The Ivanpah Solar Power Facility, officially opened in February 2014 in the Mojave Desert (United States), became the world’s largest solar thermal tower plant, with a gross installed capacity of 392 MW and more than 173,500 heliostats spread over three fields that concentrate solar radiation onto boilers 140 metres high. Its construction, valued at approximately £1.6 billion, was supported by a £1.6 billion federal loan from the US Department of Energy (DOE), making it one of the most ambitious projects of the Obama era.
Jointly owned by NRG Energy, BrightSource Energy and Google, Ivanpah was conceived as a demonstration of the potential of tower solar thermal power to provide stable generation, even at night, through thermal storage.
How does a solar thermal power plant work?
Tower-type concentrated solar power plants use movable mirrors, or heliostats, that track the sun and reflect its rays onto a central receiver where steam is generated. This steam drives conventional steam turbines to produce electricity in a similar way to a thermal power plant, but without the direct combustion of fossil fuels.
The ability to store heat in molten salts allows generation to be extended beyond daylight hours, although at Ivanpah this functionality was limited by the original design and the need to supplement the system with natural gas to achieve optimal operating temperatures.
Ivanpah had more than 173,500 heliostats.
Covering an area of around 13 km², the plant had the capacity to supply around 140,000 homes. The ambitious project required an investment of £1.6 billion, of which £1.1 billion came from a federal loan from the US Department of Energy (DOE).
The computer-controlled heliostats tracked the sun throughout the day and concentrated its rays on three 140-metre-high towers, where a central receiver heated water to generate steam. This steam drove conventional steam turbines, producing clean electricity without burning fossil fuels. Although the project envisaged molten salt storage to extend generation after sunset, in practice this capacity was limited by the initial design of the plant.
Several problems lead to the plant’s closure ahead of schedule
Pacific Gas & Electric’s (PG&E) decision to terminate its power purchase agreements with Ivanpah is due, to the company, to significant savings for its customers compared to other more economical sources. These clauses, initially valid until 2039, set prices that are now high compared to the steady decline in the cost of photovoltaic silicon and storage batteries.
In addition, the operating costs of the solar tower plant, which include maintenance of thousands of mirrors and management of the central receiver, have proven to be higher than those of photovoltaic solar plants of a similar scale.
Operators faced technical problems such as misaligned heliostats and unexpected heat losses that reduced the performance of the receivers. To achieve optimal operating temperatures, the plant had to resort to natural gas backup, which reduced its actual “zero emission” profile. The harsh desert conditions also caused frequent breakdowns in the moving mechanisms and drove up maintenance costs.
But that’s not all. Since its inception, Ivanpah has been criticised for its impact on local wildlife. It has been estimated that tens of thousands of birds have died each year flying over the heliostat field and overheating as they pass through the solar concentration focus. Environmental organisations documented that up to 28,000 birds died each year from overheating when flying through the solar concentration focus, making Ivanpah a “death trap” for local birdlife. Conservationists claimed that the environmental impact study did not adequately assess the risks to endangered species such as desert tortoises and migratory birds.
Some experts called the project a financial ‘boondoggle’ and an environmental ‘disaster,’ pointing out that the public investment did not result in the desired energy yield and that the complementary natural gas diminished its zero-emission profile. In January 2025, the owners of Ivanpah and the DOE concluded negotiations with PG&E for the termination of two contracts, sealing the fate of the project.
Dismantling and prospects for reuse
The dismantling of the decommissioned units will provide an opportunity to convert part of the site for photovoltaic or hybrid projects, taking advantage of infrastructure already connected to the grid.
Its operators have suggested that the site could house simpler and cheaper solar panel fields, alongside battery storage systems, to meet peak demand needs. This change in approach reflects the global trend towards technologies that combine low investment costs with operational flexibility and reduced environmental impact.
