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A Look at the Various Renewable Energy Sources

Natural energy sources like the wind, sun, and biomass (which refers to any organic material utilized as a source of energy) provide clean and renewable energy. The sun and wind, among other renewable energy sources, rely on weather conditions, but they remain unlimited in availability. In addition, unlike fossil fuels that emit greenhouse gasses when burned, renewable energy sources produce little or no harmful emissions.

In solar power, photovoltaic panels capture the sun's rays and convert them to electricity. The photovoltaic effect creates a flow of electricity when sunlight causes the electrons in a solar cell to move. Solar-thermal power uses mirrors to concentrate the sun’s rays onto a small area, producing extreme temperatures that generate steam that turns turbines to generate electricity.

In wind power, turbine blades capture the wind's kinetic energy and convert it into rotational energy that generates electricity. Large-scale wind farms can produce significant amounts of energy, while residential and small farm applications can utilize smaller turbines to satisfy on-site electricity demands.

In hydroelectric power or hydropower, the motion of falling water drives a turbine that powers a generator and produces electricity. However, hydropower may have environmental impacts, such as altering water flows and affecting aquatic ecosystems.

In geothermal power, machines or mechanical systems capture the heat in the ground and bring it to the surface to heat buildings or generate electricity. Geothermal energy is a reliable low-emission power source, but it can be geographically limited and release greenhouse gases such as sulfur.

In tidal power, ocean tides turn turbines to capture the kinetic energy of currents and convert it into electrical power. Tidal energy is predictable and reliable but geographically limited, and building tidal power plants could harm the environment.

In biomass power, burning organic matter such as wood, crop waste, and other unneeded organic materials releases energy in the form of heat to generate electricity or provide heat. Anaerobic digestion can also produce biomass energy, with bacteria breaking down organic waste to produce methane.

In ocean thermal power, machines use the temperature difference between surface water and deeper colder water to generate electricity. This process works through a closed-loop system that circulates a fluid with a low boiling point, such as propane, ammonia, or butane. Warm surface water vaporizes the working fluid, which flows through a turbine that generates electricity. The deeper cold water then condenses the fluid back to its liquid state. As a result, ocean thermal energy generates electricity without emitting greenhouse gasses.

In hydrogen power, machines produce clean, renewable hydrogen. Major automakers are already developing and introducing hydrogen fuel cell vehicles as a zero-emission alternative to fossil fuel-powered vehicles. In addition to transportation, hydrogen energy has potential applications in power generation, heating, and industrial processes. However, the high cost of production, storage, and infrastructure development are likely to limit the widespread adoption of hydrogen energy.

In fuel cell power, chemical energy is converted directly into electrical energy without combustion. In a fuel cell, hydrogen gas feeds into one electrode while oxygen feeds into another. The two gasses react to create electricity, water, and heat. Fuel cells have several advantages over traditional fossil fuel-based power sources, including high efficiency, low emissions, and quiet operation. As a result, fuel cells can power vehicles, homes, and businesses. Fuel cell technology is still in development, but it shows promise in the transition to sustainable energy.

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Advantages of Direct Air Capture for Carbon Dioxide

Established in 2021, the US Long-Term Strategy is the official plan on how the nation can meet its 2050 net-zero greenhouse gas emission goals. In addition to reducing emissions by at least 85 percent, the country will have to remove half a billion tons of carbon from the atmosphere to meet those goals. Direct-air capture (DAC) offers various advantages to those working to reduce carbon emissions.

DAC involves using chemical reactions to take carbon dioxide out of the air via liquid solvents or solid sorbents, composed of common substances found in soaps and water filtration that collect carbon dioxide. DAC works when air moves over the chemicals, which selectively trap carbon dioxide, allowing other molecules in the air to pass. After the chemical substance captures the carbon dioxide, heat is applied, releasing it from the solvent or sorbent so it can regenerate for another use.

Another DAC strategy uses electrochemical processes to reduce carbon dioxide in the air at a lower cost. For instance, University of Illinois Chicago engineers built an “artificial leaf” capable of collecting carbon dioxide at rates 100 times better than traditional DAC processes.

This UIC process involves using a leaf with a dry and a wet side. On the dry side, researchers use a solvent to attach to carbon dioxide in the atmosphere, which culminates in the production of baking soda (bicarbonate). Negatively charged ions are pulled across the leaf membrane into a positively charged electrode in a water-based solution on the wet side as the bicarbonate increases. This liquid solution dissolves the bicarbonate, allowing the carbon dioxide to be released and used in other fuels.

Regardless of the method, DAC technology has seen interest from private investment and public research funders. Furthermore, the United States Bipartisan Infrastructure Law mandated an investment of $3.5 billion toward four large-scale DAC projects. Interest in DAC is well-founded, because the technology offers important benefits.

For example, DAC can be installed in various locations, reducing the need for an extensive pipeline network. Furthermore, it does not have to attach to a power plant to remove carbon dioxide. This versatility makes it possible to deploy DAC buildings close to geological formations where the carbon dioxide can be captured and stored. Finally, by reducing the need for such a pipeline network, DAC reduces the incidence of carbon dioxide leaks.

In addition, the technology does not require the use of as much land as other carbon-sequestration techniques, such as bioenergy with carbon capture and storage (BECCS). BECCS involves turning organic material into energy (electricity or heat).

BECCS requires land to grow organic materials, like trees, that can pull carbon dioxide from the atmosphere. According to an April 2021 article in the environmental magazine Treehugger, BECCS land use as of 2019 was between 2,900 and 17,600 square feet per metric ton of carbon dioxide each year. In contrast, DAC buildings only need between 0.5 and 15 square feet to pull carbon dioxide from the air.

As mentioned above, DAC operations remove or recycle carbon dioxide, using the carbon for long-lived products (cement and building insulation) and short-lived products (carbonated beverages and synthetic fuels).

Finally, DAC offers advantages in keeping the amount of carbon dioxide in the air from increasing, creating a negative-emissions scenario. This happens after carbon dioxide is stored in geologic formations or products.