Industry workgroups are developing interoperability standards to accelerate the growth of solar+storage projects.
Adding storage to projects could really help the solar market take off. But how can contractors know if the brand of batteries they’ve chosen will operate correctly with their choice of inverters? Thanks to the SunSpec Alliance, it’s becoming as easy as looking for a sticker.
The SunSpec Alliance is a trade alliance of more than 70 solar and storage industry participants. SunSpec develops and publishes free, open interoperability specifications (also called models) that software developers and hardware manufacturers can use to ensure all their solutions can talk to each other. Since 2012, SunSpec has certified more than 25 companies. So contractors will know components with SunSpec marks can communicate. This takes the guesswork out of a project and makes it easier and cheaper to build projects, therefore accelerating the deployment of solar+storage projects.
Developing standards to ensure project components can all talk through an agreed upon language is kind of like what’s been done with Bluetooth. You can be confident that any headsets or other device with the Bluetooth logo will connect and communicate, no matter what the brand. Establishing the communication requirements for Bluetooth made it easy for manufacturers to know what language their products should “speak,” which has lead them to create many affordable options for consumers, and helped accelerate this area of the electronics market. SunSpec’s goal is to create and enact this same kind of common language that applies across the board in the residential, commercial and utility solar and solar+storage markets.
SunSpec has seen it necessary to step in because if it were up to larger international standardizing bodies, such as IEEE and IEC, to determine standards it would take a long time, thus hindering the growth of the solar industry. Although SunSpec and other working groups would love to get their standards made “official” by these bodies in the long run, having “unofficial” communication standards will allow the solar+storage industry to move along in the meantime.
“Our goal is to move very fast because international standards more very slow,” Tim (TJ) Keating, director of development at SunSpec Alliance, said. “We want to get specifications out so the ecosystem can grow and move on. Over time our specs will get picked up by other organizations and help form long-term standards.”
How it works
SunSpec membership includes a fee and is open to developers, non-profits, service providers and manufacturers on a company or individual level—so contractors are welcome to join. Members of the alliance introduce ideas for specifications based on where they see industry need and then use workgroups to focus on development. This work can take a year or more. Once the specification is in “draft” stage, it’s announced to the industry and open for feedback and ready to be tested in real projects—another chance for contractors to contribute whether a member or not. SunSpec workgroups then use this information to refine the draft and eventually release an updated version.
SunSpec specifications are open licensing models, which means that other entities can adopt and work from them. SunSpec also collaborates with some of these parties, including other workgroups and national labs. It’s a global organization, with international members that implement the standards relevant to different regions.
Spec success stories
SunSpec has developed specifications for components especially crucial to solar+storage projects—standards for meters, inverters and batteries collectively known as SunSpec’s Energy Storage Device models.
“In solar+storage projects, the inverter is almost as important as the battery,” said Keating. “The inverter does the power conversion, so if the grid needs support, high-level commands go to inverter, which can take power from the solar array or batteries. This is why sometimes the inverter control is even more important than the battery control.”
Therefore, SunSpec focused its first standards around communicating with the inverter. building on the industry accepted communication “language” Modbus.
SunSpec also recently released a specification for rapid shutdown. “Different companies have developed different rapid shutdown strategies, which is OK but bad for interoperability,” Keating said. “It’s hard for the installer to know what equipment works with what.”
SunSpec developed a rapid shutdown signaling specification to allow equipment from different vendors—whether chip companies like TI or inverter manufacturers—to talk to each other to shut off. This spec is currently in the draft phase and is open to the industry for feedback and testing.
After its success in inverters, SunSpec turned to developing a communication specification for batteries. In 2014, SunSpec used input from battery manufacturers to develop a standard for lithium-ion chemistries released to the industry in what was called Draft 3. After gathering feedback and data from test projects in 2015, this year SunSpec released an updated draft, known as Draft 4, which provides more guidance for lithium-ion batteries and additional recommendations for flow batteries. Projects incorporating these standards on flow batteries will deploy later this year.
Coming from both sides
While SunSpec was focused on behind-the-meter storage specifications, a separate workgroup—the MESA Standards Alliance—formed to lead the interoperability effort from the utility side.
Darcy Wheeles, program director of the MESA Standards Alliance, said the group formed in 2012 out of a need to standardize how utilities could communicate with storage projects in front of the meter. “There are international standards that address utility communication, but none of them had been expanded to accommodate storage and the breadth of grid services that these devices can provide,” she said. “Utilities were looking at having to spend a lot of time and money on software and engineering to get storage projects to talk to their systems. When we realized international standards organizations couldn’t develop these standards in a time frame that met utility needs, MESA was founded to jump-start the effort.”
As MESA was searching for ways to get started on these communication issues, it discovered the work SunSpec had done from behind the meter and worked with SunSpec to develop the Modbus communication protocols for the components of an energy storage system. MESA then began developing its own specifications, known as MESA-ESS, for a common communication language between in front of the meter storage systems and existing utility control systems. Most utilities use SCADA (Supervisory Control and Data Acquisition) to remotely monitor and control all assets on their distribution system including distributed energy projects like solar and storage.
Just as SunSpec is basing its specifications off Modbus, MESA is basing itsoff off the equivalent standard communication language, or protocol, on the utility side—DNP3.
“The idea is to make storage just another utility resource that can integrate into their existing systems,” Wheeles said. So like SunSpec, MESA is looking at this language to find out what needs to be done to accommodate storage.
“MESA coming from the utility side was a great win for SunSpec because it brought all our work into the utility space,” said Keating.
“We overlap at different points,” Wheeles said. “That’s going to create more robust opportunities for solar to be paired with storage, whether it’s behind the meter or on a larger scale.”
What’s next?
Keating expects more drafts of existing specifications to be released in time, each more refined than the last. On the storage side, members have proposed working on specifications for lead-acid and flywheel technologies. Major topics in the inverter working group include Rule 21 and UL 1741 compliance.
The alliance also received funding as part of the U.S. Department of Energy’s SunShot Initiative’s Orange Button program. SunSpec will create standards that make it easier for the industry to aggregate and share data to help make soft costs related to financing, design, feasibility and operations more efficient and less expensive. Like all SunSpec work, the entire industry (including contractors) is open to contribute.
Wheeles encourages the solar industry to keep innovating. “We want technology suppliers and installers to focus on their core competencies and create really innovative products and projects without having to worry about how these things are actually going to communicate with each other,” she said. “It’s like when you buy a Bluetooth headset; you know it’s going to pair with your phone because all the manufacturers have agreed on a common language. But it doesn’t stop companies from innovating great products. We are working on the Bluetooth of energy storage.”
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