As governments roll out strategies for reducing emissions, investors check up on businesses' environmental performance, and regular people grow concerned with their carbon footprints. At this point, everyone understands that using fossil fuels for energy is one of the most significant contributors to climate change. However, not everybody is familiar with the alternatives. This roundup briefly introduces the 5 primary sources of renewable energy.
Biomass includes wood, agricultural materials, and animal waste. It is the primary energy source for cooking and heating in developing countries. Likewise, it was the most common energy source in the US until the mid-1800s coal displaced it.
The most common way to convert biomass to energy is direct burning, typically with wood. However, modern technology can produce solid, liquid, and gaseous fuels through chemical and biological conversion processes. The energy from biomass is renewable because it ultimately comes from the sun – plants use photosynthesis to convert sunlight to energy, which we then release by burning.
The wind is renewable because it is a natural byproduct of the Earth's rotation. During the day, the air over land quickly warms, expands, and rises. The cooler air over the ocean rushes in to fill the void, causing wind. Then at night, the air over the land cools more quickly than the air over the sea, reversing the process.
Farmers have used windmills to convert wind energy to mechanical energy for over a thousand years to grind grain and move water. Now, we use them to generate electricity through turbines.
Similar to wind, hydropower relies on the natural day-night cycle. First, surface water from oceans, lakes, and rivers evaporates under the sun's heat. Then after it cools, precipitation falls and collects again to restart the cycle.
People have used water wheels for thousands of years to produce mechanical energy. But now, we can build huge dams to control water flow with modern construction techniques. Hydroelectric plants allow water to flow through turbines on their way back to the sea to produce electricity.
The sun is the ultimate source of all energy in the solar system. We have used it intentionally for thousands of years to dry foods for preservation. We collect the sun's energy to heat water and buildings in the modern era. In addition, photovoltaic cells can convert sunlight into electricity.
Solar power creates no pollution and emits no carbon. Moreover, it is not disruptive to the environment when used on buildings. However, the distribution of sunlight on the planet is not constant and varies due to geography, weather, and the change of seasons. Moreover, the energy is diffuse. Providing enough electricity for a large population requires photovoltaic panels to cover many acres.
Unlike the other forms of renewable energy, geothermal does not come directly from the sun. Instead, we harness the heat produced by the Earth itself to heat water and buildings and to produce electricity.
Geothermal heat comes from the core of the Earth, a molten mass over 10,000 degrees Fahrenheit, roughly the same as the sun's surface. Geothermal power plants make electricity by tapping high-pressure hot water pockets deep below the surface. The water produces steam to power a turbine, cools, and then is injected back into the Earth.
- Go Solar – Many states and municipalities offer incentives to people who install solar panels on their houses. They can be expensive, but it is a one-time investment. Furthermore, many exterior lights have their own solar panels.
- Get in Touch – Call your electric utility and ask about their renewable energy services. Some companies allow customers to elect what percentage of renewable energy they want.
- Hold the Gov't Accountable – Not every elected official is on board. If you have a stubborn local, state, or federal official, give them an earful (politely, of course!). As more people make demands, reps and senators interested in reelection need to start listening.