Efficiencies of hydrogen storage systems onboard fuel cell vehicles

Efficiencies of hydrogen storage systems onboard fuel cell vehicles

Solar Energy 78 (2005) 687–694 www.elsevier.com/locate/solener Efficiencies of hydrogen storage systems onboard fuel cell vehicles Vinay Ananthachar, J...

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Solar Energy 78 (2005) 687–694 www.elsevier.com/locate/solener

Efficiencies of hydrogen storage systems onboard fuel cell vehicles Vinay Ananthachar, John J. Duffy

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Energy Engineering Program, University of Massachusetts Lowell, 1 University Avenue, Lowell, MA 01854, USA Received 30 June 2003; received in revised form 27 February 2004; accepted 27 February 2004 Available online 17 March 2004 Communicated by: Associate Editor A.T. Raissi

Abstract Energy efficiency, vehicle weight, driving range, and fuel economy are compared among fuel cell vehicles (FCV) with different types of fuel storage and battery-powered electric vehicles. Three options for onboard fuel storage are examined and compared in order to evaluate the most energy efficient option of storing fuel in fuel cell vehicles: compressed hydrogen gas storage, metal hydride storage, and onboard reformer of methanol. Solar energy is considered the primary source for fair comparison of efficiencies for true zero emission vehicles. Component efficiencies are from the literature. The battery powered electric vehicle has the highest efficiency of conversion from solar energy for a driving range of 300 miles. Among the fuel cell vehicles, the most efficient is the vehicle with onboard compressed hydrogen storage. The compressed gas FCV is also the leader in four other categories: vehicle weight for a given range, driving range for a given weight, efficiency starting with fossil fuels, and miles per gallon equivalent (about equal to a hybrid electric) on urban and highway driving cycles. Ó 2004 Published by Elsevier Ltd. Keywords: Solar energy; Fuel cell vehicles; Hydrogen storage; Energy efficiency

1. Introduction Fuel cell vehicles running on pure hydrogen are zero emission vehicles (ZEV), hence these vehicles can be a long-term solution to the environmental problems associated with transportation. The hydrogen can be stored directly or produced onboard the vehicle by reforming methanol or hydrocarbon fuels derived from gasoline or diesel. The vehicle design is simpler with a direct hydrogen storage system, but a refueling infrastructure would need to be developed. The storage system potentially has a large influence on the driving performances.

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Corresponding author. Tel.: +1-978-934-2968; fax: +1-978934-3048. E-mail address: john_duff[email protected] (J.J. Duffy). 0038-092X/$ - see front matter Ó 2004 Published by Elsevier Ltd. doi:10.1016/j.solener.2004.02.008

In this study we compared energy efficiencies of different types of onboard hydrogen storage systems in a fuel cell vehicle. A reformer system in a fuel cell vehicle and a battery storage system in an electric vehicle were also examined here. We compared three leading options for fuel storage onboard a fuel cell vehicle: (a) compressed hydrogen gas storage, (b) metal hydride storage and (c) onboard methanol reformer system. It is assumed that these storage systems for a fuel cell vehicle have to provide a range of around 300 miles on the Federal Driving Test to make them acceptable to the public. Energy for the fuel cell vehicle can be produced from solar power or any other conventional power source. In this study the focus of primary energy source for hydrogen production is solar power. The efficiency with which the energy is used is important in many ways; the efficiency of hydrogen use affects the fuel cost per mile;

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Nomenclature d E0

specific weight of fuel and fuel tanks per energy equivalent to 1 l gasoline fuel economy at the base vehicle weight (@ W ¼ 1221 kg and DW ¼ 0 without air resistance)

the efficiency of energy use also determines the total emissions of greenhouse gases; and the overall efficiency of converting solar energy into energy at the wheels determines photovoltaic power or land requirement and cost of infrastructures for solar-hydrogen production. In the coming sections we will be discussing basics about fuel cell vehicle, types of fuel cells and hydrogen storage options. 1.1. Fuel cell vehicle A fuel cell vehicle is an electric-drive vehicle that uses a fuel cell system in place of a rechargeable storage battery as illustrated in the Fig. 1. The fuel cell system provides electricity to the electric drive-train. The electric drive-train consists of three main parts. They are an electric motor, an electronics package consisting of motor controller, dc-to-ac inverter and dc-to-dc converter and a transmission. The transmission transmits power from the motor to the wheels.

