Heat pump operation method and heat pump system

1. A heat pump operation method for a heat pump which generates heat using power generated by a power generation device and power supplied from an energy supplier, the method comprising:

obtaining, on a per time unit basis, generated power which is an amount of the power generated by the power generation device, load power which is an amount of the power consumed by an electric load which operates using the power generated by the power generation device, surplus power which is a difference between the generated power and the load power, and a magnitude of an impact of a reverse flow of the power generated by the power generation device on the energy supplier, wherein the magnitude of impact is based on a voltage of a power grid, and includes first, second and third states; and

controlling operation of the heat pump to cause the heat pump to consume an amount of power for generating heat adjusted to follow the surplus power obtained on a per time unit basis,

wherein in the controlling,

when the magnitude of the impact is in the first state, in which the voltage of the power grid is greater than a predetermined first threshold value, the operation of the heat pump is controlled to cause the heat pump to consume an amount of power equivalent to a larger one of (i) a value two standard deviations above a mean of the surplus power obtained over a given prior period of time measured from a present time, and (ii) the surplus power obtained in the last one of the time units,

when the magnitude of the impact is in the second state, in which the voltage of the power grid is less than or equal to a predetermined second threshold value, the operation of the heat pump is controlled to (i) permit the reverse flow of the surplus power and (ii) cause the consumption of power supplied from the energy supplier to approach zero, and

when the magnitude of the impact is in the third state in which the voltage of the power grid is less than or equal to the first threshold value and greater than the second threshold value, the operation of the heat pump is controlled to cause the heat pump to consume an amount of power equivalent to the surplus power obtained in a last one of the time units.

2. The heat pump operation method according to claim 1 ,

wherein, in the controlling, when the magnitude of the impact is in the second state, the operation of the heat pump is controlled to cause the heat pump to consume an amount of power equivalent to a smaller one of (i) a value two standard deviations below a mean of the surplus power obtained over a given prior period of time measured from a present time, and (ii) the surplus power obtained in the last one of the time units.

3. The heat pump operation method according to claim 1 ,

wherein, in the controlling, the operation of the heat pump is controlled to cause the heat pump to consume an amount of power adjusted to follow the surplus power obtained on a per time unit basis when a first condition is met, the first condition being that the surplus power remains greater than a predetermined threshold value for a given prior period of time measured from a present time.

4. The heat pump operation method according to claim 3 ,

wherein, in the obtaining, an amount of heat in a water storage tank which stores hot water heated by the heat generated by the heat pump is obtained on a per time unit basis, and

in the controlling, the operation of the heat pump is controlled to cause the heat pump to consume the amount of power adjusted to follow the surplus power obtained on a per time unit basis, when a second condition is met in addition to the first condition, the second condition being that the amount of heat in the water storage tank obtained in the last one of the time units is less than or equal to a predetermined upper limit.

5. The heat pump operation method according to claim 4 ,

wherein, in the controlling, the operation of the heat pump is controlled to cause the heat pump to consume the amount of power adjusted to follow the surplus power obtained on a per time unit basis, when a third condition is met in addition to the first condition and the second condition, the third condition being that the amount of heat in the water storage tank obtained in the last one of the time units is greater than a predetermined lower limit.

6. The heat pump operation method according to claim 1 ,

wherein, in the controlling:

an ambient temperature, which is a temperature surrounding the heat pump, an inlet water temperature, which is a temperature of the hot water flowing from a water storage tank, which stores hot water, through a heat exchanger, which heats the hot water stored in the water storage tank with the heat generated by the heat pump, and a heated water temperature, which is a temperature of the hot water supplied to the water storage tank from the heat exchanger, are obtained;

control parameters are obtained, the control parameters (i) causing the heat pump to consume the amount of power adjusted to follow the surplus power obtained on a per unit time unit basis, and (ii) causing the heat pump to increase the temperature of the hot water from the inlet water temperature to the heated water temperature; and

the operation of the heat pump is controlled according to the obtained control parameters.

7. The heat pump operation method according to claim 6 ,

wherein in the controlling, the control parameters corresponding to input information including the amount of power consumed by the heat pump, the ambient temperature, the inlet water temperature, and the heated water temperature, are obtained by referring to a control table holding the input information and the control parameters corresponding to a combination of the input information.

8. The heat pump operation method according to claim 7 ,

wherein discrete values of the input information are held in the control table, and in the controlling, when the combination of the obtained input information is not held in the control table, the control parameters corresponding to the combination of the obtained input information are obtained by linear interpolation based on a plurality of the control parameters held in the control table.

9. The heat pump operation method according to claim 5 ,

wherein in the controlling, when at least one of the first condition, the second condition, and the third condition is not met, the operation of the heat pump is controlled to cause the heat pump to consume an amount of power comparable to a rated power of the heat pump.