Title: Hybrid Solar Vehicles: Perspectives, Problems, Management Strategies
1Hybrid Solar Vehicles Perspectives, Problems,
Management Strategies
- HYATT REGENCY
- NOVEMBER 13-14, 2008
- ISTANBUL
I.Arsie, G.Rizzo, M.SorrentinoDIMEC, University
of Salerno, Italy
2Outline
- Introduction
- HSV models and results
- Optimization of Management Strategies
- The Prototype
- Conclusions
3The background
4From conferences to cartoons
5Possible Solutions?
- Kyoto Protocol A possible solution to fossil
fuel depletion and global warming is an increased
recourse to Renewable Energy (RE). - Possible application to cars
- Fuels/Energy from RE (Bio-Fuels, H2)
- Solar Cars
6Solar Energy
7Solar Energy vs. Energy Consumption
The solar energy striking the US in one day is
almost equivalent to the energy consumption for
one and a half year
8PV Panels
Today's most common PV devices use a
single-junction with poli-crystalline silicon,
with efficiency of about 12 Use of
mono-crystalline silicon results in higher
efficiency (15 and more)
Multi-junction cell
Much of today's research in multi-junction cells
focuses on gallium arsenide as one of the
component cells. Such cells have reached
efficiencies of around 40 under concentrated
sunlight (Fresnel lens).
9PV efficiency trends
10Solar Panels Production and Prices
The production of photovoltaic panels has
remarkably increased since 90s in terms of
installed power.
Their cost, after a continuous decrease and an
inversion of the trend occurred in 2004, appears
now quite stable
11Outline
- Introduction
- HSV models and results
- Optimization of Management Strategies
- The Prototype
- Conclusions
12Solar Cars
Various propotypes of solar cars have been
developed, for racing and demonstrative use
13Limits of Solar Cars
- Solar Cars do not represent realistic alternative
to normal cars, due to - Limited power and performance.
- Limited range.
- Discontinuous energy source.
- High cost.
14Hybrid Electric Vehicles
F.Porsche, 1900
Buick Skylark, 1974
Toyota Prius
Ford Escape
Honda Insight
GM Precept
Mercedes S400 Hybrid-Diesel
Peugeot 308 Hybrid-Diesel
15HEV and PV a possible marriage?
16About the dowry
17Energy Balance in a Solar Car
Net solar energy available to propulsion KWh/day
esunaverage insolation (KWh/m2day) APVeffective
panel area APV,H0.5 APV,V ?PVpanel efficiency
(0.13) ? reduction factor due to
charge/discharge processes in battery (0.9) ?
insulation reduction during driving, due to
shadow (0.9)
18Solar Fraction
6 m2_at_12 or 3 m2_at_24
Driving hours per day
Solar energy can represent a significant
contribution for intermittent use (h1-2) and for
limited average power.
For average power from 5 to 10 KW and driving
hours from 1 to 2, solar contribution ranges from
18 to 60.
Site San Antonio, Texas Yearly Averaged Data
19Statistics on Car Drivers
Some recent studies of the UK government stated
that
- about 71 of UK users reaches their office by car
- 46 of them have trips shorter than 20 min
- mostly with only one person on board.
Source Labour Force Survey, http//www.statistic
s.gov.uk/CCI/nscl.asp?ID8027
20Power Demand
Extra-urban
Urban
Power demand can be determined integrating the
longitudinal vehicle model over a mission cycle.
During urban drive, limited average power can be
required to drive a small car.
Mass1000 Kg - Length3.75 m
21Effects of Position on Energy
Average Yearly Energy (KWh/year)
Almost a factor 2 between maximum and minimum
latitudes.
For fixed panels, there is not a relevant loss by
adopting horizontal position with respect to
optimal tilt, particularly at low latitudes.
Energy absorbed with vertical position is
significantly lower, mainly at low latitudes.
Latitude (deg)
22Some HSV prototypes
Viking 23 Western Washington University
Tokyo University of Agriculture and Technology
Solar Toyota Prius By Steve Lapp
Ultra-Commuter The University of Queensland
23Solar Prius
Prius with an aftermarket 215 W monocristalline
solar module with peak power tracking and a 95
efficiency DC-DC Converter
It is estimated that the PV Prius will consume
somewhere between 17 and 29 less gasoline than
the stock Prius (range per day 5-8 miles)
24Well to Wheel
25HSV vs HEV
HEV ? Conventional Car Electric Motor
HSV ? HEV PV
26HSV vs HEV
- Mission profile (HSV should be optimized for
urban driving) - Different SOC management strategies.
