Wind Energy

Wind energy is another “clean” energy using the power of moving air to generate electricity. It is renewable because there is no shortage of air on the planet, and it is constantly in motion to a varying degree. It is not completely reliable because the wind is not always blowing, although the wind turbines are at least 100 feet above the ground to take advantage of the less turbulent and more abundant airflow, as compared to ground level.

Wind farm (US Department of Energy)

Wind energy currently makes up 4% of the US energy mix, but is growing and will eventually pass
hydroelectric as most rivers are dammed to capacity. An ideal place for wind farms in the central US
“Tornado Alley” because of nearly constant strong wind. Wind farms are compatible with the
traditional farms of the region and are an economic boon for farmers. They can lease land to energy
companies for windmill placement, and still have the ability to use nearly all of their land. Ridge tops
in the Appalachians are another great location, where topography produces adequate wind speeds.  

Developing technology has greatly improved the efficiency of windmills. Lighter blades, taller towers,
and control systems have increased the average capacity factor from 22% in 1998 to 33% in 2014. As
the race to replace fossil fuels continues, expect efficiency to increase further.

The downside to wind energy, aside from lack of wind, includes environmental impacts. Construction
of windmills in undeveloped areas requires access roads and site preparation, which can be a strain on
the environment. Leaking lubricants can pollute the soil. Birds and can be struck and killed by
windmill blades. However, fewer birds are killed by windmills than stationary buildings. Many birds
are learning to avoid areas containing windmills. Tornado Alley windfarms are away from major
flyways so migratory birds are less likely to affected in that region.

Birds and windmills are not always a good mix (NBC News)

Other negatives are aesthetics and safety. Many people believe the windmills are unsightly and ruin the
landscape. One workaround for that is to install them in developed areas, where they might actually
improve the view, especially if the view is mainly housing developments and shopping centers.
The focus then shifts to noise. The rotating blades can be noisy, depending on the distance from the
listened but the elevation above the ground helps reduce that.

Safety can be an issue when rotating blades are involved. Machines malfunction, and should a windmill
throw a blade, the potential for human death is there. A serious concern in Tornado Alley is that a
namesake tornado could destroy a wind farm and turn the blades into deadly projectiles.

This week's information comes from National Renewable Energy Laboratory, Mount Holyoke College, and US Department of Energy. Next week we'll take a look at solar energy.

Species of the Month

This week we're taking a break from understanding energy sources and trying to understand a species. When you think about lizards, you probably imagine them basking under the hot desert sun or on a tropical island. If that's the case, then June's Species of the Month will surprise you by showing up in some unexpected locations. Say hello to the eastern fence lizard.

Eastern fence lizard (University of Georgia)

Scientific name: Sceloporus undulatus

Kingdom: Animalia (animals)

Class: Reptilia (reptiles)

Order: Squamata (scaled reptiles)

Range: New York south to Florida, west to the Rockies

Habitat: Grasslands and forest edges

Lifespan: Unknown, thought to be four years average

Diet: Insects, some plant matter

Predators: Birds, snakes, other larger lizards, domestic dogs and cats

Conservation Status: No special protection

Other Information: The eastern fence lizard is a widespread reptile. They live under rocks and logs
where they have protection overnight. Cold-blooded, they bask in sunlight during the day to raise their
body temperatures. Normally, they bask close to where they call home. They are little guys. Adults
only grow as long as 19 centimeters. Color varies, but they are usually gray or brown. Males have a
blue patch on the throat and belly. A male will display the throat patch to attract a mate or warn other
males away from his territory. He will also do head bobs and push ups if threatened.
Fence lizard eggs grow after hatching. Mating season begins in April, with hatching taking place from
June to September. The eggs doubles in size between laying and hatching, and babies are half the size
of adults when they emerge. There is no parental care.

Male lizard showing blue throat and belly (University of California, Berkeley)

This week's information is courtesy of the Animal Diversity Web at University of Michigan. Next week
we return to our energy series with a look at wind power.

Tidal Energy

Continuing the series on alternative energy sources, this week features tidal energy. It is similar to
hydroelectric power: it uses the same principles of water in motion and is also a “clean” energy source.
However, tidal power relies not on the temperamental flow of a river which is subject to effects of
weather and climate but on the timeless and ceaseless pull of the sun and moon on the world’s oceans.
Because of its reliance on ocean tides, this is considered a renewable energy source because it does
not diminish the amount of tides in the ocean.

