Green energy can sometimes get called renewable energy, and vice versa.
But, what some people don’t know is that renewable energy actually falls under the broader category of green/clean/sustainable/eco friendly energy.
In this short guide, we outline what green energy is, and what the different types/sources are.
Summary – What Is Green Energy, & What Are The Different Types
Green energy, which might also be referred to as clean, sustainable or eco friendly energy, doesn’t have one single official definition
One way to describe is though, is, energy that comes from natural resources, is renewable (and not finite or scarce), is sustainable to use in the long term, has minimal negative impact of the environment, and has zero waste.
How ‘green’ an energy source is can be determined by the operation stage of the energy process, or even better – over the entire lifecycle of the energy process
We can see that renewable energy fits under this broader description of clean energy.
Renewable energy comes from natural resources and can be replenished quickly (within the lifespan of humans or muck quicker)
Fossil fuels are not renewable because they take thousands or millions of years to regenerate, making them finite in supply (we have not assessed fossil fuels in the guide below as a result)
Renewable energy isn’t always green energy, but the greenest energy might be renewable
Green energy includes all of the renewable energy sources, and nuclear energy (because of it’s zero emission operation stage)
Wind and solar are probably the greenest energy sources over the entire lifecycle when compared to other green energy sources
*Note – hydrogen is not yet produced at scale by renewable energy (it is mainly being produced by fossil fuels and natural gas), so we have omitted it from this guide.
What Exactly Makes An Energy Source Green/Clean/Sustainable/Eco Friendly?
There are several things that can be looked for or assessed across the entire lifecycle of the energy process:
If it comes from renewable, or finite resources (uranium is finite at the moment)
Whether it is mined or not (uranium is mined)
Whether it is grown and requires inputs such as water and other inputs to grow the resource that is to be used for energy (some bioenergy is)
Whether the operation stage involves the emission of greenhouse gases like carbon dioxide, or the release of air pollution contaminants (renewables and nuclear usually don’t, but bioenergy might)
Whether the operation stage uses a lot of water or other important resources (nuclear reactors can use water for cooling purposes)
Whether there is any other environmental damage or pollution such as water pollution at any stage throughout the energy process (renewables have a land footprint for their setup, and have carbon footprints still for the manufacture of equipment such as solar panels and wind generators. A little known fact is that solar panels actually include plastic as a material. Once renewable equipment reaches the end of it’s lifespan, it needs to either be recycled or sent to land fill. Bioenergy can cause a range of land clearing, resource usage, environmental pollution, emissions, and waste issues in some forms)
Whether there is waste or by-products that are either harmful, or need to be managed/treated (nuclear has nuclear waste, whilst renewables tend to have no waste products apart from some forms of bioenergy)
How efficient the production stage is at turning energy from the resource into electricity (renewables all tend to be more efficient at turning their natural resources into electricity compared to fossil fuels. Biomass also isn’t as efficient as the other renewable energy sources)
The use of important resources like water throughout the energy process (nuclear reactors use a lot of water, and bioenergy can use water for crops or for refining biofuels)
What Are The Different Types/Sources Of Green Energy?
Fossil fuels, including coal, oil and natural gas, are not green energy.
The renewable energy sources are seen as green – you can read this guide for a list with examples and explanations of the different types of renewable energy sources.
The short list is:
Solar (PV – photovoltaic, and thermal)
Wind (onshore, and offshore)
Hydropower (run-of-river, storage, pumped-storage)
Geothermal (steam, and water)
Renewable resources don’t need to be mined, have no or few emissions and air pollution during the operation stage, and produce no or few waste products.
Bioenergy is the one asterisk among this group as it can be grown from crops or come from waste products from other sectors, and can produce emissions and air contaminants when burnt or refined. It can also produce waste products like ash.
In addition to these sources, nuclear can probably also be considered a clean source of energy because it is clean during the operation stage – emitting only a clean vapor (but, uranium does require mining and is finite, and nuclear produces a radioactive waste that needs to be disposed of properly and takes many years break down safely).
Consider The Consumer Stage For Sustainable Energy As Well
Above, we were mainly talking about the production of green energy sources.
Some descriptions extend sustainable energy in particular out to include the consumption and use of this energy in the form of electricity as well e.g. for heating and cooling, or for electric vehicles.
Making sure that these consumer stage systems are energy efficient is one extra way that energy use can be sustainable, in addition to the sustainable production of energy.