August 2004 • NREL/CP-520-36401 

Solar Photovoltaic Hydrogen: 

The Technologies and Their 

Place in Our Roadmaps and 

Energy Economics 

L.L. Kazmerski 

National Renewable Energy Laboratory 

K. Broussard 

Southern University 

Prepared for the 19th European PV Solar Energy 

Conference and Exhibition 

Paris, France 

June 7–11, 2004 

National Renewable Energy Laboratory

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SOLAR PHOTOVOLTAIC HYDROGEN: 

THE TECHNOLOGIES AND THEIR PLACE IN OUR ROADMAPS AND ENERGY ECONOMICS 

Lawrence L. Kazmerski and Kara Broussard* 

National Renewable Energy Laboratory, Golden, Colorado 80401, USA 

*Research Intern from Southern University, Baton Rouge, Louisiana, USA 

Tel: (303) 384-6600; Fax: (303) 384-6601; e-mail: kaz@nrel.gov 

ABSTRACT: Future solar photovoltaics-hydrogen systems are discussed in terms of the evolving hydrogen econ­


omy. The focus is on distributed hydrogen, relying on the same distributed-energy strengths of solar-photovoltaic


electricity in the built environment. Solar-hydrogen residences/buildings, as well as solar parks, are presented. The 


economics, feasibility, and potential of these approaches are evaluated in terms of roadmap predictions on photovol­


taic and hydrogen pathways—and whether solar-hydrogen fit in these strategies and timeframes. Issues with the “hy­


drogen future” are considered, and alternatives to this hydrogen future are examined.


Keywords: solar hydrogen, system, roadmaps, electrolysis, photolysis


1. INTRODUCTION 

Solar electricity is real and on a path as a power of 

choice for world consumers [1,2]. Advances in photovol­ taic (PV) performance over the past 25 years—with crystalline silicon more than doubling in efficiency, thin films nearly quadrupling, and concentrator cells converting almost 40% of incident photon energy into electrical 

power—have been the foundation for credible electricity 

generation [2–4]. History has offered strong indicators for progress and reliability. Fifty years ago, one 2-cm2

 Si 

solar cell at Bell Telephone Laboratories broke the 5%­ efficiency mark—delivering a power of 5 mW. This last 

year, the industry shipped over 500 million cells having 2 an area of more than 6 billion cm —representing a power 

of nearly 0.75 GW [5]. That original cell still functions a half century later—and current module technology is 

warranted for 20–30 years. The versatility, clean and 

secure power, and scalability of this solar technology offers even more for the world energy portfolio— 

including perhaps serving as the perfect partner for our 

potential hydrogen prospects [6]. The major focus herein is to look at solar PV in this application—focusing on 

combining the distributed-energy delivery strengths of 

PV with a similar energy-distribution scheme for hydro­ gen and its related technologies to afford our future generations with 24-hour solar-hydrogen power. 

2. SOLAR HYDROGEN SCENARIOS 

When the United States rolled out its hydrogen vision 

in 2002 [7,8] and its strategy in 2003 [9], the source of 

the hydrogen was perceived primarily to be natural gas— 

an approach that hardly ignited the renewables community. Within a few months of the U.S. President’s an­ nouncements in his 2003 State of the Union Address, the 

developing natural gas shortage has precluded this source 

from being the primary one—and other technologies have come forward. Nuclear, wind, bioenergy, and solar 

have positioned themselves to serve as the energy resources to produce the required hydrogen [10–13]. Among these resources, solar possesses some special attributes that may make it the power of choice in the 

future. If one looks at the more than 14 TW total primary energy equivalent required currently worldwide—or the 

26–30 TW predicted to be consumed at the coming halfcentury point, only solar of the renewable resources could actually meet this total—and only nuclear from the 

nonrenewables [14]. Questions about PV-for-electricity 

and solar-for-hydrogen production land-area require­ ments, water use, electricity needs, and technology pro­ duction pathways/performances have been addressed— 

with no showstoppers identified on the horizon [15–17]. What limitations exist? 

As centralized facilities, both concentrating 

solar power (CSP) and nuclear provide clean-generation thermal roadmaps toward generating economical hydro­ gen [9]. Additionally, CSP, concentrating PV (CPV), 

and flat-plate PV can meet electricity prices that are needed for large- scale electrolysis. However, all these centralized approaches require long-distance delivery, 

which is difficult and potentially the most costly segment 

of the hydrogen energy system. 

