Potentialities of hydrogen production in Algeria

international journal of hydrogen energy 33 (2008) 4476–4487

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Potentialities of hydrogen production in Algeria R. Boudriesa,b,*, R. Dizeneb a

CDER, Route de l’Observatoire, Bouzareah Algiers, Algeria USTHB, El Alia, Algiers, Algeria

b

article info

abstract

Article history:

The objective of the present study is to estimate the potentialities of hydrogen production

Received 22 December 2007

in Algeria. Particular attention is paid to the clean and sustainable hydrogen production,

Received in revised form

i.e., production from renewable energy.

3 June 2008

First, the present overall energy situation in Algeria is reviewed. Trend in energy demand is

Accepted 4 June 2008

analysed taking into account major parameters such as population growth, urbanization,

Available online 19 August 2008

improvement in quality of life and export opportunities. The resources available for hydrogen production are then presented. Finally, the estimation of hydrogen production

Keywords:

potential using solar sources, the most important renewable energy sources in Algeria, is

Algeria

presented.

Population

This study indicates that the shift to hydrogen economy shows a promising prospect. Not

Hydrogen production

only, it can meet the evergrowing local needs but it will also allow Algeria to keep its share

Primary energy consumption

of the energy market. Indeed, as is now the case for natural gas, hydrogen could be deliv-

Electricity consumption

ered to Western Europe through pipelines.

Hydrocarbons

ª 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights

Renewable energy

reserved.

Water PV Electrolysis Tracking East/West Tracking North/South Fixed PV array

1.

Introduction

Energy has been the driving force behind the economic and social development in the history of mankind. With the advent of the industrial revolution and the technological advances, the energy demand has worldwide increased exponentially. With the improvement in the standard of living, the consumption has gone beyond basic needs [1]. Now energy occupies a sensitive position in all human activities. It has

become important to the point that the degree of a country development is measured by its energy consumption level. Energy sources have evolved and each new source of energy has given new impetus to technological, economic and social changes. At present, hydrocarbons are the dominant energy source. They cover about 80% of the world’s needs [2]. However, the evergrowing demand is putting stress on the hydrocarbon reserves. It has been reported that the energy

* Corresponding author. CDER, Route de l’Observatoire, Bouzareah Algiers, Algeria. Tel.: þ213 550075543. E-mail address: [email protected] (R. Boudries). 0360-3199/$ – see front matter ª 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2008.06.050

international journal of hydrogen energy 33 (2008) 4476–4487

needs are growing at the rate of 1% per year for the industrialised nations and 5% per year for the developing countries [3]. At this rate of consumption and with hydrocarbons production peaking soon [4], the risks of shortage might become a reality in a few decades. On top of this problem of reserves, there is a real concern about the environmental impacts associated with the exploitation, the production, the transport and the use of hydrocarbons. These energy resources are the main source of air pollution, producing environmental damaging pollutants, such as CO2 [5]. It has been reported [6] that CO2 concentration has increased by 30% since the industrial revolution. Although the CO2 emission rate from hydrocarbons’ consumption went noticeably down in the early 1990s, it has been rising again reaching an alarming level in the last five years. This is despite the Kyoto protocol and the local and regional stringent environmental regulations in effect that limit its emission into the atmosphere. CO2 emissions went from 5.84 GtC in 1990 to 6.35 GtC in 1999, to 7.68 GtC in 2005 [7]; representing an average increase rate of 0.24 GtC/year for the 2000–2005 period and 0.087 GtC/year for the 1990–1999 period. Hydrocarbons are then polluting and their use generates greenhouse gases. Even efficiency use has arguably not curbed the explosion in energy consumption or reduced the negative environmental impacts [8,9]. Growing concern over diminishing reserves of fossil fuels and fear of the environmental consequences have led to the active search for new energy sources. Serious reserves have been expressed concerning the use of nuclear power as a worldwide energy source. This is mainly due to the problem of radioactive wastes. The remaining contenders are renewable energy sources. These sources are clean and inexhaustible. They meet worldwide about 13.5% of the global energy demand [10] and they are in full expansion. However, they suffer from intrinsic drawbacks. They are indeed dilute, intermittent and dependent on the season. There is also a mismatch between energy supply and demand. To overcome this hurdle, there is thus the need for its storage in an energy form that can attain high density and that can be stored for long periods and transported possibly over long distances. Among the storage options, hydrogen is gaining increasing consideration as a central player in the world’s energy future [10,11], first by being an alternative to fossil fuels then by ultimately replacing it. Hydrogen, as an energy carrier, has the potential to solve many of the major problems encountered in the use of fossil fuel. It is an environment friendly carrier that can be used in mobile and stationary applications. There is a worldwide growing commitment to hydrogen economy. Some countries, such as Canada, Japan, the United States and the European Union, have ongoing major programs to develop and to implement hydrogen energy systems [11– 15]. Scenarios for the integration of hydrogen as an energy vector into the global energy system have been proposed at the international [16] regional [17] and national levels [18–32]. Even companies, whose main activities are in oil and gas, are more and more seduced by hydrogen as an energy vector [33]. Major oil companies such as Shell and BP have formed subsidiaries whose main activities are the development and

