Dutch startup Moonwatt has presented new sodium-ion storage system for use in utility-scale PV plants at the Smarter E trade show in Munich, Germany, today.

“Instead of relying on large, containerised systems, Moonwatt develops small, modular enclosures that are easier to mass-produce, install, maintain and replace,” a company’s spokesperson told pv magazine. “Moonwatt’s smaller battery storage units are distributed across the entire ground-mounted PV array. This is possible because the batteries are cooled entirely passively.”

The system is available in DC- and AC-coupled versions.

The Monopod 1500 V / 4-hour Hybrid system features a DC-coupled architecture that reportedly reduces electrical balance-of-plant costs by 50%. It uses a modular design and offers a stated lifetime of 12,000 cycles. The manufacturer claims its DC-coupled interface to the PV system eliminates multiple conversion losses while achieving 94% efficiency from solar to battery to grid.

Each inverter block provides 350 kVA of AC apparent power, 350 kW of bidirectional AC active power, and operates at 800 V AC. The system supports a maximum PV input power of 600 kW, with a DC voltage range of 500 V to 1,100 V. It also integrates 12 maximum power point trackers (MPPTs), each with five strings.

The configuration accommodates between one and seven Monopod units per inverter block. This scalability enables battery AC power to range from 50 kW to 354 kW, while AC energy capacity scales from 202 kWh to 1,416 kWh.

The Monopod 1500 V / 4-hour Hybrid AC-coupled variant is claimed to cut electrical balance-of-plant by connecting to 800 V inverters on the low-voltage AC side, which the manufacturer said avoids installing additional transformers for the battery system alone. This configuration reportedly a 93% efficiency from solar to battery to grid.

With this product, each inverter block provides same AC apparent power, bi-directional AC active power, an AC voltage as the DC-coupled system. While there is no solar max input power specified for this configuration, it features a battery maximum DC voltage of 1500 V DC.

The system accommodates scalable storage setups, integrating from 1 up to 7 Moonpod units per inverter block. Depending on the number of units, the battery max power AC scales seamlessly from 50 kW to 354 kW. Concurrently, the total battery energy capacity AC expands from 202 kWh up to a maximum of 1,416 kWh.

Both products are IP68-rated for the Moonpod unit and IP65-rated for the inverter. The inverter measures 1,050 mm x 950 mm x 380 mm and has a weight of 150 kg. As for the Moonpod units their dimensions are 1,213 mm x 1,053 mm x 2,114 mm and weigh 3,500 kg.

For the battery technology, Moonwatt uses sodium iron phosphate pyrophosphate(NFPP) cells, a polyanion sodium-ion architecture prized for exceptional thermal stability and complete absence of lithium, cobalt, nickel, or manganese.

As for the passive cooling architecture, Moonwatt claims it delivers a measurable efficiency advantage, as it loses up to 25% less energy per cycle than a conventional actively cooled lithium-ion system, where fans, pumps and HVAC equipment consume auxiliary power continuously. Moreover, the Moonpod units draw zero auxiliary power for cooling thermal management and run silently thanks to the complete absence of active cooling, according to the manufacturer.

“We want to replicate the success that small solar string inverters had over large centralised inverters,” the spokesperson said. “The solar industry proved that distributed, modular power electronics outperform large central units in reliability, serviceability, and ultimately cost. We believe the same transition is now coming for battery storage.”

Weighing under 3.5 tons, each Moonpod unit can be handled with a standard forklift, with no crane required, and placed directly on flattened soil or gravel with no concrete foundations needed. The same product suits retrofits of existing solar plants, connecting on the low-voltage DC or AC side without redesigning the plant’s electrical architecture or adding medium-voltage infrastructure.

The company is present at Intersolar Europe in Munich from 25 to 27 June (Booth C2.190), where the Moonpod will be on display.