Electrical energy storage is considered essential for the future energy system to solve the intermittency problems caused by renewable energy sources such as wind and solar power . Among all the energy storage technologies, battery systems may provide flexibility  in a more distributed and decentralized way. In countries with deregulated electricity markets, grid-connected battery systems should participate in the electric power system and interact with other market players . 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. Additionally, a correct recognition of the barriers and advantages by all the stakeholders, including the system /  market operator, policy maker, investor, and project manager, is the key factor to promote battery storage technologies in grid-connected applications. For market and system regulators, more efforts are necessary to reduce the barriers from regulatory framework, promote pilot projects, and design appropriate market products or services that adequately address the flexibility provided by different technologies .
Electrical energy storage is considered essential for the future energy systems . Among all the energy storage technologies, battery systems may provide flexibility to the power grid in a more distributed and decentralized way. In countries with deregulated electricity markets, grid-connected battery systems should be operated under the specific market design of the country . In this work, using the Spanish electricity market as an example, 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 systems is still the main barrier for grid-connected battery systems . In Spain, for energy arbitrage within the day-ahead market, it is required that the battery wear cost decreases to 15 Euro / MWh to make the potentially profitable utilization rate higher than 20\%. Nevertheless, the potentially profitable utilization of batteries is much higher in the applications when higher flexibility is demanded. The minimum required battery wear cost corresponding to 20\% potentially profitable utilization time increases to 35 Euro/MWh for energy arbitrage within the day-ahead market and ancillary services, and 50 Euro/MWh for upward secondary reserve. The results of this study contribute to the awareness of battery storage technology and its flexibility in grid applications. The findings also have significant implications for policy makers and market operators interested in promoting grid-connected battery storage under a deregulated power market .
R
system to solve the intermittency problems caused by renewable energy sources such as wind and solar power
systems
A
to the power grid
R
participate in the electric power system and interact with other market players
be operated under the specific market design of the country
R
study,
work, using the Spanish electricity market as an example,
D
market designs of both wholesale markets and ancillary services in Spain are introduced, and the
R
storage are investigated under its specific market and regulatory framework. Finally, the
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
A
systems
R
, and the flexibility offered by such systems would be currently the most promising comparative advantage for this novel technology. Additionally, a correct recognition of the barriers and advantages by all the stakeholders, including the system
. In Spain, for energy arbitrage within the day-ahead market, it is required that the battery wear cost decreases to 15 Euro
A
MWh to make the potentially profitable utilization rate higher than 20\%. Nevertheless, the potentially profitable utilization of batteries is much higher in the applications when higher flexibility is demanded. The minimum required battery wear cost corresponding to 20\% potentially profitable utilization time increases to 35 Euro/MWh for energy arbitrage within the day-ahead market and ancillary services, and 50 Euro/MWh for upward secondary reserve. The results of this study contribute to the awareness of battery storage technology and its flexibility in grid applications. The findings also have significant implications for policy makers and
R
operator, policy maker, investor, and project manager, is the key factor to promote battery storage technologies in grid-connected applications. For market and system regulators, more efforts are necessary to reduce the barriers from regulatory framework, promote pilot projects, and design appropriate market products or services that adequately address the flexibility provided by different technologies
operators interested in promoting grid-connected battery storage under a deregulated power market