Designing Resilience Into The Grid

The technology involved in a microgrid, includes the analysis, methods, and requirements of the grid, in addition to the physical off-the-shelf components.

Last year, the Department of Energy (DOE) announced more than $8 million for microgrid projects across the United States. With goals of reducing emissions by more than 20% and improving system energy efficiencies by more than 20% by 2020, microgrids will be part of the solution as they help increase the amount of renewable energy that can be integrated into the grid.

Sandia National Laboratories is one of the groups involved in the projects, with more than a decade of microgrid technology experience. Traditionally motivated by critical uses of electricity by the military, Sandia is now working to retool the technology for use in the civilian sector.

“The interest has always been there,” explains Dr. Abraham Ellis, Technical Staff, Sandia National Laboratories, speaking of civilian adoption; but a recent push to action has followed the destruction caused by Hurricane Sandy in 2012. “So much of the critical infrastructure just failed, and energy was a big part of it,” adds Ellis. “There is always motivation when something bad happens.”

The difficulty of designing a large system immune to large scale disaster, as well as the associated cost, have trumped motivation in the past. According to Ellis, it has been outside the realm of the normal planning process; however, the design can now be secured more easily on a local level through the use of microgrids.

Per his own definition, Ellis describes a microgrid as “part of the grid that has in it defined loads … it also has local generation resources, and other types of controllable assets, like energy storage,” explains Ellis. “The microgrid has the ability to work in parallel with the grid when the grid is operating normally.”

By that definition, microgrids are fairly common, such as emergency generators in hospitals or airports. “When the grid goes down those generators provide power to a defined part of the load.” However, these examples are not of very high performing microgrids, with limitations to the amount of fuel on site, and the inability to operate in parallel with the grid, because of their high emissions.

An Energy Savings Account

Having energy under local control in a microgrid is “like having a savings account,” says Ellis. “You have another option if part of the grid is taken out.” With this degree of resilience, the effects of large scale disasters can be mitigated.

This control also gives grid designers the option to make components more or less robust to specific threats, such as harsh environments, or malicious attacks from terrorists.

The technology involved in a microgrid, includes the analysis, methods, and requirements of the grid, in addition to the physical off-the-shelf components. “We're not talking about a new type of hardware technology,” explains Ellis. “What we're talking about a new approach to be able to design a network in an optimal way.”

This new approach includes quantifying the resilience of the grid, which is not an easy thing to do. “The first thing you have to decide is whether one approach is more or less resilient than another, and by how much … In addition, you have to know the cost differential and the risks,” explains Ellis.

While Ellis doesn't believe in a particularly insurmountable challenge to implementing microgrids, balancing costs and benefits remains difficult. “I don't think technology is the showstopper,” he adds.

A primary challenge is when the microgrid does not work in parallel with the grid. “You have to be more careful than usual about the way the controls internal to the microgrid are designed … because a microgrid tends to have less flexibility to manage voltage and frequency within the microgrid,” explains Ellis.

In other words, “you cannot count on the grid to do everything. The microgrid has to maintain control of the quality of the electricity using its own resources. While they are smaller, you have to be more conscious about it.”

Weighing the Benefits

Power storage has long been the thorn in the side of product development. While some advances have been made, price still remains an issue, and for microgrids, it has to be balanced with the benefits.

“If you have an energy storage system, you can use it to charge or discharge as you need to make sure you don’t over-tax the generation resources in the microgrid,” explains Ellis.

Typically, a microgrid designer will try to deploy an energy storage system that is as small as possible as the larger systems quickly become cost prohibitive. “This is a positive trend,” says Ellis. “Several years into the future energy storage is going to become more cost effective and we will see more on the grid.”

Managing the Future

To the casual observer, a microgrid isn’t particularly visible. The big changes will come for the utilities managers, to whom the microgrid will be quite conspicuous. “[Microgirds] change the way you mange your own energy use,” explains Ellis, adding that the new technology may require energy managers to become savvier. “It is a new type of system you need to get used to,” he adds. “It’s a lot of fun actually. But it can become somewhat complicated.”

With any new implementation, examples are always helpful. Right now, many entities could consider microgrids to address resilience and emissions concerns, but people are lacking education. “It is always useful to have examples of successful microgrid deployments,” adds Ellis. “It makes it easier for other people to make a more informed decision.”

Other notables besides Sandia working on microgrid projects, include the Electric Power Research Institute (EPRI) and General Electric Company (GE), both supported by the Energy Department’s National Renewable Energy Laboratory (NREL).

“Microgrids support a flexible and efficient electric grid, enabling the integration of renewable and distributed energy resources such as wind and solar energy, combined heat and power, energy storage, and demand response," says NREL's Energy Systems Integration associate director, Bryan Hannegan. "NREL is excited to be working with EPRI and with GE to accelerate the development of microgrids that can provide a reliable, affordable, and sustainable electricity supply."

Whether or not the U.S. will meet its goals by 2020, microgrids are “a step in the right direction.”

This article originally appeared in the March 2015 print edition of PD&D.