Large Collector Areas Perform Best
Well-sized systems have a collector size of about 4 to 5 m²/kW reference chilling capacity and a hot storage volume of 50 to 75l/m² aperture area. In these ranges high total solar fractions can be obtained and the system operates close to the optimum in terms of primary energy savings and the costs of these primary energy savings.
Implement Optimized Control Algorithm
The control strategy influences the performance of the system considerable in terms of both solar fractions and primary energy consumption. That is: an individual adaptation of the system control to the chiller as a function of location, application and configuration offers significant potential for improvement. Especially the control of pumps and the heat rejection fan must be studied.
Use Chilled Ceiling Distribution Systems
Chilled ceiling systems are more favorable compared to fan coil systems in terms of chiller performance due to a higher temperature level in the chilled water circuit.
Consider Solar Autonomous System for Cooling
To maximize primary energy savings it should always be considered to design a system without fossil backup heater for cooling in summer. If a system is designed large enough, solar fractions for cooling can be above 90% and using the backup system for cooling can be avoided. Other options to reduce fossil fuel consumption are to install a biomass boiler or to use waste heat as heat backup system or an electrically driven compression chiller as cold backup. This will increase primary energy savings but also increase investment costs.