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deployment of hydrogen energy technologies [34]. To this end, they have most often joined forces with car manufacturers, governmental agencies and others to promote and operate hydrogen energy systems. This is the case of California Fuel Cell Partnership where BP, Shell, ExxonMobil and ChevronTexaco are involved [35]. They are also active in decarbonising conventional energy [36] and in setting up hydrogen refuelling stations [37]. For Algeria, hydrogen is of paramount importance. It permits the country not only to increase and to diversify its energy mix but also to keep its share of the energy market at the international level and to meet its domestic demand that is becoming more and more important. Algeria is a country rich in natural resources offering a variety of options for hydrogen production. It exhibits more particularly enormous energy potentialities in solar energy as well as in geothermal and wind energy. The insulation through the whole country is one of the highest in the world in power as well as in number of days. This situation makes Algeria an excellent place for the production of hydrogen using the solar energy. This work presents the current energy situation in Algeria in terms of its total energy resources and consumption. Incidences of population growth and urbanization on the energy scene have been studied. The natural resources available for the production of hydrogen are reviewed and finally the potential of hydrogen production using electrolysis PV system, which represents one of the most technologically advanced sustainable methods, is evaluated.

2.

Algeria and its energy situation

Bordering the Mediterranean Sea, Algeria lies in north-west Africa between the Sahel countries in the south, Western Sahara and Morocco in the west and Tunisia and Libya in the east. It is located between the 18 and 38 of North latitude and between meridians 9 of West longitude and 12 of East longitude. It covers an area of 2,381,741 km2. Its coastal line on the Mediterranean Sea extends over 1200 km and the aerial space stretches out southward on 1800 km as far as the tropic of cancer. Going from north to south, the country presents significant variations in its topographic, climatic and socio-economic characteristics. As shown in Fig. 1, Algeria has a strongly growing population. In the last 25 years it has almost doubled. Though we notice a slowing down in the 1990s, the last statistics (sizable increase in marriage rate and in fertility rate [38]) indicate that it is a short term phenomenon and the population growth is taking a turn towards fast growth. Analysis of the population distribution brings out the following characteristics:  The population is very young: more than 50% of the population is less than 19 years old.  The population is not well distributed: from a point of view of land occupation, there is a disparity in population settlement. The north that represents about 4% of the country area and where most of the energy infrastructures are

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Primary energy consumption (1012 Wh)

international journal of hydrogen energy 33 (2008) 4476–4487

Population ( in 106 inhabitants)

34 32 30 28 26 24 22 20 18 1980

1984

1988

1992

1996

2000

2004

400

a

350

300

250

200 1980 1983 1986 1989 1992 1995 1998 2001 2004

2008

Year

Fig. 1 – Evolution of the Algerian population over the years.

Electricity consumption (billion kWh)

year 25

b

20

located is occupied by 65% of the population; 25% of the population has settled in the high Plateaux region. While only 10% of the population lives in the Sahara desert that represents 87% of the territory and where most of the energy sources are located.  A strong urbanization: urbanization went from 16% in 1966 to way above 63% presently.  A fast growing mega poles: these poles are concentrated mainly in the north. This situation creates the problem of commuting to and from work.  In the south, urban centers, located in scattered oases, are characterized by their remoteness. This situation makes the connection of these centers to the national electrical grid very challenging and very costly.

Fig. 2 – (a) Evolution of the primary energy consumption in Algeria over the years. (b) Evolution of the electricity consumption in Algeria over the years.

