A recent Greentech Media article brought to light new details about a lithium battery fire at the Arizona Public Service (APS) McMicken Energy Storage facility that occurred in April.
According to GTM, the fire involved a thermal event affecting one battery rack but not a thermal runaway event affecting multiple battery racks. This is very good news, as we’ll explain below. The article also suggests that venting energy storage enclosures to release combustible gases may be a solution. We respectfully disagree.
We still don’t know the root cause of the fire. However, we know enough to conclude that more ventilation is not the best approach to battery fire prevention. We also know that storage projects need a failure plan, and they need to comply with higher standards.
Read on for our recommendations to help energy storage contractors prevent lithium battery fires.
No thermal runaway
After the Arizona fire, an investigation from APS and battery provider Fluence found that only one battery rack containing 14 modules had “melted.” Evidently the fire did not spread to adjacent racks, setting up a more hazardous thermal runaway scenario, which could have added to the fire’s propagation many times over.
This is encouraging. It’s not the failure of a single cell, but rather the propagation of that failed cell that causes all the damage we see in lithium fires. We should understand why the propagation stopped at the rack level. Here are a few possibilities.
(A) The spacing between racks in the system design was wide enough to stop the fire’s propagation in other racks.
(B) The original equipment manufacturer’s design of the battery pack itself helped prevent rack-to-rack propagation.
As the investigation proceeds, we hope to understand not only the root cause of the APS fire but also the design criteria that helped prevent rack-to-rack thermal runaway. APS is reporting investigation updateshere. Independent research and third-party lab testing can also produce findings that improve design and engineering for battery safety.
Venting is not the answer
APS director of technology innovation and integration Scott Bordenkircher told GTM that the McMicken facility fire will prompt engineering and design changes, balancing fire suppression with the removal of explosive gases.
A better answer might be to make sure fire response professionals do not open containers designed to enclose and isolate what’s inside. Do we know enough today to arm firefighters with the correct training to protect themselves and suppress fire? A system designed to fully contain explosive gases may be part of the solution rather than the problem. While investigating ways to improve lithium battery safety, it’s also a good idea to explore best practices for first responders.
Root cause unknown
While it is encouraging that rack-to-rack propagation did not occur, the root cause of the APS fire is still unknown. A root cause analysis will help engineers modify future designs to improve lithium battery safety. Following the chain of events backwards to the point of origin (modules within the rack, cells within the module, and down to the cell level) can yield key insights.
If the root cause of the fire was truly “spontaneous,” which is a real possibility when large quantities of lithium cells are manufactured, no design or manufacturing changes can eliminate the possibility of another freak accident occurring. We may have to accept that spontaneous lithium failures are inherent in lithium technology and manufacturing processes. If this is the case, the best we can do is focus on controllable areas of fire suppression, isolation, and safety at the component- and system-level, rather than at the cell- or module-level.
With that in mind, what can energy storage companies do to eliminate or mitigate lithium battery fires? Here are two recommendations.
Plan for failure
In the event of a lithium battery fire, projects need clear and well-documented protocols to assist in fire suppression, cleanup, and investigation. These prevention and remediation plans ought to be provided as part of the project-specific safety plan or permitting process. This would ensure the information is provided to local authorities and site personnel. System design should also be informed by the possibility of system-level or component-level failures. Fire, building, chemical, and electrical safety codes and standards may be consulted and referenced.
For instance, in the APS fire, the bad rack was positioned in the middle of several batteries that maintained a 90% state of charge. As a result, the APS/Fluence team spent 9 weeks removing and de-energizing all of those batteries.
“There was absolutely no playbook,” Bordenkircher told GTM.
If this experience leads to the creation of a proactive project failure plan, that would be a positive outcome. It could help guide future safety code iterations and standards development.
In addition, it is interesting that APS used LG Chem batteries. According to SepiSolar research, LG Chem batteries have among the widest temperature range needed to initiate thermal runaway. LG Chem batteries also have a fire incident history that reportedly led the battery maker to shut down some of its own storage systems in South Korea.
Raise project standards
The risk of a lithium battery fire is lower in residential and commercial applications than in utility installations. The reason: such projects must comply with the UL 9540 and NFPA 855 safety standards. Utility projects, on the other hand, are basically self-regulating.
