Microgrids Explained: How They Work and When to Use Them
A microgrid is a localized energy system capable of operating connected to the main grid or independently. This guide explains how microgrids work, their components, and applications.
What Is a Microgrid?
A microgrid is a self-contained electrical network — comprising generation, storage, loads, and control systems — that can operate either connected to the main utility grid or independently (in 'island mode'). The defining characteristic of a microgrid is its ability to disconnect from the larger grid and continue operating autonomously, maintaining power supply to its local loads regardless of conditions on the main grid.
The concept of the microgrid is not new — remote military installations, industrial campuses, and island communities have operated self-sufficient power systems for decades. What is new is the sophistication of the control systems, the diversity of generation and storage technologies available, and the economic case for microgrid deployment at commercial and industrial scale driven by increasing grid reliability concerns and falling distributed generation costs.
Core Components of a Microgrid
Generation Assets
A microgrid typically includes one or more generation sources. In industrial and commercial applications, natural gas generators (fueled by pipeline gas or LNG) are the most common generation technology due to their reliability, dispatchability, and energy density. Solar PV, fuel cells, and microturbines are also used, often in combination with gas generation.
Energy Storage
Battery energy storage systems (BESS) serve several functions in microgrids: bridging power during generation transitions, providing fast-response frequency regulation, enabling energy time-shifting, and providing initial power during island mode startup before generators reach full load.
Load Management Systems
Advanced microgrids include load control systems capable of shedding non-critical loads during supply constraints, prioritizing critical processes, and managing load balance across generation sources.
Microgrid Controller
The microgrid controller is the intelligence layer that coordinates all components — dispatching generation, managing storage, controlling load, monitoring grid conditions, and managing the transition between grid-connected and island mode operation. The controller must be able to detect grid disturbances and initiate islanding transition within milliseconds to prevent load disruption.
Interconnection Equipment
Static transfer switches (STS) and automatic transfer switches (ATS) manage the electrical connection between the microgrid and the main grid, enabling seamless transitions between modes.
How Microgrids Achieve Island Mode Operation
When the microgrid controller detects a qualifying grid disturbance — voltage sag, frequency deviation, or complete outage — it initiates island mode transition. The static transfer switch disconnects the microgrid from the main grid within milliseconds. Within the island, generation assets are dispatched to balance supply and demand without support from the main grid. Battery storage provides bridge power and frequency/voltage support during the transition period. Load management sheds non-critical loads if required to maintain balance within the island's generation capacity.
Fuel Supply in LNG-Fueled Microgrids
For microgrids using natural gas generation, fuel supply reliability is as important as generation equipment reliability. Integrated LNG supply chains that provide on-site cryogenic storage and continuous truck delivery enable microgrid operation fully independent of both the utility grid and the pipeline network — the highest level of energy independence available to commercial and industrial operators.
Microgrid Applications
Industrial Campuses
Large industrial facilities — refineries, chemical plants, steel mills, data center campuses — are prime microgrid candidates. Their high, concentrated power loads and high sensitivity to power quality and continuity justify microgrid infrastructure investment. Industrial energy solutions from United Energy support microgrid fuel supply for these applications.
Remote Operations
Remote industrial sites without grid access are effectively forced microgrids — completely self-sufficient energy systems by necessity rather than choice. Remote site power systems apply microgrid principles to the most demanding operational environments.
Critical Infrastructure
Hospitals, emergency services, water treatment facilities, and other critical infrastructure are investing in microgrid capability to ensure continued operation during grid emergencies — particularly in regions subject to extreme weather events or other grid reliability concerns.
Key Takeaways
- A microgrid is a self-contained energy system capable of operating connected to or independent of the main grid
- Core components include generation, storage, load management, control systems, and interconnection equipment
- Island mode operation requires millisecond-response control systems to prevent load disruption during grid separation
- LNG-fueled microgrids provide energy independence from both the utility grid and the pipeline network
- Industrial campuses, remote operations, and critical infrastructure are the primary microgrid applications
How does a microgrid differ from a backup generator?
A backup generator provides power when the grid fails but typically takes 10–30 seconds to start and cannot operate continuously as a primary power source. A microgrid is a complete, continuously operational energy system designed to serve as either a supplement or replacement for grid power, with smooth transitions between grid-connected and island modes and the capability to operate indefinitely in island mode.
How much does a microgrid cost?
Microgrid costs vary enormously based on generation capacity, fuel type, storage, and control system sophistication. Industrial microgrids in the 1–10 MW range typically cost $1–5 million per MW installed. Larger systems may benefit from economies of scale. Power-purchase agreement (PPA) and energy-as-a-service models can reduce upfront capital requirements.
Can a microgrid sell power back to the utility grid?
Yes. Grid-connected microgrids can participate in electricity markets, selling excess generation to the grid or providing ancillary services like frequency regulation. This additional revenue stream can improve microgrid project economics. Regulatory requirements for grid-connected generation participation vary by jurisdiction.
What is the role of natural gas in microgrids?
Natural gas, fueled by pipeline or LNG, is the most common dispatchable generation technology in industrial microgrids. Gas generators provide reliable, controllable power that can ramp up and down quickly to match load changes. In island mode, dispatchable gas generation provides the frequency and voltage stability that microgrid loads require.
How long can a microgrid operate in island mode?
A properly fueled microgrid can operate in island mode indefinitely. The practical limit is fuel supply — on-site fuel storage provides a defined reserve, and continuous delivery (for LNG) extends runtime without limit. Remote microgrids with well-managed LNG supply chains can operate autonomously for months without grid support.
LNG Fuel Supply for Industrial Microgrids
United Energy provides integrated LNG supply chains for industrial microgrids requiring reliable fuel independent of pipeline and grid infrastructure.