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Fossil energy use is increasing. This will cause climate change and it already changed some. Some of institutions are neglecting this change but it will take its action pretty soon. Beside those, energy sector is growing everyday more and more. And the fossil fuel part is making really good amount of money.
There are many advantages of using fossil energy
1. You can have a big capacity in a single location to generate giant energy.
2. A fossil fuel based power plan can built on any location. Transportation also will be faster and easier, therefore it is always easy and faster to find the fuel.
3. Especially coal sources are too many on earth. This makes it a lot cheaper than other energy sources.
4. A power plant can run very efficient with gas.
There are also drawbacks using of fossil fuel
1. When they burn carbon dioxide occurs and this is the major disadvantage of fossil fuel, is the pollution. If you are using coal additiaonally you will produce sulphur dioxide which causes acid rains.
2. Coal based power stations use a lot of coal; therefore they need their reserves near them. This also means environmental pollution.
3. Gas based power stations can spread bad odors into air.
4. Crude oil based power plants can cause big environmental pollution because of the oil spills during the transportation, also you burn crude oil it contains toxic chemicals and this is the one of the biggest problems on earth.
The renewable energy sources are open wide range than anything else. It’s the clean energy; however it does not mean that it won’t bring any pollution to us. Yes there is pollution when you built a renewable energy system to generate power. How that happens? It is simple. For example: Let’s assume that we are going to build a wind power generator. Simply for the manufacturing of blades we might use PVC, fiberglass etc. Let’s use the most popular one which is fiberglass. Fiberglass production will produce emissions of toxic air pollutants, and it will also contain styrene. It is present in resins and gel coats. Some styrene evaporates during curing process. There will be paints; thinners etc. and those are also releasing toxic air. What you understood is correct and we know now that renewable energy systems cause environmental pollution too. It might not be significant amount as fossil fuel energy but it still does.
Moreover, it is not free like some people think. When you want to use renewable energy you will need funds:
1. To make the system, or to purchase.
2. To build the system.
3. Maintenance as manufacturer instructed.
4. To replace broken parts.
5. To purchase or lease significant size of land.
Land is the very cost effective one. Unless-otherwise manufacturer instructed, in a wind farm there should be 5 rotor diameters space between each wind turbines. If you do less than 5 you might lose the efficiency (less spacing requires approval by the turbine supplier), then your investment will NOT eimburse the amount you expected.
Table 1.1 Rotor Size and Maximum Power Output. Danish Wind Industry Association, American Wind Energy Association
You will need large size area to build your wind farm. Example: Let’s use 72 meters rotor diameter and power output will be for this size approximately 2000 kW, Table 1.1.
It is really variable from power plant to power plant but just an example that the five-unit, 2,040-megawatt Four Corners Power Plant, located on the Navajo Indian Reservation west of Farmington, New Mexico, is operated by APS. Fueled by low-sulfur coal from the nearby Navajo mine, the plant is owned by APS and five other utilities in the Southwest. APS' stake in Four Corners makes 782 megawatts of energy available to the APS system, Picture 1.1.
Picture 1.1 Four Corners Power Plant
Let’s go back to power output of each wind turbine and space it takes. And each unit for Four Corners Power Plant is generating approximately 400,000 kW. When one fossil fuel operated unit generates 400,000 kW the other wind turbine generates 2000 kW. Fossil fuel based 200 times more than wind power.
Wind energy generation is not that simple and cheap. There are options to solve or reduce those issues we are receiving from the wind energy generations. We can even reduce the pollution we are creating by manufacturing of the fiberglass wind turbine blades. There are techniques to do that.
Those techniques are:
1. If the manufacturing uses open molds switch them to closed molds.
2. Install impregnator systems that combine resin and fiber application.
3. Use computerized manufacturing, therefore you don’t waste and redo. Redoing is more pollution.
4. Use less styrene contains resins and gel coats.
5. Use ultraviolet-cured or vapor-suppressed resin, because these resins have the potential to emit less styrene.
How we can eliminate pollution from the fossil fuel burning to generate power? It is very hard since burning will occur on earth. There is some filtering systems but they work up to some point since pollution creating level is really high. Continuing to build new wind farms will definitely help to decrease environmental pollution.
Table 1.1 mentions about wind generators power output. The large turbines usually generate the maximum power at 15 meters per second (33 mph) wind speed, this called rated wind speed. And also this is their rated power generating wind speed which calculates from the rated wind speed; therefore this rated power will be the maximum power you can normally receive from the wind turbine. Rated power is usually confusing with power output. Power output can be anything, it is depends on the current wind and conditions.
Wind speed vs. energy generation is not linear. Power incensement is the cube factor of speed incensement. For example: If wind occurs at V speed, and increases to 2V then power (P) incensement will be 23= 8 times. This doesn’t mean wind can go higher speed as much as it can and power will increase infinitely. Normally large size turbines set to 20 meters per second (45 mph) to shut down because of the safety system. Some turbines might go up to 36 meters per second (80 mph). Typically more than 36 meters per second (80 mph) does not called safe.
