Understanding Microgrids
The jury is out on the definition of a microgrid
The definition of a microgrid changes depending on the project constraints in which it is used. The term gets thrown around with different context and a new definition almost every time I hear it. I’ve seen the differing points of view and it is about time for a consensus. We all need to be on the same page using the same terminology.
After Hurricane Sandy, we might be discussing a grid-tied system with large battery storage and smart electronics that can provide power during service outages. In developing countries, we might be discussing an off grid system with pay-as-you-go meters and less than 100 kilowatts of solar PV. On a university campus, we might be discussing combined heat and power for a group of buildings.
Technically these are all microgrids, but microgrids of different types. The best but most broad definition I have seen is from the Microgrid Institute:
A microgrid is a small energy system capable of balancing captive supply and demand resources to maintain stable service within a defined boundary.
Key Characteristics of a Microgrid:
- Connecting to the traditional grid is optional.
- Resiliency, reliability, and sustainability are the core responsibilities.
- Backup for all system loads, not just the critical loads.
- Modern technology is needed to optimize energy production and usage.
Other Definitions
Smart Grid Interoperability Panel (SGIP) has a white paper further describing Local Grid Definitions, a clarification on #microgrid #picogrid & #nanograd.
According to the US Department of Energy:
A microgrid is a local energy grid with control capability, which means it can disconnect from the traditional grid and operate autonomously.
According to the Rocky Mountain Institute:
Microgrids are subsets of the greater grid and usually include their own generation (such as photovoltaics, wind turbines, and fuel cells), their own demand (lights, fans, televisions, computers, etc.) and often the ability to modulate it to match price and priority, and perhaps even storage capability (such as batteries or the distributed storage in electrified vehicles). What makes the microgrid unique is that it intelligently coordinates and balances all these technologies.
According to the Microgrid Institute:
A microgrid is a small energy system capable of balancing captive supply and demand resources to maintain stable service within a defined boundary. Microgrids are defined by their function, not their size. Microgrids combine various distributed energy resources (DER) to form a whole system that’s greater than its parts.
Most microgrids can be further described by one of five categories (as defined by Microgrid Institute):
- Off-grid microgrids including islands, remote sites, and other microgrid systems not connected to a local utility network.
- Campus microgrids that are fully interconnected with a local utility grid, but can also maintain some level of service in isolation from the grid, such as during a utility outage. Typical examples serve university and corporate campuses, prisons, and military bases.
- Community microgrids that are integrated into utility networks. Such microgrids serve multiple customers or services within a community, generally to provide resilient power for vital community assets.
- District Energy microgrids that provide electricity as well as thermal energy for heating (and cooling) of multiple facilities.
- Nanogrids comprised of the smallest discrete network units with the capability to operate independently. A nanogrid can be defined as a single building or a single energy domain.
The most challenging part of our microgrid future is that it must be cheaper than the status quo.
There are some situations that microgrids will be implemented in an area for the first time, such as in developing countries; and other times, it will be introduced to replace the aging infrastructure and outdated equipment. The old generation will be butting heads with the new generation. SolarCity is proactively warning and preparing the utilities of the world with their Grid Engineering Solutions.
