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Don J. Cleland
Centre for Postharvest & Refrigeration Research
Massey University, Palmerston North, New Zealand
26 May 2015
Refrigeration Technology –
Evolution, Revolution or
Back to the Future
• Refrigeration in NZ
• Alternative Technologies
• Refrigerants
• Vapour Compression Advances
• Conclusions
• Prediction is difficult; especially about the future! (Niels Bohr)
Overview
• export cold chain – trading nation at the bottom of the world
– exports are 25% of GDP
– ≈50% of exports are food
– about half of export food is refrigerated
• domestic cold chain
• space heating/cooling via heating pump/air
conditioning growing rapidly
• about 25% of electricity use
Refrigeration in NZ
NZ Refrigeration
Consumption
4
Household, 5,824.49
Slaughtering and Meat Processing, 3,238.63
Retail Trade - Food, 2,445.03
Dairy Products, 1,710.94
Hotels/Motels 891.723
Wholesale Trade - Food, 826.554
Dairy Agriculture, 671.443
Fishing and Hunting, 658.594
Other Food Proc. Sectors,
615.694
Refrigeration End-Use
Energy Consumption (TJ)
Source: EECA Energy End Use Database, March 2011
Refrigeration Fraction of
Total End-Use Energy (NZ)
Household, 13.3%
Slaughtering & Meat Processing,
49.3%
Retail Trade - Food, 60.5%
Dairy Products, 15.4%
Hotels/Motels 26.0%
Wholesale Trade - Food, 92.6%
Dairy Agriculture, 19.8%
Fishing and Hunting, 94.5%
Other Food Proc Sectors, 11.5%
Proof that the World is Getting Warmer
Updated Study – Larger Budget!
GHG Emissions
Improved Sustainability
– Energy Efficiency
• indirect GHG impact (energy) >> direct GHG impact (refrigerant leakage)
• mitigated if renewable energy supply
• minimize heat loads first (e.g. insulation; air infiltration, fans, lights, equipment, product, defrost)
• then improve refrigeration system efficiency
• auxiliary energy not just compressors (e.g. fans & pumps)
• 20-50% improvement economically feasible
• shift from lowest first cost to lowest life cycle cost
• greater system knowledge by designers, operators and maintenance engineers
COP system
loadheat energy
minimize
maximize
Vapour Compression
Cycle
pumpsfanscomp
removedrejected
QQQ
COP
and/or
inputenergy
coolingor heating useful
Evaporation
Condensation Thro
ttling
• Alternative Technology (Revolution)
• Improved Technology and Heat Pumping (Evolution)
• Refrigerants (Back to the Future)
• Change in Habits (Back to the Future)
Opportunities
• Possibilities
– acoustic
– magnetic
– thermo-electric (Peltier)
– vortex tube
– Brayton (air) cycle
– Stirling cycle
– absorption/adsorption
• Issues
– low efficiency in practice
– low capacity
– high cost
• Niche applications e.g. Peltier for low noise
• Absorption if low cost heat at reasonable temp.
