Design of a Micro Heat Engine

Abstract The design for a totally new class of heat engine, a micro heat engine, which takes advantage of thermophysical phenomena unique to small scales, is introduced. The proposed engine is an external combustion engine, in which thermal power is converted to mechanical power through the use of a novel thermodynamic cycle which approaches the ideal vapor Carnot cycle. Mechanical power is converted into electrical power through the use of a piezoelectric generator. The generator, which takes the form of a flexible membrane, can be readily manufactured using MEMS fabrication techniques but still delivers high conversion efficiency. This approach eliminates the requirement to manufacture complex micromachines such as rotary compressors and turbines, resulting in a very simple but highly efficient device.

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A Micro Heat Engine for MEMS Power (Keynote Paper)

Fluids Engineering ◽

10.1115/imece2002-39385 ◽

2002 ◽

Cited By ~ 1

Author(s):

C. D. Richards ◽

D. F. Bahr ◽

R. F. Richards

Keyword(s):

Combustion Engine ◽

Thermal Power ◽

Electrical Power ◽

Heat Engine ◽

Thermodynamic Cycle ◽

Mechanical Power ◽

Batch Fabrication ◽

Macro Scale ◽

Micro Heat Engine ◽

External Combustion

Progress in the development of a micro heat engine is presented. The prototype micro heat engine is an external combustion engine, in which thermal power is converted to mechanical power through the use of a novel thermodynamic cycle. Mechanical power is converted into electrical power through the use of a thin-film piezoelectric membrane generator. The design, well suited to photolithography-based batch fabrication methods, is unlike any conventionally manufactured macro-scale engine. In this paper, the design, fabrication and preliminary testing of a working prototype are discussed. The operation of the engine and its key component, the piezoelectric membrane generator is presented. For the first time, the production of electrical power by a dynamic micro heat engine is demonstrated.

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Low Frequency Operation of the P3 Micro Heat Engine

Microelectromechanical Systems ◽

10.1115/imece2002-39307 ◽

2002 ◽

Cited By ~ 1

Author(s):

Scott A. Whalen ◽

Michael R. Thompson ◽

Cecilia D. Richards ◽

David F. Bahr ◽

Robert F. Richards

Keyword(s):

Combustion Engine ◽

Thermal Power ◽

Electrical Power ◽

Heat Engine ◽

Low Frequency ◽

Thermodynamic Cycle ◽

Mechanical Power ◽

Peak Voltage ◽

Macro Scale ◽

Micro Heat Engine

The development and low frequency testing of a micro heat engine is presented. Production of electrical power by a dynamic micro heat engine is demonstrated. The prototype micro heat engine is an external combustion engine in which thermal power is converted to mechanical power through a novel thermodynamic cycle. Mechanical power is converted into electrical power through the use of a thin-film piezoelectric membrane generator. This design is well suited to photolithography-based batch fabrication methods and is unlike any conventionally manufactured macro-scale engine. A peak-to-peak voltage of .84 volts, and power output of 1.5 microwatts have been realized at operating speeds of 10 Hz. Measurements are also presented for the engine operating at resonant conditions. Cycle speeds up to 240 Hz have been obtained, with peak-to-peak voltages of 70 millivolts.

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The P3 Micro Power Generation System

10.1115/imece2001/htd-24283 ◽

2001 ◽

Author(s):

C. Richards ◽

D. Bahr ◽

C.-G. Xu ◽

R. Richards

Keyword(s):

Power Generation ◽

Combustion Engine ◽

Thermal Power ◽

Electrical Power ◽

Heat Engine ◽

Mechanical Power ◽

Carnot Cycle ◽

Generation System ◽

Power Generation System ◽

Micro Heat Engine

Abstract Work toward the development of a new MEMS power generation system, the P3 micro heat engine, is presented. The P3 micro heat engine is an external combustion engine, in which thermal power is converted to mechanical power through the use of a novel thermodynamic cycle that approaches the ideal vapor Carnot cycle. Mechanical power is converted into electrical power through the use of a thin-film piezoelectric membrane generator. A numerical model of the engine, SIMP3, is introduced. The model is used, first to illustrate the micro heat engine’s operation, and then to explore the optimization of the engine. The major parameters controlling the performance of the P3 micro engine are discussed.

