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How Does a Water Source Heat Pump Work?

How Does a Water Source Heat Pump Work?

Apr 15,2022
Heat pumps are an innovative way to harness the natural thermal energy of the ground, atmosphere, and even water around us. They can use the heat already present to heat your home without using gas, thus reducing the amount of carbon dioxide produced in your home.

These amazing appliances work even when the outside temperature is below zero. This is because, although we may feel cold outside, the pump can still utilize some heat. Additionally, the ground typically remains warmer than the air, so even if the outside temperature drops below zero, the ground can remain a mild 10℃.

Water source heat pumps can heat your home using natural heat from lakes, ponds, rivers, springs, wells, or boreholes. The heat it produces can be further heated with electricity and then supplied to your faucets, radiators, and underfloor heating. A water source heat pump can replace your home's gas boiler, and it is thought that heat pumps, in general, will become more popular in the coming years. 

How do water source heat pumps work?

Water source heat pumps use refrigerants to transfer heat from water to your home. Before we go any further, you should understand two types of systems: closed-loop and open-loop.

Closed-loop systems transport water mixed with antifreeze through a series of coils or heat exchange plates submerged in water sources such as lakes, although this may require planning permission due to the risk of water contamination. 

As the mixture passes through the coil, it absorbs energy from the water and sends it directly to the heat pump. In an open-loop system, water is drawn directly from the lake and sent directly to the heat pump. Once the heat is removed from the water, it can be pumped back into the lake.

Water is also a very suitable heat source for heat pumps. Groundwater maintains a constant temperature between 7℃and 12℃, even on cold winter days. In order to use groundwater for a heat pump, groundwater must be drawn through a water supply well and delivered to the evaporator of the water/water heat pump. The cooling water then passes through the return well.

Surface water (lakes or rivers) can also be used as a heat source, but it should be noted that temperatures can fluctuate greatly depending on the season.

No matter which system you have, heat is pumped from the water to the intermediate plate heat exchanger. Through the intermediate circuit, the energy is transferred to the heat exchanger or evaporator of the heat pump, where it is absorbed by the refrigerant. 

As the refrigerant heats up, it changes from liquid to gas. Refrigerant is a very powerful heat sink that can absorb heat from very low temperatures. This is why heat pumps are so useful in cold climates. 

Once the refrigerant turns into a gas, it is compressed to raise the temperature to a more useful level and then enters the heat exchanger (condenser). In the condenser, heat can be released to heat your water and radiator. As the gas begins to cool, it condenses and turns back into a liquid. When this happens, it is drawn back through the expansion valve to start the process all over again. 

A real benefit of water (and ground) heat pumps in summer are the option of passive cooling. It is also called "natural cooling". This process transfers the cooler temperature of the groundwater directly into the house heating circuit.

For this purpose, the heat pump compressor is idle. Additional heat exchangers provide system separation. Free cooling with a water heat pump is very efficient as it only requires two circulating pumps to run. During natural cooling, only the heat pump is activated to generate domestic hot water.

Free cooling is possible by using the following systems:

Floor heating system

Fan convector

Icy ceilings

Concrete core tempering

By replacing the cooling of the heated surface, the system is conditioned to avoid condensation, i.e. below the dew point of the heated surface.

The closer the water source is to your home, the more beneficial the system will be to you. Otherwise, the pump may be using too much electricity to pump water from the source to your home. This means that the water source should also not be located too high.

Certain environmental regulations must also be followed before the system is installed. Open-loop systems may affect groundwater temperatures and may require permission from the Environment Agency.

How efficient is a water source heat pump?

The efficiency of a heat pump will depend on where it gets its heat from. Air source heat pumps are the least efficient, followed by ground source heat pumps. 

Water source heat pumps are usually the most efficient as the source temperature is usually higher in winter, between 7℃and 12℃, however, lakes/rivers can also freeze over in winter depending on geographic location and local weather patterns, so the source temperature may not be as favorable as the temperature from the ground.

When using flowing water from a stream or river, the extracted heat is continuously replaced by warmer water that is not locally cooled by the operation of the heat pump. This increases the efficiency of the water source heat pump and also prevents the water from freezing, which can be a problem with stagnant water.

Ground source heat pumps typically operate with a coefficient of performance (CoP) of 4.8 (B/W of 0/35C). This measurement calculates the efficiency of the heat pump based on the comparison of the energy input to the energy output. For example, if a water source heat pump uses 1kW of electricity and produces 3kW of heat, the CoP will be 4. A heat pump with four CoPs will be more efficient than this. The CoP of a water source heat pump is typically around 6.0 (W/W 10/35C). 

The above describes the working principle of the water source heat pump, if you plan to buy it, please contact us.

SUOHER is a professional custom heat pump supplier and manufacturer. We have a team with extensive experience in heat pump design, processing, quality control, and controller function development. Our target is global, including Europe, South America, South Africa, and Asia.

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