The heat pump is ‘hot’ and receives a lot of attention in view of the ambition to achieve the much-discussed climate objectives. It is often thought: CV out and heat pump in, Kees is done. But is it really that simple? In a report by Radar, broadcast on Monday 25 February 2019, the honest answer to this question and the honest truth about heat pumps was sought.
The figures do not lie in the research conducted by Radar: 1 in 5 respondents is dissatisfied with the heat pump that has been used. Without a professional application, a heat pump can end in a major disappointment in the form of a higher energy bill or not being able to heat a building in the winter. But how should it be? The most important conclusion of the report from Radar: good insulation and the application of a low-temperature delivery system are the most important preconditions for a successful application of the heat pump as main heating.
Good insulation: the shell of the building
Good insulation of a building is always important and not only when using a heat pump. After all, insulation ensures that less energy is needed to heat the building: less heat escapes to the outside. An important term here is heat loss. With the help of a quick scan or an extensive thermal image report you can also determine how well it is insulated for your building. If the insulation is in order, the heat pump will function more efficiently and allow a comfortable indoor temperature.
Heating with low temperature heating
With a heat pump as main heating, it is important that the house is heated with a low temperature emission system, such as underfloor heating or low temperature radiators. The lower the flow temperature in the heating system, the better the heat pump performs. The savings are mainly due to the fact that the supply temperature of the water that goes to the low temperature radiators or underfloor heating is a maximum of 55 degrees Celsius. With conventional central heating, this can rise to 80 degrees Celsius. The system therefore needs to heat up to a lower temperature in order to get and keep the house comfortably warm.
Comparing system efficiency: (S)COP
Heat pumps come in different shapes and sizes. Compare it to a car: from Ferrari to Toyota and from Tesla to Opel. What they can differ and also the price tag is not the same. In fact, this also applies to heat pumps. But on what basis can a heat pump best be compared when it comes to efficiency? The COP, the Coefficient of Performance, is a good measuring point for this. The COP shows the relationship between the energy consumption of the system and the useful amount of heat that results, measured at an outside temperature of 7 degrees Celsius and a release temperature of 35 degrees Celsius. The higher the COP, the more efficient the installation. With a heat pump, a COP of 4 means that 1 kW of electricity is needed from the grid (or solar panels!) to give off 4 kW of heat.
In order to get a good comparison for the Netherlands, an energy label now also contains a Seasonal Coefficient of Performance: a weighted COP based on our region and climate. This is an important factor in particular when an air heat pump is used. The SCOP makes a weighted average of the COP values at +12, +7, +2 and -7 degrees Celsius outside temperature. This provides a representative picture of the heating season for the Dutch climate.
In winter it is cold outside and the temperature difference that has to be bridged to the desired indoor temperature is greater than in summer. Partly for this reason, a heat pump runs with a lower COP in winter than in summer. It is therefore also crucial for an installer that he finds out in the technical data of a system which heating capacity is produced when it freezes outside, so that it is still pleasantly warm even at -10, -15 or even -20 degrees Celsius.
Sound from the heat pump
The Radar report touched on another tricky point: the noise made by the outdoor unit of the heat pump system. The amount of noise a heat pump makes is partly determined by the number of revolutions that the fan and compressor must make. The required speed in turn depends on the power of the heat pump. If a heat pump is oversized (the device has more power than is strictly necessary for the building), the fan and compressor need to make fewer revolutions and therefore produce less noise than a heat pump that can deliver exactly the required power. This can be a trade-off when choosing a slightly larger capacity heat pump.
The shape of the fan blade and the sound-insulating and damping measures taken by the manufacturer also play a role. During the installation phase, the use of rubber beams under the outdoor unit is also a method to limit the vibration and thus the noise.
Buffer tank application
The Radar report did not pay attention to the importance of a buffer tank for the efficiency of the heat pump system. In order for a heat pump to work efficiently, it must have sufficient active water available. If this is not enough, the system will ‘shuttle’, in other words regularly start up and shut down, which greatly reduces the efficiency. Sufficient active water can be achieved by using a buffer tank with an amount of content that is tailored to the system.
tap water
Also not mentioned in the Radar report is the provision of sanitary hot water. A boiler tank is used to also use the heat pump for domestic hot water. Hot water is stored here, so that hot water comes out of the tap at any time. A heat pump is not a continuous flow device like a combi boiler. Here too, the size of the boiler must be geared to the system and the wishes of the users.
The reversible operation of the heat pump for cooling
Another aspect of a heat pump that was not discussed in the Radar report is the reversibility of the heat pump. Is it hot outside and do you want to cool down your building? Then the heat pump can do this too. With a ground-based, geothermal heat pump, this is done with passive cooling. This means that only the use of the circulation pump makes use of the cold in the soil or water source. An air heat pump uses active cooling: the warm outside air is converted into cold air or cold water by the heat pump. This process requires the compressor in the heat pump and uses more energy than passive cooling. This is therefore only a comfort advantage and does not contribute to energy savings. The fact is that a central heating boiler does not have the option of cooling in the summer and therefore does not offer this comfort advantage.
Conclusion
The only correct conclusion from Radar’s report is: let a professional installer advise you. So take a good look at certification and feel free to ask about reference projects. Do you want Ambrava | Samsung is looking for an installer in your area? Please contact us via info@ambrava.nl or 055 527 7777.
