Temperature Abatement using Spray Injection and Metal Wire Mesh in Liquid Piston Compressor for Ocean Compressed Air Energy Storage Application

Abstract

Abstract One of the challenges in designing an Ocean Compressed Air Energy Storage (OCAES) system is achieving efficient compression and expansion of air. The rise of temperature during air compression results in significant loss of energy which leads to low storage efficiency. In this study, temperature abatement in liquid piston compressor using spray injection and metal wire mesh are investigated experimentally to improve storage efficiency. Water spray at different injection pressures and metal wire mesh of different surface areas and volumes were tested for heat dissipation inside the compression chamber. Results indicated that the water spray injection is useful to reduce the final temperature from 334 K to as low as 297 K for compression of air from atmospheric pressure to about 250 KPa when the injection pressure is 60 psi. For the more effective metal wire mesh among the inserts tested in this study, temperature abatement to a final temperature of 308K was observed. Compared to wire mesh inserts alone, the simultaneous use of the inserts and spray injection resulted in enhanced temperature abatement. Compared with spray injection method alone, temperature abatement improvement was observed when inserts of sparse density were used along with spray injection. Although wire mesh inserts distract the contact of water droplets with hot air, the simultaneous use of the two methods resulted in an increased effective surface area because the surface area added by the inserts is larger than the surface area lost by the droplets coming to contact with the inserts. When inserts with more compacted structures are used, the temperature abatement was less than the spray injection alone. This seems to suggest that the contact surface lost by the droplets is more significant than the extra surface area added by the inserts. Since the geometries of mesh inserts used in this study are different from each other, temperature increase patterns at certain pressure levels are compared. Clearly, spray injection improves compression efficiency to 95% from the base 80% efficiency of liquid piston compressor. This work uniquely highlights the further development of efficient air compression using spray injection and metal wire mesh.