Why Water and Wind Are Complementary
Here are a few key concepts to help us understand
why water and wind are complementary.
Installed capacity
Total generating capacity of the units in a facility (e.g., a wind farm or hydropower plant). Expressed in MW (millions of watts).
Water
A hydropower plant with two generating units of 50 MW each has an installed capacity of 100 MW.
Wind
A wind farm with 50 wind turbines
of 2 MW each has an installed
capacity of 100 MW.
units X 50 mw
= 100 MW
= 100 MW
Firm capacity
The capacity that can be made available with a predetermined level of reliability. It’s very important for an electric utility to be able to count on firm capacity, because electricity must be generated just when the customer needs it.
Water
The capacity of a hydropower plant can easily be guaranteed, because the quantity of water sent through the turbines can be controlled at all times.
A hydropower plant with an installed capacity of 100 MW has a firm capacity of nearly 100 MW, since generating units seldom break down.
Wind
There is no guarantee that the wind
will blow when electricity is needed.
That is why, Hydro-Québec has determined, based on statistical and meteorological studies, that during periods of peak demand on the power grid, wind farms as a whole can contribute 35% of their installed capacity.
= 100 MW Firm
Capacity
= 35 MW Firm
Capacity
Electrical energy output
This is the power generated by a facility (i.e., wind farm or hydropower plant) multiplied by the number of hours during which that power is delivered.
Power X Number of hours = Energy
For example, a hydropower plant or wind farm that generates 100 MW for one hour on a continuous basis produces 100 MWh (megawatthours) or 100,000 kWh (kilowatthours) of electrical energy.
However, no generating facility can operate at maximum capacity all the time, since allowances have to be made for maintenance, equipment failure and energy source availability. To determine a facility’s real energy output, you need to consider its annual load factor, that is, the ratio between its actual electrical energy output in a given year and the energy that would have been supplied had the facility been operated continuously at maximum capacity throughout the year. This ratio is usually expressed as a percentage.
Water
A hydropower plant with an installed capacity of 100 MW and a plant load factor of 65% (average load factor for Hydro-Québec's generating fleet) has an annual energy output of 569,400 MWh.
Wind
A wind farm with an installed capacity
of 100 MW and a load factor of 35%
(estimated average for all wind farms currently in operation) has an average annual energy output of 306,600 MWh.
Kilo, mega, tera?
| Prefix/Unit | Symbol | |
|---|---|---|
| watt | W | = 1 watt |
| kilowatt | kW | = 1 000 or 103 watts |
| megawatt | MW | = 1 000 000 or 106 watts |
| gigawatt | GW | = 1 000 000 000 or 109 watts |
| terawatt | TW | = 1 000 000 000 000 or 1012 watts |
The same prefixes are used for watthours, volts and amperes.
Power vs. energy
Power
The capacity to do work. In the field of electricity, the units of measure for power are the watt (W) and its multiples: kilowatt (kW), megawatt (MW), gigawatt (GW) and terawatt (TW).
Energy
Power multiplied by the period of time during which the power is used. In the field of electricity, the units of measure for energy are the watthour (Wh) and its multiples: kilowatthour (kWh), megawatthour (MWh), gigawatthour (GWh) and terawatthour (TWh).
Your electricity meter measures the energy or kilowatthours consumed, and this is what you are billed for.
- A 1,000-W hairdryer working for 1 hour consumes 1 kilowatthour of energy. 1,000 W (1 kW) X 1 hour = 1 kWh
- A 200-MW hydropower plant can generate a maximum of 200 MWh or 200,000 kWh in one hour.
Load factor
