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CoLTES - Latent Thermal Energy Storage for Cooling Applications


Für den Inhalt der Angaben zeichnet die Projektleitung verantwortlich.


This project, funded by Gebert Rüf Stiftung, is supported by the following project partners: Hochschule Luzern, Institute of Mechanical Engineering and Energy Technology, Competence Centre Thermal Energy Storage; Cowa Thermal Solutions AG


  • Projekt-Nr: GRS-046/18 
  • Förderbeitrag: CHF 148'000 
  • Bewilligung: 02.07.2018 
  • Dauer: 09.2018 - 01.2020 
  • Handlungsfeld:  First Ventures, seit 2018



Efficient production of cold is a topic of increased attention since the worldwide cooling demand is increasing. To increase efficiency as well as the ability of integration of renewables, storage technologies are necessary. Cold storages allow for a decoupling of supply and demand and enable to produce cold when it is most efficient. However, current storage solutions have low energy densities resulting in large space requirements and hence high costs. Within the project 'ColTES', a latent thermal energy storage device for cooling applications will be developed which uses a liquid/solid phase change of the storage material to store thermal energy. The technology offers an up to factor four higher energy density than existing water storage solutions. The proposed storage is based on phase change material capsules, arranged in a packed bed, which leads to a high scalability, modularity and flexibility. With the new funds, a prototype of the system will be developed and tested. The described business case will be further specified, related business opportunities will be identified and industrial partnerships will be formed.

Was ist das Besondere an diesem Projekt?

The proposed storage solution is compact, scalable, simple and modular and allows for the production of cold when it is most efficient (e.g. during night) and provide it when needed. Consequently, considerable energy and costs savings results for the end user.


Within the project, a eutectic mixture of two salt-hydrates with a melting temperature of 15°C was developed, which offers a factor four higher energy density than conventional storage materials. The mixture is stable over more than 300 cycles (status: August 2019), cost-effective and environmental friendly. The proof of concept with single metallic and polyethylene capsules could be achieved and an 80l storage filled with around 2000 capsuled will be commissioned in autumn 2019. A cold storage will be installed in a solar assisted cooling system in early 2020 within a demonstrator project with industrial several partners.
Jörg Worlitschek, Simon Maranda and Remo Waser founded the startup Cowa Thermal Solutions with the mission to commercialize the developed technology. Cowa has won the “Zentralschweizer Business Plan Contest” and has reached Venture Kick Stage II. The startup is currently looking for funding/investors and plans to launch their first product in 2021.


M. Berger and R. Waser, «Advanced latent thermal energy storage for space cooling in the tropics», IEEE PES GTD Asia 2019, 2019;
R. Waser et al., «Fast and experimentally validated model of a latent thermal energy storage device for system level simulations», Appl. Energy, vol. 231, pp. 116–126, 2018;
Ghani, Faisal; Waser, Remo; O'Donovan, Tadhg; Schütz, Philipp; Zaglio, Maurizio & Worlitschek, Jörg (10.02.2018). «Non-linear system identification of a latent heat thermal energy storage system». Applied Thermal Engineering, 585-593.



Am Projekt beteiligte Personen

Remo Waser, Hochschule Luzern
Simon Maranda, Hochschule Luzern
Jörg Worlitschek, Hochschule Luzern
Lukas Müller, Hochschule Luzern

Letzte Aktualisierung dieser Projektdarstellung  21.04.2022