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How to be Cool
Mike Dennis
Department of Engineering
How do we get “Cool”
Air Conditioning
Condensor
Electricity consumed
here
35°C
Expansion
valve
2 kW
Compressor
8°C
Evaporator
Now you’re cool, but expensive
Peak loading on electricity grids
$ 30b required to upgrade grids over the next 20 years
2/3 of all houses in Australia have air conditioners
Big energy consumers!
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
Electricity consumed
here
35°C
Expansion
valve
2 kW
Compressor
8°C
Evaporator
Photovoltaic Air Conditioning
Condensor
Vapour Compression
Evaporator
Hot Side
N P N P N P
Peltier Cell
Cold Side
Expansion
Compression
Stirling Cycle
Thermal Air Conditioning
Dessicant / Evaporative cooling
Condensor
Gen
Absorption cooling
Evaporator
Abs
Condensor
Adsorption cooling
Evaporator
Thermal Air Conditioning
Condensor
Ejector Cycle
Evaporator
Condensor
Organic Rankine Cycle
Condensor
Evaporator
The Ejector Cycle
16m2
0.1kW
35°C
Condensor
35°C
1kW
Condensor
90°C
8°C
Evaporator
Conventional heat pump
COP = 3
8°C
Evaporator
Ejector heat pump
COPe = 0.7, COPm = 30
Cool, warm and wet
Condensor
• One system
• High solar contribution
• Three energy services
Evaporator
Winter space heating
Water heating
Leveraged Operation
Smaller collector
0.1kW
35°C
Condensor
90°C
20°C
Intercooler
Intercooler
8°C
Evaporator
0.4kW
Reduced electricity
consumption
Increased cooling effect
*** Retro-fit solution and night operation possible ***
The Ejector (compressor)
Solar
heated
primary
Evaporator
Sonic shock
seondary
•Need high secondary flow
•Need high compression ratio
Ejector thermal compressor
Inside the solar nozzle
Solar fluid
nozzle
Mixing
Chamber
Vacuum
port
Diffuser
Sensitivity
C o o lin g C a p a c it y
5 .0
Cooling Capac ity (kW)
90
85
4 .5
Tg e n
100
95
105
110
14
80
4 .0
12
3 .5
10
3 .0
2 .5
8
2 .0
Te v
1 .5
1 .0
2
4
6
0 .5
0 .0
20
25
30
35
C o n d e n s in g T e m p e r a tu r e
40
45
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