At approximately 8 p.m. on October 29, Hurricane Sandy slammed directly into the New Jersey coastline near Atlantic City. Sandy’s 90-mile-per-hour winds also coincided with a full moon and high tides. Over 2.7 million, or 68 percent, of New Jersey electric utility customers were without power at the peak of this storm. As a result of Sandy, there were approximately 9,000 downed utility poles and 116,000 fallen trees. Thousands of homes and businesses were destroyed, refineries were shut down and 70 percent of gas stations were offline. As a state, we mourn these losses and have come together to rebuild.
Sandy also impacted the operations of solar and highlighted the fact that solar, as currently designed, does not operate if grid power is down.
In 2001, there were only six solar projects for a total of 9 kilowatts in New Jersey. These six facilities produced approximately 10,800 kilowatt-hours of electricity per year. At the end of 2012, there were almost 19,000 solar installations across New Jersey for almost 1 gigawat of solar capacity, which generated over 1 percent of the electricity used in the state. Today, there are almost 5,000 projects in various stages of installation for almost 740,000 additional kilowatts of solar capacity in the pipeline.
After Hurricane Irene there were no reports of any significant solar panel damage. Likewise after Sandy, while there was damage to some projects, there were no reports of massive panel damage. Even some panels that were on buildings that were destroyed by the storm survived intact. The 1 gigawatt of installed solar did not assist in the aftermath of the storm, but a change in design could address this issue.
When grid power to a home is down, the solar inverter senses the loss and shuts down the system. This happens by design and is required by code. Most solar systems are not designed to operate independently of grid power. The distribution grid under net metering acts as the storage component for the system. When the solar generator does not use the solar electricity, it is virtually stored on the distribution grid to be used later. When the sun goes down, the solar generator gets back the solar electricity that was stored on the distribution grid. The solar generator’s electricity is not really stored on the grid, but under net metering the grid functions like storage for the generator. This standard design works well, except when a majority of the grid power is out from a storm. The solar generator loses the ability to store solar electricity.
Solar can be designed to operate as a part of a storm emergency response solution with two system changes. One is through use of an inverter that senses the grid power is offline and switches the solar to isolate the photovoltaic system. This isolation needs to include a transfer of critical loads within the building. The switching, which is what happens when an emergency diesel generator comes online, is a little more difficult with solar because of the variability of the solar generation. This transfer has to be able to match critical loads to account for the variable generation of solar.
The other way solar can operate following a storm is through an onsite storage system, since the grid is no longer the storage system. Currently, this storage is in batteries onsite, but the onsite batteries only have to support the critical loads and not the full building load. In the future, within a smarter grid, this may be improved through community storage or distributive storage.
There continue to be advances in the area of off-grid solar. New Jersey has invested in companies that design and build these types of systems. One is Princeton Power Systems in Lawrenceville, N.J. The Board of Public Utilities and our Economic Development Authority have funded the growth of this clean-energy company since 2005. Princeton Power designs and builds inverters that can operate as grid tie systems, but more importantly as off-grid systems. They have designed and operated several solar systems that can be isolated from the grid to operate when the grid is down.
New Jersey is currently evaluating other systems that can operate in a storm-response mode when the grid is down. Solar with storage could be included in that mix. Designing solar for off-grid with storage is currently more expensive than the standard design. When viewed in retrospect after a hurricane, however, this redesign could add significant value.
One of the keys to advancing off-grid solar in a storm response mode is smart grid. Smart grid is more than just installing advanced meters at homes or businesses. Smart grid is enhancing the intelligence of the distribution grid to be able to improve its ability to add innovative technologies such as storm-responsive distributive generation. A smarter grid can make storm-responsive photovoltaics possible and improve the grid’s reliability during an emergency.