Understand the pros and cons of software and communications decisions

software and communications strategy

At times, it is optimal to have connected devices in place. At other times, it creates another point of failure.

As is true in every industry today, solar installations are becoming smarter and more connected by leveraging the power of real-time data, remote controls and responsiveness to improve project and product performance. Project owners and financing partners cheer software platforms that enable sophisticated communications.

Without question, software and communications can play an important role in many storage projects. First and foremost, battery communication capabilities may be required or at least strongly recommended when integrating with certain inverters, chargers and other power electronics.

At the residential level, such software and communications allow for higher level monitoring capabilities that provide both the installer and homeowner with granular data on system performance and health. Software can also improve ease-of-programming.

When it comes to C&I projects, software and communications plays an even more important role. These large-scale projects often combine large numbers of interconnected technology assets and hardware that require communications and software to communicate with one another and perform as an integrated system.

But be careful…

That said, as important as these technologies are to the future of the renewable energy industry, be sure to proceed with caution.

At times, it is optimal to have connected devices in place. At other times, it creates another point of failure. When an installation’s on-site management is dependent on interconnectivity through networks and airwaves, what happens when those conduits cease to function?

In an environment in which renewable energy + storage deployments have become more and more critical in the face of escalating catastrophic events, it’s important to recognize that software and communications can create barriers to energy resilience when the grid and Internet networks are unavailable. The result is stranded assets that do not have the ability to turn back on without the intervention of a highly trained professional.

After Hurricane Maria in Puerto Rico, for example, homeowners did not have the ability to bring their systems back online, and expert software technicians were unavailable to service offline inverters and energy storage systems for some time. The same issue has posed problems in remote communities, where technical expertise to reset and restore system function has not been available locally. In this kind of situation it often makes sense to have a simpler, user-friendly battery system design.

Be sure to weigh the added cost and complexity of installing a smart storage system. With additional wiring and programming required, installation can be longer and more cumbersome without added benefit.

Unfortunately there is no one-size-fits-all solution when it comes to communications and software. In some cases, connectivity is essential to project success. But in other situations, building resiliency is better achieved through a simpler approach that empowers the end user to own, control, manage and fix their own systems. The key for installers is to understand both and be able to advise their customers as to which is most advantageous for their unique circumstance and project objects.

This post and the entire 12 Days of Storage was contributed by SimpliPhi.

— Solar Builder magazine

Design a battery bank to grow with your customers

modular battery storage design

Whether residential or commercial, energy needs and usage inevitably evolve over time — most often with power loads and required energy increasing as operations or families grow.
With that reality in mind, the ability to deliver energy storage solutions that can scale and expand in sync with an end customer’s needs is an important installation selling point.

Understanding scalability

Battery size and modularity can make a big difference when it comes to project scalability, optimization and ease of installation, but not every battery has the ability to scale. Some are limited to two-to-four in parallel configurations, while other batteries are designed to scale to any desired kWh.

For example, at the Taft Botanical Garden in Ojai, Calif., the property owners realized that their ground mount solar array was generating significantly more energy than anticipated — and more than their initial 21 kWh battery bank could store. At the same time, special events at the garden were taxing the system with high demand. The system installers were able to easily double the size of the battery bank by adding new batteries to the existing bank (blending old and new), harnessing more solar power to the benefit of the property’s operational needs and budget.

Consider kWh optimization and space utilization

Energy storage modularity is also a benefit when it comes to optimizing storage for each unique deployment case and environment. Smaller building blocks allow more flexibility to narrow in on the exact kWh capacity best suited to a project. Modular batteries also allow more freedom when it comes to space utilization, making it possible to install in small, crowded or uniquely configured locations.

At a home in England, for example, the homeowners had only one, tiny “Harry Potter-sized” under-stair closet available to house their battery bank. With small, modular batteries, that installation location proved to be no problem.

Simplify, accelerate your installs

Common battery weights range from 50 lbs to more than 400 lbs. Depending on how much your battery weighs, the installation process will be very different.

