Provided are apparatus and methods for storing thermal energy. For example, an apparatus including comprising at least one phase change material, and a capsule containing the at least one phase change material. The capsule may be permanently or temporarily sealed to contain the encapsulation material. The encapsulation material includes at least one material that is chemically and physically distinct from the phase change material. The encapsulation material and phase change material are selected to store and discharge thermal energy at temperatures of greater than 400.degree. C. without capsule failure.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was developed with financial support from the Department of Energy, Government Grant Award Number DE-FG36-08G018150. The United States government may have certain rights to the invention.