What Alternative Energy Is Available?

Alternative energy refers to energy derived from renewable, sustainable sources that produce little to no greenhouse gas emissions. According to the United Nations, renewable energy comes from natural sources that are replenished at a higher rate than they are consumed, such as sunlight, wind, water, plants, and geothermal heat (https://www.un.org/en/climatechange/what-is-renewable-energy). Alternative energy is important because it can help mitigate climate change by reducing reliance on fossil fuels like coal, oil, and natural gas that emit greenhouse gases when burned.

Shifting to alternative energy sources like solar, wind, and hydropower is a key strategy for reducing greenhouse gas emissions and avoiding the worst impacts of climate change. Widespread adoption of renewable energy can also improve public health by reducing air pollution, create jobs in the clean energy sector, and make countries more energy independent and secure. As the effects of climate change intensify, transitioning to alternative energy will become increasingly important for protecting the planet and charting a more sustainable future.

Table of Contents

Solar

The sun radiates an enormous amount of energy onto the earth every day. Solar power harnesses this energy using photovoltaic cells to convert the sun’s rays into electricity (Source). Solar panels made up of photovoltaic cells can be installed on rooftops, parking garages, or large open spaces to generate power. There are a few main types of solar technologies:

Photovoltaics – PV panels made up of silicon cells that convert sunlight directly into electricity.
Concentrated solar power – Uses mirrors to concentrate sunlight to heat a receiver filled with fluid that produces steam to power turbines and generate electricity.

Solar heating and cooling systems – Capture heat from the sun to provide hot water and air conditioning.

The solar industry has experienced massive growth over the past decade. In 2021, solar accounted for about 3% of U.S. electricity generation, up from 0.35% in 2010 (Source). The amount of solar capacity installed has grown at an average annual rate of 42% over the last 10 years. Many experts predict solar could make up 20% of U.S. electricity generation by 2050 if growth continues at this pace.

Wind

Wind power harnesses the wind to generate electricity using wind turbines. Wind turbines work by using blades to capture the kinetic energy in wind. When the wind blows, the blades spin a shaft connected to a generator that converts the rotational energy into electrical energy [1].

There are two main types of wind turbines:

Onshore wind turbines are located on land, usually in open plains, hills, or mountain ridges. Offshore wind turbines are installed in bodies of water, usually in coastal areas or lakes. Offshore wind can generate more power since wind speeds tend to be stronger over water. However, offshore wind farms are more expensive to build and maintain [2].

Global wind power capacity reached 837 GW by 2021, supplying over 6% of the world’s electricity demand. The United States is a leader in wind power generation, with over 122 GW of installed capacity. In 2020, wind surpassed hydroelectric power to become the largest source of renewable electricity generation in the U.S. [3]. The wind energy industry continues to grow rapidly due to technology improvements, government incentives, and the declining cost of wind power.

[1] https://cleanpower.org/facts/wind-power/
[2] https://www.energy.gov/articles/us-department-energy-projects-strong-growth-us-wind-power-sector

[3] https://www.iea.org/energy-system/renewables/wind

Hydroelectric

Hydroelectric power is generated from the energy of flowing water. Typically, hydroelectric dams are constructed on rivers to create large reservoirs of water. When the water is released from the reservoir, it flows through turbines to spin generators that produce electricity. Hydroelectric power provides around 16% of the world’s electricity and is considered a renewable energy source as it relies on the water cycle [1].

Hydroelectric dams operate by controlling the flow of water to the turbines. The amount of electricity generated depends on both the volume of water flow and the height from which it falls. The largest hydroelectric facilities in the world are massive dams and reservoirs built to generate over 10,000 megawatts of power. For example, the Three Gorges Dam in China has a capacity of 22,500 megawatts [2].

While hydroelectric power is renewable and does not directly emit greenhouse gases, large dams can have major environmental impacts. Building a dam floods areas upstream, altering aquatic ecosystems and often displacing people living in those regions. Dams also change the natural flow of rivers downstream, affecting wildlife habitats. However, proponents argue hydroelectricity has much lower lifecycle emissions than fossil fuel energy sources.

Some major hydroelectric projects today include upgrades and expansion of existing dams rather than building massive new ones. Countries with mountainous terrain and high precipitation like Brazil, Canada, and Norway generate a significant share of their electricity from hydro. With most ideal dam sites already utilized in developed nations, the majority of large hydro construction is occurring in emerging economies.

Geothermal

Geothermal energy refers to harnessing the heat beneath the earth’s surface to generate power. Geothermal energy originates from residual heat in the Earth’s core and radioactive decay of minerals in the crust. Typically hot water or steam from geothermal reservoirs is brought up through production wells to the surface and used to power turbines connected to electrical generators to produce electricity. E360

The three main uses of geothermal energy are electricity generation, direct heating and cooling, and geothermal heat pumps. Currently less than 1% of the world’s energy needs are met using geothermal, but experts believe it could become a major clean energy source. Geothermal electricity production could increase 26-fold according to the DOE. With improvements in technology, geothermal has the potential to provide constant reliable energy in many parts of the world.

