Thermal energy storage is turning hotel and data center cooling into dispatchable grid capacity. Here’s how IceBrick and CAISO point to the future of green tech.
Why thermal energy storage suddenly matters
Cooling loads from buildings and data centers now make up the single biggest slice of peak electricity demand in many hot regions. In California, those peaks are exactly what strain the grid, drive up emissions, and lead to emergency alerts.
That’s why Nostromo’s IceBrick thermal energy storage system quietly stepping into the CAISO wholesale energy market is a bigger deal than it looks on the surface. It’s a glimpse of how commercial buildings can stop being passive energy hogs and start acting like clean, flexible power plants.
For anyone thinking seriously about green technology, energy storage, and grid-interactive buildings, this is a blueprint worth studying.
This post breaks down how IceBrick works, what’s different about thermal energy storage, why CAISO market participation is a turning point, and how similar technologies can cut emissions and energy costs while supporting grid reliability.
What IceBrick actually does for the grid
Nostromo’s IceBrick is a behind-the-meter thermal energy storage system that shifts cooling demand off peak hours and turns buildings into dispatchable grid resources.
Instead of drawing huge amounts of electricity for cooling during hot afternoons, IceBrick:
- Makes ice at night when grid demand and prices are lower
- Stores that “cold” as frozen water in modular IceBrick units
- Uses the stored ice for air conditioning during peak hours, dramatically reducing the chiller’s electrical load
At the Beverly Hilton and the adjacent Waldorf Astoria in California, IceBrick has already shown what this looks like in practice:
- Participated in California’s Demand Side Grid Support (DSGS) program
- Delivered event reductions of over 200 kW during peak grid stress
- Now participates in the CAISO wholesale energy market as a standalone demand response resource, via integration partner Olivine
In plain language: two luxury hotels are now functioning like a small, flexible power plant. When the grid’s under pressure, their cooling load can be dispatched up or down and compensated through the market.
That’s the shift: cooling is no longer just a cost center – it’s an energy asset.
Why thermal ESS beats “just add more batteries” in many buildings
Most companies assume that decarbonizing buildings means solar on the roof and lithium-ion batteries in the basement. Those help, but they don’t always attack the biggest problem: cooling.
Here’s the thing about commercial load profiles: chillers and HVAC dominate peak demand. In data centers and large buildings, cooling can represent 30–60% of electricity use at peak times. If you ignore that, you’re leaving huge flexibility on the table.
How thermal energy storage fits into green technology
Thermal energy storage (TES) like IceBrick sits at the intersection of:
- Clean energy – by shifting loads away from fossil-heavy peak hours
- Smart buildings – via control systems that respond to grid signals
- AI and automation – optimizing when to charge (freeze) and discharge (cool)
Compared with conventional battery energy storage systems (BESS), a thermal ESS has some advantages for cooling-heavy facilities:
- Higher round-trip value for cooling: You’re storing exactly what you need (cold), not electricity you’ll later convert into cold
- Lower fire and safety risk: Ice and water instead of lithium-ion chemistry
- Long design life: Mechanical and thermal components typically age slower than many battery chemistries under similar cycling
- More predictable use case: Cooling loads are highly correlated with weather and occupancy, which are relatively straightforward for AI models to forecast
I’ve found that when you treat cooling as the primary flexible resource, the economics often look better than forcing everything through a battery.
When batteries still win
Batteries are still the right answer when you need:
- Fast, bi-directional power for frequency regulation
- Backup power for critical loads
- Multi-use cases like energy arbitrage, backup, and EV charging support
A smart green-technology strategy doesn’t pick one or the other. The most resilient and efficient sites combine thermal storage, batteries, and intelligent controls – and let AI decide what to dispatch when.
CAISO market participation: why this milestone matters
IceBrick’s participation in the CAISO market signals that thermal storage can finally be treated as a first-class grid resource, not just a behind-the-scenes efficiency upgrade.
Nostromo’s system at the Beverly Hilton and Waldorf Astoria is operating through Olivine’s ClimateResponse DER platform, which handles:
- CAISO market transactions
- Event dispatch coordination
- Performance measurement and valuation
This is more than a technical integration story. It shows three key shifts that matter for any business looking at green technology:
1. Behind-the-meter assets are now “market citizens”
The old grid model: big centralized plants supply power, buildings consume.
The new model: virtual power plants (VPPs) made up of thousands of behind-the-meter assets – batteries, smart thermostats, EV chargers, and now thermal ESS – respond dynamically to grid conditions.
IceBrick isn’t just reducing the hotel’s bill. It’s:
- Bidding into wholesale markets through an aggregator
- Providing dispatchable capacity, just like a power plant
- Getting paid for being flexible at the right times
2. Policy and finance are catching up
Two decisions have set the stage for thermal ESS in California:
- The US Department of Energy’s conditional commitment of up to US$305.54 million to support Project IceBrick, a VPP of up to 193 thermal storage systems in commercial buildings across California
- California’s DSGS program (even though funding’s now cut) showing that distributed load flexibility can reach 700 MW of enrolled capacity in a short timeframe
Lauren Nevitt of Sunrun called DSGS the largest VPP in the US – and probably the world. IceBrick participated in that ecosystem, and now graduates into full market participation.