Revolution - Alternative
Technologies
Absorption HPs & Heat
Transformers
• Absorption HPs
– output < 100oC (condenser), T < 65oC
– COP = 1.1 to 1.8
– heat source > Thot
• Heat Transformers
– output < 150oC (absorber), T < 50oC
– COP = 0.4 to 0.5
– heat source < Thot but not waste heat
Expanders
Evaporation
Condensation Expansio
n
Expander
• usually boot-strapped
to compressor
• liquid + vapour
challenge
• still experimental
rather than commercial
The Perfect
Refrigerant
Planet (Environment) - zero ODP
- low GWP
- energy efficient
- low toxicity
- unstable (short
atmospheric life)
Prosperity (Economic) - low cost
- high performance
- energy efficient
- safe
- stable
- wide material
compatibility
- low cost equipment
- low GWP
People (Society) - safe
o non-flammable
o low pressure
o distinctive colour or
smell
- low toxicity
- energy efficient
- low cost equipment
Refrigerants
Source: Danfoss
Refrigerants – Back
to the Future
• CFCs – e.g. R12, R502
– phased out under Montreal Protocol
• HCFCs – e.g. R22, R141b, some drop-in blends
– phasing out under Montreal Protocol by 2020
• HFCs – e.g. R134a, R404A, R407C, R410A, R417A, R507
– subject to Kyoto Protocol
• HFOs – low GWP replacement for HFCs e.g. HFO-1234yf
• Natural Refrigerants (NRs) – e.g. ammonia (R717), CO2 (R744), air (R729),
hydrocarbons (HCs) including propane (R290), iso-butane (R600a) and ethane (R170)
Refrigerant Choice (appropriate temperature range)
Criteria HCFCs HFCs HFOs NRs
Refrigerant Cost (no levy)
low/medium medium high low
System Cost medium medium medium high
Capacity good good good very good
Energy Efficiency good good good very good
ODP yes no no no
GWP (levy) high high low very low
Safety (e.g. flammability, toxicity, high pressure)
good generally
good
good except flammability
often significant risks
Oil Compatibility traditional synthetic synthetic wide
Coldstore Fire –
Propane Refrigerant!
Improved Sustainability
- Refrigerants
• no perfect refrigerant (flammability hard to avoid)
• move to those with no ODP & low or zero GWP without reducing energy efficiency (often NRs)
• minimise charge (system design)
• minimise leakage (improved system design, maintenance practices and disposal systems)
• direct emissions <15% of total GHG impact
• worst for transport & field-erected retail & industrial systems
• low for factory-built hermetic systems but disposal issue as large numbers
Performance of
Alternatives
Refrigerant HFC-404A Alternative
GWP 3260 150
Charge (kg) 5 5
Leakage (% pa) 5 5
Energy Use (kWh pa) 25,000 +5%
TEWI (kg CO2) 388,855 394,388 (+1.4%)
Levy + Energy Cost ($) 656+37,500 = 38,156 30+39375 = 39,405(+3.3%)
o 15 year equipment life
o 90% refrigerant recovery
o Electricity emission factor of 1 kg CO2/kWh
o Electricity cost of $0.1/kWh
• If charge & leakage low, then GWP less important than efficiency
Evolution • Load Reduction
– super-insulation
– lighting e.g. LED
– VSDs (inverters) for fans & pumps
– fan and motor efficiencies
– defrost optimisation; anti-frost surfaces
– door protection &/or desiccant dehumidification
– ambient cooling
– load shifting
• System Efficiency – oversized and enhanced HXs
– compressor efficiencies
– oil free compressors
– improved temperature matching e.g. CO2 transcritical
– higher pressure refrigerants (lower PR, lower pressure drops; smaller equipment)
– multi-staging
