Heat Pumps: What about their rentability?

Heat pumps rentability has still secrets for some people who intend to invest in it as a heating source for their buildings.

Heat pumps are a key technology for sustainable buildings and for households aiming for more profitable but also clean solution to heat their buildings at winter, and also to cool it down in the summer.

A lot of people still ignore how this technology works and why it’s absolutely worthy to invest in it. In this article, we’re going to give a clear and easy to understand explanation on how heat pumps works, and why we consider them as clean and reliable technology.

How does it work?

A heat pump has four main components: Condenser, evaporator, compressor, and an expansion valve. A refrigerant circulates through those four main components to ensure the heat transfer from the source to the other side.

The operation mode of a heat pump has two stages:

• Heat extraction from the heat source

The heat is drawn from a heat source via the evaporator. This heat source maybe air, ground, water, wasted heat. A refrigerant transfer the extracted calories to the condenser with the help of a compressor. The compressor plays the role of a pump that raises the pressure and ensure the refrigerant circulation. The expansion valve reduces at a later stage the pressure according to the design cycle of the heat pump.

• Heat transfer from the heat pump to the heating system

The refrigerant releases it’s energy in the condenser, which transfer it to the heating system. It could be forced air systems like central air handling units or indoor VRV splits systems or hydronic systems such as radiators and under-floor heating. The refrigerant goes then through the expansion valve who decreases its pressure and cools it completely down to liquid status.

Why is a heat pump so worthy to invest in it?

A heat pump as mentioned has a main function: extracting calories from a heat source and transferring it to your heat distribution system in your building. A heat pump can also reverse its cycle and cool-down therefore the building. This last configuration and it’s feasibility depends generally on the scale of the project, and mainly if your heating terminal equipments can also cool down your indoor.

The compressor plays a key role as it maintain the circulation of the refrigerant within the heat pump. To ensure this function, the compressor converts the electrical energy into mechanical energy.

Now as the compressor consumes electrical energy, is it really worthy to invest in a heat pump?

A heat pump consumes hence electricity to produce the heat needed to warm up a building. But the ratio between the amount of electrical energy and heat energy is quite high, that leaves no doubt about the rentability of a heat pump. This ratio called coefficient of performance (COP) of a heat pump may vary according to the heat source and the model of the heat pump. There is two type of COP:

• COP : The COP is the ratio of the heat output (kW) over the electrical input (kW) at a single moment. The COP should decrease if the input temperature available falls. That’s what makes a COP fluctuating during the heating season.
• SPF : The SPF is the average Coefficient of Performance (CoP) of a heat pump over the full heating season. This factor is the best comparative indicator of heat pumps and their rentability, but it’s harder to quantify. The SPF or SCOP is estimated via a thermal simulation, or via an energy accounting system in a post installation stage.

Here below some indicative SPF according to the heat source:

Conclusion:

An investment in heat pumps is not anymore a concern of rentability, but about the optimal choice. Choosing the best heat pump for your building could be a headache, as different parameters are involved. It’s recommended to consult a professional before making any purchase decision. For medium and large scale of projects, an engineering office intervention is absolutely a necessity for the suitable conception and implantation of a building heating system including the heat pump.