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Estimation of electrolytic hydrogen production potential in Venezuela from renewable energies
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Available online at www.sciencedirect.com
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Estimation of electrolytic hydrogen production potential in Venezuela from renewable energies F. Posso a,b,*, J. Zambrano b,1 a b
Universidad de Los Andes-Nu´cleo Tachira, Departamento de Ciencias, San Cristobal 5001, Venezuela chira, San Cristobal, Venezuela Decanato de Investigacion, Universidad Nacional Experimental de Ta
article info
abstract
Article history:
An initial estimation of the potential for hydrogen (H2) production in Venezuela is made,
Received 30 November 2013
obtained by water electrolysis using electricity from renewable sources, taking advantage
Received in revised form
of the great potential of the country for solar, wind and mini hydro energies. For the first
8 May 2014
two, its potential maps is obtained from insolation and wind speed maps, respectively,
Accepted 6 June 2014
prepared from satellite data, and for mini-hydro, the potential is obtained from docu-
Available online 3 July 2014
mentary information. To calculate the amount of H2 to produce is used the Higher Heating Value, considering the electrolytic system overall efficiency of 75%, including power re-
Keywords:
quirements of the electrolyzer, auxiliary equipment, and system losses. In addition, in the
Electrolytic hydrogen production
calculation of usable renewable potential are excluded land areas under special adminis-
Solar energy
tration, marine, lake and urban areas, and other limitations are considered concerning
Solar-hydrogen energetic system
energy conversion efficiencies and useful areas available for the location of the different
Venezuela
renewable technologies. The results give a total production of 2.073 1010 kg of H2/year, with a contribution of 95% of solar photovoltaic energy. The H2 produced covers entirely the energy requirements of rural population without energy service, and the remainder could be used as a chemical feedstock in industrial processes such as oil refining or petrochemical, whose demand in not entirely satisfied with the annual production of H2 from the country, or even for export. It is concluded that the results are the initial point of a detailed research, with more accurate estimation of the potentials that include economic and social topics related with the production on H2, on the way to determine the feasibility of developing of the Solar-H2 system, in its different forms in Venezuela. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Introduction The Solar-Hydrogen Energetic System (SHES), can be defined as an energetic system in which the primary source is any
type of solar energy, direct or indirect; and the H2 is the secondary source or energetic vector. It is a clean, self-sufficient and appropriate system to overcome the drawbacks of intermittency and storage related with electric generation from renewable energy (RE), and therefore, able to motorize the
chira, Departamento de Ciencias, San Cristo bal 5001, Venezuela. Tel.: þ58 * Corresponding author. Universidad de Los Andes-Nu´cleo Ta 2763421520; fax: þ58 2763045043. E-mail addresses: [email protected], [email protected] (F. Posso), [email protected] (J. Zambrano). 1 Tel.: þ58 2763532454; fax: þ58 2763532949. http://dx.doi.org/10.1016/j.ijhydene.2014.06.033 0360-3199/Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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sustainable development of a country or region [1]. A crucial stage for the development of the SHES is the H2 production with numerous studies that demonstrates its feasibility [2,3], while working intensely to achieve in the medium term, production costs competitive with the conventional production process by reforming of natural gas, with the lowest cost currently [4]. In Latin America, Brazil is a leader in R&D on H2 production from RE, especially hydropower [5,6], In turn, although Venezuela exhibits great potential of these primary sources, its development is minimal, and, except for largescale hydro, without an effect on the energy balance of the country. Although country's degree of electrification is close to 96%, an important sector of rural population, about 25%, has no permanent energy services, for this reason is difficult, expensive, and therefore improbable, its satisfaction with the traditional energy system [7]. Since these rural communities are disseminated throughout the country, probably located in areas with exploitable potential of solar energy, its energy needs could be met by SESH in its various forms, thus overcoming the situation of energy deprivation. Complementarity and synergy between electricity and H2 would allow the energy autonomy to these isolated and depressed areas, improving their quality of life, stimulating the local economy to be employment-intensive, preserving the culture and sustainable endogenous development. Moreover, it is also recognized that any action or project that proposes the SESH implantation, requires a primary estimation of potential H2 production because it would be an appropriate starting point for more comprehensive studies on the feasibility of a specific SESH. In this context, the principal objective of this paper is to make a preliminary estimate of the production potential of electrolytic H2 in Venezuela from those forms of solar energy with potential of a significant magnitude in the country, considering its use as an energy vector in the rural areas of the country, and eventually as an input in improvement processes of heavy crudes, refining and petrochemical. An important contribution associated to the purpose of this paper is the free access software, HYDRA (H2 Demand and Resource Analysis) developed by the National Renewable Energy Laboratory (NREL), that provides information about demand, sources, production, costs, infrastructure and distribution of H2 for a determined country [8]. About the H2 production potential, it includes different fossil and renewable sources, and presents the results in different potential maps with different detail level, thus, for the US, the software shows the production potential for states and counties, while for Latin America it does not show results, maybe for the lack of information about renewable resource in the region. In fact, there is not documental evidence about the renewable H2 production in these countries, but are available estimations for specific regions in several countries and for some RE, then some essential cases are presented. rdoba province from Argentina the production In the Co potential of H2 obtained by electrolysis for the automotive sector has been evaluated using the wind energy as electric source. The wind energy is evaluated based on wind maps of the province, and are selected whose regions with levels above Class 4, a capacity factor of 0.39 is considered, excluding natural areas and those with gradients above 20%, for the electrolysis system an efficiency of 75% is assumed. The