– evaporative heat rejection (vs air)
– improved controls
• Heat Pump Heating – space heating, water heating, drying, distillation, process heating
– air-source vs ground-source vs waste heat vs cooling integrated
open doors
floor
walls
ceiling solar radiation
product
lights
people
forklifts
fans defrost
Lighting
Lamp
98%
2
Fitting
50%
1
Wiring
1%
100
Customer
Primary Energy
320
% Loss
Generation
65%
112
Transmission
5%
106
Distribution
5%
101
Gas or CoalUsefulLight
1
Lamp
98%
2
Fitting
50%
1
Wiring
1%
100
Customer
Primary Energy
320
Primary Energy
320
% Loss
Generation
65%
112
Transmission
5%
106
Distribution
5%
101
Gas or CoalUsefulLight
1Incandescent via Huntly
Lamp
90%
2
Fitting
50%
1
Wiring
1%
20
Customer
Primary Energy
64
% Loss
Generation
65%
22
Transmission
5%
21
Distribution
5%
20
Gas or CoalUsefulLight
1
Lamp
90%
2
Fitting
50%
1
Wiring
1%
20
Customer
Primary Energy
64
% Loss
Generation
65%
22
Transmission
5%
21
Distribution
5%
20
Distribution
5%
20
Gas or CoalUsefulLight
1
CFL/LED via Huntly
Evaporator Fans
via coal power station - system
inefficiencies – extra pressure drops;
food packaging
via CCGT
via CCGT – improved system & fan;
from 8 to 7 if refrig. COP from 2 to 3;
also motor efficiency potential
Case Study – Blast
Freezing Cell • 12 stillages; each with 36 cartons; 15 kg
per carton
• freeze in 44 hours at -30oC (-22oF)
• single fan 1250 mm diameter, 8 aerofoils at 30o pitch angle, motor rated 11 kW at STP, 6 pole, 975 rpm, 22.7 A FLA at 415 VAC, 60 mm deep inlet cone, rated at 20 m3/s @ 300 Pa SP
(Odey, 2006)
• baffling above and beside each stillage to minimise air bypass
• full fan inlet cone
• full fan diffuser
• fan inlet air turning vanes
• fan discharge air turning vanes
Comparison
Unmodified Modified
Fan Power 8.7 kW 4.0 kW
Fan Pitch 30o 22o
Fan Speed 960 rpm 720 rpm
Freezing Time < 44 h < 44 h
Pressure Drop bends, coils product stack
Fan Inlet unstable vortex more stable
Uniformity poor good
Air Flow 22 m3/s (47,000 cfm) 18 m3/s (38,000 cfm)
Pressure Drop 270 Pa (1.08” H2O) 160 Pa (0.64” H2O)
• same velocity over product for lower total flow and fan power
VSD - Screw
Compressor Unloading
0
10
20
30
40
50
60
70
80
90
100
110
0 10 20 30 40 50 60 70 80 90 100
Percentage of Full Load (%)
Slide Valve
VSD
hp
(%
)
VSD - Evaporator Fans
• air movement for
– heat removal by evaporator
– product heat transfer
– temperature uniformity
• fans up to 30% of heat load
• energy for fans plus energy to
remove fan heat
• reduce fan speed in low load periods
0
10
20
30
40
50
60
70
80
90
100
110
40 50 60 70 80 90 100
Cooling Capacity (%)
Fa
n P
ow
er
(%)
0
10
20
30
40
50
Fre
qu
en
cy (
Hz)
Fan Power
Frequency
Assumes %5 VSD Losses
Case Study - Coldstore
• design heat load of 100 kW
• 4 5 kW fans
• peak load of 80 kW (12 hr/day, 6 days/wk, 11 months of year)
• off-peak load of 60 kW
• refrigeration COP of 2
• energy cost
– $0.10/kWh (peak)
– $0.05/kWh (off-peak)
On/Off VSD
Cost low $5000
Peak Capacity 90% 90%
Peak Power 18 kW (90%) 14 kW (70%)
Peak Savings 10296 kWh 30888 kWh
Off-Peak Capacity 70% 70%
Off-Peak Power 14 kW (70%) 5 kW (25%)
Off-Peak Savings 44928 kWh 112320 kWh
Air distribution uneven uniform
Total Savings 55224 kWh 143208 kWh
Total Cost Savings $3276 $8705
26 28 30 32 34 36 380
20
40
60
80
100
120
140
160
Saturated Condensing Temperature [°C]
Po
we
r [k
W]
Compressor
Compressor+Condenser
