What is a microgrid, and when does it make sense?

What are the parts of a microgrid?

Every microgrid has the same building blocks, however large it is.

• Local generation. Solar panels, wind, small hydro, a natural gas or diesel generator, or a combination. These are sometimes called distributed energy resources.
• Storage. Batteries are most common. They smooth out supply and ride through short outages. See solar battery storage in Canada.
• Loads. The buildings and equipment being served, some of which can be marked as critical.
• A controller. Software and hardware that balance supply and demand every moment and decide when to connect to, or disconnect from, the main grid.
• A point of connection. A switch where the microgrid meets the utility's network, so it can separate safely.

How does a microgrid differ from rooftop solar?

A typical grid-tied rooftop system shuts down during an outage, to protect line workers, unless it is built to island. Adding a battery and the right equipment allows one house to keep running. That is a small backup system, covered in solar systems during power outages, and the inverter choices are explained in solar inverter types.

A microgrid goes further. Several sources and several customers are controlled together, so the system can decide which loads get power, charge storage when supply is high and keep critical buildings energized while others wait. The shared control is the main difference, and it is why a microgrid is usually owned by an operator such as a utility, a campus or a community group. A fully independent home system is a different case, discussed in grid-tied versus off-grid solar.

Where are microgrids used in Canada?

Remote communities not connected to the main grid have long run their own local systems, historically on diesel generators. Many of those communities are now looking at adding solar, wind or storage to cut fuel use, a story covered in off-grid solar in Canada. In connected areas, microgrids appear at hospitals, campuses, military bases and industrial sites that cannot afford long outages.

They also fit the idea of community-scale energy, described in community energy systems in Canada. A neighbourhood that owns its solar and storage can share the benefits and the risks. The rules for connecting such a system differ by province and utility.

What are the benefits and the costs?

The main benefits are reliability and resilience during outages, better use of local renewable power sources and, in some cases, lower energy costs from managing peaks. Microgrid systems that include energy storage can also keep critical services running while the electric grid is down. A microgrid can also defer upgrades to a stretched local network.

The costs are real, and design choices drive them. Controllers, protection equipment, storage and engineering add to the price of the generation itself, and operation takes skills most households and small businesses do not have. Prices depend on size, site and equipment and change from year to year, so obtain detailed quotes before comparing options. Another way for many small sources to work together is the virtual approach explained in virtual power plants, which links separate sites by software instead of by a shared local network.

What does this have to do with Drake Landing?

Drake Landing Solar Community in Okotoks, Alberta was a thermal system, not an electrical microgrid. Its 800 collectors, Energy Centre and buried loop shared heat among 52 homes rather than power. The planning ideas overlap, though: local generation, local storage and a controller that decides what to charge and what to deliver, as explained on the how it works page. The home electricity supply stayed on the normal grid.

Before spending money on a microgrid or a shared system, check the permitting and interconnection rules with your utility and the provincial energy ministry, and review current funding with the Government of Canada energy pages.

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