UL 9540 addresses construction, performance, and testing of energy storage systems, including how the system handles combustible concentrations and fire detection and suppression.
If we hold utility projects to higher safety standards, battery fire risks will go down.
Improve risk management
It’s more important than ever to understand and manage the risks associated with energy storage projects. That’s why SepiSolar is writing about the APS battery fire and why we will continue to write about it.
Our experience balancing cost, speed, and safety in energy storage projects contributed to the development of the new C&I Project Risk Management Guide. Download a free copy today.
When I saw this article about LG lithium-ion energy storage fires in Korea, I couldn’t help but think of the fires that PG&E is being held responsible for in California. Those fires have ultimately lead PG&E into bankruptcy and will inevitably increase energy costs to ratepayers.
It’s amazing how something as seemingly simple as a campfire, power line, or a 18650 lithium cell—about the size of a lipstick container–can cause so much damage to California, one of the wealthiest states in the world and PG&E, the largest utility in the state, and, of course to the loss of lives and homes.
Some of these hazards defy logic or at least expectations. When SepiSolar was providing technical due diligence and engineering review services to NRG Home Solar from 2014 – 2016, we came across residential projects on the East coast that had unexpected dangers. For example, there was a solar PV system installed on top of the garage where snow had piled up on the PV system. Some rain had turned that snow into a giant slab of hardened ice. When the ice slipped off the solar array, it crushed the car parked in the driveway–not dented, dinged, or scratched. It completely totaled the car. The homeowner told us “that’s exactly where my children play in the summertime.”
Having just become a father at the end of December 2018, I think it’s fair to say that safety cannot, should not, and will not ever be taken for granted on my watch.
Risks vs Benefits
I don’t mean to suggest that we ought to over-design, over-engineer, over-regulate, over-install, or somehow bullet-proof every single component or assembly in a traditional solar or storage system. That’s like saying “Since car accidents kill people, let’s require everyone to drive army-grade tanks down the street.” That line of thinking effectively kills an industry and becomes a zero-sum game. Instead, I would pose that taking risks is a part of life and is healthy for us, since taking risks and stepping outside our comfort zones is exactly how we grow, learn, and evolve.
The goal is to take calculated risks, or, alternatively, educated risks. What’s a calculated risk? It’s a risk that you’re aware you’re taking. The difference between educated risks and blind or reckless risks is awareness.
We then need to weigh those risks against the benefits in order to make effective decisions. After those decisions are made, we need to be ready to revisit them again soon because the learning process never stops. Assumptions will need to be revised, data recalculated, risks revisited, benefits re-weighed, and decisions re-evaluated. This is how we evolve and approach an ever-safer future, together.
So, let’s build some awareness, shall we? Let’s have a data-driven discussion about the fire risks associated with energy storage systems, and let’s turn our blind risks into calculated ones. Having helped build Green Charge Networks into a nationwide energy storage integrator (acquired by Engie in 2015), engineered solar and battery systems for over 10+ years, and having worked with utilities, UL, code officials, etc. on safety standards, I think I might have a thing or two to say about this subject.
Evaluate the Energy Storage Technology
To minimize risks in energy storage, perhaps the most obvious approach is to work with a technology that inherently works with chemicals and materials that have no fire risk associated with them. This is particularly difficult with batteries because when almost any battery is short-circuited, they instantly become a fire hazard. But that’s the nature of batteries – they can produce insanely high amounts of current, since the resistance in the battery circuit is governed by however fast (or slow) the chemicals involved can react with each other, allowing the free flow of electrons to accumulate. Of course, these chemicals are designed to react with each other in order to release electric charge. So, fire hazard is almost inherent in any battery (with at least 1 exception).
I love this side-by-side technology comparison authored by Fire Captain Matthew Paiss, a 22-year veteran of the San Jose Fire Department. Captain Paiss is the Fire Department’s subject matter expert on energy storage and is the IAFF primary representative to NFPA 70 (National Electrical Code) and NFPA 855 (Energy Storage System Standards), which has been incorporated into UL standards such as UL 9540. It was surprising and gratifying to know that there’s at least 1 technology that rises above the rest when it comes to safety.
