  There is strong experimental evidence for pairing of polaronic carriers in
the normal state, two distinct energy scales, d-wave superconducting order
parameter,and charge segregation in the form of stripes in several cuprates.All
these remarkable phenomena might be unified in the framework of the bipolaron
theory as a result of the formation of mobile bipolarons in the normal state
and their Bose-Einstein condensation. Extending the BCS theory towards an
intermediate and strong-coupling regime we show that there are two energy
scales in this regime, a temperature independent incoherent gap and a
temperature dependent coherent gap combining into one temperature dependent
global gap. The temperature dependence of the gap and single particle (Giaver)
tunnelling spectra in cuprates are quantitatively described. A framework for
understanding of two distinct energy scales observed in Giaver tunnelling and
Andreev reflection experiments is provided. We suggest that both d-wave
superconducting order parameter and striped charge distribution result from the
bipolaron (center-of-mass) energy band dispersion rather than from any
particular interaction.
