Is energy always conserved?

Another example of non conservation of energy it the temperature of the space. No matter where we look, it's 2.9 Kelin, but if we use thermodynamic principles or any other principles, the temperature of the Univverse should now be much much much closer to Zero Kelin, using ANY MODEL of exansion of the universe. 

Much much much closer to "us", there are many methods today to slow down molecules (and this way to lower their temperature),  to do it, people are obviously building systems alowing no energy transfers withe the "exterior". The temperature of the molecule is directly linked to it's speed and of course it's energy. But as soon as we stop cooling the molecule ( its equivalent to "slowing down" the molecule), it automatically jump again to 2.9 Kelvin. 

From where the molecule takes the energy to jump back to 2.9K, in those systems not allowing any energy transfer ? From nowhere apparently. And why do we find again 2.9 Kelvin, the same temperature as the Universe, a temperature that SHOULD (according to thermodynamics and all theories of universe expansion) be far lower......

So energy can not only be apparently lost like for the redshift, it can also be apparently created........