Alternatives? Just as the distributed solar-PV system makes use of the economics of “electricity generation at 

point of use,” an alternative distributed hydrogen system 

links “production” and “delivery” at the point of use [16]—distributed solar electricity and distributed solar 

hydrogen. The recent U.S. National Academy study of 

hydrogen provided a partial look at this approach, as well 

[18]. This concept can be visualized in two distinct implementations. The first is at the individual residence or 

building level [9]. This concept expands on the zero- energy home with the inclusion of production, storage, 

and “in-property” distribution. The primary source of 

energy is the sun, with PV providing the electricity and with solar thermal providing for the building’s heating 

and cooling needs. In the longer term, this would be a 

hybrid electricity/thermal system integrated into the building structure. As the PV and solar thermal technologies advance, integration into the building structure 

will be essential in ensuring architectural integrity and 

desirability. But coincidentally, it will also maximize the use of the building’s skin. The solar electricity is used 

for (1) generating daytime electricity for the building, (2) 

providing power to the electrolyzer to produce the hydrogen (and oxygen) for the fuel cell and storage, and (3) 

supplying excess electricity to the grid. The stored hydrogen could even be used to fuel the “family Freedom 

Car,” in addition to providing the hydrogen for the fuel cell (24-hour power). Thus, this concept could fulfill the “zero-energy home” objective, but could also result in the 

“energy-plus” residence—providing more energy than it 

needs. The excess could be shared with the utility, as well as with neighbors. This situation extends into the second distributed 

PV/hydrogen concept: the solar hydrogen park (Fig. 1). 

In this approach, a number of residences, structures, and 

local community buildings share the solar-collection 

tasks to generate the necessary electricity—and share the hydrogen generation from a community “plant.” Thus, 

the stored hydrogen would feed their fuel cells for nighttime power, and community fueling stations are used for hydrogen-powered automobiles, vans, and trucks. 

Protected parking covers would also support PV (which 

would not only feed into the community power, but also be offered for electric or hybrid vehicles). Note that 

other smaller generation schemes could also be used, which could include concentrating PV—with small para­ bolic dishes. Although some individual residences might 

have problems with local zoning and/or covenants, the 

use of dishes, or even CSP troughs, could be landscaped 

into visual acceptability. Such approaches are currently 

being developed in Australia, where hybrid CPV- hydrogen production units have been demonstrated suc­ cessfully. The case for the “solar hydrogen park” is that 

the distribution of hydrogen is over a small distance, 

generating the fuel very near the point of use. In fact, the efficiency of the system and the effectiveness of generat­ ing the hydrogen can be increased with technology evolution—such as a thin-layer electrolyzer integrated with the PV modules (e.g., integrated into the PV/thermal roof 

1 
module) and/or having pyrolysis systems integrated with 

the PV. Both of these approaches reduce the hydrogen “transportation” distances during the production cycles. 

It is also possible that the hydrogen storage could be 

integrated into this structure, using carbon-nanotube 

technology in a thin-layer configuration. 

Figure 1: Distributed Solar-Hydrogen Residence Concept. 

This paper examines these future possibilities—the 

energy-plus home and the solar hydrogen park—for technical feasibility and economics feasibility, and timeexpectations are evaluated in terms of expected technology 

advancements and predictions from the U.S. PV Industry

Roadmap [19]. 

3. ECONOMICS AND TIMES VERSUS ROADMAPS 

The economics of producing hydrogen using PV has 

been examined by a number of sources [20–27]. A simplistic economic potential might be gauged by comparing 

the “market” selling price of hydrogen to the corresponding solar production cost—and the portion of this cost 

that is attributed to the electricity. Currently, purified, 

noncompressed hydrogen is produced for about $0.75/kg 

to $2/kg, depending on the volume and quality purchased. Currently, PV electrolysis is about an order of 

magnitude more expensive ($7/kg–$25/kg), depending on 

the tax credit and rate and on the internal rate of return 

[7–9,12,19]. (There is no current “cost” for hydrogen 

from PV photolysis because there is no production, ex­ cept in the research laboratory. However, some analysts still estimate this cost near the $20/kg level—with ample assumptions!) Hydrogen (from natural gas) is currently 

delivered at about $5/kg to a car at a refueling station. Of 

this, about $1.90/kg is credited to the electricity (at a rate 

of $0.035/kWh). For a smaller electrolysis system, the current cost is $7.40/kg to $8.00/kg), with the electricity 

portion at $4.10/kg (at a $0.06/kWh rate). These two 

cases correspond to the distributed-generation scenarios in Figs. 2 and 1, respectively. Of course, current PV 

