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Pros and Cons of Renewable Energy Sources

It’s no longer up for debate that the end of fossil fuel reserves is in sight. While estimates for the world’s supply to fall short of demand range from about 2020 to 2050, one thing is certain: alternative energy sources are unavoidably woven into humanity’s path toward the future. As the Earth’s population (and its appetite for modern amenities) continues to grow and add stress to the planet and atmosphere, it’s clear that the source of energy that powers the future must be both renewable and clean.

There are many viable options out there, but which one is best? The answer is most likely not one-size-fits-all, but rather a combination of several renewable energy sources. Understanding the pros and cons of these sources can help you make educated decisions about energy policies that will affect our future.


Solar Energy


Solar PV array at the Solar Living CenterSolar energy is responsible for all of the light and most of the heat we experience on Earth. That’s a lot of free energy floating around. The sun’s heat can be harnessed with absorption and conduction in solar thermal collectors to heat water. It can be concentrated with mirrors to cook food and applied to rooms in need of heating with some well-placed windows. Photons (light) from the sun can even be converted into electricity through photovoltaic cells. As renewable energy sources go, the sun is by far the largest and most accessible here on Earth.

Pros

  • Clean and quiet — no moving parts or waste from chemical reactions
  • Solar energy is available anywhere the sun shines and will be for billions more years
  • Heat from the sun can be harnessed without any mechanical aid
  • Many homeowners qualify for solar panel installation with no money down
  • Solar panels are nearly maintenance-free, last for decades, and produce power at a low, fixed cost once installed

Cons

  • Solar energy is only harnessed during daylight hours
  • Weather can decrease the efficiency of solar energy capture
  • Modern solar panels are only around 20% efficient


Wind Harvesting


Harvesting wind powerWhen wind blows against a turbine’s blades it spins them, powering an electric generator. While it is a clean and renewable source of energy, wind is not constant in many places, so wind harvesting doesn’t make sense everywhere.

Pros

  • Clean energy — produces no waste since no chemical reaction takes place
  • Although tall, wind towers take up little ground space, preserving land for other uses

Cons

  • Wind (and therefore dependable electricity) is not constant in most places a turbine can be built
  • Wind turbines alter the landscape and natural aesthetics


Hydroelectricity


Austria's Kaprun hydroelectric damWater is about 800 times denser than air, so its ability to spin a turbine is far greater. When natural forces move water — whether through gravity (rivers and tides) or wind (waves in the ocean) — that “free” kinetic energy responsible for the water’s movement is converted into electrical energy if it spins a turbine hooked to an electric generator. Hydroelectricity is the most widely-used form of renewable energy in the world today.

Pros

  • Clean energy — produces no waste since no chemical reaction takes place
  • Water that passes through the turbine is not contaminated and can be reused downstream
  • With dams, water flow (and therefore power generation) can be regulated to match demand

Cons

  • Dams are expensive to build and can destroy habitats along rivers


Geothermal Energy


Geothermal power stationIntense gravitational pressure and radioactive decay create temperatures of thousands of degrees around the core of the Earth. Much closer to the surface, heat from these processes mixes with groundwater (or water can be pumped in), creating geothermally-heated water or steam that can be used to heat buildings or power turbines. Despite the large role radioactive decay plays in the creation of this heat, all its harmful byproducts are naturally stored deep underground.

Pros

  • Geothermal energy is quite clean — emissions are low and are often limited to water vapor
  • Geothermal plants take up the least space per kW generated of any major power source
  • There is millions of times more geothermal energy available than humans can consume

Cons

  • Because current drilling technology is limited, potential sites for geothermal plants are limited — they must have shallow geothermal heat reserves (at most 2-3 miles deep) and close proximity to surface water for pumping and cooling
  • Outside fuel is needed to operate the water pumps some plants use


Biomass and Biofuel


BiofuelBiofuel is essentially solar energy stored in biomass (plants) during photosynthesis. While it doesn’t often enter the conversation of renewable energy sources, it is actually the one that’s been used the longest, in the form of wood burning. Today, biomass used for the production of biofuels exists primarily in the forms of wood, “energy crops” harvested specifically for biofuel production, plant waste from crops harvested for other purposes, and animal waste. The release of biofuel comes most often from the direct incineration of biomass for heat or electricity generation, but biomass can also be converted into a biogas (methane) through microbial composting of waste and sewage and used as an alternative to natural gas.

Pros

  • Carbon neutral (while alive, biomass acts as a carbon sink and upon death, as a source)
  • Biogas harvesting keeps methane, a potent greenhouse gas, out of the atmosphere
  • Can turn existing waste into energy

Cons

  • Energy is most easily realized through incineration, emitting air pollution and greenhouse gases
  • Large amounts of fresh water are needed to farm biomass and process its waste
  • Without going through expensive refinement methods, biomass has a low energy density so transporting it to a biofuel plant is costly and inefficient


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