Just after noon on a 43C summer day, the 14.5 sq km Desert Sunlight Solar Farm - the biggest of its kind erected on US federal land - is proving why this desolate spot is such a good one for harnessing the sun's rays.
With few clouds above, the seemingly endless 8-million-panel array is churning out enough electricity to power 160,000 homes some 280km west of here in Los Angeles.
"This is fairly typical, that as the sun moves through the sky, this is about the time of day that we hit that sort of number," said Steve Stengel, a spokesman for the plant's co-owner, NextEra Energy Resources.
Giant solar arrays such as Desert Sunlight not only generate vast amounts of power, but they also do not require any fuel or produce any carbon emissions - advancing the ambitious climate goals of California and the United States alike.
But lately, those lofty goals have run into a more earthly reality: Large-scale solar projects require vast amounts of land, land that also is home to many animal and plant species, most iconic among them a slow-moving herbivore called the desert tortoise.
The creature is so highly regarded by the conservation community, and so threatened by climate change, that groups that might otherwise regard themselves as allies of clean energy find themselves at odds with the solar industry.
The two sides are squaring off on a US Bureau of Land Management plan to allocate some 4 million ha of public land in the California desert for conservation, recreation and clean-energy installations like the 550-megawatt, or million watt, Desert Sunlight.
The solar lobby argues that the current draft plan would throttle the industry's expansion, making it difficult to meet the nation's renewable-energy goals. Environmentalists want to preserve "connectivity" between areas of vital species habitat so that tortoises and other animals can move around and adjust to warming conditions, which could drive them to higher, cooler elevations. For the animals, reaching distant mountain ranges might mean crossing flat stretches where, otherwise, companies might put solar installations.
The resulting proposal would allocate 157,000ha of federal land for renewable-energy development, while protecting 2.1 million ha for conservation reasons and 1.5 million ha for recreation. (The last two involve some overlap). "Over twice the amount of important desert tortoise lands" would be protected under the plan, the agency determined.
"Why the administration would on one hand call for greater use of renewable energy on public lands as a way to hit carbon-reduction targets while cutting off access to the land needed ... is lost on us," said Dan Whitten, vice-president for communications at the Solar Energy Industries Association, the main trade group of the booming solar industry.
The industry's stance on the initiative - dubbed the Desert Renewable Energy Conservation Plan - has in turn triggered criticism in the conservation world and spurred a counter-mobilisation in the plan's favour.
"We've been at this for eight years. The industry has been at the table, and to have these issues come up ... at the 11th hour seems a bit not only mystifying but disingenuous on their part for not bringing them up earlier," said Ileene Anderson, a senior scientist with the Centre for Biological Diversity, one of a number of prominent environmental groups backing the plan.
What's behind it all is a desert that, far from being deserted, is in high demand - presenting a complex patchwork of urban areas, national parks and monuments, military bases, lands of major cultural significance to Native Americans, and more.
The Bureau of Land Management (BLM), a branch of the Interior Department, has been charged with managing 4 million publicly owned hectares of this landscape since 1976, a period that coincided with a steady decline in the population of the tortoise, a long-lived and slow-reproducing reptile that digs telltale burrows in the dry earth to keep cool.
The tortoise is threatened by roads, off-road vehicles and more - including a changing climate. It is considered an "umbrella" species because its habitat overlaps with so many others. "By protecting the tortoise, you protect all the other species in the desert," said Mark Massar, a wildlife biologist with the BLM.
Concern for the tortoise mounted as the desert solar boom hit in the late 2000s, buoyed by President Barack Obama's economic stimulus act and California's ever-more-ambitious targets for renewable energy, which currently require power companies to get 50 per cent of their electricity from clean sources by 2030.
The conflicts were epitomised by the Ivanpah solar plant in the Mojave Desert. One environmental group, the Western Watersheds Project, sued the federal government in 2011 to stop the project. That didn't happen, but developers ultimately had to spend millions of dollars to protect desert tortoises at and around the site.
