I need solutions for an efficient cooling system for server room,because the actual cooling system stops around
-20*C.I'm searching for an additional system to use only in winter at lower temperatures and if it is possible to use the outside cold air for energy saving. Any suggestions?
To cool an entire room to temps that low, and efficiently no less, would need an industrial freezing solution. Honestly, I think you are going a bit overboard with this! I have seen many computer rooms in my day and none have needed anything more that regular A/C at ~15C.
The big problem is that outside temperature reached -20*C last year which caused cooling system not ruuning and servers overheating. I need a solution to prevent worst weather conditions and if it is possible a system for using the external fresh air to cool the room.(temperature and humidity control)
with an industrial cooling system like you want, all that effiency you want from your servers, will be wasted by adding on the freezer system, and why do you need a server room below freezing? if you need it to be that efficient, might as well relocate to the Swiss alps and setup there
I think OP is wanting a cooling system that can WITHSTAND temperatures of -20C, not cooling to -20C.
Anyway, a furnace might help with your issues, OP I'm not too sure where you live, but we typically have a little kerosene stove we use whenever it gets cold, which helps a lot with the cold inside the house.