CHEX

A water battery for renewable energy

CHEX stores surplus solar and wind power as compressed gas and returns it through water turbines when the grid needs it. Competitive from 6 to 8 hours of storage, and more cost-effective the longer it runs.

Talk to our team See how it works
How CHEX Energy Storage works Schematic cross-section. Surplus solar and wind power drives a compressor that stores gas in an underground cavity such as an abandoned mine. When energy is needed, the gas expands and pushes a closed circuit of water through a low-speed turbine. A CHEX turbine, centered between the two tanks, sends electricity to the grid. Surplus solar and wind Compressor Compressed gas storage abandoned mine, depleted reservoir or well Electricity to the grid Low-speed water turbine closed water circuit
Simplified diagram. Gas is stored when there is surplus power and released when demand rises.
where CHEX becomes competitive
6–8+hours
maximum round-trip efficiency
70%
scalable power range
1–200MW
design lifetime
50–60years
CO2 avoided per MWh stored
~300kg

Design values of CHEX Energy Storage.

How CHEX Energy Storage works

Like a hydroelectric dam, without the river or the valley. In CHEX, gas pressure takes the place of height. Think of it as a compressed-air battery, but with water.

  1. Charge

    The energy to be stored is converted into gas with a compressor.

  2. Store

    The gas can be stored in tanks, abandoned mines or wells, or in liquid form, depending on what suits the site best.

  3. Generate

    When the energy is needed again, the gas is released into CHEX, and its water turbine recovers up to 70% of it.

Thumbnail for the video: What is Chex? Compressed hydro energy storage system

Watch the explainer video

How CHEX solves renewable energy surplus and curtailment.

The liquid piston principle behind CHEX is described in a peer-reviewed paper, Aliaga et al., Applied Energy, 2024, co-authored by Dr. Christian Romero.

Inside the CHEX facility: pressure tanks, piping and the control panel of the 10 kW working unit
Inside the CHEX facility. Pressure tanks, piping and the control panel of the 10 kW working unit.

How CHEX compares

Each storage technology has trade-offs. CHEX is built for long duration, long service life and existing sites, without chemical storage materials.

Typical values for each technology category. CHEX values are design values.
CHEX Energy Storage Lithium-ion batteries Pumped hydro Conventional compressed air
Free of chemicals and fuel Yes No Yes Partlysome plants burn natural gas
Works without special geography Yescan reuse abandoned mines and wells for higher capacity Yes Noneeds two reservoirs at different heights Yescan also use suitable caverns at larger scale
Storage duration 8+ hoursmore cost-effective the longer it runs 1 to 4 hours 6 to 12+ hours Several hours to a day
Service life 50 to 60 years 10 to 15 years 50+ years 30+ years
Round-trip efficiency Up to 70% 85 to 90% 70 to 80% 40 to 70%
Thumbnail for the video: The world's largest air battery just switched on

Compressed-air storage is already a reality

Large compressed-air plants already store energy for the grid. CHEX builds on the same principle, with water turbines and existing underground sites, increasing capacity and durability while making maintenance easier.

Where we are

From university research to the first commercial project.

  1. Research

    Completed

    Concept and first models developed at USM and CCTVal.

  2. Patents

    Completed

    Granted in Chile, Argentina, Australia and Europe (19 countries). Pending in the United States and Morocco.

    View the granted European patent

  3. Working unit

    Completed

    A 10 kW working unit has been built and tested.

  4. Industrial-scale project

    In progress

    In talks with companies to build the technology at industrial scale.

  5. First commercial project

    Planned

    The first commercial installation, following the industrial-scale project.

  1. CHEX SpA is founded in Valparaíso.
  2. ANID Startup Ciencia. Awarded USD 100,000 in milestone-based funding.
  3. AWS Clean Energy Accelerator. Selected for the global program. European patent granted. Patent EP3693568 covers the CHEX system across 19 countries.
  4. Working unit completed. Construction of the 10 kW working unit is finished. Avonni Award, Energy category. A leading innovation award in Chile.

Sites and partners we are looking for

CHEX can store its gas in existing mines, reservoirs and wells. That means less new construction and a new use for closed industrial sites.

Thumbnail for the video: CHEX Energy for Oil, Gas, and Mining

  • Renewable generators

    Store the energy lost to curtailment and sell it when it is worth more.

  • Mining companies

    Turn a closed mine into a storage asset instead of a closure cost.

  • Oil and gas operators

    Give depleted reservoirs and inactive wells a second life as storage.

  • Grid operators and utilities

    Long-duration flexibility as renewable generation grows.

  • Investors and pilot partners

    Help take a patented, working technology from a 10 kW unit to industrial scale.