Condenser
Axial Fan
Tcond,opt = 30.6°C
Toa,wb=25.6°C
VSD - Evaporative
Condensers
70
75
80
85
90
95
100
105
110
800 900 1000 1100 1200 1300 1400 1500
Discharge Pressure (kPa.g)
Perc
en
tag
e E
nerg
y U
se (
%)
70
75
80
85
90
95
100
105
110
Perc
en
tag
e C
oo
lin
g C
ap
acit
y (
%)
Energy Use
Cooling Capacity
41.036.238.733.630.928.024.921.5
Saturated Condensation Temperature (°C)
low, high
high,high
off, low
low,low
off,off
off, high
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90 100
Percentage Full Load Capacity
Pe
rce
nta
ge
Fu
ll L
oa
d P
ow
er
On/Off
Two 2-Speed
VSD
50% of Design Load
150
160
170
180
190
200
210
220
230
240
250
600 700 800 900 1000 1100 1200 1300 1400 1500
Discharge Pressure (kPa.g)
To
tal P
ow
er
(kW
)
On/Off
VSD
Two-Speed
Saturated Condensation Temperature (°C)
41.036.238.733.630.928.024.921.517.813.8
WB=8oC
WB=16oC
• Design
• 1000 kWr at -5oC
• 35oC SCT with 20oC WB
• VSD saves about 20 kW
relative to on/off cycling
• optimum discharge pressure
but < 10oC approach to WB
• float discharge pressure (fully
loaded fans) unless:
• very low heat load
• approach to WB <10oC
0.0
5.0
10.0
15.0
20.0
25.0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Av
era
ge
mo
nth
ly W
B T
em
pe
ratu
re (
°C)
Colder May Not Be
Worse (Visser, 2006)
Design 1 2 3 4 5
Air Temp. (oC) -35 -36 -38 -40 -43
Air Velocity (m/s) 6 5 4 3 2
Suction Temp. (oC) -40.5 -42.2 -44.5 -47.2 -50.5
Fan Power (kWe) 131 81 43 17 8
Refrig. Load (kWr) 517 467 429 403 395
COP 1.52 1.48 1.34 1.21 1.10
Comp. Power (kWe) 339 315 321 334 361
Total Power (kWe) 470 416 364 351 369
blast freezing 95 tonnes/day in a 24 hour cycle
Multi-Staging, Cascades
& Secondaries
• Use refrigerants in optimal temp. range
• Minimise & isolate charges of high GWP, flammable or toxic refrigerants
• “Safe” refrigerants in populated areas
• Energy penalty due to extra temp. difference
• CO2 likely low stage & secondary – safe & low cost
– efficient
– low pumping power/pressure drop
– low mass & volumetric flows
– equipment availability & cost improving
• High stage refrigerants situation specific
Frozen Warehouse - 19,000 m2 (Edwards, 2006, 2008)
Relative
Performance
System Capital Cost
Energy
Factor
Annual Energy
Life Cycle Costs (20 yr)
DX R404A $2,500,000 1.2 $1,00,000 $25,250,000
DX Ammonia $3,063,000 1 $813,000 $22,063,000
Pumped Ammonia $3,125,000 0.8 $650,000 $17,625,000
Secondary CO2 $3,625,000 0.87 $706,000 $19,875,000
Secondary T40 $3,750,000 +$50,000 $756,000 $20,875,000
Cascade CO2 $3,375,000 0.84 $688,000 $19,250,000
Meat Freezing (5200 kg/h) (Visser, 1996)
Type of Freezer Air-Blast Plate
Heat Load 658 kWr (187 TR) 627 kWr (178 TR)
Operating Conditions -35/-10/+35oC
-31/+14/+95oF
-32.5/-10/+35oC
-26.5/+14/+95oF
Evap. Fan Power 93 kWe -
Pumps and Condensers 30 kWe 37 kWe
Compressor Power 332 kWe 300 kWe
Hydraulics & Conveyors 15 kWe 8 kWe
Dehumidification - 10 kWe
Total Power 470 kWe 355 kWe (-24%)
Freezing Time 47 h 18 h
Carton Stacking Density uneven & unstable flat (10% savings)
• transcritical if gas cooling matches process
• CO2 advantages
– good heat transfer characteristics
– high pressure
• low PR
• small equipment
– CO2 glide matches water rise
Temperature Matching
289,56
35 ºC
349,37
433,46
441,02
151,46
59,81
479,01
37,99
s = 2032,93
544,19
128,83 ºC
65,18
30,47
100
V = 0,01576
299,8
141,22
91,65
108,6 ºC
