Energy efficiency measures are a priority in the near term to reduce the carbon intensity of maritime sector in the next years. Since 2017, IMO has been proposing policies to rapidly promote the adoption of cleaner technologies and fuels for oceangoing vessels. Lithium-ion batteries have been recently installed onboard smaller scale ferries and passenger vessels either as the primary energy source, or then as a hybrid solution. Various lithium-ion battery chemistries are available, with sources pointing at lithium nickel manganese cobalt oxide as the most feasible solution for ships. In this Chapter (Section 5.2), the authors focus their attention on the design, modeling, and control of maritime batteries, presenting and discussing real-life applications on sizing, modeling and control. Thermal energy storage (TES) technologies are focused on mismatching the gap between the energy production and consumption by recovering surplus energy during the generation to be used on periods of high demand. Although large amount of studies cover the application of TES technology in fields like renewable energies or industrial applications, very few authors evaluated the use of TES systems in ships to increase the efficiency of the engines and reduce their CO2 emissions. In Section 5.3, an analysis of the potential use of TES systems is presented, considering the heat and cold sources in different types of ships, and its use on board. Potential drawbacks of the use of TES on board ships, such as the integration with existing propulsion layouts, the requirements of weight and volume, are also discussed.@en