Not Your Average Solar Gas Turbine

A Solar Pulse Gas Turbine works like the average solar gas turbine used in concentrated solar power plants. If you are not familiar how solar gas turbines work click picture 1.

What sets it apart from the average solar gas turbine, is the way it tries minimize pressure drop. Pressure drop is caused by air having to travel through > 4 meter long solar receiver tubes or receivers made of ceramic foam or "porcupine" ceramics.

Picture 1 - How does a solar gas turbine work?

How does a solar brayton cycle gas turbine work?

How it works

First, the pulse valve in front of the turbines driving the compressor and generator is closed. See picture 2.

Picture 2 - The Prometheus Solar Pulse Gas Turbine

How to reduce pressure in solar gas turbines

Next, the starter engine turns the compressor until the tubes running through the solar receiver are completely filled with compressed air and are fully pressurized to the designated compression ratio, e.g. 20 bar.

The moment the pressurized air has reached its designated operating temperature, e.g. 1100 C, the pulse valve is opened and the hot pressurized air expands in the turbines, driving the compressor and generator.

The pulse valve is opened and closed e.g. 500 times per second, creating "air pulses" or "air detonations", basically so fast that, at least from engineering point of view, it forms a continuous air flow (somewhat resembles the working of a Pulse Detonation Engine).

Interrupting the air flow has some advantages:

Some of the kinetic energy of the "air pulses" is stored in the rotating turbines/compressor (like energy is stored in flywheels).

Therefor, an "air pulse" only has to "hit" the turbines the moment the energy stored in the turbines / compressor from the previous "air pulse" is about become to weak to power the turbines/compressor. Less air is needed for delivering the same work.

This means the compressor will turn at full speed, and pump slightly more compressed air into the solar receiver tubes than is exiting at the pulse valve.

Because the solar receiver tubes were completely filled with fully pressurized air at the start of the cycle, and more air is entering the solar receiver tubes than is exiting, the pressure inside the solar receiver tubes is likely to stay very near the designated compression ratio, e.g. 20 bar, reducing the pressure drop to the lowest possible level.

If this works, overall efficiency should improve because it would make it possible to heat air over a longer distance (increasing the temperature of the air), and doing so without any or very small loss of pressure.

Feedback appreciated

Please, feel free to tweet or email your thoughts.


This page is a work in progress. Hope to add more information soon.