Among other things, an integrated portable energy conversion mat is to be installed at a pavement surface over which a car or truck is to pass. The mat has a width at least as wide as the distance between the outermost edges of the treads of the tires located at an axle of the car or truck. The mat has a top surface over which the tires of the car or truck are to pass. The mat includes a sealed enclosed space housing and energy conversion system. The energy conversion system includes two sets of channels that extend along a length of the mat and contain hydraulic fluid under pressure. An energy converter converts energy carried by the hydraulic fluid in response to the tires of the car or truck passing over the top surface into electrical energy. An electrical port is coupled to the energy converter and exposed at an outer surface of the mat. The two sets of channels are spaced apart across the width of the mat by a distance that corresponds to the distance between the treads of the tires located at an axle of the car or truck. The energy converter is located within the sealed enclosed space of the mat and in the portion of the mat that is between the two sets of channels.