What is baseload?

Baseload is the part of electricity demand that never goes away, even in the quietest hour of the night, together with the type of power plant that supplies it. These plants run almost continuously because their fuel is cheap per unit and they are costly to switch on and off. Knowing the baseload tells planners how much steady supply the grid needs.

How it works

Demand on a grid follows a daily curve, low overnight, rising in the morning and peaking in the evening. The lowest point of that curve is the baseload. Plants such as nuclear, coal and large hydro have high fixed costs and low running costs, so they earn their return by running as many hours as possible near full output.

The trade-off is flexibility. A plant built for steady output is slow to ramp up and down, so when a lot of wind or solar arrives and pushes the remaining demand below the baseload, there is a conflict. Either the steady plants must reduce output at a loss of efficiency, or the surplus must be stored, exported or discarded.

Example

Say a region's demand ranges from 400 MW at 4 a.m. to 1,000 MW at 7 p.m. The baseload is 400 MW. A 400 MW nuclear plant running all 8,760 hours of the year produces 400 x 8,760 = 3,504,000 MWh. Now say a solar farm adds 300 MW at midday, when demand is 700 MW. The remaining demand for steady plants falls to 400 MW, which is still at baseload. But if the solar farm grew to 500 MW, the remaining demand would drop to 200 MW, below the plant's output. This is an illustration.

How to model it in Machinations

Use a Register to produce a daily demand curve from the step number. A Source for the steady plant outputs a fixed rate, and another Source for solar follows a daytime pattern. A Pool collects any surplus and a Drain removes demand. Make the solar capacity a Lever, then Play over several days and chart the surplus.