A heat trace system for heating vessels of a piping system, the heat trace system comprising: a temperature control system comprising: a programmable controller comprising at least one microprocessor; and a power source connected to the controller; a plurality of heat trace elements that are adjacent to vessels of the piping system, and wherein the plurality of heat trace elements are connected to the power source of the temperature control system; and a plurality of temperature sensor modules distributed throughout the piping system, wherein: each of the temperature sensor modules comprises a temperature sensor for sensing a temperature of a localized point of a vessel of the piping system; and the plurality of temperature sensor modules are configured to transmit sensed temperature data, sensed by the temperature sensors, to the temperature control system; wherein the heat trace system is characterised in that the plurality of temperature sensor modules are connected to and powered by an associated heat trace element of the plurality of heat trace elements; and each of the temperature sensor modules further comprises an energy storage device connected to the associated heat trace element for storing energy from the associated heat trace element, wherein the energy stored by energy storage device from the associated heat trace element is for powering the temperature sensor of the temperature sensor module. a temperature control system comprising: a programmable controller comprising at least one microprocessor; and a power source connected to the controller; a programmable controller comprising at least one microprocessor; and a power source connected to the controller; a plurality of heat trace elements that are adjacent to vessels of the piping system, and wherein the plurality of heat trace elements are connected to the power source of the temperature control system; and a plurality of temperature sensor modules distributed throughout the piping system, wherein: each of the temperature sensor modules comprises a temperature sensor for sensing a temperature of a localized point of a vessel of the piping system; and the plurality of temperature sensor modules are configured to transmit sensed temperature data, sensed by the temperature sensors, to the temperature control system; each of the temperature sensor modules comprises a temperature sensor for sensing a temperature of a localized point of a vessel of the piping system; and the plurality of temperature sensor modules are configured to transmit sensed temperature data, sensed by the temperature sensors, to the temperature control system; wherein the heat trace system is characterised in that the plurality of temperature sensor modules are connected to and powered by an associated heat trace element of the plurality of heat trace elements; and each of the temperature sensor modules further comprises an energy storage device connected to the associated heat trace element for storing energy from the associated heat trace element, wherein the energy stored by energy storage device from the associated heat trace element is for powering the temperature sensor of the temperature sensor module.