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Characterization of a Piezoelectric Membrane for MEMS Power

10.1115/imece2001/mems-23803 ◽

2001 ◽

Author(s):

K. Bruce ◽

R. Richards ◽

D. Bahr ◽

C. Richards

Keyword(s):

Thin Film ◽

Power System ◽

Combustion Engine ◽

Thermal Power ◽

Operating Conditions ◽

Mechanical Power ◽

Central Component ◽

Carnot Cycle ◽

Modular Architecture ◽

Micro Power

Abstract Work toward the development of a thin-film piezoelectric membrane generator is presented. The membrane generator is the central component of a new MEMS power generation system, the P3 micro power system. The P3 micro power system is based on a two-dimensional, modular architecture, in which the individual generic modules or unit cells each have all the functions of an engine integrated. Each unit cell is an external combustion engine, in which thermal power is converted to mechanical power through the use of a novel thermodynamic cycle that approaches the ideal vapor Carnot cycle. Mechanical power is converted into electrical power through the use of a thin-film piezoelectric membrane generator. This paper introduces the concept of the thin-film piezoelectric membrane generator, and describes its design and fabrication. Results of a study to characterize the performance of the piezoelectric membrane generator under expected operating conditions are presented. Current prototypes of the membrane generator are shown to be capable of producing a peak power of 0.1 milliWatts at a voltage of 0.5 Volts.

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Development of Scaling Model for a MEMS-Based Micro Heat Engine

Volume 10: Micro and Nano Systems ◽

10.1115/imece2010-37946 ◽

2010 ◽

Author(s):

H. Bardaweel ◽

B. S. Preetham ◽

R. Richards ◽

C. Richards ◽

M. Anderson

Keyword(s):

Combustion Engine ◽

Heat Engine ◽

Working Fluid ◽

Thin Membranes ◽

Micro Heat Engine ◽

Heat Of Evaporation ◽

Major Factors ◽

Engine Components ◽

External Combustion ◽

Thermal Physical Properties

In this work we investigate issues related to scaling of a MEMS-based resonant heat engine. The engine is an external combustion engine made of a cavity encapsulated between two thin membranes. The cavity is filled with saturated liquid-vapor mixture working fluid. We use both model and experiment to investigate scaling of the MEMS-based resonant heat engine. The results suggest that the performance of the engine is determined by three major factors: geometry of the engine, speed of operation, and thermal physical properties of engine components. Larger engine volumes, working fluids with higher latent heat of evaporation, slower engine speeds, and compliant expander structures are shown to be desirable.

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A Micro Heat Engine Executing an Internal Carnot Cycle

ASME 2008 2nd International Conference on Energy Sustainability, Volume 2 ◽

10.1115/es2008-54266 ◽

2008 ◽

Cited By ~ 1

Author(s):

Eli Lurie ◽

Abraham Kribus

Keyword(s):

Strong Dependence ◽

Heat Engine ◽

Thermodynamic Cycle ◽

Maximum Power ◽

Working Fluid ◽

Carnot Cycle ◽

Heating And Cooling ◽

Engine Design ◽

Power Point ◽

Micro Heat Engine

A micro heat engine, based on a cavity filled with a stationary working fluid under liquid-vapor saturation conditions and encapsulated by two membranes, is described and analyzed. This engine design is easy to produce using MEMS technologies and is operated with external heating and cooling. The motion of the membranes is controlled such that the internal pressure and temperature are constant during the heat addition and removal processes, and thus the fluid executes a true internal Carnot cycle. A model of this Saturation Phase-change Internal Carnot Engine (SPICE) was developed including thermodynamic, mechanical and heat transfer aspects. The efficiency and maximum power of the engine are derived. The maximum power point is fixed in a three-parameter space, and operation at this point leads to maximum power density that scales with the inverse square of the engine dimension. Inclusion of the finite heat capacity of the engine wall leads to a strong dependence of performance on engine frequency, and the existence of an optimal frequency. Effects of transient reverse heat flow, and ‘parasitic heat’ that does not participate in the thermodynamic cycle are observed.

