Photovoltaic (PV) power generation is an intermittent, non-dispatchable resource generally considered as energy-only with no capacity credit. However, there is ample evidence that solar energy...
Technologies are scaling up quickly to meet industry needs.
will purchase the output.
Power tower supplier and developer BrightSource Energy has the boldest development plan to date. The Oakland-based company says it will build and own some 2,600 MW of power tower capacity, with seven plants generating 1,300 MW to be delivered to SCE and seven more generating another 1,300 MW under contract to PG&E. Its first plant, the 440-MW Ivanpah Solar Power Complex, will be located in Ivanpah, approximately 50 miles northwest of Needles, Calif., and about five miles from the Nevada border.
The plant will be constructed in three phases, two 110-MW facilities and one 220-MW facility. The first phase is scheduled to begin construction in early 2010 and be completed by 2012. The second phase will begin construction roughly six months after the start of the first. The plant is located near existing transmission lines and will require relatively minor line upgrades to connect and deliver its power to PG&E.
BrightSource is led by the original management team of Luz International, which developed a group of nine CSPs known as the Solar Energy Generating Systems (SEGS) in the Mojave Desert between 1984 and 1991. Those plants, now owned by FPL Group and SCE, employ parabolic trough technology and generate a cumulative 310 MW. The Luz team is now embracing a power tower design it says can generate more heat, and therefore steam, to drive today’s higher-efficiency steam turbines, says spokesman Keely Wachs.
“The holy grail in this business is high temperatures and high pressure steam. With the trough technology we could get maximum steam temperatures between 300 to 400 degrees [Centigrade]. With the power tower design, we can get 550 to 650 C. You’ve got to reach those temperatures to take full advantage of today’s advanced steam turbine technologies. Otherwise it’s like putting a 486 chip in a new computer,” Wachs says.
Concentrating the solar energy directly on the boiler, he says, results in a 15-percent efficiency gain over a trough design. Further efficiency gains are realized with heliostats that can be raised and lowered to optimally track the sun as its angle changes with the seasons. And though it decreases efficiency and increases the plant’s capital cost, dry cooling will be employed to reduce its water requirements.
“Wet cooling uses 20 times more water,” Wachs says. “Dry cooling supports a closed-loop system that continually feeds the steam cycle. Ivanpah will require 100 acre feet of water, which is the equivalent of 300 homes worth of water a year. Most of the water will be used to wash the mirrors. You do take a hit with dry cooling, but we believe wet technology will have a hard time getting permitted because the West is so water sensitive.”
Demand for PV also is on the rise, as is size of new PV plants. However, unlike with CPS technology, some utilities are taking an ownership position. Both PG&E and SCE, for example, have announced they will build, own and operate 250 MW of PV assets over the next five years.
Growing interest from utilities is driving PV suppliers