The project undertaken by Hypnetic GmbH focused on the development of a hydropneumatic energy storage system and the concurrent growth of the company as a manufacturer and marketer of this technology. The technical work began with the construction and testing of a prototype that demonstrated that a conventional hydraulic motor can be repurposed for electrical energy storage. The prototype also proved that adjusting the displacement of the hydraulic motor provides a viable method for regulating power output. Building on this, a high‑pressure low‑pressure concept was devised and experimentally validated, addressing the scaling limitations inherent in the single‑displacement approach and enabling larger storage capacities without compromising control precision.
A key outcome of the research was the design of a management system that guarantees safe and efficient operation of the hydropneumatic storage unit. Modern control and maintenance strategies were integrated into this system. In particular, a model‑predictive control (MPC) scheme was implemented and compared with a conventional proportional‑integral (PI) controller. For a demanded power of 12 kW and a sampling interval of 10 ms, the MPC achieved superior performance, reducing tracking error and improving response time relative to the PI baseline. These results confirm that predictive control can enhance the dynamic behaviour of the storage device.
Parallel to the control advances, the project explored predictive maintenance. Several approaches were developed and validated, demonstrating that condition‑based monitoring can anticipate component degradation and schedule maintenance before failures occur. This proactive maintenance strategy is expected to increase the reliability and lifespan of the storage system, thereby reducing operational costs.
The project also made significant strides in the business domain. The company completed its business‑administration and organisational setup, launched marketing and sales initiatives, and secured a seed‑financing round that bridged the funding gap between the EXIST founder stipend and subsequent investment. Six students were recruited to support development and application studies, and their master’s and bachelor’s theses were carried out in cooperation with the Institute for Electrical Energy Systems – Department Energy Storage. These academic collaborations enriched the technical portfolio and fostered knowledge transfer between academia and industry.
The funding for the project was provided by the German Federal Environment Foundation (Deutsche Bundesstiftung Umwelt). Over the course of the funding period, the project achieved several milestones: prototype construction and testing, development of the high‑pressure low‑pressure concept, implementation of MPC and predictive maintenance, establishment of a management system, and successful seed financing. The combined technical and organisational progress positions Hypnetic GmbH to enter the market with a competitive hydropneumatic energy storage solution that complements existing storage technologies and supports the transition to a renewable‑energy‑based grid.