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yearly total amount of H2 generated in 10 departments of the Province is 3.734 107 Ton H2/year, enough for providing until 10 times the energy required for the automotive sector of the entire province [9]. A prospective study about the viability of H2 production considering the wind potential of La Patagonia, this energy is accounted with the use of seven weather station located at southern Chilean lands, using meteorological and statistical models, getting a capacity factor of 0.55 for wind source. The H2 is produced by electrolysis with unsalted sea water, after that, the liquid H2 is transported by ship to the central region for its use. The H2 production is equivalent to substitute 7.1% of oil consumption it is around 380,000 kg H2/year [10]. In Ecuador the potential of H2 production from hydroelectricity is evaluated, the study considers that certain turbinable spilled water in several hydroelectric plants over the country could be used to additional generation oriented to H2 production by electrolysis. The hydroelectric plant HidroPaute is selected for the study; it has an installed capacity of 1100 MW, contributing with 32% of total generation of the country, with a capacity factor of 62% in 2011. Two scenarios of H2 production are considered: in the first one is assumed that is available a 30% of water spilled in 2011; in the second situation this amount is duplicated. Considering an electrolysis process efficiency of 75%, it has obtained for the first scenario 5400.8 Ton H2/year and 10,801.7 Ton H2/year for the second one, which is used for chemical and energy requirements [11]. In Brazil [3] have studied the H2 production from solar photovoltaic (PV), wind, and hydroelectricity energies, the same sources considered in this paper. The study evaluates the technical and economic performance of a hypothetical production plant of electrolytic H2 with a capacity of 30 MW located at northeast Brazil. The evaluation of the potential of generation of solar PV and wind energies is based on the Solar Atlas and Brazilian Wind Potential Atlas, the hydroelectric energy is provided by a Hydroelectrical Central located at northeast of the country and it is able to deliver the required energy to surpass the electrical requirements of the electrolysis plant. It is considered an availability factor of 95%, conversion efficiency of 80%. The overall annual production is 56.26 106 m3 H2/year, for export only. In other ambit [2], have estimated the amount of H2 from renewable energies available in the US, with the use of solar PV and wind energies, with the aim to provide the automotive sector. The potential from both sources is estimated with software based on GIS. For the solar option, the radiation data corresponds to monthly means for 40 km2 cells, considering 3% of this area for solar photoelectric conversion, excluding forest parks, marine and lake areas, assuming 10% of solar PV efficiency. For the wind case, are considered the winds Class 3 or higher, and placing in every cell turbines of 5 MW and also considering the mentioned exclusions. The efficiency for the electrolysis process is 75% and the results are expressed with a potential map of the country, organized by counties, obtaining an overall annual potential of 1.110 1012 kg H2/ year for 2010. From this revision, is clear that methodology used to calculate the production potential of H2 by electrolysis, has the following characteristics: a. the use of potential maps of the renewable resources, generated thought different models
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with data from weather stations or satellite measurements, as input variables. b. The use of capacities and efficiencies factors to calculate the usable renewable energy, considering the available area for siting the devices for energetic conversion. c. The H2 amount that could be obtained is calculated accounting the efficiency of the electrolysis process and the availability of H2 production plant. Finally, the potential of H2 production for Latin American countries has been treated very little, studies are for specific regions of a country and for different purposes, which is not exactly use in the rural sector, whose population in a significant percentage lacks permanent energy service. The aim of this work is to contribute to both.
Table 2 e Comparison between renewable energy potentials of several countries [13]. Country
Solar potential (TWh/year)
Wind Potentiala (km2)
Argentina Bolivia Colombia Ecuador Guyana Mexico Peru Suriname Venezuela
7853.43 3220.15 2889.94 606.28 575.82 6469.15 3576.84 402.46 2586.86
418,022.00 26,611.00 57,996.00 229,084.00 N.A. 38,687.00 671,212.00 N.A. 10,950.00
a
Renewables energies in Venezuela Venezuela exhibits a great potential of RE in their different types, as indicated in Table 1. However, its development in the country is negligible, largely due to Venezuela also has large reserves of fossil fuels, especially oil, considered the largest in the world, and whose intensive operation for over 60 years, have shaped the energy sector, the country economy and even the Venezuelan society itself. Additional data for gross RE potential for Venezuela is presented by the NREL [13] and predicts 258,686 TW/year of potential for solar energy and estimates winds Class 3e7 with an area of 10,950 km2, a brief comparison between RE potentials of the countries within the region is shown in Table 2. It can be noticed that Venezuela has a solar potential similar to other nearby countries but its wind potential is very low due to geographical restrictions related to the coastal mountain range. Also, are available more accurate estimations of the solar and wind potentials [14,15], in form of potential maps, as shown in Fig. 1, which have been made from satellite measurements of average annual values of wind speed and insolation, respectively, corresponding to grids of 1 of longitude and latitude, setting a two-dimensional matrix located between 73 and 60 west longitude and between 12 and 1 north latitude, Fig. 2. These values are the basis for the calculation of potential production of H2 in Venezuela. In harnessing the RE, the Venezuelan government has been pushing several actions to promote and develop them, and the most important are: the construction of two wind
Table 1 e Renewable energy potential in Venezuela [8]. Source Mini-hydro Bioenergy Solar energy Wind energy Geothermal energy Others RE Large scale hydro
Specifications
Potential (GW)
Until 50 MW/utility Firewood, plantings, waste 15% conversion, 1% NTa, 0.3 MPb 3% conversion, 4% NT 2.5 NT Oceanic, hybrid
4.5 11.7 157.2 48.9 5.2 18.36 63.8 309.6
Total a b
National territory. Marine platform.
Winds class 3e7 at 50 m.
farms, located in the northwestern coastal area, with a total generating capacity of about 200 MW, right now in its initial operation, generating about 25 MW that are delivered to the electric grid [16], Regarding the solar photovoltaic (PV), the program “Sembrando Luz”, designed to provide permanent and efficient energy services to the rural and isolated populations that are not connected to the traditional power grid, had installed for 2012 around 3139 systems, with a total power of 2.5 MW supplying more than 257 thousand residents of 1020 rural communities [17]. Other types of RE, there are only small initiatives with no effect on the energy balance of the country.