Biomass

Biomass is organic material that comes from plants and animals, and contains stored energy from the sun. Biomass can be burned directly or converted to liquid biofuels or biogas that can replace fossil fuels. Sources of biomass include wood, crops, waste materials, and methane from landfills [1].

There are several types of biomass energy:

Wood and agricultural waste – This includes wood chips, pellets, and residue from timber harvesting operations, crops like corn husks and rice hulls, and food waste.
Municipal solid waste – Garbage can be burned in waste-to-energy plants to generate electricity and heat.
Landfill gas – Methane gas naturally forms as organic matter in landfills decomposes and can be captured.

Algae – Special algae called microalgae can be cultivated and harvested to produce oils and fuels.

Biomass can be used to generate electricity, provide process heat for industries, produce liquid transportation fuels, and supply gases that can be used like natural gas. Common methods for exploiting energy in biomass include:

Direct combustion – Burning biomass directly for heat and power generation.

Thermal conversion – High heat converts biomass into syngas or bio-oil.
Biochemical conversion – Bacteria anaerobically digest biomass to produce biogas.

Hydrogen

Hydrogen fuel cell vehicles (FCEVs) like the Hyundai Nexo or Toyota Mirai use hydrogen and oxygen to produce electricity which powers the motor. Hydrogen can be used in fuel cells to power electric motors without producing harmful tailpipe emissions – the only byproducts are heat and water [1].

Some advantages of hydrogen fuel cell vehicles include much faster refueling times compared to battery electric vehicles, long driving ranges of 300+ miles on a full tank, and the fact that hydrogen is the most abundant chemical substance in the universe. Hydrogen can also be produced domestically from several sources including natural gas, nuclear power, and renewable power like solar and wind [2].

However, hydrogen cars face challenges such as very few public refueling stations available. Producing and transporting hydrogen fuel on a large scale would also require major infrastructure investments. Additionally, 95% of hydrogen today is made from natural gas in a process that releases carbon dioxide, undercutting some of its green benefits [2].

Tidal

Tidal energy takes advantage of the natural rise and fall of the tides to generate electricity (https://www.nationalgeographic.org/encyclopedia/tidal-energy/). Tidal projects consist of tidal turbines or barrages.

Tidal turbines work like wind turbines, except they use flowing water to turn the blades, driving a generator inside to produce electricity (https://www.eia.gov/energyexplained/hydropower/tidal-power.php). The Sihwa Lake Tidal Power Station in South Korea has the largest electricity generation capacity at 254 megawatts (MW) (https://www.eia.gov/energyexplained/hydropower/tidal-power.php).

Tidal barrages enclose an area of sea using embankments, while also encompassing turbines to capture the kinetic energy from tides. As the water flows into and out of the basin, it rotates the turbines.

Tidal energy can provide predictible and renewable energy, but it also comes with some limitations. Tidal barrages in particular can disrupt aquatic life and habitat due to the changing water levels and flow inside the barrage. There are also high initial construction costs and limited number of viable sites with optimal tidal flow. Overall tidal shows promise but requires careful planning and environmental assessment.

Wave

Wave energy comes from harnessing the waves in oceans and seas. The motion of the waves contains kinetic energy that can be captured and converted into electricity. Wave energy works by using devices called wave energy converters that sit on or near the surface of the water. The rising and falling of waves moves these devices, which then activates hydraulics to drive an electrical generator. Some types of wave energy converters use an air turbine that spins as waves pass by, turning a generator to produce electricity (Source 1).

Wave energy projects and prototypes have been developed in various parts of the world, though it has not yet reached large-scale commercial deployment. One notable project is the Carnegie Clean Energy wave farm in Australia, which has installed three large wave energy converters. Europe and the west coast of the United States also have significant wave energy resources. Estimates indicate the theoretical potential of wave energy off U.S. coasts could provide up to 2.64 trillion kilowatt-hours per year, which is roughly the amount of electricity used by the entire country annually (Source 1).

While the potential of wave power is significant, there are still challenges to overcome before it sees widespread adoption. Continued technology improvements and cost reductions will be needed. But wave energy could one day make a contribution to clean, renewable electricity generation, especially for coastal communities and islands (Source 2).

Conclusion

In summary, some of the key alternative energy sources that exist today include solar, wind, hydroelectric, geothermal, biomass, hydrogen, tidal, and wave power. Each of these renewable energy sources offers environmental benefits and the potential to significantly reduce our reliance on fossil fuels. Solar and wind power in particular have seen tremendous growth recently as costs have come down dramatically. The future for renewable energy looks bright as many governments and corporations are making major investments into further developing and expanding alternative energy infrastructure globally. With continued innovation and adoption, renewable energy sources are poised to play a major role in powering a cleaner and more sustainable future.