Connected Strategy for Hydrogen Value Chain ^ Top ^ 42 Figure 18 | Prosumer model AGGREGATOR An aggregator can operate many renewable DERs together, creating a sizeable capacity like that of a conventional generator (i.e., virtual power plant). As such, aggregators can then sell electricity or ancillary services in the wholesale market, or in the system operator’s ancillary services procurement. An aggregator enables smoother integration of DERs into the power system, by allowing them to provide energy to the wholesale market and ancillary services to the grid operator. Thus, aggregator contributes to the system’s flexibility. STEM is a California-based start-up with artificial intelligence technology that focuses on behind-the-meter energy storage systems and virtual power plants. It uses energy storage systems to reduce the cost of electricity for commercial consumers. The batteries are charged when the cost of electricity is low and discharged when the cost of electricity is high (typically during peak demand period). While traditional battery storage is used now, hydrogen will likely be adopted in the future. Stem can use its software to reduce the net demand of its customers, thereby reducing the demand of the whole area when the existing supply system cannot supply in the local area (Stem, 2019).