CERAWeek: Solar tech to fight climate change-linked energy cuts

Far from being unreliable, solar power can be paired with microgrids to keep lights and power on when severe weather strikes or even turned into hydrogen for use as energy storage, according to executives with a pair of startups presenting at the CERAWeek by IHS Markit conference.

Power supplies could become more resilient, for example, if utilities install more self-sufficient solar networks to supply neighborhoods, said Sunnova Energy Chief Marketing Officer Michael Grasso.

A solar power array that feeds a single home's nanogrid could be "pooled" with several hundred others to form a microgrid. Additional renewable energy sources could be added so that the utility can operate the microgrid as an independent unit, providing power back-up and cost-reducing services.

The neighborhood-level, solar-powered microgrid has benefits for both energy consumer and energy producer. "The consumer at the nanogrid at the grid's edge, they're getting the benefit of this renewable energy. They're helping decarbonization, and they're getting the benefit of economic savings," said Grasso.

"We know they're getting that energy resiliency, which is more and more critical with all of the weather effects that we're seeing across the [US] and around the world, whether it's hurricanes, or the most recent freezing or cold that prevented centralized resources from the district from getting to these consumers when they needed them the most," said Grasso.

Texas' recent spell of arctic weather, where surges in household demand correlated with widespread blackouts, is just one example of the energy resiliency problems that solar microgrids could prevent.

As well as being useful in bad weather, the solar microgrid lets the utility do away with costly network upgrades while adding power generation as the population it serves grows, according to Grasso. It also prevents the utility from having to regularly address grid instability or frequency problems caused by uneven population growth or increased use of distributed solar panels.

Cheap green hydrogen — from rocks

Bill Gates-backed startup Heliogen is another technology newcomer targeting solar-sourced energy redundancy, either as imported hydrogen that could serve as fuel for gas-fired power plants or as domestic reserves of stored energy, enabling renewable energy to end up in places with high demand.

Heliogen CEO Bill Gross explained the concept of a sunlight refinery, a robotically-assembled concentrated solar power (CSP) plant which produces green hydrogen at a cost of $1.88 per kg, making it competitive with hydrogen from natural gas at a cost of $2.20 per kg. "We develop very, very low-cost energy storage that uses hot air and rocks at high temperature, 1,000 degrees Centigrade, to dramatically reduce the cost of energy storage," said Gross.

A key reason that Heliogen's production methodology is cheaper than other solar-sourced green hydrogen plants being trialed today is that it heats rocks to let the plant work overtime at night, increasing its capacity factor. "Typical solar panels are in the 21% to 22% capacity factor range ... We have achieved [an] 85% plus capacity factor," said Gross. "With our system, we're converting the photons to high-temperature heat. When the photons stop, i.e. when the sun goes down, the heat stays. We hold on to that heat in high-temperature rocks, so we can keep on producing power."

While Heliogen's production of hydrogen is relatively cheap, today's hydrogen transport and scale hurdles could impact its cost.

The startup is seeking partners to increase the scale at which its green hydrogen can be produced, said Gross. "We need to invest in many breakthroughs to make this happen. I've shared with you one technology that we've built at Heliogen. We would love to work with you and partner to make this happen at scale."

Posted 04 March 2021 by Cristina Brooks, Senior Journalist, Climate and Sustainability