Clean energy continues to gain prevalence in the U.S. and around the world. Solar, wind, hydro, geothermal, and biomass energy sources are some of the most popular ways to power our society with a reduced environmental impact and lower costs. In this article, we’ll explain the main types of renewable energy sources and the role they play in our energy mix, policies, and economics.
Renewable energy comes from inexhaustible resources or those that naturally replenish over time. Renewable energy sources are beneficial because they have a limited negative environmental impact compared to fossil fuels. Many renewable energy sources are cost-effective for homeowners, businesses, and governments. The most common examples of renewable energy are solar energy, wind power, geothermal power, hydropower, and biomass.
While some types of renewable energy like solar and wind power are virtually limitless, renewable resources like biomass replenish within a human lifespan. Conversely, non-renewable energy sources like coal, oil, and gas take millions of years to form deep in the earth and deplete many times faster than they can regenerate naturally.
Renewable energy vs. clean energy
The terms “renewable energy” and “clean energy” are commonly used to describe energy derived from renewable resources. While often used interchangeably, it’s important to understand the differences between these two terms.
Renewable energy refers to energy from renewable resources that replenish on a human timescale and don’t run out. Renewables are often environmentally friendly but include power sources that can have some negative environmental impacts, such as hydropower.
Clean energy refers to any net neutral or positive energy regarding pollution and environmental impact. Most forms of renewable energy can also safely be called clean energy.
There are five main types of renewable energy: Solar, wind, hydropower, geothermal, and biomass. Each type has pros and cons and unique applications, and they will all undoubtedly play an important role in our clean energy future.
Solar energy comes from the sun, which supplies our entire planet with the energy we need to survive. Solar panels capture energy directly from sunlight and convert it to usable electricity from homes and businesses. In addition to solar photovoltaic panels (PVs), solar technology can charge battery systems and produce hot water.
Wind power is energy generated from airflow within the earth’s atmosphere. When you feel the wind, you’re simply feeling air moving from place to place due to the uneven heating of the Earth’s surface. We can capture the power of wind using massive turbines, which generate electricity when they spin. Like solar energy, wind power is essentially pollution-free and is a growing and important renewable energy source supplying electricity to grids worldwide.
Hydropower (also referred to as hydroelectricity) generates electricity from moving water. This often happens at large dams or waterfalls where water drops significantly in elevation. Other forms of hydropower include tidal power and wave power, which use the ebb and flow of tides and the power of ocean waves to generate electricity from water.
Hydropower is one of the most significant contributors to renewable energy, but it also has a greater environmental impact than some other renewable energy sources. Notably, hydropower facilities can change water levels, currents, and migration paths for fish and other freshwater life.
Earth has a massive energy source contained within it. The heat that was trapped when our planet formed, combined with heat generated from radioactive decay in rocks deep beneath the crust, results in a massive amount of geothermal energy. All rocks contain trace amounts of radioactive material that decay slowly over millions of years and generate heat. Geothermal heat warms the ground and rock just about everywhere under the earth’s surface and can be used for heating and electricity generation.
Energy generated from organic plant and animal matter is known as biomass and is one of the most traditional renewable energy sources. Biomass fuels, like wood, crop waste, and animal manure, are either burned directly to produce heat or converted into biofuels like ethanol and biodiesel and burned later.
Biomass fuels are considered “carbon-neutral,” meaning they don’t put any extra carbon dioxide into the atmosphere. In principle, as long as new plants are planted and grown whenever plants are harvested and burned for energy, those new plants will take up the carbon produced by combustion, leading to no extra carbon added to the atmosphere. However, regrowing plant life takes time, and the degree to which biomass fuel is truly carbon-neutral is debatable.
Pros Of Renewable Energy
Cons Of Renewable Energy
|Essentially unlimited||Either intermittent or needs to be paired with energy storage|
|Numerous health benefits||Geographic limitations|
|Less sensitive to worldwide energy prices|
On the pros side, clean energy is an essentially limitless source of power, it provides many health benefits, and it lowers the exposure to world energy markets, where prices of fossil fuels can spike unexpectedly.
On the cons side, renewables can be intermittent, they often need energy storage to be fully effective, and deployment is limited by some geographic factors.
Below, we'll explore these pros and cons in further detail.
It won't run out
Renewable energy sources use resources straight from the environment to generate clean power. Renewable resources won’t run out over time, which cannot be said for many types of fossil fuels – as we use fossil fuel resources, they will be increasingly difficult to obtain, likely driving up both the cost and environmental impact of their extraction.
