Why Residential Solar Can’t Keep The Lights On (Yet)

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Dan Boyce/Inside Energy

Solar Panels for municipal energy production in Del Norte, Colorado

Rooftop solar panels are increasingly popular and affordable, but unless you pay for costly battery backup, they won't power your home during a blackout.

MJ Monty, via Flickr (creative commons)

Rooftop solar panels are increasingly popular and affordable, but unless you pay for costly battery backup, they won\’t power your home during a blackout.

Last week, in Part 1 of our Solar Challenge series,  Inside Energy reporter Dan Boyce explained why the water treatment plant in Del Norte, Colorado, can’t rely on electricity generated by its solar panels during a power outage. Keeping solar power running is dangerous for utility staff working to restore grid power and reconnect solar-powered facilities to the grid after an outage.

This issue doesn’t only affect relatively larger commercial and municipal solar installations. If your home has photovoltaic panels, it most likely affects you, too.

The vast majority of all solar systems, regardless of size, are designed to shut down during a utility power outage. Backup batteries or generators help solar-powered homes keep the lights on when grid power goes down. However, these reliability enhancements are beyond the financial reach of most homeowners. (Even though the cost of rooftop solar has been dropping steadily, that’s for typical residential installations which do not include battery or generator backup.)

Boyce noted that microgrids might be one way to allow solar panels to keep generating power during a blackout. A microgrid is a localized power grid that can be operated independently of the utility grid. This is an option where ample local power generation resources exist, and where smart inverter devices support switching between locally generated power and the grid.

The catch is that most neighborhoods don’t have enough solar panels or other sources of non-grid electricity to meet basic needs, and thus can’t support a microgrid. However, the fast-rising rate of utility power grid disruptions (as documented by Inside Energy Data Journalist Jordan Wirfs-Brock, in our series) may motivate more communities to install more local generation capacity. Eventually, this might be enough to harness into local microgrids that could keep the lights on when severe weather, wildfires, or other calamities temporarily knock the grid offline.

Realistically, community microgrids probably would combine several power sources in addition to solar photovoltaics with battery backup — especially fuel cells, wind turbines, or conventional generators fueled by natural gas or propane.

Community crowdfunding might substantially expand residential solar into rental and low-income housing.

When more solar or other power sources exist right in your neighborhood, you and your neighbors have more options — not simply to cut your utility bills and greenhouse gas emissions, but to keep your lights on at all.

How much power disruption are you willing to tolerate? How many outages, or how long would they have to last, would it take for you to want to take action or spend money to ensure always-on power at your home? Please comment below with your thoughts.

  • Paul D. North Jr.

    My comment on the NPR version of this report on Sept. 17th ( http://www.npr.org/2014/09/17/348987688/when-the-powers-out-solar-panels-may-not-keep-the-lights-on ) is pasted below:

    “Because of frequent power outages, and for many of the reason cited in this report – even though we’re in a suburban-rural area only 5 miles from Allentown, Penn. – this past spring we installed a 4.2 KW solar panel array on our roof ($14,000), plus 8 ea. 12 volt 250 amp-hour batteries as a back-up ($8,000), with all the necessary inverters, controllers, etc., all available “off-the-shelf” and easily permitted by our local building code department. It worked seamlessly a few weeks later when a stupid driver broke a utility pole at 10 PM and the power was out for 3 hours. In the meantime, the solar panels have also reduced our power bill by about half, producing from 10 to 24 KWHr of power each day (depends on the weather and sun angle, course). We’re extremely satisfied with it all, and think more widespread implementation of similar systems would be a good thing for the grid and community reliability and disaster preparedness.”

    Comments there are closed now, but I’d like – and need – to add more a little more here, because (good grief !) there seems to be a lot of ignorance and misinformation about this out there:

    See the video “SAVING SUNSHINE – Keeping the Lights On with Batteries and Solar Power” (presently available as a DVD only, for $20, free shipping) from the Mid-Atlantic Renewable Energy Association (MAREA) at: http://www.themarea.org/saving-sunshine.shtml

    The ‘star’ of that video, Bruce Hankin, was one of the installers of our system; the other – and the actual contractor – was Bill Hennessy, of Berks Solar: http://www.berkssolar.com/

    The “state-of-the-art” ‘guts’ of our battery back-up system is the Magnum Energy MagnaSine Model No. MS-4448-PAE Inverter/ Charger (see: http://magnumenergy.com/ms-pae-series-invertercharger/ ) mounted on a MPSL 175-30D Panel ( http://magnumenergy.com/mp-series-magnum-panel/ ). The basic inverter is a Solar Edge Model SE 3800A-US “Utility Interactive Non-Isolated Photovoltaic Inverter” (see: http://www.solaredge.com/wp-content/uploads/pdfs/products/inverters/se-single-phase-us-inverter-datasheet.pdf – I don’t know why it’s labeled “Non-Isolated”, though). Anyone who wants to know more about the technical aspects should contact Bill, not me.
    I see this website apparently allows images (photos0 to be posted as well. I might try to do that later today/ tonight (time permitting).

