The NEKKA project aimed to develop an alternative vehicle climate‑control system based on the elastocaloric effect. The system uses a nickel‑titanium shape‑memory alloy (FGL material) that changes phase under mechanical stress, releasing or absorbing latent heat. By cycling the alloy between austenite and martensite, the system can cool or heat the cabin without conventional refrigerants, eliminating flammable or high‑GWP substances. The elastocaloric cycle consists of four stages: loading the alloy, heat exchange while maintaining strain, rapid unloading to absorb heat, and a final heat exchange at constant strain. This solid‑state approach can achieve a coefficient of performance (COP) two to three times higher than conventional compression‑cycle air conditioners, as shown in laboratory tests. The absence of a refrigerant loop also removes the risk of leaks that contribute to global warming.

The project progressed through a staged development plan. First, the alloy composition and processing route were optimized to ensure corrosion resistance, long‑term stability, and high elastocaloric response. Mechanical and functional characterisation, including life‑cycle testing under high‑cycle loading, confirmed the material’s durability. Next, the alloy was integrated into a hub element that serves as the core of a component demonstrator. Mechanical testing of the hub element verified that the structure could withstand the required stresses while maintaining efficient heat transfer. The component demonstrator was then mounted in a vehicle‑scale test rig that simulated realistic operating conditions. Finally, the complete system was installed in a prototype vehicle, where it was evaluated for space, weight, and cost savings compared to a conventional air‑conditioning unit. The demonstrator achieved a 30 % reduction in system volume, a 20 % weight saving, and a 25 % cost reduction, while delivering the projected COP improvement.

The NEKKA effort was carried out by a consortium of four partners. Vitesco Technologies coordinated the project and provided the vehicle integration and system‑level testing facilities. TLK‑Thermo GmbH supplied the high‑temperature test benches and the vehicle‑environment simulation rig. The University of Saarland conducted the mechanical and functional testing of the hub element and performed the elastocaloric characterisation of the alloy. Ingpuls GmbH was responsible for the alloy development, processing, and life‑cycle testing. The project ran over a multi‑year period and was funded under the German Federal Ministry of Education and Research’s “New Vehicle and System Technologies” program, specifically targeting lightweight concepts for road vehicles. The collaboration enabled a rapid translation of laboratory findings into a vehicle‑ready prototype, demonstrating the feasibility of elastocaloric climate control for all vehicle classes.

The NEKKA project therefore delivers a scalable, environmentally friendly alternative to conventional vehicle air conditioning. By harnessing the elastocaloric effect, it offers significant gains in energy efficiency, eliminates hazardous refrigerants, and reduces system size, weight, and cost, thereby supporting the automotive industry’s shift toward sustainable mobility.