electricity is generated at a rate in the range of 

$0.18/kWh–$0.25/kWh—higher than conventional elec­ tricity without some incentives. Can PV eventually meet 

the price criteria for generating electricity competitive for 

the distributed hydrogen requirements? As a basis, we will use the U.S. PV Industry Roadmap as a guide to 2020—and some preliminary (not finalized) targets from 

the in-progress industry roadmap realignment (which 

provides a new set of targets because funding and policy 

assumptions were not met for the original strategy)—as 

well as learning or experience curves to predict the fu­ tures to 2050. The requirements for hydrogen (and the 

electricity cost to produce it) will be taken from the new 

Multi-Year Technical Plans. Levelized electricity cost­ ing (LEC) is used. 

Table 1 presents a comparison of relevant costs, goals, and predictions over the timeframe of 2003 

through 2050. Current (2003) PV electricity prices are 

certainly not competitive. Neither the end-of-the-decade 

goal of $3–$4/W for systems in the current roadmap nor 

the $3/W (2015) for the realigned roadmap can be expected to lower the electricity price to the levels required 

by the hydrogen Multi-Year Plan for the defined costcompetitive region. The major goal is $0.06–0.08/kWh 

in 2020 (for both the Roadmap [19] and the U.S. DOE 

Solar Energy Technologies Program [12]). With more 

aggressive policies, the realigned roadmap could bring 

about electricity prices below this. This electricity price meets the hydrogen goal for 2010, but is still below the 

more sound expectation of about $0.04/kWh, reached in 

2030—or about 2025 possible in the realignment. Prices beyond the roadmap timeframes can be deduced from the 

learning curve data [28], which shows that PV has historically followed an “80% learning curve” (i.e., for each 

doubling of cumulative production, the price decreases 

by 20%) [28]. Similar timeframes can be anticipated for 

both the residential and the solar village concepts—if the PV Roadmap goals are met & the learning curve continues past 2020. For a central PV station, by comparison, 

the required electricity price is the wholesale electricity 

price, which will not be reached until at least 2040 (about 

5–8 years sooner in the realignment). This corresponds 

to hydrogen at about $1.60–$1.70/kg, which, in the case of transportation, is equivalent to $1.25–$1.35/gallon of 

gasoline with a 0.2%/year escalation [7,9]. 

This analysis shows that even the roadmap projections allow PV to fit well into an eventual hydrogen economy 

in the United States. But how can we get there sooner? 

If some of the “predictors” are off, then certainly the competition with other energy sources can bring about 

this solar scenario faster. For example, if the Energy 

Information Administration gasoline escalation was higher than 1%/year, this would mean that roughly 

$0.35/kWh to $0.45/kWh PV would be economical— 

realizing the 2040 centralized goal about 10 years sooner, or accelerating the 2030 expectations by 3–5 years. 

However, it is difficult to propose such an alternative without also pointing out that the roadmap goals may not 

be reached, that the learning curve for PV might be 85%, 

or that prices and availabilities of competing fuel sources 

might be more, rather than less, favorable. Moreover, the realigned roadmap would accelerate the longertimeframe goals (e.g., beyond 2025) by as much as a 

decade—if the realigned roadmap conditions are met. Expectations that disruptive technologies will favorably alter the learning curve also present risk. However, 

the risk depends on reasonable science, rather than specu­ lation. These breakthrough technologies lower prices and 

open markets more rapidly. An example is that of the 

transistor, which was continuing on a 90% learning curve until the late 1950s. With the introduction of the integrated circuit—certainly a disruptive technology from 

business as usual—that electronic technology followed a 50%-60% learning curve for a brief period, until it settled 

on an 80% characteristic, similar to that of PV. Thus, as 

the cumulative units that were produced quickly in- creased due to the integrated processing, the cost per unit 

fell—and the demand for this new technology increased 

substantially. This “integrated” innovation is not much 

different than the second and third generations of PV that 

are already being pursued. This same impact of innovation can bring about PV—and PV for hydrogen—more rapidly. Thin-film technologies (especially multijunction 

polycrystalline approaches), nanotechnologies, and “plastic” cells all address low-cost breakthrough PV, primarily 

for our distributed scenarios [2,29]. On the other hand, 

super-high-efficiency PV using quantum dots, rods, or pods, ultra-multijunctions, impurity or intermediate layer cells, thermophotovoltaics or thermophotonic all pose 

breakthrough possibilities on the other end of the technology spectrum [2,29]. They are aimed at both central­ ized and distributed power-park applications. Addition- ally, the direct production of hydrogen by photolysis 

(electrochemical methods) is also a breakthrough tech­ nology. This has considerable potential for cost effectiveness—but the problems of performance (efficiency 

2 
Table 1: Competitiveness comparison of PV-hydrogen based roadmaps and multiyear plans. Italiziced numbers projected from roadmap using technology learning/experience curves. Proposed (not final) roadmap targets and projected indicated in grey tones. 

