Compressed Air Energy Storage Patents

Compressed air energy storage (CAES) patents cover adiabatic and heat-recovery innovations; cavern and underground-storage innovations; liquid-air (cryogenic) innovations; and isothermal, expander, and system innovations — with IP held by advanced-CAES and liquid-air-storage developers (in the long-duration-energy-storage race to store renewable energy for hours-to-days cheaply). MAJOR CAES PATENT HOLDERS: HYDROSTOR: Advanced Compressed Air Energy Storage (A-CAES) — compressing air, RECOVERING and storing the compression HEAT in a thermal store (so no fuel is burned on discharge, unlike legacy diabatic CAES), storing the compressed air in a purpose-built water-compensated underground cavern (water maintains constant pressure), and a deep adiabatic-CAES estate. HIGHVIEW POWER: Liquid Air Energy Storage LAES — using off-peak electricity to liquefy air (cryogenic, −196 °C) stored in insulated tanks, then re-gasifying/expanding it through a turbine to generate power (storable anywhere, no geology needed) — the leading liquid-air estate. OTHERS: Corre Energy (salt-cavern CAES), Apex CAES and the legacy diabatic plants (Huntorf, McIntosh — old technology that burns gas on discharge), Augwind (hydro-pneumatic), Cheesecake Energy (compressed-air + thermal), and Storelectric. Adiabatic heat-recovery CAES, liquid-air storage, and underground cavern engineering are the core CAES patent domains — and the appeal is cheap, long-duration, geomechanically-durable storage using mature equipment.

Adiabatic and heat-recovery innovations; thermal-store innovations; underground cavern and pressure-compensation innovations; and compressor/expander and round-trip innovations represent core CAES patent domains — and recovering the compression heat (adiabatic) plus the air-storage method are the central differentiators. ADIABATIC / HEAT-RECOVERY PATENTS: capturing the heat generated when air is compressed and storing it (in a thermal store), then RETURNING that heat to the air before expansion (so discharge needs no fuel — the key advance over legacy 'diabatic' CAES, which burns natural gas to reheat the air, hurting efficiency and emissions) — Hydrostor A-CAES; the heat-recovery cycle, the thermal-store medium (water, oil, packed-bed gravel, molten salt), and the integration are key claims that determine round-trip efficiency. CAVERN / UNDERGROUND-STORAGE PATENTS: storing compressed air underground — salt caverns (leached, the legacy approach), hard-rock or lined caverns, and Hydrostor's WATER-COMPENSATED cavern (a water column maintains constant air pressure as air is added/withdrawn, keeping the compressor/expander at constant pressure for efficiency — a distinctive design); cavern construction, sealing, and geomechanics. COMPRESSOR / EXPANDER PATENTS: efficient multi-stage compression and expansion (turbomachinery), and constant-pressure operation. ROUND-TRIP / EFFICIENCY PATENTS: maximizing round-trip efficiency (the main CAES weakness historically) via heat recovery and constant-pressure design. Adiabatic heat-recovery cycles (fuel-free, high efficiency) and constant-pressure cavern designs are the highest-value CAES IP because they overcome legacy CAES's efficiency and emissions drawbacks.

Liquid-air (cryogenic) innovations; cold-recovery and integration innovations; isothermal-compression innovations; and thermal-storage and balance-of-plant innovations represent additional energy-storage patent domains — and liquid air (geology-free) plus isothermal compression are distinct approaches to cheap long-duration storage. LIQUID-AIR (LAES) PATENTS: liquefying air with off-peak power and storing it cryogenically, then pumping, re-gasifying, and expanding it to generate power — the liquefaction and power-recovery cycle (Claude/Linde-derived), insulated cryogenic storage, and crucially COLD-RECOVERY (storing the 'cold' released during re-gasification to make the next liquefaction more efficient — the key to LAES round-trip efficiency, Highview), plus integration with waste heat/cold from industry; LAES's advantage is it needs no special geology (storable anywhere). ISOTHERMAL-COMPRESSION PATENTS: compressing air slowly while removing the heat continuously (keeping temperature constant, which is thermodynamically efficient and avoids needing a separate hot store) — spray/liquid-piston and other isothermal approaches. THERMAL-STORAGE PATENTS: the hot and cold thermal stores (packed-bed, molten salt, water/oil) that capture and return heat/cold — shared with thermal-energy-storage. SYSTEM / BALANCE-OF-PLANT PATENTS: power-conversion, controls, multi-day discharge management, and hybridization (with renewables or industrial heat). Cold-recovery LAES (geology-free, efficient) and isothermal compression are the highest-value, most-differentiated air-storage IP because they address CAES's efficiency and siting limits.

