A heat pump extracts thermal energy from a heat source such as ambient air, the ground or water and raises it to a usable temperature level with the help of electrical energy. The generated heat can be used for space heating, domestic hot water or technical processes. Depending on their design, some heat pumps can also provide cooling.
Heat Pumps at a Glance
- The efficiency of a heat pump depends particularly on the temperature of the heat source and the required supply temperature.
- The coefficient of performance (COP) describes efficiency at a specific operating point, while the seasonal performance factor (SPF) evaluates performance over a longer period under real operating conditions.
- Thermal storage systems and the thermal storage capacity of a building enable heat pump operation to be shifted within certain limits.
- An EMS can coordinate the operation of a controllable heat pump with PV generation, electricity prices and electrical load limits.
How Does a Heat Pump Work?
Most heat pumps operate using a closed refrigerant circuit. A refrigerant absorbs heat from the environment in the evaporator and evaporates. An electrically driven compressor then increases the pressure and, consequently, the temperature of the refrigerant. In the condenser, the heat is transferred to the heating system or a thermal storage system. An expansion valve subsequently reduces the pressure before the cycle begins again.
The smaller the temperature difference between the heat source and the required output temperature, the more efficiently the heat pump can operate. Low supply temperatures, such as those used in underfloor heating systems, are therefore generally beneficial. At low outdoor temperatures or when high supply temperatures are required, efficiency usually decreases, meaning that more electrical energy is needed to provide the same amount of heat.
The coefficient of performance (COP) describes the ratio of heat output to electrical input at a defined operating point. In simplified terms, a COP of 4 means that under these conditions, approximately 4 kWh of heat can be provided using 1 kWh of electrical energy.
The seasonal performance factor describes the ratio between the amount of heat provided over a full year or heating season and the electrical energy consumed for this purpose. Its significance depends strongly on whether components such as circulation pumps, control systems and electric backup heaters are included within the defined system boundary.
Typical Heat Pump Applications
Heat pumps are used in residential, commercial and industrial buildings for space heating and domestic hot water production. In suitable applications, they can also provide process heat at a technically achievable temperature level.
Air-to-water heat pumps use ambient air as their heat source. Ground-source brine-to-water heat pumps extract energy from the ground through horizontal collectors or boreholes. Water-to-water heat pumps usually obtain heat from groundwater. The appropriate design depends on factors such as the location, required temperature level, available space and applicable permitting requirements.
In combination with a PV system, part of the heat pump’s operation can be shifted to periods of high on-site electricity generation. A domestic hot water tank or buffer tank stores thermal energy and partially separates heat generation from immediate heat demand.
When combined with a battery energy storage system (BESS), a heat pump can also use electrical energy that was stored previously. Whether this is economically beneficial depends on factors such as electricity prices, storage losses, available battery capacity and alternative uses of the BESS.
Benefits, Limitations and Technical Requirements
Heat pumps can make environmental heat usable and therefore provide more thermal energy than the electrical energy they consume. However, their actual efficiency depends strongly on the building, heat source, system sizing, required temperatures and control quality.
Frequent cycling, unsuitable system sizing and high supply temperatures can reduce efficiency. Intensive use of an electric backup heater also increases electricity consumption. Air-source heat pumps may additionally require energy-intensive defrost cycles.
Flexible operation must account for heat demand, comfort limits, minimum operating times, lockout periods and permitted switching frequencies. Operation can only be shifted if the building or a thermal storage system provides sufficient thermal flexibility.
Integration into an EMS also requires a suitable communication or control interface, such as Modbus, EEBus, an approved manufacturer API or a dedicated control contact. The availability of measurement data alone does not automatically mean that the interface also permits control commands or write access.
How Can EcoPhi Integrate a Heat Pump?
EcoPhi can record a heat pump’s electrical consumption and display it together with data from PV systems, BESS, electricity meters and other loads. Temperatures, operating states and internal measurements can only be integrated if they are available through the device interface or additional sensors.
If a suitable and approved interface is available, the EMS can coordinate operating permissions or setpoints based on PV surplus, electricity prices, load limits and defined comfort conditions. The specific functionality depends on the supported data points, available write access and project requirements.
Control commands are transmitted through the interfaces provided by the manufacturer and within the permitted operating limits. Directly switching the electrical supply off and on is not a standard form of EMS control and may bypass technical protection functions or required run-on periods. The heat pump’s internal controller remains responsible for the refrigerant circuit, compressor operation and safety functions.
Heat Pumps Summarized
A heat pump uses electrical energy to raise environmental heat to a usable temperature level. Its efficiency is significantly influenced by temperature conditions, the heating system and its control strategy. With suitable interfaces and sufficient thermal flexibility, an EMS can coordinate its operation with PV generation, electricity prices and other energy assets.
Frequently Asked Questions About Heat Pumps
What Is the Difference Between COP and SPF?
The COP describes the efficiency of a heat pump at a defined operating point. The SPF evaluates the ratio between the heat provided and the electrical energy consumed over a full year or heating season.
Why Does a Heat Pump Operate More Efficiently at Lower Supply Temperatures?
A low supply temperature reduces the required temperature lift between the heat source and the heating system. As a result, the compressor generally requires less electrical energy per unit of heat provided.
Can a Heat Pump Operate Only When PV Surplus Is Available?
Usually not entirely, because space heating and domestic hot water are also required outside periods of PV generation. However, an EMS can shift flexible operating periods to times with PV surplus, provided that comfort limits and technical requirements are observed.
Can Every Heat Pump Be Controlled by an EMS?
No. The available functions depend on the installed interfaces and the control commands approved by the manufacturer. An interface may provide read-only measurement data without permitting control commands or write access.