The larger pixels will also have an increased dark current, which are electrons generated not by photons but internally by the camera. Dark current is proportional to the surface area, and shows up in your images as light points. Generally the bigger pixels are better for planetary images where the pixels will not saturate as quickly. Cooling For a CCD camera to operate more efficiently it must be cool. For each drop in temperature of 6 degrees C, the dark current is divided in half.
Dark current is electrons generated by the electronics of the camera.
The most common way of cooling a CCD camera is with a Peltier cooler. The Peltier is a thermoelectric cooler. When a current is passed through it, heat is drawn from one side of the cooler to the other where it can be expelled. There are different ways to expel the heat. Many of the amateur cameras available today expel the heat by convection to the atmosphere, or ambient air.