The hydrogen market in Venezuela Hydrogen production The overall H2 produced in Venezuela, in 2010, reached 4850 MNm3 H2 [16], is produced via natural gas reformed, and is captive class, because it is fully consumed where it is generated. There is currently a deficit of H2 with chemical purposes that is estimated to rise with the increase of oil activity in the Faja del Orinoco and materialize expansions in petrochemical plants, according to PDVSA's development plans in the medium term [18].
Hydrogen consumption The H2 produced “in situ” is used as an input in the process of: a. Improvement of heavy oil, in order to obtain a synthetic oil, syncrude, with a higher commercial value, b. hydrogenation in the production of fuels derived from petroleum, and c. Petrochemical processes, especially for the production of ammonia [17]. If the H2 from renewable sources is used as a vector to satisfy the energy needs of the rural sector, the required amount is obtained by considering the energy consumption per capita in this sector, that arises to 191 kWh/year and the number of people to provide energy reaches 828,000 hab [19]. Then, assuming a 75% efficiency in the conversion in the electrolysis process respect to the higher heating value (HHV), the amount of H2 required is: CH2 ¼
CPC NH FCE
(1)
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Fig. 1 e Wind map (Left). Insolation map (Right).
CH2
kWh 191 year ð828; 000 habÞ hab kg H2 ¼ 3012342:86 ¼ year kWh 52:5 kg H2
(2)
Hydrogen production in Venezuela from RE General considerations This study considers as primary renewable sources for H2 production the solar direct energy, and indirect solar classified in: small hydro and wind, all usable with great potential in Venezuela [12,13]. In every case, H2 is produced by electrolysis of water with electricity generated from the selected RE,
(Fig. 3). It is clear that the HHV energy is used as a basis for calculation, with an overall efficiency of 75%, which includes the requirements of the electrolyzer and auxiliary equipment, and losses of the electrolytic system [2]. Moreover, in determining the land area available for harnessing the potential of RE, certain restrictions are taken considered, such as: a. Areas under Special Administration Regime (ABRAE, for its acronym in Spanish), defined as protected areas, covering an area equivalent to 46% of the land surface [20], including national parks and recreational, natural monuments, biosphere reserves and wildlife. b. Urban areas, obtained from distribution maps of urban populations are also excluded [21], and whose occupancy rate is taken into account in the grid that corresponds to the geopolitical distribution of these settlements.
Fig. 2 e Bidimensional grid used for the potential estimation of H2.
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Fig. 3 e Routes for the production of electrolytic hydrogen from some RE.
Hydrogen production
power. Equation (5) expresses the instantaneous power produced by a PV system:
In this case, the SESH basically consists in the coupling a PV power generation, wind and mini-hydroelectric system with an electrolytic system. Although its development and widespread use involves overcoming several technological and economic challenges, is one of the most promising routes for the production of renewable H2 [22,23]. On the other hand, considering that this is a potential estimation study, it is assumed that all the energy produced by renewable means will be used in the transformation process to H2. The possible routes for the production are shown in Fig. 3.
Establishment of usable areas To obtain the potential of solar photovoltaic and wind energy, primary information is taken from NASA [24], which consists of representative values of certain meteorological variables and corresponding to the two-dimensional mesh shown in Fig. 2 in which each of the 89 squares has an area of 12,100 km2. Taking into account that the procedure for determining the H2 production is the same for all grid cells that include the Venezuelan territory, as an illustration of the calculation for one square is presented, the number 34, selected because exhibits an insolation value very close the national average. The useful area per grid as a function of the grid area (AU), the ABRAE and the factor of available area (fA,D) is presented in Equation (3). AU ¼ AC ABRAE fA;D
(3)
PPV ¼ GT AN;FV factiv hcell hinv hother
(5)
where GT is the actual total radiation, Npanel the number of PV panels, AN,FV is the net superficial area with PV panels, factiv is the fraction of superficial area with active solar cells, hcell is the conversion efficiency of the PV module, hinv is the conversion efficiency of the DCeAC inverter and the parameter hother is proposed by CEC [26] as shown in Equation (6), where hother corresponds to the deviation of standard condition of test, htemp is the reduction factor for temperature, hloss is the reduction factor for electrical losses and hdirt is the reduction factor for dirt. hother ¼ hstd htemp hloss hdirt
(6)
Also, the annual average insolation over a daily basis as a function of GT(i) is: P8760 hr Fdaily ¼
GTðiÞ Dti 365 day
i¼1
(7)
From Equations (5), (6) and (7) and considering that Dti corresponds to a step of 1 h, the annual energy by PV is presented in the Equation (8): EPV;annual;C ¼ ð365 dayÞFdaily AN;FV factiv hcell hinv hstd htemp hloss hdirt
The net area of the grid (AN,C) is obtained from Equation (4), considering the population factor (fP):
The parameters associated with the production of solar PV to any grid are presented in Table 4, and specifically to the grid 34, from the Equation (8):
AN;C ¼ AU 1 fP
EPV;annual;C ¼ 1:515 1010 kWh=year
(4)
The influencing parameters in the calculation of (AN,C) are shown in Table 3.