Larger batteries require heavy equipment to install and present limitations as to how they can be installed. For example, mounting a 400 lb battery on a wall would be impractical, whereas simple brackets and standard shelving can easily house smaller, lighter weight batteries. You may also find other limitations with larger battery building blocks such as doorway restrictions and stairwell limitations when installing.

When it comes to choosing the right battery for your next storage project, consider solutions that can scale and expand. The added flexibility and simplicity will be appreciated by customers both in the present and years down the road.

This post and the entire 12 Days of Storage was contributed by SimpliPhi.

— Solar Builder magazine

Here’s a crash course in battery system sizing


battery size calculation

Get your calculator ready.

There are various ways to determine the size of a battery bank when designing a system. The most efficient way to size a battery bank is to determine the electrical loads and load requirements for both power and energy. Proper system design involves a number of factors and requires analysis and calculations on the loads, PV or other generation sources, as well as the battery performance profile being used in the system.

Depth of discharge

As discussed a few days ago on the Fourth Day of Storage, depth of discharge plays an important role when sizing batteries because battery banks must be calculated according to the actual amount of usable energy storage. Check your battery’s warranty for the most accurate statement of its depth of discharge. For example:

  • 80% DoD = 3.5 kWh x .8 = 2.8 kWh
  • 90% DoD = 3.5 kWh x .9 = 3.1 kWh
  • 100% DoD = 3.5 kWh x .1 = 3.5 kWh

Sizing based on loads

The most important step when sizing a battery system is to determine the required or desired amount of energy storage — most often using a measure of kWh-per-day. The minimum kWh-per-day value can be calculated based on the wattage and runtime of all potential loads to be supported by the system. From there, the battery size may be adjusted depending on whether the system is intended for daily cycling or backup power. The load profile and desired duration of backup power should also be considered.

There are a number of online resources available to calculate loads and determine the appropriate kWh-per-day value from utility billing information.

Consider this example:

  • 2.8 kWh at 80% DoD
  • Load calculations: 10 kWh per day
  • Customer requests: 1.5 days of backup power
  • 10 kWh x 1.5 days = 15 kWh of desired storage
  • 15 kWh/2.8 kWh (battery size) = 5.3 batteries

In this example, based on the actual usable amount of energy for 5.3 of the batteries selected, you may choose to size up to 6 batteries or round down to 5 batteries based on customer preference, either to create extra cushion for unforeseen electrical loads or to be cost conscious and design a more conservative system.

Sizing based on solar

Simpliphi Governor Brown off grid project

The battery bank at California Governor Jerry Brown’s off-grid residence.

When retrofitting an existing PV installation to add storage, battery bank size is most often computed based on the size of the solar array. It is important to consider peak sun hours, PV Watts data (realistic energy production based on location), and PV size (kW) as part of the calculation. In addition, it’s critical that the system cannot exceed the maximum continuous charge rate of the battery bank to prevent damage and ensure a long life. For example:

  • Battery for system: 3.5 kWh battery with maximum charge of 1.7 kW continuous
  • PV array size: 4 kW
  • Average PV daily production: 20 kWh per day
  • 4 kW (PV) / 1.7 kW (Max. battery charge) = 2.3 batteries

Round up the 2.3 battery units to determine that the minimum number of batteries would be three of the 3.5 kWh batteries.

Based on daily PV production: 20 kWh (PV per day) / 3.1 kWh (battery at 90% DoD) = 6.4 (3.5 kWh batteries)

From this calculation, you can round up to 7 or round down to 6 batteries based on customer preference (such as mode of operation).

Power Requirements

Every battery has a maximum charge and discharge capacity. Those rates must be adhered to for adequately charging the battery, like PV system size (charge rate) and the continuous load value to be supported by the battery (discharge rate).

