Heat pumps are increasingly becoming more integral to modern living solutions due to their higher efficiency in both heating and cooling buildings. But how is this efficiency measured? Fixx has put together this guide to explore the key measure of Heat Pump Efficiency – Coefficient of Performance (CoP).
What is COP (Coefficient of Performance)?
Coefficient of performance is the measure of heat pump efficiency. It does this by assigning a whole number as a grade, which is derived from a ratio of units of heat generated versus electrical energy consumed. The higher the grade, then, the higher amount of heat generated per unit of electricity.
High CoP indicates a high level of thermal energy generation compared to energy consumed. This is used for both air-source heat pumps and ground-source heat pumps and acts as a grade of quality, but the actual process of grading each type is different.
Types of Heat Pumps
Air Source Heat Pumps
An air source heat pump works by using electrical energy to outside air through a heat exchanger. The heat is then funnelled into a compressor, which raises its temperature. The efficiency of air source heat pumps, measured by COP, varies depending on outside temperature, as well as other conditions.
In mild climates, air-source heat pumps can operate at a highly efficient level. This is because the difference between the temperature within and without is much smaller than that of colder climates. Efficiency will always be lower in colder climates due to the increased amount of energy required to heat the air.
Understanding this highlights why the climate, rather than the heat pump, tends to dictate the efficiency of the heat pump operating in a major way. Nonetheless, typically, you can expect air source heat pumps to achieve between 3 and 4 COP. Some brands of heat pumps boast higher COP due to enhanced manufacturing processes. For example, optimising thermodynamic cycles and reduction of energy loss.
Ground Source Heat Pumps
Ground source heat pumps, also known as geothermal heat pumps, draw from stable ground temperatures to extract or dissipate heat. This heat pump system can maintain higher efficiencies compared to an air source heat pump due to less fluctuation in ground temperature compared to air temperature.
A ground source heat pump is made up of pipes buried underground, forming a loop that can reject/absorb heat. You can expect COPs between 4 and 5.
Expanding on Heat Pump System Components
A heat pump system, whether it’s an air-source heat pump or ground-source heat pump, rely on the following components that influence the coefficient of performance (COP):
- Compressor – The compressor is the main component of a heat pump. It is tasked with compressing the refrigerant, which increases its temperature and pressure. This allows it to absorb heat and transport it. The best-made compressors will improve thermal energy transfer as well as reduce the electrical power supplied.
- Heat Exchanger – A heat exchanger within a pump is the component that absorbs heat from a cold source (either the outside temperature or the ground temperature). It then releases it into a hot reservoir, such as a room or water heating system. Nonetheless, they are responsible for the overall heat energy output and overall system performance.
- Refrigerants – Your choice of refrigerant directly affects heat pump efficiency in terms of heat transfer capabilities and more. Higher heat capacities within a refrigerant can achieve higher heat energy transfer rates. Eco-friendly options are also available, lowering carbon footprint and aligning with renewable energy sources for a sustainable heating season.
Overall, the quality of each component reflects the quality of the COP.
Achieving Maximum Theoretical Efficiency via Seasonal Adjustment
Achieving optimal efficiency through seasonal coefficient of performance is a fairly common tactic. Fluctuations in outside temperature and ground temperature are common as seasons change, and implementing changes during these periods will allow you to account for them, allowing for better rates of COP.
Seasonal Efficacy Factors
For an air source heat pump, you can expect efficiency to drop when the outside temperature does. Due to this, the system has to work harder to extract heat from the cold air.
For a ground source heat pump, the largely consistent ground temperature staves off a lot of the temperature shift. This means that whilst the heat pump will experience slightly lower efficiency, the difference is negligible.
Optimising System Performance
Aside from simple maintenance, there is another easy way to ensure your system works optimally. Many modern heat pumps come with SMART technology, allowing you to monitor and make remote changes to your system.
The following are some examples of Smart Technology that directly affect heat pump COP.
- Advanced Thermostats – Advanced thermostats are key in the optimisation of heat pump performance. They help maintain an optimal balance between thermal energy use and comfort through their ability to alter temperature settings.
- IoT Integration for Heat Pumps – Through connection to a heat pump to IoT devices, you enable precise management of your heat output. They monitor changes to external and internal conditions, prompting adjustments of a heat pump’s settings to improve performance and energy usage in response.
- Weather Responsive Adjustments – Integrating weather forecasting technology can allow heat pump systems to make automatic cooling and heating adjustments to anticipate changes of outside temperature.
- Energy Usage Insights – Smart systems provide analytics on energy consumption, showing trends of electrical energy used and the ratio of heat energy produced.
Conclusion
Overall, the coefficient of performance is a measure by which you can judge the overall efficiency of your heat pump, as well as its specific usage. Through SMART technology, the ratio can be tweaked a fair bit.
FAQs
Does insulation increase my heat pump COP?
Yes. Insulation has been the main method of minimising heat loss from a building in winter since the government began to push their green energy measures. They give the following effects on the coefficient of performance (COP):
- Reduced Workload – Insulation keeps heat from leaving or entering the walls. This means your heat pump will not have to tax itself as much as it would otherwise.
- Energy Savings – Lower energy usage contributes to higher COP. Since less energy has to be generated due to the low heat loss, less electrical energy must be used to generate heat from the building.
- High Lifespan – A heat pump can operate within safe and optimal parameters in a well-insulated building, ensuring minimal degradation.
- Seasonal COP – Insulation works both ways – it keeps heat in and out. This means that extreme temperatures within summer and winter will have much less effect on the heat pump COP than they would in a building without insulation.
How does defrost mode affect COP?
Defrost mode is a function that serves a critical purpose within heat pumps, particularly in cold temperatures. It exists mainly due to ice being able to build up on the outdoor heat exchanger.
- Temporary Reduction in Efficiency – COP lowers when the heat pump switches into defrost mode. It uses electrical energy to generate heat but doesn’t contribute it to the house. Instead, it heats the area in which the ice forms, thereby melting the ice.
- Increased Demand – The demand for switching to and from defrost mode will place stress on the heat pump compressor. This can lead to increased wear and potential inefficiencies.
Defrost cycles are almost always required at some point in the year, but how often and the duration of the cycles depend on the external temperature and humidity levels.
What is the difference between COP and SEER?
The difference between COP and SEER lies in their focus and usage.
- Focus – COP is the measure of the efficacy of a heat pump or air conditioner. A high COP indicates that it is able to deliver more heating or cooling, compared to the energy it otherwise consumes. SEER, on the other hand, is the measure of an air conditioning unit and heat pump’s cooling capabilities. It is calculated as the ratio of total cooling provided versus electrical energy.
- Use – COP is used to evaluate the efficiency of a heat pump when operating heat. It doesn’t account for wider factors, such as variations in weather and temperature. SEER, on the other hand, provides a broader measure. It covers varying conditions of a cooling season which makes it useful for consumers to compare their efficiency through other climates.
- Weather Conditions – COP varies significantly based on the temperature the system is operating at. As external temps decrease, so too does the COP, because the system has to work harder. But SEER is more generalised, displaying averages of performance over a range of temps and operational conditions.