Technologies for VehicularEnergy Efficiency

Amir A. M. Oliveira Jr. (UFSC)Rafael Bravo (IFSC)

Victor Juliano de Negri (UFSC)Rafael de Matos Goulart (UFSC)

September 2nd-3rd, 2014.

1. Why energy efficiency for trucks

2. The waste

3. Strategies of energy recuperation

4. A hydraulic-pneumatic alternative

5. Conclusion

Outline

2

Fuel 42% 38% 37% 36% 23%

Available, kW 380 160 145 141 137 86

Component Engine Auxiliary Transmission Driveline Tires Drag

Losses, kW 220 15 4 4 51 86

Efficiency, nond.

42% 38% 97% 97% 63%

Powertrain efficiency

3

Tank Wheel

Energy dissipated in steady state: Class 8 long-haul

Fraction of energy actuallyused to move the useful cargo

4

Passenger car TruckVehicle weight, kg 1500 13608Useful weight, kg 75 20412Ratio useful/vehicle 0.05 1.5Efficiency Tank-to-Wheels 13% 23%Energy loss Drag 7% 7%

Acceleration 6% 16%Fraction useful energy 0.3% 24%

23%

Vehicle efficiency

Why is efficiency important?

Annual energy consumption in Brazil (2011):• Primary energy = 229 Mtoe

18 % electricity + 82 % thermal

• Transport = 74 Mtoe = 32 % of total• Diesel oil = 34 Mtoe = 46 % of transport

(more than total in Chile)

To put in context:• Record generation of Itaipu (2010) = 8.5 Mtoe

4 Itaipus-equivalent burned as diesel oil annually

5

Efficiency = ton x km/liters

Three-steps strategy:1. Reduce vehicle weight, losses and other energy needs:

• Reduce air drag and rolling resistance• Reduce weight• Reduce idling time• Reduce cabin heating/cooling loads

2. Increase efficiency and downsize the powertrain:• Increase power train efficiency• The smallest powertrain needed for the job• Recover waste energy

3. Increase load capacity:• Increase cargo volume – long-combination vehicle

6

Approach to improve vehicle efficiency

Hybrid systems:1. Thermal (internal combustion engine) –

Limited by Carnot´s Cycle2. Mechanical – No theoretical limit3. Electrical4. Hydraulic/pneumatics – Limited by heat transfer

7

Recover waste energy

Key Distributed Power Program Quarterly Review (2001)8

Hybrid systems

Hydraulic/pneumatics:

Advantages

• Increased energy density

• Enlarged energy range

• Pneumatic accumulator is cleaner

Disadvantages

• Small energy density / larger sizes of accumulator

• Lower thermal efficiency of the accumulator

• Internal combustion engine does not easily work as a compressor

11

Hydraulic/pneumatics versus Electric

Simulation - Vehicle dynamics

12

𝐹𝑡 − 𝐹𝐴 − 𝐹𝑅 − 𝐹𝑓 − 𝐹𝐺 = 𝑚𝑣

𝑑𝑣𝑣𝑑𝑡

1 +𝐽𝑒𝑞

𝑚𝑣 𝑟𝑤2

𝐹𝐴 =1

2𝜌𝑎𝑟 𝑥𝑣

2 𝐴𝑓 𝐶𝐷,𝐴

Drag:

𝐹𝑅 = 𝑚𝑣 𝑔 𝐶𝑅 𝑐𝑜𝑠𝛼Rolling:

Dynamics:

Objectives:

Energy storage during:• Breaking when needed• Keeping the speed while descending

Use of stored energy for:• Compressing air for auxiliaries• Acceleration• Other auxiliaries using a hydraulic pump

13

Description of the hybrid system

Modes of energy recovery:

1. Breaking and charging the acumulator

2. Compression of air and use of excesshydraulic energy

14

Description of the hybrid system

15

Hybrid Transmission

Gear B

ox

Differentia

l

Sha

ft 2

Sha

ft 1

Pneumatic

circuits

G

1P

2Z1

0M

Output 1

Output 2

Output 3

HydropneumaticSystem

Preliminary results

16

VOLVO 9700 Bus: 12.3 m, RHD, 4x2, Euro 5

Maximum load: 19 tonEngine power: 320 kW (420 Hp)

17

Preliminary results

Variable Value

Vehicle speed 13.9 m/s (50 km/h)

Road inclination 3º

Pneumatic circuit pressure 0.5 Mpa

Volume of air reservoir 0.1 m3

Hydraulic pump 180 cm3/rot

Hydraulics working pressure 35 Mpa

Pre-charge pressure 10 Mpa

Volume of hydraulic accumulator 64 liters

1. Horizontal breaking

18

19

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5 20,0 22,5 25,0

0

10

20

30

40

50

Velocidade do Veiculo

Velo

cid

ade (

km

/h)

0 5 10 15 20 25 30

0

40

80

120

160

Deslo

cam

ento

(m

)

