KK Anasyfa Yenilenebilir Enerji Kaynakları Depolama Yöntemleri,
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STORAGE METHODS for RENEAWBLE ENERGIES: SOLAR and WIND -Section 1-
From the point of energy generating systems, sun light and wind are unstable sources. The energy capacities entirely depended to environmental factors. Environmental factors that is atmospheric events, can alterate in little time intervals. The following graphs explain better what I say.
WHY STORAGE ?
As can be seen from above graphs, the amount of generated energy in solar and wind power plants, changes instantly. Because these instant changes threaten system stability, effective use of energy sources and supply-demand regularity; the storage of generated energy bocomes an obligation.
Hydro energy (Water in dams), bio-mass, conventional fuels can stored before electric generation. This sense is not acceptable for solar and wind energy. Solar and wind energy is first transformed to electrical energy and then stored by transforming a desired energy form.
STORAGE METHODS
There is no wonderfull storing method with its all properties. It is not possible to say, that's the one. Storage method differ with size/volume and technology as to necessity, use area and demand characteristics.
BASIC STORAGE METHODS
-Hydroelectric Plant with pumping
-Compressed Air
-Flywheel(inertial) Energy Storage
-Lead Acid Battery
-Lithium İon Battery
-Nicel Cadmium Battery
-Nicel Metal Hybrid Battery
-Super Capaciter
Hydroelectric Power Plants with Pumping
In some hours in the day when the demand(electricity-energy) is low, the water is pumped to a high reservoir and then in the time that the demand rises, the stored water is flowed to the turbines in low reservoir and consequently electricity is generated.
These plants have 60-80 percent efficiency. The efficiency is determined by the quality of set up equipment.
First Hydroelectric power plant by pumping is established in 1890 in Italy and Switzerland.
The power of these plants rises to 150 MW totally in forty countries in the world.
The Japanese has the main capacity with 23.668MW. In these plants it is a focused topic to change the fresh water sources with sea water.
Advantages
-Large apply area
-Can be used in high power and energy levels.
-Fast start up
Disadvantages
-Limited with geographic factors.
-Distance to demand centres. (consume where you generate)
-Set up time and initial cost
Compressed Air Stored Electric Power Plants
Like in previous plants with pumping, the air is compressed with high pressures 40-70 bar to natural spaces/cavities, retired mines or into tanks, in the times that demand is less and electricity is cheap. When the demand rises, this pressurised air is flowed to the gas turbine and electricity is generated.
The gas turbine used in this method is the improved one of the existing gas turbine technology.
In the plants that electic generation is with only natural gas, nearly 2/3 of energy is used to pressurise air.
This means that total energy generated with pressurised air and ntural gas is three times then only with natural gas.
In the World first in Detschland in 1978, 290 MW powered compressed air plant is established by using dissolved salt caverns.
Advantages
-Fast start up
-Easy mechanical system
-Long work life as to battery technologies
-Low initial cost then Hydroelectric plant with pump.
Disadvantages
-Needs fossil fuel natural gas
-Geography of area should be convenient to establishment.
-If the storage is desired in tanks, initial cost rises highly.
Flywheel (Inertial Storage)
The flywheels stores the energy in kinetic form then this energy can be transformed into electrical power.
We can say, the flywheel is a mechanical battery/storage element. Flywheel is a mass, turns around an axis, the capability of energy storing, increases with mass. (Exactly with inertia that is combined with amount of mass and location-geometry of mass)
Flywheels are convenient for storing in short times (less than 1 minute) but this technology is in the beginning presently. These systems are convenient for storing low amount of energy in short times rather than high scaled energy storage.
Advantages
-Fast start up, fast discharge/transfer
-Low maintenance cost. Less times of maintenance than other batteries.
-High efficiency
-Very effective method to stabilise the power quality
-Unlimited charge/discharge - Endless times of storing kinetic energy.
Disadvantages
-Should be used in closed container.
-Revolutions per time changes as to energy transformed.
-Sensitive engineering equipment is needed.
-High cost.
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