A water-to-water heat pump works by extracting heat from a water source and transferring it to a water-based heating or cooling system. These systems efficiently utilize the relatively stable temperature of water sources for heating and cooling purposes. Here's a detailed breakdown of the process:
The Process Explained
The fundamental principle of a water-to-water heat pump revolves around a refrigerant cycle. This cycle allows the pump to move heat, rather than generating it. Here's how it works:
- Heat Extraction: The process begins with a water source, which can be a well, a lake, or a river. The heat pump uses this water as a source of energy.
- Evaporator Coil: A refrigerant, with a very low boiling point, circulates through an evaporator coil. This coil is in contact with the water source. As the water passes by the coil, it transfers some of its heat to the refrigerant.
- Refrigerant Vaporization: The heat absorbed from the water causes the liquid refrigerant to vaporize into a low-pressure gas.
- Compression: The refrigerant gas is compressed, increasing both its temperature and pressure.
- Condensation: The now hot, high-pressure refrigerant gas is then passed through a condenser coil, which is connected to the hydronic heating or water-based cooling system of the building.
- Heat Transfer: The refrigerant releases the heat it absorbed from the water source and the heat of compression, which is now used to heat water in the hydronic system or cool water in the water-based cooling system.
- Refrigerant Liquefaction: As it releases heat, the refrigerant condenses back into a liquid but under high pressure, starting the cycle again. It then goes through an expansion valve, reducing the pressure and thus the temperature, ready to restart the cycle.
Key Components and Their Roles
| Component | Function |
|---|---|
| Water Source | Provides a stable and consistent temperature for heat extraction. |
| Evaporator Coil | Absorbs heat from the water source and transfers it to the refrigerant. |
| Refrigerant | A fluid that cycles through the system, absorbing and releasing heat at different points. |
| Compressor | Compresses the refrigerant gas, increasing its temperature and pressure. |
| Condenser Coil | Transfers the heat from the refrigerant to the hydronic heating or water-based cooling system. |
| Expansion Valve | Reduces the pressure of the refrigerant, allowing it to absorb more heat in the evaporator coil. |
| Hydronic System | Water is heated in the system, which is then used for indoor space heating. |
| Water-Based System | Water is cooled in the system, which is then used for indoor space cooling. |
Practical Examples and Insights
- Geothermal Systems: These often use groundwater as a heat source, tapping into the earth's stable underground temperature.
- Lake/River Systems: These use the water from a nearby body of water as the heat source. This can be an efficient system given a large enough resource.
Benefits of Water-to-Water Heat Pumps:
- High Efficiency: They are highly efficient in heat transfer due to the stable temperature of the water source.
- Versatility: These systems can be used for both heating and cooling.
- Environmentally Friendly: They do not rely on fossil fuels for direct heating or cooling, making them a sustainable choice.
In summary, water-to-water heat pumps use a refrigerant cycle to extract heat from a water source and transfer it to a hydronic system for space heating or a water-based cooling system, providing an efficient and versatile heating/cooling solution.
