Solar Simulation System with Cloud and Tunnel Simulation

With this solar simulation system developed for Volvo Cars in Gothenburg, BF Engineering implemented a high-performance test platform that enables not only constant solar irradiation but also dynamic transitions between sunlight and shadow. The core of the system is a mechanical shutter technology that enables realistic driving situations such as passing clouds or entering a tunnel to be reproducibly simulated in a climatic wind tunnel. The project was implemented via Aiolos Engineering and is based on 28 BF SUN high-performance luminaires.

The technical challenge lies in the HMI technology used: high-performance HMI luminaires cannot simply be switched on and off arbitrarily during an ongoing test. After being switched off, a cooling phase is initially required before they can be ignited again. For rapid changes in light intensity, the radiation is therefore mechanically interrupted by shutters while the luminaires themselves continue operating in their stable operating state.

The Volvo system uses a specially developed “Tunnel-Cloud” rotary shutter system for this purpose. Mechanical shading elements are selectively moved in front of the individual light sources to reduce or interrupt their radiation. This allows rapid changes in brightness to be generated without affecting the thermal and spectral operating characteristics of the HMI light sources through switching them off and on again. The project specification explicitly identifies the system as “SunSim for CWT 28x4000W with shutter” and the shutter as “Drehshutter Tunnel-Cloud”.

This makes it possible to investigate dynamic driving scenarios under controlled laboratory conditions: a vehicle can initially be thermally loaded under full solar irradiation, then enter a simulated shadow area or tunnel within a short period of time, and subsequently be exposed to full solar radiation again. Changing levels of cloud cover can also be reproduced. Such transient load changes are particularly relevant for the development of modern air conditioning and thermal management systems.

The system achieves a maximum irradiance of 1,200 W/m² on a reference area of 6 × 3 metres. In combination with the cloud simulation system, the irradiance can be reduced to 300 W/m². The required homogeneity is 5%. A total of 28 BF SUN luminaires rated at 4,000 W each are used, corresponding to 112 kW of installed lamp power.

The system was designed for operation under demanding climatic wind tunnel conditions. The solar simulation can be operated at temperatures down to −10°C; the chamber itself is designed for conditions of up to −30°C or +60°C as well as rain and snow simulation. Three pyranometers measure the irradiance and support reproducible system adjustment and monitoring.

By combining high-performance solar simulation with mechanical shutter technology, BF Engineering expands conventional solar testing with a decisive additional dimension: not only the intensity of sunlight, but also rapid and realistic changes in solar loading can be reproduced. This creates a versatile development platform for investigating vehicle behaviour under dynamic environmental conditions.