Consider this example:

  • Battery for system: 3.5 kWh with a maximum continuous discharge of 1.7 kW
  • Home maximum continuous discharge: 6 kW
  • 6 kW (continuous load) / 1.7 kW (battery maximum discharge) = 3.5 batteries

When it comes to power requirements, you always round up to determine the minimum battery bank size. In this example, the system requires 4 of the 3.5 batteries.

For additional guidance, SimpliPhi Power offers a simple battery bank sizing estimator tool right here.

This post and the entire 12 Days of Storage was contributed by SimpliPhi.

— Solar Builder magazine

The value proposition of energy storage without solar

energy storage as a service

It’s no surprise that within the solar community energy storage is most often discussed in the context of solar+storage. But what about the potential for energy storage where there is no PV system?

Whether you’re talking about residential or C&I applications, the truth is that batteries can help optimize any power generation source including solar, wind, grid power, or fuel-based generators by storing reserves and lowering energy costs, creating energy security for home and business owners.

Solar installers know that in a solar+storage system, PV generation is used to charge the batteries during the day for use at night, periods of inclement weather or grid outages. Similarly, wind turbines can be used to charge batteries when the wind is blowing, day or night, for use when wind conditions are unfavorable.

Even in the case of traditional fossil fuel power generation, energy storage can be a game changer.

Storage as a service

Where utility rate structures are based on time of use (TOU), batteries can charge from the grid during off-peak hours and discharge during the highest rate periods — protecting home and business owners from paying more for energy used during those times. This type of grid-tied energy storage opens up opportunities for smarter and less costly energy consumption for residential and commercial customers alike. This is also true for those who rent or lease their property and cannot install solar energy on their roof.

Further, for those home and business owners who want energy security but cannot yet afford a solar or wind power system, the installation of only a few batteries can deliver the energy resiliency they need during an outage as a first step.

For those who rely on fuel-based generators, batteries can save money on fuel and extend the life of the generator by switching it’s role from a source of primary power to a battery charging tool. This allows the generator to be used more effectively at its full capacity to charge the batteries for shorter periods of time, which significantly reduces generator run-time and the associated noise and maintenance costs.

With so many different value propositions for batteries with or without renewable generation, energy storage deployments can provide an exciting new business growth opportunity for solar installers who are looking to diversify their expertise and provide additional benefits to their customers.

This post and the entire 12 Days of Storage was contributed by SimpliPhi.

— Solar Builder magazine

Solar + storage inverter selection: inverter stacking vs. high voltage inverters

commerial solar storage simpliphi project

Scaling an energy storage system requires stacking both energy (batteries) and power (inverters).
Batteries that were designed to be modular can typically be stacked without limitation. However, inverter stacking presents more challenges. The question installers must answer is at what point does it make sense to jump from a multi-inverter stack of 48V inverters to a higher voltage inverter option.

Regardless of the energy storage demand, the power requirement of a project’s load profile is the most important factor when deciding whether inverter stacking or a high voltage inverter option makes sense for a project.

When considering a standard 48V battery-based inverter, stacking is limited to smaller outputs. In fact, most of the largest allowable 48V battery-based inverter stacks cap out at approximately 60 kW. That 60 kW is usually more than enough power to cover residential and even some small commercial systems. For systems larger than 60 kW, making the leap to a high voltage inverter is most often the best choice in order to achieve higher power output and cover larger loads, such as those seen in most commercial and industrial projects.

When deciding whether to stack 48V inverters or choose a higher voltage inverter, be sure to also consider the AC power demands of the project.

48V inverters are ideal for residential projects that consist of 120/240V AC loads, and high voltage inverters are best suited for commercial and industrial projects with 3-Phase 480V AC Power requirements. Choosing a high voltage inverter designed for a greater power output avoids expensive and long installation practices with extra equipment such as transformers and cabling.

Choosing the optimal inverter for the power demands of a given project ensures a less costly installation process and safer, more efficient energy storage system operation for the long term.

This post and the entire 12 Days of Storage was contributed by SimpliPhi.

— Solar Builder magazine