In my column last week, I reported on The Navy Yard in Philadelphia, a remarkable 1,200-acre business campus with 300 companies employing 10,000 people -- with as many as 35,000 employees projected eventually. What had attracted me to the facility while I was in town for a conference, was an innovative demonstration that’s been launched showing how solar-electric systems with battery back-up and smart controls can help to create a more resilient power grid.

This week, I’ll dig a little more deeply into this system, which has been developed by the company Solar Grid Storage, LLC.

The emergence of microgrids

With more intense storms, wildfires, terrorist actions, and other events causing widespread power outages -- and likely to cause increasingly common outages in the future, according to many experts -- there is growing demand for creating islandable "microgrids."

Microgrids are small- to moderate-size power grids, often serving university or medical campuses, that have the capability to be isolated from the regional power grid in the event of a widespread outage. Such systems must have their own generation capacity along with sophisticated electricity management systems.

More than 50 military bases have created, or are in the process of creating, microgrids. Military facilities have to maintain operability, even if widespread outages occur, so they are a natural for microgrids. Some universities and hospital complexes have also created microgrids, and the State of Connecticut, heavily hit by Superstorm Sandy, Tropical Storm Irene, and a freak October snowstorm in 2011, has passed legislation to create demonstration microgrids in eight cities.

Another advantage of microgrids is that the small-scale power generation needed for such systems takes place close to where the power is being used, so if there is waste heat created in the generation process (as occurs with generators that use steam turbines or fuel cells), that heat can be captured and productively used -- referred to as cogeneration or combined heat and power.

How a small amount of
electricity storage can boost
grid resilience

Our electricity grid is a complex and hard-to-manage system. The amount of power (electricity) being generated has to be closely balanced with the amount of power being consumed (demand). Fluctuations in demand occur all the time. In the morning hours between 6 and 8 a.m., for example, a lot of people get up, turn on lights, shower, operate their coffee makers, and turn up the heat (or air conditioning); electricity demand rises significantly.

One of the big challenges in managing this fluctuating demand is that most generators can’t be turned on and off quickly. You can’t just throw a switch and expect a several-hundred-megawatt generator to start cranking out electricity.

With renewable energy power-generation systems -- particularly wind and solar -- fluctuations in output provide another complication. When the wind stops blowing the output from a wind farm ceases, and when clouds obscure the sun the output of PV systems drops dramatically.

Battery storage in a power grid allows electricity to be stored when more is being generated than consumed, and it allows electricity to be pulled out of storage when demand exceeds supply. The same battery bank can allow critical loads in a microgrid to remain powered when the regional grid goes down. This role of batteries in managing the output from wind and solar systems is important and will grow in significance as the percentage of our electricity supplied by renewables grows.

Solar Grid Storage

Based in Silver Spring, Maryland, with a few other offices spread around the Northeast, Solar Grid Storage offers a modular system for managing the output of PV arrays and storing power to better balance the output and power availability from large, grid-connected PV systems.

Advanced, lithium-ion batteries are used in this system. This technology avoids the use of heavy metals like lead and cadmium that are used in other batteries. The technology also allows deep discharge without wearing out the batteries and very rapid recharging -- though cost is an issue.

The business model for Solar Grid Storage is that the owner of a large PV array would own just the actual array, and Solar Grid Storage would own the inverter, battery system, and other equipment needed to manage the system. These components come packaged in a 30-foot container, which the company confusingly refers to as PowerFactor.

The battery bank and controls allow the system to take over instantaneously in the event of a regional power outage.

One of the first four of these systems has been installed at The Navy Yard, and my colleagues and I got a chance to tour this facility. Being modular, it is shipped directly to the site and can be hooked up quickly.

Another, larger PowerFactor system was installed in October, 2013 in Laurel, Maryland for the real estate developer Konterra. That system manages power from a 402 kW solar array that is integrated with parking lot canopies. It includes critical loads power that can provide 50 kW of electricity for just over four hours.

Innovation just beginning

The Solar Grid Storage installations are cutting-edge examples of what we can expect in the years ahead as efforts to effectively integrate renewable energy into the utility grid move forward. I believe that such innovations will demonstrate very effective synergies between solar energy (and other renewables), the goals of resilience, and the efficient operation of the power grid. It should be fun to watch!

Alex Wilson is the founder of BuildingGreen, Inc. and the Resilient Design Institute (, both based in Brattleboro. Send comments or suggestions for future columns to