1

1

Small-Scale Biomass-Fired CHP System

Dr. Hao Liu*, Prof. Saffa Rif1fat

and Dr. Guoquan Qiu

ERA-NET Bioenergy Conference @Berlin, Germany

2

PROJECT CONSORTIUM,

FUNDING AND PLANS

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Project Consortium

• Academic Partners

– University of Nottingham, UK
– University of Duisburg – Essen, Germany

• Industrial partners

– Renewable Energy Suppliers Ltd (RES), UK
– Nottinghamshire County Council, UK
– Barnsley Metropolitan Borough Council, UK
– Gesellschaft fur Motoren und Kraftanlage

(GMK), Germany

4

Project Funding (1)

• Funding Organisations

– Engineering and Physics Science

Research Council (EPSRC), UK

– FNR - Fachagentur Nachwachsende

Rohstoffe e.V. Agency of Renewable
Resources , Germany

2

5

Project Funding (2)

• Financial Summary

– Overall cost: €355k
– Funding for University of Nottingham:€194k
– Funding for University of Duisburg – Essen:

€112k

• Project Duration

– 17 months
– Starting/Completion Dates:

• Nottingham 1 Jan 2007 – 31 Oct 2008
• Essen 1 Jan 2007 – 31 May 2008

6

Research

Motivations

Energy

Environment

Economics

Biomass –
A Primary

Sustainable Energy

Biomass Combustion-

A Carbon Neutral

Process

Small-Scale

Biomass-Fired CHP–

Used in domestic and
commercial buildings

7

Research Objectives

To Prove the Applicability of

Biomass-Powered CHP with ORC

in a Small-scale System of 1 - 10KWe

To Design, Construct and Evaluate the

Small-scale Biomass-Fired CHP System

To Develop a Computer Model for the

Small-Scale Biomass-Fired CHP system

8

Working Packages

WPs

WP1

CHP Setup

WP3

CHP

Modelling

WP4

Project

Management

WP2

CHP

Evaluation

3

9

Working Package 1

CHP Setup

Procurement and

Modification of the

Biomass Boiler and

Heat Exchangers

Procurement and

Modification of the
ORC Micro-turbine

Installation and

Assembly of the CHP

System Components

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Working Package 2

CHP

Evaluation

Preliminary
ORC Micro-

Turbine Test

ORC Working

Fluids Test

( HFEs, n-pentane,

Honeywell 245a-WF)

Electricity

Efficiency

&

CHP Efficiency

Pollutants

Emission

(CO, NOx,

Particulates,

CxHy, etc.)

11

Working Package 3

CHP

Modelling

Biomass

Combustion
in the Boiler

ORC Cycle

Thermal Oil

Cycle

ORC Turbine

Condenser

Evaporator

Chemical

Reaction

Pollutants

Emission

Heat Transfer

from the

Combusted

Gases

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Working Package 4

Management

Team

University of Duisburg –

Essen

Prof. Dr.-Ing. Ingo Romey

University of Nottingham

Dr. Hao LIU

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13

1

2

3

4

5

6

7

8

9

1 0 1 1

1 2

1

2

3

1

2

3

4

5

6

7

8

9

1 0 1 1

1 2

1

2

3

M o n th

W o rk P la n ( fo r U o N )

M o n th

P re lim in a ry W o rk &

L ite ra tu re R e v ie w

E q u ip m e n t

P ro c u re m e n t

C H P I n s ta lla tio n

C H P T e s tin g

C H P E v a lu a tio n

Y e a r

2 0 0 8

Y e a r

2 0 0 7

Work Plan for University of Nottingham

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EXPERIMENTAL TESTS

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System Characterization

Micro-Turbine

with ORC

Direct Biomass

Combustion

Heat

Exchanging

Carbon Neutral

Low-Cost

Investment

High Efficiency

2KWe Biomass CHP

16

25kW biomass boiler in
University of Nottingham

Biomass Boiler and Fuel

5

17

Micro-Turbine

Alternator

Micro-Turbine & Alternator

18

Alternators

Car Alternator 1

Alternators

Car

Alternator 2

High Output

Alternator

19

Performance of Typical Car Alternators

20

Performance of High Output Alternator

6

21

Power Generation Test Rig

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™

Expansion in the superheating state

™

High enthalpy drop ( i.e., high thermal
efficiency)

™

Acceptable thermal stability

™

Non-toxic

™

No ozone depletion

™

Low global warming potential

Criteria for Selecting ORC Fluids

23

™

HFE7100 – tested & modelled

™

HFE7000 – tested & modelled

™

N-pentane - modelled

Selected ORC Fluids

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THERMODYNAMIC MODELING OF

THE ORC-BASED CHP SYSTEM

7

25

‰

Boiler thermal efficiency

η

boiler

= 85%

‰

Isentropic turbine efficiency

η

IST

= 85%

‰

Isentropic working fluid pump efficiency

η

ISP

=65%

‰

Turbine to alternator electrical conversion
efficiency

η

alter

=

90%

Main Modeling Assumptions

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A Typical ORC T-S Diagram

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‰

Organic cycle efficiency:

Calculation Formula

act

act

act

input

output

h

h

h

h

h

h

q

w

act

2

3

1

2

4

3

)

(

)

(

−

−

−

−

=

=

η

‰

Carnot cycle efficiency:

1

2

1

T

T

carnot

−

=

η

‰

Electrical efficiency of the CHP:

