Renewables, Solar

Power Generation Week Attendees Experience Solar Generation Up Close at Ivanpah

A group of Power Generation Week attendees visited the Ivanpah concentrated solar power facility Monday. The tour included a presentation about the facility and the safety and environmental protection measures employed there, as well as a drive through the fields of heliostats to the base of tower two.

The Ivanpah facility, completed in 2014, features 175,000 heliostats that hold 350,000 mirrors. The heliostats, which are situated in three separate fields, are devices that hold the mirrors and can be adjusted so the mirrors reflect sunlight onto thermal receivers that sit atop the three 460-foot towers at the center of each field.

Unlike the solar photovoltaic panels that are used on rooftops and soak up sunlight to generate power, the mirrors reflect sunlight onto the thermal receivers, which in turn heat water to power steam turbines.

According to an NRG Energy spokesperson, when these thermal receivers are glowing the system is generating electricity that is going to the grid under a must-take agreement. While at the facility, the two operating towers generated 822 megawatt-hours (MWh) of electricity. With the combined capacity of the three towers – 126 MW for tower one and 133 MW each for towers two and three – the Ivanpah facility will generate 392 MW of power per hour by 2018, following a four-year ramp-up period.

The spokesperson said under the best conditions – a sunny, dry day with no wind – the facility can generate at full power from about 10 a.m. to about 2 p.m. Located in the Mojave Desert, Ivanpah benefits from prevalent sunny conditions, but environmental factors can affect operations.

“It’s finicky,” said NRG’s spokesperson. “It likes perfect weather.”

Clouds, for example, have a big effect on the day-to-day operations, and predicting their type and presence is not easy. The spokesperson said NRG is working on ways to better understand when, and to what extent, clouds will form. Other factors like moisture, wind and dust also influence the ability of the mirrors to reflect sunlight onto the thermal receivers.

The tour concluded with a visit to the main control room, where staff members watch banks of computer screens that deliver endless amounts of data about the operation of the facility. From there, software calculates how the mirrors should be positioned to get the desired MW output from the facility. The control room is set up with three stations, each covering one of the towers. Another station allows staff to monitor the weather. The spokesperson said their weather data is predictive but not 100 percent accurate.

Now that Ivanpah is fully operational, the spokesperson said there are no plans to expand the project, but NRG is looking into the possibility of building energy storage functionality into the system. For now, the 65-member staff is focused on ensuring the project is ready to run whenever the sun shines.