Fig. 1. Schematic of fuel cell vehicle.

HHV LHV L V DW

higher heating value lower heating value driving range in miles speed of the vehicle (30, 40, 50 and 60 mph) weight of fuel + fuel tank in kg

A fuel cell converts chemical energy in hydrogen and oxygen directly into electrical energy. It is similar to the rechargeable battery. Fuel cells and batteries are electrochemical devices; the main difference between them is that in a fuel cell, the electricity producing reactants are continually supplied from an external source, such as the air and a hydrogen storage tank, whereas in a battery, the electricity producing reactants are regenerated in the battery by the recharging process. There are five important types of fuel cells; they are (1) proton exchange membrane (2) alkaline fuel cell (3) phosphoric acid fuel cell (4) solid oxide fuel cell and (5) molten carbonate fuel cell. The proton exchange membrane fuel cell (PEM) is the most suitable fuel cell for automobile applications. These cells operate at relatively low temperatures of about 80 °C, have high power density, and can vary their output quickly to meet shifts in power demand. 1.2. Hydrogen storage system Hydrogen, the most abundant element in the universe, has great potential as an energy carrier. Hydrogen can be easily generated from renewable energy sources for example PV, wind, or hydro with electrolyzers. There are different types of hydrogen storage options. (1) Compressed H2 gas storage system: the least complex method of storing pure hydrogen is as a compressed gas in a high-pressure cylinder. The gas can be stored at an ambient temperature, thereby avoiding costly and bulky thermal insulation; and it is easy to pump the gas, i.e., merely opening a valve allows removal of the gas from the system. (2) Metal hydride storage: certain materials absorb hydrogen under moderate pressure (less than 1000 psia) at low temperatures, forming reversible hydrogen compounds called hydrides. The storage tank contains powdered metals that absorb hydrogen and release heat when the hydrogen is forced into the tank under pressure. The hydrogen is released from the compound when the pressure is reduced and heat is applied. (3) Liquid hydrogen storage: hydrogen can be stored as a liquid at extremely low temperatures ()253 °C) in highly insulated vacuum containers. (4) Carbon adsorption: this type of storage system is in the research stage. Here the hydrogen is forced into a refrigerated

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tank under pressure where it adheres to activated carbon. The carbon material is a highly porous material that absorbs hydrogen efficiently. (5) Sponge iron: hydrogen can be produced onboard a vehicle by oxidation of iron using steam (IEEE spectrum, 1995). In this reaction the powered iron stored in the tank is combined with oxygen in the steam to form iron oxide (rust) and liberates hydrogen in the process. Once the iron is completely converted to iron oxide in the vehicle, either the entire tank is replaced or the iron oxide is removed from the tank and replaced with fresh iron. In either case it takes a few minutes to replace.

2. Hydrogen storage onboard a FCV The development of adequate on-board energy storage is a major economic and technological barrier to introducing hydrogen vehicles. In this study we compared three leading options for fuel storage onboard a fuel cell vehicle: (a) compressed hydrogen gas storage, (b) metal hydride storage and (c) onboard methanol reformer system.

