Current models for dark energy include a cosmological constant and scalar field models such as quintessence and k–essence. By measuring the dark energy sound speed, $c_{\hbox{\scriptsize\it eff}}$, and its equation of state parameter, $w$, one can distinguish between these. Here we investigate the possibility of measuring $c_{\hbox{\scriptsize\it eff}}$ and $w$ using combined observations from the SKA and CMB experiments. We present theoretical predictions for the cross–power spectrum of ISW fluctuations in the CMB and the expected field of HI galaxies detectable with the SKA.
