My alien race is able to absorb energy via the skin, like plants using sunlight for photosynthesis. The race eats a lot of food, like humans, But they need this absorbed energy for their proper inner functionality. They are cold-blooded, and they do not have any internal mechanism to keep their body temperature. They are depending on this absorbed heat for this. But they cant absorb direct sunlight. Some elements in this world have the power to absorb and emit heat from sunlight in a different form -and this race can absorb only that. The temperature on the planet is a bit lower - an average of 20°C.
Since they are absorbing the energy via the skin, it makes sense to wear fewer clothes and expose more skin - or is it the other way around - like wearing many layers of dress to make them keep warm? Also how will be their skin - I saw plants in cool places that have pointed and hard leaves, so will their skin need to be like that - very hard ? or pale skin like people who live in cold places? Thanks in Advance.