Last week we reported on Silver Spring Networks’ Maui smart grid project, including its plans to addsolarpower to its list of smart grid link-ups. Looks like those plans are coming true -- and you can add Oklahoma to the list.
Utilities in both states are asking Silver Spring, inverter maker Fronius and solar installer SolarCity to network smart inverters that connect rooftop solar systems to the grid. Both projects are funded by the Department of Energy’s SunShot program, which represents Energy Secretary Steven Chu’s vow to reduce the overall cost of rooftop solar to $1 a watt -- not per panel, but for the entire installation: parts, labor, permitting and all.
SunShot gave out $145 million in grants earlier this year, of which $25.9 million was set aside for eight solar-grid integration projects. Looks like the new Hawaii-Oklahoma partnership is one of them. In Maui, the companies will retrofit old inverters and install new ones to balance the grid, both against the fluctuating power from the PV itself and against the dips and spikes caused by wind farms and the diesel-fired turbines that provide most of its (very expensive) power.
The Oklahoma project will be a little different, in that Oklahoma Gas & Electric will actually own the inverters that connect to customer-owned solar and will be trying out a technique called conservation voltage reduction (CVR), which saves power by reducing grid voltages to bare minimums.
Silver Spring already works with OG&E on smart meters and home area networks, and is supporting its commercial-scale rollout of a fully smart-meter-enabled, home-thermostat-connected variable pricing program meant to shave peak loads and avoid building new power plants -- and smart inverters could really help with that goal.
Inverters only make up about 10 percent to 15 percent of total PV installation costs. But they could offer all kinds of cost-reducing, grid-balancing functions that actually add value to distributed solar power. Maui, for one, hopes to “mitigate voltage fluctuations caused by variability of PV systems, contribute to grid stability during frequency excursions and faults, and report real‐time PV output to both the utility and customer,” the DOE’s announcement says -- a long list of functions that could actually earn money on top of solving intermittency problems, if inverters are smart enough to manage it.
But without smart inverters of some kind, utilities can’t even know exactly how many of their customers have rooftop solar, let alone how much power they’re generating. That can become a problem as on-again, off-again solar power starts to destabilize the grid. Solar power is more predictable than wind power -- it’s easier to see clouds coming than to measure how fast the wind is blowing from second to second -- but it’s also less well-connected to sensors or controls, particularly at the residential rooftop level.
A slew of projects are trying to fix that problem, including DOE’s SEGIS (Solar Energy Grid Integration Systems) projects (check out Petra Solar’s big one in New Jersey), and now the SunShot program. Germany, where some towns already get 20 percent or more of their power from rooftop solar, is considering a law to force new rooftop PV inverters to be able to “ramp” their power up and down slowly, rather than tripping on and off all at once, since cutting 20 percent of a local grid’s power in one go is sure to cause major blackouts.
Silver Spring, which is waiting to launch the most anticipated smart grid IPO of the century (so far), recently announced a networking partnership with microinverter maker Enphase. Developer Clean Power Finance, which just landed a $75 million fund from Google, has said it plans to start using the mash-up to manage its solar portfolio.
It’s far from the only networked inverter system out there, of course. Solar power developers like SunEdison already monitor their solar panels, since they own the asset and are responsible for collecting payments, calculating their value for tax incentives and the like.
How developers manage their solar power, on the other hand, depends on their project-by-project mix of inverters, microinverters and monitoring and control interfaces. Enphase, for instance, uses its own powerline carrier technology to link its microinverters, though it bridges to Silver Spring’s network at key points.
SolarCity, for its part, actively manages the solar arrays it installs on its customers’ rooftops, and co-founder and COO Peter Rive told me in September that the company was looking at more complex control capabilities as well, though he wouldn’t provide details (I wonder if the SunShot announcement was what he was talking about?). Still, we’re seeing pressure from regulators to get inverters to speak a common language, so to speak, if only to tell different types of smart grid networks whether they’re on or not.
As for Fronius, the inverter maker participating in the SunShot projects, it and fellow incumbents SMA, Power-One and KACO New Energy hold a 60-percent market share in global PV inverter shipments. All of them are working on smarter inverters, of course. The big question that remains, however, is how fluent they will be in the new polyglot world of smart grid communications.