Not ready to buy a battery today? Here’s how to prepare your solar project for future energy storage
Energy storage can still be prohibitive for some homeowners, but installing solar so that batteries can be added later can smooth the transition when they’re ready to make the investment.
In California, this practice will be mandatory for new single-family homes beginning in 2023. The California Energy Code of 2022 says that these homes, which are already required to contain solar installations, must be wired so that energy storage systems can be easily added later. That includes installing a busbar of at least 225 amps, four backup circuits (two of which should be the refrigerator and the outlet in the bedroom), and a sub-panel or a main panel with a split bus for those circuits.
There are a number of other considerations that can make life easier for both the installer and homeowner when planning storage-ready solar projects.
Installers should carefully consider the type and brand of inverter to use for solar projects when storage is planned as a later addition. Hybrid or battery powered inverters are ready to accept a battery on the DC side. In the event of a power outage, battery-powered hybrid inverters can temporarily switch to off-grid mode and continue to power the home.
“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 grid health,” said Ken Boyce, senior director of principal engineering, industrial , at the UL.
To add storage to microinverter-based systems, an additional inverter must be installed to link the solar power and storage. Manufacturers of AC-coupled systems such as Tesla have both the battery and inverter in one housing.
California installation company Renova Energy is a SunPower dealer that installs AC modules that convert the electricity at the panel.
“We need to keep the same technology consistent with the way we build our solar systems, so we immediately started looking at AC-coupled battery systems like Tesla,” said Matthew De La Torre, VP Engineering at Renova Energy.
If battery power is not available or the customer is not yet ready to invest in storage along with solar energy, sometimes Renova will upgrade the main electrical service panel, install an additional sub panel and add an additional conduit to easily connect a battery when the time is there.
“Some things we do are extend conduits or add extra conduits between certain electrical boxes and components so that when it comes time to install the battery, there’s a lot less drywall or stucco work to be done,” De La Torre said.
Batteries added to the AC side of the system will change the nameplate capacity of the project, which would alter a homeowner’s interconnection agreement with the utility and require a re-evaluation.
“I hope that when people add AC-linked storage, they realize that this adds nameplate capacity and that requires a new connection application or a revised link application. For some of these things, it may not be entirely clear that this needs to be done,” says Brian Lydic, chief regulatory engineer at the Interstate Renewable Energy Council.
Even DC-coupled storage can change the hours of the day when a homeowner can export power to the grid, so the utility should be notified. The utility may require additional equipment such as a power control system or other evidence that the battery is set to charge only by the PV system to ensure that the installation complies with export regulations.
“The DC-coupled solution will probably still be simpler from an interconnection process perspective, but you may still need a power control system to get through the process, depending on how flexible you want your storage to be, compared to the way you used it with your PV system,” Lydic said.
Power control systems are combinations of hardware/software solutions made by specific inverter manufacturers. They are programmed to manage energy exports to fit within the constraints of the distribution system and also to prove compliance with grid metering rules. Solar + storage projects are generally approved more quickly by the utility company once they have this automated system installed.
“Some utilities have limitations on how energy stored in an energy storage system can be delivered back to the grid, so there is an option to certify equipment so that the power control system has been evaluated to hinder that type of functionality,” Boyce said. “That can be very helpful in building confidence as more energy storage is deployed.”
Safety and Compatibility
Whether the future storage will be AC or DC coupled to the solar project, safety and code compliance are paramount.
“It’s really important that the particular battery system and inverter combination has been assessed for safe compatibility,” Boyce said.
Inverters and batteries manufactured by the same company are the easiest choice to ensure compatibility, but due to existing partnerships and product preferences, different brands are often used. Compatibility can be tested by labs such as UL or field tested. All projects are inspected by the local AHJ to ensure that the equipment is installed according to regulations.
“One of the challenges is that if you start to add different resources or change the capacity of your resources or you add different components, such as energy storage systems, you can have a change in the electrical ratings of the system,” Boyce says. said. “We always want to make sure that the equipment used in that system has the correct electrical specifications to handle the actual electrical load being presented.”
Some manufacturers are offering standalone energy management systems with an eye on the future of the smart home. Schneider Electric recently launched its Square D Energy Control Center (ECC), an all-in-one enclosure that integrates the home’s main panel and backup panel, and includes 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 use of energy throughout the day, taking into account taking into account utility rates, peak loads and tax spikes.
“You bring in a solution that expects you to come back and put in a generator. It expects if you didn’t put the battery in at the time of installation, you’re going to do that sometime in the future,” said Brad Wills, director of strategic clients and programs at Schneider Electric.”You literally come back and you add the battery to the existing housing and you don’t add new housing. You don’t tear open the drywall, you don’t have to re-stucco the outside of the house.”
Power management systems give homeowners the flexibility to choose and change which critical devices should provide backup power when storage is added to the system. Manufacturers such as Lumin and Span are making standalone smart circuit solutions that would also be useful for future storage additions, but Schneider’s product acts as both a smart circuit and a microgrid management solution.
“It is not a one-time thing that someone has more than one power source. That’s the new standard and it’s going to happen, so why not build the house to be prepared for it?” said Will.