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TRAINING FOR OLADE`S MEMBER COUNTRIES
COURSE CAPEV 14 2011
DESIGN AND IMPLEMENTATION OF COMBINED HYBRID
SYSTEMS
(ADVANCES IN TECHNOLOGY AND REGULATION)
By César Angeles-Camacho
Instituto de Ingenieria, UNAM
[email protected]
Octubre 2011
Lecturer: PhD. César Angeles-Camacho
Contact Details:
Instituto de Ingeniería, Edificio Bernardo Quintana
(12), Room 202 (Cord. De Eléctrica y Computación)
Telephone: 56-23-36-00 ext. 8810
Email: [email protected]
Areas of Expertise/Research
Modelling and Simulation of Large-scale Power Systems with FACTS
Equipment
Power Electronic Equipment Principles and its Applications in Electric
Power Systems, Generation, Transmission and Distribution
Wind Generation – Impact on the Power Networks, Transmission and
Distribution System
Session 4
Chapter 5: Wind – PV- Diesel hybrid
systems
Contact Details: PhD. César Angeles Camacho
Instituto de Ingeniería, Edificio Bernardo Quintana
(12), Room 202 (Cord. De Eléctrica y Computación)
Telephone: 56-23-36-00 ext. 8810
Email: [email protected]
Wind-PV hybrid systems
with diesel generator backup.
a. Introduction.
b. Design and configuration of a Wind-PV – Diesel system.
c. Sizing.
d. Optimization of Wind-PV-Diesel system.
e. Environmental impact of Wind-PV-Diesel system.
Introduction
Wind and Solar are naturally complementary in terms of both resources
being well suited to hybrid systems.
The rapid growth of the solar photovoltaics (PV) industry has contributed to
the demand for small wind turbines, as the two technologies are often
market complements.
Hybrid electric systems combine wind and PV systems to make the most of
the area's seasonal wind and solar resources;
 with wind relatively more available in winter months and at night
time,
 and solar relatively more available in summer months and during
winter's sunlit days.
Introduction
Introduction
These hybrid systems provide a
more consistent year-round
output than either wind-only or
PV-only systems and can be
designed to achieve desired
attributes at the lowest
possible cost.
These systems can be grid
connected, but they are also
often stand-alone, distributed
energy generators.
Introduction
A drawback, common to solar and wind power generations, is their
unpredictable nature and dependence on weather and climatic changes.
Both of these would have to be oversized to make their stand alone systems
completely reliable.
For the times when neither system is producing enough electric
power, most hybrid systems have backup power through batteries
and/or an engine generator powered by conventional fuels, such as
diesel.
Introduction
Therefore, depending on the requirement and the availability of energy
sources, more than two sources maybe combined, such as solar-wind-Diesel
system.
This kind of hybrid system can attenuate individual fluctuations,
increase overall energy output and reduce energy storage
requirements significantly.
Introduction
Various hybrid energy systems have been installed in many countries over
the last decade, resulting in the development of systems that can compete
with conventional, fuel based remote area power supplies in many
applications.
With the wide spread introduction of net-metering, the use of small isolated
or grid connected hybrid energy systems is expected to grow tremendously
in the near future, both in industrialized and developing countries.
Introduction
However, with the increased complexity, the optimum design of hybrid
system becomes complicated through
 uncertain renewable energy supplies
 Uncertain load demand,
 non-linear characteristics of the components,
 and the fact that optimum configuration and optimum control
strategy of the system are interdependent.
Design and configuration of a wind-PV system
Typical stand-alone hybrid solar-wind-diesel power generation system
consists of three types of power generation facilities:
i.
PV array,
ii.
wind turbine,
iii.
diesel generator,
And other componets like,
 inverter, rectifier,
 Battery bank. serve for the storage of the natural energies
 controller,
 and other accessory devices and cables.
Design and configuration of a wind-PV system
In stan-along systems the storage Batteries are installed to ease the
fluctuations of power generation output normally happened in case of
renewable energy source.
