Solid-state thermal energy storage (TES) systems heat stacks of refractory bricks or ceramics to temperatures up to 800–1,200 °C using electric heaters, then discharge heat via air or gas loops into industrial processes. Properly designed, they can achieve high round-trip thermal efficiency and long lifetimes, enabling electrification and load shifting away from expensive gas and peak power.
- Operating temperature windows from 400–1,000 °C are realistic for most commercial concepts, with niche designs targeting up to 1,200 °C for metallurgy and ceramics.
- Round-trip thermal efficiency (electricity → stored heat → delivered process heat) can reach 70–90% depending on insulation, discharge temperature, and integration.
- For well-utilized systems, levelized cost of heat (LCOH) from brick TES can land in the 25–45 EUR/MWhth range where off-peak renewable electricity is abundant, often undercutting modern gas prices.
- Best-fit applications combine repeatable heat profiles, 4–12 hour shifting windows, and co-location with cheap power and constrained gas infrastructure.
1. Technology benchmarks: what solid-state TES really looks like
Brick-based TES systems store energy as sensible heat in dense ceramic or refractory materials. Compared with molten salts or phase-change materials, they offer simple construction, wide temperature windows, and relative robustness to cycling. At a high level, a system consists of an insulated chamber filled with bricks, electric heaters, fans or blowers, and heat exchangers connecting to process air or gases.
Typical commercial and near-commercial designs can be summarized as follows:
| Parameter | Mid-temperature TES module | High-temperature TES module | Reference: gas-fired furnace |
|---|---|---|---|
| Discharge temperature window | 400–650 °C | 700–1,000 °C | 500–1,200 °C |
| Typical module power | 5–20 MWth | 10–50 MWth | 5–40 MWth |
| Duration window | 4–8 hours | 6–12 hours | Not applicable (direct combustion) |
| Round-trip thermal efficiency | 80–90% electricity → heat in air | 70–85% higher losses at very high T | 85–95% fuel → heat |
| Expected design life | 20–25 years | 15–25 years | 15–20 years |
| Cycle life | >20,000 cycles | 10,000–20,000 cycles | Not typically specified |
For developers, the practical trade-off is between temperature, efficiency, capex, and integration complexity. Higher discharge temperatures can directly substitute for fuel-fired heat in many processes, but they increase materials stress and heat loss. Operating in the 500–800 °C range often delivers the best compromise between performance and cost.
2. Economics: from capex per kWhth to levelized cost of heat
Brick-based TES economics are driven by three core levers:
- Overnight capex per kWhth of storage and per kWth of charging/discharging power.
- Utilization (cycles per year and hours per cycle).
- Price spread between charging electricity and displaced fuel or peak power tariffs.
| Cost component | Mid-T TES (400–650 °C) | High-T TES (700–1,000 °C) |
|---|---|---|
| Storage media & vessel (EUR/kWhth) | 8–15 | 12–22 |
| Insulation & structure | 6–12 | 10–18 |
| Electric heaters & power electronics | 10–18 | 12–22 |
| Fans, blowers, ducting, HX | 6–12 | 8–15 |
| Engineering, project & contingencies | 8–15 | 10–18 |
| Total overnight capex (EUR/kWhth) | 38–72 | 52–95 |
When this capex is annualized over a 20-year life at 7–9% real WACC and 250–350 full cycles per year, the resulting capital recovery cost typically lands in the 8–18 EUR/MWhth range. Adding charging electricity, round-trip losses, and O&M yields indicative levelized cost of heat (LCOH) ranges such as:
The key takeaway: in systems with good utilization and access to low-cost electricity, brick TES can undercut gas-fired heat on an LCOH basis while also providing load shifting and CO2 reductions. In markets with flat or already expensive power, economics are tighter and electrification pathways such as heat pumps or direct electrification may be preferable.
Quantify TES economics with Energy Solutions tools
To avoid over- or under-estimating TES value, process engineers should run multiple price and utilization scenarios. Our tools help compare brick TES against gas, direct electric, and hybrid systems on a common LCOH and payback basis.
3. Integration with industrial processes
Successful TES projects are ultimately integration projects. The thermodynamics of bricks in an insulated box are straightforward; the challenge is matching the TES discharge profile to real process constraints, ramp rates, and product quality requirements.
3.1 Direct air or flue gas integration
Many systems blow air through hot bricks and then mix this hot air into combustion air or process air streams. This is particularly attractive for processes such as:
- Continuous ovens and dryers (food, textiles, paper).
- Low- to mid-temperature kilns (ceramics, refractories).
- Preheating combustion air for existing fuel-fired equipment.
3.2 Indirect loops and heat exchangers
Where process gases are corrosive or oxygen-sensitive, TES may instead heat an intermediate loop (air, nitrogen, or thermal oil) that then transfers heat via dedicated exchangers. This adds capex and minor losses but can simplify integration significantly.
3.3 Controls and EMS coordination
To fully exploit load shifting, TES must coordinate with an energy management system (EMS) that schedules charging in low-price hours and discharging into peak operations, while respecting production constraints. Integration with on-site PV, wind, and demand charges amplifies value but also increases control complexity.
Integration rule of thumb: if TES integration requires major process redesign or extended downtime, project risk rises sharply. The best early projects are bolt-on or parallel paths that can be tested without putting core production at risk.