Distancia Percorrida

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5 20,0 22,5 25,0

0

250

500

750

1000

1250

1500

Rotaçao da Bomba

Velo

cid

ade (

rpm

)

Tempo (s)

0 5 10 15 20 25 30

0

500

1000

1500

2000

2500

3000

Velo

cid

ade (

rpm

)

Rotaçao do Motor Hidraulico

Tempo (s)

Vehicle speed and distance,Speed of pump and hydraulic motor

20

0 5 10 15 20 25

0

75

150

225

300

Pressao hidraulica

Pressao no acumuladorPre

ssa

o (

ba

r)

Tempo (s)

0 5 10 15 20 25

0

1500

3000

4500

6000

Torque da bomba

To

rqu

e (

N.m

)

Pump torque,Pressure in the hydraulic system and accumulator

21

0 5 10 15 20 25 30

5

6

7

8

Pressao no reservatorio

Pre

ssa

o (

ba

r)

Tempo (s)

0 5 10 15 20 25 30

0

100

200

300

400

500

600

Dissipada

Reservatorio

Acumulador

En

erg

ia (

kJ)

Energy dissipated and accumulated in the reservoirand accumulator,

Pressure in the reservoir

2. Breaking while descending

22

23

0 50 100 150 200

42

45

48

51

54

57

60

Velocidade do Veiculo

Ve

locid

ad

e (

km

/h)

0 50 100 150 200

0

500

1000

1500

2000

2500

3000

3500

De

slo

ca

me

nto

(m

)

Distancia Percorrida

0 50 100 150 200

1300

1400

1500

1600

1700

1800

Rotaçao da Bomba

Ve

locid

ad

e (

rpm

)

Tempo (s)

0 50 100 150 200

0,00

0,25

0,50

0,75

1,00

De

slo

ca

me

nto

re

lativo

Motor Hidraulico

Tempo (s)

Fig. 46. Resposta do sistema híbrido

Vehicle speed and distance,Speed of pump and hydraulic motor

24

0 10 20 30

0

1500

3000

4500

6000

Torque de frenagem

Torq

ue (

N.m

)

Tempo (s)

0 10 20 30

0,00

0,25

0,50

0,75

1,00

Bomba Hidraulica

De

slo

cam

ento

Rela

tivo

Pump displacement (relative) and torque

25

0 4 8 12 16 20

100

150

200

250

300

350

Acumulador

CircuitoPre

ssa

o (

ba

r)

Tempo (s)

0 4 8 12 16 20

0

700

1400

2100

2800

3500

Motor HidraulicoVe

locid

ad

e (

rpm

)

Speed and Pressure in the hydraulic motor

26

0 50 100 150 200 250

0

10

20

30

40

50

60

Pressao no reservatorioPre

ssa

o (

ba

r)

Tempo (s)

0 50 100 150 200 250

0

50

100

150

200

250

Temperatura no reservatorioTe

mp

era

tura

(°C

)

Temperature and Pressure in air reservoir

27

0 50 100 150 200 250

0

50

100

150

200

250

Compressor

Motor Hidraulico

To

rqu

e (

N.m

)

Tempo (s)

0 50 100 150 200 250

0

300

600

900

1200

1500 Reservatorio

Acumulador

En

erg

ia (

kJ)

Energy accumulated in the reservoir and accumulator,Torque in the compressor and pump

28

0 100 200 300 400

0

15

30

45

60

75

90

Pressao no Reservatorio

Pre

ssa

o (

ba

r)

0 100 200 300 400

0

1000

2000

3000

4000

5000

Ve

locid

ad

e (

rpm

)

Motor Hidraulico

0 100 200 300 400

0

500

1000

1500

2000

2500

Dissipada hidraulicamente

Reservatorio de ar

En

erg

ia (

kJ)

Tempo (s)

0 100 200 300 400

0,0

0,2

0,4

0,6

0,8

1,0

De

slo

ca

men

to R

ela

tivo

Motor Hidraulico

Tempo (s)

Conditions in the hydraulic system for higher energy

Conclusions

• The system proposed stores and uses thestored energy.

• The torque available during breaking is largerthan needed.

• The energy stored in the accumulators can beused while the vehicle is moving.

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• The hydro-pneumatic system has 3 times more capacity than commercially available systems

• Possible improvements:

– Increase pressure in the hydraulic system for 42 Mpa

– Increase compressor capacity

– Use thermal insulation in the reservoirs

– Use na electrical generator in parallel with the pump

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Conclusions

Prof. Amir Antonio Martins Oliveira Jr.

Dept. of Mechanical Engineering – UFSC

amir.oliveira@gmail.com

Thank you.

31

Acknowledgement: Volvo Group Trucks TechnologyVOLVO GTT - Advanced Technology & ResearchDr. Roberson Assis de OliveiraDr. Flavio Prezesniak