Basic Research Needs for Solar Energy Utilization

12.13

3.03

5.28

5.28

0.37

0.37

0.00

5.00

10.00

15.00

20.00

25.00

Effect of Solar Module Cost

$/kg Hydrogen Cost

Overhead and

Maintenance

Electrolyzer Cost

Solar Electric Cost

$17.78/kg

$6/Wp

2005 price

$8.68/kg

$1.5/Wp

2020 target

Figure 72 Hydrogen selling price for carbon-free solar electricity (assumes

42 kg/hour production rate)

This analysis reveals that the capital cost of the electrolyzer becomes significant in an application
that combines it with solar power.

With a 2020 solar efficiency of 20% and an electrolyzer system efficiency of 65%, the overall
solar conversion efficiency will be about 13%. It is not unreasonable to foresee that by 2020,
systems for photocatalytic hydrogen evolution, where hydrogen is evolved directly from a
photocatalytic surface, would probably be more effective than electrolyzers in generating
hydrogen fuel.

REFERENCES

A. Aden, M. Ruth, K. Ibsen, J. Jechura, K. Neeves, J. Sheehan, and B. Wallace, Lignocellulosic
Biomass to Ethanol Process Design and Economics Utilizing Co-current Dilute Acid
Prehydrolysis and Enzymatic Hydrolysis for Corn Stover, Golden, Colo.: National Renewable
Energy Laboratory, NREL/TP-510-32438 (2002).

A. Bullion, “Ethanol Trends,” International Sugar Journal, CVI ( 1263 ), 173–174, 177 (2004).

H.L. Chum and R.P. Overend, “Biomass and Bioenergy in the United States,” in Advances in
Solar Energy: An Annual Review, Y. Goswami (Ed.), Boulder, Colo.: American Solar Energy
Society, 83–148 (2003).