Compressed Air Energy Storage Units for Power Generation and DSM in Korea

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Compressed Air Energy Storage Units for Power Generation and DSM in Korea *Sang-Seung Lee, **Young-Min Kim ***Jong-Keun Park, ***Seung-Il Moon, and ***Yong-Tae Yoon * Korea Electrical

1 Compressed Air Energy Storage Units for Power Generation and DSM in Korea *Sang-Seung Lee, **Young-Min Kim ***Jong-Keun Park, ***Seung-Il Moon, and ***Yong-Tae Yoon * Korea Electrical Engineering and Science Research Institute (KESRI), Seoul National University, Korea ** Korea Institute of Machinery & Materials (KIMM) ***School of Electrical Eng,, Seoul National University, Korea

2 Introduction Necessary of CAES Storing surplus power during the night not involved using a large scale power storage method Intermittent nature of solar isolation, wind, and waves make these unreliable energy sources Compressed Air Energy Storage (CAES) CAES Hybrid technology of power storage and generation High-power, long-term load-leveling applications For large or small load management For use as an emergency generator during power failure 2

3 Storage technologies The relationship between power rating and storage technologies CAES have developed small, medium and large units supplementary power storage systems, district heating supply systems 3

4 Compares various energy storage systems Capital cost, lifetime, output power densities, storage energy densities and losses in operation for some parameters of already developed storage systems. 4

5 CAES concepts (1) Ideal gas law PV = ηrt P : pressure, V : volume, T : temperature, η : number of moles, R : universal gas constant Simplified volume energy density 1 V dv 1 V V Evolume = ηrt = PV = P V V V V V V ln 0ln : pressure, V : initial volumes, V : final volumes P0 0

6 CAES concepts (2) net electrical efficiency Storage Efficiency = { P F η} E : power consumed, P : total power generated F : fuel supplied, η : conventional generation efficiency CAES system by subtracting the amount of energy generated by the fuel E

7 CAES system 6 Regenerator 1 2 Compressor 3 Combustion Chamber Qfuel =100 4 Turbine 5 Wnet = 34 W net General gas turbine system, which drives the compressor Wc =56 (0.62* WE) WE =90 Wc =56 WE =76 Wnet =76 (+42) Typical large scale CAES system Qfuel =100 ER = 42/56 =

8 Typical large scale CAES system Air is used to drive the compressor of a gas turbine CAES technology makes modification to the basic gas turbine (GT) technology Storage facility for the compressed air rock cavern, salt cavern, or porous rock created by water-bearing aquifers or as a result of oil and gas extraction Aquifers attractive as a storage medium compressed air will displace water, setting up a constant-pressure storage system 8

9 Efficiency of CAES system The general gas turbine uses 1/2~2/3 power of turbine axis output for the drive of an air compressor CAES system obtain 2~3 times the generation power in comparison to a gas turbine generation (utilization of the precompressed air) Additional generation output 42(=76-34) is produced in comparison to gas turbine generation Consumed compression work of 56 in advance and the storage efficiency corresponds to about 75%(=42/56) 9

CAES plants in the world Germany Huntorf 290MW CAES in Germany since 1978 (90% availability, 99% reliability) USA The Alabama Electric Co-operative built a 110-MW Plant

10 CAES plants in the world Germany Huntorf 290MW CAES in Germany since 1978 (90% availability, 99% reliability) USA The Alabama Electric Co-operative built a 110-MW Plant started to operate in May 1991, supplied power during peak demand periods First in the world to use a fuel-efficient recuperator. This recuperator reduces fuel consumption by 25%. 10

11 Development of CAES system Large-scale CAES limited by the availability of suitable sites Current research focused on human-made storage tanks Energy utilization of manmade compressed air storage generation system Wc =56 QCHP =50 Qfuel =100 WE =76 Wnet =76 (+42) ER = 42/56 = 0.75 (+0.9 Heat) Man-made Air Storage These systems have the merit of making use of waste heat by storing considerable amounts of heat generated under compression. 11

Non-fuel supply micro-caes Energy density in the micro-caes system of an Ericsson cycle in the case without heating the compressed air for power

63 kwh) (20 ) (20 ) 50 bar, 1 m 3 (59.4 kg) (Exg=5.43 kwh) Heat In 4.67 kwh (Exg=4.