η

elec

=

η

act

η

boiler

η

alter

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RESULTS & CONCLUSIONS

8

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Thermodynamic Modelling Results (1)

0.71 0.72 0.73 0.74 0.75 0.76 0.77 0.78 0.79 0.80 0.81 0.82 0.83 0.84

10

12

14

16

18

20

22

24

26

28

30

Actua

l O

R

C an

d

C

ar

no

t cycle

efficie

ncy, %

T

2

/T

1

η

act

η

carnot

(T

1

=100

0

C)

η

act

η

carnot

(T

1

=120

0

C)

η

act

η

carnot

(T

1

=140

0

C)

HFE 7000

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Thermodynamic Modelling Results (2)

0.71 0.72 0.73 0.74 0.75 0.76 0.77 0.78 0.79 0.80 0.81 0.82 0.83 0.84

10

12

14

16

18

20

22

24

26

28

30

Actual

ORC

a

nd

Ca

rno

t cycle

e

ffici

ency, %

T

2

/T

1

η

act

η

carnot

(T

1

=100

0

C)

η

act

η

carnot

(T

1

=120

0

C)

η

act

η

carnot

(T

1

=140

0

C)

HFE 7100

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Thermodynamic Modelling Results (3)

0.71 0.72 0.73 0.74 0.75 0.76 0.77 0.78 0.79 0.80 0.81 0.82 0.83 0.84

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8

9

10

11

12

13

Ele

ctrica

l efficie

n

cy

o

f th

e CH

P

system

, %

T

2

/T

1

HFE7000

HFE7100

n-pentane

T

1

=100

0

C (solid)

T

1

=120

0

C (half-solid)

T

1

=140

0

C (hollow)

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ORC Turbine - Air Test Results (1)

Air Flow Rate (l/min, STP)

Ro

ta

tio

n

Sp

e

e

d

(r

p

m

)

100

200

300

400

500

600

700

800

350

400

450

500

550

600

650

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ORC Turbine - Air Test Results (2)

Air Flow Rate (l/min, STP)

Ai

r

P

re

ss

ur

e

(ba

r)

100

200

300

400

500

600

700

800

2.5

3

3.5

4

4.5

5

5.5

6

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RPM, Pressure & Flow Rate vs HFE7100 Pumping Rate

5

10

15

20

25

30

35

40

45

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

200

400

600

800

1000

1200

1400

P

res

sure (

bar),

HFE

fl

o

w

rat

e (l/

m

in)

HFE pump setting (%)

Turbine inelt pressure (bar)
HFE7100 flow rate (l/min)

18 Aug 2008

RP

M

RPM

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Turbine Test Data – Energy Balance

0

2

4

6

8

10

12

10

15

20

25

30

35

40

45

HFE7100 pump setting,%

Bo

iler hea

t in

put and hea

t ou

tput,

kW

Heat Input
Heat output from Cond.

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Power Generation Test Data – V, I (HFE7100)

HFE7100

-2

0

2

4

6

8

10

12

14

16

12:43:12

12:57:36

13:12:00

13:26:24

13:40:48

13:55:12

14:09:36

Time

I,

V

I, Amps
V, volts

10

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Power Generation Test Data – V, I (HFE7000)

I,V vs Time (HFE7000)

0

2

4

6

8

10

12

14

16

13

:0

4:

00

13

:0

5:

50

13

:0

7:

40

13

:0

9:

30

13

:1

1:

20

13

:1

3:

10

13

:1

5:

00

13

:1

6:

50

13

:1

8:

40

13

:2

0:

30

13

:2

2:

20

13

:2

4:

10

13

:2

6:

00

13

:2

7:

50

13

:2

9:

40

I,

A;

V,

Vo

lt

I, Amps
V, Volt

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Power Generation Test Data – Energy Balance

0

1

2

3

4

5

6

7

8

9

10

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In

put/

O

ut

p

ut

Energy,

kW

HFE7100 pump setting, %

Measured heat Input from boiler
Measured heat ouput from cond.
Calculated maximum turbine output

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39

Power Generation Test Data – Energy Balance

0

10

20

30

40

50

60

70

80

90

37

Ef

fic

ienc

y,

%

HFE7100 pump setting, %

Measured/calculated CHP eff.
Calculated maximum electrical eff. using measued data

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Conclusions (1)

• A biomass-fired CHP with ORC has been

developed and tested. In total, more than 5000

hours of operation have been accumulated.

• Successful power generation with the CHP

system indicates that ORC-based power

generation can be applied to 1-10 kW

e

biomass-

fired CHP

– Total CHP efficiency of the CHP system is over 80%.

– However, the electrical efficiency of the CHP system

achieved with experiments is much smaller than

those predicted by thermodynamic modelling and by

calculations using experimental data

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Conclusions (2)

• The main components of the developed ORC-

based CHP system need to be optimised:

– Turbine: The isentropic efficiency of the existing

turbine is in the order of 10-20%

– Alternator: The cut-in speed of all of the tested

alternators are too high.

– Biomass boiler: The maximum hot water

temperature needs to be 120

0

C - 160

0

C.

– Pumps and heat exchangers: They need to be

specifically designed for their purposes (e.g.
evaporator, condenser)

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An optimised micro-scale biomass-fired

CHP with ORC can provide the required

heat and power to its users from a

renewable source (biomass) with

acceptable electrical and overall

efficiencies.

Conclusions (3)