A solar photovoltaic (PV) water heating system includes a tank (1.020) including at least a first heating unit (1.016) having at least first and second heating elements (1.016.1 . . . 1.016.x), at least one of which is switchable (1.014.1A . . . 1.014.1m); a PV solar collector (1.002); an inverter (1.004) adapted to convert the output from the PV collector to an alternating power supply; a modulator (1.060) to modulate the alternating power supply from the inverter; a controller (1.040) adapted to control the modulator and the switching of the or each switchable heating element; wherein the controller is adapted to control the modulator and the switchable heating elements to maximize the energy drawn from the PC collector.

A method of operating a water heater receiving electrical power from an electrical grid. The method includes providing a water heater in a locked state. A digital key module may be communicatively coupled (for example, via wired or wireless communication) to the water heater and used to unlock the water heater placing the water heater into an unlocked state. Such unlocking of the water heater must only be done for such water heaters that are enrolled in a utility demand response program.

An electrical water heater adapted for energy management and a method of controlling the consumption of electrical power from the power supply grid of a utility is described. The bottom resistive heating element of the water heater is a dual element resistive heating element which has a high power rated resistive heating element to heat water and a further low power rated resistive heating element. The power rating of the low power resistive heating element is calculated to be lower than the supply grid diversified mean load. A controller has a communication link with a utility which manages the power supply grid. The utility can control the resistive heating elements of the dual element in such a way, and depending on conditions of the grid, to conserve energy and regulate its frequency thereby resulting in a cost saving to the consumer and the utility. The low power rated resistive heating element is also connectable to an alternative power source.

An electrical water heater adapted for energy management and a method of controlling the consumption of electrical power from the power supply grid of a utility is described. The bottom resistive heating element of the water heater is a dual element resistive heating element which has a high power rated resistive heating element to heat water and a further low power rated resistive heating element. The power rating of the low power resistive heating element is calculated to be lower than the supply grid diversified mean load. A controller has a communication link with a utility which manages the power supply grid. The utility can control the resistive heating elements of the dual element in such a way, and depending on conditions of the grid, to conserve energy and regulate its frequency thereby resulting in a cost saving to the consumer and the utility. The low power rated resistive heating element is also connectable to an alternative power source.

Described embodiments relate generally to energy harvesting systems and interface devices for such systems. In particular, such energy harvesting systems may be configured to harvest kinetic energy from the environment, such as wind, hydro, wave or geothermal energy or to harvest electromagnetic energy like solar radiation. Embodiments also relate to systems and methods to facilitate remote monitoring and/or control of a system comprising an interface device.

An electrical water heater adapted for energy management and a method of controlling the consumption of electrical power from the power supply grid of a utility is described. The bottom resistive heating element of the water heater is a dual element resistive heating element which has a high power rated resistive heating element to heat water and a further low power rated resistive heating element. The power rating of the low power resistive heating element is calculated to be lower than the supply grid diversified mean load. A controller has a communication link with a utility which manages the power supply grid. The utility can control the resistive heating elements of the dual element in such a way, and depending on conditions of the grid, to conserve energy and regulate its frequency thereby resulting in a cost saving to the consumer and the utility. The low power rated resistive heating element is also connectable to an alternative power source.

A solar photovoltaic (PV) water heating system includes a tank including at least a first heating unit having at least first and second heating elements, at least one of which is switchable; a PV solar collector; an inverter adapted to convert the output from the PV collector to an alternating power supply; a modulator to modulate the alternating power supply from the inverter; a controller adapted to control the modulator and the switching of the or each switchable heating element; wherein the controller is adapted to control the modulator and the switchable heating elements to maximize the energy drawn from the PV collector.

A solar photovoltaic (PV) water heating system includes a tank including at least a first heating unit having at least first and second heating elements, at least one of which is switchable; a PV solar collector; an inverter adapted to convert the output from the PV collector to an alternating power supply; a modulator to modulate the alternating power supply from the inverter; a controller adapted to control the modulator and the switching of the or each switchable heating element; wherein the controller is adapted to control the modulator and the switchable heating elements to maximize the energy drawn from the PV collector.

A solar photovoltaic (PV) water heating system includes a tank including at least a first heating unit having at least first and second heating elements, at least one of which is switchable; a PV solar collector; an inverter adapted to convert the output from the PV collector to an alternating power supply; a modulator to modulate the alternating power supply from the inverter; a controller adapted to control the modulator and the switching of the or each switchable heating element; wherein the controller is adapted to control the modulator and the switchable heating elements to maximize the energy drawn from the PV collector.

A solar photovoltaic (PV) water heating system includes a tank including at least a first heating unit having at least first and second heating elements, at least one of which is switchable; a PV solar collector; an inverter adapted to convert the output from the PV collector to an alternating power supply; a modulator to modulate the alternating power supply from the inverter; a controller adapted to control the modulator and the switching of the or each switchable heating element; wherein the controller is adapted to control the modulator and the switchable heating elements to maximize the energy drawn from the PV collector.