SMUD’s Microgrid Definition A Smart Grid concept “Integrated energy system consisting of interconnected loads and distributed energy resources which as an integrated system can operate in parallel with the grid or in an intentional island mode” Microgrids can vary in scope, size, and ownership Promote intentional islanding Cluster loads with Distributed Energy Resources. Have islanded DER units coordinate output to meet load demand. Load shedding when needed. Insure stability for multi-sourced systems. Seamless separation & automatic re-synchronizing with the grid. Design for high reliability Insure redundancy: n + 1 sources. Autonomous local control for fast events (No central controller) Minimize engineering errors/cost/and maximizes flexibility: use plug-and-play peer-to-peer models. Each DER unit is a voltage source. Multi-unit stability is insured through voltage vs. reactive power control. Communication between components is through frequency. DER output control uses power vs. frequency droop. Intelligent load shedding on low frequency. Automatic re-synchronizing using frequency difference between the island and Utility network. What a Microgrid is not One microturbine in a commercial building is not a microgrid, but DG A group of individual generation sources that are not coordinated, but run optimally for a narrowly defined load A load or group of loads that cannot be easily separated from the grid or controlled Does not have to have thermal (whereas CHP by definition has thermal) SMUD’s microgrid is an example of a small multi-facility scale microgrid and may applicable for some customers in Tanzania Source: US DOE/CEC Microgrids Research Assessment, Navigant Consulting Inc., May 2006 SMUD project demonstrates single-facility scale microgrid which could be feasible for C&I customers.

TecoGen Natural Gas Fired Generators SMUD Microgrid Project Overview Enabling Technologies 3-100kW natural gas engines 1200 amp-rated smart switch Seamless separation and isolation from utility grid and resynchronization Existing Systems 123-ton absorption chiller 1 new centrifugal chillers (500 ton) and existing chillers (600 and 200 ton) 4 existing natural gas fired boilers 15,000 ton-hour chilled water energy storage (760,000 gallons) The project has recently become operational and we are currently commissioning the systems. Major components to the project include these listed here. TecoGen Natural Gas Fired Generators