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BASIC KNOWLEDGE - RENEWABLE ENERGY SOURCES What is renewable energy? Definition, types, and challenges

Author / Editor: Luke James / Nicole Kareta

Wind and solar power are bringing about a clean energy revolution. Here is everything that you need to know about renewable energy, the different types, and the advantages and challenges of it, plus a look to the future.

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Now that we have innovative and cheaper ways to capture and retain renewable energy sources such as the sun and wind, renewables are becoming a much more important power source.
Now that we have innovative and cheaper ways to capture and retain renewable energy sources such as the sun and wind, renewables are becoming a much more important power source.
(Source: ©Mike Fouque - stock.adobe.com)

Renewable energy, sometimes referred to as “clean” or “green” energy, is a booming innovation that is bringing down energy costs and delivering on its promise of a cleaner, greener future. Across the world, from Europe to America, solar and wind generation are breaking record after record as they slowly start to penetrate national electricity grids without compromising on electricity.

This means that renewable energy sources are slowly but surely displacing “dirty” energy sources, such as fossil fuels (e.g., coal and oil) in the power sector and offering the benefit of lower emissions and pollution levels.

What is the definition of ‘renewable energy’?

When we say, “renewable energy”, “renewable energy sources”, or “green energy” we mean any energy from a source that is not depleted when used, such as the wind or sun; we can use an unlimited amount of the sun or wind’s energy because its supply is infinite.

While renewable energy is sometimes thought of as a new technology, harnessing the power of nature has long since been used for heating, lighting, transportation, and more. Wind, for example, has been used for hundreds of years by sailors to move boats across the ocean. Meanwhile, farmers have long since relied on the wind to make their windmills turn and grind down grain. The sun has also been used for a very long time to help kindle fires and in some cases for cooking.

However, over the course of the last few hundred years and especially during the industrial revolution, humans have turned to cheaper and dirtier energy sources. While these are not more abundant than renewable sources like the sun and wind, they are much more convenient and efficient to use… or, at least, they have been up until now.

Now that we have innovative and cheaper ways to capture and retain renewable energy sources such as the sun and wind, renewables are becoming a much more important power source. In Europe, for example, energy from renewable sources made up 34 percent of gross electricity consumption, up from 32 percent in 2018. The renewables expansion is happening on both a large and small scale, from rooftop solar panels on homes to giant offshore wind farms and battery plants. Renewables have become so reliable, in fact, that some rural communities rely on it entirely for lighting and heating.

What is ‘dirty energy’?

When we say, “dirty energy”, we are referring to fossil fuels such as oil, gas, and coal. These are non-renewable (i.e., finite: once they are gone, they are gone for good) and only available in limited amounts. While it is true that these sources do replenish, it takes a very, very, very long time—in some cases, millions of years—to replenish.

Non-renewable energy sources are also only able to be found in certain parts of the world. This means they are more plentiful in some nations than others, such as the “oil-rich” Arab states. In contrast, every country on Earth has access to renewable sources such as the sun and wind. Prioritizing renewable energy therefore levels the playing field and makes countries less reliant on others, something which has a knock-on effect on things like national security.

Finally, non-renewable energy sources are a risk to the environment and human health. Oil drilling, for example, might require strip mining or fracking, which can cause earthquakes and water pollution. It can also damage habitats. Some non-renewables, such as coal, can lead to air pollution which is not only bad for our health but contributes to global warming.

Why does renewable energy matter?

Renewable energy sources account for a growing chunk of energy consumption in Europe, the U.S., and the wider world.

They are a fast-growing source of clean, low- or zero-carbon electricity. While cost can sometimes be a barrier to the adoption of renewable sources—as we will explore in more detail later—rapid advances in technology, supply chains, and government policy have contributed to their growth in recent years.

These renewable energy sources are important because they provide reliable power supplies and fuel diversification. These help to improve energy security, the environment, and conserve natural resources and habitats. They also reduce the need for costly fuel imports and accidents such as oil spills, such as the Deepwater Horizon oil spill of 2010 which claimed the lives of 11 rig workers and millions of marine animals, including mammals, birds, and fish.

Different types of renewable energy sources

While solar and wind are the two most referred to types of renewable energy, there are several. These include:

Solar renewable energy

Solar energy is energy that comes from the sun. This is harnessed by solar (or photovoltaic (PV)) cells made from silicon that is found in solar panels. These cells transform sunlight into electricity. The most common types of solar systems are those found on top of rooftops that generate electricity locally for homes and businesses. However, solar panel systems on a large enough scale can be powerful enough to power entire neighborhoods and provide electricity for thousands of homes.

Solar is now seen as such a viable energy source, in fact, that most developed nations have government-backed schemes and incentives that “reward” home and business owners for installing solar panels on their property. These include everything from cashback and tax breaks to paying homeowners to “sell” their surplus power to national power grids. Solar is an example of zero-carbon energy; it doesn’t produce any pollutants or harmful by-products beyond those generated during the solar PV cell manufacturing process.