CAES startup IP strategy must navigate Hydrostor A-CAES and Highview LAES estates, legacy diabatic-CAES prior art (Huntorf/McIntosh — decades old) and turbomachinery prior art (compressors/expanders/cryogenic liquefaction are mature industrial technology), the competition from batteries (short-duration) and other long-duration storage (flow, iron-air, thermal, gravity, pumped-hydro), geology/siting constraints (for cavern CAES), capital intensity, and a landscape where round-trip efficiency, cost, and duration decide success; understand that compression/expansion and liquefaction are mature prior art, so the durable IP is in adiabatic heat-recovery cycles, constant-pressure/water-compensated cavern designs, cold-recovery LAES, isothermal compression, and thermal-store integration, and that round-trip efficiency, cost, and demonstrated long-duration performance matter as much as patents; identify whitespace in adiabatic heat recovery, geology-free storage, isothermal compression, and efficiency improvements. CAES STARTUP IP STRATEGY: TURBOMACHINERY AND LIQUEFACTION ARE MATURE — HEAT/COLD RECOVERY, CAVERN DESIGN, AND ISOTHERMAL ARE THE IP: compressors, expanders, and cryogenic liquefaction are old industrial tech, so patent the adiabatic heat-recovery cycle, constant-pressure/water-compensated cavern, cold-recovery LAES, and isothermal compression — not the basic machinery; ADIABATIC HEAT RECOVERY (FUEL-FREE) AND COLD-RECOVERY LAES ARE HIGHEST-VALUE: legacy CAES burned gas and was inefficient; fuel-free adiabatic heat recovery (Hydrostor) and efficient cold-recovery liquid air (Highview) overcome the historic efficiency/emissions problems — the most valuable IP; GEOLOGY-FREE STORAGE (LAES) AND CONSTANT-PRESSURE DESIGNS EXPAND SITING/EFFICIENCY: liquid air needs no caverns (storable anywhere) and water-compensated constant-pressure caverns boost efficiency — both are distinctive, patentable design advantages; ISOTHERMAL COMPRESSION IS AN OPEN EFFICIENCY FRONTIER: continuously-cooled (isothermal) compression avoids separate hot stores and is thermodynamically efficient — patentable; ROUND-TRIP EFFICIENCY, COST, AND DURATION ARE EXISTENTIAL VS BATTERIES/OTHER LDES: CAES competes on cheap, long-duration, durable storage — measured efficiency/cost/duration strengthens patents and the business; CAPITAL AND (FOR CAVERN CAES) GEOLOGY ARE PARALLEL CONSTRAINTS: cavern CAES needs suitable geology and big capital — IP without siting/financing is incomplete; WHEN TO PATENT: NOVEL CYCLE/SYSTEM WITH MEASURED PERFORMANCE: file once a system shows measured results (round-trip efficiency % + duration hours + $/kWh + heat/cold-recovery effectiveness + cycle/calendar life) vs. legacy CAES/battery baselines — measured round-trip efficiency, duration, cost, and recovery effectiveness are the critical CAES IP metrics; KEY FTO CHECKLIST: Hydrostor A-CAES adiabatic heat-recovery thermal-store + water-compensated constant-pressure cavern; Highview LAES cryogenic liquefaction + cold-recovery + insulated storage; Corre Energy/legacy salt-cavern diabatic (Huntorf/McIntosh prior art); isothermal-compression spray/liquid-piston; packed-bed/molten-salt/water-oil thermal store; multi-stage compressor/expander turbomachinery (mature); cold-recovery liquefaction integration; geology-free siting; waste-heat/cold hybridization; battery/flow/iron-air/thermal/gravity LDES competition.