On the work­bench in a Swiss garage lie an engine cooling system, a self-bent composite pipe heat exchanger, the hoses of an antifreeze circuit—and an ebm-papst fan. A water tank stands on the floor. Cable ties, tools and an old brine heat pump complete the makeshift setup. Thomas Degelo, Michael Egli and Pascal Barmet sit around it, tinkering, discussing and forging a plan. “We asked ourselves why there was no system that provided renew­able heating without going deep into the ground or installing a lot of tech­nology outside. That’s how the idea of imple­menting the prin­ciple of an ice storage heat pump on a small scale came about,” says Thomas Degelo.

From a Garage Start-Up to a Full-Fledged Company

Tradi­tional ice storage heat pumps are suit­able for large build­ings: hotels, office complexes, or commer­cial build­ings. This is because they use large, under­ground concrete tanks that hold several thou­sand liters of water. Heat exchangers are located inside these tanks, through which heat from renew­able energy sources is fed into the system. When heat energy is extracted from the storage tank, the temper­a­ture drops to 0° Celsius; the water freezes, releasing energy that is used for heating. When heat is rein­tro­duced, the ice melts again, and the cycle begins anew. Ice storage heat pumps are designed for seasonal storage manage­ment: heat is stored in the summer and retrieved in the winter.

The heat transfer fluid flows through the heat exchanger coils and absorbs energy from the ice storage tank. (Images | Nullpunkt AG)

For a single-family home, a typical system like this is too large, too expen­sive, and far too complex. But conven­tional heat pumps also have their limi­ta­tions: ground-source heat exchangers require permits, involve exten­sive construc­tion work, and are costly. Outdoor air-to-water heat pumps take up space, require careful noise and site plan­ning, and are not to everyone’s aesthetic taste. “As the three engi­neers and home­owners that we are, we weren’t willing to accept that,” says Degelo. “We asked ourselves why there wasn’t a system that provides renew­able heating without going deep into the ground or installing a lot of equip­ment outside.” That’s how the idea arose to develop an ice storage heating system that could also fit in a garage, a base­ment room, or a niche.

In the winter of 2023, the three engi­neers installed the first proto­type of a compact ice storage heat pump at a colleague’s house. The oil heating system remained connected as a backup, just in case. But the impro­vised setup consisting of car radi­a­tors, composite pipes, antifreeze solu­tion and an old fan worked—and was surpris­ingly stable at that.

The successful exper­i­ment marked the starting point: Devel­op­ment of the ice storage heat pump began in 2023, and in 2025 the engi­neers founded nullpunkt AG—with the goal of devel­oping a marketable ice storage heat pump for single-family homes.

Winter in summer?

But then winter was over—and with it, the real-world condi­tions needed for a true stress test. The three engi­neers didn’t want to wait for the next one. So they simply recre­ated it: In a rented under­ground parking garage, they set up their own climate lab—complete with a cooling system, humid­i­fi­ca­tion, and a control system capable of gener­ating frost and fog profiles at the push of a button. “We were able to bring the chamber down to minus 15 degrees Celsius and 90 percent humidity,” says Degelo. “This allowed us to specif­i­cally test situ­a­tions that rarely occur together outdoors—and certainly not when you need them.” A year later, Nullpunkt installed the further-devel­oped proto­type at their colleague’s facility again. It was an excep­tion­ally cold winter with plenty of freezing rain—the perfect endurance test. Based on these tests, Nullpunkt made final adjust­ments. The start of series produc­tion was now within reach, but one crucial compo­nent was still missing.

At night, Triton is barely audible compared to other heat pumps on the market—we owe this largely to this fan.

Thomas Degelo, CEO Nullpunkt AG

The very first proto­type ran on an old ebm-papst fan that was orig­i­nally intended for another project by Degelo’s engi­neering firm. Its purpose was to convey the ambient air through the external heat exchanger and thus regen­erate the ice storage tank. “I was already familiar with ebm-papst from my time in building services engi­neering, so I know how effi­cient their prod­ucts are,” says Degelo.

The AxiTone is unbeat­ably quiet

As devel­op­ment progressed and the team needed a new, more effi­cient and signif­i­cantly quieter fan, nullpunkt contacted ebm-papst in Switzer­land. Samuel Schlit­tler, sales repre­sen­ta­tive at ebm-papst in Switzer­land, quickly came up with the right sugges­tion: the AxiTone, an axial fan specially devel­oped for heat pumps with partic­u­larly quiet oper­a­tion.

“The 450 mm AxiTone fits into the Triton concept without any major adjust­ments. It delivers the neces­sary airflow while remaining highly efficient—and, above all, quiet,” explains Schlit­tler. During the day, the noise level is around 53 dB(A), and at night it drops to as low as 35 dB(A). In conven­tional heat pumps, the air usually flows in from the side. In Triton, the AxiTone is located on top of the outdoor unit and pushes the air down through the ring-shaped heat exchanger. This air flow ensures an even flow through the heat exchanger and contributes signif­i­cantly to the low noise level. “The AxiTone offers enor­mous advan­tages for us,” says Degelo. “At night, Triton is barely audible compared to other heat pumps on the market—we owe this largely to this fan.”

In addi­tion, the flow tech­nology experts at ebm-papst in Mulfingen contributed their exper­tise to the further devel­op­ment: Together, the part­ners opti­mized the entire air flow, adjusted the baffles, refined the heat exchanger geom­etry and coor­di­nated the flow paths with each other. The result is an outdoor unit with partic­u­larly quiet running char­ac­ter­is­tics and high effi­ciency.

A start-up that is rethinking heating

The Triton system has been on the market since October 2025 and the first systems have already been installed. At the same time, the company is already plan­ning the next step: The heat pump will also be launched on the German market. Although Triton does not require any addi­tional heat sources, nullpunkt is plan­ning exten­sions such as the inte­gra­tion of photo­voltaics or waste water heat in order to further increase effi­ciency and the use of self-gener­ated elec­tricity.