A microgrid is a smaller version of the larger interconnected power system that powers your home. A microgrid has its own mix of generation, control and load. A microgrid can either be connected to the larger electrical grid or completely islanded.
Islanded Communities and Diesel Displacement
With the advances in energy storage technologies, including lithium ion and flow batteries, adding local energy sources to a isolated community to serve as a major source of energy displacing the large amounts of diesel that are currently used.
Diesel is a very large cost for local communities, and relying on a single source of energy can cause energy insecurity for the community. There is a risk of a late shipment, spill, fire, etc causing an outage that will cause a risk of freezing in the cold north. By taking advantage of local energy resources such as mini hydro, tidal and wind, the diesel consumption can be replaced with local renewable energy reducing the reliance on diesel and the exposure of international diesel prices.
Above is a outline sketch of how the system may look. The energy sources will depend on the local resources available and could include those in the box and others not listed. These sources would feed into the microgrid optimization system (MGOS) which will make the decision to store or supply to the utility based on current energy needs of the community. The size of the storage system, and the technology used, will depend on the local load, energy sources and the existing diesel supply base.
How the Microgrid Optimization System will work
The MGOS will communicate closely with the local utility for existing load information and how much energy the community can accept in real time. The optimization algorithm will use the existing load, weather data, etc to determine the best use of the available energy and if there is an variance in supply and the load at the community.
The goal of the microgrid optimization system will be to ensure a 100% utilization of the local renewable energy displacing the maximum amount of diesel. The utility will typically own the diesel generation and based on their minimum power supply there will be times during low load situations the local energy will be stored and shifted to higher load times keeping the diesel to a minimum level load.
Without the addition of the storage system the hydro plant in this scenario must be limited during the low load times, and then the diesel system must take all the load when the sun comes up during the day. The average diesel used for 1 kWH of electrical energy is 3.3litres. In this case a total of 24,454 litres of diesel is used, over this two week period.
Implementing an energy storage system with a max storage of 2500kWH and 200kW of max charge/discharge rate only 19,072 litres will be needed, a savings of 5,382 litres.
The green line indicates the storage capacity at reach hour over the two week period. When the light blue is above the black load line that indicates when the storage system is charging, and when under it indicates when the system is charging. By eye only you can see how much less light orange is used, this indicates a savings of 5,382 litres of diesel. Assuming a delivered cost of $0.9/litre to a remote community this indicates a savings of $4,800 over a two week period.