Codes & Standards
There are a ton of uber-smart tradesmen, engineers, officials, and subject matter experts who love to wordsmith and craft codes and technical language (God love them!) in order to impose a minimal, universal set of health and safety standards designed to protect personal property and life. Some of these codes go all the way back to 1897, as is the case with the National Electrical Code, when electricity was thought of as a liquid! (Check out Leyden jars.)
Bottom line, let’s be sure to read and understand the modern codes thoroughly, including NFPA, NEC, UL, among others. Every word, comma, and comment were crafted with the care one would expect of a nationally applicable set of requirements, even if you disagree with many of them. It’s important to follow voltage, current, and sizing requirements, naturally. NEC 706, for instance, was just added to the NEC in the 2017 edition. That’s the first time batteries have been overhauled in the NEC since Article 480 was written back in the early 20th century! Let’s expect this new code section to evolve with the times as more data becomes available and continue to think of these codes as a “minimal” set of safety standards that we can go above-and-beyond as necessary to ensure the safety of the systems we design and build.
While codes and standards are important, one of their drawbacks is that they are slow to change. Technology and data often evolve faster than codes and policies. Because of this, it’s important to look at the data, stay up-to-date on the latest-and-greatest information available, and dynamically build this data into your systems as it becomes available. Basically, I’m advising you to read. Read articles, publications, journals, media newsletters, and absorb as much as possible to keep up-to-date.
For instance, now that the above Korean article has surfaced about LG battery fires, it’s imperative to find out the root cause failures that led to these hazards. There is much to learn from failure, thereby converting failure into learning opportunities (which perhaps negates the use of the term “failure” in the first place – nothing is a failure, so long as you learn something from it!). We don’t have to wait for new technologies or new codes to come out. Instead, let’s use the data right away in any or all systems that we may be using with LG batteries, or any battery, for that matter.
The first time I thought about the risks associated with batteries was when I heard that Boeing grounded the Dreamliner. Our Co-Founder and CEO of Green Charge Networks at the time was a retired Boeing executive, so this naturally caught our attention. Wikipedia does a decent job summing up that experience, and you can get the full investigative report here.
The general takeaway is that regulatory bodies, manufacturers, and engineers were not “up to snuff” on the risks associated with battery technology. To a great degree, as the above Korean article shows, we are still learning these risks. At our time at Green Charge Networks, we understood that this meant that the safe deployment of battery systems would largely rest on us, since codes, standards, products, and regulations were still too much in their infancy to support us.
Direct Experience and Training
Nothing prepares you for danger, uncertainty, or risk more than education, experience, and training. The more hands-on experience you have with a particular product or technology, the more you will understand its limitations, weaknesses, and risks. Understanding not only what and when a battery undergoes thermal runaway, but also the “how” can really help put battery risks into perspective. What I learn from this is that it’s not just the battery one should be cautious of, but also the environment the battery is in. For example, does the battery have a fire suppression system? Is the battery located near any buildings or structures that have no fire suppression?.
One time I dropped a wrench on an old golf cart battery, and it just so happened that the wrench landed perfectly on both positive and negative terminals simultaneously. It was the first time I saw metal turn bright red, orange, and then white, and eventually melting all over the battery. This was just a regular ol’ lead acid battery, so it was surprising to me that such an old battery could have such a great impact on something as solid and stiff as a wrench. Needless to say, I am very cautious around terminals of batteries, since most batteries cannot be inherently turned “off” (again, with some exceptions).
In a nutshell, if you’re working with lithium batteries, make sure to identify the risks and retire them as much as possible. For instance:
HVAC systems for lithium are not just there to support battery performance, but they are safety devices as well. Make sure they’re appropriately sized and adequate for the operating environment the batteries will be in.
Lithium batteries that get too hot can result in thermal runaway, and other types of hazards, aside from accelerated degradation of the cell capacities and efficiencies. Fire suppression systems are required with the appropriate cleaning agents.
Closely monitoring and isolating cells that are approaching their end-of-life is critical. Battery degradation not only leads to capacity loss, but also battery failure.
There are many other aspects to keep in mind, and nearly all are avoidable if you’re aware of them in the first place.
I strongly believe that lithium-ion battery systems will continue to grow and thrive in our new renewable energy world, but as the Korean article shows, there are risks. As engineers, it’s our responsibility to be aware of these risks, evaluate them, and to find the solutions that will decrease those risk and perhaps even eliminate them with new safety innovations.
