No, black bin liners cannot heat a pool.
The reasons for this are:
- Black bin liners will not contain the necessary components to facilitate heating of a pool.
- The plastic material is too thin to provide any real insulating effect in order to raise and retain the temperature of water.
- Even if placed over direct sunlight, they won't be able to transfer enough thermal energy into the water below them due to their lack of insulation properties or reflective surfaces.
Therefore, it would be unwise and potentially dangerous to use black bin liners as an effective method for heating up a pool.