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2.1. Compressed hydrogen gas storage system The least complex method of storing pure hydrogen is as a compressed gas in a high-pressure cylinder. Energy for the fuel cell vehicle can be produced from solar power, biomass or any other means, but here we will be considering energy from solar power. It is important to consider energy efficiency at each stage because the efficiency of the hydrogen or electricity use affects the fuel cost per mile, land requirement; also the efficiency of energy use often determines total emissions of greenhouse gases, but in this case the tail pipe emissions would be zero. Table 1 shows the overall and stage-by-stage energy efficiencies of solar energy–hydrogen production anduse (FCV) pathways. Hydrogen production using an electrolyzer is considered in this study and the conversion efficiency of the electrolyzer is around 68%. For compressing the hydrogen gas with the electrolyzer to the required high pressure, 7–10% extra energy is used (Aurora, 2003). In the case of a hydrogen storage system, the energy stored in 6.8 kg of the compressed hydrogen is 965.6 MJ (higher heating value (HHV) of H2 ¼ 142 MJ/kg). The energy available at the wheels is

Table 1 Comparison of solar-to-wheel energy efficienciesa FCV with compressed H2 storage

Sunlight

PV array electricity (15%)b

Power cond. (85%)c

1 –

0.15 1

Battery powered electric vehicle

Sunlight

FCV with metal-hydride storage

Sunlight

FCV with onboard reformer

1 –

1 – Sunlight

1 – a

Fuel cell (46%)f

Drive-train (95%)f

Energy efficiency

0.128 0.85

H2 prod. and compression (63%)d; e 0.0803 0.536

0.0369 0.246

0.0351 0.234

3.5% 23%

PV array (15%) 0.15 1

Power cond. (85%) 0.128 0.85

DC trans (92%)c 0.117 0.782

Recharger and battery (81%)c 0.095 0.63

Drive-train (95%) 0.090 0.60

Energy efficiency 9% 60%

PV array (15%) 0.15 1

Power cond. (85%) 0.128 0.85

H2 prod. (68%)d; e 0.0867 0.578

M–H storage (92%)g 0.0798 0.532

Fuel cell (46%) 0.0367 0.245

Drive-train (95%) 0.0349 0.232

Energy efficiency 3.5% 23%

Biomass photosynthesis (0.3%)c 0.003 1

Methanol prod. (63%)f

Methanol transportation (98%)c

Onboard reformer (62%)h

Fuel cell (39%)d

Drive-train (95%)

Energy efficiency

0.00189 0.63

0.00185 0.617

0.00115 0.383

0.00045 0.149

0.000425 0.142

0.043% 14%

A driving range of 300 miles for a midsize car is assumed for the storage options examined in Table 1. From Ogden and Nitsch (1993). c From DeLuchi and Ogden (1993). d From Ananthachar (2002). e From Aurora (2003). f From Ahman (2001). g Derived from estimates in James et al. (1996). h From Ogden et al. (1999). b

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337.6 MJ of the fuel cell vehicle assuming the conversion efficiencies of the drive-train is 76% and the fuel cell is 46% (Ahman, 2001). The path consists of only those stages that consume either the primary energy or the intermediate fuel (electricity or hydrogen). The efficiency of the power-train accounts for energy recovered from regenerative braking over the entire drive cycle (DeLuchi and Ogden, 1993). The overall energy efficiency of a fuel cell vehicle running on compressed hydrogen gas storage system depends on the fuel pathway. Hydrogen gas can be produced efficiently from a variety of widely available renewable sources, using such methods as water electrolysis powered by solar electricity and gasification of renewably grown biomass.

anode feed gas (Ogden et al., 1995). In the case of onboard steam reforming methanol, the hydrogen content is about 75% by volume, which reduces the efficiency of the fuel cells. The peak power output of the fuel cells is highest on pure hydrogen. The primary energy efficiency for fuel cell vehicles using onboard methanol reformer where methanol is derived from cellulosic biomass is shown in the Table 1. The primary energy efficiency is shown from solar energy to wheels of the vehicle. The conversion efficiency of biomass to methanol is 63%. The energy required to deliver the methanol is relatively low: around 2% of the total energy is required for truck transport from production to the refueling site (Ahman, 2001). 2.4. Battery powered electric vehicle