2004–05 2010 2015 2020 2030 2040–50 

PV System Price $6–$15/W $3–$4/W [$3/W] $1.50–$2.00/W 

[<$1.50/W] ~$1.00/W ~$0.50/W 

PV Electricity Price $0.18– 

0.25/kWh 

$0.11– 

0.16/kWh 

[$0.061– $0.10/kWh+

] 

$0.06–0.08/kWh 

[$0.05–0.07/kWh] 

~$0.045/kW 

h 

[<0.04/kWh 

] 

~0.03/kWh 

U.S. PV Capacity or Shipments (for that 

year or cumulative in- stalled) 

0.2–0.4 

GW/yr 0.8– 1.0GW/yr 

[2-2.75GW/yr 

U.S.] 

7–8GW/yr of 

which 

3.1GW/yr U.S. 

[130GW 

installed cumulative] 

1000–1600TWh/yr [2000–3000TWh/yr]

[450–630GW in- stalled cumulative] 

Targets 15% of new (added) U.S. gen­ eration capacity* 

10% of total 

U.S. genera­ tion capacity** 

15%–18% of total 

U.S. generation ca­ pacity 

[50% of all build­ ings; 

1/4–1/3 of U.S. elec­ tricity] 

Performance-Efficiency 

Range for Best Com­ mercial 

(Cell/ Module/ Sys­ tem)*** 

10–20%/ 

11–15%/ 

7–12% 

18–25%/ 

14–17%/ 

9–14% 

[Likely at 

higher end of 

2010 goals] 

20–28%/

16–20+%/

13–18% 

[20+-35%/

18–24%/

14–20%] 

20+–40%/

18+–28%/

16–20% 

[22–40+%/

20–30%/

18–25%] 

Ultra-high-efficiency modules: >40% 

Ultra-low-cost modules: >20% 

Distributed Hydrogen: Solar Park (Electroly­ sis) 

Total Price Electricity Price $4.70/kg 

$1.90/kg 

$2.50/kg 

$1.60/kg 

Distributed Hydrogen: Residence (Electrolysis) 

Total Price Electricity Price $7.40/kg 

$4.10/kg 

$3.80/kg 

$2.80/kg 

Distributed Hydrogen: Photolysis (Electro­ chem) 

Price Efficiency (solarhydrogen) 

N/A 

7% 

$22/kg 

9% 

$5/kg 

14% 

Roadmap assumptions: R&D budget (original: $100 million/year, never reached; new $150 million/year, 10–15 years) 

Major aggressive policy changes (incentives, etc.) on state and federal levels; 30-year system lifetime + Depends on discount rate *Target reached in 2018 with new roadmap. 

**Target reached in 2026 with new roadmap. 

***Higher efficiencies are noted in the 2020–2050 timeframe for concentrating PV technologies and 

preliminary ultrahigh-efficiency concepts leading toward commercialization. 

and reliability) need to be proven (see Table 1). In the 

1980 timeframe [30], a rooftop system was demonstrated, 

but it used hydrogen bromide—which had inherent envi­ ronmental concerns. If the same type of system could be 

realized using water splitting, the distributed hydrogen 

scenario would be widespread. If the performance levels for modules and systems, indicated in Table 1, are 

reached, the solar-PV hydrogen option will certainly be 

one of choice, not imposition. The increased focus on R&D through enhanced budgets—providing a balanced 

investment between now-, near-, and next-term PV technologies would certainly lower the risk for the required 

technology developments in these timeframes. 

