Microgrids
Microgrids are not a new construct. Thomas Edison began with a microgrid. They’ve been on college campuses and at medical centers for years, often based on combined heat and power systems… thermal power plants. The 15 MW power plant at Princeton University, built in the late 1990s, can switch between natural gas and biodiesel and supports the power, heating, and chilled water needs of all 150 campus buildings there. Harvard has been operating a steam loop on campus since 1916. In 2003 its Blackstone Steam Plant was upgraded to generate power and 400 degrees F steam at 100 psi. The 13,800-volt system now connects 250 buildings on Harvard’s Cambridge and Alston campuses and can island with 12.5 MW of power and a “black-start capable” microgrid.
This paper, however, is about a new and exciting form of microgrid. The microgrids that are the root of this paper – that combine renewable energy with energy storage — may become ubiquitous throughout North America, for campuses, for communities. They are a new form of microgrid, carbon-free microgrids. They do not replace utility grids; they complement them, adding key features, like onsite renewable power and emergency back-up systems. They’re mini grids that work daily and then that really spring into action when the big grid goes down. And they are enabled by advanced energy storage.