CAES fired Natural gas combus on (CO2 emissions) The heat produced during compression phase is dissipated (low compression-phase efficiency)

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1 AG Mini-A-CAES/2-TES: Above Ground Compressed Air Energy Storage 1 to 10 MW combined with a two-level Thermal Energy Storage ( make Wind Farm / PV dipatchable ) Federico Santi, University of Rome

2 AG Mini A-CAES/2 TES Concept CAES is a well known energy storage technology (two existing plants in the world: US and Germany) Several research groups are exploring innovation in CAES techs (RWE/GE Adele, ESPC, SustainX, etc.) Our proposal AG Mini A-AES / 2 TES is an evolutionary CAES system with: Above Ground ( AG ) compressed air storage (not underground cavern, but steel tanks) Medium-Small Size ( Mini ) i.e. 1 to 10 MW, about 8 hrs charge / 2 hrs discharge (it can be modified) Adiabatic ( A-CAES ): heat produced during compression stored/used to heat air before expansion Two-level thermal energy storage ( 2 TES ), molten salt and pressurized hot water Adiabatic CAES concept: compressed air coming out from the storage system has to be heated before to enter in the air expander to generate electric power CAES fired Natural gas combus on (CO2 emissions) The heat produced during compression phase is dissipated (low compression-phase efficiency) A-CAES Heat stored in a TES system The heat produced during the compression phase is stored and then used for the power generation

3 The (Evolutionary) Idea Our idea is based on the following, simple 5 main milestones: Wind Farm (or PV) Grid We see 13 good reasons to choose AG Mini-A-CAES/2 TES for smart grids / balancing renewables

4 Above Ground Compressed Air Storage System Compressed Air Storage System: Steel-Pipes (42 o 48 ) H or V in a concrete building Alternative: Normal Steel Tank Design Specifications: Standard: EN Max pressure: 55Barg Max temperature: 100 C Corrosion: 3mm Material: P355 NH EN Storage Capacity: 0,14 to 14 Mm 3. Storage pressure up to bar In/Out Air Flow about 300 kg/s. System response time: few minutes Cost: about 40 M for 3 Mm 3 system High-Performance Compressed Natural Gas (CNG) Technologies Traditional Compressed Air Technologies

5 Above Ground Compressed Air Storage System Horizontal Configuration Vertical Configuration Surface CAES Vertical Configuration Possible Application in a 1200 MW CCGT Power Plant (Civitavecchia, Rome) AG CAES example (GE Gas Turbine, not A, not Mini, no TES )

6 Combining AG and TES: an Optimization Problem 50 MW Wind Farm + AG A-CAES example (charge 8 hrs eq., discharge 2 hrs eq.) Traditional Compressed Air Tanks Experimental TES: Concrete Blocks Comments: Low Efficiency (54%) Experimental TES High Cost of Traditional Compressd Air Storage Tank but Total Investment Cost (2000 /kw) less than NaS batteries Size optimized for medium-small wind farms and/or large PV plants Fast Response Time (few minutes) Capable to balance RES No siting problems (hydropumping, UG CAES, ) No cycling problems No fossil fuels No fire/explosion hazards No risks for the environment

7 Benefits: Low cost materials Flexible design Small exergetic losses Small energetic losses Different TES Systems: TES Phase Changing Material Diathermic Oil Molten Salt Pressurized water Concrete blocks Hybrid Solutions: Two-level Thermal Energy Storage MAIN ISSUE Super-heated water and concrete Super-heated water and molten salt Low efficiency due to high exegetic losses Can be used both as TES and heat transfer fluid but high cost, safety and environmental issues Low cost, but high solidification temperature Low cost, but low storage temperature Variable out temp., low efficiency High Temperature: Solar Grade Molten Salts Low Temperature: Pressurized Water Pressurized water and molten salt hybrid TES most promising solution solving the issues shown in the others

8 Two pressure levels plant scheme

9 Ex. Catalogue Components and Performances GE Turbo Expander Compression: 35% P / min response time < 5 min Generation: 20% P /min, response time < 10min 9

