Certain aspects of natural gas liquid fractionation plant waste heat conversion to cooling capacity using Kalina Cycle can be implemented as a system, which includes a waste heat recovery heat exchanger to heat a buffer fluid stream by exchange with a heat source in a natural gas liquid fractionation plant. The system includes a Kalina cycle energy conversion system including one or more first energy conversion heat exchangers to heat a first portion of a working fluid by exchange with the heated buffer fluid stream, a separator to receive the heated working fluid and to output a vapor stream of the working fluid and the liquid stream of the working fluid, and a cooling subsystem including a first cooling element to condense the vapor stream of the working fluid and a second cooling element configured to cool a process fluid stream from the natural gas liquid fractionation plant by exchange with the condensed vapor stream of the working fluid.