530,5851,57
119,18 ºC
537,6758,66
COP = 151,46 / 65,18 = 2,324COP = 141,22 / 58,66 = 2.407COP = 91,65 / 51,57 = 1,777
289,56
35 ºC
349,37
433,46
441,02
151,46
59,81
479,01
37,99
s = 2032,93
544,19
128,83 ºC
65,18
30,47
100
V = 0,01576
299,8
141,22
91,65
108,6 ºC
530,5851,57
119,18 ºC
537,6758,66
COP = 151,46 / 65,18 = 2,324COP = 141,22 / 58,66 = 2.407COP = 91,65 / 51,57 = 1,777
COP = 151,46 / 65,18 = 2,324COP = 141,22 / 58,66 = 2.407COP = 91,65 / 51,57 = 1,777
Load Shifting Potential
(NZ, 2000)
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90 100
Percentage Avoided
Co
st
($/M
Wh
)
0
10
20
30
40
50
60
70
80
90
100
Perc
en
tag
e M
arg
in R
ela
tive t
o A
vera
ge P
rice (
%)
Ranked Cost
Average Cost Avoided
Average Price Paid
Percentage Margin
• customer inconvenience
• control systems
– demand inelastic to price
– automated
• stored product provides thermal inertia
• product temperature is critical
• simple peak tariff avoidance practised
• optimised?
– length of shift
– time of shift
– risk to product
Coldstore Load Shifting
-30
-26
-22
-18
-14
-10
0 6 12 18 24 30 36 42 48
Time after 00:00 am on Wednesday 2/9/98 (hours)
Air
Te
mp
era
ture
(oC
)
10 cm above bottom pallet
evaporator air-off
regulatory probe
0
20
40
60
0 6 12 18 24 30 36 42 48
Time after 00:00 am on Wednesday 2/9/98 (hours)
Do
or
Op
en
Tim
e (
%)
Refrig. shed
both fans off
Refrig. restored
both fans on
Refrig. shed
one fan on
Refrig. restored
both fans on
Defrost
-28
-26
-24
-22
-20
0 24 48 72 96 120 144
Time After 00:00 am on Thursday 3/9/98 (hours)
Pro
duct
or
Air
Tem
pe
ratu
re (
oC
)
prod. centre (1)intermediate (2)
prod. outside (3)air (regulatory probe)
Refrig. shed
Suction set to -28oC
Refrig.
restoredDefrost Refrig.
restored
Refrig. shed
Suction set
to -32oC
3
2
2 2
3
31
11
X Y
Z
X Y
Z
CRM LAMBS PPASCRM LAMBS PPAS
1) Winter Tariff, W eek One, Days 35 to 39 inclusive
2) Winter Tariff, W eek Two, Days 42 to 46 inclusive
3) Modified W inter Tariff, W eek One, Days 49 to 53 inclusive
4) Modified W inter Tariff, W eek Two, Days 56 to 60 inclusive
0
100
200
300
400
500
0:00 6:00 12:00 18:00 0:00
Time of Day
Usag
e (
kW
)
0
2.5
5
7.5
10
12.5
Cost (c
/kW
h)
0
100
200
300
400
500
0:00 6:00 12:00 18:00 0:00
Time of Day
Usag
e (
kW
)
0
2.5
5
7.5
10
12.5
Cost (c
/kW
h)
0
100
200
300
400
500
0:00 6:00 12:00 18:00 0:00
Tim e of Day
Us
ag
e (
kW
)
0
2.5
5
7.5
10
12.5C
ost (c
/kW
h)
0
100
200
300
400
500
0:00 6:00 12:00 18:00 0:00
Time of Day
Usag
e (
kW
)
0
2.5
5
7.5
10
12.5
Cost
(c/
kW
h)
Domestic Freezer
Load Shifting
-25
-20
-15
-10
-5
0
8:24 9:24 10:24 11:24 12:24 13:24 14:24 15:24 16:24
Time
Tem
pera
ture
(°C
)
bottom
top
vertical
chest
-20
-15
-10
-5
0
5
7:12 8:12 9:12 10:12 11:12 12:12 13:12 14:12 15:12 16:12 17:12
Time
Tem
pera
ture
(°C
)
top
bottom
middle
Thermostat setting
1 4 7 Average
Power use (during on-time) per unit (W) 142.2 133.5 120.6 132.1
Average unit % on-time 37% 51% 53% 47%
W available per unit 58 78 78 71
no. of units in NZ (1998) 447,500 447,500 447,500 447,500
MW available (1998) 23.3 30.7 28.6 27.8
Transport Refrigeration
• efficiency poor (e.g. combustion engine driven, high area to volume, air
condensers, multi-temperature capability, space constraints so less
insulation, high air flows and small HXs)
• extra refrigeration energy small compared with motive power so low
incentive
• possible developments
