Introduction Acoustic to electric power conversion Kees de Blok, - - PowerPoint PPT Presentation

▶
introduction
SMART_READER_LITE
LIVE PREVIEW

Introduction Acoustic to electric power conversion Kees de Blok, - - PowerPoint PPT Presentation

Jun 11, 2023 21 likes •182 views

Introduction Acoustic to electric power conversion Kees de Blok, Aster Thermoacoustics Pawel Owczarek, Future energy management-University of Wraclow Maurice Francois, Hekyom Brief introduction Thermoacoustic engine Multistage traveling wave

slide-1
SLIDE 1

23 juni 2014

1

Introduction

Acoustic to electric power conversion

Kees de Blok, Aster Thermoacoustics Pawel Owczarek, Future energy management-University of Wraclow Maurice Francois, Hekyom

Brief introduction Thermoacoustic engine Multistage traveling wave themoacoustics High power applications Acoustic to electric conversion (movie) Full scale design Conclusions

slide-2
SLIDE 2

Introduction

What is thermoacoustics?

  • A key enabling energy conversion technology based on "classic"

thermodynamic cycles in which compression, displacement and expansion of the gas is controlled by an acoustic wave rather then by pistons and displacers.

  • Characteristics
  • No mechanical moving parts in the thermodynamic process
  • Maintenance free
  • Simple construction
  • Large freedom of implementation
  • Low noise
  • High efficiency (>40% of the Carnot factor)
  • Large temperature range
  • Scalable from Watt’

s to MegaWatt’ s

  • Inert gas like helium, argon or even air as working medium

23 juni 2014 2

slide-3
SLIDE 3

Introduction

What can we do with thermoacoustics? Converting heat into acoustic energy (= mechanical energy) ⇒ Heat engine

  • Heat supply at high temperature from arbitrary heat source
  • Onset temperature difference ≈ 30ºC
  • Operating temperature differerence >100ºC

Converting the acoustic output power into electricity

  • Linear alternator (loudspeaker)
  • Bi-directional turbine

Converting acoustic energy into a temperature lift

(By reversal of the thermodynamic cycle)

⇒ Heat pump or refrigerator

  • Temperature lift: > 80ºC
  • Temperature range: -200ºC up to 250ºC

23 juni 2014

3

TAEC

Heat supply at high temperature Heat sink at a low temperature Acoustic

  • utput power

TAEC

Heat taken at low temperature Heat sink at a high temperature Acoustic power

slide-4
SLIDE 4

Introduction

Typical operating characteristics

  • Low onset and operation temperature
  • No wear and mechanical friction
  • Large temperature range
  • No phase change working gas

23 juni 2014

4

Thermoacoustic heat pump Thermoacoustic Heat Engine Thermoacoustic cooler

slide-5
SLIDE 5

23 juni 2014

5

Thermoacoustic engine

Basic geometry of a thermoacoustic engine

  • Above onset temperature acoustic

power gain exceeds losses and

  • scillation start
  • Oscilllation frequency is set by

(acoustic) length of the feedback tube

  • At increasing input temperature (above
  • nset) part of the acoustic loop power

can be extracted as net output power Acoustic output power can be converted to

  • electricity …
  • r drive a termoacoustic heat pump
slide-6
SLIDE 6

23 juni 2014

6

Multi-stage traveling wave thermoacoustics

Utilizing low and medium temperature heat sources

  • Waste heat
  • Solar (vacuum tube collectors)
  • Geothermal
  • …….
  • .

Multi stage traveling wave thermoacoustic engine

  • Increase of acoustic power gain proportional with

number of stages

  • Less acoustic loop power relative to the net acoustic
  • utput power (more compact design)
  • Oscillation frequency set by the acoustic length
  • Onset temperature difference < 30°C
  • Operating temperature difference > 100 °C

4-stage thermoacoustic traveling wave engine (THATEA project)

slide-7
SLIDE 7

High power applications

23 juni 2014

7

100 kWT Thermo Acoustic Power generator 3m

Thermoacoustic power (TAP)

Conversion of industrial waste heat into electricity

  • SBIR project phase2

Design and built of a TAP converting 100 kW waste heat at 160ºC into 10 kW electricity Location: Smurfit Kappa Solid Board, Nieuweschans(Gr)

Other (industrial) applications

  • Heat transformer

Upgrade waste heat above the pinch

  • Gas liquefaction

Storage and transport of LNG

slide-8
SLIDE 8

High power applications

23 juni 2014

8 Conclusions of the TAP project in 2011

  • Thermoacoustic energy conversion itself can be scaled up

in power succesfully

  • Upscaling toward high power applications is blocked by the

linear alternators Practical issues

Piston stroke limited by stroke of the springs Size and weigth of moving mass more than proportional with power (Larger TA system ⇒ lower frequency ⇒ less induction) Sensitive for overload Vibration