We can conclude that Algeria is characterized by a young and growing population, and a fast urbanization. This situation puts certainly a lot of pressure on the energy supply as the demand is going to increase very fast. Fig. 2a represents the evolution of the primary energy consumption. It can be seen that there is a steady increase in consumption up to the 1990s. Then a slight decrease takes place due to the economical and the social instability. But this situation is reversed by the end of the 1990s. In 2005, Algeria primary energy consumption per capita was 12.84 MWh [7]. This represents a healthy increase of about 10% over the previous year indicating a return to economical and social stability. Nonetheless, if this value is almost three times that of the average African consumption, it remains a very modest figure by comparison to the world level (21.05 MWh). This is an indication that growth in energy consumption is very likely and energy demand is definitely going to increase. Algeria current exploited energy resources are hydrocarbons, hydropower and to some extent coal. Renewable energy, the other important energy resource, is not exploited commercially; its exploitation is still at the rudimentary level in the rural areas. Hydrocarbon forms the bulk of the energy supply accounting, in 2005, for more than 97% of the energy mix (oil 33% and gas 64%). Coal and hydropower represent

only modest contributions of 2.7% and 0.3%, respectively [7,39]. The evolution of electricity consumption is shown in Fig. 2b. One can see an increase of more than fourfold in the consumption in the last 25 years despite a slowdown in the 1990s. This situation is also due mainly to the economical restructuring and the decline in the industrial production. The household consumption was large enough to prevent a decrease in the overall electricity consumption. Driven by improvement in quality of life, the number of energy customers as well as the consumption per customer have been increasing steadily [40]. The largest sources of Algeria electricity generation are accounted for by conventional thermal facilities fuelled mainly by natural gas. Hydroelectricity is making a modest contribution (4.5% of the installed capacity in 2005 [40]) that is relatively decreasing over the years due mainly to the limited hydraulic resources. From Fig. 2a and b, it can be seen that energy consumption is growing at a quick rate and the country will be in need of significant additional capacity in the near future. The additional capacity is necessary to meet the soaring internal demand and to fulfil the country ambition to export

15

10

5 1980

1985

1990

1995

2000

2005

Year

international journal of hydrogen energy 33 (2008) 4476–4487

electricity. The internal demand is driven from on one hand by the booming young population, the improvement in quality of life and the fast urbanization and on the other hand by the energy needs for the large scale desalination plants that are planned for the upcoming years. Of particular challenge is also the problem of meeting the needs of the remote and isolated regions that are situated particularly in the south. These regions are not yet connected to the electrical grid. Algeria is also determined to export electricity to Europe. Running along the pipelines, undersea power connections to Europe are under consideration [41]. Algeria is then in need of a big additional capacity. For this reason, there is a risk that conventional energy sources would not anymore be sufficient to meet the high demand. Hydrogen is then an attractive alternative energy carrier. It offers the storability and transportability qualities of conventional resources and the renewability and environmental friendliness of renewable energy. More specifically it allows the country:  to meet its commitment to the Kyoto protocol. Indeed, mitigation of CO2 is possible through sequestration of CO2 in the case of hydrogen production from conventional energy sources. In the case of hydrogen production from renewable energy, there is practically elimination of CO2;  to diversify its energy mix and eventually to have a substitute to the limited hydrocarbon resources;  to exploit in a viable way the very important renewable energy sources. Hydrogen could act as a storage medium for renewable energy. Intermittency and dilution, the two major hurdles could then be overcome this way;  to reduce energy losses particularly in the case of exportation. Indeed, hydrogen could be transported over long distances with fewer losses than electricity [42].

3.

Hydrogen and natural resources

A common element on earth, hydrogen is though found practically in combined form with oxygen in water and with carbon and other elements in hydrocarbon compounds. Several techniques are available for the production of hydrogen. They differ according to the feedstock used (natural gas, methanol, oil, biomass, water, etc.), the process involved (decomposition, steam reforming, partial oxidation, electrolysis, etc.) and the primary energy sources selected (conventional, nuclear or renewable). Some of these techniques have reached commercial production maturity; others are still at the experimental level [43]. Currently, hydrogen is produced overwhelmingly through steam reforming of natural gas (mainly methane) and other hydrocarbons (oil and coal). This technique of hydrogen production with sequestration of generated CO2 has attracted a lot of attention [44,45]. Indeed, conversion of hydrocarbons into a clean fuel such as hydrogen and the capture and the sequestration of the generated carbon is part of the strategy that has been considered for the mitigation of the emission of carbon into the atmosphere and for the smooth move towards the hydrogen economy [46–48].

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Options for the capture and secure storage of carbon have been proposed [49,50]. The best contenders for carbon storage are deep oceans, underground geological formations such as coal seams, depleted oil and gas reservoirs and aquifers. Besides these sequestration options and the terrestrial sequestration option, others are under considerations. This includes the conversion of CO2 into benign materials that has no effect on the environment [51]. However, concerns about environmental risks, including possible ocean acidification and possible leak of stored CO2 from geological formation have been expressed [52]. More field tests are then necessary to prove the efficiency of CO2 sequestration. From a long-term perspective, it is only with hydrogen generated from renewable sources that a viable large scale production of hydrogen as a major clean energy carrier of the future is possible. Production of hydrogen from renewable energy, such as solar and wind energy, is certainly going to play an important role in the future energy supply. A more promising pathway, as it is environmentally friendly and more sustainable, is the electrolysis of water using renewable energy. The two most important resources necessary for its development are water and renewable energy including solar and wind energy. Algeria is a country blessed with a wide range of natural resources including hydrocarbons, biomass, solar and wind energy and water for electrolysis. This will offer the country a full range of options for the development of a hydrogen industry preferably in the framework of international cooperation [53]. Below, the most important resources relevant to hydrogen production are reported.

