Before revision:  In this study, the market designs of both wholesale markets and ancillary services in Spain are introduced, and the barriers to grid-connected battery storage are investigated under its specific market and regulatory framework. Finally, the numerical and empirical analysis suggests that the high cycle cost for battery  is still the main barrier for grid-connected battery systems , and the flexibility offered by such systems would be currently the most promising comparative advantage for this novel technology.
After revision:  In this study, the market designs of both wholesale markets and ancillary services in Spain are introduced, and the barriers to grid-connected battery systems are investigated using utilization analysis. The concept of "potentially profitable utilization time" is proposed and introduced to identify and evaluate future potential grid applications for battery systems. The numerical and empirical analysis suggests that the high cycle cost for battery is still the main barrier for grid-connected battery systems , and the flexibility offered by such systems would be currently the most promising comparative advantage for this novel technology.