Yotta Energy has designed a one-kilowatt-hour battery that mounts underneath a roof-mounted, environmentally-exposed solar module.

Ten years ago, the idea of putting a microinverter or optimizer behind a rooftop solar panel was a bit of a reliability stretch. Today, module-level panel electronics warrants its own acronym and enjoys an 80% percent market share in the U.S. residential solar market.

Yotta Energy believes batteries are headed in the same direction — to module-level micro-storage — and is deploying a 52-pound, 1 kW-hr lithium iron-phosphate battery on the same solar module racking gear that holds the ballast.

CEO Omeed Badkoobeh believes any safety and reliability concerns are rendered moot by the stable battery chemistry and the company’s solutions to thermal issues.

The CEO told pv magazine that its temperature-control methods are “completely solid state.”

There are no active components on “the hot side” — no moving parts, no fans, no pumps, no Peltier coolers, no power usage. On “the cold side,” the firm does use power in its phase-change heat exchange system, a technology used in space applications.

The CEO sees this as a solution for solar-plus-storage “in the urban environment.” The company is rolling out several pilot deployments with strategic partners.

Yotta works with solar developers. “Many solar developers get requests for storage,” but settle for just doing solar now out of inexperience or availability. “We see that shifting,” said the CEO. “Soon it will be automatic to deploy storage.”

Badkoobeh claims Yotta’s system, “allows for the lowest installed costs for adding energy storage to any solar PV system. The ability to remotely design and conserve space opens up opportunities for more solar installers to incorporate energy storage.” The CEO said the Yotta product enables the “ability to install just the right amount of storage and the ability to expand.”

Yotta’s funding has come from grants and $1.5 million in seed funding from undisclosed investors. The CEO is working on follow-on funding to keep the ten-person company moving ahead.

Hasn’t this been done before?

SolPad unstealthed in 2016 with bold claims of a yet-to-be commercialized solid-state battery that was installed, like Yotta, under the module along with a microinverter. Four years later, replete with new CEO Terry Jester, SolPad is still developing the technology and coming to market this year.

Barry Cinnamon, an experienced solar and storage installer at Cinnamon Energy Systems has worked with SolPad. He told pv magazine: “I think the idea has a lot of potential. The physical constraints of finding room for batteries on the sides of houses are very challenging, and getting worse with new codes. So — putting the batteries on the roof avoids that problem completely. Carrying up a bunch of 40-pound batteries is much easier than installing a 220-pound battery on the side of a house. There are also some interesting design issues with either sending DC power down from the roof (to a backup inverter), or actually doing the backup power generation on the roof with micros.”

According to SolPad cofounder, Christopher Estes, the startup “has a very sophisticated energy storage and energy analytics solution that is far superior in all aspects,” which is the kind of thing cofounders say.

SolPad’s current CEO and solar industry veteran, Terry Jester tells pv magazine, “We have a full suite of products including load controller (for demand charge management/reduction), inverter (1 kW), battery storage (2 kW-hr), gateway, junction boxes and all the wiring needed to install a system.”

“We’ve shipped our first load controllers and are excited that we are nearly through UL certification with our product suite (several components such as the battery, junction boxes and the cables are complete), with expected shipments of the inverter storage system in Q2 of 2020. The inverter is GaN based, bi-directional and will delivery almost 10% more energy than products out there now because of low parasitic losses and high inverter performance — even in low power ranges. We can run off-grid with ease and the load controller will manage the battery state of charge/load shedding if off-grid for extended periods of time.”

Another startup with similar ideas, JLM Energy, claimed 20-year warranties for module-level storage, right before it went bankrupt.

Getting through “the arc of acceptance”

Yotta’s CEO cites a large battery design that “took a year to site,” noting that it required fire suppression systems and had to be a certain distance from the building. He added, “Every project for energy storage is a custom-engineered process.” He said that storage is complex and expensive and “people don’t want to take the technical risk.”

He added, “Centralized systems require a lot more human intervention.”

In an interview with pv magazine, John Powers, CEO of software startup Extensible Energy said, “Batteries are great. Utilities are deploying batteries on the grid. But a 20 kw-hr battery in a commercial building is large, complicated and requires fire suppression. The installed cost is many times the cost of the battery itself.”

These seem like decent reasons to go with a lot of small, UL-certified batteries on commercial buildings and residences.

CEO Badkoobeh knows he “must get through the arc of acceptance.” He used that term several times during the interview.

Cinnamon notes, “The challenge for every company with batteries and inverters is getting the requisite UL certifications — and making sure the system works. It’s expensive and time-consuming.”

Another installer told pv magazine, “Real world pricing to the consumer means a lot and we know nothing about where that’s going to be when [Yotta] finally starts to ship in quantity…Enphase, SolarEdge, Pika/Generac…all bringing new storage [to market] and they’ll all go through a painful burn-in period. They all have their work cut out for them. I see the expanding storage space likely to be just as brutal, if not more so, than solar module manufacturing and sales.”