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"?

All four listed technologies are considered "Distributed Energy Resources" (DERs).

Distributed Energy Resources are small-scale, modular electricity generation or storage technologies located close to the load they serve, typically ranging from a few kilowatts to 50 megawatts. They can be connected to the grid at the distribution level or operate independently.

1. Battery storage: Allows for electricity generated from various sources (including renewables) to be stored and dispatched when needed, often located at homes, businesses, or grid substations.

2. Biomass generators: Small-scale power plants that convert organic matter into electricity, often located near the source of biomass or users.

3. Fuel cells: Devices that convert the chemical energy of a fuel (like hydrogen) into electricity through a chemical reaction, often used in smaller, localized applications or vehicles.

4. Rooftop solar photovoltaic (PV) units: Solar panels installed on individual buildings to generate electricity for local consumption or to feed back into the grid, a classic example of distributed generation.

All these technologies fit the definition of DERs as they are decentralized, relatively small, and can be integrated into the distribution network or directly serve a local load.