PV model The proposed model uses a modification of the simple model of EnergyPlus Engineering Reference [25], in which the radiation incident on the PV panel is multiplied by several factors for efficiency parameters that adjust the maximum usable
Wind model This alternative for producing renewable H2 has attracted considerable interest, particularly in the case of hybrid
Table 4 e Parameters associated with the production of solar PV [24,26,27]. Parameter
Value
Fdaily ðkWh=m dayÞ AN;FV ¼ AN;C ðkm2 Þ factiv hcell hinv hstd htemp hloss hdirt 2
Table 3 e Parameters influencing the selection of usable area. Parameter AC (km2) ABRAE fA,D fP
Value 12,100 54% 1% variable
5.55 65.34 86.5% 20.8% 90% 95% 90% 95% 93%
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systems, in conjunction with PV and Solar Thermal systems [22]. For the calculation of production H2 potential, are taken into account only those two-dimensional mesh grids with winds of Class 2 or higher, i.e., winds with a speed equal to or greater than 4.4 m/sec, considered economically viable for generating electricity with current technology or for it develop in the short term [2], that imply consider the 20% of the squares of the mesh. To predict the power output of the wind system, a simplified model shown in Equation (9) is used, a reference performance curve of a commercial wind turbine for low speed is selected [28], which is shown in Fig. 4, and then the maximum power ðPaeroðvwind Þ Þ as a function of wind speed is directly obtained. Also is considered the efficiency of a DCeAC inverter hinv and the corresponding electrical losses factor hloss. Pwind ¼ Paeroðvwind Þ hinv hloss
8760 Xhr
Ewind;annual;C ¼ 3:363 108
kWh year
(8)
The annual average wind energy captured by each grid ðEwind;annual;C Þ, is calculated from Paeroðvwind Þ as a function of average annual wind speed obtained from NASA [19], the number of wind turbines in the park (Nturb) and the effectiveness factor of the array farr, as shown in Equation (10). Ewind;annual;C ¼ Nturb farr
Fig. 5 e Selected arrangement for the wind model.
PwindðiÞ Dti
(9)
i¼1
Due to the fluid dynamic interference, wind farms typically produce less energy than the sum of these wind turbines placed isolated, such the location of wind turbines should be optimized depending on the characteristics of wind and terrain. . Performed studies have found that a separation of turbines 8e10 rotor diameters in the prevailing wind direction and 5D in the perpendicular direction results in energy losses to lower 10% [29,30]. With the intention of consider an arrangement that minimizes the failures, the configuration in Fig. 5 is proposed. For the selected arrangement, the equivalent area of each turbine is equivalent to5D 10D, equivalent to 605,000 m2, with reference to the net area of the grid (AN,C), Then should be placed in it about 81 turbines. Considering the selected wind turbine, the average wind speed in the grid example for the wind case (No. 4) is 6.18 m/s, the efficiency factors are similar to those presented in the PV case and the photovoltaic efficiency factor is 90%, the total annual wind energy of that grid, according to Equation (10) is:
Mini-hydro model To obtain the mini hydro potential, the information in Table 1 is taken, in which the production capacity for this item (PMH) is 4.5 GW, and considering that this resource can be continuously exploited, can be said that the annual mini hydropower nationwide is given by Equation (12): EMH;annual ¼ PMH ð8760 hrÞ
(10)
Resulting: EMH ¼ 3:942 1010
kWh year
Total renewable energy To obtain the total annual renewable energy (ET) that can potentially be used for production of H2, must be added the energy produced in each grid for PV, wind and mini-hydro power, according to Equation (11). ET ¼ ET;PV þ ET;wind þ ET;MH
ET;FV ¼
89 X
EFV;annual;C ðiÞ
i¼1
ET;eolica ¼
89 X
(11)
Ewind;annual;C ðiÞ
i¼1
Then, the total renewable energy for every source is: ET ¼ 1:146 1012 kWh=year ET;PV ¼ 1:088 1012 kWh=year ET;wind ¼ 1:825 1010 kWh=year ET;MH ¼ 3:942 1010 kWh=year
Calculation of amount of hydrogen to obtain For the calculation of H2 to obtain, the Equation (11) is used, in which is required the total renewable energy (ET) and energy conversion factor for H2 (FCE), in which an availability factor (fav) representing the period devoted to maintenance and the value of 0.95 has been reported for the case of H2 production plants by electrolysis [5,19] mH2 ¼
Fig. 4 e Power curve for the selected wind turbine (P ¼ 2000 kW D ¼ 110 m) [23].
E fav FCE
(12)
Finally the annual amount of H2 for each renewable source and the total are presented in Table 5. A summary of the potential reported in the literature and obtained for Venezuela is shown in Table 6, although it is not
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Table 5 e Results by type of renewable energy and overall. RE type
Production H2 (kg/year)
PV Wind Minihydro Total
Contribution (%)
10
1.968 10 3.303 108 7.134 108 2.073 £ 1010
94.96 1.59 3.45 100
h
Table 6 e Reported H2 production potentials. Country, region rdoba Argentina, Co Brazil, Ceara Chile, Patagonia Ecuador, Azuay USA Venezuela
Potential (kg H2/year) 6
37.34 10 5.06 106 3.8 105 10.8 106 1.110 1015 2.073 1010
Year 2010 2010 2010 2014 2005 2014
possible a fair comparison between them, correspond to different situations and conditions, if it is useful for an understanding of the order of magnitude production potential of H2 in Venezuela, compared to other countries in Latin America.
Conclusions It have been determined the total potential production of H2 in Venezuela by water electrolysis with electricity from renewable sources, considering solar PV, wind and mini-hydro energy, all with large potential in Venezuela. Of these, the first is the largest contribution mainly due to an exploitable potential distributed throughout the country, which does not happen in the remaining two. The total H2 produced completely covers the electric energy requirements of unattended rural population, the remainder can be used as input in different chemical processes. These results represent a starting point for more elaborate and exhaustive studies, including economic, social and environmental aspects involved in intensive development of H2 as an energy vector in Venezuela.
Acknowledgments n of the Universidad Nacional To Decanato de Investigacio chira for the financial support for the Experimental del Ta realization of this paper.
