Featured in the January/February Edition of North American Clean Energy Magazine
Energy storage has dominated conversations among solar professionals and the energy industry for the last several years, and as traditional rules of Net Energy Metering slowly fade, energy storage is poised to become one of the most critical components to any renewable energy project.
Currently, rate structures surrounding the simple buy/sell meter are no longer optimized to provide customers with the most value for their solar generation. Utilities have started charging customers for the times that their production capacities are nearing its limits, and for customers, these charges appear either as momentary peak demand charges or hour-long stretches, typically in the afternoon and evening, when energy is purchased at premium Time-of-Use (TOU) rates. Since solar PV generates energy in a bell curve, peaking at noon when energy is cheapest, energy storage is the best option moving forward that gives customers the control to sell those clean solar electrons back to the grid at a premium value.
With more companies offering energy storage solutions, the market has been flooded with an array of battery products, each one more different than the last. Now, the question on every installer’s mind is: which product to choose?
The right battery selection is critical, especially for customers who demand the best. This includes those relying on batteries to support their entire energy load as well as customers who have been burned in the past by entry-level products or lead-acid and are now looking for the most sophisticated technology. Cities prone to weather-related power outages, like those in California and Puerto Rico for example, require reliable products to supply clean drinking water and maintain business continuity.
Given that the majority of end customers know little about the differences between the batteries available to them, installers are tasked with recommending the solution that best suits their individual needs. To find that right fit, there are three key factors to take into consideration: safety, performance, and flexibility.
First and foremost, it is essential to compare the safety of each battery, starting with its chemistry. Understanding that not all batteries are equally safe is paramount, since saving the customer money on their electricity bill or lowering their carbon footprint will be of little value if the battery system introduces hazards to their home and the environment.
For instance, lead-acid batteries require outside ventilation to avoid flammable and smelly off-gassing, and some lithium chemistries, notably nickel cobalt aluminum (NCA) and nickel manganese cobalt (NMC), suffer from potential thermal runaway issues when any part of the system fails. Unfortunately, each of these traits run the risk of starting fires.
Lithium-ion batteries are among the most popular for energy storage, due in large part to high energy density, but the makeup of these batteries can vary tremendously. Lithium iron phosphate (LFP), for example, has proven to be a thermally stable choice for installers, as it is made with materials that are intrinsically safer than other lithium-ion batteries. With this comes peace-of-mind knowing that even in the event of a fire, the battery valves will open to relieve pressure at the cell level.
LFP is also cobalt-free, an added benefit that not only eliminates the need for expensive materials but also avoids the harsh consequences of cobalt mining, including child labor, the inhalation of toxic fumes, and fatality.
Durability and Longevity
The financial payback of a solar PV system hinges on long, hassle-free system performance. Again, knowing that not all batteries are created equal, recognizing the differences between battery maintenance will enable solar installers to provide customers with products that offer the highest return on investment.
Lead-acid batteries typically require monthly maintenance and five-year replacement cycles, while NCA and NMC batteries typically last 10-years between replacement cycles. But, even those with 10-year replacement cycles can be riddled with exceptions.
For example, some manufacturers limit the average depth-of-discharge while others discourage fully charging the battery. As a result, the end customer pays for a capacity that they have no way of fully utilizing. Some battery manufacturers even have strict requirements regarding internet connectivity, in which case a lost signal results in loss of full warranty coverage.
The best option is to look for warranties allowing a 100 percent depth-of-discharge and at least a 15-year performance guarantee.
Each customer’s energy needs are unique, and one-size-fits-all approaches to battery storage can leave many customers with a system that fails to meet their expectations. Flexibility, in regards to both scalability and inverter compatibility, is the third and final piece to selecting the premier battery in the market.
Using a battery that works with a wide variety of inverters enables installers to choose inverter partners that work best within their Balance of Systems and opens the installer up to building the most optimized system for their customer.
Flexibility also becomes a priority as customer needs evolve over time. Customers who initially purchased 8 kWh or 16 kWh of storage capacity may double their energy consumption and now require 32 kWh of storage. Not only does the installer need a battery that can integrate seamlessly with the existing batteries, the installer often needs to install those new batteries with limited space to scale. In places like garages or basements, where square-footage is smaller, expanding system size without compromising its footprint can be a challenge.
Luckily, there are low-profile and even stackable batteries. The best strategy would be to start with a battery designed specifically for flexibility to make accommodating future changes much easier.
The market for battery storage will undoubtedly expand over the coming years, particularly as technology progresses and renewable energy’s integration with the electrical grid becomes more complex. And while changes in battery solutions are also imminent, there are a few features that will never go out of style – safety and stability, durability and capability, and flexibility in design and future use. So, when it comes to choosing which battery products to bring into the homes and businesses of customers, future-proof projects by following these simple guidelines.
Wes Kennedy, System Engineering Specialist, Blue Planet Energy