Bowman Microturbine

Bowman Power Systems (BPS), is developing the TurbogenTM family of small scale compact power generation systems ranging from 25 kWe to 80 kWe, for distributed power generation and for mobile power applications.

These systems are based on compact gas turbines (Micro Turbine Engines) and high speed generator technologies (Turbo Alternators), together with associated power electronics (Power Conditioners).

Nominal size for the Bowman microturbine is 80 kW, depending on options.

Features

The BPS systems offer the following standard and optional features:

• Recuperated or simple cycle Microturbine Generator
• Pre-engineered compact Package
• Gas fuel capability
• Alternate fuels: Diesel and Kerosene (Optional)
• Low Emissions
• High operational flexibility allowing both 'Heat or Power demand following'
• Low acoustic noise level
• Low temperature hot water output (90 degrees C.)
• Capability to produce high pressure hot water
• Capability for steam production
• Power output with utility network interface for grid connection (Option)
• Power output for stand alone operation (Option)
• Peak shaving and load following (Options)
• Remote control and monitoring (Options)
• Data logging (Options)

Microturbine Engines

These very small high speed gas turbine engines are simple radial designs, closer in concept to low cost turbochargers than the more complex axial designs of large industrial engines, which are often derived from aero engines. Conservative operating temperatures eliminate the need to use high cost sophisticated materials, which together with their simplicity is conducive to low cost when produced in volume.

In comparison with reciprocating engines, they attract lower maintenance costs, produce lower vibration, lower emissions and are more compact, making them the ideal engine choice for cogeneration and CHP systems.

Turbo Alternators

A conventional small gas turbine generator set consists of a high speed turbine (e.g. 50k rpm) coupled to a low speed electrical machine (e.g. 3k rpm) through a reduction gearbox. However, the power output of an electrical machine is proportional to speed. Consequently, if the electrical machine (alternator) is run at turbine speed it is so small that it can be integrated into the engine on the same shaft as the turbo machinery forming a compact high speed generator or Turbo Alternator. The gearbox is no longer required and the alternator also acts as a starter motor to further reduce the size of the generator set.

The BPS definition of a MTG is where a high speed generator is used and runs at turbine speed on a single or multi-shaft system. The primary power range for this Turbo Alternator technology is 25 kW to 500 kW. However, for certain applications it is expected to be used down to a few kW and possibly up to a few MW.

BPS first systems cover the range 25kW to 115kW, with systems up to 2MW planned for later development.

Recuperators

Durable heat exchangers of high affectivity and low cost are needed to increase the efficiency of gas turbines to the levels needed to compete with reciprocating engine based power generation systems. Their function is to preheat the air used in the combustion process and thereby reduce the amount of fuel used to reach operating temperature.

The BPS recuperator is a primary surface type, manufactured from stainless steel for long life. With an affectivity of about 90%, the fuel consumption of the microturbine engine is approximately halved, doubling the MTG efficiency from 15% to about 30%.

Power Conditioners

The electrical output frequency of a Turbo Alternator is typically 1000 to 3000 Hz and must be converted to 50 or 60 Hz. A microprocessor controlled Power Conditioner carries out the frequency conversion, and other power conditioning and utility connection functions, to provide electrical power of appropriate quality and features. The Power Conditioner controls output frequency independent of turbine speed and facilitates the variation of speed with load to save fuel.

The BPS Power Conditioner is designed in house and provides the functionality to allow the MTG to operate in parallel with the utility supply (Grid connected) in Export or Load Following mode, or as a stand alone system (Island Mode). Integrated engine control and management capability together with remote control and monitoring is a further feature of this module.

Gas Boost Compressors

Natural gas is the fuel of choice for stationary power plants. Pipeline gas is usually supplied to small users at low pressure, typically less than 1 psi. An MTG requires gas at 60 to 80 psi, therefore an efficient low cost durable Gas Boost Compressor is needed.

BPS are developing suitable technology in association with experienced air and refrigeration compressor manufacturing companies and now have units from two suppliers available for commercial use subject to completion of certification.

Specifications

Emissions

NOx = 25 ppm @ 15% O2

Heat Recovery

Bowman is currently the only microturbine manufacturer to promote using their unit to produce low pressure steam. As the Table indicates above, the TG80 is available both with and without a recuperator. The non-recuperated unit has substantially higher exhaust gas temperatures that can be used to direct fire a steam waste heat boiler (HRSG) or a small absorption chiller.

PDF Literature

The following information is available on THIS site in PDF format:

Bowman Brochure
Bowman spec sheet
Turbo Alternator spec sheet
Power Conditioner spec sheet
Gas Boost Compressor spec sheet

Bowman Power

For more information about Bowman,

Bowman Power Systems
20501 Ventura Blvd
Suite 295
Woodland Hills, CA 91364
818-999-6709

Go to the Bowman web site www.bowmanpower.com

Source: Bowman product brochures and web site 7/2002