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ResoFreeze: Innovative plant concept for supplying cooling with CHCP

EnEff:Wärme - Forschung für energieeffiziente Wärme- und Kältenetze
Ansicht einer 80 kW-Resorptionsanlage, die in ähnlicher Form im

View of an 80-kW resorption chiller that is being constructed in a similar form as part of the research project.

© Makatec GmbH

Settlement summary

Project status Projektstatus: Phase 2Planning
Location TU Dresden, 01069 Dresden, Germany
Project plan Commissioning of the plant, development of calculation models for simulating the process, validation of the simulation using measurement data from the plant
Developer, organizer TU Dresden, Makatec GmbH
Project themes

Project description

To further increase the operating times of CHP plants, the waste heat produced from the electricity generation can also be used in summer to provide cooling in a temperature range below 0 °C. A new kind of plant for combined heating, cooling and power (CHCP) shall be thermodynamically optimised for this purpose and the economic potential of the plant concept verified by constructing and testing a prototype system. The core of the development is a resorption chiller that in combination with an ice storage system makes it possible to decouple the peak electricity and cooling requirements time-wise. This opens up new opportunities for increasing the efficiency and profitability of the overall supply system.

In all scenarios for converting to a renewables-based energy provision, the use of highly efficient cogeneration belongs to the recognised transitional technologies. Therefore it is important that much greater use is also made of the potential offered by trigeneration (CHCP) for providing cooling, such as for storage purposes in the food industry and in industrial and technological processes, i.e. in the –5 to +4 °C temperature range. 

Project

The increasing requirement for cooling in private households and industry needs to be met by suitable concepts. Vapour-compression chillers, which require a considerable amount of electrical energy, can be replaced by utilising absorption processes and the available waste heat potential. In particular the focus is on waste heat in the temperature range between 70 and 90 °C, since this is created in a diverse range of technical applications and is difficult to use for other technologies such as in simple clockwise processes. This waste heat could be produced, for example, by solar thermal systems or CHP plants in summer, since the heating requirement during these months is low. The CHP plants could be operated at full load, which would increase the electricity efficiency and revenues.

In order to utilise these advantages, a new kind of resorption chiller has been developed with a water/ammonia mixture. The intention is to operate it as a demonstration system. In order to ensure that the generation of the electrical and cooling energy is decoupled, particularly during peak load periods, the generated cooling energy is stored in an ice storage system. Calculation models are being developed and validated for this plant concept. 

Schedule
  • Installation and commissioning of the resorption chiller at the site in Dresden by December 2013.
  • Testing and recording the performance data for the system until around June 2014.
  • Optimisation of the chiller operation and validation of the simulation codes by the beginning of 2015.

A chiller will be constructed as a demonstration system in a commercial environment as part of a second project phase from 2015.

Concept

The project intends to prove that, in comparison with conventional cogeneration plants, the concept of CHCP plants improves the economic efficiency. That can be particularly expected where cooling requirements exist throughout the year. In addition, the research project also intends to investigate the savings potential achieved by using compact plastic heat exchangers. These have a high resistance to caustic materials such as ammonia and have considerably lower material-specific costs relative to steels with high corrosion resistance. A further focus is on investigating the partial load behaviour of the resorption chiller, including with high external temperatures in summer.