2.2. Metal hydride storage system Hydrogen can be stored directly at very high pressures in a pressure vessel or produced onboard the vehicle by reforming methanol or hydrocarbon fuels derived from gasoline or diesel. The other type of direct onboard hydrogen storage is in the form of metal hydrides. In this section we will be going through the energy efficiency calculations for a fuel cell vehicle using solar energy as the primary energy source and also study the metal hydride storage system. According to the study conducted by DTI (James et al., 1996) in the metal hydride storage charging process at constant temperature, the hydrogen initially rapidly diffuses into the metal particle interstices and the pressure rises, indicating physical adsorption. Subsequently, the hydrogen reacts with the metal alloy at a slower rate forming the metal hydride, with a slowly increasing pressure. After the reaction is completed, the pressure again increases, indicating small additional pressurized gas storage in the void space. Heavy metal hydride such as FeTiH1:9 is assumed for the energy calculations in this study. The weight percent is 1.8% per hydride and the heat required for desorption is 12 MJ/kg. The release temperature for FeTiH1:9 is 20–50 °C at 3 atm; this energy can be provided by the excess heat of the fuel cell system. 2.3. Onboard reformer system Hydrogen can be stored directly as explained in the previous sections or it can be produced onboard the vehicle by steam reforming of methanol. Direct hydrogen storage results in a simpler vehicle design but a more complex refueling infrastructure. Onboard reforming results in the opposite. The methanol fuel cell vehicle has a methanol storage tank, a steam reformer to produce hydrogen gas and rest of the components are same as hydrogen powered fuel cell vehicle as shown in the Fig. 1. The output of the PEM fuel cells in the fuel cell vehicle varies with the concentration of hydrogen in the

The energy efficiencies of the battery powered electric vehicle are explored in this section. The primary energy source is solar energy and it is converted to electricity using a photovoltaic array. The energy efficiency of the battery electric vehicle from sun-to-wheel and wellto-wheel and the energy required at each stage of the fuel pathway for a vehicle range of 300 miles is shown in Table 1. A Valve-Regulated Lead Acid (VRLA) battery system is considered in this study. The battery system in an electric vehicle has to store up to 30 kW h to afford the vehicle the acceptable range. The recharging and the battery efficiency do not include the use of any energy to heat a high-temperature battery (DeLuchi and Ogden, 1993) for the battery only storage system. The primary energy efficiency for an energy carrier based on renewable resources (i.e. in our case photovoltaic electricity) used is given in Table 1. As we can observe from the table, the energy conversion at each stage is higher as compared to the fuel pathway of fuel cell vehicle using hydrogen derived from solar power. One of the advantages of the photovoltaic power is that it is distributed and can be used near the load. This PV efficiency is no different than the previous cases and is much higher than the biomass conversion efficiency. When the primary energy source is fossil fuel (coal), the overall energy efficiency is much higher than the solar-to-wheel efficiency. The batteries have highest potential for primary energy efficiency from solar energy, but the main drawbacks are long recharging time, low specific energy of the batteries that reduces the overall electric vehicle range for the same vehicle weight.

3. Comparisons of fuel cell vehicles 3.1. Solar-to-wheel energy efficiencies Three leading options for fuel storage onboard fuel cell vehicles and a battery powered electric vehicle are

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compared, based on the energy efficiency, weight tradeoffs, ‘‘fuel’’ economy, and the driving range of the alternative vehicles. The calculated energy efficiencies of fuel cell vehicles with various options for hydrogen storage and of a battery powered electric vehicle are shown in Fig. 2. The highest efficiency is achieved for the battery-powered electric vehicle. The energy efficiency from the photovoltaic array (electricity) to the wheels of the vehicle is highest for battery powered electric vehicle (60%) and lowest for the fuel cell vehicle with onboard methanol reformer system (14%) (Fig. 3). When we consider regenerative braking in the drive-train system, some of the energy consumed can be saved in the fuel pathway, around 25% of the braking energy is regenerated and stored in the batteries (Ahman, 2001). Due to regenerative braking the overall fuel efficiency is increased in all the storage options. In the case of an onboard reformer system the energy efficiency is based on methanol as the input energy. When we compare the different power-

Energy efficiencies (%)

Solar-to-Wheel energy efficiency comparison of alternative storage systems in FCV/EVs 9

10.0 8.0 6.0

3.5

3.5 0.043

2.0 FCV with FCV with metalcompressed H2 hydride storage storage

FCV with onboard methanol reformer

Battery Electric vehicle

Fig. 2. Solar-to-wheel energy efficiency comparison.

