Brazil built a solar plant without a single battery and stores the sun’s heat in two giant pools, one hot and one cold

A Brazilian solar plant proves that energy can be stored without traditional batteries by using two pools.

Solar power is the leading installed renewable energy capacity worldwide, delivering significant volumes of clean power.

Despite this, global energy grids are increasingly struggling to balance fluctuating supply with uninterrupted demand for electricity.

To avoid economically unfeasible storage strategies while bridging long-term gaps, developers must seek alternative approaches.

Chemical batteries usually bridge this gap, but long-duration performance is limited by bottlenecks.

Will using alternative storage methods help prevent grid fluctuations?

How the most popular green source still fails to deliver

The cost of solar power has dropped by 60% over the past decade.

These lower costs were driven by manufacturing oversupply and a price war among major producers.

This was a primary factor in making solar the leading global renewable energy source.

In 2025, affordable panel prices drove a record of 664 GW of new installations.

Consequently, the total global capacity exceeded 3 TW.

Currently, it supplies approximately 9% of the world’s electricity demand.

Despite this great scale, the source alone cannot reliably maintain modern power grids.

Electricity consumption often peaks during early evening when solar generation plummets to zero.

Its inherently intermittent nature makes it impossible to balance fluctuations, which destabilizes grids.

Furthermore, fossil-fuel plants supply backup power after sunset, directly conflicting with climate targets.

This is why long-duration storage systems are essential to prevent massive curtailments and energy waste.

But conventional storage methods are no longer sufficient.

Chemical storage cannot satisfy long-term grid needs

Chemical battery storage has become synonymous with renewable energy facilities.

Lithium-ion batteries are the most widely used for rapid grid adjustments.

Despite their popularity, they fall short in meeting long-term power demands.

The majority of grid-scale installations supply electricity only up to four hours.

Storage capacity can be extended to eight hours or longer.

This will require doubling or quadrupling battery packs, which will drastically increase initial expenses.

Another major barrier is rapid degradation.

After 3,000 to 5,000 charge cycles, the batteries experience up to a 30% loss in capacity.

This necessitates more frequent replacements, which becomes expensive.

Furthermore, this approach faces critical mineral bottlenecks. Minerals such as lithium, nickel, and cobalt are geographically limited, raising supply chain and sustainability concerns.

To avoid economically unfeasible storage strategies while bridging long-term gaps, developers must seek alternative approaches.

RayGen designed a high-efficiency system that overcomes these obstacles.

A concentrated solar and thermal storage plant

Concentrated solar plants supply high volumes of power, but storage methods vary greatly among these facilities.

In Petrolina, Brazil, RayGen deployed a water-based thermal storage approach paired with concentrated solar.

The 1 MW pilot plant was developed in partnership with Axia Energia.

A multi-step thermodynamic operational process

Smart tracking mirrors focus sunlight 2,000 times onto ultra-efficient solar modules attached to a central receiver tower.

The sunlight is directly converted into electricity.

Simultaneously, waste heat is absorbed by a water cooling cycle to prevent the modules from burning out.

The hot water flows into an insulated hot reservoir at roughly 194°F. A separate insulated cold reservoir maintains water near 32°F.

As demand rises or the sun sets, the temperature difference between the pools drives an Organic Rankine Cycle heat engine.

Clean electricity is then produced for 8 to 48 hours or more.

The facility can deliver zero-degradation energy storage with a 30-year operational lifespan.

By combining concentrated solar with thermal hydro storage, grid challenges such as frequency control can be easily overcome.

Now, utilities can balance intermittent power generation 24/7.

Furthermore, this plant addresses the fundamental issues faced by chemical battery systems.

Global energy demand will continue to rise due to widespread digital adoption. To prevent power shortages and blackouts, thermal storage should scale up.

Ultimately, implementing this approach will pave the way toward affordable, long-duration grid security.