– super insulation
– high efficiency and variable speed fans
– improved HXs (e.g. micro-channel)
– improved ventilation, defrost and compressor capacity controls
– greater protection of doors for delivery vehicles
– transferring from road to rail and/or shipping containers to refrigerated holds but
significant logistic and inter-modal cost implications
Domestic & Display
Cabinets
• driven by instruments such MEPS so level
playing field but continuous improvement
• likely incremental developments
– different refrigerants (e.g. CO2 or hydrocarbons)
– higher efficiency compressors
– better air curtains for or phase-out of open desk
cabinets
– improved HXs (e.g. micro-channel)
– high efficiency lights and fans
– improved controls
Custom-Built Commercial
& Industrial
• similar incremental equipment and system
design improvements e.g. electronic rather
than thermostatic expansion valves
• improved operations also a significant
opportunity e.g.
– use of night curtains in supermarkets
– closing doors in coldstores
– appropriate or floating head pressure and
suction set-points
– better expansion valve settings
EU Refrigerator Energy
Labels and MEPS
0
5
10
15
20
25
30
35
40
45
50
A+ A B C D E F G
Mark
et
sh
are
(%
)
2003 1st 3 months
1997
1990-2 (GEA)
Source: Waide, 2006
0%
2%
4%
6%
8%
10%
12%
30%
40%
50%
60%
70%
80%
90%
100%
110%
120%
130%
140%
150%
160%
170%
180%
190%
200%
210%
220%
230%
240%
Energy efficiency index (%)
Shar
e of m
odel
s/s
ale
s1999 (CECED)
1997 (CECED)
1994 Sales-weighted (ADEME)
1990-2 (GEA)
A B C D E F G
0
100
200
300
400
500
600
700
800
900
1000
050100150200250300350400450500
Electricity consumption (kWh/year)
Lif
e c
ycle
co
st
(Tu
nis
ian
Din
ars
)
MEPS for Air-
Conditioners
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
0 5 10 15 20 25 30
New Standard/ W indow (one box) Type
N ew S tandard/ S eparate Type
New Standard/ O thers
New Standard/ Duct Type
New Standard/ M ulti type
Present Standard/ W indow (one box)Type
P resent S tandard/ S eparate Type
(kW )
(CO P:A verage Heating and Cooling)
Cooling Capacity
MEPS for Space Heating Heat Pumps
2
2.2
2.4
2.6
2.8
3
3.2
3.4
0 5 10 15 20 25 30
Nominal Heating Capacity (kW)
CO
P
Pre 2007
Post 2007
• Japan (top), NZ (bottom)
• improved
– HX so lower TDs
– fan & motor efficiency
– compressor efficiency
• potential for clothing & SP changes - Florida (below)
Outdoor Temperature (oC)
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34
Sp
ac
e C
on
ditio
nin
g D
em
an
d (k
W)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
CoolingHeating
Source: Waide, 2006
Heat Pump Criteria
• Economic
• Environmental (primary energy or CO2)
• EF = emissions factor (tonne CO2/PJ)
• need to include production, transmission, distribution & standing losses
• extra capital vs savings in energy costs and emissions
heat useful tofuelfuel ofcost
yelectricit ofcost COP h
yelectricit tofuel
heat useful tofuel
heatfor fuel
yelectricitfor fuel
yelectricit tofuel
heat useful tofuel COPor COPh
h
h
h
EF
EF
Example of Criteria
• typical data – direct gas vs electrical HP
– electricity @ $0.15/kWh
– gas @ $11/GJ ($0.04/kWh)
– hgas to heat = 80% (flued gas heater)
– hgas to electricity = 33% (Huntly)
• economic criteria
• environmental (same fuel)
• much lower critical COP if electricity renewable
0380040
150
fuel ofcost
yelectricit ofcost COP heat useful tofuel ..