Energy efficiency comparison of different storage options

3.2. Well-to-wheel energy efficiencies The well-to-wheel energy efficiencies, when the primary energy source is fossil fuel (e.g. coal), are also of interest. Hydrogen gas can be produced in a large, centralized steam reforming of natural gas and distributed via gas pipelines. According to Ogden et al. (1999) large-scale production of hydrogen would lower production costs. The efficiency of producing hydrogen from natural gas is approximately 85%. The energy efficiency from wellto-wheel in a compressed hydrogen gas FCV is 33%, which includes the losses in drive-train and the fuel cell stack. The efficiency from coal power to the electricity is assumed to be 40% (Ahman, 2001) and the well-to-wheel energy efficiency starting with coal in a battery powered electric vehicle is 24%. If natural gas is used in producing electricity then the conversion efficiency would be 55% (Ahman, 2001) and the well-to-wheel efficiency of the battery powered electric vehicle would increase to 33%.

The mass of the vehicle varies with the type of the vehicle. The calculated weight of the individual components of the fuel cell vehicle and the battery powered electric vehicles are shown in the Fig. 4. Vehicles with onboard fuel processor and battery powered electric vehicle are heavier than the direct hydrogen fuel cell vehicle for several reasons. First, in an onboard fuel reformer vehicle, the fuel processor adds weight and in the battery powered electric vehicle, the battery contributes most of the weight to the vehicle. Second, due to

60

70.0

Vehicle weight

60.0 50.0 40.0 30.0

23

Weight (kg)

Energy efficiencies (%)

trains from the primary energy source, i.e., sunlight to the wheels of the vehicle, the well-to-wheel efficiency of the battery powered electric vehicle is highest and the lowest is again the reformer system. The low value of solar-to-wheel energy efficiency of the onboard reformer fuel cell vehicle is due to the low conversion efficiency of the photosynthesis process (0.3%).

3.3. Vehicle weight and driving range

4.0

0.0

23 14

20.0 10.0 0.0

691

FCV with compressed storage

FCV with metalH2 hydride storage

FCV with onboard methanol reformer

Battery Electric vehicle

2000 1800 1600 1400 1200 1000 800 600 400 200 0

592 80

265

1221

1221

Compressed H2 gas

Onboard reformer system

Basic vehicle weight (kg)

Fig. 3. Comparison of energy efficiency of different leading storage options.

1221

Metal hydride storage

800

1021

Battery

fuel+fuel tank (kg)

Fig. 4. Vehicle weight comparison.

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the low energy efficiency of the fuel cell/fuel processor system as compared to a pure hydrogen system, a larger fuel cell is needed for same power output. Assumptions for the weight comparison are (Ogden et al., 1995): (1) Glider weight ¼ 600 kg (includes body & chassis, motor/controller, accessories and etc). (2) Peak power battery ¼ 285 kg (VRLA battery of 10 kW h, specific energy ¼ 35 W h/kg) and (3) Cargo ¼ 136 kg. The basic weight of the vehicle excluding fuel and fuel tank is around 1221 kg. Eq. (1) from Yamane and Furuhama (1998) is used to relate the range, weight, and fuel economy: L¼