Economic issues

Cost > 3000 € / kW No mass production Per kW electrictricity relativelly large amont of magnetic materiaal Availability and cost of raw materials for strong magnets (neodynium) The TAP Linear alternator

slide-9
SLIDE 9

Acoustic to electric conversion

23 juni 2014

9 1) Using the acoustic wave pressure component Convert periodic pressure variation into periodic bi-directional linear motion (piston, membrane)

Linear alternators MHD Piezo electric effect

2) Using the acoustic wave velocity component Convert periodic bi-directional velocity into uni- directional rotation

Bi-directional turbine

Mean pressure Acoustic wave motion Pressure amplitude Gas displacement amplitude

slide-10
SLIDE 10

Acoustic to electric conversion

23 juni 2014

10 Bi-directional turbines Rotation is independent of flow direction Know embodiments

  • Lift based turbines

Wells turbine Darrieus rotor (wind turbine)

  • Impulse based turbines

Savonious rotor (ventilation) Axial impulse turbine Radial impulse turbine

Existing technology used for oscillating water column (OWC) wave power plants (30-500kWe)

Bron: Limpet 500

Guide vanes Rotor Guide vanes

slide-11
SLIDE 11

Acoustic to electric conversion

23 juni 2014

11 Acoustic experiments on scale models

  • Radial impuls turbine (100mm∅)
  • Axial impuls turbine (72mm∅)

Both manufactured in SLA-SMS 3-D printing. brushless DC elektromotor used as generator

Observations:

  • Radial turbine
  • Higher torque at lower rotational speed
  • Axiale turbine
  • Lower torque at higher rotational speed
  • Better efficiency for AC flow
  • Output power and efficiency observed to be

hardly dependent of acoustic frequency

Axiale impuls turbine Relation rotor efficency and frequency

slide-12
SLIDE 12

Acoustic to electric conversion

23 juni 2014

12 Scaling experiment at the 100 kW TAP SKSB

Linear alternator replaced by radial bi-directional inpulse turbine

  • Measured rotor efficiency of 75% at 0.8MPa
  • Efficiency proportional with fluid density

Radiale impuls turbine voor de TAP (Drotor =300 mm) Radiale impuls turbine in position in engine stage #2

slide-13
SLIDE 13

Acoustic to electric conversion

23 juni 2014

13 Test axial turbines in the 100kW TAP

Manufactured by AGAN italy

Axial turbine :

Rotor diameter: 200mm Rotational speed : 2700rpm Power: 2 kW

Generator : Outer runner permanent magnet motor Aim of this experiment

  • Validate turbine model
  • Acoustic impedance
  • Avoid radial induced streaming
  • Confirm feasible turbine effciency
  • Starting point for manufacturing and turbine optimization

Efficiency in air at 0.8MPa of this axial bi-directional turbine is measured to be 80%

Turbine in preparaton Turbine position inside the TAP

slide-14
SLIDE 14

Full scale design 1MWT

23 juni 2014

14

  • Basic thermoacoustic engine stage

Low temperature heat exchanger High temperature heat exchanger Regenerator

Acoustic power in Acoustic power out

Bi-directional turbine + generator

Low temperature cooling circuit 15-40°C (Waste) heat in (140-250°C) Electricity out

slide-15
SLIDE 15

Full scale design 1MWT

23 juni 2014

15

Flue gas heat exchanger Roof section or mounting platform

2 m

Looped heat-pipe circuits Heat sink terminals

slide-16
SLIDE 16

Conclusions

23 juni 2014

16

  • The TAP concept is theroretical and experimentally validated and recognized as a compatitive

technology for converting waste heat into electricity.

  • Upscaling in power toward industrial levels however was blocked by the increasing cost, mass and

complexity of linear alternators

  • As a practical and economic viable alternative for linear alternators at increasing power levels the

concept of a bi-directional turbine, converting acoustic power into rotation and from there into electricity, is introduced and tested succesfully

  • Rotor efficiency defined as shaft output power over acoustic input power is a function of fluid density,

and is measured to raise from about 30% at atmospheric pressure up to 80% for air at 0.8MPa.

  • As a major achievement, the initial limitation in upscaling the thermal and electric power levels is

abrogated, paving the way for full scale application of thermoacoustic waste heat recovery in industry up to MW scale