Development of hybrid photovoltaic-fuel cell system for stand-alone application

ww.sciencedirect.com

i n t e rn a t i o n a l j o u rn a l o f h y d r o g e n en e r g y x x x ( 2 0 1 3 ) 1e8

Available online at w

journal homepage: www.elsevier .com/locate/he

Development of hybrid photovoltaic-fuel cell system forstand-alone application

Djamila Rekioua*, Samia Bensmail, Nabila Bettar

Department of Electrical Engineering, Laboratory LTII, University of Bejaia, 06000, Algeria

a r t i c l e i n f o

Article history:

Received 27 November 2012

Accepted 7 March 2013

Available online xxx

Keywords:

Fuel cell (FC)

Photovoltaic (PV)

Hybrid power system (HPS)

Fuel cell (FC)

Power management

* Corresponding author.E-mail address: [email protected] (D.

Please cite this article in press as: Rekiapplication, International Journal of Hyd

0360-3199/$ e see front matter Copyright ªhttp://dx.doi.org/10.1016/j.ijhydene.2013.03.0

a b s t r a c t

In this paper we present firstly the different hybrid systems with fuel cell. Then, the study

is given with a hybrid fuel cellephotovoltaic generator. The role of this system is the

production of electricity without interruption in remote areas. It consists generally of a

photovoltaic generator (PV), an alkaline water electrolyzer, a storage gas tank, a proton

exchange membrane fuel cell (PEMFC), and power conditioning units (PCU) to manage the

system operation of the hybrid system. Different topologies are competing for an optimal

design of the hybrid photovoltaiceelectrolyzerefuel cell system. The studied system is

proposed. PV subsystem work as a primary source, converting solar irradiation into elec-

tricity that is given to a DC bus. The second working subsystem is the electrolyzer which

produces hydrogen and oxygen fromwater as a result of an electrochemical process. When

there is an excess of solar generation available, the electrolyzer is turned on to begin

producing hydrogen which is sent to a storage tank. The produced hydrogen is used by the

third working subsystem (the fuel cell stack) which produces electrical energy to supply the

DC bus. The modelisation of the global system is given and the obtained results are pre-

sented and discussed.

Copyright ª 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights

reserved.

1. Introduction converters, filters and a control system for load management.

Hybrid power systems (HPS) combine two or more sources of

renewable energy into one or more conventional energy

sources [1e3]. The renewable energy sources such as photo-

voltaic and wind do not deliver a constant power, but due to

their complementarities their combination provides more

continuous electrical output. Hybrid power systems are

generally independent from large interconnected networks

and are often used in remote areas [4,5]. The purpose of a

hybrid power system is to produce as much energy from

renewable energy sources to ensure the load demand. In

addition to sources of energy, a hybrid system may also

include a DC or AC distribution system, a storage system,

Rekioua).

oua D, et al., Developmrogen Energy (2013), htt

2013, Hydrogen Energy P40

All these components can be connected in different archi-

tectures. The renewable energy sources can be connected to

the DC bus depending on the size of the system. The power

delivered by an HPS can vary from a few watts for domestic

applications up to a few megawatts for systems used in the

electrification of small villages. Thus, the hybrid systems used

for applications with very low power (under 5 kW) generally

feed DC loads. Larger systems, generating a power greater

than 100 kW are connected to an AC bus, and they are

designed to be connected to large interconnected networks [6].

Hybrid systems are characterized by several different sources,

several different loads, several storage elements and several

forms of energy. We present in this paper firstly the different

ent of hybrid photovoltaic-fuel cell system for stand-alonep://dx.doi.org/10.1016/j.ijhydene.2013.03.040

ublications, LLC. Published by Elsevier Ltd. All rights reserved.

mailto:[email protected]

www.sciencedirect.com/science/journal/03603199

www.elsevier.com/locate/he

http://dx.doi.org/10.1016/j.ijhydene.2013.03.040



PV

Fuel cell stack

I

sI

pvI

chI

battI

DC

Bus

DC load

AC load

DC

DC

DC

DC

AC

DC

Battery

Fig. 1 e Description of a hybrid photovoltaicebatteryefuel cell.

i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n en e r g y x x x ( 2 0 1 3 ) 1e82

hybrid systems which include a fuel cell generator. Then, the

studied system is proposed. Finally obtained simulation re-

sults and some experimental ones are presented and

discussed.