  • See your organization here?

    Tell us about your site or project and we will explore how CHEX fits.

    Contact us

From the lab in Valparaíso to the market

CHEX Energy Storage was developed at Universidad Técnica Federico Santa María (USM) and the Centro Científico Tecnológico de Valparaíso (CCTVal), in a team led by Dr. Christian Romero.

CHEX SpA was founded in 2018 to take that research to market.

CHEX also holds a triple impact mission, combining environmental, social and economic goals.

Dr. Christian Romero

Co-founder and Chief Executive Officer

Leads scientific and engineering development. A solid-state physicist from KU Leuven with over 1,000 citations, he is Sub-director and a Board member of CCTVal, where he directs the energy storage program. He has founded two companies and received the 2024 Avonni Award in Energy.

Google Scholar · LinkedIn

Laurentzi de Sasia Rodríguez

Co-founder and Chief Commercial Officer

Leads strategy and commercial development. He opened the first Intel office in Chile, leading it for almost 20 years, and has since focused on renewable energy, including hydrogen storage and combustion.

Alex Garay

Chief Technology Officer

Leads technology development. An engineer with 20 years of experience in industry, mining, defense and energy, he connects design, prototyping, validation and industrial implementation.

LinkedIn

Lars Olrik

International Advisor

Advises on international expansion.

Recognition and partners

Press and mentions

Frequently asked questions

What is CHEX Energy Storage?

CHEX Energy Storage is a long-duration energy storage technology developed in Valparaíso, Chile. It stores surplus electricity as compressed gas. When energy is needed, the gas expands and drives a fixed volume of water through low-speed turbines that generate electricity. It works like a virtual dam or a water battery.

How long can CHEX store energy, and how efficient is it?

CHEX becomes competitive with batteries at around 6 to 8 hours of storage, and its cost per unit of energy keeps falling as storage duration grows. Round-trip efficiency is up to 70%.

Why does CHEX get more cost-effective with longer storage?

Adding hours mostly means storing more gas, in larger tanks or in existing mines and wells, rather than adding more machinery. Each extra hour of storage costs less than the last.

How does CHEX compare with lithium-ion batteries?

Lithium-ion batteries are efficient and well suited to a few hours of storage. CHEX becomes competitive from around 6 to 8 hours and grows more cost-effective with longer durations, with a design lifetime of 50 to 60 years and no chemical storage materials, so it produces no chemical waste and no direct CO2 emissions during operation.

How does CHEX compare with pumped hydro?

Both generate electricity by moving water through turbines. Pumped hydro needs two reservoirs at different heights and the right geography. CHEX replaces height with gas pressure in a closed water circuit, so it can use tanks or existing underground sites.

How is CHEX different from conventional compressed-air storage?

Conventional plants release compressed air through air turbines, and some burn natural gas to reheat it. CHEX uses the expanding gas to push water through durable low-speed water turbines, and it can store the gas in abandoned mines, depleted reservoirs and inactive wells.

What sizes can a CHEX project have?

The technology scales from 1 MW to 200 MW, from industrial sites to grid-scale projects.

What gas does CHEX use?

CHEX can use different gases, including CO2, chosen for the conditions of each project.

Is CHEX safe?

CHEX uses industry-tested components such as tanks, valves and turbines, common in other industrial applications. The system holds no chemical storage materials and operates as a closed water circuit.

How much water does CHEX need?

CHEX uses a closed water circuit with a fixed volume of water. The same water is reused in every cycle, so the system does not need a continuous water supply, which makes it suitable for dry regions.

How long does installation take?

Installation typically takes between 1.5 and 2 years, depending on the project's size and site conditions.

What stage of development is CHEX in?

The technology is patented, and a 10 kW working unit has been built and tested. CHEX is now in talks with companies to build the technology at industrial scale.

Is the technology patented?

Yes. CHEX Energy Storage is patented in Chile, Argentina, Australia and Europe, where European patent EP3693568 covers 19 countries, including the United Kingdom, Germany and Spain. Applications are pending in the United States and Morocco.

Who developed CHEX?

A team of physicists and engineers from Universidad Técnica Federico Santa María (USM) and the Centro Científico Tecnológico de Valparaíso (CCTVal), led by Dr. Christian Romero. CHEX SpA was founded in 2018 by Dr. Romero and Laurentzi de Sasia Rodríguez to bring the technology to market.

Talk to our team

Tell us about your project, your site or your grid challenge. We will get back to you.

Write to us
Office
General Bari 699, Valparaíso, Chile. View on map
Hours
Monday to Friday, 9 am to 5 pm, Chile time
Email
contact@chexenergy.com