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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