The Sandia-developed Energy Surety MicrogridTM (ESM) methodology presents a new paradigm in the production of our nation’s power – embracing the concept of “think globally, act locally,” but utilizing an innovative and practical approach.
ESM methodology directly links energy surety (safety, security, reliability, sustainability, and cost effectiveness) with critical power needs. It does this by integrating distributed energy resources (DERs), including backup generators, local PV systems, small wind turbines, electrical energy storage, etc., into a local electrical distribution service area (microgrid). This decentralized approach allows the DERS to be managed intelligently, efficiently, and reliably.
Sandia’s methodology offers three main advantages over a typical microgrid design:
- ESM microgrid design allows the microgrid to be grid-tied (operated in conjunction with, and even augmenting, the main grid with microgrid-generated power); or to be islanded (operated completely independent of the main power grid).
- Computer modeling that utilizes extensive analysis capabilities to determine the most efficient, most cost-effective, most secure and safest combination of distributed energy resources (DERs) within the microgrid.
- A risk assessment approach that identifies the critical needs within a microgrid. When the main grid goes down, in an ESM-designed microgrid, the methodology has already prioritized those missions that pose the most critical risk to security and safety, and apportions the power accordingly.
The energy surety microgrid is a smaller version of the larger electric grid. It can generate and control electrical power output in a self contained, localized area; thus ensuring that installations within the microgrid have the necessary power to maintain critical missions, even when the main grid goes down.
In addition, localizing electrical power generation and control sets the stage for future grid modernization. Because the ESM framework utilizes the integration of DERs into a microgrid, it lessens the need for the construction of large, distantly located electrical power plants, which can include large PV and wind farms.
Local control of microgrid resources enables smart grid functionality, including:
- Demand response (shutting down high energy use appliances such as air conditioners for brief periods during times when the demand for electricity is high);
- The intelligent interconnection and integration of small DERs including generators, PV panels, and small wind turbines
- Net metering – the ability for the microgrid to sell back to the utility any excess power generated within its borders.
Currently, when the main grid loses power, many end-users rely on backup generators, usually diesel-powered, for their emergency power source. In most cases, single backup generators are dedicated to single buildings. In an ESM design, when the grid goes down, the microgrid is physically disconnected (islanded) from the main grid, and begins to produce the power needed to operate the critical missions within the microgrid.
One key method for producing the required power in the most efficient, reliable, and cost effective way possible is to interconnect backup diesel generators within the microgrid. If a single generator fails, interconnected generators can meet the demand; and because interconnected generators serve more than one building, they can be scheduled to run at full power, which is the most efficient operating mode for a diesel generator.
In non-ESM microgrid designs, when the grid goes down, renewable resources such as solar and wind systems must be disconnected, because the power they produce continues to feed into the grid, thus creating safety hazards for those working to repair the grid. Because the ESM methodology ensures that the microgrid physically disconnects from the main grid, the renewable generation sources within the microgrid are not required to be disconnected; they can continue to produce power without creating a safety hazard.
The ESM methodology also has advantages when the main grid is up and running. In grid-tied mode, DERs, such as solar or wind power located within the microgrid, can minimize dependency on utility-generated power. This results in decreased costs. And, because microgrid customers can sell the green energy they produce back to the utility, the utility’s dependency on fossil fuel is minimized.
Recently, grid security has become a pertinent issue, due to the threat of cyber attack. Given that an ESMTM requires significant levels of software, control, and networking, cyber security becomes a salient ingredient of the ESM microgrid design process. The ESM methodology allows for the incorporation of cyber security standards such as encryption, firewalls, strong password requirements, and other measures that enable command and control of the microgrid.
Risk Assessment Approach
When the main grid goes down, critical missions must still continue operations. In the event that a power outage lasts longer than a few hours, Sandia’s risk-based approach ensures that critical missions are allocated available power on a priority basis. The Sandia methodology prioritizes these critical missions based on the risk that is posed if they do not receive power. I.e., it is better to provide extended power to critical missions, like command centers or hospitals, than to provide limited duration power to non-critical missions.