3.1.

Hydrocarbons

Backbone of the Algerian economy, hydrocarbons played, play and will certainly continue to play, at least in the short run, a major role in the national development. In the present state, hydrocarbons constitute the main exploited resources. Coal, another energy source, is imported. However, taking into account the technological evolutions that require other form of energy, the need to diversify the energy resources is becoming a necessity. Hydrocarbon, more particularly natural gas, could be used to produce hydrogen via a variety of processes including thermal decomposition, partial oxidation, auto-thermal reforming [54,55]. As discussed before, to avoid pollution, capture and sequestration of CO2 emissions are possible. The In Salah aquifer, one of the largest sequestration and storage fields [56] could be used. The transport of hydrogen towards potential national and international consumers could be insured via the existing dense pipeline network [57]. However, taking into account the limited character of the hydrocarbons, this will not insure a sustainable production of hydrogen. In addition the increase in the local consumption needs risks not only to undermine the strategic role assigned to hydrocarbons but also to be, in the long-term, bigger than the national production. We have then Algeria becoming an energy importing instead of an energy exporting country.

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Oil

As of January 2006, the proven oil reserves in Algeria are estimated at 12.27 billion barrels by the Oil and Gas Journal [27]. However, Algeria is considered under explored and it is believed that the oil potential is much larger. Exploration activities are underway and in the last years new oil wells have been discovered. The largest oil field is located in Hassi Messaoud in central Sahara. With its proven reserve of 6.4 billion barrels, it is the most significant and the largest reservoir. It contains about 60% of the country proven oil reserves [59]. The second largest field is situated in Rhourde El Baguel with about three billion barrels of proven oil reserves. Other major fields are located in Hassi R’mel, Tin Fouye Tabankort Ordo, Zarzaitine, Haoud Berkaoui/Ben Kahla, and Ait Kheir. A new oil field has lately been discovered in the Berkin basin and preliminary estimate has indicated that the oil reserves are high and could reach several billion barrels. More than 3850 km oil pipeline network facilitates the transfer of crude oil to coastal export terminals or to refineries, with most of the important pipelines transiting through Hassi Messaoud oil field [59]. The refineries, located on the Mediterranean coast line, not only meet most of the country oil product needs but export. With negligible sulphur content, Algeria oil is among the highest quality in the world. As shown in Fig. 3, the crude oil production has been steadily increasing these last years. In 2005, this production has reached, including lease condensate and natural gas plant liquids, 2.08 million barrels per day. This represents an increase of 5.5% over 2004, 10% over 2003 and about 40% over 2000. At the 2005 production rate and with actual proven reserves, the lifespan of oil is less than a quarter of a century; but with Algeria plans to increase its production to 2.0 million barrel per day of crude oil by the year 2010, this lifespan will be even shorter. This increase in production is dictated not only by the export demand but also, as shown in Fig. 4, by the domestic consumption that is increasing very fast.

3.1.2.

Gas

According to the Oil and Gas Journal [58], the proven natural gas reserves in Algeria are estimated at about 4.6 trillion cubic

Oil consumption ( 103 barrels/day)

3.1.1.

international journal of hydrogen energy 33 (2008) 4476–4487

200

150

100

50

1965

1970

1975

1980

1985

1990

1995

2000

2005

Year Fig. 4 – Evolution over the years of local oil consumption.

meters placing Algeria in the seventh rank at the world level. However, the recoverable reserves are much higher; they could be as high as 8 trillion cubic meters. In Algeria the largest natural gas field is situated in Hassi R’mel, 450 km south of Algiers. Its reserves represent half of all the Algerian proven reserves. The other fields are situated in the south and southeast regions such as the Rhourde Nouss, the In Amenas and the In Salah region. Lately a major natural gas field was discovered in the Reggane Basin in southwestern Algeria. As shown in Fig. 5 the production of natural gas has been increasing at a faster pace. There is an increase of about 7.3% in 2005 over 2004. At this rate of production the lifetime of natural gas will be a little more than half a century. But, if we take into consideration the recoverable reserves, the lifetime span would approach a century. However, this seems unlikely as the production is going to increase pushed first by the ever increasing demand and then by the deliberate politics in encouraging the use of natural gas. This could be seen through the consumption statistics. From Fig. 6, we can see that the increase in natural gas consumption

2,0

100

Gas production ( 109 m3)

Oil production (106 barrels/day)

250

1,5

1,0

80

60

40

20

0

0,5 1965

1970

1975

1980

1985

1990

1995

2000

2005

Year Fig. 3 – Evolution of Algerian oil production over the last 40 years.

