Smart energy management system with CO2 as working fluid

Japan-Norway Energy Science Week 2015

Smart Energy Cities and Industries

Hiroshi Yamaguchi, Ph.D. Energy Conversion Research Center

Professor

Department of Mechanical Engineering

Fluid Mechanics Laboratory, Doshisha University, Japan

Introduction

History and main application of CO2’s use as a refrigerant

1990s 1850, The concept of CO2 vapor compression refrigeration system was first proposed. Interest in CO2 was renewed due to the phase-out of ozone depleting refrigerants.

…

G. Lorentzen received high credit for the new attention to CO2.

1990 G. Lorentzen patented application for a transcritical CO2 heat pump system.

Later 1990s

Theoretical and experimental researches on practical heat pump and system design.

R & D of refrigerator using as natural refrigerant has been becoming popular in recent years.

An example of industrial use

CF. : http://www.fareastgizmos.com/wp-content/uploads/2007/10/Sanyo_Coca_cola.jpg

Advantage of CO2 as working fluid :

Harmless

Uninflammable

High Cp and high heat transfer coefficent

Zero ODP and Low GWP （vs R134a: 1/1300）

Developing new type CO2-based Heat Pump refrigerator are highly expected.

Ammonia CO2

H2O Air Hydrocarbon etc.

Natural refrigerant Freon-based refrigerant

CFC HCFC

Stopping from 1996 Will be stopped from 2020

（Depletion of Ozone layer+Global warming）

Development of refrigerants used refrigerator

Low adverse effect to Ozone layer

HFC

（Global warming）

Alternative Freon

CF.:http://www.cbc.ca/news2/background/kyoto/gfx/titlephoto.jpg

CF.:http://www.cbc.ca/news2/background/kyoto/gfx/climatechange250.jpg

Classification

Refrigerant ODP GWP Safety

HCFC R22 0.055 1700 A1

HFC

R134a 0 1300 A1

R404A 0 3850 A1

R407C 0 1370 A1

R410A 0 1370 A1

R507A 0 3900 A1

Natural refrigerant

NH3 0 ＜1 B2

C3H8 0 3 A3

C4H10 0 3 A3

CO2 0 1 A1

16 In ANSI/ASHRAE Standard 15-1992, refrigerants are classified according to the hazard involved in their use. Group A1 refrigerant are the least hazardous, Group B3 the most hazardous.

HFC

Natural refrigerant

Heat carrier

CO2

Non-toxicity Non-flammability Inertness

CO2’s Advantage

A：low toxicity, B：high toxicity 1： Non-flammable, 2：mild flammable, 3：extremely flammable ODP : Ozone Depletion Potential GWP : Global Warming Potential

Energy Conversion Research Center

Ice thermal storage tank

Heat pump cycle (Experimental)

Solar Rankine system (Experimental)

Gas engine Generator Heat exchanger

Energy management

Cold water & Air conditioning Thermal-use Power Supply

Hot water & Air conditioning Thermal-use

Absorption refrigerator

CO2 is used

CO2 is used

Energy Conversion Research Center

CF. : https://www1.doshisha.ac.jp/~ene-cent/newpage70.html

Energy management system

CF. : https://www1.doshisha.ac.jp/~ene-cent/framepage6.html

CO2 Heat Pump Add. Recoverd Heat

30%ηn

40%ηCG

Heat Exchanger

High Temperature Exhaust Gas

Water

Power Unit Generator

Cooling Water

Air

Fuel

Recovered Heat

Electricity

Steam Hot water Hot water

Total Efficiency 70～75%

SUPER CRITICAL CO2 RANKINE CYCLE SYSTEM

Natural Energy

Solar Energy arriving surface of the earth 115.0000×1012 kW Solar energy is absorbed plants 0.0965×1012 kW

Amount of Primary Energy Consumption of The World

0.0150×1012 kW

Energy of Wind, Wave, Ocean stream 0.3700×1012 kW

Amount of Primary Energy Consumption in Japan

0.0007×1012 kW

Solar Energy is Large Amount of Energy

Studying about solar energy is very active

CF. : World Energy Statistics (2009)

Natural Energy

Thermophysical properties dramatically changes with temperature

Pseudo-critical region

Cp

10

6 [

Pa

s],

/10 [

kg/m

3]

/

10

3 [

W/mK

], C

p [

J/(k

gK

)]

T [K]280 300 320 340 360 380

0

20

40

60

80

100

120

140

Thermophysical property of CO2 at 9.0MPa

・Low viscosity ・Low density ・High specific heat

Outline of SRCS

Heat output

Electric generator

Pump

Evacuated solar collectors

Heat exchangers Turbine

Solar energy

CO2 flow

SRCS generates electrical and thermal energy by using solar energy.

h [kJ/kg]

P [

MP

a]

304.1 [K]

7.38[MPa]

SupercriticalLiquid

Liquid+Gas Gas

5 1

234

C.P.

