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

QQ

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