There are several safety systems those to shut down the system to prevent wind generating electrical and mechanical components from the damaging. Excessive wind speed might put the system in danger. Shutting of the system at dangerous wind speed called Cut-out Speed. For severe wind speeds there are a couple of ways to activate the shut down system. The one of them uses basic vibration sensor which actually consists of metal ball attaching to the chain, poised on a tiny pedestal. When turbine starts vibrating more than the limit defined, the ball falls off the pedestal and pulls the chain to start the shutting down the system. The most popular one is using a breaking system. At the severe wind speeds a power-control system activating the breaking system when wind speed goes more than the limited wind speed, e.g. 20 meters per second (45 mph), and when wind speed drops under the limit power-control system will release the break to operate the system for electric generation.
There are modern ways also to prevent severe winds to damage the wind power generator. The most of the current wind turbine generator manufacturing uses modern ways.
1. Blade Pitch Control: Basically blades rotate individually to control the wind power. If the wind becomes severe then power generating increases and a Power-Control Monitoring System sends the signals to rotate the blades to let the wind go through the blades, and tilt rotor moment decrease; therefore rotating speed can be reduced to keep system still generating the power safely. If the power level goes lower, it rotates back to the optimal angle of attack of the blade's airfoil. The newest technology is to rotate each blade individually; therefore you can more sensitively set the system to generate the power exactly you want.
Blades rotating system can build from
a) Electrical motor mechanical gear system which includes PITCHmaster Controller and Electric Servoactuator.
b) Hydraulically Blade Pitch Control works with Axis Control Valve and Hydraulic Actuator. This one is the most popular one because of the reliability. Blades rotated by pistons.
2. Passive stall control: In this type of design, when severe winds occur the rotor airfoil profile is aerodynamically designed to prevent rotating faster than projected RPM. It twists to create aerodynamic stall; therefore turbulence starts to stop rotating the blades. 60% of the installed wind turbines are using this type of controlling designs. It doesn’t require too much maintenance since the main idea of the design coming from the aerodynamic rules.
3. Active stall control: Usually very large wind turbines use this mechanism. It is very similar to blades pitch control system. A power-control system will be used. After turbine reaches it’s projected rated power, the system pitches blades opposite way of blade control system does, it increases the angle of attack to create stall position. Hence, laminar flow stops, blades rotating decreases and wind turbine will reduce electric generation.
There are number of Engineered Safety Features (EFSs). A wind turbine it is like any other engineered product; therefore reliability, safe and beneficial operation is must.
The shape of the wind turbines designed aerodynamically to generate maximum power. Average Annual Wind Speeds are different at everywhere. When selecting a tower you should analyze your Geographical Wind Resource to figure out the right tower and right installation to reimburse the money you spent. Otherwise you will waste your money. You might need an expensive installation or you might not need it. You should first start to figure out the rated power you are looking for.
Coastlines are the best locations for wind power. If you are not located near the coastlines higher elevation locations will be the choice. If your location even doesn’t have high elevation for the installation then you will have to pick higher towers to install your wind power generator. When you install even large size wind turbines they work better because their blade’s lengths are longer; therefore they can reach higher altitude to get the better wind power. Ideal height for good wind power is 40 feet to 350 feet. If you pick more than 350 feet your reimbursement graphic against to time will drop down dramatically. Effective wind power not only depends on wind speed also depends on the air density. Air density is always higher at lower altitudes, also higher at the cold temperatures. A hot air balloon rises because of this density differences. This is confusing for most of people that pressure goes up for the hotter air but there is nothing to create powerful wind with it. Their kinetic energy is higher than cold air molecules, they move faster individually and this creates more pressure. The main reason winds occur is the temperature differences between the areas. Also earth’s rotation is effective since air is above the earth. Figure 1.1 assuming that 5 air molecules are hitting to the blades with the F force. We have total 5F to push the blade. If you install your wind turbine with higher tower then better wind force you might catch but if you install it too high then density will go down and you might not have more wind speed to receive the better wind power than before. An airplane can move faster at the higher altitudes than lower altitudes with the same engine power. Air density goes down at higher altitudes, air is more thinner, and accordingly lifting force decreases but speed takes the place; therefore quantity of hitting molecules to the wings will stay the same and airplane can hang in the air with the same force on the wings (gravity differences between the different altitudes are neglected). All of those tell that finding right location for your wind turbine is extremely important. A wind farm design requires a lot of research about the area. You will have to select your wind turbine according to your land’s wind power availabilities.
You also need knowledge of basic wind calculations of wind energy for your economic impact. The kinetic energy of the wind will be transferring to wind turbine blades; air molecules will be pushing the blades. This will be totally a kinetic energy transfer and this energy will be using for power generating. PART 2
Yunus Topcan
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