.
.
h
42330
801COP
yelectricit tofuel
heat useful tofuel
heatfor fuel
yelectricitfor fuel.
.
.
EF
EF
h
h
Water Heating
Primary Energy
1.25
Burner
1
Hot Water
1
Gas
% Loss 20%
Primary Energy
2
CCGT
1
Hot Water
1
Gas
% Loss 50%
Primary Energy
1.25
Burner
1
Hot Water
1
Gas
% Loss 20%
Primary Energy
2
CCGT
1
Hot Water
1
Gas
% Loss 50%
Electric Immersion via CCGT
Solar or Heat Pump via CCGT
Primary Energy
0.66
CCGT
0.33
Electricity
0.33
Gas
% Loss 50%
Hot Water
1
-200%
Free Energy from Ambient
Primary Energy
0.66
CCGT
0.33
Electricity
0.33
Gas
% Loss 50%
Hot Water
1
-200%
Free Energy from Ambient
Direct Gas
• 8% of electricity
• ≈ 85% of homes use electric HWC
• load shifting via ripple control
(controlled rate)
• “housekeeping” (insulation,
thermostat setting, leaks)
0
1
2
3
4
5
-10 0 10 20 30 40
Air temperature (°C)
Heating C
OP
at
65°C
Heat Pump Water
Heaters
Solar versus Heat Pump
Solar Heat Pump
Installed cost ≈ $3500 ??
Energy savings 60-70% > 60-70%
Cost savings ≈ $350 pa ≈ $350 pa
Payback 10 years ? years
Winter performance poor moderate
Availability good poor
Other issues control noise
refrigerants
Industrial Dehumidifier
Drying
Fresh
cold dry
air inlet
Hot
moist
air
outletWarm
humid
return
air
Fresh
cold dry
air inlet
Hot
moist
air
outletWarm
humid
return
air
0
1
2
3
4
20 40 60 80 100 120
Initial moisture content (% dry-basis)
Kil
n S
ME
R (
kg
/kW
h).
Kiln data
Kiln model
Fit to kiln data
• Specific Moisture Extraction Rate of 2.8 kg/kWh equates to COP 1.9
• tight control of heat losses
• quality and loss benefits e.g. closed system
• limits to temperatures
Living Habits
51 Weekly food for typical German and Andean families. Photographs by Peter Menzel/www.menzelphoto.com
Sustainable Energy Use?
Hunter/gatherer 0.12 kW (2500 calories per day)
New Zealander ≈ 6 kW
American ≈ 9 kW
Incident Solar ≈ 0.4 kW/m2
(8500 kW per capita; land only)
• Reversion in lifestyle unlikely
• Revolutionary new technology unlikely
• Vapour compression cycle hard to beat
• Lots of incremental improvement potential
• Shift to flammable refrigerants inevitable
• Heat pumps allow high efficiency heating and heat recovery
Conclusions
Questions