Electricity demand changes throughout the day as people wake up, go to school or work, cook, heat and cool buildings, and use electronics. A power grid must supply electricity at the same rate that customers use it, so matching supply to demand is essential for reliability. Baseload power covers the steady minimum demand, while peaking power covers short periods of high demand.
Renewable energy machines can help meet both needs when they are combined with storage, forecasting, and flexible grid controls.
Some renewable sources, such as geothermal plants, hydropower dams, and biomass plants, can provide steady output for many hours and are often useful for baseload. Solar panels and wind turbines produce variable power because sunlight and wind speed change, so they often need batteries, pumped hydro storage, or backup sources to match demand peaks. Peaking power is especially important in the morning and evening, when electricity use rises quickly.
Engineers compare demand curves, power ratings, capacity factors, and response times to decide which machines should run at each time of day.
Key Facts
- Power is the rate of energy transfer: P = E/t.
- Electrical energy used by customers is often measured in kilowatt-hours: E = P × t.
- Baseload demand is the minimum power demand that stays present for most or all of the day.
- Peaking power is extra power supplied during short times when demand rises above the baseload level.
- Capacity factor = actual energy produced ÷ maximum possible energy if running at full power all the time.
- Fast-response resources such as batteries and some hydropower systems can change output quickly to balance the grid.
Vocabulary
- Baseload
- Baseload is the steady minimum amount of electrical power that a grid must supply over a long period.
- Peaking power
- Peaking power is additional electrical power used to meet short periods of high demand.
- Demand curve
- A demand curve is a graph showing how the amount of electrical power customers need changes with time.
- Capacity factor
- Capacity factor is the fraction of a power plant's maximum possible energy output that it actually produces over time.
- Energy storage
- Energy storage is a system that saves energy when supply is high and releases it when demand is high.
Common Mistakes to Avoid
- Confusing power with energy is wrong because power is a rate and energy is the total amount transferred. A 2 kW device running for 3 hours uses 6 kWh of energy.
- Assuming all renewable sources are variable is wrong because geothermal, biomass, and some hydropower plants can provide steady output. Solar and wind are variable, but renewables are not all the same.
- Labeling the highest part of the demand curve as baseload is wrong because baseload is the lower steady band that exists even when demand is low. Peaks are the extra demand above that band.
- Ignoring response time is wrong because a power source must ramp up quickly enough to cover a sudden increase in demand. A slow plant may be useful for steady supply but not for fast peaks.
Practice Questions
- 1 A town has a baseload demand of 45 MW and an evening peak demand of 72 MW. How much peaking power is needed during the evening peak?
- 2 A battery can deliver 10 MW for 4 hours. How many megawatt-hours of energy can it supply, and could it cover a 5 MW demand increase for 6 hours?
- 3 A grid has solar panels, wind turbines, a geothermal plant, a hydropower dam, and batteries. Explain which resources would be best for baseload, which would be best for peaking power, and why.