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Design, Development and Manufacture of High-Speed Foil Bearings

Mohawk Innovative Technology, Inc., Albany, NY

Mohawk Innovative Technology, Inc. Turbine Image

Background

A tremendous amount of energy is lost in the form of waste heat. Low grade heat from sources such as combined cycle power plants, industrial processes, geothermal wells, engine exhaust gases, small scale cogeneration, or domestic boilers etc., and even commercial buildings give off substantial amount of waste heat. Some estimates put this number as high as 15 quadrillion British Thermal Units (BTU) of waste heat generated in the US each year. The flow of energy from heat source to heat sink has the capacity to do work. Currently, almost none of this energy is being recovered, and the market for energy recovery systems is substantial.

Waste heat energy can be converted to electricity with a recovery system that uses a small turbine generator at its core. Although the technology is well matured, there has been difficulty developing a turbo generator which has the required high efficiency, reliability, and low cost to be accepted in the market place. A high speed turbine generator helps to achieve the desired high efficiency and power output, However, the generator bearings, which experience high stress and hard working conditions, have been problematic. MiTi, with funding from NYSERDA, had implemented a revolutionary type of oil free bearing for the turbo generator. The new bearing uses a very small cushion of ambient gas for lubrication, which results in the turbine shaft "floating" on a thin gas film as it spins at operational speeds. While the shaft and bearing are in contact during startup and shutdown, the shaft is quickly levitated once the rotor starts spinning. Because there is no contact between the shaft and bearings during operation and only one moving part is used very high reliability is achieved.

Systems have to be sized for the particular application, but can range from tens of Kilowatts to upwards of Megawatt systems. It is expected that the systems will have a payback period of about two or three years. Although higher temperatures are preferred, current systems are capable of operating with working fluid temperatures as low as 160 degrees.

Objective/Scope

This project is entering its final stages of testing as a prototype in an industrial environment. The Indeck-Corinth Energy Center operates a 132MW combined cycle power-generation system and a distilled water product plant, which will be used for this system demonstration. This project entails a full system detailed design, followed by fabrication, installation, and operation at the site. Operational data will be recorded and analyzed for at least the first six months.

Description

The industry setting will test the technology in real case situations, involving longer operating times and changing working conditions. The advanced turbo generator features a Variable Frequency Inverter, brazed plate heat exchanger and air cooled condenser technologies and an environmentally friendly working fluid (R134a) to make an efficient and reliable power generating system with minimal operating costs. Other benefits include elimination of environmental hazards and costs associated with oil changes and disposal, lower noise, and small footprint.

Benefits and Metrics

Successful demonstration of oil-free bearing turbo-generator technology will allow MiTi to market the technology to other end-users, which will lead to the creation of high-technology manufacturing jobs in New York State. Industries that use MiTi’s system will experience lower operating costs by producing part of their own electricity with waste heat streams. This will also lower demand on utility grids and power stations. The proposed system design will be modular to accommodate a wide variety of low-grade heat sources may be used. The system can represent a stand-alone generation site with an external heat source. Renewable heat sources, such as solar thermal, could also be integrated to the turbo generator.

Links

The first link below is a demonstration of the proof of concept turbo generator in operation using air in an open loop configuration.

Schedule and Status

A contract was recently executed and the project is under way.

Last Updated: 08/13/2014