12 Non-fuel supply micro-caes Energy density in the micro-caes system of an Ericsson cycle in the case without heating the compressed air for power production Hot Water (80 ), 86 kg Heat 5.97 kwh (Exg=0.54 kwh) Cold Water (-6 ), 171 kg Cool 5.19kWh (Exg=0.25 kwh) Heat Out 6.63 kwh (Exg=6.63 kwh) (20 ) (20 ) 50 bar, 1 m 3 (59.4 kg) (Exg=5.43 kwh) Heat In 4.67 kwh (Exg=4.67 kwh) Compression Work Expansion Work Use of cooling effect in the process of expansion of air for refrigeration heating of compressed air is necessary for obtaining much more power (approximately 3 times) from the stored compressed air

13 Fuel supply micro-caes Energy density in the micro-caes system of an Ericsson cycle in the case with heating the compressed air for power production Hot Water (80 ), 86 kg Heat 5.97 kwh (Exg=0.54 kwh) Fuel Supply 17.7 kwh (Exg=17.7 kwh) Heat Out 6.63 kwh (Exg=6.63 kwh) (20 ) (700 ) 50 bar, 1 m 3 (59.4 kg) (Exg=5.43 kwh) Heat In 15.5 kwh (Exg=15.5 kwh) Compression Work Expansion Work Air compressor require two or more stages; intercoolers and aftercoolers to achieve economy of compression and reduce moisture content Compressor ; auxiliaries to regulate and control changeover from generation mode to storage mode. 13

14 Improve of micro-caes Improve the energy efficiency of the micro-caes, the multistage compression for intercooling is needed due to the high pressure ratio Idea of applying Ericssion cycle to micro-caes without multistage of compression/expansion Method of cooling air during compression by spraying liquid (such as water or oil) into the inlet port of the compressor can be used Injected liquid is separated in a separator after compression allowing it to be used for the recovery of waste heat and later for residential heating 14

15 UPS Compressed Air Cylinders Thermal Storage Providing several seconds of bridging power Hot thermal oil with electric heater Supercap Separator UPS Scroll Expander M/G AC/DC Compressor Auxiliary generation technique of an uninterruptible power supply (UPS) during a power failure 15

16 Demand growth rate Power system in KOREA 1990 s, posting an average increase of 10% Demand is predicted to show a continuous annual growth rate of more than 4~5% Generation sector of Korea Electric Power Corporation (KEPCO) was split up into six structurally separate generation companies 16

17 CAES prospects in KOREA (1) Demand-side management (DSM) any activity adopted by a utility that ultimately changes the utility s total system load curve Six generic load shape objectives illustrate the range of possibility 17

18 CAES prospects in KOREA (2) Average growth rate 2.5% per annum from 2004 to 2017 Increased rate of DSM represents residential as 2.5%, commercial as 3.6% and industrial as 2.3% Average growth rate of peak demand after DSM 2.7% per annum from 2004 to 2017 Class Before DSM 259, , , , ,732 After DSM Residential 57,189 68,260 74,172 77,491 78,635 Commercial 86,023 99, , , ,052 Industrial 150, , , , ,799 Total 293, , , , ,486 Electricity sales before and after DSM Storage and utilization time of CAES are determined by KEPCO load curve patterns over an entire day 18

19 Conclusion (1) CAES (compressed air energy storage) units, and reflected on a plan for DSM (demand-side management) for the prospects in KEPCO. New substituted technology not only for large or small load management but also for an emergency generator during power failure. CAES for the dual-purpose applications of supplementary power generation and a district heating supply system that is designed as an underground cavern or a modular-type pressurized vessel with large and small container. 19

20 Conclusion (2) CAES utilization time by the power between a lower limit and upper limit by the KEPCO load curve patterns over an entire day. Ericsson cycle of an isothermal compression/expansion to a micro-caes utilizing a wide heat transfer area and very good heat transfer characteristics. New technology not only for air storage of load management but also auxiliary generation of an UPS (uninterruptible power supply) under a power failure. 20

Storage Technologies for Renewable Energy

Storage Technologies for Renewable Energy Joseph H. Simmons and Ardeth M. Barnhart Co-Directors AzRISE The Arizona Research Institute for Solar Energy University of Arizona http://www.azrise.org AzRISE