Nomenclature Variables A area cuad square grid D diameter E energy f factor FCE energy conversion factor
G m N P C F
solar radiation mass number power consumption insolation efficiency
Sub-indexes A area activ active arr array av availability C square grid cell PV cell D available PV photovoltaic H habitant inv inverter MH mini-hydro N net P population PC per capita loss electric loss std standard T total temp temperature turb turbine U useful
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Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/locate/he
Estimation of electrolytic hydrogen production potential in Venezuela from renewable energies F. Posso a,b,*, J. Zambrano b,1 a b
Universidad de Los Andes-Nu´cleo Tachira, Departamento de Ciencias, San Cristobal 5001, Venezuela chira, San Cristobal, Venezuela Decanato de Investigacion, Universidad Nacional Experimental de Ta
article info
abstract
Article history:
An initial estimation of the potential for hydrogen (H2) production in Venezuela is made,
Received 30 November 2013
obtained by water electrolysis using electricity from renewable sources, taking advantage
Received in revised form
of the great potential of the country for solar, wind and mini hydro energies. For the first
8 May 2014
two, its potential maps is obtained from insolation and wind speed maps, respectively,
Accepted 6 June 2014
prepared from satellite data, and for mini-hydro, the potential is obtained from docu-
Available online 3 July 2014
mentary information. To calculate the amount of H2 to produce is used the Higher Heating Value, considering the electrolytic system overall efficiency of 75%, including power re-
Keywords:
quirements of the electrolyzer, auxiliary equipment, and system losses. In addition, in the
Electrolytic hydrogen production
calculation of usable renewable potential are excluded land areas under special adminis-
Solar energy
tration, marine, lake and urban areas, and other limitations are considered concerning
Solar-hydrogen energetic system
energy conversion efficiencies and useful areas available for the location of the different
Venezuela
renewable technologies. The results give a total production of 2.073 1010 kg of H2/year, with a contribution of 95% of solar photovoltaic energy. The H2 produced covers entirely the energy requirements of rural population without energy service, and the remainder could be used as a chemical feedstock in industrial processes such as oil refining or petrochemical, whose demand in not entirely satisfied with the annual production of H2 from the country, or even for export. It is concluded that the results are the initial point of a detailed research, with more accurate estimation of the potentials that include economic and social topics related with the production on H2, on the way to determine the feasibility of developing of the Solar-H2 system, in its different forms in Venezuela. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Introduction The Solar-Hydrogen Energetic System (SHES), can be defined as an energetic system in which the primary source is any
type of solar energy, direct or indirect; and the H2 is the secondary source or energetic vector. It is a clean, self-sufficient and appropriate system to overcome the drawbacks of intermittency and storage related with electric generation from renewable energy (RE), and therefore, able to motorize the
chira, Departamento de Ciencias, San Cristo bal 5001, Venezuela. Tel.: þ58 * Corresponding author. Universidad de Los Andes-Nu´cleo Ta 2763421520; fax: þ58 2763045043. E-mail addresses: [email protected], [email protected] (F. Posso), [email protected] (J. Zambrano). 1 Tel.: þ58 2763532454; fax: þ58 2763532949. http://dx.doi.org/10.1016/j.ijhydene.2014.06.033 0360-3199/Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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sustainable development of a country or region [1]. A crucial stage for the development of the SHES is the H2 production with numerous studies that demonstrates its feasibility [2,3], while working intensely to achieve in the medium term, production costs competitive with the conventional production process by reforming of natural gas, with the lowest cost currently [4]. In Latin America, Brazil is a leader in R&D on H2 production from RE, especially hydropower [5,6], In turn, although Venezuela exhibits great potential of these primary sources, its development is minimal, and, except for largescale hydro, without an effect on the energy balance of the country. Although country's degree of electrification is close to 96%, an important sector of rural population, about 25%, has no permanent energy services, for this reason is difficult, expensive, and therefore improbable, its satisfaction with the traditional energy system [7]. Since these rural communities are disseminated throughout the country, probably located in areas with exploitable potential of solar energy, its energy needs could be met by SESH in its various forms, thus overcoming the situation of energy deprivation. Complementarity and synergy between electricity and H2 would allow the energy autonomy to these isolated and depressed areas, improving their quality of life, stimulating the local economy to be employment-intensive, preserving the culture and sustainable endogenous development. Moreover, it is also recognized that any action or project that proposes the SESH implantation, requires a primary estimation of potential H2 production because it would be an appropriate starting point for more comprehensive studies on the feasibility of a specific SESH. In this context, the principal objective of this paper is to make a preliminary estimate of the production potential of electrolytic H2 in Venezuela from those forms of solar energy with potential of a significant magnitude in the country, considering its use as an energy vector in the rural areas of the country, and eventually as an input in improvement processes of heavy crudes, refining and petrochemical. An important contribution associated to the purpose of this paper is the free access software, HYDRA (H2 Demand and Resource Analysis) developed by the National Renewable Energy Laboratory (NREL), that provides information about demand, sources, production, costs, infrastructure and distribution of H2 for a determined country [8]. About the H2 production potential, it includes different fossil and renewable sources, and presents the results in different potential maps with different detail level, thus, for the US, the software shows the production potential for states and counties, while for Latin America it does not show results, maybe for the lack of information about renewable resource in the region. In fact, there is not documental evidence about the renewable H2 production in these countries, but are available estimations for specific regions in several countries and for some RE, then some essential cases are presented. rdoba province from Argentina the production In the Co potential of H2 obtained by electrolysis for the automotive sector has been evaluated using the wind energy as electric source. The wind energy is evaluated based on wind maps of the province, and are selected whose regions with levels above Class 4, a capacity factor of 0.39 is considered, excluding natural areas and those with gradients above 20%, for the electrolysis system an efficiency of 75% is assumed. The