- Different structure (vehicle dimension, hybrid
architecture)
27HSV vs HEV control
28Potential advantages of Series HSV
- No mechanical link between generator and wheels
- Very effective vibration insulation can be
achieved - Less constraints for vehicle layout
- Possible use of in-wheel motors with advanced
traction control techniques - Engines optimized for steady operation can be
used - ICE designed and optimized for steady conditions
- D.I. Stratified charge engine (4 or 2 strokes)
- Micro gas turbine
- Series architecture acts as a bridge towards the
introduction of fuel cell powertrains. - More suitable for V2G applications
29Vehicle to Grid (V2G)
- V2G concept to connect parked electric driven
vehicles (electric, hybrid, hybrid solar,
fuel-cell) to the grid by a two-way computer
controlled hook up. - The power capacity of the automotive fleet is
about 10 times greater than the electrical
generating plants (in US) and is idle over the
95.
- Advantages
- Reduction of costs for peak power production.
- Toward the distributed generation, with reduction
of Transmission and Distribution (TD) costs. - Facilitate integration of intermittent renewable
resources. - The value of the utility exceeds the costs for
the two-way hook up and for the reduced vehicle
battery life.
30V2G Additional advantages for HSV
31Engine control in a series HSV
In a series HSV, the Internal Combustion Engine
could operate on the optimum efficiency curve and
whenever possible at its maximum efficiency
ICE Efficiency
ICE Power
32SHM Operating Modes /1
Parking
PV Panels
with sunlight
VMU
ICE
EG
EM
Battery
33SHM Operating Modes /2
Hybrid
PV Panels
with sunlight
VMU
ICE
EG
EM
Battery
34SHM Operating Modes /3
Electric Driving
PV Panels
with sunlight
VMU
ICE
EG
EM
Battery
35SHM Operating Modes /4
Regenerative Braking
PV Panels
with sunlight
VMU
ICE
EG
EM
Battery
36SHM Operating Modes /5
Recharge from grid
PV Panels
with sunlight
VMU
ICE
EG
EM
Battery
37SHM Operating Modes /6
We believe that the most plausible vehicle of
the future is a plug-in hybrid... (Center for
Energy and Climate Solutions, 2004)
Power to grid (V2G)
PV Panels
Thermal load
with sunlight
heat
VMU
ICE
EG
EM
Battery
38Flow Chart
DESIGN SPECIFICATION Power demand Insolation
HSV Structure
CONTROL VARIABLES Control Strategy for EG MPPT
for PV
DESIGN VARIABLES PV Panel Area and Position EG
and EM Power Car dimensions Materials
EXHOGENOUS VARIABLES Fuel Price Panel
Efficiency Unit weight and costs
MODELS Energy Flows for HSV/CC Car sizing -
Weight - Cost
OUTPUT Car Stability Fuel Savings Weight -
Payback
Objective Function and Constraints
39Payback Optimization
? Objective Function minimum Payback
? Inequality Constraints
- Design variables X
- Electric Generator Power PEG
- Electric Motor Power PEM
- Horizontal panel area APV,H
- Vertical panel area APV,V
- Car length l
- Car width w
- Car Height h
- Weight reduction factor of car chassis with
respect to base value CWf
Solved by Sequential Quadratic Programming
(Matlab routine FMINCON)
40Constraint Specification
EG Power within lower and upper bounds
41Optimal design results
Fuel Price 2.1 /KG Italy, June, 2008
PV Retail Price June 2008 4.70 /W
42MPPT Techniques
Uniform working conditions
- Due to changing sun irradiance, PV source must be
matched to the load to draw maximum power. - Maximum Power Point Tracking (MPPT) techniques
are adopted. - The presence of local maxima occur during
mismatched conditions, due to shading effects and
temperature variations in different parts of the
panel. - The characteristic may change rapidly during
driving conditions, required advanced MPPT
control.
Mismatched PV field
Power vs. voltage characteristic of a PV field
43Sources of mismatching
- Different solar irradiation levels due to
- Clouds
- Shadows
- Different orientation of parts of the PV field
- Dirtiness
- Tolerances (due to manufacturing and/or ageing)
- Different types of panels (different models,
photo-glass, coloured) in the same string
44MPPT management of PV array
- MPPT strategy are implemented to maximizing PV
efficiency throughout the day.
Max Allowable Power
Power given to the battery
P
Vi
MPPT
Vi
45Outline
- Introduction
- HSV models and results
- Optimization of Management Strategies
- The Prototype
- Conclusions
46HSV Modeling
- Longitudinal model of the HSV protoype
? Power at wheels
? EM Power
? Battery recharge power
experimentally characterized
47Experimental characterization EG and EM
- The electric generator was characterized
connecting a pure resistive electrical load. - A 4 order polynomial regression was obtained.
- EM efficiency is modeled by a 3rd order
polynomial regression identified vs. manufacturer
technical data.
