ES1.1 · Storage services and technology selection

Learning objectives

• Calculate the event energy.
• Identify the first failed constraint for each device.
• Specify the next evidence request.

Allow 30–45 minutes including derivations and exercises. All numerical values are teaching assumptions.

1. Define the delivered service

A storage project buys a time-dependent service, rather than an inventory alone. Specify the net power at a named meter, uninterrupted duration, response delay, recovery window and protected reserve. Heating, cooling and electrical backup are different services even when all quantities are expressed in MWh.

2. Follow the conversion chain

Batteries store electrochemical energy; pumped hydro stores elevated water; flywheels store motion. Air storage depends on pressure, temperature and a thermodynamic cycle. Hydrogen and thermal routes require explicit final conversion stages if electricity is the contracted output. Each stage has power and availability limits.

3. Separate energy from power

For constant duty, E=P×t. For varying duty, sum power multiplied by each interval length. Available capacity must be stated at the output boundary after losses and reserve deductions. Passing the energy check does not establish adequate converter current, startup behaviour or voltage support.

4. Screen local constraints first

Hydro needs usable elevation, water and civil works; air storage needs a suitable pressure system and heat balance. Thermal storage needs a compatible temperature service. A battery still needs thermal management, protection and permission. Technology rankings should follow these gates rather than a generic cost-per-kWh chart.

5. Prepare the decision record

Record why each option passes, fails or remains unknown. Keep source dates and operating conditions beside every assumption. When data are absent, create a measurement or supplier evidence action with an owner. Do not turn an assumed retention rate or response time into an equipment guarantee.

Worked answers and reasoning

Attempt the exercises before opening each answer.