We have updated the Unisim Compact solar simulator and will be uploading the details of the new system at the end of the month.
For existing Unisim Compact solar simulator customers the new enclosure systems are available free of charge and will be dispatched shortly. If we have not already contacted you, please email us and we will arrange an enclosure kit for you.
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." 
"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" 
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.
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.
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.
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.
With the advent of cells with more than four junctions, the basic design of the TS-Space Systems Unisim range reached its sensible limit. To provide for five and more junctions, the N-zone solar simulator was introduced. This is very sophisticated, and can be used to analyse cells with up to twelve junctions with-out the adjustment of any one junction affecting the other.
A simplified version of this simulator is now offered. This is based on our standard, spectrally close-matched simulators, but uses LED boost zones in place of the traditional arc and tungsten lamps, up to 1100nm. These are much more compact than our simulator zones, are extremely stable and perform well within the international standards for spatial uniformity of +/-2%.
The LED banks can be retrospectively installed in existing Unisim solar simulators or included at the point of manufacture. They are computer controlled using dedicated rack-mount power supply units which control the current limit and temperature of the individual LED's to automatically prevent any drift in wavelength. Custom software allows for computer
control of an individual LED as well as groups of LED's with the same wavelength. LED output configurations of the simulator can be saved and recalled.
The software automatically detects the LED units installed at start-up which allows the user to replace individual LED's or even install an alternative wavelength LED with minimal disruption to the control system. Thus any later changes to simulator wavelength requirements can be accommodated with minimal cost and downtime.
Please feel free to contact us for more information and pricing.
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.
 Wilkinson, V. A.; Goodbody, C.; Williams, W. G., "Measurement of multijunction cells under close-match conditions," Photovoltaic Specialists Conference, 1997., Conference Record of the Twenty-Sixth IEEE , vol., no., pp.947,950, 29 Sep-3 Oct 1997 doi: 10.1109/PVSC.1997.654244
 "Solar Cell Calibration and Measurement Techniques" NASA Technical Memorandum 113155 November 1997 IECEC–97534
 Jeffrey H. Warner ; Robert J. Walters ; Scott R. Messenger ; Justin R. Lorentzen ; Geoffrey P. Summers, et al."Measurement and characterization of triple junction solar cells using a close matched multizone solar simulator", Proc. SPIE 5520, Organic Photovoltaics V, 45 (November 3, 2004); doi:10.1117/12.559734; http://dx.doi.org/10.1117/12.559734
 Montgomery, Kyle H.; Wilt, David M.; Howard, Alex; Williams, Bill; Williams, Bill; , "Characterization of a TS-Space quad-source solar simulator," Photovoltaic Specialists Conference (PVSC), 2012 38th IEEE , vol., no., pp.001517-001522, 3-8 June 2012
 Wilkinson, V. A.; Goodbody, C.; Williams, W. G., "Measurement of multijunction cells under close-match conditions," Photovoltaic Specialists Conference, 1997., Conference Record of the Twenty-Sixth IEEE , vol., no., pp.947,950, 29 Sep-3 Oct 1997
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