Update: On January 31, 2019, The CPUC unanimously passed this landmark update to California net metering for energy storage. Read SepiSolar’s white paper to see why this change will “super size” solar with storage.
SepiSolar has released a new white paper that reveals significant financial benefits of a California net energy metering policy decision for DC-coupled energy storage
FREMONT, Calif. – Dec. 11, 2018 – A new SepiSolar white paper reveals the financial benefits of a pending revision to California’s net energy metering (NEM) policy. When finalized, commercial DC-coupled solar-plus-storage installations will not only be able to benefit from NEM, but will also be able to increase solar system size, reduce installation and permitting costs, and quicken interconnection approval time.
On Oct. 5, 2018, the California Public Utilities Commission (CPUC) issued a proposed decision to modify CPUC Decision 14-05-033, the NEM tariff policy for solar and energy storage. Once approved, the change will allow DC-coupled energy storage systems to become eligible for NEM without the need for thousands of dollars in extra hardware costs and burdensome verifications required by California utilities and the IRS for AC-coupled energy storage systems.
To take advantage of this policy change, contractors will need to design solar systems with DC-coupled storage and procure DC-coupled energy storage products that incorporate a new Underwriters Laboratory (UL)-verified inverter firmware solution. NEXTracker’s NX Flow™ energy storage system piloted this firmware solution with UL, and is therefore expected to be the first DC-coupled energy storage product approved for the new regulation.
SepiSolar’s white paper reviews and compares the historical challenges of designing AC-coupled and DC-coupled energy storage systems for NEM. It also describes how the new NEM DC-coupled policy and system design will eliminate the need to purchase the extra equipment required for non-export AC-coupled systems, such as reverse-power relays, an additional utility meter, switchgear and a second inverter.
“This policy does more than just reduce equipment costs,” said Josh Weiner, CEO of SepiSolar and author of the white paper. “Businesses can now store their excess solar power in a battery system and receive demand charge benefits as well as the financial benefits from NEM. Another benefit is that solar systems can now be ‘supersized’ to exceed the 1 MW behind-the-meter interconnection soft limit. With a DC-coupled design using products that have the UL-verified firmware, excess generation over 1 MW can now be stored in the battery and later exported into the grid at favorable or optimized NEM or NEM-aggregate tariff. As a simple example, a 1 MW stand-alone solar system can be increased to 2.8 MW with a complementary DC-coupled 1.8 MW storage system and a 1 MW AC inverter that uses the new firmware.”
The same DC-coupled system design may also eliminate the need for utility infrastructure upgrade costs. These costs are most often charged to the solar asset owner when the solar system’s export generation is over 1 MW. Typically, the owner either pays for the upgrades or decreases the system size. With the new DC-coupled configuration, solar-plus-storage systems can be designed to meet the location’s grid capacity, reducing the need for upgrades. Any excess solar can be stored and later exported at up to 1 MW intervals. In models developed by SepiSolar, adding DC-coupled energy storage under the pending NEM policy is usually much less expensive than the cost of grid infrastructure costs without storage.
The simpler DC-coupled design also will allow solar+storage systems to qualify for expedited interconnection, reducing difficult verification requirements for utility interconnection, expediting interconnection. Finally, with the UL-verified firmware, tax equity investors and utilities receive independent verification that the storage system is only exporting solar generation and not charging batteries from the grid. This verification is important for qualifying energy storage systems to receive the 30% investment tax credit.
The proposed CPUC ruling for NEM for DC-coupled solar-plus-storage systems is expected to gain final approval by the end of 2018 or early in 2019.
How do you sell C&I energy storage without overwhelming prospects with jargon and giving just the right amount of technical and financial modeling information? SepiSolar’s CEO Josh Weiner and Systems Engineer John Henley will be answering any C&I energy storage sales and financial modeling questions at our next Ask SepiSolar Anything, Tuesday, August 14, at 11 am Pacific/2pm Eastern!
From demand charge reduction to energy arbitrage or backup power for critical loads, commercial and industrial businesses turn to solar+storage for many different pain points. Some are financial, some have to do with grid reliability, some want self-sufficiency, and some have corporate sustainability goals. And then there are those facility managers who will pay almost any price to keep their machines and data centers running 24/7 during the next natural disaster.
