Anax-Star Turboexpander

the most efficient natural gas letdown generator on the planet 

How does it work?

The ASTE harnesses wasted energy in natural gas regulating stations to generate clean electricity. This venture represents the first step we’ve taken on our mission of reducing the use of fossil fuels, by doing more with less.

An innovative, efficient addition to existing infrastructure, the ASTE provides utilities, energy-intensive manufacturers, independent power producers, universities, and many other organizations with the opportunity to profit from this groundbreaking technology.

We’ve built the ASTE to maximize performance, safety and efficiency while, at the same time, minimizing cost and maintenance.


Natural Gas Parameters

The ASTE is designed to operate at gas inlet pressures from about 350 to 1,100 psig, with at least a 250 psig pressure reduction. In order to achieve the 250 kW power output at these pressures, gas throughput must be between 6,000 and 25,000 scfm.




A pressure control valve regulates gas inlet pressure, and a bypass valve regulates mass flow through the turboexpander in order to maintain stable gas outlet pressure and power generation. Since the ASTE integrates with existing pipeline infrastructure, the regulating station’s safety measures will also protect the ASTE. Additionally, dual fast-acting shutoff valves isolate the ASTE and protect the gas pipeline during controlled and fast stop scenarios.




The ASTE is mounted on a single, compact 18 feet x 7 feet x 7 feet skid. At this size, the ASTE can be shipped in a standard intermodal shipping container and takes up a limited amount of on-site real estate.


The ASTE costs anywhere from 1/4 to 1/2 the price of other turboexpanders on the market. By minimizing these engineering, installation, and manufacturing costs, Anax shortens the machine’s payback period and generates an industry-leading ROI.




The ASTE has an estimated lifetime of 25 – 30 years, with minimal maintenance required. It is designed for installation in seismic zones 1-4 and can stand outdoors with minimal support.





Anax avoids prohibitive engineering costs by designing machines with plug-and-play capability.

Safety and Performance

The ASTE is installed in parallel with the existing regulating valves, providing redundancy and reliability for the pipeline, as well as easy maintenance.

A pressure control valve regulates gas inlet pressure, and a bypass valve regulates mass flow through the turboexpander to maintain stable gas outlet pressure and power generation.

Dual fast-acting shutoff valves isolate the ASTE and redirect gas through the existing regulating valves during controlled and fast stop scenarios such as shaft over-speed/imbalance, loss of utility grid power, loss of external heat, loss of bearing pressure, loss of instrument air, and many more.

The performance and safety tests conducted at the test facility in accordance with the test plan demonstrated technical feasibility and safe operation of the Anax-Star Turboexpander [ASTE250 HP-L250kW GLG]



Gas Technology Institute Safety & Performance Report


Through innovative engineering and design thinking, the Anax-Star Turboexpander overcomes the barriers that have prevented widespread adoption of turboexpanders at natural gas letdown stations.



The ASTE can be adapted to a variety of gas pressure and flow parameters. Additionally, each one can operate as a standalone unit or designed to work in parallel with other ASTE units, producing from 250 KW to several megawatts at a time.



The combination of a permanent magnetic generator and ultra-high frequency inverter enables the ASTE to operate across a wide range of inlet pressures without losing stability. Managing fluctuating inlet pressures has prevented turbines from achieving widespread acceptance in gas letdown applications. To this point, similar machines required stable inlet and outlet conditions in order to deliver at the correct frequency. 



 Since the ASTE generates energy from the flow of natural gas and waste heat recovery, the unit generates electricity with zero carbon emissions. These improvements to natural gas efficiency enable users to generate the same amount of energy with less natural gas. Additionally, this distributed energy resource creates a more resilient grid and reduces the need for dirty peaker plants.

High-Frequency Inverter

High-Frequency Inverter

A high-frequency inverter rectifies generator electricity converting it to standard 480V, 60Hz AC power.



 A full diagnostic suite monitors key parameters such as: temperature, pressure, shaft speed, electrical output, and bearing functionality. Since the ASTE integrates with the existing pipeline infrastructure, all existing redirect and bypass valves protect the machine. Finally, the unit records electrical output and can provide a metered record of performance by remote connection.



 The ASTE operates best as part of a CHP (Combined Heat and Power) system, where waste heat can be used to pre-heat gas entering the turbine. Unlike most systems, the ASTE utilizes low-grade (below 150°F) waste heat that would otherwise be discharged into the atmosphere, as it has limited applications.