Solar Cooling Opt - Primary energy optimisation of solar cooling systems with efficient system technology and innovative control strategies

1.10.2010 - 31.12.2013

Funding organisation: Climate and Energy Fund, New Energies 2020, 3rd call for proposals, July 2009

Project leader University of Innsbruck: Wolfgang Streicher

Project staff: Daniel Neyer, Alexander Thür, Markus Brychta

The research project "Primary energy optimisation of solar cooling systems with efficient system technology and innovative control strategies" (SolarCoolingOpt) aimed to optimise the primary energy efficiency of solar thermal cooling systems.

In a first step, improved simulation models for a speed-controlled sorption rotor and an absorption chiller with dynamic behaviour were developed for the TRNSYS simulation environment. One focus of the project was to investigate different system types and configurations with their associated control strategies through simulation with improved models and to contribute to the optimisation of solar thermal cooling systems through specific measures. The following three applications were analysed

a) Desiccant Evaporative Cooling (DEC) systems

b) Absorption chiller in the low output range (19 kW)

c) Absorption chiller in the MW range as base load coverage

In each case, a "standard configuration" and several optimised variants were simulated and examined for their primary energy efficiency and compared with a reference system for conventional refrigeration (compression refrigeration system). For DEC systems, the importance of the sorption rotor for moisture recovery in heating mode was emphasised. For the 19 kW absorption refrigeration system, dynamic capacity control and the omission of a cold water storage tank and thermal back-up led to very good efficiency values. With an ideal design and relatively simple control concepts, large systems (>1000 kW) that cover the base load can achieve savings in non-renewable primary energy of >50% compared to the reference system. Solar-assisted systems of this size and configuration can achieve at least an electrical "Seasonal Performance Factor" _SPFel of > 12.

The optimisations developed were implemented and successfully tested for selected systems.

Life cycle analyses for two of the uses investigated by simulation showed that when considering the entire life cycle, solar thermal cooling systems (with optimised operation) can compensate for the higher expenses for construction and disposal and have a reduction potential of greenhouse gas emissions and non-renewable primary energy demand in cooling operation of between 35% and 50% compared to conventional systems in the case studies investigated here.

Investigations of two case studies with absorption chillers in the industrial and commercial sector, including economic feasibility studies, resulted in minimum amortisation periods of 8 years, depending on the location and other boundary conditions. The utilisation of existing waste heat flows (not otherwise required) as a cooling process drive represents an interesting option here.

Practical tests with a functional model of an efficient and cost-effective recooling unit (26 kW recooling capacity) developed in the project showed ways of significantly reducing investment and operating costs.