SepiSolar’s Josh Weiner and John Henley have years of experience consulting with clients on how to sell and design C&I energy storage from a technical sales perspective, providing easy-to-digest language and data points that don’t overwhelm prospects with jargon or too much information.
After a brief sales tips and best practices presentation, Josh and John will answer any question about energy storage sales and financial modeling for your C&I solar+storage prospects. RSVP to this interactive “Car Talk for Solar” webinar!
“Where are we on the energy storage adoption curve?” That’s one of the questions a participant asked at our latest monthly Ask SepiSolar Anything “Car Talk for Solar” webinar series. It’s the only place on the web where solar professionals can ask SepiSolar’s solar+storage engineer experts anything about a particular renewable energy topic.
For July, our topic was to Ask SepiSolar Anything… about battery storage technologies. That is, about the technical aspects of different battery chemistries on the market today.
To offer a broad view than the typical Lithium-ion energy storage landscape, SepiSolar’s CEO Josh Weiner invited Matt Harper, the Chief Product Officer and Co-Founder of Avalon Battery, a Vanadium flow battery company based in Fremont, California.
Together, Josh and Matt tag-teamed on the answers, offering various perspectives and case study examples of their years of experience in developing and modeling energy storage for various applications.
From the live audience at Intersolar and on the web, we received the following questions. Jump to the topic that most interests you in the time stamp at the end of the question:
Overview of Energy Storage Technology Landscape 00:01
Matt Harper briefly describes Avalon Battery and its Vanadium flow battery technology 01:40
Question 1: Please give a concrete example of a project that has integrated electric vehicles with solar and storage in some kind of a project or a use case 07:00
Question 2: There are a lot of flow battery technologies out there. Zinc Iron, Zinc Bromide, Iron-Iron, etc. Why Vanadium? What makes it so special? 12:48
Question 3: If you have a grid-tied inverter already installed, how would you integrate a battery into that, perhaps aftermarket? 17:55
Question 4: What are the HVAC requirements for Avalon and other flow batteries? 21:27
Question 5: Does the efficiency level of Vanadium Batteries change at cold temperatures? 27:30
Question 6: I have an existing PV array that uses SMA inverters, two strings with a total of 6kW. Can it work with a flow battery? 29:20
Question 7: Where are we on the energy storage adoption curve? i.e., Utility vs DG projections? 45:51
Question 8: When will batteries—of all kinds—be cheap enough and available enough to combine with solar, wind, etc and replace a baseload natural gas plant. That is when will utilities have a choice between a baseload natural gas plant and a solar+storage plant? 47:04
Have a question about selling solar+storage for commercial projects? Then tune in next month for Ask SepiSolar Anything about Selling C&I Energy Storage. Click the button below to sign up!
If you’re not already installing solar+energy storage for your customers, you soon will be. But which energy storage technology is best? What’s the price per kWh? How long will the battery technology last? Are Lithium-based batteries really the best? How expensive are flow batteries? How about flywheels?
You can ask any of these questions–or anything else–and get an answer from SepiSolar’s CEO and storage expert, Josh Weiner. Also answering your questions will be our special battery technology guest, Matt Harper, Chief Product Officer of Avalon Battery.
Before Avalon, Matt was a former VP of Products and Marketing at Prudent Energy and has 9 years developing energy storage technologies. He holds 7 US patents.
In addition to being CEO of SepiSolar, Josh has been designing solar+storage systems since 2004 and was one of the early co-founders of Green Charge Networks (recently acquired by Engie.). He now consults with developers, as well as various storage manufacturers.
Over the years, Josh and Matt have separately studied many different battery technologies, and they’re both excited to be sharing their objective knowledge and opinions, answering any of your battery technology questions LIVE at the EES stage at Intersolar or on our usual web platform at the same time.
Join us for Ask SepiSolar Anything – Live from Intersolar!
Topic: Ask SepiSolar Anything about energy storage technologies. Josh will be answering questions with our special guest, Matt Harper, Chief Product Officer of Avalon Battery.
When: Thursday, July 12, at 1 pm Pacific.
