Combined gas and steam

Imagine you are making breakfast, and you need both your toaster and your microwave to make your toast and egg. The same thing happens when we make electricity. We can use different machines to make electricity, and sometimes we use more than one to make it more efficiently.

Combined Gas and Steam (also known as a Combined Cycle) is when we use two types of machines to make electricity. The first machine, called a gas turbine, burns gas (like the stove in your kitchen) to make electricity by spinning a generator. However, burning gas can be noisy and produce a lot of heat, which we don't want to waste.

This is where our second machine comes in, called a steam turbine. It's kind of like a big kettle or pot that boils water to create steam, which then spins a second generator to make even more electricity. But where does the steam come from?

The hot exhaust gases that come out of the gas turbine are incredibly hot, and we want to use that heat to make steam. We pass those gases through something called a Heat Recovery Steam Generator (or HRSG for short) which is kind of like a giant pipe filled with water. As those hot gases travel through the pipe, they heat up the water and turn it into steam, which can then power the steam turbine.

By using both the gas turbine and the steam turbine together, we can make a lot of electricity from a single source of gas. This method is efficient because we are using the heat that would normally be wasted from the gas turbine to make more electricity with the steam turbine. So it's like using both your toaster and your microwave to make breakfast instead of just one.