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yearly total amount of H2 generated in 10 departments of the Province is 3.734 107 Ton H2/year, enough for providing until 10 times the energy required for the automotive sector of the entire province [9]. A prospective study about the viability of H2 production considering the wind potential of La Patagonia, this energy is accounted with the use of seven weather station located at southern Chilean lands, using meteorological and statistical models, getting a capacity factor of 0.55 for wind source. The H2 is produced by electrolysis with unsalted sea water, after that, the liquid H2 is transported by ship to the central region for its use. The H2 production is equivalent to substitute 7.1% of oil consumption it is around 380,000 kg H2/year [10]. In Ecuador the potential of H2 production from hydroelectricity is evaluated, the study considers that certain turbinable spilled water in several hydroelectric plants over the country could be used to additional generation oriented to H2 production by electrolysis. The hydroelectric plant HidroPaute is selected for the study; it has an installed capacity of 1100 MW, contributing with 32% of total generation of the country, with a capacity factor of 62% in 2011. Two scenarios of H2 production are considered: in the first one is assumed that is available a 30% of water spilled in 2011; in the second situation this amount is duplicated. Considering an electrolysis process efficiency of 75%, it has obtained for the first scenario 5400.8 Ton H2/year and 10,801.7 Ton H2/year for the second one, which is used for chemical and energy requirements [11]. In Brazil [3] have studied the H2 production from solar photovoltaic (PV), wind, and hydroelectricity energies, the same sources considered in this paper. The study evaluates the technical and economic performance of a hypothetical production plant of electrolytic H2 with a capacity of 30 MW located at northeast Brazil. The evaluation of the potential of generation of solar PV and wind energies is based on the Solar Atlas and Brazilian Wind Potential Atlas, the hydroelectric energy is provided by a Hydroelectrical Central located at northeast of the country and it is able to deliver the required energy to surpass the electrical requirements of the electrolysis plant. It is considered an availability factor of 95%, conversion efficiency of 80%. The overall annual production is 56.26 106 m3 H2/year, for export only. In other ambit [2], have estimated the amount of H2 from renewable energies available in the US, with the use of solar PV and wind energies, with the aim to provide the automotive sector. The potential from both sources is estimated with software based on GIS. For the solar option, the radiation data corresponds to monthly means for 40 km2 cells, considering 3% of this area for solar photoelectric conversion, excluding forest parks, marine and lake areas, assuming 10% of solar PV efficiency. For the wind case, are considered the winds Class 3 or higher, and placing in every cell turbines of 5 MW and also considering the mentioned exclusions. The efficiency for the electrolysis process is 75% and the results are expressed with a potential map of the country, organized by counties, obtaining an overall annual potential of 1.110 1012 kg H2/ year for 2010. From this revision, is clear that methodology used to calculate the production potential of H2 by electrolysis, has the following characteristics: a. the use of potential maps of the renewable resources, generated thought different models
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with data from weather stations or satellite measurements, as input variables. b. The use of capacities and efficiencies factors to calculate the usable renewable energy, considering the available area for siting the devices for energetic conversion. c. The H2 amount that could be obtained is calculated accounting the efficiency of the electrolysis process and the availability of H2 production plant. Finally, the potential of H2 production for Latin American countries has been treated very little, studies are for specific regions of a country and for different purposes, which is not exactly use in the rural sector, whose population in a significant percentage lacks permanent energy service. The aim of this work is to contribute to both.
Table 2 e Comparison between renewable energy potentials of several countries [13]. Country
Solar potential (TWh/year)
Wind Potentiala (km2)
Argentina Bolivia Colombia Ecuador Guyana Mexico Peru Suriname Venezuela
7853.43 3220.15 2889.94 606.28 575.82 6469.15 3576.84 402.46 2586.86
418,022.00 26,611.00 57,996.00 229,084.00 N.A. 38,687.00 671,212.00 N.A. 10,950.00
a
Renewables energies in Venezuela Venezuela exhibits a great potential of RE in their different types, as indicated in Table 1. However, its development in the country is negligible, largely due to Venezuela also has large reserves of fossil fuels, especially oil, considered the largest in the world, and whose intensive operation for over 60 years, have shaped the energy sector, the country economy and even the Venezuelan society itself. Additional data for gross RE potential for Venezuela is presented by the NREL [13] and predicts 258,686 TW/year of potential for solar energy and estimates winds Class 3e7 with an area of 10,950 km2, a brief comparison between RE potentials of the countries within the region is shown in Table 2. It can be noticed that Venezuela has a solar potential similar to other nearby countries but its wind potential is very low due to geographical restrictions related to the coastal mountain range. Also, are available more accurate estimations of the solar and wind potentials [14,15], in form of potential maps, as shown in Fig. 1, which have been made from satellite measurements of average annual values of wind speed and insolation, respectively, corresponding to grids of 1 of longitude and latitude, setting a two-dimensional matrix located between 73 and 60 west longitude and between 12 and 1 north latitude, Fig. 2. These values are the basis for the calculation of potential production of H2 in Venezuela. In harnessing the RE, the Venezuelan government has been pushing several actions to promote and develop them, and the most important are: the construction of two wind
Table 1 e Renewable energy potential in Venezuela [8]. Source Mini-hydro Bioenergy Solar energy Wind energy Geothermal energy Others RE Large scale hydro
Specifications
Potential (GW)
Until 50 MW/utility Firewood, plantings, waste 15% conversion, 1% NTa, 0.3 MPb 3% conversion, 4% NT 2.5 NT Oceanic, hybrid
4.5 11.7 157.2 48.9 5.2 18.36 63.8 309.6
Total a b
National territory. Marine platform.
Winds class 3e7 at 50 m.
farms, located in the northwestern coastal area, with a total generating capacity of about 200 MW, right now in its initial operation, generating about 25 MW that are delivered to the electric grid [16], Regarding the solar photovoltaic (PV), the program “Sembrando Luz”, designed to provide permanent and efficient energy services to the rural and isolated populations that are not connected to the traditional power grid, had installed for 2012 around 3139 systems, with a total power of 2.5 MW supplying more than 257 thousand residents of 1020 rural communities [17]. Other types of RE, there are only small initiatives with no effect on the energy balance of the country.