Numerous health benefits
The use of fossil fuels not only emits greenhouse gases but other harmful pollutants that have been shown to lead to respiratory and cardiac health issues. With renewable energy, you’re helping decrease the prevalence of these pollutants and contributing to an overall healthier atmosphere.
Additionally, clean energy supports the health of the natural environment. Renewable energy generation sources emit little to no greenhouse gases or pollutants into the air - this means a smaller carbon footprint and an overall positive impact on the environment. During combustion, fossil fuels emit greenhouse gases, which have been proven to contribute to rising global temperatures and higher frequencies of extreme weather events.
Fuel prices don't matter
With clean energy technologies, the cost of power shouldn't swing around as the cost of fuel rises and falls. The U.S. already produces more energy than it consumes, but the cost of natural gas and other fossil fuels is still sensitive to worldwide demand.
Once you've built a clean-energy installation, the cost to run it over time is extremely low and isn't sensitive to changes in the costs of commodities.
Intermittency is a challenge
Though renewable energy resources are available around the world, many of these resources aren’t available 24/7, year-round. Renewables are considered "intermittent", meaning they aren't capable of producing energy at all times. Some days may be windier than others, the sun doesn’t shine at night or on cloudy days, and droughts may occur for periods of time. Additionally, there can be other unpredictable weather events that disrupt clean energy technologies. Geothermal energy is immune from this challenge, however.
Energy storage is expensive
Because of the intermittent nature of many clean energy sources, there’s a need for energy storage paired with it. While there are storage technologies available, they can be expensive, especially for large-scale renewable energy plants. It’s worth noting that energy storage capacity is growing as the technology progresses, and batteries are becoming more affordable as time goes on.
The United States has a diverse geography with varying climates, topographies, vegetation, and more. This creates a beautiful variety of landscapes but also means that there are some areas that are more or less suitable for renewable technologies. For example, a large farm with open space may be a great place for a residential wind turbine or a solar energy system, while a townhome in a city covered in shade from taller buildings wouldn’t be able to reap the benefits of either technology on their property.
Renewable energy’s portion of our overall energy mix has experienced immense growth over the last several decades.
In 2022, renewable energy accounted for about 22 percent of the United State’s electricity generation in 2022. Wind power and hydropower contributed over 16 percent combined, solar generated 3.4 percent, and biomass 1.3 percent. Geothermal produced less than half a percent of U.S. electrical generation.
In the first five months of 2023, solar and wind actually generated more power than coal for the first time. That followed similar feats in 2020 and 2022 when solar, wind, and hydropower combined all beat coal generation.
Policy tools are essential to increasing the use of renewable energy sources for electricity generation, heating, cooling, and more. Policies at the federal and state level promote renewables and help offset costs for customers of all sizes, from residential to utility-scale projects. The Database of State Incentives for Renewables and Efficiency, or DSIRE is the best place to browse current renewable energy policies at the federal and state level.
Federal renewable energy policy
At the federal level, there are a few important policies to be aware of that prop up renewable energy adoption and development.
The federal renewable energy Investment Tax Credit (ITC) can be applied to residential and commercial solar energy system installations and currently amounts to 30 percent of the total cost of installation.
The federal Production Tax Credit (PTC) is a primary incentive for large-scale renewable energy procurement. The PTC compensates system owners based on production (on a dollar per kilowatt-hour, kWh basis) instead of the system’s upfront cost and is good for the first 10 years of its lifetime. The PTC is currently set at $0.026/kWh for wind, closed-loop biomass, solar, and geothermal resources and 1.3 cents/kWh for landfill gas (LFG), open-loop biomass, municipal solid waste resources, and small irrigation power facilities.
State-level renewable energy policy
Many states have renewable portfolio standards (RPS), which require a certain percentage of a state’s electricity consumption must come from renewable energy sources. Currently, 38 states and Washington D.C. have renewable portfolio standards in place. Some state RPS guidelines even include specific requirements for individual renewable sources, such as solar carve-outs.
Other state-level policy tools to help bolster the adoption of renewable energy include net metering, RECs, and feed-in tariffs, all of which provide financial incentives for renewable energy investment.
Besides being environmentally friendly, many economic benefits come with renewable energy sources. Learn what makes clean energy a positive force for economies everywhere, from low-cost energy to job creation.