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Solar Shuts Down When Most Needed

Linda Hardesty

New YorkHurricane Sandy and its resulting economic losses have motivated a variety of stakeholders in New York City to come up with new ideas for back-up power during emergencies.

At the seventh annual NYC Solar Summit this week, power executives pointed out that solar installations in urban areas are generally grid-tied and designed to shut down when the grid fails so as not to feed power onto downed lines.

The inverters on solar systems are designed to shut down when there’s a problem with the grid because “you can’t have live power coming down a line that a lineman is working on,” explained Laurie Reilly, a spokeswoman with the City University of New York (CUNY).

A technical panel at the NYC Solar Summit yesterday presented on resiliency and the capability of solar to supply power in emergencies such as Sandy. The panel discussed new technologies that re-route the power captured on rooftops by solar and other distributed generation, allowing these resources to contribute during disasters.

One of the panelists, Tristan Kreager, manager of hybrid energy solutions with SMA America, said one of the company’s Sunny Boy residential inverters can provide a secure power supply of up to 1500 watts from the PV plant during grid failure. “There’s logic inside the inverter that registers when the utility is down and prevents any backflow of power onto the grid,” said Kreager. The inverter then isolates any power from the PV system to an accessory port, allowing for an AC circuit. The AC circuit only becomes alive during a grid outage and it needs to be manually switched on. The AC circuit can then be used to plug in household devices up to 12 amps such as appliances and cell phones, for example.

In January, CUNY formed the Smart Distributed Generation Hub with federal, state and city collaboration, working together to implement changes that can help utilize not only solar power, but other distributed generation solutions as resilient resources during emergencies.

Earlier this year, Green Power Resource Management (GPRM) announced production of its non-grid-tied solar powered air conditioner and virtual power plant in its new manufacturing facility in Escondido, Calif. “Typical solar installations are grid-tied and do not provide power when the grid goes down, said Ralph Ciarlanti, GPRM CFO. “Most customers do not know this.” Ciarlanti explained that the solar modules themselves are often powered by AC power coming in from the grid via a switching device at the master panel. It’s somewhat ironic that solar panels can generate electricity, but often need a little grid power to operate.



10 comments on “Solar Shuts Down When Most Needed

  1. In LA, the Department of Water and Power does not allow solar units to generate when the grid is down. It’s a serious mistake for earthquake country. Stand-alone capability should become a political goal of the solar movement. It might save lives.

  2. This headline doesn’t seem accurate (and seems a bit sensationalized). Also makes it confusing to read the article, which has a different message.

  3. Totally correct. This is 100% misleading. I’m now working on proposals by NY and NJ buildings to get solar BECAUSE of Hurricane Sandy and the message is. Solar works when the grid does not!

  4. I agree with the commenter above me — it appears to me that having solar system provide power, especailly during a massive disaster and city-wide grid outage, is a benefit even if the switches need to be manually switched on.

  5. If the solar system was wired into the grid the same way that a backup emergency generator is, the whole problem would be solved.
    The backup generator has an AUTOMATIC TRANSFER SWITCH that automatically transfers the home’s electric system from grid to generator by switching the main service wires OFF of grid and ONTO generator keeping generator power from reaching the grid.
    If the solar system had the same transfer switch, with a slight modification (to allow for net metering when the grid was up), it could power the house while the grid was down without endangering repair workers who were fixing supposedly dead circuits.

  6. From speaking with CUNY and the representative from SMA, the problem is: Solar COULD work when the grid is down, but in most cases it’s not set up that way, and the solar installations in NYC weren’t of much help after Sandy.

  7. Using solar for backup, as a substitute for a gen set for example, is not so simple, although I like the idea of a manual convenience outlet emerg supply.
    Consider this … when utility power is lost, it is usually during some sort of storm – dark clouds, late afternoon, etc – rarely mid day on a sunny summer day. Solar output is variable depending on strength of sun. To have an auto xfer switch to the house like with a gen set, when solar output is so variable on conditions, would probably result in just “browning out” everything and being not very useful. It is not simple. Keep up the good work CUNY & SMA.

  8. Maybe we should consider backup power in conjunction with solar power. Battery packs or Fuel cells. Perhaps a system with this capability can switch over to battery/ fuel cell at peak demand times as well to lessen load on the grid.

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