My curiosity on wind power has been sparked again, and I really wanted to understand what makes this idea so NON-cost-effective. Wind turbines are springing up more and more, yet you still hear the complaint that there's not quite the ROI as desired. Looking at some comparison charts of wind turbine sizes, I noticed (with actual conscious interest this time) that they were categorized in terms of kWs or MWs (and just to be super clear kW = 1000 watts and MW = 1 million watts). So, I asked myself, what do those numbers really mean? Is it saying it's producing a certain amount of power....or a certain amount of energy? And what is the difference between power and energy anyways? A shameful question I must admit for someone who's probably aced all the tests on the subject when the info was fresh in the brain. But like many others I've encountered, no matter how much we study that chapter on electricity, we leave with the same amount of fog we entered with. Well, let's try and lift that fog once and for all, so we stop doubting ourselves and sounding ignorant when really talking about energy. I originally set out to look deeper into this issue of size vs. cost. vs. energy output, but first I needed to step back, waaaaay back to understand the basics. Back we go to high school physics.......
The most basic formula being:
First off, let's define what each item actually is:
ENERGY: a measure of HOW MUCH fuel is contained within or used by something over a specific amount of time. (kWh, Joule, Calorie, BTU, Therms....)
POWER: the RATE at which energy is generated or used. (J/s, W, kW, MW.....)
Read them again. Notice the differences? Energy is like talking about miles while Power is like mph. Amount vs. rate. Got it?
But let's look a little closer into energy, then we'll tie that back into power. Now, energy, as you know, comes in many different forms, cannot be created or destroyed, but can be converted. So it's a bit misguiding to say you've 'used all the energy' when in fact, it's merely been converted into some other form that is no longer of use to you.
Below you will see a list of different kinds of energy and some examples of conversion:
Electrical
Mechanical
Chemical
Thermal
Radiant (electromagnetic Radiation)
Nuclear
Magnetic
Elastic
Sound
Light
Mass (E=MC2)
Thermal energy --- into ---> Mechanical Energy --- via ---> Steam Turbine
Chemical energy --- into ---> Thermal Energy --- via ---> Fire
Electric energy --- into ---> Electromagnetic Radiation --- via ---> LED
Electromagnetic Radiation --- into ---> Electrical Energy --- via ---> Solar Cell
Electricity is one of the major items we think about in terms of energy, but electricity is measured in volts. How then, does this translate into, let's say, an 800kW turbine?
To do this, we first need to understand the components of electricity. Like water in a hose (the electrons in a wire) there is a pressure [volts (V)] pushing the water through which creates a current [amp (I)]. If you have something trying to slow down your flow of water, you then have a resistance [ohm (Ω or R)] in the current. With these items and a little thing called Ohm's Law, you can now calculate a watt!
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| Think of electricity like water flowing through a hose. |
Power (Watts) = Voltage * Current
P = V * I
Remember, power is a RATE, and to measure the electrical power (P) of something the Watt (W) is used as a nice abbreviation for the RATE, J/s (joules/second) or (energy/time). But then you say, hey, how do you get J/s from the equation Volts * Amps? I'm not going to go into that here, just trust that it works that way (or see yourself how the conversion works). All you need to remember is that Volts * Amps = Watts, and that Watts is a RATE of energy usage.
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| You can use these triangles to help you remember what calculations give you certain variables. Simply cover one letter and the other two's position within the triangle will give you the calculation you need. |
So back to our 800kW wind turbine. This number is telling us the rate at which electric power is being produced. NOT the amount of power, but the RATE (again, think of mph). If this is its rate at full speed, then at no speed, you now have a 0kW turbine (just like if your car stops, you are then going 0mph).
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| 800kW vs. 0kW |
But we want to also know how much ENERGY is being produced from this. And this is where we introduce Mr. Power to Ms. Time. With these two together, we can create little energy babies.
Energy = Power (or Watts or J/s or RATE) x Hours (Time)
E = W * h............. = Wh
(first comes love, then comes marriage, then comes Wh in the baby carriage....horrible, right? but doesn't 'Wh kinda look like the sound a baby makes? ' Waaaaaaahhhhh)
Therefore, we can say that for an 800kW turbine running for 2 hours, it can produce 1600 kWh of energy. And THIS, the kWh, is how utility companies charge you for electricity.... those sneaky guys.
For example, if you are running five 100W light bulbs in your home for 8 hours each and electricity is charged at $0.07 a kWh, then it will cost you....
5*100W = 500W = .5 kW
.5kW * 8 hours = 4.0 kWh
4.0 kWh * $0.07/kWh = $0.28
Ok, that was a lot of variables all at once, but hopefully the fog of energy vs. electricity vs. power vs. W and kWh and how you get charged on your electric bill has been lifted, and we can all move on to more exciting things...like perhaps my original ponder about the cost effectiveness of wind turbines in general or any other energy producing (or more correctly put, converting) apparatus. More on this to come.....
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