less materials and resources are needed to fix constantly breaking parts.
• Solar is quiet, reducing noise pollution. Sound is a crucial way many wildlife learn about their environment. They use sound to steer, communicate, and forage. Too much noise pollution can increase an organism’s chance of death by altering the fine balance of detection between predators and prey.

Wind

• Wind energy does not pollute the air like fossil fuel power plants, which emit particulate matter, nitrogen oxides, and sulfur dioxide—resulting in health issues and economic costs. Wind turbines do not emit atmospheric emissions that result in acid rain, smog, or greenhouse gases.
• There are no damaging fluids used in the generation of wind energy.
• The majority of electric power plants need water to run, and water use in drought-afflicted locations such as the western United States is a major problem. There is no water needed to generate electricity from wind.

Diversifying energy supply

• All five renewable energy sources can lower dependence on foreign oil.
• Solar energy has the capability to produce electricity in remote areas not connected to the grid and wind lowers the risk of cost spikes and supply interruptions.

Biomass

• Biomass use can lower dependence on foreign oil since biofuels are the sole renewable liquid transportation fuel available.

Geothermal

• Even in freezing climates, everyone has access to the steady 48–55-degree temperatures under the ground’s surface. Geothermal energy is available all throughout the day and every day of the year. Geothermal power plants have average capabilities of 90 percent or higher, compared to roughly 75 percent for coal plants. By having it be more efficient, this aids in diversifying the energy supply.
• The price of geothermal electricity does not vary with fossil fuel supply and demand. This results in a low-cost and consistent electricity source.

Hydropower

• Because hydropower is versatile and can store energy, it’s compatible with other types of energy generation. With more kinds of different generation such as wind and solar being utilized, hydropower can ensure power supplies stay continuous — even when the sun stops shining or the wind stops blowing. By adding to an assorted energy mix, hydropower secures human energy independence and lowers the United States dependency on imported fossil fuels.

Solar

• Solar energy has the capability to produce electricity in remote areas that are not connected to the grid. This is more economic than running vast sets of wires into remote areas, and in turn helps in diversifying energy supply.

Wind

• Adding wind power to the energy blend diversifies the national energy portfolio and lowers America’s dependence on fossil fuels from abroad. Wind energy stabilizes the price of electricity and lowers risk of cost spikes and supply interruptions. With the growing use of electric and plug-in hybrid transportation, wind energy can also lower U.S. reliance on imported vehicle fuels.

Economic development and job creation

• Biomass supports the forestry and agricultural industries while hydropower can make recreational areas and support boating and fishing.
• Wind power plant owners pay rent to the farmer or rancher for using the land and solar employs many veterans of the U.S. Armed Services.

Biomass

• Biomass energy aids U.S. farming and forest-commodity industries. With developing technology, —agricultural residues like corn stover (the stalks, leaves, and plant husks) and wheat straw will also be utilized, furthering ties to the agricultural industry. Long-term proposals include growing dedicated energy crops, like quick-growing trees and grasses, and algae. These feedstocks can flourish sustainably on grounds that cannot support exhaustive food crops.

Geothermal

• A geothermal project for electricity production includes the services of investors, government executives, regulatory figures, auditors, economists, environmentalists, management and marketing groups, legal experts, geophysicists, engineers, drilling workers, logistics individuals, operations and maintenance units, and a utility board. Many hands are needed to ensure the prosperity of a geothermal venture. The amount of workers hired under such a project shows the major economic influence geothermal creation delivers to a country through capacity building, greater global presence, and partnerships, and heightened gross domestic product (GDP).

Hydropower

• Hydroelectric installations deliver electricity, highways, industry, and trade to populations, thus strengthening the economy, furthering access to health and education, and bettering general well-being. It provides great opportunities and is available where progress is most needed.
• Hydroelectric developments have an average lifetime of 50 to 100 years. They are long-lasting investments that can help different generations. It is simple to upgrade them to include more recent technologies, which further aids economic development.
• Dams made for hydropower production may produce locations for recreational use such as boating and fishing.

Solar

• Since 2010, the U.S. solar labor force has grown 123 percent. Veterans of the U.S. Armed Services comprise 8.1 percent of the entire solar labor force.
• The Solar Foundation, a nonprofit corporation that encourages the use of solar methods to help meet global energy consumption, gauges that in August 2010, 93,000 individuals spent greater than half their work hours on projects connected to solar energy. The solar industry includes individuals in science, engineering, manufacturing, building, and installation.

Wind

• Wind turbines can be constructed on already present farms or ranches. This largely benefits the economy in rural areas, where the majority of strong wind sites are located. Farmers and ranchers can carry on tending the land because the wind turbines use merely a small portion of the land. Wind power plant owners pay rent to the farmer or rancher for using the land, thus giving landowners added income.
• Wind allows the U.S. industry to grow and compete with other nations. New wind projects in the U.S. are responsible for annual investments of more than $10 billion. The United States has a largely skilled workforce and can compete with countries around the world in the clean energy economy.
• The U.S. wind sector employs over 100,000 workers. A wind turbine technician is one of the quickest growing American positions available. Wind has the possibility to support over 600,000 jobs in development, installation, maintenance, and supporting operations by the year 2050.

Renewable energy certificates (REC)

• RECs serve as a crucial part in accounting, tracking, and designated ownership to renewable electricity production and consumption.
• REC Arbitrage is a green power attainment idea used by electricity purchasers to hit two objectives.

A renewable energy certificate, or REC is a market-based tool that denotes property rights to the environmental, social, and non-power characteristics of renewable electricity production. RECs are released when one megawatt-hour (MWh) of electricity is produced and sent to the electricity grid from a renewable resource.

RECs have various data traits, including:

• Certificate data
• Certificate kind
• Tracking system ID
• Renewable fuel kind
• Renewable facility area
• Nameplate capability of project
• Project name
• Project build date
• Certificate generation
• Certificate unique identification number
• Utility to which project is related
• Eligibility for certification
• Emissions rate of renewable resources

Because the physical electricity obtained through the utility grid does not announce the origin or how it was produced, RECs serve as a crucial part in accounting, tracking, and designated ownership to renewable electricity production and consumption. On a shared grid, RECs are the tool that electricity buyers need to use to uphold renewable electricity use claims. RECs are assisted by various governmental levels, regional electricity transmission officials, nongovernmental organizations (NGOs), and trade associations, including in U.S. case law.

REC Arbitrage

REC Arbitrage is a green power attainment idea used by electricity purchasers to jointly hit two objectives:

1. Lower the price of renewable electricity consumption; and
2. Uphold renewable electricity use and carbon footprint decrease claims.

The concept is used by purchasers installing individual-financed renewable electricity projects or buyers who acquire renewable electricity right from a renewable electricity project, like through a power purchase agreement (PPA).

What is the importance of RECs?

• RECs are the currency of renewable energy trades in compliance and voluntary markets.
• They give access to, grant, and claim use of renewable production on a combined grid.
• RECs Influence electricity market dynamics by providing an outlet for buyer preferences for certain types of electricity produced from renewables.
• REC attainment lowers available REC supply putting forth a demand signal to the market to create a greater supply.
• They inspire new renewable energy production.
• Individual states can drive production through mandated programs (Solar renewable energy certificate programs).
• RECs are an instrument used for hitting corporate objectives for greenhouse gas reporting and for state policy requirements under Renewable Portfolio Standards (RPS).