4. Case study snapshots (indicative)
Public data on brick TES projects is still sparse, but indicative configurations illustrate the order of magnitude economics. The examples below are simplified but anchored in realistic ranges for capex, efficiency, and energy prices.
| Site | TES size | Application | Key outcomes |
|---|---|---|---|
| Food dryer with off-peak charging | 10 MWhth, 3 MWth charge/discharge | Shift dryer heat from night-time electricity to day production | 20–30% energy cost reduction, 30–40% CO2 cut vs. gas baseline |
| Ceramics kiln preheating | 30 MWhth, 8 MWth | Preheat kiln air to 600 °C with TES, reduce gas share | Gas consumption cut by 25–40%, improved temperature uniformity |
| District heat & steam hybrid | 50 MWhth, 12 MWth | Charge from surplus wind, discharge into steam network | Peak boiler output reduction, higher RES share in district heat |
In each case, the project’s success hinges on process compatibility and price spreads, not just on nominal efficiency. Sites with narrow operating hours or highly variable loads may struggle to reach the cycle counts needed to fully amortize capex.
5. Global perspective: where brick TES has the strongest rationale
TES potential is highest where three ingredients align:
- High and rising renewable penetration with frequent low or negative power prices.
- Large, repeatable industrial heat loads at 300–1,000 °C.
- Policy or market signals that reward electrification and CO2 reduction.
Europe, with its combination of expensive gas, growing carbon prices, and high renewable shares, is a clear early market. Selected regions in North America, the Middle East, and Asia with large industrial clusters and cheap solar will also see compelling TES economics, particularly when paired with hydrogen or electrified kilns.
6. Devil’s advocate: limits and failure modes
Despite its promise, solid-state TES is not a silver bullet. Key risks and limitations include:
- Under-utilization risk: if production schedules change or TES is oversized, cycle counts and economics deteriorate quickly.
- Integration downtime: tying TES into legacy plants can require outages and complex tie-ins that production teams resist.
- Uncertain long-term materials performance at very high temperatures and in aggressive atmospheres.
- Power capacity constraints: large TES chargers may stress grid connections unless coordinated with on-site generation and EMS.
Investor caution: treat early TES projects as demonstration-plus-commercial assets. Require clear monitoring plans, conservative assumptions on utilization, and explicit responsibilities for integration risk across OEM, EPC, and plant teams.
7. Outlook to 2035: role of solid-state TES in industrial decarbonization
By 2030–2035, brick-based TES could become a standard option in the toolkit for decarbonizing low- and mid-temperature industrial heat, much as heat recovery systems are today. Several trajectories are plausible:
- Base case: tens of GWhth of installed capacity globally, concentrated in food, paper, and ceramics, mostly for 400–700 °C applications.
- High adoption: widespread use in steel and high-temperature ceramics, with TES integrated into new electric furnaces and hybrid gas–electric systems.
- Limited adoption: if power prices remain volatile without predictable low-price windows, or if policy support for electrification is weak, TES deployment may be confined to specific showcase projects.
In most scenarios, TES sits alongside other tools — heat pumps, direct electrification, hydrogen, and CCS — rather than replacing them. The most resilient decarbonization pathways will mix these tools based on local conditions and infrastructure constraints.
8. Implementation guide: how to evaluate a TES project
For plant managers and energy teams, a structured evaluation approach can quickly distinguish high-value TES opportunities from marginal ones.
8.1 Screening questions
- What share of your heat load sits in continuous or regular campaigns vs. highly variable, batch operations?
- Do you have access to low-cost or negative-price power for at least 4–8 hours per day on average?
- Is your site already planning furnace or dryer upgrades where TES integration can be bundled?
- Can the grid connection, on-site PV, or wind support additional charging demand without major reinforcement?
8.2 Quantitative steps
- Map hourly heat demand and identify regular windows where TES could discharge.
- Characterize electricity and fuel price distributions and model realistic spreads.
- Size TES storage and power to match a portion of the load (e.g., 20–40%) rather than aiming for full substitution.
- Calculate LCOH and payback under conservative, base, and optimistic scenarios.
- Stress-test for low utilization years (maintenance, demand downturns).
8.3 Contracting and risk allocation
Most early TES projects will involve some form of performance guarantee or shared-savings mechanism. Aligning incentives across OEMs, EPCs, and plant owners reduces the risk that TES becomes an orphan asset when production conditions change.
9. FAQ: what industrial teams ask about solid-state TES
How does brick TES differ from molten salt storage?
Brick TES stores energy as sensible heat in solid refractory materials, while molten salt typically operates in the 250–565 °C range and requires pumps, tanks, and freeze protection. Brick TES can reach much higher temperatures, is relatively tolerant to cycling, and often integrates more directly with air and flue gas systems, making it better suited to industrial heat than many CSP-derived molten salt systems.
What round-trip efficiency should we assume?
For well-insulated systems operating at 400–700 °C with sensible integration, it is reasonable to assume 80–90% thermal round-trip efficiency from electricity to delivered hot air. At very high temperatures or with long storage durations, losses can push this towards 70–80%, so sensitivity testing is important.
Can brick TES fully replace gas-fired furnaces?
In some applications, yes, particularly in continuous processes where TES can provide most of the required heat and occasional gas firing covers peaks or contingencies. In many cases, TES will initially act as a hybrid solution, offsetting a portion of gas use while existing equipment remains in place.
How do we size TES relative to our load?
A common strategy is to size storage to cover a defined fraction of daily or shift-based heat demand (for example 20–40%) that can be reliably shifted. Oversizing TES can look attractive on paper but will undermine economics if utilization falls short of expectations.
What are realistic project timelines?
For brownfield sites, expect 18–30 months from early feasibility to commissioning, including integration engineering and outages. Greenfield projects or those bundled with major furnace upgrades can integrate TES more smoothly into existing timelines.