Modelling Energy Demand for a Fleet of Hydrogen-Electric Vehicles Interacting with a Clean Energy Hub

Faraz Syed*, Michael Fowler, David Wan, Yaser Maniyali

Green Energy & Fuel Cell Lab, Chemical EngineeringUniversity of Waterloo

International Conference on Hydrogen Production, Oshawa. May 3rd – 6th 2009

Presentation Outline

1. Introduction2. Model Development3. Results4. Conclusions5. Future Work

2

Introduction

• Electricity: changes on supply-side:• Increasing use of distributed power

generation• Increasing use of renewable energy

(intermittent)

• Electricity: changes on demand-side:• Anticipated population growth• Increasing electricity demand for

transportation

3

Role of Hydrogen

• Hydrogen will be important for supply- and demand-side issues

• Supply side:• Electricity storage for peak load shaving

& renewable enabling

• Demand side:• Hydrogen-based transportation (reduced

impact, increased energy security)

4

Electrification of Transportation

5

CVs• Gasolin

e

HEVs• Gasoline

PHEVs• Electricity,

some gasoline

PFCVs• Hydrogen

& electricity

Conventional Vehicles

Electrification of Transportation

6

CVs• Gasolin

e

HEVs• Gasoline

PHEVs• Electricity,

some gasoline

PFCVs• Hydrogen

& electricity

Hybrid Electric Vehicles

Electrification of Transportation

7

CVs• Gasolin

e

HEVs• Gasoline

PHEVs• Electricity,

some gasoline

PFCVs• Hydrogen

& electricity

Plug-in Hybrid Electric Vehicles

Electrification of Transportation

8

CVs• Gasolin

e

HEVs• Gasoline

PHEVs• Electricity,

some gasoline

PFCVs• Hydrogen

& electricity

Plug-in Fuel Cell Vehicles

Integrated Energy System & Hubs• New integrated energy system (also

called the hydrogen economy) likely• Energy hubs will form interface

between supply & demand to provide:• Electricity storage for peak load shaving

& renewable enabling• Demand-side management (e.g. PHEV

charging)

9

Schematic of systems and energy interactions in the clean energy hub model 10

Clean Energy Hub

Electricity system

Hydrogen system

H2 storage

E H2 H2 E

Electricity Supply(10 wind turbines @ 20MW total capacity)

Energy Demand

Vehicle fleet(4,000 vehicles)

ElectricityHydrogen

Legend

Model Development: Clean Energy Hub

Model Logic for Clean Energy Hub

If Supply > Demand

Store excess electricity as hydrogen

If Demand > Supply

Generate electricity from hydrogen

11

Model Development: Fleet

• Fleet consists of 4,000 hydrogen-electric vehicles

• Bottom-up approach: individual vehicle actions were simulated

• Review of existing vehicle models (e.g. PSAT & CRUISE):• each component is modelled• intended for vehicle designers• too complex & computationally expensive

12

Vehicle architecture represented in PSAT 13

Fleet Model: Architecture

• Developed simplified vehicle architecture

• Designed to be generic & applicable to variety of real vehicle architectures

• Two (2) energy inputs (electricity & hydrogen)

• Two (2) energy storage devices (ESS & HSS)

• Two (2) energy conversion devices

14

Simplified vehicle architecture used for fleet model 15

Vehicle

ESS

HSS

Electricity system

Hydrogen system

E KE

H2 KE

Wheels

Legend Electricity Hydrogen Kinetic Energy

Fleet Model: Architecture

• Electricity Storage System (ESS) parameters:• Capacity [kWh]• State-of-charge (SOC) [%]

• Hydrogen Storage System (HSS) parameters:• Capacity [kg]• Amount stored [kg]

16

Energy usage during travel modes 17

Charge depleting Charge sustaining

ESS

Stat

e of

Cha

rge

(%)

Distance travelled

HSS

stor

age

(kg)

Fleet Model: Daily Operation

Travellingperiod

8 am – 11 pm

Charging period

12 am – 7 am

18

Fleet Model: Daily Operation

• Charging period is modelled every time-step (1 hr)

• Travelling period is modelled over entire period

19

0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 540%

50%

100%

Simulation Time [h]

SOC

[%]

Charging & travelling period demonstration 20

charging travellingtravelling charging

Smart Charging/Charging Strategy

• Different charging strategies can be used:• Full-power charging• Minimum-power charging

• Full-power charging is simplest, limited only by charging station power

• Minimum-power charging targets full ESS charging over entire charging period 21

Fleet Model: Travel Simulation

• Daily travel distance (i.e. driver behaviour) is an input

• Stochastic model in place of actual data• Gaussian distribution with mean of 30 km &

standard deviation of 1 km

22

Daily travel

distance

Energy depletion function

Energy depletion function for ESS & HSS 23

START

STOP

Does the given travel distance exceed the charge depleting range?

Deplete the ESS completely and subtract charge depleting range from

travel distance

NODeplete the ESS accordingly

YES

Does remaining distance exceed the charge sustaining range?

NODeplete the HSS accordingly

Deplete the HSS completely and subtract charge sustaining range from

travel distance

YES

Return total distance travelled

Other Model Parameters

Parameter Value Unit

ESS capacity 10 kWh

ESS initial SOC 100 %

HSS capacity 4 kg

HSS initial mass 4 kg

Charge-depleting electricity consumption 6.5 km/kWh

Charge-sustaining hydrogen consumption 70 km/kg

Maximum charging station power 1.65 kW

24

Parameters for an individual fuel cell electric vehicle

Simulation

• Simulation run for 7-day period in January

• Two scenarios compared:• Case A: Full-power charging• Case B: Minimum-power charging

25

Sample case electricity demand and supply profiles during charging26

12 AM 1 AM 2 AM 3 AM 4 AM 5 AM 6 AM0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

Full-power charging Minimum-power chargingWind Power

Simulation Time [h]

Pow

er [M

W]

Simulation Results

• Demand exceeded supply in both scenarios• hydrogen system filled the supply deficit to

ensure supply reliability.

• Effect of switching from full-power to minimum-power charging strategy:• 14.6% decrease in peak demand• 40.8% decrease in supply deficit

• electricity generation capacity of hydrogen system can be reduced by up to 40.8% as well

27

Conclusions

• Developed a “bottom-up” fleet model for hydrogen-electric vehicles (PFCVs)

• Model output: fleet load profile (electricity & hydrogen)

• Demonstrated smart-charging simulation through charging strategy

28

Future Work

• PHEV fleet modelling: gasoline instead of hydrogen

• Per-hour travel modelling• Need better driver behaviour data

• Stochastic charging: no fixed charging period for fleet

29

Thank You

Questions?

Faraz SyedChemical EngineeringUniversity of Waterloo

f2syed@uwaterloo.ca