E0 W DW ; 2 ðW þ DW Þ þ 0:047V d

ð1Þ

where L is the driving range in miles; DW the weight of fuel + fuel tank in kg; V the speed of the vehicle (30, 40, 50 and 60 mph); d the specific weight of fuel and fuel tanks per energy equivalent to 1 l gasoline; E0 the fuel economy at the base vehicle weight (@W ¼ 1221 kg and DW ¼ 0 without air resistance). The driving range per refueling depends on the weight of fuel & fuel tank and it is also largely affected by the storage methods. The dashed lines represent the different speeds of the vehicle (30, 40, 50 and 60 mph). Fig. 5 shows that the driving range per refueling does

not increase with DW as a linear function and is affected largely by the storage methods. A battery powered electric vehicle with DW ¼ 300 kg, which may be the maximum DW for practical use, can travel only 100 miles. When the driving range of 300 miles is required, the battery-powered vehicle has to carry more than 800 kg of ‘‘fuel’’. This result indicates the battery powered vehicle is much inferior in the driving range as compared to the fuel cell vehicles. In case of a fuel cell vehicle with onboard methanol reformer storage system, the DW ¼ 350 kg is required for a driving range of 300 miles. Even in case of a fuel cell vehicle with metal hydride storage, for 300 miles driving range the weight of fuel and fuel tank would be more than 500 kg. It is found that vehicles with these storage methods have to carry much heavier fuel and fuel tank than 300 kg to obtain the driving range of around 300 miles. On the other hand, in the case of a fuel cell vehicle with high pressure container at 5000 psia, DW ¼ 100 kg will give a driving range of 300 miles. 3.4. Fuel economy of the vehicles Table 2 shows the vehicle fuel economy on urban driving cycle and highway driving cycle used by the EPA (US Environmental Protection Agency, 2003) to certify that vehicles meet the Federal emissions and fuel economy standards. To generate these two fuel economy estimates, different tests are used to represent typical driving cycles in a city and a highway by the EPA. The fuel ‘‘economy’’ is highest for a battery powered electric vehicle like the two seater Ford’s Th!nk electric vehicle as compared to the hybrid and compressed hydrogen stored fuel cell vehicles (Honda FCX). The fuel economy of battery powered electric vehicle is based on electricity from an outlet (electrical grid). The higher fuel economy of the battery powered electric vehicle is due to the direct use of the electricity from the outlet without much loss in energy conversion. In case of the fuel cell vehicle the lower fuel economy is due to the losses in energy conversion in the fuel cell stack and losses in the drive-train. Table 2 Fuel economy of vehicle Type of vehicle

Citya

Highwaya

(mpg) gasoline equivalent

(mpg) gasoline equivalent

2001 Ford Th!nk Electric 106 vehicle 2004 Honda FCX (miles/ 51 kg  mpg) 2004 Honda Civic hybrid 48 2004 Honda Insight 57 2004 Toyota Prius 60 Fig. 5. Effect of weight on driving range.

a

From www.fueleconomy.gov.

83 46 47 56 51

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The fuel economy of a direct hydrogen fuel cell vehicle is roughly equal to the commercially available Honda hybrid and Toyota Prius electric vehicles.

4. Summary and conclusions In this study, energy efficiency, vehicle weight, driving range, and fuel economy are compared among battery powered electric vehicles and fuel cell vehicles (FCV) with different types of fuel storage. When we compare all the fuel pathways starting from a common primary energy source (sunlight), the battery powered electric vehicle has the highest potential for primary energy efficiency as compared to compressed hydrogen gas, metal hydride and onboard reformer systems. Among the fuel cell vehicles the compressed hydrogen gas stored FCV is the most energy efficient vehicle. Vehicles with onboard steam reforming of methanol, where methanol is derived from biomass, have the lowest primary energy conversion; this is due to the photosynthesis process, which has very low energy conversion efficiency. A constant driving range of around 300 miles was used in the calculation of the above energy efficiencies. When one compares efficiencies starting with fossil fuel, the vehicle with compressed hydrogen gas tank storage at 33% is either slightly above or equal to the battery electric car depending on the source of fuel in the power plant producing electricity for the battery charging. Of course, efficiencies change with operating and weather conditions and a number of other variables. The estimated efficiencies here are intended to represent typical values. The compressed hydrogen gas tank storage system onboard a fuel cell vehicle is simpler in design, lighter weight, and more energy efficient than those with metalhydride storage, and methanol reformer system vehicles. The weight of the fuel cell vehicle with compressed hydrogen gas tank storage is much lower compared to other vehicles considered in this study for a driving range of around 300 miles. The driving range for a given weight of vehicle achieved in a fuel cell vehicle with compressed hydrogen gas storage system is better compared to the metal-hydride and onboard methanol reformer system. The battery powered electric vehicle has the lowest driving range for a fixed weight due to the weight of the batteries. The fuel economy (miles per gasoline equivalent of electricity) on a standard driving test of the battery powered electric vehicle appears better than the fuel cell vehicles because a battery has a better round trip efficiency than a fuel cell efficiency. But if one starts with a common source, like natural gas, the two are about equal in fuel economy. The fuel economies of the fuel cell vehicles are still better than any vehicle with an

