Why Christie Obiaya believes solar thermal is key to the energy transition

Christie Obiaya, CEO of solar thermal producer Heliogen, discusses why she feels this technology will play a key role in abating the greenhouse gas emissions of industrial sectors and explains why its energy is more easily stored than that of other renewables such as wind or solar PV.

While the global economy is undergoing a radical energy transition, large parts of it remain poorly positioned to reach net zero.

Bill Gates has observed that electricity generation, one of the easiest parts of the economy to decarbonise, accounts for only 25% of greenhouse gas emissions per year, calling this the “75% problem” in his blog, Gates Notes, in 2018.

Around the same time, Gates invested into a solar thermal energy start-up named Heliogen [HLGN]. He described the company’s artificial intelligence (AI)-driven solar thermal technology as a “promising development in the quest to one day replace fossil fuel”.

Solar thermal technology differs from solar photovoltaic (PV) technology because, rather than convert sunlight directly into electricity, it uses a bank of mirrors (heliostats) to concentrate the sun’s rays towards a receiver. This can heat to over 1,000°C thanks to AI optimisation of the mirrors’ positioning. 

Heliogen is now a publicly listed company on the verge of rolling out its technology commercially. Its CEO Christie Obiaya spoke to Opto Sessions last week, and shone some light on why, of all the sources of renewable energy, solar thermal has the most potential to radically accelerate the energy transition.

Hard-to-abate sectors

“One fifth of the world’s energy consumption today goes towards creating heat for industrial processes,” Obiaya told Opto Sessions. “Today, that’s done by burning fossil fuels like coal and natural gas.”

According to McKinsey, the production of steel and cement together account for approximately 14% of global CO2 emissions. While carbon capture and storage technology (CCS) is one potential means of decarbonising the industrial sector, it is a relatively immature technology which faces economic hurdles to widespread adoption.

The other solution is to switch to low-emission processes or fuels, such as hydrogen. Heliogen is preparing to produce green hydrogen using its solar thermal technology in partnership with Bloom Energy [BE]. The technology lends itself particularly well to supporting industrial processes that require intense amounts of heat.

“There aren’t that many current renewable energy solutions that easily lend themselves to displacing fossil fuels for heat,” said Obiaya. 

For example, Heliogen’s technology can produce steam at temperatures of up to 300°C. This has applications across industries, including mining, chemicals manufacture, and the extraction of oil and natural gas.

Heliogen’s green steam solution is “modular and can be scaled down to fit on a customer's site”, Obiaya told Opto Sessions. It offers cost efficiencies over generating industrial heat using fossil fuels.

Energy availability and storage 

There is also the question of energy availability and storage, another characteristic that makes solar thermal energy a particularly attractive source even when compared to other renewables.

“It's not just about creating clean power and clean electricity,” says Obiaya.

“When you talk about wind power, for example, if you're in a place of good wind resource, it very easily lends itself to low-cost energy in the form of power and electricity.” Elsewhere, however, there are difficulties in balancing the demand for power and electricity with supply, given that winds are variable.

Solar thermal offers solutions to these challenges. For example, steam generated via solar thermal energy can store that energy in a steam accumulator, allowing industrial processes powered by the sun to run at night. Alternatively, solid media storage heats solid objects, such as ceramic particles, and then stores them in an insulated silo.

Because heat energy is storable, solar thermal even offers advantages over PV generation.

“The US desert in the southwest has really low solar PV prices at midday,” Obiaya told OptoSessions. However, storing the energy generated during this peak requires batteries, which are costly.

“The kinds of customers that find our solution very compelling are ones that need some form of dispatchable energy when the sun's not shining, or the wind’s not blowing.”

One source among many

Naturally, Obiaya does not claim that solar thermal alone can tackle the issue of climate change.

“Every form of renewable energy will have its place in the energy transition,” she told OptoSessions. This point was underlined by research from Imperial College London, which showed that wind became the UK’s largest source of energy for the first time over the initial three months of 2023.

However, solar thermal offers key advantages over other forms of renewable energy generation, which could make the technology a key component in the global energy mix as the transition gathers pace.