Grid Balancing
Supply and Demand
Must be very well balanced on grid failures occur.
Grid Frequency
Changes in the frequency of the grid indicate imbalances of supply and demand.
In the US, the grid operates at 60Hz. Frequency deviations as small as 0.3 Hz can trigger blackouts to avoid damage to the grid.
Load Following
Grid control strategy that views the electrical demand or load as fixed and adjusts the supply to meet demand.
Supply Following
Grid control strategy that recognizes that renewable energy sources fluctuate and schedules demands and loads that could be deferred to times when energy is available.
- Cars often charged at night, charging during the day would use solar peak
Baseload Supply
Energy generation sources that are most economical to run nearly continuously.
Load-Following Supply
Energy generation sources whose output can be raised and lowered to match the load or demand.
Peakers
Energy generation sources that are only used when the power demand hits very high (peak) levels.
Spinning Reserves
Energy sources that are ready to provide power to the grid on demand.
Frequency Regulation
Grid services that can be deployed to bring the grid frequency back into the desired range.
Demand Response
Strategies to adjust the demand (rather than supply) to respond to grid imbalances in supply and demand.
Diurnal Load Variation
The observed daily fluctuations in power demanded from the grid due to human activity.
Duck Curve
A sharp increase in demand occurs in the early evening as folks return to their homes. At the same time, the amount of solar electricity available is sharply decreasing. This creates a need to bring lots of power online quickly which is very challenging for grid operators.
Transmission Constraints
Even if adequate supply exists to meet demand, it may be impossible to deliver the power if the necessary transmission lines are at their capacity.
Demand Exercise
- Choose an academic building and dorm on campus
- List the likely electrical demands for those buildings
- List the times when those demands are likely to occur
- Sketch a graph of the demanded power versus time
Supply Exercise
- Imagine a solar plant and a geothermal plant
- Sketch a graph of the power supplied versus time
Balancing Exercise
- Imagine a demand from your campus buildings
- Sketch a graph showing how you would meet this demand with the supplies you sketched above