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internal combustion engine, however. The compressed gas FCV has almost the same equivalent miles per gallon as the hybrid electric Honda Civic and Honda Insight on city and highway driving cycles. Hydrogen stored in high-pressure vessels could be the preferred storage type for fuel cell vehicles, for reasons of vehicle design, cost and efficiency, as well as environmental benefits. With renewable energy as a primary source of energy, the total greenhouse gas emissions in the fuel cycle can be reduced to essentially zero and also the tailpipe emissions of the vehicles would be zero. The vehicle design is simpler with direct hydrogen storage (compressed hydrogen gas or metal-hydride), but this approach requires developing a more complex refueling infrastructure. Initially the hydrogen gas can be produced in a small onsite solar-electrolysis facility and can serve a small number of fuel cell vehicles. As the demand increases, the size and number of the hydrogen production facilities can be increased. This approach reduces the requirement for an initial massive refueling infrastructure and investment. In the case of a battery powered electric vehicle, the electricity can be produced from a photovoltaic array in a small onsite charging facility and the electrical output can be directly utilized for charging the batteries, but the charging time can be around 7–8 h, which is a disadvantage. With the success of hydrogen technology, fuel cell vehicles and electric vehicles could be an economical and environmental friendly form of transportation in the near future. References Ahman, M., 2001. Primary energy efficiency of alternative powertrains in vehicles. Energy 26, 973–989. Ananthachar, V., 2002. Efficiencies of hydrogen storage system onboard fuel cell vehicles, Master’s thesis, University of Massachusetts Lowell. Aurora, P., 2003, Modeling and control of a solar hydrogen fuel cell system for remote applications, Master’s thesis, University of Massachusetts Lowell. DeLuchi, M.A., Ogden, J.M., 1993. Solar hydrogen fuel cell vehicles. Transportation Research A 27 (3), 255–275. IEEE Spectrum, May 1995. The search for better batteries, pp. 55–56. James, B.D., Baum, G.M., Lomax Jr., F.D., Thomas, C.E., Kuhn Jr., I.F. 1996. Comparison of onboard hydrogen storage for fuel cell vehicles, Task 4.2 Final Report under Subcontract 47-2-R31148 by Directed Technologies, Inc., 4001 North Fairfax Drive, Suite 775, Arlington, VA 22203. Ogden, J.M., Nitsch, J., 1993. Solar hydrogen, chapter 22 of Renewable energy: sources for fuels and electricity. Island press. Ogden, J.M., Steinbugler, M., Dennis, E., Kartha, S., Iwan, L., Andrew, J., 1995. Hydrogen Energy Systems Studies. Center for Energy and Environment Studies. Princeton University, NJ. Ogden, J.M., Steinbugler, M.M., Kreutz, T.G., 1999. A comparison of hydrogen, methanol and gasoline as fuels for fuel

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cell vehicles: implications for vehicle design and infrastructure development. Journal of Power Sources 79, 143–168. US Environmental Protection Agency, 2003. Available from .

Yamane, K., Furuhama, S., 1998. A study on the effect of the total weight of fuel and fuel tank on the driving performance of cars. International Journal of Hydrogen Energy 23 (9), 825–831.