Image Source: Matter Network
Dear Pablo: As we get more and more energy from the wind and tides, won’t we start interfering with those fundamental forces? Or are our efforts so puny that they won’t matter? Am I nuts to think that our efforts might affect the earth’s rotation or the Gulf Stream, or have other significant, unanticipated consequences?Your concern is certainly warranted, especially when you consider that people never imagined that humans could have an effect on the climate, as we now undoubtedly do. Harnessing energy, no matter the source, either depletes a store of finite energy (oil, gas, coal, etc.), or harnesses the output of a renewable source (wood, solar, etc.). We know that we are having an effect on the finite resources, with many believing that half of the world's available oil has already been extracted, but what effect do we have on renewable resources?
Some renewable resources, such as wood and other forms of biomass, are renewable because they are rapidly self-replicating. The problem with this type of renewable resource is that there is a specific sustainable yield, beyond which the ability of the resource to renew itself becomes compromised. To better understand this type of predicament, think of the timber industry in many parts of the world, where unsustainable harvesting practices have led to deforestation and a complete cessation to the local forestry industry for at least 30 years, not to mention all of the other harm that comes from deforestation. But wind, solar, tide, and hydroelectric energy are not self-replicating, and therefore not bound by such constraints, right?
Nearly all sources of renewable energy get their energy input from the sun, with the exception of geothermal and tidal power (which is dependent on the moon). Solar energy enters the earth's atmosphere, where it feeds plants with energy and warms the surface. This surface warming warms the air, which rises and is replaced by cooler air rushing in from the side. This is how we get wind, and wind creates waves. This surface warming also evaporates surface moisture and creates clouds that feed our hydroelectric reservoirs with water.
How We Harness Renewable EnergyThe direct harnessing of the sun's energy through solar photovoltaic panels on your roof, or large scale concentrated solar power facilities such as those being developed by BrightSource Energy, does not represent a significant overall change to the absorption or reflection of solar energy by the earth's surface and is therefore unlikely to have any major negative effect on the earth's natural systems.
The harnessing of wind to generate electricity, while growing drastically, will also never be widespread enough to have an impact on the overall functioning of the earth. According to a study by Stanford, the mean wind speed, at 80 meters above the surface (the height of the hub of a modern wind turbine) is 4.59 meters/second. If we placed one wind turbine in each of the world's 150,000,000 square kilometers we would produce 231,329,250,000 MWh per year, which is equivalent to millions of nuclear power plants. Obviously we could never use that much electricity, but my point here is that even at this extreme we would have as little of an effect on the wind as a few trees.
Waves are no different, except that water is far more dense than air and carries a lot more energy. Think of waves as a collection of wind energy over miles of open ocean. This energy is usually dissipated on the shores and goes virtually unharnessed. In a past article on wave power, I calculated that a single wave power facility off of San Francisco's Ocean Beach could provide as much electricity as 21 nuclear power plants. So clearly, we do not need a lot of wave power facilities to meet our needs, which would have very little effect on the oceans.
How Harnessing Resources May Affect the the Earth's RotationThere is one more energy source to explore, and this might surprise you. According to Dr. Benjamin Fong Chao, a geophysicist at the NASA Goddard Space Flight Center, the amount of water stored in the world's dams is not insignificant; at about 10,000,000,000 metric tons, and it has an effect on the earth's rotation. The reason is that most reservoirs are in higher latitudes, closer to the earth's poles. Similar to a figure skater bringing her arms in to accelerate her rotation, the earth has sped up as well. In addition, the water captured by dams has offset about 1.2 inches of sea level rise cause by climate change, reducing the lunar tidal drag on the earth's rotation. Dr. Chao estimates that, over the past 40 years, each day has been 0.2 millionths of a second shorter as a result (a total of 0.00292 seconds).
Compared to the drastic climate-altering effects of the alternative, I don't think you have anything to worry about with renewable energy.
Ask Pablo is a weekly column that aims to answer your pressing eco-quandries. Want to ask Pablo a question? Simply email Pablo(at)treehugger(dot)com. Wondering why Pablo's qualified to answer? As the VP of Greenhouse Gas Management at ClimateCHECK, he helps major corporations measure and manage their greenhouse gas emissions.
More on Renewable Energy
Inventor builds Wave Generator at Home
The Onion on the Global Rotation Crisis
More on the Effects of Renewable Energy
Dams for Water Supply Are Altering Earth's Orbit, Expert Says
Ask Pablo: Wave Power