  Waste heat recovery for trucks via organic Rankine cycle is a promising
technology to reduce fuel consumption and emissions. As the vehicles are
operated in street traffic, the heat source is subject to strong fluctuations.
Consequently, such disturbances have to be considered to enable safe and
efficient operation. Herein, we find optimal operating policies for several
representative scenarios by means of dynamic optimization and discuss the
implications on control strategy design. First, we optimize operation of a
typical driving cycle with data from a test rig. Results indicate that
operating the cycle at minimal superheat is an appropriate operating policy.
Second, we consider a scenario where the permissible expander power is
temporarily limited, which is realistic in street traffic. In this case, an
operating policy with flexible superheat can reduce the losses associated with
operation at minimal superheat by up to 53 % in the considered scenario. As the
duration of power limitation increases, other constraints might become active
which results in part of the exhaust gas being bypassed, hence reduced savings.
