solar power on a large scale in the United States will need the technology to have reached cost parity with current energy sources. The energy delivered to the grid as electricity will, for solar, need to reach “grid parity”; the faster solar power can do that, the better for the U.S. economy as a whole.

Solid-state (SS) lighting is clearly the next step in lighting. It has already become entrenched in many niche applications and is moving quickly toward adoption as the new standard for general lighting. The record efficiency for SS lighting today is 231 lumens per watt (lm/W),8 compared to 4-15 lm/W for a conventional incandescent bulb, and approximately 55 lm/W for a compact fluorescent bulb. Cost is the main issue preventing widespread adoptions of SS lighting, but substantial progress is being made in lowering the cost of light-emitting diodes (LEDs).

In the 1998 NRC study Harnessing Light: Optical Science and Engineering for the 21st Century,9 solar cells are discussed for space application, with a short section on terrestrial application. At the time of that publication, the cost to purchase solar cell panels for terrestrial application was $4.50 per watt (W), compared to the current cost, which is as low as $0.75/W. LEDs, also called SS lighting, were barely discussed in the 1998 report, in which Figure 3.12 shows efficiencies from 20-80 lm/W for LEDs, compared to the current record of 231 lm/W.


Solar power has received great interest recently as a renewable energy solution capable of providing energy independence and environmental stability while beginning to deliver power at a competitive price. Because of high costs relative to other energy generation technologies, solar power currently satisfies only a small fraction of the world’s energy need. Government support and private investments have led to a boom of technical advances over the past years that have continued to drive solar power toward eventually being a mainstream source of power.10

Solar power has great potential for home, off-grid, and utility-scale generation. Solar cells have become common in applications for which grid power is not accessible (see Figure 5.1) or convenient, such as powering remote devices or small handheld electronics. As will be seen in this chapter, utility-scale solar plants are not yet competitive with alternative sources of energy, yet the cost of solar electricity


8 More information about Cree is available at Accessed December 17, 2011.

9 National Research Council. 1998. Harnessing Light: Optical Science and Engineering for the 21st Century. Washington, D.C.: National Academy Press.

10 Tyner, C. E., G.J. Kolb, M. Geyer, and M. Romero. 2001. “Concentrating Solar Power in 2001—An IEA/SolarPACES Summary of Present Status and Future Prospects.” International Energy Agency—SolarPACES. Available at Accessed August 1, 2012.

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