document title / titre du document TRP W ORK PLAN ... - emits - ESA

TRP Work Plan 2005-2007
Description of Activities
TEC-SB/7935/dc
12/Feb/09
TRP Reference: 03/W25
Title:
Solar cell electrical characterization facility for Mars exploration missions
The differences between the Mars environment and the orbital environment in which the solar cells are most commonly used
require dedicated facilities to test both the solar cell and the photovoltaic assembly Coupons.
The critical differences between the two environments having strong impacts in the solar cell and photovoltaic assembly
testing are:
- Solar intensity and spectrum modified by dust
- Low temperature operation
- Dust deposition on the solar array surface
The Mars surface is characterized by low temperature, low solar intensity and by a solar spectrum which is strongly affected
by the atmosphere. The sunlight reaching Mars is strongly scattered by the dust particles hanging in the air; for this reason the
diffused component is larger than the direct light. The direct part of the spectrum, incident on the Mars surface is more intense
in the blue region whereas the diffuse part is more red due to the blue light absorption. Being the opacity of the atmosphere
defined as the optical depth, the total spectrum is redder when the optical depth increases. It can be roughly assumed that the
solar cells will work on Mars at an average temperature between -80oC and +20oC with a solar constant between 0.2 and 0.4.
These conditions are however changing over the course of one day and depend on the seasons and atmospheric
phenomena.
The atmospheric dust does not remain suspended in the atmosphere, but deposits out of the atmosphere onto any horizontal
surfaces with a dust coverage rate of 0.3 % power loss per day. This is potentially the major lifetime limiting factor for a solar
power system on any Mars mission longer than 100 days.
For these reasons it is very important to upgrade and to modify the existing test facilities dedicated to the characterization and
the qualification of the photovoltaic components, in order to be prepared for the future Aurora missions on the surface of Mars.
To achieve the above described objectives, a first activity is proposed. The consideration / simulation of Martian dust
deposition effects on the solar array surface will be addressed in another new Aurora technology activity entitled Martian Dust
Simulation Facility for Solar Cells . The main technical objective is the realisation of a solar cell electrical characterization
facility adequate to the specific Mars environment requirements by modifying and upgrading the already existing INTA facilities
at SPASOLAB.
These facilities will be adapted to the electrical characterization of both Silicon and Gallium Arsenide based solar cells.
The following development steps are proposed as follows:
- Modification/Upgrading of the optical system of Spasolab multi-zone solar simulator, dedicated to the multi-junction GaAs
solar cells, by means of the realisation of a dedicated filter able to meet the requirements of the Mars surface illumination
spectrum
- Modification/Upgrading of the optical system of Spasolab single source solar simulator, dedicated to the Silicon solar cells,
by means of the realisation of a dedicated filter able to meet the requirements of the Mars surface illumination spectrum
- Modification/Upgrading of the Cryostat dedicated to the electrical characterization of the solar cells at low temperatures, in
order to be suitable for the existing larger solar cells.
Deliverables:
Assessment/realisation of a solar cell electrical characterization facility (by modifying/upgrading the optical system of Spasolab
).
Current TRL: TRL1 Target TRL: TRL4 Application Need/Date: TRL4 in 2008
Application/Mission: Mars Exploration Contract Duration: 18 months
SW Clause : - Dossier0 Ref.: T-7720
Consistency with Harmonisation
Roadmap and Conclusions:
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