In my blog 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 (photovoltaic) 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 fifty 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 — an approach referred to as cogeneration or combined heat and power (CHP).
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 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 a critical loads in 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 Philadelphia, 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 20-foot container, which the company (confusingly) trademarked as PowerFactor (at least it’s confusing to those of us who have been trying for years to fully understand what power factor means).
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. This PowerFactor250 system includes a 250-kW inverter and has 125 kWh of battery storage. 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 PowerFactor500 system manages power from a 402-kW solar array that is integrated with parking lot canopies, and it includes 300 kWh of battery storage (though 250 kWh would be more typical with the 500 kW inverter). It includes critical loads power that can provide 50 kW of electricity for just over four hours — or more when the sun is shining and generating power.
Innovation is 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. “Adding storage to solar projects makes them even more valuable to customers and also provides new benefits to the grid — and all ratepayers,” Solar Grid Storage CEO Tom Leyden told me. “We are proud to be part of what we believe will help usher in the grid of the future.”
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 is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.