1970

1975

1980

1985

1990

1995

2000

2005

Year Fig. 5 – Evolution of Algerian natural gas production over the years.

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international journal of hydrogen energy 33 (2008) 4476–4487

It is also worth mentioning the projects of the hybrid solar gas thermal power stations that are underway [65]. It is particularly in connection with renewable energy that the production of hydrogen takes a major significance. Hydrogen plays a role as a clean energy carrier. Energies where hydrogen can play this role are mainly solar, wind and geothermal energy.

Gas consumption (109 m3)

25

20

15

3.2.1.

10

5

0 1965

1970

1975

1980

1985

1990

1995

2000

2005

Year Fig. 6 – Evolution of local natural gas consumption over the years.

in 2005 over 2004 is about 9.8%; this is a higher value than in production indicating an expansion in gas use. Two integrated infrastructure pipeline networks are used for the transport and distribution of natural gas; one for export and the other one for domestic needs. Hassi R’mel, the major natural field is the center of all the natural gas infrastructure networks. An over 1650 km gas pipelines connect Hassi R’mel to the major natural gas fields. For local needs, a system of 1550 km gas pipeline link Hassi R’mel to the coastal Mediterranean cities. The export network is composed of two major gas pipelines. An 1100 km line links Hassi R’mel, via Tunisia, to Italy and a 1600 km runs from Hassi R’mel, via Morocco, to Spain. To reinforce the export capacities and to meet the international commitments, three projects are underway. The first concerns the pipeline linking Algeria to Spain with possible extension to France [60]. The second is the 1500 km gas pipeline connecting Hassi R’mel to heartland Italy. The third project, unlike the others that are Trans Mediterranean, is the 7300 km Trans Saharan natural gas pipe that links the gas fields of Warri in Nigeria, via Niger, to Hassi R’mel [61].

3.2.

Renewable energy

Algeria is richly endowed with renewable energy resources. However, these resources are still commercially under exploited or even untapped. Indeed, modern and intensive use of this energy, which requires the suitable technology development for the collect, the storage and the conversion, is still in the stage of development. It should be though noted that the use of solar energy, even at the rudimentary level such as the drying of food, is an ancestral tradition. In recent years, Algeria started paying more attention to developing its ‘‘clean’’ energy resources, i.e., renewable energy resources [62]. Besides the residential sector where there is a dynamic for the use of solar water heater, there is the program for the solar electrification of the south [63]. With an expected daily energy of 2.17 MWh, 20 villages in the Big South have already benefited from this program [64].

Solar energy

Algeria is situated in the Sun Belt region and it is thus endowed with a high solar potential. As can be deduced from Table 1, the mean yearly sunshine duration varies from a low of 2650 h on the coastal line to 3500 h in the South. The Sahara, which includes more than 80% of the territory, offers sunshine duration always larger than 8 h/day, with values in excess of 12 h/day during the summer. Moreover, from its geographical position, the sunshine duration doesn’t present important differences between the different months of the year. This allows an equal and lengthy availability of the sun throughout the year. In addition, as shown in Table 1, the potential of daily solar energy is important. It varies from a low average of 4.66 kWh/ m2 in the north to a mean value of 7.26 kWh/m2 in the south. This means that the yearly energy potential on 80% of the territory is of the order of 2650 kWh/m2. The total daily available energy is of the order of 16.56  1015 Wh.

3.2.2.

Wind

With the fast development in its technology, wind energy has in recent years attracted a lot of attention worldwide and it is on its way to becoming a serious contender to conventional energy resources [66]. For Algeria, wind is another renewable source that is very promising. Using data from meteorological measurement [67], it has been shown that wind can play a significant role, with particularly attractive areas for wind sites located in the south west regions and in Tiaret, Maghress and Biskra regions [68]. In Table 2 the rate of geographical distribution of the wind speed for different altitudes is presented [68]. It could be deduced that wind speeds are high enough for a viable exploitation of wind energy on more than 96% of the national territory. The Great South, particularly the Adrar region, is practically uninhabited and contains an important underground

Table 1 – Regional daily solar energy and sunshine duration in Algeria Region

Coastal line

High Plateaux

Sahara

Area (km2) Mean daily sunshine duration (h) Solar daily energy density (kWh/m2) Potential daily energy (1012 Wh)

95,271 7.26

238,174 8.22

2,048,296 9.59

4.66

5.21

7.26

443.96

1240.89

14,870.63

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international journal of hydrogen energy 33 (2008) 4476–4487

3.3.

