Dutch heating specialist offers solar-tied thermal battery for domestic hot water


One Solution Holland B.V., a Dutch heating tech specialist, presented its FlexTherm Eco thermal battery at the recent Solar Solutions trade show in Amsterdam.

“The battery is particularly suitable to be combined with a rooftop PV system or a residential photovoltaic-thermal installation,” One Solution Holland Sales Engineer Kaz Collé told pv magazine, noting that very little maintenance is required, as there are no moving parts. “The general advantage of our battery is the small volume and low thermal loss. Moreover, it is environmentally friendly as no toxic materials are used and it's fully recyclable.”

The manufacturer describes the device as a thermal charging station that converts power directly into heat and stores it for the provision of hot water.

“It is is a very efficient appliance with energy label A+,” Collé said, noting that the battery uses an inorganic salt as a phase-change material (PCM). PCMs are able to absorb, store and release large amounts of latent heat over a defined temperature range and have often been used, at the research level, for PV module cooling.

The FlexTherm Eco battery is able in three versions with storage capacities of 3.5 kWh, 7.0 kWh, and 10.5 kWh.

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“The 7.0 kWh device can supply 12.5 liters of hot water per minute,” said Collé.

The smallest battery measures 360 mm x 570 mm x 445 mm and weighs 70 kg. The largest device has dimensions of 360 mm x 570 mm x 880 mm and a weight of 170 kg. All of the products have a minimum working pressure of 1.0 bar and a discharge water temperature ranging from 50 C to 55 C.

One Solution Holland estimates the heat loss per hour between 18.7 W and 30.7 W, depending on the system size. It says the battery has already been used on multiple projects featuring PV.

“The total storage capacity of these projects in the Netherlands is currently 13.65 MW,” Collé said, noting that the company is offering a five-year warranty.

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