Technology Comparison

Table 1 below highlights the key features of the three solar technologies. Towers and troughs are best suited for large, grid-connected power projects in the 30-200 MW size, whereas, dish/engine systems are modular and can be used i n single dish applications or grouped in dish farms to create larger multi-megawatt projects. Parabolic trough plants are the most mature solar power technology available today and the technology most likely to be used for near-ter m deployments. Power towers, with low cost and efficient thermal storage, promise to offer dispatchable, high capacit y factor, solar-only power plants in the near future. The modular nature of dishes will allow them to be used in smaller, high-value applications.

Towers and dishes offer the opportunity to achieve higher solar-to-electric efficiencies and lower cost than paraboli c trough plants, but uncertainty remains as to whether these technologies can achieve the necessary capital cost reductions and availability improvements. Parabolic troughs are currently a proven technology primarily waiting for a n opportunity to be developed. Power towers require the operability and maintainability of the molten-salt technolog y to be demonstrated and the development of low cost heliostats. Dish/engine systems require the development of at least one commercial engine and the development of a low cost concentrator.

Table 1. Characteristics of solar thermal electric power systems.

Parabolic Trough

Power Tower

Dish/Engine

Size

30-320 MW*

10-200 MW*

5-25 kW*

Operating Temperature (°C/°F)

390/734

565/1,049

750/1,382

Annual Capacity Factor

23-50%*

20-77%*

25%

Peak Efficiency

20%(d)

23%(p)

29.4%(d)

Net Annual Efficiency

11(d')-16%*

7(d')-20%*

12-25%*(p)

Commercial Status

Commercially

Scale-up

Prototype

Available

Demonstration

Demonstration

Technology Development Risk

Low

Medium

High

Storage Available

Limited

Yes

Battery

Hybrid Designs

Yes

Yes

Yes

Cost

$/m2

630-275*

475-200*

3,100-320*

$/W

4.0-2.7*

4.4-2.5*

12.6-1.3*

$/Wrt

4.0-1.3*

2.4-0.9*

12.6-1.1*

Values indicate changes over the 1997-2030 time frame. f $/Wp removes the effect of thermal storage (or hybridization for the power tower TC and footnotes in Table 4. (p) = predicted; (d) = demonstrated; (d') = has been demonstrated,

Values indicate changes over the 1997-2030 time frame. f $/Wp removes the effect of thermal storage (or hybridization for the power tower TC and footnotes in Table 4. (p) = predicted; (d) = demonstrated; (d') = has been demonstrated, dish/engine). See discussion of thermal storage in out years are predicted values

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