A system including a photovoltaic panel having a first heat exchanger for absorbing heat from the panel and/or from the environment by a heat exchanging fluid, connected to a heat pump. A second heat exchanger is provided for absorbing heat by the heat exchanging fluid and a control means for controlling a flow of the heat exchanging fluid through the first heat exchanger and/or the second heat exchanger. The heat pump is arranged to cool the heat exchanging fluid. The system has the following operating modes: a first mode in which cooled heat exchanging fluid is fed to the first heat exchanger; and a second mode in which cooled heat exchanging fluid is fed to the second heat exchanger and then fed to the first heat exchanger.

A hot water supply system includes a first heat pump, a second heat pump, and a hot water storage tank. The first heat pump heats water stored in the hot water storage tank to make hot water. The second heat pump heats water supplied to the hot water storage tank.

A present heating system or heating and cooling system does not include a tank for storing potable hot water in anticipation of a potable hot water demand. Although one or more temperature sensors may be used for providing feedback to heating of the contents of a tank water heater to achieve a setpoint temperature, the effect of stratification can cause layers of fluid having different temperatures in the tank water heater. Therefore, although portions of the contents of a water heater may be disposed at a setpoint temperature that is unfavorable for Legionella proliferation, there potentially exists other portions that may be disposed at temperatures suitable for Legionella proliferation, especially when the contents have been left unused for an extended period of time.

A hot water supply apparatus includes a heat pump device in which a compressor and a heat exchanger are connected, a heat medium circuit connected to the heat pump device via the heat exchanger, a tank that stores water after the water exchanges heat with a heat medium of the heat medium circuit, two tank-temperature detection units attached at different heights to the tank and each detects a temperature of water in the tank, and a controller that controls, by using a value detected by each of the two tank-temperature detection units, a temperature of water in the tank. The controller sets a target hot water supply temperature based on a stored-hot-water temperature detected by one of the two tank temperature detection units and a within-tank temperature difference that is a difference between temperatures within the tank detected by the two tank-temperature detection units.

A hot water supply apparatus includes a heat pump device in which a compressor and a heat exchanger are connected, a heat medium circuit connected to the heat pump device via the heat exchanger, a tank that stores water after the water exchanges heat with a heat medium of the heat medium circuit, two tank-temperature detection units attached at different heights to the tank and each detects a temperature of water in the tank, and a controller that controls, by using a value detected by each of the two tank-temperature detection units, a temperature of water in the tank. The controller sets a target hot water supply temperature based on a stored-hot-water temperature detected by one of the two tank temperature detection units and a within-tank temperature difference that is a difference between temperatures within the tank detected by the two tank-temperature detection units.

A heat pump may include a compressor configured to compress a refrigerant, a first temperature sensor configured to detect an outdoor temperature, a second temperature sensor provided in heating pipes connected to a heating device, and a controller. Based on a first sensing value of the first temperature sensor, the controller may be configured to control a compressor, control power to a boiler, and/or calculate an expected efficiency of the heat pump. Based on the expected efficiency and/or a second sensing value of a second temperature sensor, the controller may be configured to control power to the boiler.

A heating system (1) has a turbine (20) for burning a fuel to provide flue gas and electrical energy. A flue gas heat exchanger (25) receives the flue gas and uses it to heat water in three of stages. An air conduit (2) receives inlet air (3) and gases from secondary inlets (5, 26) from within the system to elevate the temperature in the main conduit (2) above ambient. An evaporator (8) recovering heat from the air flow of the main conduit, and provides energy via an evaporator coil to an air source heat pump ASHP (50). A water source heat pump WSHP (60) receives a water feed at an elevated temperature from the ASHP (50), and it cools the flue gas in a third heat exchanger stage (25(c)). Hence, WSW efficiency is high and it provides product water, as do the first and second stages of the flue gas heat exchanger (25)

A heating system (1) has a turbine (20) for burning a fuel to provide flue gas and electrical energy. A flue gas heat exchanger (25) receives the flue gas and uses it to heat water in three of stages. An air conduit (2) receives inlet air (3) and gases from secondary inlets (5, 26) from within the system to elevate the temperature in the main conduit (2) above ambient. An evaporator (8) recovering heat from the air flow of the main conduit, and provides energy via an evaporator coil to an air source heat pump ASHP (50). A water source heat pump WSHP (60) receives a water feed at an elevated temperature from the ASHP (50), and it cools the flue gas in a third heat exchanger stage (25(c)). Hence, WSW efficiency is high and it provides product water, as do the first and second stages of the flue gas heat exchanger (25)

Air heating and potable water systems have a thermostat with a computer processing unit (CPU), a hot water heater, a hydronic air handler, and a primary pump controlling flow of hot water from the water heater into the hydronic air handler, which has a hydronic coil, a blower, and a first control panel having a CPU in operative communicates with the thermostat. The hydronic coil receives hot water from the water heater to warm air passing over the hydronic coil. The primary pump is in operative communication with the first control panel and an indicator of hot water flow. The indicator of hot water flow is in operative communication with either the thermostat or the first control panel, and any CPU in the system stores a priority instruction, which upon an indication of hot water flow deactivates or delays activation of the primary pump for a predetermined period of time.

Air heating and potable water systems have a thermostat with a computer processing unit (CPU), a hot water heater, a hydronic air handler, and a primary pump controlling flow of hot water from the water heater into the hydronic air handler, which has a hydronic coil, a blower, and a first control panel having a CPU in operative communicates with the thermostat. The hydronic coil receives hot water from the water heater to warm air passing over the hydronic coil. The primary pump is in operative communication with the first control panel and an indicator of hot water flow. The indicator of hot water flow is in operative communication with either the thermostat or the first control panel, and any CPU in the system stores a priority instruction, which upon an indication of hot water flow deactivates or delays activation of the primary pump for a predetermined period of time.