Design and configuration of a wind-PV system
Various combinations of diesel generator, wind turbine, PV array, battery, and power
converter modules can be taken into account towards identifying an economically
viable solution that would meet the required load.
For commissioning a hybrid system it is initially assume that the site selected is
exposed to reasonable wind speeds as well as good solar irradiation.
It is also essential to know the energy demand at that site.
This allowed for the design of a suitable hybrid power system that would meet the
demands of load at best.
Design and configuration of a wind-PV system
Climatic conditions determine the availability and magnitude of wind and solar
energy at particular site.
Pre-feasibility studies are based on weather data (wind speed, solar insolation) and
load requirements for specific site.
In order to calculate the performance of an existing system, or to predict energy
consumption or energy generated from a system in the design stage, appropriate
weather data is required
Feasibility of hybrid PV/wind energy system strongly depends
on solar radiation and wind energy potential available at the
site
Design and configuration of a wind-PV system
The collected data of the various energy sources is analysed in order to plan for the
structure of the system
Various feasibility and performance studies are reported to evaluate option of hybrid
PV/wind energy systems
Simulations and modelling were carried out over a period of time, allowing the
statistical information about local weather to be truly representative.
Photovoltaic array area, number of wind machines, and battery
storage capacity play an important role in operation of hybrid
PV/wind–diesel system while satisfying load
Design and configuration of a wind-PV system
The recent state of art hybrid energy system technological development is the result
of activities in a number of research areas, such as
 Advances in electrical power conversion through the availability of new
power electronic semiconductor devices, have led to improved efficiency,
system quality and reliability.
 Development of versatile hybrid energy system simulation software;
continuing advances in the manufacturing process and improve efficiency of
photovoltaic modules.
Design and configuration of a wind-PV system
 The development of customized, automatic controllers, which improve the
operation of hybrid energy systems and reduce maintenance requirements.
 Development of improved, deep-cycle, lead-acid batteries for renewable
energy systems.
 Availability of more efficient and reliable AC and DC appliances, which can
recover their additional cost over their extended operating lifetime.
The task for the hybrid energy system controller is to control the
interaction of various system components and control power flow
within the system to provide a stable and reliable source of energy.
Sizing
After pre-feasibility study the selection of proper sizing of equipment is made based
on weather data and maximum capacity.
The unit sizing of integrated power system plays an important role in deciding the
reliability and economy of the system.
Open literature show wide Studies by the different researchers discussing different
methods to determining the wind generator capacity and the number of PV panels,
number and size of wind turbines and number and capacity of battery needed for
the stand-alone system.
Sizing
Some methods to determinate the size of the Wind-PV-Diesel Systems are,
 linear programming techniques to minimize the average production cost of
electricity while meeting the load requirements in a reliable manner, and takes
environmental factors into consideration both in the design and operation phases
are used.
 Using the measured data of solar and wind energy at a given location, research's
employ a simple graphical construction to determine the optimum configuration
of the two generators that satisfies the energy demand of the user throughout the
year.
 Presented some methodologies for optimal sizing of stand-alone WG-P-Diesel
systems are using genetic algorithms.
Sizing
Optimum size of hybrid PV/wind energy system can be calculated on an hourly basis
or on the basis of daily average power per month, the day of minimum PV power per
month, and the day of minimum wind power per month.
National Renewable Energy Laboratory (NREL)’s, Hybrid Optimization Model for
Electric Renewable (HOMER , www.homerenergy.com) has been used as the sizing
and optimization software tool.
HOMER contains a number of energy component models and evaluates suitable
technology options based on cost and availability of resources.
Sizing
Analysis with HOMER requires information on
a) resources,
b) economic constraints,
c) and control methods.
It also requires inputs on
 component types,
 their numbers,
 costs, efficiency,
 longevity,
 etc.