2. Different hybrid systems with fuel cell

2.1. Hybrid photovoltaicefuel cell

The role of a hybrid (fuel cellePV) system is the production of

electricity without interruption in remote areas. It consists

generally of a photovoltaic generator (PV), an alkaline water

electrolyzer, a storage gas tank, a proton exchangemembrane

fuel cell (PEMFC), and power conditioning units (PCU) to

manage the system operation of the hybrid system. A PEM fuel

cell can be described as two electrodes (anode and cathode)

separated by a solid membrane. The energy is produced by a

PV generator. Whenever there is enough solar radiation, the

Fig. 2 e Hybrid wind/PV/f

Please cite this article in press as: Rekioua D, et al., Developmapplication, International Journal of Hydrogen Energy (2013), htt

user load can be powered totally by the PV generator. During

periods of low solar radiation, auxiliary electricity is required.

An alkaline high pressure water electrolyzer is powered by the

excess energy from the PV generator to produce hydrogen and

oxygen at a maximum pressure. A PEMFC is used to keep the

system reliability at the same level as for the conventional

system while decreasing the environmental impact of the

whole system. The PEMFC consumes gases which are pro-

duced by an electrolyzer to supply the user load demandwhen

the PV generator energy is deficient; it works as an auxiliary

generator. Power conditioning units dispatch the energy be-

tween the components of the system.

2.2. Hybrid photovoltaicebatteryefuel cell system

In this configuration (Fig. 1), the fuel cell system is used as a

back-up generator, when the batteries reach the minimum

allowable charging level and the load exceeds the power

produced by the PV generator. The advantages of this system

uel cell configuration.




i n t e rn a t i o n a l j o u rn a l o f h y d r o g e n en e r g y x x x ( 2 0 1 3 ) 1e8 3

are in general the same as for a photovoltaicebatteryediesel

hybrid system with regard to the PV generator size and bat-

teries availability. It is noted that fuel cell system needs more

time to provide the rated power and the output should only be

increased slowly after start up. The increasing of the operating

temperature which occurs during operation improves signif-

icantly the efficiency of a fuel cell [7].

2.3. Hybrid photovoltaic/wind/fuel cell system

The necessary changes in our energy supply system can be

accomplished if we use a hybrid system with solar, wind and

fuel cell energies. Generally, the overall system comprises a

wind subsystem with an AC/DC rectifier to connect the wind

generator to the DC bus. It’s also consisted of a PV subsystem

connected to the DC bus via a filter and DC/DC converter. The

excess energy is stored as electrolytic hydrogen through an

electrolyzer and we use a fuel cell to generate electricity

during low irradiance and low wind speed (Fig. 2).

2.4. Hybrid photovoltaiceelectrolyzerefuel cell system

In some applications, another source of energy is necessary to

realize energy storage. In a hybrid photovoltaiceelectrolyzere

fuel cell system, the excess energy is stored in the form of

compressed hydrogen via conversion through the electrolyzer.

The fuel cell is used to produce power if the needed power

exceeds that produced by the PV generator. It can also function

as an emergency generator, if the PV generator system fails [7]

(Fig. 3).

2.5. Different topologies of hybridphotovoltaiceelectrolyzerefuel cell system

Different topologies are competing for an optimal design of

the hybrid photovoltaiceelectrolyszerefuel cell System

Fig. 3 e Description of a hybrid photovo


(Fig. 4). These topologies are DC and AC coupled systems. The

PV generator supplies the electrolyzer with DC voltage. To

obtain correctly the direct coupling of the component, the

maximum power point voltage of the PV generator must be

equal to the maximum voltage of the fuel cell component and

the rated voltage of the electrolyzer component [7]. In this

case, the connection between the components and the user

demand is established through power conditioning unit. It

keeps the DC bus voltage almost constant while the power is

fluctuating. System with AC coupled components is con-

nected directly to the AC bus. The inverters can keep the

output frequency and voltage stable and allow the energy

surplus to flow backwards and to be stored into the hydrogen

subsystem. This configuration has numerous advantages

such as: expandability, utility grid, compatibility, cost reduc-

tion, and simple design and installation [7].

3. Description of the studied system

The proposed and studied system comprises photovoltaic

panels (Siemens SM110-24), a fuel cell stack and a storage

system. Power management unit (PMU) allows the coordina-

tion between the different energy sources such as PV panels

electrolyzes and fuel cells (Fig. 5). Generally, PV subsystem

works as a primary source; it converts solar irradiation into

electricity provided to a DC bus. Hydrogen is used by the

second working subsystem (the fuel cell stack) which pro-

duces electrical energy to supply the DC bus.