Tidal power is also similar to wind power. Tidal turbines look like miniature underwater windmills.
Tidal turbines can be smaller and more densely spaced than windmills because water is denser than air;
less surface area is required to generate a comparable amount of electricity. While the wind may not
always blow, the tides are always in motion. 

Tide turbines (Forbes)

Another device to harness the energy of the tides is called a barrage. It is similar to a small submerged
dam that blocks the incoming and outgoing tides at the mouth of an estuary. A sluice in the dam opens
to collect the tidewater, which flows though and turns turbines to generate electricity.

One drawback of tidal energy is the tides themselves. Generation capacity is limited by the tidal cycle,
meaning peak demand will frequently be missed. Also, the change in tides must be at least seven
meters for this to be economically efficient. 

Barrages are limited by location. Not all estuaries are suitable sites. The equipment used for generation (either barrages or tide turbines) must be highly durable due to the unforgiving nature of the undersea environment.

Tidal barrage (Britannica)

Like the other energy sources previously mentioned, tidal power has negative impacts on the environment. However, due to limit use of this technology, these impacts are still being studied and at present are not certain to be occurring. The possible impacts include altered waves, currents, substrate, and sediment movement; loss of habitat for benthic organisms; noise that may interfere with biosonar; generation of magnetic fields; introduction of toxins in paint, lubricants, and antifouling; hindrance of fish passage; and fish being struck by blades or sucked into turbines.

This week's information comes from Marine Current Turbines, Ocean Energy Council, and Pacific Marine Energy Center. After a brief break for a look at June's Species of the Month, this series will resume with wind energy.

Pros and Cons of Hydroelectric

Hydroelectric power generates the most electricity of all renewable energy sources in the US, about
7% of the total production. It is a truly renewable source as the same water can flow through a series of dams on a single river, and it is renewable. It is also “clean”, producing no carbon emissions outside of those during the dam building process. 

Water held back by a dam goes through an intake pipe and turns turbines as it passes through the dam.
Faster flowing water will produce more power. Hydroelectric power is about 90% efficient, making it a
great source of power. Due to controls at the dam, the flow of water can be adjusted to meet peak
demands much more quickly than at a nuclear or coal-fired plant. Some dams are equipped with a
pump and can pump water to a higher level during times of low energy usage. The water is then
released back through the dam at peak times to generate additional power.

Not all dams are generating stations, but hydroelectric dams often serve other purposes such as flood
control, irrigation, drinking water supply, and recreation. Because the water is naturally occurring and
free, hydroelectric power is among the cheapest on the market, less than a penny per kilowatt hour on
average. An electric utility can earn additional income through recreational fees, keeping utility rates
low.

Hydroelectric dam in Arizona (USGS)

Although hydroelectric power is “clean”, it is not completely “green”. Like the fossil fuels, it also has
negative environmental impacts. Dams affect fish migration, hydrology, and sediment and nutrient
movement. Flooding a reservoir also causes terrestrial habitat loss, which is traded for aquatic habitat.

Fish ladders can be built to aid anadromous fish in passing around a dam. These fish hatch in
freshwater, live as adults at sea, and return to their native streams to spawn. The journey through
natural aquatic habit frequently involves jumping over small waterfalls, which fish ladders mimic.
Different species of fish move at different speeds and therefore have different needs. Fish ladders come
in many different designs, and some even look like a natural stream rather than a flooded staircase.
Intake screens covering the intake pipes can successfully keep most fish from getting sucked into the
turbines, which can kill them.

Fish ladder (Army Corps of Engineers)

Terrestrial habitat is lost at the expense of aquatic habitat gain. However, the reservoir behind the dam
is of lower quality than a natural lake and alters downstream hydrology. Reservoir water stagnates
since there is no outlet and sediments and nutrients from upstream collect behind the dam rather than
enriching downstream areas. Downstream ecosystems can also suffer if not enough water is released
from the dam.

Sediment deposits after a dam removal in Washington (NPS)

This week's information comes from US Bureau of Reclamation, Michigan DNR, and
Union of Concerned Scientists.