The Power of the Waves

After learning about solar and wind power, I thought hydropower would be a great next topic.  Hydropower is the most common source of renewable energy, as it accounts for about 67% of the United State's total renewable energy production.  First, let's talk about how hydropower works.  Hydropower uses the force of falling water to turn the turbine of a generator.  The water pressure is usually built up by damming a river, and then channeling the water down a large pipe called a penstock.  This increases the water pressure.  After the water turns the turbine, it flows back into the river on the other side of the dam.  This is a renewable source of energy because of the water cycle.  The water that flows out from the penstock will eventually evaporate and start back at the source of the river by rain, snow, or other precipitation.

Hydropower sounds simple enough, but there are several things that need to be considered.  Salmon are fish that swim upstream to spawn.  After spawning, the salmon and their offspring need to swim downstream to return to the ocean.  Damming a river makes it nearly impossible for these salmon to get upstream to their spawning grounds.  Even if they did get upstream, they could easily be killed by the dam on the way back down.  To prevent this problem, dams in rivers where salmon migrate have installed fish "ladders".  These fish ladders are simply a passage around the damn with a serious of steps.  The water flows fast enough over these steps to attract the fish but slow enough that they can leap over them without be washed back down.  

The Grand Coulee Dam in Grand Coulee, Washington produces more power than any other hydroelectric dam in the United States.  Although this dam produces billions of kilowatts of power annually and irrigates about 600,000 acres of farmland, it has no fish ladder.  This dam removed about a thousand miles of spawning grounds for several types of salmon.  This dam, like many others, has its pros and cons.  It is up to you to decide which outweighs the other.  A great video about hydropower can be found here : video. 

One of the Grand Coulee Dam's 33 turbines being assembled

                                                                                                                            

  

The Power of the Wind

After investigating solar power last week, I thought a good topic for this week would be wind power.  The reasons for using wind power are the same as solar, we are slowly but surely running out of fossil fuels.  Wind power is becoming more popular and a lot more high-tech.  First, lets look at how a wind turbine works.  As wind passes over the three blades, it causes them to turn.  This spins a shaft, in turn rotating the gears of a generator.  This may seem simple, but several variables can affect the amount of power generated.  The first one of these variables is wind speed.  The turbine can start generating electricity at about 8 mph.  Once wind speed reaches about 65 mph, the turbine will be stopped because these speeds could damage it.  The radius of the blades also affects the turbines total power output.  Doubling the radius quadruples the output!  Another factor is air density.  Heavier air (at a lower altitude) generates more power.  This is why offshore wind turbines are becoming more common.  With an average wind speed of just 15 mph over the course of a year, a single wind turbine with a blade radius of only 50 feet could power about 50 homes.

So exactly how much power can we get from wind?  Is it possible to rely entirely on wind for power?  To answer these questions, we will take a look at Denmark.  A large island off the coast of Denmark called Samso Island gets 100% of its power from wind.  This island is home to about 4,000 people, and all of there homes are supplied with electricity from wind turbines.  In the United States, wind power accounts for around 2-3% of our total power, and yet we are one of the leaders in wind power output.  The U.S Department of Energy's Energy Efficiency and Renewable Energy branch conducted a wind resource potential for the entire United States.  They concluded that the U.S has a capacity to produce 36,919,551 gigawatt hours of electricity.  The annual electricity consumption in the U.S in only about 4,119,000 gigawatt hours.  Keep in mind that is just the potential wind energy production, and it would cost a lot to meet that potential.  Wind power is becoming increasingly popular however, and combined with solar and other forms of energy production, the need for fossil fuels will decrease.

Wind Resource Potential Map

Here is a video that takes a look into a wind turbine...very cool, check it out!

VIDEO

All About Solar Energy

With the world's supply of fossil fuels such as coal, oil, and natural gas being depleted, alternate forms of energy production are in need.  One of these forms of energy production is solar energy.  The sun is arguably the biggest source of energy available to us.  It could easily provide us with all the energy we need, and it won't run out anytime soon.  There is only one problem...harnessing this energy.  Right now solar energy accounts for less than 1% of the world's total energy production.  About 85% of this energy production comes from fossil fuels.  Three of the major arguments against solar energy are that energy can only be produced in nice weather, there is no room for solar panels, and its cost.  Looking at the first issue, it is true that solar panels don't work effectively at night or during adverse weather.  However, there are very powerful batteries that can store the energy made during the day so that power can be used at night or during storms.  As for the issue of space, solar panels are bulky.  But think of the Sahara Desert.  It is estimated that an area of 640,000 square km could provide the world with nearly all the power it needs.  The Sahara Desert, one of the sunniest places in the world, spans 9,000,000 square km.  As for the cost of solar panels, they are pricey.  This is mainly because they require large amounts of silicon which is not readily available.  However, this price can be offset with time, as anyone who invested in solar would save money on energy in the long run.

 

After learning more about solar energy, you may ask, how does solar energy work?  Obviously I could go into great detail to answer this question, but I am going to keep it simple.  There are two different types, solar thermal and photovoltaic.  Solar thermal is used to generate heat from the Sun's energy.  I am going to focus on photovoltaic because this is how electricity is made from the Sun.  The solar panels in the photovoltaic method contain silicon (a semi-conductor) based solar cells that absorb the Sun's light.  Being a semi-condutor means the silicon readily donates its electrons.  The energy from the Sun's light "excites" the electrons in the silicon solar cells, creating electron flow or electricity.  This is in the form of a direct current or DC.  This DC power can be stored in a battery.  Since your house uses alternating current or AC power, the DC power has to flow through an inverter to change it to AC.