Energy storage may still be unaffordable for some homeowners, but installing solar panels so batteries can be added later can make the transition smooth when they’re ready to make the investment.
In California, this practice will be mandatory for new single-family homes starting in 2023. According to the California Energy Code 2022, these houses that are already equipped with solar systems must be wired so that energy storage can be easily added later. This includes installing a 225 amp minimum busbar, four fused circuits (two of which must be the refrigerator and socket in the bedroom), and either a sub-panel or a split-bus main panel for those circuits.
There are a number of other considerations that can make the life of both the installer and homeowner easier when planning storage-ready solar projects.
Installers should carefully consider what type and brand of inverters to use for solar projects if storage is planned as a later addition. Hybrid or battery-compatible inverters are built in such a way that they can accommodate a battery on the DC side. In the event of a power failure, hybrid inverters connected to batteries can temporarily switch to off-grid mode and continue to supply the house with electricity.
“Inverters are getting more sophisticated in the way they interact with the grid, so we have our advanced technology inverters that can respond to grid conditions to support the health of the grid,” said Ken Boyce, senior director of Principal Engineering, industrial, at UL.
To add storage to microinverter-based systems, an additional inverter must be installed to connect solar and storage. Manufacturers of AC-coupled systems such as Tesla integrate both the battery and the inverter in one housing.
Californian installation company Renova Energy is a SunPower dealer that installs AC modules that convert power to the panel.
“We need to keep the same technology in the way we build our solar systems, so we immediately looked into AC-coupled battery systems like Tesla,” said Matthew De La Torre, VP of Engineering at Renova Energy.
If the battery supply is not available or the customer is not ready to invest in storage along with solar energy, Renova will sometimes upgrade the main power supply panel, install an additional sub panel and add extra wiring to easily connect a battery in due course.
“Some of the things we do are enlarge the conduit or add extra conduit between certain electrical boxes and components so that there is much less drywall or stucco work when installing the battery,” said De La Torre.
Batteries added on the AC side of the system will change the capacity of the project on the nameplate, which would change the homeowner’s interconnection agreement with the utility and require a reassessment.
“I hope that when people add AC coupled storage they will see that it increases the capacity on the nameplate and requires a new connection application or a revised connection application. For some of these things, it may not be entirely obvious that this should be done, ”said Brian Lydic, senior regulatory engineer with the Interstate Renewable Energy Council.
Even DC-coupled storage systems could change the times of day at which a homeowner can feed electricity into the grid, so the utility should be informed about this. The utility may need additional equipment such as a power control system or other evidence that the battery is only set up to be charged from the PV system to ensure that the installation complies with export regulations.
“The DC-coupled solution will likely still be simpler from an interconnection process perspective, but you may still need a power control system to walk the process depending on how flexible your storage is compared to how you use it with yours Have used PV system, ”said Lydic.
Power control systems are combined hardware / software solutions produced by certain inverter manufacturers. They are programmed to manage energy exports to meet the restrictions of the distribution system and also to demonstrate compliance with net metering rules. Solar + storage projects are usually approved more quickly by the utility company when this automated system is installed.
“Some utility companies have put restrictions on how energy stored in an energy storage system can be fed back into the grid. “This can be very helpful in building trust, as more and more energy storage devices are used.”
Security and Compatibility
Regardless of whether the future storage system will be AC or DC coupled to the solar project, safety and compliance with regulations are of the utmost importance.
“It is really important that the specific combination of the battery system and inverter has been tested for safe compatibility,” said Boyce.
Inverters and batteries from the same manufacturer are the easiest choice to ensure compatibility, but different brands are often used due to existing partnerships and product preferences. Compatibility can be tested by laboratories such as UL or in the field. All projects are inspected by the local AHJ to ensure that equipment is properly installed.
“One of the challenges is that the electrical ratings of the system can change as you start adding different sources or changing the capacity of your sources or adding different components like energy storage systems.” “We always want to ensure that the equipment used in this system has the appropriate electrical ratings to handle the actual electrical load.”
With a view to the future of smart homes, some manufacturers offer self-sufficient power control systems. Schneider Electric recently launched its Square D Energy Control Center (ECC), an all-in-one housing that integrates the home’s main panel and backup panel and contains inputs for solar inverters, batteries and generators. In conjunction with the company’s EcoStruxure Microgrid Operation (EMO), the system can autonomously instruct the energy control center to charge, discharge, or idle a battery depending on the optimal energy use throughout the day, taking into account electricity tariffs, peak loads and load Spikes.
“You’re building a solution that expects you to come back and add a generator,” said Brad Wills, director of strategic customers and programs at Schneider Electric. “You literally come back and add the battery to the existing enclosure and you don’t add another enclosure, you don’t tear open the drywall, you don’t have to re-plaster the outside of the house.”
Power control systems give homeowners the flexibility to choose and change which critical devices provide backup power when storage is added to the system. Manufacturers like Lumin and Span make standalone smart circuit solutions that would also be helpful for future storage expansion, but Schneider’s product functions as both a smart circuit and a microgrid management solution.
“It is not an isolated case that someone has more than one source of energy. That’s the new standard and it’s going to happen, so why not build the house to be prepared? ”Wills said.