How it works


The Prometheus Gas Turbine uses a very powerful (centrifugal) compressor to drive the turbine of an generator. See picture 1. Normally it drives the turbine of an generator directly. See picture 2.

Picture 1 - Concept Prometheus Gas Turbine
Flowchart Prometheus gas turbine powering centrifugal compressor

Potential efficiency example


This Prometheus Gas Turbine example is based on the off the shelf SPCP  pipeline compressor package by Siemens, which consists of the SGT-400 gas turbine and STC-SV centrifugal compressor. See "Sources and technical details" section at the bottom of the page for more technical details.

The SGT-400 gas turbine driving the STC-SV centrifugal compressor (picture 3) consumes about 37 MW. In power generation it can drive a 13 MW generator. The STC-SV centrifugal compressor's maximum flow rate is 133 kg/s and its maximum discharge pressure is 1000 bar. For instance for nitrogen, which has almost the same weight and density as ambient air, the compressor discharge pressure is 900 bar.

Picture 2 - Siemens SGT 750 gas turbine Picture 3 -  Siemens SPCP  pipeline compressor package
Diagram Siemens SGT-750 gas turbine Flowchart Siemens SGT-400 gas turbine powering STC-SV compressor

A comparison of picture 2 and 3 shows that the STC-SV compressor's air flow in picture 3 is almost 20 kg/s larger than the air flow of the SGT-750 gas turbine in picture 2, and its discharge pressure is about 37 times the compression ratio of the SGT-750 gas turbine. The temperature of the STC-SV compressor's air flow is lower (about 550 Celsius vs 1150 Celsius).

Why generating 36 MW might very well be feasible

> The larger air flow - 133 kg/s vs 113 kg/s. - Note: the gas stream of the SGT 750 gas turbine also has to drive turbines of the compressor (average back work ratio is ± 50 %)
> The high discharge pressure - 900 bar vs 24 bar This is too high, no turbine can handle this pressure. However, the pressure can be reduced by using an Venturi . The ejector which will bring down the pressure of 900 bar to an intermediate pressure of e.g. 100 bar, at the same time it sucks in air and increases the air flow from 133 kg/s to e.g. > 170 kg/s. To prevent the air sucked in by the ejector from cooling the air flow from the STC compressor, it is lead through an heat exchanger (heated by the exhaust gases from the SGT 400 gas turbine flow). See picture 4.
> Although the temperature coming from the STC-SV compressor is only 50% of that SGT 750 gas turbine, it should be sufficient. A temperature of ± 600 C is enough for gas turbines of future ACAES plants. See picture 5, which shows the flow chart of a prototype ACAES plant.
   
Picture 4 - Prometheus Gas Turbine

Flowchart Siemens SGT-400 gas turbine and Siemens STC-SV centrifugal compressor powering a 36 MW generator

Picture 5 - flowchart prototype AA CAES power plant

Example of a Advanced Adiabatic Compressed Air Energy Storage plant
Image is a screen shot from this adiabatic compressed-air energy storage (ACAES) paper (direct pdf file download)

Potential energy savings


Almost 98% of the fuel the SGT-400 gas turbine consumes is converted to electrical energy!

About 56 MW of fuel is saved per hour! (The Siemens SGT-400 consumes about 37 MW, the Siemens SGT-750 consumes 93 MW).

NB: The example is based on existing off the shelf hardware, meaning a specifically designed compressor should be more efficient.

Environment


The Prometheus Turbine is very fuel efficient. This postpones Peak Oil, makes it less profitable to drill in the Arctic for oil and gas, use hydraulic fracturing and nuclear fission.

Running on biofuel, makes it very environment friendly and the Prometheus Gas Turbine could very well be the backbone for a solar and wind power based grid. If it is to run on biofuel, there is less surface needed to grow it, minimizing the risk of a lower food production.

Might also work in concentrated solar plant like Ivanpah, in a solar Brayton cycle, and in the more distant future with hot nuclear fusion or even LENR (cold fusion).

Feedback


Good idea, bad idea? Has already been done? Want to help/invest? Please feel free to email or tweet your feedback or questions.

Sources and technical details


Siemens SGT-400 gas turbine specifications Siemens STC-SV centrifugal compressor specifications
Screen shot brochure specifications Siemens SGT-400 gas turbine Screen shot brochure specifications Siemens STC-Sv centrifugal compressor

Siemens SGT-750 gas turbine specifications


Siemens gas turbine compressor package (pdf file)

Gases densities

Industrial gas turbines by Siemens (pdf file)

Back work ratio in gas turbines explained
 
AA-CAES Explained

ADELE - Adiabatic compressed-air energy storage