Symbiotics | A New Generation of Hydropower

Electricity Facts

Generating Electricity

  • Generating electricity is relatively simple:
    • An electricity generator is most simply an electric motor in reverse—i.e. instead of applying electricity to the motor to produce rotating mechanical shaft energy:
    • The simplest way to generate electricity is to produce rotating mechanical shaft energy to spin a turbine attached to a shaft which will drive the generator:
    • There are four major ways to spin a turbine:
        1. Use a natural gas turbine, where natural gas is burned and the hot exhaust is directed through a bladed turbine which drives a shaft.  An example of this is a jet engine, where the hot exhaust from burning jet fuel (actually high grade kerosene) drives a turbine. We see this turbine spinning in the jet engines of commercial airliners.
        2. Use a steam driven turbine, where treated water is boiled to steam and the steam is contained in high pressure pipes until directed onto a turbine. There are six ways to boil the water to raise steam.
          1. Burn coal and immerse the high pressure steam pipes in the flames from the burning coal, much like roasting marshmallows.
          2. Burn natural gas and immerse the high pressure steam pipes in the flames from the burning natural gas, again much like roasting marshmallows.
          3. Burn an alternate fuel and immerse the high pressure steam pipes in the flames from the burning alternate fuel, again much like roasting marshmallows. The alternate fuel could be residual fuel oil, biomass, wood, wood chips or animal dung.
          4. Bury the pipes deep in the earth and allow the earth’s natural volcanic heat to boil the water.  This is geothermal energy.
          5. Construct a nuclear reactor and use the heat from the radioactive pile to boil the water and raise steam.  This is nuclear energy.
          6. Use the waste heat from an existing process to heat the water in the pipes.  This is co-generation.
        3. Use a wind driven turbine on a wind mill.  This is wind energy. Wind energy can be on-shore or off-shore.
        4. Use a water driven turbine.  This is hydro power. There are four major forms of water power.
          1. Run of River where a free-flowing river or canal is contained by a dam or diversion structure and the ‘head’ of water behind the dam or diversion structure is selectively released to flow through a turbine to generate electricity. The water is then returned to the river or canal.
          2. Tidal Power where an incoming (rising) tide is contained behind a structure. The contained water creates a head of pressure. The contained water is run through a turbine and returned to the main body of water.
          3. Wave Power where the energy provided by the natural rising and falling of water waves in a lake, bay, or ocean is converted using a mechanical device.  The mechanical power created from these systems either directly activates a generator or transfers to a working fluid, water, or air which in turn drives a turbine/generator.
          4. Pumped Storage where water from a natural body of water (a river or a lake, the lower reservoir) is pumped to a man made upper reservoir using electricity purchased during periods of low electricity demand. Then during periods of high electricity demand this water is recycled back to the lower reservoir, driving a generation turbine in the process.

            The process works like a large storage battery, storing energy to be used when it is more needed. Pumped storage is hydropower, just a highly engineered form of hydropower. Rather than using coal or natural gas as fuel to generate electricity, pumped storage uses purchased electricity. Pumped storage is one of the most efficient forms of electricity generation:
            1. Coal fired plants have efficiency factors below 50%; most of the energy contained in coal is wasted and not converted into electricity.
            2. Combined cycle natural gas fired plants may have efficiency factors as high as 75%; more of the energy contained in natural gas is converted into electricity.
            3. Pumped storage plants have efficiency factors of approximately 80%; while some electricity is wasted, pumped storage is among the most efficient ways to generate electricity. Coupled with pumped storage’s ability to convert low value off-peak electricity into high value on-peak electricity, it can be seen that pumped storage represents a key tool in the energy arsenal.
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