Monday, April 9, 2012

Renewable Energy: A Strategy for Long-Term Survival

Renewable Energy: A Strategy for Long-Term Survival
by Joel Boyce

This year, Care2 decided to expand Earth Day into Earth Month, since there is so much to explore when it comes to the environment. Every day in April, we’ll have a post about some of the most important topics for the environment, exploring and explaining the basics. It’s a great tool to help you get started with helping the environment or help explain it to others. See the whole series here.

What is Renewable Energy?
Broadly speaking, renewable energy is an energy source that naturally replenishes itself. Energy captured directly from the sun as heat (in solar thermal) or electricity (in solar voltaic) are good examples of renewable. When we use up this energy, we can just get more the next time the sun shines.

This is in comparison to a non-renewable energy source, which, by definition, will eventually run out. Fossil fuels are non-renewable. The bulk of the world’s oil reserves are expected to be gone by mid-century.

Endless Energy
Renewables are a free lunch. We will never have any major energy crises as a result of a renewable energy sources drying up. That’s because renewables are ultimately drawn from energy sources that will outlast the Earth itself.

The primary source of renewables is ultimately radiative energy received from the sun. Solar energy captures energy directly from the radiation that strikes the Earth’s surface. However, temperature differences due to the uneven heating of the Earth ultimately power our planet’s weather systems. Thus, wind power and wave power are also a form of solar energy, as is hydroelectric (which is replenished by rainfall).

Plants also store solar energy in the chemical bonds that knit up their living tissue. This energy can be consumed by humans and other animals who can, in turn, do more useful work. Or the energy can be released more directly, as in the examples of burning firewood or bio-fuels (living plant-derived ethanols, for example).

Two non-solar renewables are geothermal energy, which is partly powered by radioactive decay deep in the Earth, and energy captured from the ocean’s tides, which is ultimately drawn from the gravitational tug of both the moon and sun on our planet’s oceans.

Ancient Solar and Unwanted Byproducts
It comes as a surprise to some people that fossil fuels like oil, coal and natural gas are ultimately sun-derived energy sources as well. Made from dead plants and animals that were unable to decompose (usually because they were covered in mud and water where decomposers and oxygen couldn’t get at them), time and pressure eventually compressed them into energy-dense combustibles.

The critical difference between renewable and non-renewable sources, from an environmental perspective, is this: renewable sources, even bio-fuels, allow us to use only as much energy in a given period of time as our planet receives from the sun, its core and tidal forces.

Our ancient hunter-gatherer ancestors utilized fire as a tool and an energy source, but the creation of energy storing plant-tissue via photosynthesis and the decomposition of that same tissue via herbivorous stomachs, decomposing microorganisms, or a campfire, is the complementary part of that cycle, and results in the same chemical products that initially went into it (carbon dioxide and water). Ultimately, our stock of firewood is limited by the amount of solar energy captured by our forests.

Non-renewables allow us to gain additional energy stored at a previous time, but both the energy and the physical byproducts are outside of our planet’s short-term cycles. The burning of fossil fuels releases carbon dioxide that has been stored away for hundreds of millions of years, resulting in a rapid and violent shift in our climate. Some of the side-effects include running out of things that are supposed to be self-sustaining, like our fishing stocks, arable farmland and precious biodiversity.

Even nuclear energy, which many environmentalists advocate as the lesser of two non-renewable evils, releases large amounts of energy, but the process of nuclear fission creates byproducts that are difficult to store and dangerous to human health.

No comments:

Post a Comment