Consider the following: 1. Battery storage 2. Biomass generators 3. Fuel cells 4. Rooftop solar photovoltaic units How many of the above are considered "Distributed Energy Resources"?

Answer: D. All four are considered Distributed Energy Resources (DERs). DERs are small-scale energy generation or storage technologies located close to where energy is consumed, as opposed to centralized utility-scale power plants. They typically connect to the distribution grid. (1) Battery storage: classic DER — provides energy storage and grid services at consumer or distribution level. (2) Biomass generators: small-scale generators using agricultural or organic waste; widely used DER especially in rural India. (3) Fuel cells: stationary fuel cells used for backup or primary power at building or industrial scale qualify as DERs. (4) Rooftop solar PV: the most widespread DER globally — distributed generation directly at the consumer site. All four qualify, hence D. Source: Ministry of Power / IRENA / IEA distributed energy resource definitions.