The hydrogen market in Venezuela Hydrogen production The overall H2 produced in Venezuela, in 2010, reached 4850 MNm3 H2 [16], is produced via natural gas reformed, and is captive class, because it is fully consumed where it is generated. There is currently a deficit of H2 with chemical purposes that is estimated to rise with the increase of oil activity in the Faja del Orinoco and materialize expansions in petrochemical plants, according to PDVSA's development plans in the medium term [18].
Hydrogen consumption The H2 produced “in situ” is used as an input in the process of: a. Improvement of heavy oil, in order to obtain a synthetic oil, syncrude, with a higher commercial value, b. hydrogenation in the production of fuels derived from petroleum, and c. Petrochemical processes, especially for the production of ammonia [17]. If the H2 from renewable sources is used as a vector to satisfy the energy needs of the rural sector, the required amount is obtained by considering the energy consumption per capita in this sector, that arises to 191 kWh/year and the number of people to provide energy reaches 828,000 hab [19]. Then, assuming a 75% efficiency in the conversion in the electrolysis process respect to the higher heating value (HHV), the amount of H2 required is: CH2 ¼
CPC NH FCE
(1)
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Fig. 1 e Wind map (Left). Insolation map (Right).
CH2
kWh 191 year ð828; 000 habÞ hab kg H2 ¼ 3012342:86 ¼ year kWh 52:5 kg H2
(2)
Hydrogen production in Venezuela from RE General considerations This study considers as primary renewable sources for H2 production the solar direct energy, and indirect solar classified in: small hydro and wind, all usable with great potential in Venezuela [12,13]. In every case, H2 is produced by electrolysis of water with electricity generated from the selected RE,
(Fig. 3). It is clear that the HHV energy is used as a basis for calculation, with an overall efficiency of 75%, which includes the requirements of the electrolyzer and auxiliary equipment, and losses of the electrolytic system [2]. Moreover, in determining the land area available for harnessing the potential of RE, certain restrictions are taken considered, such as: a. Areas under Special Administration Regime (ABRAE, for its acronym in Spanish), defined as protected areas, covering an area equivalent to 46% of the land surface [20], including national parks and recreational, natural monuments, biosphere reserves and wildlife. b. Urban areas, obtained from distribution maps of urban populations are also excluded [21], and whose occupancy rate is taken into account in the grid that corresponds to the geopolitical distribution of these settlements.
Fig. 2 e Bidimensional grid used for the potential estimation of H2.
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Fig. 3 e Routes for the production of electrolytic hydrogen from some RE.
Hydrogen production
power. Equation (5) expresses the instantaneous power produced by a PV system:
In this case, the SESH basically consists in the coupling a PV power generation, wind and mini-hydroelectric system with an electrolytic system. Although its development and widespread use involves overcoming several technological and economic challenges, is one of the most promising routes for the production of renewable H2 [22,23]. On the other hand, considering that this is a potential estimation study, it is assumed that all the energy produced by renewable means will be used in the transformation process to H2. The possible routes for the production are shown in Fig. 3.
Establishment of usable areas To obtain the potential of solar photovoltaic and wind energy, primary information is taken from NASA [24], which consists of representative values of certain meteorological variables and corresponding to the two-dimensional mesh shown in Fig. 2 in which each of the 89 squares has an area of 12,100 km2. Taking into account that the procedure for determining the H2 production is the same for all grid cells that include the Venezuelan territory, as an illustration of the calculation for one square is presented, the number 34, selected because exhibits an insolation value very close the national average. The useful area per grid as a function of the grid area (AU), the ABRAE and the factor of available area (fA,D) is presented in Equation (3). AU ¼ AC ABRAE fA;D
(3)
PPV ¼ GT AN;FV factiv hcell hinv hother
(5)
where GT is the actual total radiation, Npanel the number of PV panels, AN,FV is the net superficial area with PV panels, factiv is the fraction of superficial area with active solar cells, hcell is the conversion efficiency of the PV module, hinv is the conversion efficiency of the DCeAC inverter and the parameter hother is proposed by CEC [26] as shown in Equation (6), where hother corresponds to the deviation of standard condition of test, htemp is the reduction factor for temperature, hloss is the reduction factor for electrical losses and hdirt is the reduction factor for dirt. hother ¼ hstd htemp hloss hdirt
(6)
Also, the annual average insolation over a daily basis as a function of GT(i) is: P8760 hr Fdaily ¼
GTðiÞ Dti 365 day
i¼1
(7)
From Equations (5), (6) and (7) and considering that Dti corresponds to a step of 1 h, the annual energy by PV is presented in the Equation (8): EPV;annual;C ¼ ð365 dayÞFdaily AN;FV factiv hcell hinv hstd htemp hloss hdirt
The net area of the grid (AN,C) is obtained from Equation (4), considering the population factor (fP):
The parameters associated with the production of solar PV to any grid are presented in Table 4, and specifically to the grid 34, from the Equation (8):
AN;C ¼ AU 1 fP
EPV;annual;C ¼ 1:515 1010 kWh=year
(4)
The influencing parameters in the calculation of (AN,C) are shown in Table 3.