This matters because once regulators and financiers have seen a technology at scale, the barrier for replication in other states and countries drops fast.
3. Software is the bridge between hardware and revenue
Olivine’s role is a good reminder: hardware alone doesn’t make a resource “grid-ready.” You need:
- Accurate forecasting of building load and grid signals
- Optimisation algorithms (increasingly AI-driven) to schedule charging and discharging
- Compliance with complex market rules
The reality? Most building operators don’t want to touch that complexity. Platforms like ClimateResponse absorb it, so the building sees simple price signals and performance payments, while the software handles the CAISO puzzle.
What this means for commercial buildings and data centers
Cooling is now a strategic asset for any large building or data center, not just an engineering afterthought.
Nostromo’s CEO, Yoram Ashery, put it bluntly:
“Cooling by commercial buildings and data centres is the single largest load on the grid, and making these large loads flexible and operable interactively with the power grid demonstrates how buildings and data centres can help the grid unlock existing capacity to serve new demands, while saving energy costs and enjoying more resilient and reliable cooling operation.”
Here’s how that translates into practical decisions.
If you own or operate large commercial buildings
You should be looking at thermal storage + smart controls if:
- Your building has high afternoon cooling peaks
- You’re in a capacity-constrained or high-price region (California, parts of Texas, Northeast US, etc.)
- You can participate in demand response, DSGS-style programs, or ISO/RTO markets through an aggregator
Potential benefits:
- Lower peak demand charges and better tariff optimization
- Revenue from grid services via aggregators
- Decarbonization progress without waiting for full electrification of everything
- Improved cooling resilience during grid stress events
If you’re planning or running data centers
For data centers, this story is even sharper. Cooling is often the swing factor for both energy use and community acceptance.
Thermal ESS can help you:
- Improve your effective Power Usage Effectiveness (PUE) during peak periods
- Reduce grid interconnection friction by presenting a more flexible load profile
- Support renewable integration by shifting energy use to times of high solar or wind production
- Back up commitments to 24/7 clean energy with dispatchable demand reduction, not just RECs on paper
Pair that with AI-driven controls, and you get a data center that’s not just “less bad” for the grid, but actively helpful.
How AI and smart controls turn TES into a true green technology asset
Thermal storage on its own is just hardware. It becomes powerful when it’s directed by intelligent software. That’s the piece that ties this story back into the broader Green Technology series.
The best-performing projects now combine:
-
Physical flexibility
- Thermal ESS like IceBrick
- Batteries where appropriate
- Controllable HVAC and ventilation
-
Digital intelligence
- AI models that forecast weather, occupancy, and grid prices
- Control systems that schedule when to freeze ice and when to discharge
- DER platforms that communicate with market operators like CAISO
-
Market access
- Aggregators or platforms (like Olivine) that know how to monetise flexibility
- Programs such as DSGS, capacity markets, or flexible load tariffs
For businesses, the opportunity is straightforward:
- You invest once in flexible infrastructure (like thermal ESS)
- You connect it to smart software that constantly optimizes
- You unlock a long-term stream of avoided costs and new revenue
There’s a better way to approach decarbonization than just buying more offsets or hoping the grid gets cleaner. Turn your existing loads into flexible, intelligent resources. Thermal ESS is one of the most direct routes to do that for cooling.
Where green technology leaders should go from here
Most companies get this wrong: they focus their entire sustainability strategy on supply (buy green power) and forget demand (make your load flexible). The IceBrick–CAISO story shows how powerful the demand side can be when you treat it as part of your energy portfolio.
If you’re responsible for energy, sustainability, or infrastructure strategy, a practical next step looks like this:
-
Map your cooling profile
- When are your cooling peaks?
- What’s your maximum kW demand from HVAC and chillers?
- How often do you bump into demand charges or grid constraints?
-
Assess flexibility potential
- Could some of that cooling be shifted earlier with thermal storage?
- Are there existing programs or markets you could join via aggregators?
- Do you already have a building management system that could integrate with TES?
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Engage with solution providers
- Thermal ESS vendors (like Nostromo’s category)
- DER aggregators and VPP platforms
- Consultants who understand both engineering and market rules
-
Design for revenue, not just savings
- Ask explicitly: How will this project earn from grid services over 10–20 years?
- Model multiple scenarios: demand response, capacity payments, time-of-use shifting
Green technology isn’t just about installing shiny hardware. It’s about designing systems – physical and digital – that cooperate with the grid, cut emissions, and support your business model.
Thermal energy storage like IceBrick is proving that cooling loads can be just as valuable as power plants. The organizations that internalize that now will be the ones with lower costs, stronger ESG stories, and fewer headaches the next time the grid hits its limits.