Seasonal Performance Factor SPF
Seasonal performance factor (SPF) is a: ‘…measure of the operating performance of an electric heat pump over the season. It is the ratio of the heat delivered to the total electrical energy supplied over the season, but there are up to seven different ways to draw the system boundaries. For example, SPFH2 excludes auxiliary resistance heating while SPFH4 includes it – making a large difference.’
Ref Non-domestic Building Services Compliance Guide For Scotland, 2015 Edition v1.1, published by the Scottish Government, Building Standards Division in April 2018.
In their "Domestic Annual Heat Pump System Efficiency (DAHPSE) - Estimator - BETA" published by the BRE they describe the need for Seasonal performance factor (SPF) and the reason for its development as an alternative to compliment the Coefficient of Performance (COP) and Seasonal Coefficient of Performance (SCOP).
"The COP is an instantaneous measurement and reflects the sink and source temperatures at a particular moment, such as during a test. In practice, it is of limited use for evaluating or comparing performance throughout a year, where source temperatures (such as outside air) will change significantly. Water flow (sink) temperatures through the heat emitters may also change throughout the year, for example due to weather compensation controls.
In order to estimate annual performance, the European Union’s Ecodesign regulations utilise a test and calculation standard (EN14825:2016) at a wide range of temperature conditions. These are used to calculate a Seasonal Coefficient of Performance (SCOP) for a heat pump, which is used to derive an energy label class (A++ to G) for comparison purposes.
Unfortunately, the SCOP estimation of performance misses a number of important issues that may affect the performance of a heat pump when installed in homes. These include:
- Heat loss of the actual dwelling in which the heat pump is installed is ignored
- It uses average European climate data
- Hot water heating operation is ignored, including its impact on space heating operation
- Heating hours
- For inverter (modulating) heat pumps, the minimum heat output is not defined, meaning some heat pumps may cycle on/off more than others at identical temperature conditions
- Weather compensation is always assumed to be present
The Building Research Establishment has developed an annual efficiency calculation method that utilises the engineering standard EN15316-4-2:2017 to address these issues. Annual efficiency (or SPF) can be defined in a number of different ways, and can include or exclude electrical energy needed for different heat pump system components. The annual efficiency estimates provided by this website include all auxiliary components necessary for operation, including back-up direct-electric heaters and circulation pump. This type of annual efficiency (or SPF) is often known as SEPEMO (SEasonal PErformance factor and MOnitoring (SEPEMO) system boundaries.) “SPF_H4”. The Seasonal Performance Factor (SPF) is the same as annual efficiency, but is not multiplied by 100."
The UCL Energy Futures Lab Briefing Paper "Accelerating the transition to heat pumps: measuring real-world performance and enabling peer-to-peer learning" by Dr Richard Carmichael published September 2022 describes SEPEMO Seasonal Performance factor and monitoring for heat pump systems in the building sector, as a project funded by Intelligent EnergyEurope (IEE) Programme financed by the European Commission, Contract No. IEE/08/776/SI2.529222, which defined four Seasonal performance factors (SPFs) 1-4 according to the boundaries of the system they are concerned with, which are explained by the above image and commentary below:
"SPFH1 This system contains only the heat pump unit. SPFH1 evaluates the performance of the refrigeration cycle. The system boundaries are similar to the COP defined in EN 14511, except that the standard takes, in addition, a small part of the pump consumption to overcome head losses in the liquid heat exchangers, and most part of the fan electricity consumption."
"SPFH2 This system contains the heat pump unit and the equipment to make the source energy available for the heat pump. SPFH2 evaluates the performance of the heat pump including heat source. This figure corresponds roughly to the SCOPNET, as defined in prEN 14825, excluding most of the heat source consumption."
"SPFH3 This system contains the heat pump unit, the equipment to make the source energy available and the back-up heater. SPFH3 represents the heat pump system and thereby it can be used for comparison to conventional heating systems(e.g. oil, gas, etc.). This system boundary is similar to the SPF in VDI 4650-1, EN 15316-4-2 and the SCOPON in prEN 14825, excluding most of the heat source consumption for most cases. For monovalent4 heat pump systems SPFH3 and SPFH2 are identical."
"SPFH4 This system contains the heat pump unit, the equipment to make the source energy available, the back-up heaterand all auxiliary drives, including the auxiliary consumption of the heat sink system. SPFH4 represents the heat pumpheating system including all auxiliary drives which are installed in the heating system."
See also: Coefficient of performance and Seasonal Coefficient of Performance.
[edit] Related articles on Designing Buildings
- Absorption heat pump.
- Air source heat pumps.
- Coefficient of performance.
- Combined heat and power CHP.
- Domestic heat pumps and the electricity supply system.
- Earth-to-air heat exchangers.
- Exhaust air heat pump.
- Ground source heat pumps.
- Heat exchanger.
- Heat pump.
- Heat recovery.
- Residential heat pump installations: the role of vocational education and training.
- Solar thermal heating.
- Types of domestic boiler.
- Water source heat pumps.
[edit] External links
https://tools.bregroup.com/heatpumpefficiency/hot-water-consumption
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