Renewables: What’s Next in Energy Storage Systems?

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While more than a billion people on the planet do not have access to a power grid, we are witnessing a growing pervasiveness of small solar systems in which a solar panel and a battery are connected to constitute a system along with an electrical outlet, either a USB port or an AC adapter. These pay-as-you-go solar systems are growing in popularity in Africa and some parts of Asia, where people can access electricity for about $6 to $8 a month.

This allows fishermen to freeze what they catch and get it to the market safely. People are also able to have light bulbs, TVs, and mobile phone chargers in their homes. Alex Lidow, power semiconductors industry veteran and CEO and co-founder of Efficient Power Conversion (EPC), called this a quiet trend when he spoke on a panel during the Green Engineering Summit held virtually last week. He said that many startups, as well as large companies, are now operating in this field.

The panel discussion, “Alternative energy sources and related energy storage technologies,” aimed to determine the megatrends in renewable industries.

Another panelist, Shri Joshi, head of the Industrial Power Control (IPC) division for the Americas at Infineon Technologies, presented an interesting statistic. Of all the cumulative capacity on the solar grid in the United States, only 6% have the battery or storage attached. “It shows an immense potential for storage to grow,” he said. “It also shows that storage will come in various forms, not just stationary batteries.”

Joshi added that the overall picture is quite diversified at the macro level. “In the United States, we have a lot of emphasis on grid-scale storage before the meter,” he said. “In Germany, there is a lot of emphasis on behind-the-meter, and that drives different topologies and component requirements.”

Figure 1: In before-the-meter cases, an energy storage system (ESS) functions as bulk storage coupled with either renewable generation or transmission and distribution systems. In residential and commercial setups, ESS plays a role as behind-the-meter. (Source: Infineon Technologies)

With the advent of wide-bandgap (WBG) semiconductors, Joshi said, there is a shift towards high-frequency conversion. That will greatly impact the passives and will also mandate new requirements for thermal management. “Components with better thermal conductivity can squeeze higher power from a given circuit size,” he said.

Like Lidow, Joshi sees that solar and storage are getting combined, which means battery voltages will go as high as 1,500 V. That, in turn, calls for WBG technologies like silicon carbide. Here, as Joshi noticed, there is a propensity for going towards high-frequency switching. “There is a need for creatively integrated modules with low self-inductance because that matters for surge voltages,” he said. “It was unheard of five to 10 years ago.”

Three megatrends in ESS

When asked about megatrends in energy storage system (ESS) technologies, Henrik Mannesson, general manager for grid infrastructure at Texas Instruments, identified three areas.

First, while there is a need to generate more energy, the majority of which is now produced by solar and wind, power conversion has become an important consideration in ESS solutions.

Second, for energy storage solutions in households, increasing round-trip efficiencies, heat management, higher power density, and the overall size of energy storage systems have become major design considerations.

Third, on the battery side of things, Mannesson, like Infineon’s Joshi, sees a clear transition towards higher voltages. “While portable ESS solutions have been operating at 48-V systems on solar power, many ESS solutions now connected to the grid are moving to 400-V battery technologies,” Mannesson said.

Figure 2: Energy storage systems are increasingly connected to grids, and that calls for greater connectivity between generation, distribution, and consumption. (Source: Texas Instruments)

Patrick Le Fèvre, chief marketing and communications officer at Powerbox, presented the European viewpoint about ESS technologies. He told the panel that wind turbines were shut down in some European countries because power could not be distributed to the network due to energy access. Additionally, he said that, due to the lack of wind in countries like Germany and the UK, how we can optimally store energy is still an open question.

Le Fèvre noted that ESS technology is still a big question mark. “We are currently at the development phase, so more research is required for mass energy storage.”

The panel agreed on the need to intensify the research on ESS technologies. However, EPC’s Lidow concluded the discussion on the future of ESS solutions with a more provocative note.

He raised this question: While electric vehicles are taking off, what will we do with all those batteries? First, how do we build them? Do they outlast the mechanical shell around them? Or does a car require a replacement before the battery wears out? “The recycling of batteries may be an important element in the storage of electricity from renewables,” Lidow said.

Think of all those batteries piled up and hooked to the grid — that would be a good thing for energy storage systems.

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