We elaborate on a model of conformal dark energy ( dynamical dark energy measured by the conformal age of the universe ) recently proposed in [ H. Wei and R.G .
Cai , arXiv:0708.0884 ] where the present-day dark energy density was taken to be \rho _ { q } \equiv 3 \alpha ^ { 2 } m _ { P } ^ { 2 } / \eta ^ { 2 } , where \eta is the conformal time and \alpha is a numerical constant .
In the absence of an interaction between the ordinary matter and dark energy field q , the model may be adjusted to the present values of the dark energy density fraction \Omega _ { \lower 2.0 pt \hbox { $ \scriptstyle q$ } } \simeq 0.73 and the equation of state parameter w _ { \lower 2.0 pt \hbox { $ \scriptstyle q$ } } < -0.78 , if the numerical constant \alpha 
takes a reasonably large value , \alpha \gtrsim 2.6 .
However , in the presence of a nontrivial gravitational coupling of q -field to matter , say \widetilde { Q } , the model may be adjusted to the values \Omega _ { \lower 2.0 pt \hbox { $ \scriptstyle q$ } } \simeq 0.73 and w _ { \lower 2.0 pt \hbox { $ \scriptstyle q$ } } \simeq - 1 , even if \alpha \sim { \cal O } ( 1 ) , given that the present value of \widetilde { Q } is large .
Unlike for the model in [ R.G .
Cai , arXiv:0707.4049 ] , the bound \Omega _ { \lower 2.0 pt \hbox { $ \scriptstyle q$ } } < 0.1 during big bang nucleosynthesis ( BBN ) may be satisfied for almost any value of \alpha .
Here we discuss some other limitations of this proposal as a viable dark energy model .
The model draws some parallels with the holographic dark energy ; we also briefly comment on the latter model .

PACS numbers : 95.36.+x , 98.80.Es