With our solar simulators and other products being used across the world we aim to provide fast and effective product support. To help in this, we have now added a support forum to our website where we intend to build a repository of information that can provide further support, answer questions if you are having problems or even help you out if you have inherited an old TS-Space Systems solar simulator or product. We have also included forums for our test services and we have already started an FAQ for our outgassing test services.

If you have a question or information you'd like to see included in an FAQ, post it in the relevant section and we'll add it in.

The ASTM standard for solar simulators states that:

"A solar simulator (also artificial sun) is a device that provides illumination approximating natural sunlight. The purpose of the solar simulator is to provide a controllable indoor test facility under laboratory conditions, used for the testing of solar cells, sun screen, plastics, and other materials and devices." [1]

and that:

"A solar simulator usually consists of three major components: (1) light source(s) and associated power supply; (2) any optics and filters required to modify the output beam to meet the classification requirements" [1]

Thus we need to select a light source that approximates the solar spectrum we want to simulate, be it AM0 for space applications of AM1.5 for terrestrial, and appropriate power supply. We also need to be able to manipulate the beam via an optical system such that the spectrum and spatial uniformity of irradiance can be optimised for the required application.

Light Sources
There are four commonly used light sources used in solar simulators:

Light Emitting Diodes (LED) - Recent advances in LED technology for the general domestic market has made high-power LED's commonly available. The advantages for solar simulators are obvious as they have a lower energy consumption and longer lifetime than arc lamps. There are limitations, however. They are only available in discrete wavelengths i.e. a continuous spectrum requires a cluster of LED's operating at different wavelengths which produces a crude spectral match. More importantly, the commonly available wavelength LED's do not cover the full spectrum required for more advanced, multi-junction devices which have a spectral response past 1000nm.

For more information on this see our previous article on close spectral match solar simulators or our new LED-hybrid solar simulator.

Power Supplies
These are typically dictated by the light source used. For example, arc lamp power supplies are typically highly complex devices that have to manage a high voltage ignition stage in order to establish the arc. QTH lamps will require a comparatively more simple DC source with a compatible power output.

Optics
The optical layout of a solar simulator varies greatly depending on a multitude of variables including: the type and number of light sources used, the area of illumination generated, the spectral output generated etc. For basic solar simulators there are perhaps greater areas of commonality between manufacturers: a parabolic reflector, mixing mirror, IR clipping filter and 90 degree "down" mirror are generally found in single source xenon Class "A" systems.

Generally, major concerns for the optical system of a solar system (beyond achieving its required classification) is the ease of use/adjustment and maintenance. If a specific vertical or horizontal beam orientation is required then this should also be considered.

[1] ASTM E927 Standard Specification for Solar Simulation for Terrestrial Photovoltaic Testing

While most basic solar simulators use a single xenon lamp as their light source, advanced solar simulators commonly use multiple light sources (referred to as 'multi-source') in order to achieve a close spectral match to the reference spectrum. This is generally done by filtering and merging the output of two types of source, usually an arc source (metal halide or xenon) for the visible and a QTH source for the NIR-LWIR ranges.

The term 'close-match' to describe a solar simulator that attempted to move beyond a single-source design and accurately reproduce the solar reference spectrum was first used in 1997 by Dr Williams from 'TS-Space Systems LTD' when the results from the first ever close-match solar simulator were presented. The research compared the results of testing multi-junction solar cells using a close-match spectrum to the results from using another, basic solar simulator and showed measurement variations of up to 20% in some cases.