The paper explores the possibility that the current accelerated expansion of the universe is explained by a quintessence model with an exponential scalar potential, \( V = V_0 e^{-\lambda \phi} \), where \(\lambda \geq \sqrt{2}\) and the universe is open, favoring string theory realizations and no cosmological horizon. The authors analyze the full cosmology of the model, including matter, radiation, and optional negative spatial curvature, for all \(\lambda > 0\), using an extensive dynamical system analysis. They find that minimal physical requirements, such as past radiation domination and current accelerated expansion, lead to an upper bound \(\lambda \lesssim \sqrt{3}\), which increases slightly with observed spatial curvature. Cosmological solutions start in a kination epoch, transition through radiation and matter dominated phases, and enter an accelerating phase, which is only transient for \(\lambda > \sqrt{2}\). Field distances between Big Bang Nucleosynthesis (BBN) and today are sub-Planckian. The paper discusses possible string theory origins and phenomenological challenges, such as time variation of fundamental constants, and provides theoretical predictions for model parameters, particularly the varying dark energy equation of state parameter, to be fitted to data from recent surveys like DES-Y5 and DES.The paper explores the possibility that the current accelerated expansion of the universe is explained by a quintessence model with an exponential scalar potential, \( V = V_0 e^{-\lambda \phi} \), where \(\lambda \geq \sqrt{2}\) and the universe is open, favoring string theory realizations and no cosmological horizon. The authors analyze the full cosmology of the model, including matter, radiation, and optional negative spatial curvature, for all \(\lambda > 0\), using an extensive dynamical system analysis. They find that minimal physical requirements, such as past radiation domination and current accelerated expansion, lead to an upper bound \(\lambda \lesssim \sqrt{3}\), which increases slightly with observed spatial curvature. Cosmological solutions start in a kination epoch, transition through radiation and matter dominated phases, and enter an accelerating phase, which is only transient for \(\lambda > \sqrt{2}\). Field distances between Big Bang Nucleosynthesis (BBN) and today are sub-Planckian. The paper discusses possible string theory origins and phenomenological challenges, such as time variation of fundamental constants, and provides theoretical predictions for model parameters, particularly the varying dark energy equation of state parameter, to be fitted to data from recent surveys like DES-Y5 and DES.