    • bill lopez

      I have a 5.6kW grid tied system. One of the first tests I tried was seeing the outcome of running my generator and testing the response from the inverter. Inverter shut down, error message: AC Freq Too High / Low.

      Buried in the instruction manual I found this little tid bit: “Use the Wakeup menu to set the minimum and maximum grid frequencies and grid voltages between which the inverter
      can begin power production.”

      So – it would seem that my “grid tie” inverter IS capable of running with frequency and voltage ranges OUTSIDE of the “normal” grid provided specs.

      Next up for me is to test what the girds frequency is and then check what my generator outputs – my plan would then be to either re-program the inverter to operate within a wider range, or just wait until my power was out, and then go re-program the inverter.

      I also want to check if I can set it to zero, and see if it will operate without any grid ac voltage.

      From the Inverter’s config menu:

      The ranges for Wakeup parameters are:

      Frequency: 0 to 100 [Hz]

      Voltage 0 to 500[V]

  • Guest

    See attached photos.

  • Paul D. North Jr.

    Trying to upload images . . .

  • Don Duncan

    Paul: You say you cut your power bill by half. That is useless info. What is the payback time? How long will it take to recoup your expense?

    It is my understanding that solar is not cost effective yet. Am I wrong?

    • A statement like “solar is not cost effective yet” is an over simplified. The cost benefits of solar MUST be determined on a case by case basis (or at least on a regional basis). Just as everyone pays different utility rates, so the time it takes to offset the cost is different—everywhere. The cost is also complicated by multiple factors such as tariffs, rebates and incentives. Most of these (except the on granddaddy of them all, the Renewable Energy Tax Credit) are regionally based issues as well.

      There are many places in the U.S. where solar can save consumers a bundle, other places, not so much. The number of places where it really pays off are increasing at a very impressive rate (many have said that it’s a better investment than the stock market).

      The is only one reasonable answer to the question of the current viability of residential solar. That is: It depends on where you live.

  • Don Duncan

    “Realistically, community microgrids probably would combine…”? Not at all. Hooking up a hodge-podge of systems opens up a complex problem of how to fairly distribute the cost. With each system being different, in cost, in generation, in storage, the decentralization poses challenges not addressed anywhere.
    “How much power disruption are you willing to tolerate?” That would depend on the cost of avoidance. And that would depend on each house, and the importance of continuous service. So the answer is different for each household. Presently, no one is saying it is financially viable, or even close.

  • john

    I note in the article some mention of Islanding.
    As I understand it every inverter is set to shut down in nono-seconds when the grid is disrupted I find it extremely hard to see the problem.
    Unless some issue has not been addressed I can not believe there is any problem end of story if there is why on earth was the inverter manufacturer been allowed to sell it?
    If any inverter is allowed to be sold in a state of possible danger it is the fault of the regulatory system.
    If a system is so poor god help you because nothing sold is safe frankly.
    I find it very hard to believe this.

  • I’m fortunate to live in a new development, with underground power lines. We don’t have forest-fulls of tall trees like many in the East and Southeast, either.

    Historically, we loose power for only about 45 min. at a time and that happens only about once every two years. Not something to worry about, with or without solar.

    The only problem we’ve had with solar was with the local pigeon population. They don’t cause any loss of power, but they can do roof damage and make a lot of mess and noise. Nesting and gnawing squirrels, on the other hand, can certainly cause a power outage. And the solution certainly won’t be as easy or quick as getting power back from the utility.

    Solving that problem led me to create a solution, which is now my business—supplying installers with the equipment and know-how to keep varmints out from under residential solar installations.

  • Amber Rivera

    Hi everyone – I’m Inside Energy’s Engagement Editor. Thank you all for reading and for your participation in the discussion. If you’d like to be more connected to the work that we do, sign up to be a part of our Insider Network, at this link: http://insideenergy.org/Insiders