Storing Work¶

So far, we have explored multiple ways to produce and use work for sustainability. In Module 1, we analyzed how work can separate CO₂ from flue gases. In Module 2, we saw how chemical reactions drive electrical work in fuel cells. Here, in Module 3, we examined how geothermal heat can be converted into useful work.

But what happens when work is produced but not needed immediately? The Earth’s heat flux is constant, yet electricity demand spikes in the evening. To balance supply and demand, we need ways to store work for later use.

Phase Transitions in Energy Storage¶

Batteries store energy by leveraging phase transitions, but unlike water phase changes, which vary with temperature and pressure, battery materials store energy by changing chemical composition while holding temperature and pressure constant.

This difference introduces new thermodynamic relations. Instead of liquid-to-gas transitions, batteries rely on ion intercalation, where lithium ions move between electrodes to store and release energy. Understanding these composition-based phase changes requires a new framework, which we will develop in Module 4.