Where:Sign up to get a link to watch via the web or be in the audience at Intersolar. Get all the info and a reminder here:
P.S. If you or your company are on Twitter and want to meet other solar people behind the solar brands on Twitter, RSVP for the 8th Annual Intersolar Tweetup, which @SepiSolar is sponsoring. Space is limited so get a ticket before Intersolar!
If you missed our first Ask SepiSolar Anything with SepiSolar’s CEO Josh Weiner answering solar+energy storage questions, you can’t ask any more questions, but you can listen to the whole session here:
Josh tackled some great questions from people tuning in to this live and interactive program:
What are some of the common KW inverter sizes for C&I solar+storage? (at 11:12)
When you’re doing solar PV plus storage, what kind of interconnection requirements, like 120 percent rule, do people face? Are you seeing more AC or DC coupling on the system? (at 13:20).
For commercial solar+storage, who are the customers that would benefit the most from solar+storage, and who are the customers that aren’t yet ready? (at 20:40)
What type of energy storage is available and viable for the Florida residential and commercial market? Which brands? Also, does storage benefit from the 30% ITC credit if installed in conjunction with solar? (at 26:00)
For O&M requirements for lithium-ion batteries for C&I solar+storage applications, is there maintenance required on a yearly basis? Or is it bi-yearly? What kind of components need to be serviced? What kind need to be replaced? (at 30:15)
Is there an unbiased accurate chart from an independent testing lab of expected life cycles of all that all the battery brands? (Short answer, yes, but there’s only one that’s public.) (at 38:02)
How does energy solar PV and energy storage work with virtual net metering and aggregate net metering? (at 43:22)
What is the unit based cost for battery O&M? (at 47:10)
Join us for our next Ask SepiSolar Anything
If you have more questions about solar+storage, or energy storage or anything related to solar, join us for our July edition of Ask SepiSolar Anything. You can be in the audience and ask your questions live at Intersolar North America or tune in virtually.
Topic: Ask SepiSolar Anything about energy storage technologies. Josh will be answering questions with our special guest, Matt Harper, Chief Product Officer of Avalon Battery.
When: Thursday, July 12, at 1pm Pacific.
Where: Sign up to get a link to watch via the web or join us live at Intersolar. Get all the info and a reminder here!
P.S. If you’re on Twitter and want to meet other solar people behind the solar brands on Twitter, RSVP for the 8th Annual Intersolar Tweetup, which @SepiSolar is sponsoring. Space is limited.
If you’re an architect, new homebuilder or housing developer in California, you’ve probably heard by now that the California Energy Commission (CEC) has updated its Title 24 solar and energy efficiency standards. Effective January 1, 2020, the update specifically mandates that all new California homes under three stories install solar panels on the roof or achieve an equivalent total home energy efficiency reduction through other measures.
To comply with Title 24, new homebuilders, architects and developers will be required to use Title 24’ssoftware for calculating the building’s “Energy Design Rating” (EDR), which not only includes inputs for solar but also for energy storage and other options.
To give builders more flexibility, the EDR is scored like a golf tournament—the lower the score, the better (or, the more “energy efficient” the home is). The goal is to achieve an equal-to-or-less-than EDR for a solar home than a comparable “regular” home, of the same square footage.
Depending on the square footage and climate, new-home solar will range between 2.7 and 5.7 kW DC to meet the requirements, but that doesn’t tell the whole story. Rather than meeting the minimum requirements, builders may be better off designing their Title 24 solar systems with battery storage.
Why Builders Should Include Storage with Solar
As mentioned, the EDR software gives homebuilders a score, but there are many ways to meet that score, and one is combining solar with energy storage. Including energy storage will not only meet the minimum solar requirements, but will maximize energy savings for the home, offering customers a financial advantage over other homes.
When solar engineers design a solar system, they typically take into consideration the following factors:
The average amount of sunlight for the area
The orientation of the roof in relation to the sun
The amount of potential shading over the course of the year
The pitch of the roof
The home’s annual kWh usage
While these parameters are important, equally important are the utility rate considerations that system designers like SepiSolar factor into their plan sets. These rate policies affect the solar system’s ROI and include:
Tiered Rates. Tiered rates vary by utility and charge customers higher rates when they use more energy over a certain monthly amount.
Net Energy Metering (NEM). NEM is like rollover minutes for solar. Utilities will credit solar homeowners for any excess solar power that is exported to the grid. The value of NEM varies by the utility and the time of day that the solar is exported to the grid.