It is in this context that the BLM began a protracted process to apportion the land, collaborating with federal and California partner agencies.
For renewable energy, one of the largest designated areas lies in east Riverside County, California, halfway between Los Angeles and Phoenix along Interstate 10. The region, called the Chuckwalla Valley, is part of a dry and harsh landscape that once supported massive World War II training exercises overseen by Army General George S. Patton, who was preparing an Allied invasion force to go into North Africa.
One advantage of this valley is that it contains many hot, low-lying areas that are less-desirable habitat for tortoises, which prefer higher elevations. Even conservationists say they are okay - mostly - with solar installations out here.
"This is a pretty decent area to be what you might call a sacrifice area for solar," Joan Taylor, a longtime desert conservation advocate who chairs the Sierra Club's California/Nevada Desert Committee, said as she surveyed Desert Sunlight recently.
The solar-energy industry has moved quickly to lay claim to the area. To the east of Desert Sunlight, near the Arizona border, NextEra is finishing construction on another large array, the two-part Blythe project, a 235-megawatt installation covering more than three square miles. Surrounding the facility are not one but two fences. One of the fences extends 45cm below ground to prevent desert tortoises from burrowing beneath it.
But solar-energy backers fear that finding other suitable sites may be difficult under the federal plan. One charge is that some of the renewable-energy zones overlap with ecologically sensitive areas, such as sand dunes that are home to the Mojave fringe-toed lizard, and "microphyll woodlands," areas of taller trees, such as ironwood and palo verde, that are key for birds.
Danielle Mills, a senior policy adviser for the Large-scale Solar Association, recently toured one of these woodlands, which grow in desert washes that receive occasional flooding, near the Blythe array.
"Companies wouldn't come here in the first place, but on top of that, there's a requirement to avoid it," said Mills, whose organisation's members include NextEra and First Solar, which originally developed Desert Sunlight.
The BLM does not dispute that overlaps exist. Even within designated development areas, "there's still going to be some sensitive resources that are going to have to be avoided," said Mike Sintetos, who leads the BLM's renewable energy program in California. "We acknowledge that."
But Sintetos said the agency thinks there will still be "more than enough [hectares] available for the amount of megawatts that we think are going to come out of the desert."
The wind-energy industry is not happy with the plan, either. "I've never been so frustrated in my entire life. It was like beating my head against a brick wall for seven years," said Nancy Rader, executive director of the California Wind Energy Association.
But conservationists counter that California's two large utilities, Pacific Gas & Electric and Southern California Edison, have voiced support for the plan. And BLM California spokeswoman Martha Maciel adds that by channelling the solar industry to areas that are less conflict-prone, development will be a lot easier and litigation rarer. "It provides them a level of certainty that does not exist today," she said.
One key point of disagreement is just how much additional solar-energy infrastructure California, and the rest of the United States, will need - and how much should be sited on public lands.
Karen Douglas, one of the California Energy Commission's five members, argues that the 157,000ha should be more than enough - especially considering that the solar-energy industry will have the option to develop on private lands, too, and in other parts of the state, such as the San Joaquin Valley.
She described a scenario in which, assuming that California will need 20,000 megawatts of desert renewable-energy by 2040, 12 per cent of the federal lands designated under the plan would supply about 40 per cent of the goal. Private lands could then accommodate the rest, she said. "Large-scale renewable energy, especially on public land, is not the only game in town," Douglas said.
But the solar industry counters that it doesn't know how much private land will be available. Originally the plan was to work with California's counties to simultaneously obtain private land and allocate public lands. But later, the plan was split to pursue separate tracks, one factor that is now driving discord.
In the end, the debate marks a clear coming of age for the solar industry, a sign the growing appetite for the energy it produces will begin to conflict with other interests.
"There's no free ride with energy," said the Sierra Club's Taylor. "They all have costs, and large-scale solar is among them."