Exergy

Exergy is a type of energy that can do work. It is also sometimes called "available energy" because it is possible to use it to do things like turn a wheel or fill up a car. Imagine a pool of water. The water in the pool has some energy inside it, but it can't do any work because it is just sitting there. If we drain the water out of the pool and use a pump to turn it into a powerful stream of water, we can use the water to turn a wheel or power a car. This is what exergy can do, it takes existing energy and makes it useful for doing work.