48Experimental characterization the Battery pack
- Battery is modeled applying the Kirchoff law to
an equivalent circuit. - The internal resistance was modeled as a
nonlinear function of state of charge. - Model accuracy was checked against experiments.
49Experimental characterization the PV array
- The PV array has been characterized by connecting
the converter output to a resistive load.
hPV 10 (390 W/m2 irradiation)
- The average PV daily energy was derived from an
experimental year-thorough distribution
50ICE thermal transients
Engine temperature dynamics is estimated by a
first order dynamic model
Steady state temperatures and time constants are
assigned for ICE on and ICE off events
51Thermal effects on power and SFC
Specific Fuel Consumption and power are related
to the ratio between actual temperature and its
steady state value, starting from experimental
data for a SI engine
52Modeling of HC emissions
- Due to the ICE intermittent use, HC emissions
occurring during warm-up have to be accounted
for.
Experimental warm-up HC dynamics
53Energy management strategy
- In case of ICE intermittent use, energy
management for HSV can be addressed via an
optimization analysis.
- The decision variables X include number of ICE
starts, starting time, duration and ICE power
level.
Minimum and maximum values considered for state
of charge
- Day through charge sustaining is achieved
constraining SOC variations.
54Simulation of HSV prototype scenario analysis
- The prototype was simulated on a driving cycle
composed of 4 ECE-like modules.
HSV Specification
55Control optimization results (DBM) 1/3
PEG,N4 gt PEG,N2
- Initially fuel economy increases with engine
starts due to the higher degrees of freedom. - After 4 ICE-on, fuel economy tends to decrease
due to the increasing impact of thermal
transients.
N
56Control optimization results (DBM) 2/3
- HC emissions show an increasing trend with number
of starts. - A local minimum occurs at N 4.
- Such a behavior is due to the different
temperature trajectories.
57Control optimization results (DBM) 3/3
- On average EG operating conditions fall in a high
efficiency region.
- SOC excursions are satisfactorily bounded
- Final SOC leaves room for PV charging during
parking phases
58Energy management optimization by means of
genetic algorithm (GA) search
- As both integer and real variables are involved,
the GA search method was selected for such an
analysis. - HC emissions and fuel consumption for cranking
energy have been also included in the objective
function.
Binary representation of the optimization problem
GA parameters
59Control optimization results (GA) 1/2
60Control optimization results (GA) 2/2
To be recovered in the parking phase
61Comparison between GA and DBM results
A further optimization analysis was run
considering an increase in PV horizontal area
from 1.44 m2 to 3 m2. Such configuration upgrade
results in a fuel consumption reduction from 2.48
kg to 2.28 kg (19.4 saving).
() conventional vehicle fuel consumption 2.83
Kg
62Outline
- Introduction
- HSV models and results
- Optimization of Management Strategies
- The Prototype
- Conclusions
63HSV Prototype
A prototype of hybrid solar vehicle with series
structure has been developed at the University of
Salerno, within the EU Leonardo Program Energy
Conversion Systems and Their Environmental
Impact (www.dimec.unisa.it/leonardo)
64A research and educational project
Leonardo Program (I05/B/P/PP-154181) Energy
Conversion Systems and Their Environmental Impact
http//www.dimec.unisa.it/leonardo
Sponsored by ACS, Salerno (I), Lombardini (I),
Saggese (I).
65The web site www.dimec.unisa.it/Leonardo
A multi-lingual web site has been developed. The
site has more than 1000 visits per week and is at
the top positions on Google.
66Participation to the FIA Alternative Energies Cup
race ECO-TARGA FLORIO (Palermo, Italy)
67Outline
- Introduction
- HSV models and results
- Optimization of Management Strategies
- The Prototype
- Conclusions
68Conclusions
- Hybrid Solar Vehicles can represent a valuable
solution for energy saving and environmental
issues, but accurate re-design and optimization
of both vehicle and powertrain with respect to
HEV are required. - Economic feasibility could be achieved in a near
future, with realistic assumptions for component
costs, fuel price and PV panel efficiency. - Significant fuel savings can be obtained by
proper ICE management strategies. Thermal
transient effects on fuel consumption and HC
emissions must be considered in case of
intermittent use. - The use of optimization techniques (GA, DBM) has
allowed to select the best management strategies,
to be used as benchmark for real-time
implementable control. - Interdisciplinary research is needed, but also a
systematic dissemination of results and
potentialities, in order to remove the obstacles
to the diffusion of such vehicles.
69On-going activities
- Development and implementation of real-time
control strategies and comparison with benchmark
solutions. - On road tests on the prototype to validate both
simulation results and control strategies. - Installation of an automated sun-tracking roof to
further enhance solar energy contribution.
70HSV An artistic point of view
Thank you for your kind attention