Sizing
HOMER's optimization and sensitivity analysis algorithms allow the user to evaluate
the economic and technical feasibility of a large number of technology options and to
account for uncertainty in
 technology costs,
 energy resource availability,
 and other variables
HOMER Optimization and Sensitivity analysis could be done with variables having a
range of values instead of a specific number.
Considering the combine resources W-PV-Diesel, it is important that
an optimum solution is found based on the local needs and resources
available.
Optimization of Wind-PV-Diesel system
In order to predict the hybrid system performance, individual components need to be
modelled first and then their mix can be evaluated to meet the load demand.
PV module modelling
In order to predict the hybrid system performance, individual components need to be
modelled first and then their mix can be evaluated to meet the load demand.
The solar array or panel is
defined as a group of several
modules
electrically
connected in series-parallel
combinations to generate the
required current and voltage.
Optimization of Wind-PV-Diesel system
Equivalent Electrical Circuit
The complex physics of the PV cell can be represented by the equivalent electrical
circuit shown
The ideal equivalent circuit of a solar cell consists of a current source in parallel with
a diode.
The output terminals of the circuit
are connected to the load.
Internal resistance
Iph is equal to the light-generated current Ii
less the diode-current ID and the shuntleakage current Ip
Rp is inversely related with leakage current
to the ground
Optimization of Wind-PV-Diesel system
Equivalent Electrical Circuit
The open circuit voltage Voc of the
cell is obtained when the load
current is zero,
The load current is therefore
given by the expression:
where
ID = the saturation current of the diode
Q = electron charge = 1.6 · 10 –19 Coulombs
A = curve fitting constant
K = Boltzmann constant = 1.38 · 10–23
Joule/°K
T = temperature on absolute scale °K
Optimization of Wind-PV-Diesel system
PV module can be seen as a black box that with two connectors,
producing a current, I, at a voltage, V.
If the array is operating at voltage V and current I, the power generation is
P = V · I watts.
The power–voltage (P–
V) characteristic of a
photovoltaic module
operating at a standard
irradiance of 1000 W/m
and temperature of 25
°C is show
Optimization of Wind-PV-Diesel system
A simplified simulation PV model is used to estimate the actual performance of PV
modules under varying operating conditions.
Optimization of Wind-PV-Diesel system
PV modules represent the fundamental power conversion unit of a PV system, but a
single PV module has limited potential to provide power at high voltage or high
current levels.
It’s then mandatory to connect PV modules in series and in parallel in order to scaleup the voltage and current to tailor the PV array output. If a matrix of Ns×Np PV
modules is considered, the maximum power output of the PV system can be
calculated by:
Optimization of Wind-PV-Diesel system
Modelling of Wind turbine
A complex mathematical modelling of wind energy conversion system includes, wind
turbine dynamics and generator modelling.
However a simplex model can be used.
Wind Turbine Performance Model: The wind turbine power output can be simulated
by:
Optimization of Wind-PV-Diesel system
Modelling of diesel generator
To attenuate shortfalls in energy production during periods of poor sunshine, and
poor wind speed a backup diesel generator is used for increased system availability
and minimum storage requirements.
The choice of diesel generator depends on type and nature of the load.
Optimization of Wind-PV-Diesel system
Modelling of diesel generator
To determine rated capacity of the engine generator to be installed, following two
cases should be considered:
1. If the diesel generator is directly connected to load, then the rated capacity
of the generator must be at least equal to the maximum load,
2. If the diesel generator is used as a battery charger, then the current
produced by the generator should not be greater than CAh/5 A, (CAh is the
ampere hour capacity of the battery).
Optimization of Wind-PV-Diesel system
Modelling of diesel generator
Overall efficiency of diesel generator is given by
ŋhover-all = ŋbreakthermal X ŋgenerator
Here ŋbreakthermal is brake thermal efficiency of diesel-engine
For the studied system, the diesel generator is started at times when
the battery SOC falls below a certain level (diesel generator starting
point), and then the diesel generator runs at full power (or at a rate not
exceeding the maximum current that batteries are capable of
absorbing) to charge the batteries with any surplus power until the
battery SOC reach the diesel generator stopping point.