3.1. Modeling of the studied system

3.1.1. Modeling of the PVThe model studied in this work is represented by an equiva-

lent circuit. This one consists of a single diode for the cell

polarization function and two resistors (series and shunt) for

ltaiceelectrolyzerefuel cell system.




Fig. 4 e Different topologies of hybrid photovoltaiceelectrolyzerefuel cell system.

Load

(house,..)

Power management unit

Fuel cell stack

StorageO2

H2

Photovoltaic panels

AC

DC

Fig. 5 e Description of the overall system.



the losses (Fig. 6). Thus, it can thus be named “one diode

model”. Thismodel runs under the technical characteristics of

the solar cells given by the manufacturers (data sheets).

The Ipv (Vpv) characteristic of this model is given by the

following equation:

GTj

Iph Ipv

Id IRsh

Rsh

Rs

Vpv

Fig. 6 e Simplified equivalent circuit of solar cell.




Fig. 7 e Comparison of experimental results with simulation ones.

Fig. 8 e Electrical representation of a PEMFC.

Electric circuit

Humid Air Liquid Water Hydrogen

Input air

Moto-compressor

Ele

Fan

pump

Output air

Ta

To electric

circuit

To electric circuit

Fig. 9 e Diagram



Ipv ¼ Iph � Id � IRsh (1)

or, developing the terms Id and IRsh:

Ipv ¼ Iph � I0

�exp

�q�Vpv þ Rs$Ipv

�ANsKTj

�� 1

�� Vpv þ Rs$Ipv

Rsh(2)

There are different methods to solve Eq. (2), each method

leads to an approximate mathematical models. The different

mathematical models generally include parameters that are

provided by photovoltaic modules manufacturers. For this,

several methods have been proposed in the literature to

determine different parameters. The module is made of 72

solar cells connected in series to deliver a maximum power

output of 110 W. The variation in both the Ipv � Vpv and

Ppv � Vpv characteristics with irradiance level are simulated

cath

ode

Ano

de

ctric circuit

Hydrogen

nk

Out of hydrogen

of a PEMFC.




3 Ipemfc

2

Vbus

1

Ibus1

Vpemf c

Ibus

iL

Vbus

v busibus

1Vpemfc

Fig. 10 e Bloc diagram.


and the results are plotted in Fig. 7 with the experimental

results.

3.1.2. Modeling of fuel cell PEMFCIt is necessary to define the different circuits of a fuel cell

system to simplify the modeling and control of each circuit

Fig. 11 e Power


(Fig. 10). The cell system is composed of the heart cell asso-

ciated with all necessary ancillaries to the operation of a fuel

cell in an embedded application. Fig. 9 shows all functions

that are present in a fuel cell system [8]. TheMoto-compressor

is composed of an air compressor and an electrical machine.

Generally it is a permanent magnet synchronous motor

(PMSM). An air compressor supplies directly each stack, and

the flowof the air is regulated through the control of rotational

speed. The compressors used in such applications are volu-

metric type because they can easily control the outflow. These

types of compressors are classified into two categories:

reciprocating compressors and rotary compressors. In fuel cell

applications, it is the twin-screw rotary compressor types

which are used because they do not require lubrication. The

inputs of the compressor model are the rotation speed u and

the discharge pressure Ps (imposed by the pressure control).

The outputs are the mass flow and torque compression.

Another useful parameter for the operation of the stack is the

gas temperature at the output of the compressor (Fig. 9).

The simulated cell voltage VPEMFC is lower than the theo-

retically voltage ENerst. This is due to various irreversible loss

mechanisms. These losses,which are often called polarization

or over-voltage losses, originate primarily from three sources:

activation over-voltage Uact, concentration or diffusion over-

voltage Uconc, resistive or ohmic over-voltage Uohm [7](Fig. 8).

VPEMFC ¼ ENernst þ Uact � Uohm � Uconc (3)

waveforms.




Fig. 12 e Hybrid power in a case of a sudden irradiation.

Fig. 13 e Hybrid power in a case of a profile irradiation in a summer day.


