How to be Cool

Mike Dennis

Department of Engineering

How do we get “Cool”

Air Conditioning

Condensor

Evaporator

2 kW Compressor

Electricity consumed here

35°C

Expansion valve

8°C

Now you’re cool, but expensive

2/3 of all houses in Australia have air conditioners

Big energy consumers!

Peak loading on electricity grids

$ 30b required to upgrade grids over the next 20 years $

Don’t be silly…

Greenhouse Neutral House

Thermal (Solar hot w ater collectors)

Electrical (Photvoltaic collectors)

Houses as distributed power stations

Solar Air Conditioning

Condensor

Evaporator

2 kW Compressor

Electricity consumed here

35°C

Expansion valve

8°C

Photovoltaic Air Conditioning

Condensor

Evaporator

Hot Side

Cold Side

N P N P N P

Expansion Compression

Vapour Compression

Peltier Cell

Stirling Cycle

Thermal Air Conditioning

Condensor

Evaporator Abs

Gen

Condensor

Evaporator

Absorption cooling

Adsorption cooling

Dessicant / Evaporative cooling

Thermal Air Conditioning

Condensor

Evaporator

Condensor

Condensor

Evaporator

Ejector Cycle

Organic Rankine Cycle

The Ejector Cycle

Ejector heat pump

Condensor

Evaporator

Condensor

Evaporator

Conventional heat pump

8°C

35°C

1kW

COP = 3

35°C

8°C

0.1kW

16m2

COPe = 0.7, COPm = 30

90°C

Condensor

Cool, warm and wet

Evaporator

Winter space heating

Water heating

• One system

• High solar contribution

• Three energy services

Leveraged Operation

Intercooler

Condensor

Intercooler

Evaporator

8°C

0.4kW

20°C

35°C0.1kW

90°C

Reduced electricity consumption

Increased cooling effect

Smaller collector

*** Retro-fit solution and night operation possible ***

The Ejector (compressor)

Solar heated primary

Sonic shock

•Need high secondary flow

•Need high compression ratio

Evaporator

seondary

Ejector thermal compressor

Solar fluid nozzle

Vacuum port

Mixing Chamber

Diffuser

Inside the solar nozzle

Sensitivity

Cooling Capacity

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

20 25 30 35 40 45

Condensing Temperature

Coo

ling

Cap

acity

(kW

)

Tgen 8085

90 95 100 105 110

Tev

2 4 6

8

10

12

14

Progress to Date

This work is supported by the Faculty Research Grant Scheme (FRGS)

Research Directions

Improved flexibility

Variable geometry ejector

Smart control and actuation strategies

Improved cogeneration and integral thermal storage

Improved performance

Dynamic optimisation of coupled operation

Liquid pressure amplification

Improved CFD models

Mixing phenomena