Wind renewable energy

Today, wind energy is harnessed through wind turbines that in some cases can be as tall as skyscrapers. While wind turbines are usually found on-shore, but they can also be found off-shore where wind speeds tend to be higher. A turbine system works by the wind energy turning its blades. This feeds an electric generator and produces electricity which can then be used by the grid.

The wind has quickly become the cheapest energy source available in many parts of the world. In Europe, the latest estimates say that there is now 142 GW of installed wind energy capacity and in 2015 it accounted for 44.2 percent of total power capacity installations.

Hydroelectric renewable energy

Hydroelectric renewable energy is currently the largest renewable energy source in the United States, but wind energy is expected to catch up soon. While it is a viable renewable energy source, there is limited potential for it to be captured because it relies on fast-flowing water, such as that found in a river or waterfall, descending from a high point to create a force that spins a generator’s turbine blades.

That being said, there are many who argue that hydroelectric is not in fact a renewable source. This is because large-scale hydroelectric plants can sometimes reduce natural water flows and restrict access to animal habitats and human populations that rely on rivers and waterways for survival. On a smaller scale, however, carefully managed hydroelectric plants are not thought to be damaging to the environment.

Geothermal renewable energy

Geothermal energy is the heat that comes from the sub-surface of the Earth. It is contained in the rocks and fluids beneath the earth’s crust and can be found as far down to the earth’s hot molten rock, magma. To create power from geothermal energy, wells must be dug deep into underground reservoirs to access the steam and hot water they contain. This can then be used to drive turbines connected to electricity generators.

Geothermal energy is used in over 20 countries. The most famous countries with geothermal activity are the United States (California’s geysers) and Iceland, which has been used as far back as 1907 to produce over 25 percent of its energy. Today, Iceland has five geothermal power plants that leverage the hundreds of hot springs and volcanoes that can be found throughout the country.

Renewable energy advantages

Renewable energy sources have the potential to be transformative for our world. Here are some of the key advantages that they have over fossil fuels and other dirty energy sources:

They won’t run out

Renewable energy technologies make use of resources that come straight from the environment to generate electricity.

These energy sources, as we have explored, include sunshine, wind, water, and heat to name a few. The biggest advantage of these resources is that they simply won’t run out, which cannot be said for many types of fossil fuels—while fossil fuels do regenerate, it takes millions of years for this to happen.

They save money

Using renewable energy can help us to save money in the long run. Not only do renewable energy technologies come with lower maintenance requirements, but their operating costs are lower also.

When we are using technologies that generate power from natural sources such as the sun, for example, there is no need to pay to refuel as we do with fossil fuels. While entry costs have historically been high for things like solar panels and electric vehicle chargers, government incentives and improvements in technology are making them much cheaper and, in some cases, non-existent.

They create jobs

The renewable energy sector is booming, and this is creating more and more jobs. In the United States alone, for example, the wind sector employs a workforce of more than 100,000 professionals from research scientists to turbine technicians.

The renewables sector is also one of the fastest-growing worldwide, and thus is creating more employment opportunities with each passing day. There is significant potential across the entire spectrum, from research and development to construction and maintenance.

Renewable energy challenges

While solar, wind, hydroelectric, and geothermal renewable energies are popular and viable sources of energy and could be the key to fighting off climate change, there are some challenges that are important to consider.

Reliability issues

Renewable energy technologies depend entirely on weather conditions. If it’s not windy, wind turbines can’t turn. If it’s not sunny, less solar energy can be captured. If atmospheric conditions are not optimal enough, renewable energy technologies might not generate any electricity at all. For example, wind turbines require a minimum wind speed to move their blades while hydro generators require enough water flow to spin their turbines.

This is especially problematic when we consider the fact that when renewable technologies are working, they tend to produce a surplus of energy (i.e., more than is being used) which cannot be stored anywhere due to the lack of long-term storage options.

Takes up space

Setting up renewable energy generation facilities, even on a smaller scale in the home, requires not only a potentially huge capital investment but also a lot of free space for installation. While this is OK in the case of solar panels on the roofs of private homes, it becomes much more problematic on a larger scale where 40 hectares of green space might be used up to accommodate solar panels that might only generate about 20 megawatts of energy. Meanwhile, a nuclear power plant can theoretically generate roughly 180 megawatts of energy in the same amount of space.

Not totally green

While renewable sources are clearly the better option than fossil fuels, it still generates pollution. Many renewable energy technologies are created via manufacturing processes that emit a huge amount of pollution, and many of the resources needed for renewables are built using fossil fuels. There are also some examples of renewable energies that directly create pollution, the biggest one being biomass energy that requires the burning of organic matter which releases pollutants into the atmosphere.

Renewable energy & the future

We are quickly advancing towards a renewable and clean energy future. It is the top priority of most developed nations, and increasing awareness among the general population is only accelerating the trend of substituting dirty energy for clean sources by making conscious efforts to be sustainable.

Although there are several challenges facing renewable energy such as long-term storage, high entry costs, and patchy reliability, advances in technology over the next few years are likely to overcome these.

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