Table 2 – Wind distribution over Algeria Height (m)

30 45 60 75 90 105

Rate of wind speed distribution over the national territory (%) v<4

4
5
6
v>7

5.5 3.4 1.5 1.0 0.75 0.3

22.0 16.9 10 8.8 7.6 6.8

60.7 65.0 56.9 48.0 38.7 38.0

11.2 13.8 28.9 37.9 47.1 55.8

0.6 0.9 2.7 4.3 5.85 7.6

water reservoir. If one adds the fact that there, the wind potential is one of the most important of Algeria, it is then incontestably the best choice for the exploitation of the wind energy. The implantation of wind farms for industrial as well as agricultural development is then for good reason more than recommended.

3.2.3.

Geothermal energy

Geothermal is another promising renewable energy resource. The potential is estimated at 460 GWh/year [69]. More than 200 hot and mineralized natural self-flowing springs exist in Northern Algeria with most of them located in the north east [70]. About two-thirds of the geothermal resources can be classified in the low temperature fields group and the remainder mainly in the moderate temperature fields group. For the south, studies on the determination of the potential of these fields are still in progress. Preliminary studies have shown an important temperature gradient in the Tindouf region [71]. Furthermore the lower Sahara sedimentary basin encloses an important hot water (around 50  C) reservoir. So far the applications are limited to agricultural (heating of greenhouses, aquaculture), space heating, sanitary or balneotherapy. Prospect of geothermal energy use for hydrogen production is good, particularly for the supply of heat, through the hot water, for high temperature electrolysis [72].

3.2.4.

Biomass

Biomass, one of the non-intermittent renewable energy sources, is the focus of much attention for the production of hydrogen [73,74]. Biomass hydrogen can be obtained either from the culture of dedicated energy crops or from various wastes and residues such as organic municipal waste, sewage and agroresidues. In Algeria, data for a meaningful evaluation of biomass potential are scarce. However, rough estimates give a value of 2  106 m3/year of forest and agriculture products, and of industrial and domestic wastes being processed [62]. Olive and dates residues are the most significant resources with high biomass potential. Indeed, with a production of about 500,000 tonnes, dates production is the most important agricultural activity in the Sahara desert; and with a production around 293,600 tonnes of olives, Algeria is one of the leading countries in olive trees cultivation [75]. Studies have shown that the conversion of the residues of these two agricultural products into biofuel represents a real potential [76–79].

Water resources

The total conventional water resources are evaluated at 14  109 m3/year with the exploitable resources being of the order of 7.9  109 m3/year [80]. These resources are fed essentially by rainfall. However, the repartition of this rainfall is characterized by its regional variability and its irregularity from year to year. Chronic drought years can be followed by wet years. Water consumption is of the order of 6.07  109 m3/year which amounts to 201 m3/capita; 65% of the water is used for irrigation, 22% for drinking and the remaining 13% for industry [81]. Conventional water resources are rare, limited and unevenly distributed. More than two-thirds of the exploitable surface water resources are located in four basins situated in a total area that represents only 3% of the area of the whole country [82]. Fortunately, the non-conventional water resources are important [41,83]. These resources include sea water for desalination, the huge Albian underground aquifer and the domestic and industrial waste water. These resources can not only compensate for any deficit but spearhead important development projects. Waste water is estimated at about 820  106 m3/year; but its treatment and reuse are still at their first stages. With access to sea on a coastal line of 1200 km, water desalination represents the best mean to meet the water needs of the population and the industry that are concentrated along the coast and the high Plateaux. So far 21 monobloc stations with a total capacity of 57,500 m3/day are under exploitation. With an objective to reach a production capacity of 1.89  106 m3/day by the year 2009, an ambitious project to install big stations of water desalination is underway. This will not only alleviate the pressure put on the conventional water sources but provide also water for the high Plateaux region. If the Sahara is the driest region in the world, it contains nonetheless a huge underground aquifer. Stretching from west of Libya and Tunisia to Adrar and Biskra, and from Laghouat to Illizi, this aquifer covers an area of 800,000 km2. Reserves are estimated at 6  1013 m3. Its depth varies from west to east. It is a few tens of meters in the Adrar region, a few hundreds of meters in the regions of Ghardaia and Ourgla, and more than 1700 m in the Touggourt region.