PV model The proposed model uses a modification of the simple model of EnergyPlus Engineering Reference [25], in which the radiation incident on the PV panel is multiplied by several factors for efficiency parameters that adjust the maximum usable
Wind model This alternative for producing renewable H2 has attracted considerable interest, particularly in the case of hybrid
Table 4 e Parameters associated with the production of solar PV [24,26,27]. Parameter
Value
Fdaily ðkWh=m dayÞ AN;FV ¼ AN;C ðkm2 Þ factiv hcell hinv hstd htemp hloss hdirt 2
Table 3 e Parameters influencing the selection of usable area. Parameter AC (km2) ABRAE fA,D fP
Value 12,100 54% 1% variable
5.55 65.34 86.5% 20.8% 90% 95% 90% 95% 93%
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systems, in conjunction with PV and Solar Thermal systems [22]. For the calculation of production H2 potential, are taken into account only those two-dimensional mesh grids with winds of Class 2 or higher, i.e., winds with a speed equal to or greater than 4.4 m/sec, considered economically viable for generating electricity with current technology or for it develop in the short term [2], that imply consider the 20% of the squares of the mesh. To predict the power output of the wind system, a simplified model shown in Equation (9) is used, a reference performance curve of a commercial wind turbine for low speed is selected [28], which is shown in Fig. 4, and then the maximum power ðPaeroðvwind Þ Þ as a function of wind speed is directly obtained. Also is considered the efficiency of a DCeAC inverter hinv and the corresponding electrical losses factor hloss. Pwind ¼ Paeroðvwind Þ hinv hloss
8760 Xhr
Ewind;annual;C ¼ 3:363 108
kWh year
(8)
The annual average wind energy captured by each grid ðEwind;annual;C Þ, is calculated from Paeroðvwind Þ as a function of average annual wind speed obtained from NASA [19], the number of wind turbines in the park (Nturb) and the effectiveness factor of the array farr, as shown in Equation (10). Ewind;annual;C ¼ Nturb farr
Fig. 5 e Selected arrangement for the wind model.
PwindðiÞ Dti
(9)
i¼1
Due to the fluid dynamic interference, wind farms typically produce less energy than the sum of these wind turbines placed isolated, such the location of wind turbines should be optimized depending on the characteristics of wind and terrain. . Performed studies have found that a separation of turbines 8e10 rotor diameters in the prevailing wind direction and 5D in the perpendicular direction results in energy losses to lower 10% [29,30]. With the intention of consider an arrangement that minimizes the failures, the configuration in Fig. 5 is proposed. For the selected arrangement, the equivalent area of each turbine is equivalent to5D 10D, equivalent to 605,000 m2, with reference to the net area of the grid (AN,C), Then should be placed in it about 81 turbines. Considering the selected wind turbine, the average wind speed in the grid example for the wind case (No. 4) is 6.18 m/s, the efficiency factors are similar to those presented in the PV case and the photovoltaic efficiency factor is 90%, the total annual wind energy of that grid, according to Equation (10) is:
Mini-hydro model To obtain the mini hydro potential, the information in Table 1 is taken, in which the production capacity for this item (PMH) is 4.5 GW, and considering that this resource can be continuously exploited, can be said that the annual mini hydropower nationwide is given by Equation (12): EMH;annual ¼ PMH ð8760 hrÞ
(10)
Resulting: EMH ¼ 3:942 1010
kWh year
Total renewable energy To obtain the total annual renewable energy (ET) that can potentially be used for production of H2, must be added the energy produced in each grid for PV, wind and mini-hydro power, according to Equation (11). ET ¼ ET;PV þ ET;wind þ ET;MH
ET;FV ¼
89 X
EFV;annual;C ðiÞ
i¼1
ET;eolica ¼
89 X
(11)
Ewind;annual;C ðiÞ
i¼1
Then, the total renewable energy for every source is: ET ¼ 1:146 1012 kWh=year ET;PV ¼ 1:088 1012 kWh=year ET;wind ¼ 1:825 1010 kWh=year ET;MH ¼ 3:942 1010 kWh=year
Calculation of amount of hydrogen to obtain For the calculation of H2 to obtain, the Equation (11) is used, in which is required the total renewable energy (ET) and energy conversion factor for H2 (FCE), in which an availability factor (fav) representing the period devoted to maintenance and the value of 0.95 has been reported for the case of H2 production plants by electrolysis [5,19] mH2 ¼
Fig. 4 e Power curve for the selected wind turbine (P ¼ 2000 kW D ¼ 110 m) [23].
E fav FCE
(12)
Finally the annual amount of H2 for each renewable source and the total are presented in Table 5. A summary of the potential reported in the literature and obtained for Venezuela is shown in Table 6, although it is not
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Table 5 e Results by type of renewable energy and overall. RE type
Production H2 (kg/year)
PV Wind Minihydro Total
Contribution (%)
10
1.968 10 3.303 108 7.134 108 2.073 £ 1010
94.96 1.59 3.45 100
h
Table 6 e Reported H2 production potentials. Country, region rdoba Argentina, Co Brazil, Ceara Chile, Patagonia Ecuador, Azuay USA Venezuela
Potential (kg H2/year) 6
37.34 10 5.06 106 3.8 105 10.8 106 1.110 1015 2.073 1010
Year 2010 2010 2010 2014 2005 2014
possible a fair comparison between them, correspond to different situations and conditions, if it is useful for an understanding of the order of magnitude production potential of H2 in Venezuela, compared to other countries in Latin America.
Conclusions It have been determined the total potential production of H2 in Venezuela by water electrolysis with electricity from renewable sources, considering solar PV, wind and mini-hydro energy, all with large potential in Venezuela. Of these, the first is the largest contribution mainly due to an exploitable potential distributed throughout the country, which does not happen in the remaining two. The total H2 produced completely covers the electric energy requirements of unattended rural population, the remainder can be used as input in different chemical processes. These results represent a starting point for more elaborate and exhaustive studies, including economic, social and environmental aspects involved in intensive development of H2 as an energy vector in Venezuela.
Acknowledgments n of the Universidad Nacional To Decanato de Investigacio chira for the financial support for the Experimental del Ta realization of this paper.
Nomenclature Variables A area cuad square grid D diameter E energy f factor FCE energy conversion factor
G m N P C F
solar radiation mass number power consumption insolation efficiency
Sub-indexes A area activ active arr array av availability C square grid cell PV cell D available PV photovoltaic H habitant inv inverter MH mini-hydro N net P population PC per capita loss electric loss std standard T total temp temperature turb turbine U useful
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