Renewable energy is a term becoming increasing prevalent in news reports and conversations. So what does it actually mean, what main types of renewable energy sources are there and what are the benefits and disadvantages of each?
Renewable energy definition
Renewable energy is derived from natural resources that can be replenished naturally within a relatively short time frame and with potential to provide energy well into the future.
Why is renewable energy important?
Energy derived from fossil fuels create a heavy toll on the environment. It is the major driver of many wars, unrest and more recently issues such as climate change and global warming have become more pressing.
When fossil fuels are burned, they generate carbon dioxide and other greenhouse gases. These gases trap heat within our atmosphere, warming the planet and altering climate in a much shorter time than would occur naturally. This is already having devastating effects such as increased and more frequent droughts and more severe storms.
Additionally, fossil fuels are finite. Oil production from easily accessible reserves is in decline (also known as Peak Oil) and while huge coal reserves do exist, they are also limited. It takes many thousands of years for natural processes to create crude oil and coal, far longer than the rate we are using them.
Renewable energy types
Solar power
Solar power is actually a form of nuclear energy. The sun is a massive nuclear reactor that produces heat and light and will continue to do so for billions of years. We can harness this energy through the use of solar panels, collectors and concentrators to generate electricity and the heating or capture of water.
The main benefits of solar power are the fact that it's an inbound energy source, nothing is taken from the planet. However, equipment needs to be manufactured to harness the sun's rays. Even so the energy payback time, that is the amount of time it takes to repay the energy and resources gone into creating something such as a solar panel, is quite short. In the case of a solar panel, it's around 1.5 years. Given a solar panel has a life of 25 years, this is quite ecologically economical.
Another benefit of solar power is that it can be installed on many homes - allowing a degree of energy independence.
The main disadvantage of solar power is the high cost of equipment and the need for an energy storage system such as a battery bank for when the sun is not shining. Learn more about solar power
Wind power
Wind power is actually a form of solar energy as the sun creates the atmospheric conditions necessary to generate wind. Wind can be harnessed by wind turbines to generate electricity. In some countries wind power is now making up to 10% of energy needs. On a smaller scale, like heat from the sun, wind energy can be harnessed for simple tasks around the home such as drying clothes.
Again, wind turbines are quite expensive, do require more maintenance than solar panels and a storage system is needed for when the wind isn't blowing. Wind turbines can be installed on homes, although in some areas, government regulations forbid them. Learn more about wind turbines
Geothermal power
Geothermal power harnesses the heat from rocks deep below the Earth's surface that have been heated by the Earth's molten core. Water can be injected into holes leading to these rocks to create steam that can drive turbines to generate electricity.
While the construction of geothermal plants are very costly, creating electricity from that point onwards is quite cheap.
The main disadvantages of geothermal power is that it's only viable in limited geographical areas due to the depth of the hot rocks and the availability of water.
Tidal power
As tides move in and out, the water embodies a huge amount of kinetic energy. This energy can be tapped with special turbines that will work regardless of whether the tide is ebbing or flooding.
The major disadvantage of tidal power are the costs involved, corrosion and high maintenance.
Hydro power
Hydro power has been in use for thousands of years. It simply uses the inertia of the flow of a body of water to spin turbines or power a mill for grinding grain.
In more modern times, hydro electric power has supplied many homes with electricity. Unfortunately, this has seen hundreds, if not thousands of waterways around the world dammed to create the necessary water pressure and infrastructure to make the flow of water useful. Many unique wilderness areas have been lost as a result.
Wave power
Another form of harnessing water, wave power utilizes special equipment such as floating structures that move with the waves and are attached to a generator that converts this movement into electricity.
Wave power is still relatively new, but aside from the further refinement and development required and posing navigational hazards, it has few drawbacks.
Biomass
Biomass refers to plant and animal material that can be burned to generate energy. It can take the form of crops, crop waste, trees and animal waste. While these are renewable resources, biomass has similar challenges to fossil fuels in that carbon dioxide and other greenhouse/toxic gases are generated when combusted.
Proponents of biomass point out that in some ways, the burining of biomass is carbon neutral. Unlike fossil fuels, biomass is derived from organisms on the surface that have in some way extracted carbon from the surface, or very close to it. When combusted, this carbon is simply returned to the atmosphere and earth. However, a fine balance needs to be maintained between burning and growing, otherwise the generation of greenhouse gases will exceed what the biomass source is storing.
Biogas
Biogas is methane gas; a byproduct of decomposition, livestock production, cultivation of certain plants and landfills that can be captured and burned. The burning of methane gas is more desirable than allowing it to escape into the atmosphere as methane has a GWP (Global Warming Potential) 62 times that of carbon dioxide.
Biofuel
Biofuel is liquid fuel such as ethanol or biodiesel created from plant material and more recently, algae. Again, it presents some of the same challenges of burning anything. Additionally, the use of food crops as fuel has caused prices of some grains such as corn to skyrocket in recent years. A United Nations food expert went as far to describe using food as fuel as a crime against humanity.
Research into refining the cellulostic ethanol process is continuing - this is where more woody stock and crop waste can be converted into ethanol rather than the crop itself, but a more promising technology is the use of algae to create biofuels.
Is nuclear power renewable energy?
Some believe since Earth-based nuclear resources are so vast, it could be considered renewable. However, coal was also thought to be in such great quantities, it would never run out. So in keeping with the definition, nuclear power can't really be considered a renewable energy source as it would be consumed faster than the natural elements could be produced.
The future of renewable energy
Increasingly, governments around the world are turning to renewable energy to end our dependence on fossil fuels. As you can see from the above, the environmental friendliness difference between various renewable energy types is quite vast and to rely on some of the options would likely cause as many problems as we are now experiencing. Technologies such as solar, wind, wave and tidal power would appear to be the most gentlest alternatives in relation to the well-being of our planet.
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