500 600 700 800 9001

2

3

4

5

6

7

8

9

10

11

12

Trans-critical Rankine cycle

Mollier diagram

<Critical point> P=7.38MPa T=304.1K

④

≡

Power output

・Evaluation item Specific enthalpy at point 1 ~ point 5 : h [kJ/kg]

Total global solar radiation ：QI [kW]

Total heat gain ：Qin [kW]

Thermal efficiency ： ηc [%]

・Measurement item CO2 temperature :T1~T5 [℃]

CO2 pressure : P1~P5 [MPa]

CO2 mass flow rate : G [kg/min] Amount of solar radiation : I [kW/m2] Heat collecting area : Ae [m

2]

※Thermophysical properties of CO2 are obtained by PROPATH12.1

Experimental condition and evaluation item

dtAIQt

eI

dthhGQt

in 51

100I

in

CQ

Q

Performance

Average data

I [kW/m2] 0.400

G [kg/min] 0.497

Qin [kW] 2.26

ηc [%] 26.4

(a) With ice storage (b) Without ice storage

Average data

I [kW/m2] 0.426

G [kg/min] 0.463

Qin [kW] 1.87

ηc [%] 20.6

Heat gain and solar radiation (19/9/2007) Heat gain and solar radiation (26/9/2007)

15 units 3 parallels

Time

To

tal h

eat

gai

n [

kW

] So

lar radiatio

n [k

W/m

2]

Total heat gain [kW] Solar radiation [kW/m2]

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 190

0.4

0.8

1.2

1.6

2

2.4

2.8

3.2

3.6

4

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Time

So

lar radiatio

n [k

W/m

2]

To

tal h

eat

gai

n [

kW

]

Total heat gain [kW] Solar radiation [kW/m2]

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 190

0.4

0.8

1.2

1.6

2

2.4

2.8

3.2

3.6

4

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

HEAT PUMP SYSTEM USING CABON DIOXIDE

Ptr=0.518

Pcr=7.38

Pres

sure

P [M

Pa]

T=31.1℃

Super Critical

C.P

Gas

0

Solid

Liquid +

Solid

Ｔtr=-56.6℃

Liquid

Gas + Liquid

Solid + Gas

Enthalpy h [J/kg]

Mollier diagram (Pressure – Enthalpy) of carbon dioxide

1,1’ Compressor 2,2’ Heat exchanger for tap water 3,3’ Heat exchanger for cool water 4,4’ Expansion valve 5,5’ Cascade heat exchanger for brine 6 Test section

Cascade CO2 heat pump system

High pressure side Low pressure side

1 2 3

4 6 1’

2’ 3’

5 5’

4’

Brine

Cooling tower

Gas engine

・Ice storage ・Hot water supply ・Dry – ice

Heat pump system To achieve the temperature below -56.6 ℃ of the CO2 solid and gas two-phase flow in the test section

Rated output:8.4kW (Inverter control)

Rated output:6.0kW (Inverter control)

Performance

Condensing Temperature T3

Condensing Temperature T3’

Suction Temperature T1

Suction Temperature T1’

(a) Low Temperature Side (b) High Temperature Side Fig. Temperature of HTS and LTS vs. Time

Ultra-low temperature can be achieved in test section continuously

Performance & Application

COPsystem 0.298 Refrigeration temperature -59.0 ℃

WmWm

hm

hh

coolsystemCOP

COP : Coefficient Of Performance

: mass flow rate of LTS [kg/s]

: mass flow rate of HTS [kg/s]

: refrigeration capacity [kJ/kg]

: compression work of LTS [kJ/kg]

:compression work of HTS [kJ/kg]

m

hm

coolh

W

hW

0

2

4

6

8

10

12

300 400 500 600 700 800 900 1000

P1

T1

h1

P1

T1

h1

P2

T2

h2

P3

T3

h3

P4

T4

h4

P2

T2

h2

P2’

T2’

h2’

P3

T3

h3

P4

T4

h4

41cool hhh

※Thermophysical properties of CO2 are obtained by PROPATH12.1

T1~T4 : CO2 temperature [℃]

P1~P4 : CO2 pressure [MPa]

An example of application

Refrigeration cycle

NH3/R23 Cascade refrigerating system

Refrigeration temperature : -30℃ ~ -50℃

CF: http://www.nihon-netsugen-systems.com/products/compressor/cascading-system.html

Refrigeration temperature : -60℃ ~ -65℃

CO2 Cascade refrigerating system

Application

Food industry

http://www.japantuna.net/press34

An example of Application ( Future )

Solar collector

Solar collector

Solar energy

Thermal pump

Water

Turbine Generator

Power supply

Solar CO2 Rankine System

Hot water

supply tank Absorption

refrigerator

Absorption

refrigerator

Turbine

Thermal pump

Hot water

supply tank

CO2

Power

Cool water

Hot water

Super critical CO2 solar generation, air conditioning, hot water supply system