Uohm ¼ IpacScell

0BB@181:6

�1þ 0:03

�IPEMFC

Scell

�þ 0:06

�T

303

�2�IPEMFC

Scell

�2:5��l� 0:634� 3

�IPEMFC

Scell

��exp

�4:18

�T� 303

T

��

� �IPEMFC þ Scell � Rc

1CCA

(4)

Uact ¼ b1 þ b2 � TPEMFC þ b3 � TPEMFC � ln�j � 5 � 10�3�

þ b4 � TPEMFC � lnC�O2

(5)

Uconc ¼ �Bln

�1� j

jmax

�(6)

The expression of the Nernst equation according to JC

Amphlett is given by:

ENernst ¼a1 þ a2 � ðTPEMFC � 298:15Þ þ a3 � TPEMFC

��0:5 � lnP�

O2þ lnP�

H2

(7)

3.1.3. Power managementA control strategy for power management is needed [9e11].

The total power is calculated as [12]:


Ptotal ¼ Ppv � Pcomp � Pload (8)

Any excess of PV power is supplied to the electrolyzer to

generate hydrogen that is delivered to the hydrogen storage

tanks through a gas compressor. The power balance equation

given by: (Ptotal > 0)

Ppv ¼ Pcomp þ Pload þ Pelectrolyser (9)

If there is a deficit in total power (Ptotal < 0), the PEMFC start

producing energy for the load using hydrogen from the stor-

age tanks. Thus, in this case the power balance equation can

be written as: Figs. 11e13

Ppv þ PPEMFC ¼ Pload (10)

We Note that between 10:30 and 14:00, the PV generator

works and provides the power required. This is due to the light

curve, the rest of the day, the PEMFC delivers this power. We

can note from the obtained results that the proposed hybrid

system works as proposed by the power management.

4. Conclusion

In this paper, the model of a hybrid fuel cellephotovoltaic

generator is presented. The different parts of the proposed





system have been firstly modeled separately and then the

Power Management Unit (PMU) allows the coordination be-

tween PV panels and fuel cells. We can conclude that the PMU

unit can vary the number of photovoltaic panels assigned to

feed the other parts of the system. Thus it will be necessary to

develop a data acquisition system and implement automatic

controls for power management. The simulation model of the

hybrid system has been developed using MATLAB/Simulink.

The obtained results are presented and show the feasibility of

a solar-hydrogen energy production in a stand-alone system

as telecom application.

r e f e r e n c e s

[1] Mcgowan JG, Manwell JF. Hybrid/PV/diesel systemexperiences. Revue Renewable Energy 1999;16:928e33.

[2] Belhamel M, Moussa S, Kaabeche A. Production of electricityof a hybrid system (WindePhotovoltaiceDiesel). Review ofRenewable Energy 2002:49e54.

[3] El Khadimi A, Bachir L, Zeroual A. Sizing optimization andtechno-economic energy system hybrid photovoltaic e windwith storage system. Renewable Energy Journal2004;7:73e83.

[4] Saheb-Koussa D, Koussa M, Belhamel M, Haddadi M.Economic and environmental analysis for grid-connectedhybrid photovoltaicewind power system in the arid region.Energy Procedia 2011;6:361e70.


[5] Kaldellisa JK, Kavadiasa KA, Koronakis PS. Comparingwind and photovoltaic stand-alone power systemsused for the electrification of remote consumers.Renewable and Sustainable Energy Reviews2007;11:57e77.

[6] Vechiu I. Modelling and analysis of integration of renewableenergy in an autonomous network. PhD thesis. France:University of Havre; 2005.

[7] El-Maaty Abou, Metwally Aly Metwally, El-Aal Abd.Modelling and simulation of a photovoltaic fuel cell hybridsystem. A dissertation for the degree of Doctor inEngineering (Dr.-Ing.). Faculty of Electrical Engineering,University of Kassel; April 15 2005.

[8] Bettar N. Study and modeling of a PEM fuel cell. Master’sthesis. Algeria: University of Bejaia; 2008.

[9] Chekired F, Mahrane A, Chikh M, Smara Z. Optimization ofenergy management of a photovoltaic system by the fuzzylogic technique. Energy Procedia 2011;6:513e21.

[10] Rekioua D, Matagne E. Optimization of photovoltaic powersystems: modelization, simulation and control. EditionSpringer, ISBN 978-1-4471-2403-0; 2012.

[11] Ipsakis D, Voutetakis S, Seferlis P, Stergiopoulos F,Elmasides C. Power management strategies for a stand-alonepower system using renewable energy sources and hydrogenstorage. International Journal of Hydrogen Energy August2009;34(16):7081e95.

[12] Zhou Keliang, Ferreira JA, de Haan SWH. Optimal energymanagement strategy and system sizing method forstand-alone photovoltaic-hydrogen systems.International Journal of Hydrogen Energy January2008;33(2):477e89.




Documents

Development of hybrid photovoltaic-fuel cell system for stand-alone application