Time of Use (TOU). TOU rates also vary by utility. Customers incur charges when they use grid energy. During peak times, such as rush hour when the sun is setting and people are coming home, utilities charge solar and nonsolar homeowners a higher rate when they draw power from the grid, making any exported solar energy less valuable during that time of day.
That’s where energy storage (batteries) comes in.
Designing Systems for Overall Cost Savings for Solar and Title 24
Due to the above utility rate considerations, home developers that want to design premium homes that maximize utility savings as well as comply with the Title 24 solar mandate should consider including energy storage systems with their solar designs.
Solar+storage with smart battery management software will counteract the cost of tiered rates and TOU through “load shifting,” and “peak shaving.”
With peak shaving, homes using solar+storage will be able to use as much free solar as they can during the highest TOU rates while saving the excess energy in their batteries instead of exporting to the grid. Then, during peak TOU periods, the home will use this free stored solar-generated energy when the utility rates are high.
Additionally, battery management systems can also “load shift” the time when appliances are turned on or off, such as turning on a dishwasher, dryer or charging an EV when utility rates are low or when electricity can be drawn from the battery that was charged by solar.
Both peak shaving and load shifting with solar+storage encourage the home to use more of its own self-generated power, relying less on importing power from the grid. With so many homes using solar after 2020, homeowners with solar+storage will also help stabilize the grid, and can be paid a higher credit for any power the utility draws from the storage system during peak hours.
Another sales advantage for developers is that solar+storage offers some emergency power in case of a blackout. That is not the case with stand-alone solar PV systems. To protect power line repair workers, stand-alone solar systems will automatically shut down during an outage.
Things to Keep in Mind About Solar+Storage with Title 24
If you decide to meet your Title 24 solar mandate with energy storage, there are several requirements to keep in mind.
First, when adding storage to solar, there is a minimum required battery size of 5 kWh. This is a reasonable size that will allow for taking advantage of tiered rates and TOU, and it will provide a minimal amount of backup power in case of an outage.
Second, your solar+storage system designer and engineer will have to select one of three control options for the battery:
Option 1 – Basic Control (Title 24, Section JA22.214.171.124): With Basic Control, the battery system can only be charged by the solar system and can only discharge when there’s not enough solar power to meet the home’s current energy usage.
Option 2 – TOU Control (Title 24, Section JA126.96.36.199): With TOU Control, battery system will be set up with Basic Control, but will only discharge during the peak TOU hours of the day. This will change from season to season, and must be configured from the battery manufacturer or programmed by the installer at the time of commissioning.
Option 3 – Advanced Demand Response Control (Title 24, Section JA188.8.131.52): With this configuration, solar+storage systems will be programmed with Option One or Two. In addition, the battery control system must meet the demand-response requirement of a utility or third-party owner; that is, the utility or third party will be able to remotely control when the battery is charged and discharged. Typically, the homeowner will receive a financial benefit for this utility interaction with the grid.
The rules within each category will most likely be refined over time, so it’s important for your solar designer to be up to date with these standards and make any necessary changes. The above is a summary, so please review the entire Joint Appendix 12 to take full advantage of the above credits.
As longtime solar+storage engineers with thousands of projects, SepiSolar has a great deal of experience designing solar and battery systems that meet the new Title 24 regulations, as well as designing systems that comply with the local requirements of counties and other local authorities having jurisdiction (AHJs). Please contact us if you have any questions about these new Title 24 solar requirements for your new residential solar development projects.
Josh Weiner is President and CEO of SepiSolar, a solar+storage design & engineering firm based in Fremont, CA.
SepiSolar’s Josh Weiner was recently interviewed about trends in solar+storage design and engineering by Barry Cinnamon on “The Energy Show,” a radio program on KDOW Radio AM in San Jose California, as well as a popular solar industry podcast.
Josh and Barry have a long solar and storage relationship together going back to when Josh was leading Barry’s engineering department at Akeena Solar, the first national solar installation company. Their lively conversation talks about solar and storage trends, which includes a conversation about some new and improved alternatives to Lithium Ion-based storage systems.
Click below to listen to the show on SoundCloud, or you can also download it as a podcast on Itunes here.