Optimization of Wind-PV-Diesel system
Modelling of Batteries bank
Battery Performance Model: Most battery models focus on three different
characteristics.
i.
The first and most commonly used model mainly focuses on the battery
state of charge (SOC).
ii.
The second type of model is the voltage model, which is employed to model
the terminal voltage.
iii. The third type of model is the lifetime model used for assessing the
expected lifetime of the battery.
Optimization of Wind-PV-Diesel system
Minimization of the objective function
(ACS) can be realized using different
optimization techniques.
The flow chart of the optimization
process to obtain the optimum
configuration and control strategies,
implemented employing Genetic
Algorithm (GA), is illustrated in Figure
Optimization of Wind-PV-Diesel system
Based on Genetic Algorithm (GA), which has the ability to attain the global optimum
with relative computational simplicity,
GA as a sizing method for hybrid WG-PV-DG system can be used to calculate the
system optimum configuration that satisfies the load demand with minimum
annualized cost of system.
Minimization of the system cost is achieved not only by selecting an appropriate
system configuration, but also by finding a suitable control strategy.
The decision variables included in the optimization process are the PV module
number, PV module slope angle, wind turbine number, wind turbine installation
height, battery number, diesel generator (DG) type, DG starting and stopping points.
Environmental impacts
Environmental evaluation of the Diesel generator only
Petroleum-based products are one of the main causes of anthropogenic carbon
dioxide(CO2) emissions to the atmosphere.
Indeed the combustion of each litter of diesel produced 2.7 kg of CO2.
For example, during the life cycle of a conventional Diesel Generator used in medium
size WG-PV-Diesel system, the diesel oil which will be consumed is 1,244,286.28 l
leading to about 3360 tonnes of CO2 released in the nature.
Environmental impacts
Environmental evaluation of PV generator only
The mayor drawback with this scenario is there cycling of batteries at the end of their
life time.
In fact, there is no policy concerning recycling of batteries in some countries or
regions and this particular aspect represents a considerable environmental concern.
In the case studied, over the life time of the system, for a total capacity of 41,037.5
Ah, it is 411 batteries of 100 Ah (12 V) which will be probably thrown in the nature.
Environmental impacts
From environmental point of view, from the present hybrid system, Diesel Generator
is the only released in the nature of CO2 gases during its operation, whereas the
hybrid system enabled to save CO2 emission compared to the sue of Diesel Generator
only.
It is also important to noted that in some countries batteries will be thrown in the
nature against zero battery released when considering the diesel generator only
system scenario.
Further more, if the diesel generator is fuelled by biofuels more tonnes of CO2
emission which will be saved.
Indeed, the use of pure biodiesel lowers the emission of CO2 by 80%.
Environmental impacts
The potential emission reduction could also be
used to generate income through carbon
trading.
In order for any remote area energy system to
be sustainable, it is imperative that there are
locally trained technicians available.
Moreover, the consumers must be able to pay a
regular user fee to pay for any maintenance
required and procures spare parts.
Environmental impacts
We can conclude that from economic and environmental point of view, the hybrid
system Wind/PV/diesel presents many benefits compared to the Diesel Generation
only and the Wind or PV generator only.
However, this hybrid system design and management must be improved to bring the
energy more and more cheaper for remote areas.
Recommended reading : Ngan MS, Tan CW. Assessment of economic viability
for PV/wind/diesel hybrid energy system in southern Peninsular Malaysia.
Renew Sustain Energy Rev (2011), doi:10.1016/j.rser.2011.08.028
Questions ?
PhD César Angeles-Camacho, MIET & MIEEE
Universidad Nacional Autónoma de México
Instituto de Ingeniería
Edif. Bernardo Quintana
Circuito Exterior, Ciudad Universitaria
CP 04510, México, D.F.
Tel. +52 (55) 5623-3600 Ext. 8810
email: [email protected]