4. Potential of solar hydrogen PV water electrolysis production Water electrolysis for hydrogen production is a widely used technique that has reached the industrial phase. The use of solar energy in the electrolysis processes turns out to be the most viable and the most protective of the environment. As the DC power generated using photovoltaic panel is well suited for electrolysis systems, most of solar hydrogen production systems use PV as a power generator for water electrolysis [84–88]. The PV-electrolyser system is particularly interesting as it offers flexibility and modularity and it is technologically mature [89].

international journal of hydrogen energy 33 (2008) 4476–4487

Efficiency of electrolysis systems can be improved by operating at high temperature. This reduces the energy needed to activate the electrolysis process [90]. It has been suggested that heat could be obtained from geothermal sources [91]. Algeria has a huge solar and photovoltaic potential [92]. There are real possibilities for water electrolysis hydrogen production using photovoltaic energy. In the following, an estimation of the potential of hydrogen production using this technique is evaluated.

4.1.

PV-electrolysis system

A common PV-electrolysis system includes: 1. A PV array for collecting and converting solar energy into the electrical energy needed by the electrolysis unit for the splitting of water. The efficiency of the PV collector depends on the nature of the photovoltaic cells and the meteorological condition; but it is usually just a little more than 10–12% [93]. Recent studies [94, 95] have shown that the efficiency is function of the ambient temperature and the solar irradiation. 2. A power conditioning unit for shaping and conditioning the power coming from the PV array. Most of the time, besides the power conditioning unit, a unit for electrical storage is necessary. The electrical storage unit is needed to insure availability of energy in the case where there is no sun power. Usually this storage unit is made up of batteries. Studies on power conditioning [96] have shown that their efficiency is as high as 97%. A more conservative value would be of the order of 85%. 3. The electrolysis unit for splitting water into hydrogen gas and oxygen gas. The efficiency of the unit depends on the nature of the electrolysis cells as wells as on its temperature, the meteorological conditions and the characteristics of the PV array. This efficiency is usually between 65% and 85% [97]. Theoretically, the energy necessary to decomposition water by electrolysis is of the order of 58 kcal/moles [98]. In practice, it is much larger. In general, it is of the order of 4–5 kWh/Nm3 [99]. 4. The hydrogen storage unit. The efficiency of this unit depends on the storage mode used. In the present study, we assume that the hydrogen produced is sent through pipelines for example to the end user. Besides these units, we must take into consideration the auxiliary unit such as the control unit, the water supply and treatment unit and the produced gas separation unit. The water used in the electrolysis could be taken from different sources. In northern Algeria, sea water could be used. In the south, the underground water of the Albian could provide the electrolysis needed water. Besides the performance of its components, the system production capability is also a function of the levels and annual distributions of the solar radiation and the PV array size, position and orientation. Solar energy has been determined using meteorological [67] and radiation measurements [100]. Different positions and orientations of the PV array have been considered. Solar radiation received per square meter of PV array has been estimated for non-tracking PV array, for

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north/south (N/S) tracking system and for east/west (E/W) tracking system [101]. For the non-tracking PV array, the tilt angle is taken equal to the location latitude; this corresponds to the near optimum solar collecting position [102].

5.

Results and discussion

First we considered the case of the non-tracking PV arrays tilted at the site latitude. Fig. 7 reports the mapping of the hydrogen production potential through the whole country. The production is expressed in l/m2/day. This figure shows that the potential is important more particularly on the west side on the coastal line and in the Big South. To study the monthly evolution, the variation of the monthly mean of the daily hydrogen production is shown in Fig. 8 for typical sites of each region: the coastal region, the north Sahara and the Big South. It can be seen that for the coastal region (Algiers and Annaba for example), the hydrogen production is not uniform all year round. The production of July is twice more important than that of December or than that of January. However, as we move from Northern Algeria to Southern Algeria, the difference between the production potentials of the different months has a tendency to decrease. The seasonal production potentials for the different sites have been compared. In Fig. 9, the monthly mean of the daily hydrogen production per meter square of PV array per day for all the sites for each season is represented. First, the seasonal production for each site is considered. Fig. 9 shows that for a given site, the production of hydrogen is not the same. The differences are particularly important in Northern Algeria. For example in Annaba, the production potential of winter represents 71% of that of autumn, 60% of that of spring and only 50% of that of summer. For Algiers, these values are, respectively, 79%, 69% and 62%. However, these differences are distinctly much smaller for the Southern regions of Algeria and there is a more uniformly yearly

112 110 108 106 104 102 100 98 96 94 92 90 88 86 84 82 80 78 2 (l/m /day)

Fig. 7 – Hydrogen production potential for non-tracking PV arrays tilted at latitude.

international journal of hydrogen energy 33 (2008) 4476–4487

Hydrogen production (l/m2/day)

Hydrogen production (l/m2/day)

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100

80 Adrar Algiers Annaba Bechar Ghardaia Oran Saida Setif

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100 Adrar Algiers Annaba Bechar Gardaia Oran Saida Setif

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60

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40 1

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9

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Month Fig. 8 – Evolution of the monthly mean of the daily hydrogen production for selected locations. Case of nontracking PV arrays tilted at latitude.