10 AG Mini-A-CAES/2 TES Cost Estimates One pressure level Min/max pressure 13/22 bar Roundtrip efficiency 63% Easier control strategy Lower cost Cost estimates (10 MW): 940 /kwh 2000 /kw Two pressure levels Min/max pressure 34/56 bar Roundtrip efficiency 64% Slightly more complex control Higher cost Cost estimates (10MW): 980 /kwh 2330 /kw Investment cost breakdown (CAPEX) Component 1 pressure level ( /kw) 2 pressure levels ( /kw) Heat exchangers % % Turbomachinery % % TES 29 1% 63 3% Compressed air tanks % % Contingency/civil works 182 9% % Total

11 AG Mini-A-CAES/2 TES Main Features 12,9% 4,1% 1,2% AG Mini A-CAES 2 TES 17,1% 64,6% Energy Balance Salt TES losses Water TES losses Air Tank energy losses Exhaust residual heat losses Useful energy Comparison with other ES technologies: pressure levels A- CAES Life cycles comparative 1 pressure level A- CAES NaS Battery Pb Acid advanced Battery Li-ion Battery pressure levels A- CAES Installation cost [ /kw] 1 pressure level A- CAES NaS Battery Pb Acid advanced Battery Li-ion Battery Enormous durability advantage compared to whatever battery Installation cost comparable with batteries, less than hydro More environmental friendly and safe than batteries Fully made by existing and well proved components, no R&D Flexible to be used in a wide range of applications Siting much easier than hydro-pump

12 AG Mini A-CAES/2 TES History / Status Jul. 2009/Jan.2010: Study of the maximum installable RES power capacity in the Italian electrical system AIEE / Energy Foundation (key-findings: storage convenient, 4 GW in GW wind/storage in 2030) Oct/Nov 2010: Proposal for a full-scal Wind + Above gound CAES demo project, discussed with ENEL (Donatini, Zulberti) Aug. 2010: Electricity Storage in Italy: a Long Term Cost-Benefit Analysis Conducted with a Markal-Times Model of the Italian Electrical System IAEE European Conference, Vilnius Aug. 2010/Jan.2012: N.6 M.Sc. Thesis in Energy Engineering about Above-Ground CAES/TES (Compressed Air Energy Storage with Thermal Enegy Storage) wind-farm integrated, Professors M.Cumo and F. Santi; simulation/optimization modelling Sept. 2011: start-up Celertech - financial advisor and business incubator for Smart Grid /ES technologies Jun. 2012: start-up StorAge - A spin-off company to accelerate the AG Mini-A-CAES/2-TES technology developement STATUS: Basic Engineering Design ready for several options, 1 to 10 MW Front-End Engineering Designed phased-up, to be finished within 6 months Venture Capital Interest Collected from Potential Industrial Partners NEXT-STEPS: First Mover (demo, 1 to 10 MW) Business model / regulation (market or tarifs?)

13 Conclusions AG Mini A-AES / 2 TES is an evolutionary CAES system with the following charactestics: Existing components already available on the market (zero time-to-market, no further R&D activity) Above Ground CAES (without any problem of siting) Medium-Small Size 1 to 10 MW (smart grid / dispatchable renewables oriented) Adiabatic (no needs for fossil fuels) Two-level TES, molten salt and pressurized hot water (high efficiency, low cost, safe TES) No fire/explosion hazardous No environmental concerns Flexible. Fast response to dynamic load (few minutes) during charge and discharge. No limits to the number, depth, frequency, duration of the charge/discharge cycles. Long lifetime, high IRR Low O&M cost (OPEX). Efficiency up to 65%, comparable to hydro-pump Investment Cost (CAPEX) lower than NaS and Li-Ion batteries AG Mini A-CAES 7/2 TES will play a major role in Energy Storage world market during the next 10 years

14 Thank You Federico Santi Rome University La Sapienza, M.Sc. Energy Engineering Professor Scientific Director of Italian Association od Energy Economists (AIEE) / Energy Foundation Energy Manager of the Italian Agency for Air Traffic Management Energy Manager of Port of Rome (Civitavecchia, Fiumicino and Gaeta) Managing Director of the independent consultant engineering company: Studio Santi Innovation in Energy Via Cavour Santa Marinella (RM) ITALY phone: mobile: federico.santi@studiosanti.eu