This would seemingly be a massive KW load depending on the size of the structure and the difference to outside temp you want to try and maintain.
They're called "radiant heaters." It works the same way the Sun does: it has little direct effect on the temperature of the air, but it makes you feel warm. The air temperature is impacted more by reflected heat from the ground than by sunlight passing through the air. Just think of the difference between standing in the direct sunlight and stepping one foot away and finding yourself in shade. The air temperature is the same in both locations, but the way you feel is vastly different.Most 'open-air' kinds of places (like auto repair garages) use infra-red heaters mounted near the ceiling, aiming at the area below. Some are electric, some are gas. But they don't try to heat the air, they try to heat the objects (ie people) below.