Stratification storage water heater

A heating system connected to an electricity grid, the heating system comprising:

• a storage tank for a liquid, a heating apparatus, a control unit, hydraulic connections, and recirculation devices the storage tank being a tank for a liquid, the lower portion of which is configured to be connected to an inlet connection of a liquid distribution network, and an upper portion of which is configured to be connected to an outlet connection to a liquid delivery point,
• the heating apparatus comprising at least:
• a piping connection arranged between a first end called an inlet and a second end called an outlet,
• a heating element in a heat exchange relationship with the piping connection, the hydraulic connections include:
• a lower hydraulic connection between a lower portion of the storage tank and the inlet,
• an upper hydraulic connection between an upper portion of the storage tank,
• and the outlet,
• the recirculation devices are arranged to convey the liquid through the piping connection,
• the control unit is configured for:
• receiving an information about a power supplied into the electricity grid, in a quantity unbalanced versus a power demand and/or about a power produced locally from renewable sources in surplus versus local consumption, and in response to that information,
• varying the electric power consumption P of the heating element and/or varying a thermostating temperature, from a set temperature Ttarget, to a higher “surplus temperature” Tsur, in the case of an available electric power surplus, and to a lower temperature in the case of an available electric power short of demand,
• the storage tank, the piping connection and the hydraulic connections are arranged to form a hydraulic circuit in which the liquid, under the force of a pressure difference, can be drawn from the lower portion of the storage tank, heated in the piping connection, and sent to the upper hydraulic connection, so that the liquid in the storage tank can be heated with a substantially monotonically increasing temperature gradient from the engagement point of the lower hydraulic connection to the engagement point of the upper hydraulic connection,
• so that heating system is configured to store the heat generated in the portion of the water that is substantially likely to be withdrawn first.