Electricity’s Future, Part III: Microgrid

One piece of technology that could have the biggest influence over the electricity market in the coming decades is already in almost every Americans’ pocket. Rechargeable energy storage (in the form of your cell phone’s Li-ion battery in your pocket) is changing a major fundamental aspect of the electric grid: That electricity is perishable and if you don’t use it (immediately), you lose it.

A major challenge of electricity generation and distribution is that the levels of electricity generation must match the level of demand in real-time, across the entire nation. And it’s no small feat predicting how much power every American will use each day and then delivering it to their doorstep. But large-scale energy storage can change how electricity will be both generated and consumed.

In part two, we explored how power generation has begun to shrink, moving back towards more local generation. Most of these smaller scale generator still feed their power into the major electric grid (examined in part one of this series). This is the case with most of the rooftop solar panels present in the St. Louis area. They generate power which is either used immediately by the homeowner, or fed back into the electric grid controlled by Ameren and when the sun goes down, the same house that sold power to Ameren during the day would have to buy power back at night, often at higher cost. If the homeowner could store their excess energy from the day, they could then use it during night and might avoid having to buy any electricity from their utility.

This possibility has led many people to begin designing and implementing infrastructure known as “Microgrids.” Microgrids are basically any collection of power generation, energy storage, and power loads (houses, office buildings, outdoor lighting, etc.) that are connected so that they can operate without the need for the large electric grid. A microgrid could be as small as an outdoor garden light with solar panels (and a tiny battery) or as large as an entire city (or college campus). The main point is that a microgrid would contain multiple types of distributed generation (solar, wind, gas turbine, etc.) and energy storage located throughout the grid. And the grid should be interconnected so that power can flow between any of the loads or generators and by including energy storage you can generate energy independent of demand. Energy can be generated today and not used until later this week, changing electricity from a perishable into a more permanent commodity. A microgrid could stock up on energy similar to how people will stock up on food before an incoming snowstorm. And because the microgrid is designed in a web-like manner, it would be more resilient against large-scale power outages that occur during storms, because a single generator going off-line would only represent a small percentage of the grid’s capacity.

In fact, safety and emergency back-up supply is one of the major reasons behind the push for the microgrid structure. After Hurricane Sandy caused widespread power outages on the East Coast, many leaders have called for more resilient microgrids that will provide emergency back-up power. Thanks in part to that push, New York State leads the country in microgrid installations, totaling over 200MW of capacity. Most of these microgrids operate in conjunction with the national grid. These are called grid-tied microgrids, as opposed to island microgrids which generally operate in areas where a grid in not accessible. This connection is important because it allows microgrids to share their generation and storage resources. Neighboring microgrids could operate together most of the time, but if one microgrid goes offline, the rest of the system can shut off their connection to the failing microgrid and maintain power everywhere else (avoiding widespread blackouts).

This type of electric grid system will require extensive monitoring and management, making sure that each individual generator or storage device is operating in unison. The management system would still need to monitor real-time demand (as does today’s national grid), but instead of needing to monitor demand and generation all over the country, it would only require knowledge of the locally produced electricity and building demand from nearby areas.

Locally producing and consuming electricity has other benefits, such as reducing the losses from sending electricity through miles of transmission and distribution wires. Losses from moving energy from power plants to consumers can rise above 10 percent. Reducing the distance that electricity needs to travel can cut these losses.

While the microgrid structure represents only a minuscule amount of the current U.S. grid, another advantage for microgrids is that they can be implemented piece-meal. A state won’t need to convert its entire grid to microgrids with a single project. Rather, as communities want to upgrade their local grid, a microgrid can be put in place with connection to the larger grid. Making a truly national network of microgrids would take many decades, but would be capable of meeting the U.S.’ power demand in a more resilient way than today’s current grid.