A PV cell is the basic unit of a PV array. It is usually made of a silicon substrate coated with a thin film. These are mounted together with supporting structure to form PV panel. A number of technologies are available, but costs vary widely and increase sharply with high efficiencies.
Thin film technologies are generally less expensive than the others, as well as being lighter. Some versions have reached 23% efficiency
Single junction gallium arsenide are up to 28% efficiency.
Multijunction cells, three and four junction cells have reached about 36% efficiency without concentrators and up to 46% with concentrators.
Crystalline silicon cells, 25-26 %, 22% for commercially available products (2019).
Emerging technologies: Perovskite cells may reach over 30% efficiency for very low costs. Still in development.
Multijunction cells can be over 100 times more expensive than less efficient crystalline silicon cells or thin film cells.
Use on Mars
Roll out films
Flexible solar cells can be attached to a flexible backing and packed into large rolls. These can be unrolled directly onto the martian surface for a very simple deployment method. Flexible film cells are less efficient and the variations in the sun's angle during the days reduce the available energy. This might be the best technology for automated deployment in the early stages of the settlement. An example are the Renovagen rapid roll products
Sun tracking panels
Sun tracking can increase the input energy over a year by up to 40% for the same installed capacity. However the tracking mechanisms can be heavy and are moving parts that can fail over time. Might best be used after crews have arrived and there are maintenance facilities set up. Sun tracking may be less useful during dusty seasons, when a large part of the incident light is diffuse light.
Back-up power for rovers
Rovers can be partly covered with solar cells for emergency back-up power. This is a feature of the NASA MMSEV design. Alternatively, rovers can carry fold out or roll out solar arrays for emergency charging.
Solar panels and batteries can be combined into local charging power stations allowing for operating rovers and other equipment in remote locations. A series of power stations could be built along a long road between two remote locations and provide extended operational range.
Power for landed ships
Ships landing on Mars will require power. Du to the heat or re entry, solar cells on the exterior of ships may not be possible, and solar panels designed to be deployed in space may not be capable of being deployed under Martian gravity. Although an established Mars settlement may be able to provide power to landed ships, the first ships on Mars could be required to rapidly deploy solar panels to provide the power needed for their operation. Batteries can provide some service, but not for the number of years the first ships will be on Mars.
Photovoltaic arrays will be subject to damage from dust, as well as a reduction capacity from dust deposits. Some form of cleaning mechanism is required. For a settlement, this work may be done by the colonists themselves, or be automated in various ways. Solar tracking systems require even more maintenance.
- G.D.J. Harper - Domestic solar energy: a guide for the home owner 2009. ISBN 978-1-84797-060-2 p. 140