4. HYDROGEN LOOKS GREAT...BUT MAYBE NOT 

What are the limitations for this approach? Certainly, 

the arguments for hydrogen are abundant—and at first 

glance, compelling. However, if the academic exercise were given to a graduate student to find the best fuel alternative to transportation, for example—perhaps hydrogen 

would not be the answer. Because of its density, it has to be compressed to high pressures. Because of its atomic 

number, the constraints on the distribution (e.g., leaks) are 

very rigid. Because of the nature of hydrogen (and the 

pressure requirements), there are safety issues raised, as 

well. It might be better to choose a liquid that could be 

generated from the solar source. Such is the interesting 

approach proposed by Lewis [31]—the “methanol economy.” His careful analysis is based on considering the best options, using closed approaches to control the carbon 

emissions, and examining all the “electricity sources.” His 

conclusion is liquid methanol, produced by solar (and actually, solar photovoltaics). Lewis is strong in his belief 

that the total energy must be considered in any long-term 

energy planning [31]—not just electricity (which he re- ports is only 10% of the world’s primary energy now), 

chemicals, fuels, etc. In some sense, this is a parallel to 

the hydrogen approach just discussed: conversion of solar energy to electricity via PV, driving a “methalyzer” to 

produce liquid methanol, and then transporting the liquid 

fuel (from central sites in the Lewis concept) to the point 

of use. Of course, it might also be possible to use the dis­ tributed approach—depending on the efficiencies of the 

processes involved. Other approaches exist, as well (e.g., other fuels, hybrids, pure electrical economies [32]). 

However, the ensemble of metrics (relative economics, 

materials availability/security, impacts on related products, 

3 
technological feasibilities, and, of course, politics) will 

lead to the eventual winners. Hydrogen is certainly a promising technology that is an ideal partner to solar. But 

do not close the deal; do not rule out other approaches yet. It is too early to lock in on a single approach. We should remain technically flexible...and provide the innovation 

and creativity to provide our coming generations with 

coming generations of abundant clean, secure energy. 

5. SUMMARY 

Future energy can (should) include PV and hydrogen. The concept of the zero-energy building can be envisioned 

to expand to the “energy-plus home” that produces more 

energy (electricity for the residence, hydrogen for night- time power and the family “Freedom Car”). The solarhydrogen park or village is an extension of this, in which 

the solar energy and hydrogen is shared in the community. 

Again, additional electricity can be supplied to the grid 

and any excess hydrogen can be sold through the community’s refueling stations. The marriage between hydrogen and solar brings secure, clean energy—as well as making 

PV a “24-hour power” option. 

The “but when?” can be estimated from the predictions 

of the U.S. PV Industry Roadmap, the hydrogen and solar 

Multi-Year Technical Plans, and considerations of the 

learning curves for the technology. Centralized PVhydrogen will not likely be available until the 2040 

timeframe. Decentralized approaches can be reached by 

2035, depending on the escalation factors for other fuels. 

Through the acceleration of technology fueled by the policies, investments, and strategies of the new realigned U.S. 

PV Industry Roadmap, distributed and decentralized approaches can be accelerated by 5–8 years. The result 

would be an acceleration, similar to that anticipated in the 

United States by the current hydrogen program. 

Disruptive technologies—second-generation thin films, 

organics, and nanotechnologies—can accelerate the nearer 

term by 5–10 years or more. Third-generation higher-cost 

approaches (such as quantum technology cells, ultramultijunctions, new materials, novel structures, and novel 

concentrators having performances beyond 50% efficiencies) can accelerate both distributed and centralized approaches. The further investment and careful strategycontrolled path into these next-generation breakthrough 

technologies will benefit the learning curve to bring not 

only solar-PV electricity, but also, solar-PV hydrogen 

significantly closer. They can be realities within a generation of our population. 

Acknowledgements: The technical work was supported by the 

U.S. Department of Energy through Contract No. DE-AC36-

99GO10337 with the National Renewable Energy and the U.S. 

DOE MURA (Minority University Research Associates) Program. 

The views are primarily those of the authors. Kara Broussard is a 

student at Southern University, Baton Rouge, Louisiana, serving 

as a summer intern at NREL. The assistance, input, and encouragement of Professor Rhambabu Boba of Southern University, 

Allen Barnett and Robert Birkmire of the University of Delaware, 

and Roland Hulstrom, Robert McConnell, John Turner, Tom Surek, Robert Margolis, Don Gwinner, Al Hicks, and Fannie 

Posey-Eddy of NREL are gratefully acknowledged. 

6. REFERENCES 

[1] P. Maycock, PV News, Vol. 23(3), Mar. 2004; Photon International, April (2004) pp.40–41. 

[2] See, for example, technical reports in the Pro­ ceedings of this conference (2004). [3] L.L. Kazmerski, Proc. 39th IEEE Photovoltaics Spec. Conf., (IEEE, New York; 2003) pp. 21–27. 

[4] T. Surek and L.L. Kazmerski, SPIE oeMagazine (SPIE, Bellingham, WA.) May 2003, pp.24–27. 

