Indeed, there seems to be a contradiction between the concept of heat death and the principle of energy conservation, which states that energy cannot be created or destroyed, only transformed from one form to another. The idea of heat death is based on the notion that the universe will eventually reach a state of maximum entropy, where no useful energy remains available for conversion into other forms of work.
The reconciliation of these two concepts lies in the consideration of the distribution and availability of energy. While energy is conserved overall, it can become increasingly dispersed and evenly distributed throughout a closed system, such as the universe, as entropy increases. In this scenario, the energy becomes so diffused and uniformly spread that it becomes unusable for any meaningful work or further transformations.
Heat death suggests that the universe will eventually reach a state where there are no energy gradients or differences to drive processes. It doesn't mean that energy itself is destroyed but rather that it becomes effectively unusable for any practical purposes. In this state, the universe would experience a state of thermal equilibrium, where no further energy transfers or transformations can occur.
It's important to note that the concept of heat death is based on current understanding and theories, such as the second law of thermodynamics. However, the ultimate fate of the universe is still an open question and an active topic of scientific investigation. New discoveries and theoretical advancements may provide further insights and potentially modify our understanding of these concepts in the future.