Global Distributed Energy Virtual Power Plant Market Size, Share, Growth & Industry Analysis By DER Type (Battery Energy Storage Systems, Solar PV Plus Storage, Demand Response Loads, EV Smart Charging & V2G, Distributed Generation), By Application (Ancillary Services, Energy Arbitrage, Capacity Markets, Demand Response, Renewable Integration), By Deployment Model (Utility, Aggregator, VPP-as-a-Service) Industry Trends & Forecast 2026–2034