The microgrid is defined in the Smart Grid Dictionary as “A small power system that integrates self-contained generation, distribution, sensors, energy storage, and energy management software with a seamless and synchronized connection to a utility power system and can operate independently as an island form that system.” The definition goes on to describe additional characteristics, but you get the gist of it. Microgrids have the potential to substantially change utility operational and business models by putting distributed generation (DG) and distributed energy resources (DER) like energy storage into the distribution grid. Microgrids, with their reliance on DG and DER, can make us energy locavores – consuming electricity that is locally produced. And that means a smaller carbon footprint since no electricity is lost in long-distance transmission.
However, there are more unknowns than knowns about how to manage microgrids in utility distribution grids. I had the opportunity to learn about the San Diego Gas and Electric (SDG&E) microgrid project challenges in conversation with Vic Romero, Director of Asset Management and Smart Grid Projects. According to him, the greatest challenges are the new microgrid technologies and new applications of existing technologies. “We want to learn how these technologies work together when integrated into our distribution grid because this is the way of the future,” he explained.
There are nine microgrid projects that received funding from the Department of Energy (DOE) to explore their potential to build reliability into distribution networks. SDG&E is hosting one of the demonstration projects in Borrego Springs, receiving $7.5M from the DOE as well as $2.8M from the California Energy Commission (CEC) along with their own funds and contributions from vendor partners.
Borrego Springs is a small community with residents who are enthusiastic adopters of rooftop solar with 600-700 kWs of DG already deployed. More importantly, it offers a substation that can become part of the microgrid and factor into experiments of grid connects/disconnects in islanding exercises. Islanding is the situation when the microgrid is deliberately cut off from the utility distribution grid and runs on stored electricity plus locally produced electricity.
Energy storage is a key technology in the Borrego Springs microgrid. SDG&E plans to install a 500 kW battery at the substation and 2 25kW batteries for community energy storage. Some residences will also receive utility-supplied batteries that are capable of delivering 8 kWhs of electricity. There are two important microgrid applications for batteries. They can be used for islanding, delivering electricity when generation sources are offline. Batteries can also be used to firm steady and intermittent sources of power from voltage disruptions – drops and surges – in the distribution grid. SDG&E will test both applications once the energy storage technologies are installed.
SDG&E also plans to recruit 125 residential volunteers to participate in an experiment that will deliver electricity price signals over a broadband connection to their Home Area Networks (HANs) and selected devices. The devices include pool pumps, electric vehicles (EVs), thermostats, solar panels, and batteries, which will respond to price signals sent by a price-driven load management (PDLM) system or what others might call an enhanced demand response management system.
The most ambitious and revolutionary aspects to this microgrid project are two custom-built software applications. The first is the PDLM system that will supply price signals to residential devices to trigger actions based on those prices. The second is a microgrid management system that Vic Romero identified as “the next-generation Distribution Management System (DMS).” Unlike today’s DMS solutions, microgrid management systems will have more interactions with sources of generation – both utility and consumer-owned; interactions with energy storage technologies and their management systems, and communications with PDLM systems. Is this DMS on steroids? Perhaps. Are there risks in using the first release of custom software? Yes, but this is a demonstration project and experimentation is encouraged.