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PZT and Electrode Enhancements of Mems Based Micro Heat Engine for Power Generation

MRS Proceedings ◽

10.1557/proc-730-v5.19 ◽

2002 ◽

Vol 730 ◽

Author(s):

A.L. Olson ◽

L.M. Eakins ◽

B.W. Olson ◽

D.F. Bahr ◽

C.D. Richards ◽

...

Keyword(s):

Bottom Electrode ◽

Mechanical Energy ◽

Electrical Power ◽

Heat Engine ◽

Mems Devices ◽

Stress Concentrations ◽

Process Yield ◽

Micro Heat Engine ◽

Reducing Stress ◽

And Diffusion

AbstractThe P3 Micro Heat Engine relies on a thin film PZT based transducer to convert mechanical energy into usable electrical power. In an effort to increase process yield for these were used on sputtered Ti/Pt bottom electrodes to compare roughness, grain size, and diffusion for annealing temperatures between 550 and 700 °C. For an optimized bottom electrode, process yield for various sized top electrodes were then studied for PZT thickness between 0.54 and 1.62 for reducing stress concentrations. Two PZT etching geometries on 2.3 μm thick Si/SiO2 membranes, with 1.5-3.5 mm side-lengths, were examined and one was used to increase the strain at failure by at least 40%. Integrating improvements in process yield and strain at failure, single PZT based MEMS devices capable of generating power of up to 1 mW and in excess of 2 volts have been demonstrated operating at frequencies between 300 and 1,100 Hz.

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The Mechanical Behavior of a Micromachined PZT Membrane

Microelectromechanical Systems ◽

10.1115/imece2003-41570 ◽

2003 ◽

Cited By ~ 1

Author(s):

I. Demir ◽

R. F. Richards ◽

D. F. Bahr ◽

C. D. Richards

Keyword(s):

Thin Film ◽

Mechanical Behavior ◽

Material Properties ◽

Energy Minimization ◽

Variational Approach ◽

Piezoelectric Ceramic ◽

Electrical Power ◽

Heat Engine ◽

Silicon Membrane ◽

Micro Heat Engine

The mechanical behavior of a micromachined PZT membrane for power applications is investigated. The membrane is a bulk-micromachined silicon membrane that supports a thin film of piezoelectric ceramic (PZT) sandwiched between platinum and gold electrodes. The membrane undergoes large periodic deflections to convert mechanical power to electrical power in a micro heat engine. An analysis using a variational approach is developed to find an approximate closed from solution based on energy minimization. Experiments were conducted to obtain material properties, residual stresses, and pressure deflection relationships. The modeled results compare well to the experimental results.

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A New Heat Engine and its Applications in Concentrating Solar Power (CSP)

ASME 2012 6th International Conference on Energy Sustainability, Parts A and B ◽

10.1115/es2012-91358 ◽

2012 ◽

Author(s):

Yiding Cao

Keyword(s):

Heat Source ◽

Internal Combustion Engines ◽

Solar Power ◽

Combustion Engine ◽

Heat Engine ◽

Working Fluid ◽

Concentrating Solar Power ◽

Time Duration ◽

Combustion Gas ◽

External Combustion

This paper introduces a new heat engine using a gas, such as air or nitrogen, as the working fluid that extracts thermal energy from a heat source as the energy input. The heat engine is to mimic the performance of an air-standard Otto cycle. This is achieved by drastically increasing the time duration of heat acquisition from the heat source in conjunction with the timing of the heat acquisition and a large heat transfer surface area. Performance simulations show that the new heat engine can potentially attain a thermal efficiency above 50% and a power output above 100 kW under open-cycle operation. Additionally, it could drastically reduce engine costs and operate in open cycles, effectively removing the difficulties of dry cooling requirement. The new heat engine may find extensive applications in renewable energy industries, such as concentrating solar power and geothermal energy power. Furthermore, the heat engine may be employed to recover energy from exhaust streams of internal combustion engines, gas turbine engines, and various industrial processes. It may also work as a thermal-to-mechanical conversion system in a nuclear power plant, and function as an external combustion engine in which the heat source is the combustion gas from an external combustion chamber.

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