Fig. 10 – Evolution of the monthly mean of the daily hydrogen production for selected locations, case of N/S tracking.

production rate. For Adrar, the winter production rate represents 90% of that of autumn, 78% of that of spring and 71% of that of summer. For Tamanrasset these values are, respectively, 100%, 78% and 77%. Now comparing the production for different regions, it can be noticed that in winter, there are important differences in the production of the different sites. During this season, by comparison to the production of Annaba that of Tamanrasset and that of In-Guezem are, respectively, 90% and 69% more important; by comparison to Algiers production, they are, respectively, 52% and 35% more important. For the other seasons, the difference between the productions in the different sites is much less important. This is particularly true for the summer when the production in the north is as important as it is in the south. For the autumn, by comparison with the production of Annaba that of Tamanrasset is 35% more important, that of In-Guezem 32% more

important and that of Adrar about 18% more important; by comparison to that of Algiers, they are, respectively, 20%, 18% and 5%. For the spring these values are, respectively, 26%, about 17%, and 15% for Annaba, and, respectively, about 17%, 8% and 6% for Algiers. To quantify the effect of tracking on the evolution of the hydrogen production, this evolution is studied for different positions (fix tilted plane, North/South tracking and East/ West tracking). The results are presented in Fig. 8 for the non-tracking tilted plane, in Fig. 10 for the North/south tracking and in Fig. 11 for the east/west tracking. It can be seen that:

Spring Summer Autumn Winter

120

100

110

Hydrogen production (l/m2/day)

Hydrogen production (l/m2/day)

(a) There is an increase in hydrogen production using tracking systems. This is expected as, with tracking, we increase the solar energy collection. We notice also that the maximum value extends over many months. For example,

80

60

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20

O ra n ou ar gl a In G ue za M m éd ia Sa ïd a Be ja ia

rd

ai a Ta m

ar ha G

ba

ch

Be

er s

na

An

gi Al

Ad ra

r

0

Fig. 9 – Variation of the seasonal hydrogen production for different locations. Case of non-tracking PV arrays tilted at latitude.

100 90 80 Adrar Algiers Annaba Bechar Ghardaia Oran Saida Setif

70 60 50 40

1

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3

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8

9

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Month Fig. 11 – Evolution of the monthly mean of the daily hydrogen production for selected locations, case of E/W tracking.

international journal of hydrogen energy 33 (2008) 4476–4487

Hydrogen production (l/m2/day)

115 110

N/S tracking

105 100 95

E/W tracking 90 85

tilted plane 80 75 1

2

3

4

5

6

7

8

Site Fig. 12 – Evolution of the annual mean of the daily hydrogen production for selected locations and different positions and orientations of the PV arrays. (1. Adrar, 2. Algiers, 3. Annaba, 4. Bechar; 5. Ghardaia, 6. Oran, 7. Saida, 8. Setif).

for Adrar, we have a uniform production from March to September in the case of a North/South tracking. (b) For the East/West tracking, the increase in production by comparison to the non-tracking system tilted at latitude is very small for the winter and fall seasons. It is more important in the summer. (c) For the North/South tracking, the increase in production by comparison to the non-tracking system tilted at latitude is much more important than that of a East/West tracking. This increase is more significant from March to October. It can be seen that if the production for July is practically the same for all the sites under consideration, this is not the case for the other months of the year where the production is clearly much more less in the north. The difference is sometimes accentuated by the tracking systems. Finally to determine the yearly mean of the daily hydrogen production, the annual mean of the daily production per square meter of PV array for different sites is reported in Fig. 12. It can clearly be seen that the increase in production with tracking is not the same for the different sites and that this increase is relatively small for the East/West tracking. As can be deduced from Fig. 12, the relative increase with respect to the non-tracking PV arrays is more important for the North/South tracking than for the East/West tracking. This relative increase does not reach 10% for the East/West tracking, but it always exceeds 15% for all sites under consideration and even in some cases reaches 25% for the North/ South tracking.

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