[5] J. Perlin, L.L. Kazmerski, and S. Moon, Solar Today, Jan.-Feb. (2004) pp.24–27. 

[6] G. Davis, Evolving Sources or Revolutionary Technology—Exploring Alternative Energy Paths to 2050, Proc. Oil & Money Conference, London, Oct., 2001 (pp.1–11). [7] National Vision of America’s Transition to a Hydro­ gen Economy to 2030 and Beyond, Feb. 2002. 

[8] National Hydrogen Energy Roadmap, Nov. 2002. 

[9] Hydrogen, Fuel Cells & Infrastructure Technologies Program, Multi-Year Research, Development and 

Demonstration Plan (U.S. Department of Energy, 

Energy Efficiency and Renewable Energy, Washington, DC), June 2003. 

[10] Scientific American, May 2004, pp.66–74. 

[11] National Energy Policy, Report of the National En­ ergy Policy Development Group, May 2001 

[12] U.S. DOE Solar Energy Technology Program Multi- Year Technical Plan, 2003-2007 (NREL, Golden, CO; 2004). [13] J. Deutch and E. Moniz, Editorial, N-Power Key to World’s Future, Arizona Daily Star, Friday, August 

15, 2003 (www.azstarnet.com). 

[14] Energy Information Administration, International 

Energy Annual Report, 2002 (Washington, DC). [15] L.L. Kazmerski, Solar Today, Vol. 16, No. 4, pp.40– 

43, 2002. 

[16] L.L. Kazmerski, Proc. Hybrid Conf. (2004). Also, 

PV FAQ (www.nrel.gov/ncpv). 

[17] PV FAQ sheets, www.nrel.gov/ncpv 

[18] NAC, The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D (National Academies Press, 2004). [19] Solar Electric Power: U.S. Photovoltaics Industry

Roadmap (U.S. PV Industry; May, 2001). [20] J.A. Turner, Science, Vol. 285, July 30, 1999, 

pp.687–689. 

[21] See, for example, New York Times, August 15, 2003 

[22] M.K. Mann, P.L. Spath, and A.S. Watt, 9th Canadian Hydrogen Association Meeting, Vancouver, B.C. 

(Hydrogen Association). 

[23] R. Rocheleau, E. Miller, and A. Misra, Proc. U.S. 

DOE Hydrogen Prog. Rev. NREL/CP-430-21968 

(National Renewable Energy Laboratory, Golden, 

CO; 1996) pp.345–352. 

[24] J.M. Vidueria, A. Contreras, and T.N. Vesiroglu, Int. 

J. Hydrogen Energy, Vol. 28, 927-937 (2003). [25] D.L. Block and I. Melody, Int. J. Hydrogen Energy , Vol. 17, 857 (1992). [26] A. Kazim and T.N. Veziroglu, Renewable Energy, Vol. 24, 259–274 (2001). [27] C.C. Elam, C.E. Gregoire Padro, G. Sandrock, A. Luzzi, P. Lindblad, and E. Fjermestad Hagen, Int. J. 

Hydrogen Energy, Vol. 28, 601–607 (2003). [28] T. Surek, Proc. 3rd World Conference on Photovol­ taic Energy Conversion, Osaka, Japan, May 2003. 

[29] R. McConnell, S. Moon, and L.L. Kazmerski, Solar Today, to be published, June 2004. 

[30] W.R. McKee, D.R. Carson, and J.D. Levine, Proc. 16th IEEE Photovoltaics Spec. Conf. (IEEE, New 

York; 1982) pp.257–261. 

[31] N. Lewis, see Web page for detailed presentation http://www.its.caltech.edu/~mmrc/nsl/default.htm [32] J.J. Romm, The Hype About Hydrogen (Island 

Press, New York; 2004). 

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14. ABSTRACT (Maximum 200 Words) 

Future solar photovoltaics-hydrogen systems are discussed in terms of the evolving hydrogen economy. The focus 

is on distributed hydrogen, relying on the same distributed-energy strengths of solar-photovoltaic electricity in the 

built environment. Solar-hydrogen residences/buildings, as well as solar parks, are presented. The economics, 

feasibility, and potential of these approaches are evaluated in terms of roadmap predictions on photovoltaic and 

hydrogen pathways—and whether solar-hydrogen fit in these strategies and timeframes. Issues with the “hydrogen 

future” are considered, and alternatives to this hydrogen future are examined. 

15. SUBJECT TERMS 

PV; solar hydrogen; system; roadmaps; electrolysis; photolysis 

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Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18 

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