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Test methods for heat pumps
(2020)
In this study, the test method EN 14825 for testing heat pumps is validated by verifying the sensitivity of the seasonal space heating energy efficiency ηs,(declared on the energy Efficiency label) in relation to the nominal heating capacity Pdesign. Therefore, the two major parts of the test method, the measurement part and the calculation part, were investigated. The calculation part was subjected to a sensitivity analysis in order to identify the properties of a heat pump which have a strong influence on ηs. The analysis revealed that the energy consumption in Special operating states, the duration in active-mode and seasonal performance values in active-mode (SCOPon) significantly affect the sensitivity of ηs. Especially short operating times, in which the heat pump is in active-mode, lead to large changes in ηs with varying Pdesign. In addition, the range of power of Pdesign turned out to have an increasing impact on ηs with decreasing Pdesign. For Pdesign values ≤10 kW, the sensitivity of ηs increases tremendously. Especially the determination of the ηs for devices with short operating times in active-mode (1400 h) and low values for Pdesign (≤10 kW)cannot be reproduced anymore.
In this study, the test method EN 14825 for testing heat pumps is validated by verifying the sensitivity of the seasonal space heating energy efficiency ηs, (declared on the energy efficiency label) in relation to the nominal heating capacity Pdesign. Therefore, the two major parts of the test method, the measurement part and the calculation part, were investigated. The calculation part was subjected to a sensitivity analysis in order to identify the properties of a heat pump which have a strong influence on ηs. The analysis revealed that the energy consumption in special operating states, the duration in activemode and seasonal performance values in active-mode (SCOPon) significantly affect the sensitivity of ηs. Especially short operating times, in which the heat pump is in active-mode, lead to large changes in ηs with varying Pdesign. In addition, the range of power of Pdesign turned out to have an increasing Impact on ηs with decreasing Pdesign. For Pdesign values ≤10 kW, the sensitivity of ηs increases tremendously.
Especially the determination of the ηs for devices with short operating times in active-mode (1400 h) and low values for Pdesign (≤10 kW) cannot be reproduced anymore.
In order to increase the total amount of energy savings to be reached in 2020 and 2050 the German government launched a number of initiatives. One of the associated projects aims to support market surveillance authorities in the field of Ecodesign and Energy Labelling, thereby increasing confidence in these instruments. The surveillance of heating appliances is of great importance as the energy consumed by space heaters accounts for a significant share of the total energy demand in the European Union. In this study heat pumps are analyzed as a high efficiency technology and prospective candidate for large energy savings. It is focused on both validating the current measurement standards for heat pumps and further developing these methods for the benefit of market surveillance authorities.
The test method standards, EN 14511 and EN 14825, for testing heat pumps regarding their performance and energy efficiency are validated by conducting round robin tests in independent and accredited test laboratories. Based on these tests the reproducibility and repeatability of the standardized test methods and the laboratories in Europe are assessed.
Identifying deficiencies in the methods is a fundamental step towards a sustained improvement process. Optimization proposals will be developed based on these fundamental investigations and brought to the attention of standardization bodies.
It was figured out that the currently used test methods exhibit high complexity, high financial effort and reveal significant deviations of testing results depending on whether they were determined under laboratory or field test conditions.
New testing and calculation methodologies are developed to simplify the process with the aim to increase the accuracy and affordability of the energy efficiency testing of heat pumps.
Minimum energy performance standards and labels are commonly used tools to reduce the household energy use thus mitigating greenhouse gas emissions. However, the technical foundation for minimum energy performance standards and labels are test procedures for rating and testing of appliances. To de- termine the seasonal cooling performance of air conditioners, the current test standards require fixing of the compressor speed of the units to achieve steady-state conditions; this way of operation, how- ever, differs from real-life use. To make the seasonal cooling performance testing better reflect the real use conditions, this study proposes a compensation method which can be conducted independently from manufacturer data and still allows modulation of the tested units. Our results show that the tested units behave differently under part-load conditions, which results in a lower energy efficiency rating for some of the tested devices.
To determine the seasonal performance of heat pumps for energy labelling this study proposes a two-point-method that could conceivably be an alternative to the European standard EN 14825 and similar test standards such as ISO 13256. Heat pumps were tested in line with the EN 14825. The reduction of measurement points, from between five to seven (EN 14825) to only two (two-point-method), leads to 60 % savings in cost and time. It is shown that the shortened method can be used to determine the seasonal energy efficiency of heat pumps with the same degree of precision compared to EN 14825.
In this study, the test method EN 14825 for testing air conditioners is validated by verifying the sensitivity of the seasonal energy efficiency ratio SEER (declared on the energy efficiency label) in relation to the nominal cooling capacity Pdesign. Therefore, the two major parts of the test method, the measurement part and the calculation part, were investigated. Measurements were conducted on several single-split units. The calculation part was subjected to a sensitivity analysis in order to identify the properties of an air conditioner which have a strong influence on the SEER. The analysis revealed that the measurement procedure delivers reproducible results. However, the energy consumption in special operating states, the duration in active-mode and seasonal performance values in active mode (SEERon) significantly affect the sensitivity of the SEER. Especially assumption of short operating times for a cooling active mode leads to large changes in the SEER with varying Pdesign. In addition, the range of power of Pdesign turned out to have an increasing impact on the SEER with decreasing Pdesign. For Pdesign values ≤10 kW, which is the most popular type of ACs in the EU, the sensitivity of the SEER increases tremendously.
Especially the determination of the SEER for devices with short operating times in cooling active-mode (350 h) and low values for Pdesign (≤10 kW) cannot be reproduced anymore. In consequence, manufacturer could use the sensitivity of the SEER on Pdesign to artificially “increase” the energy efficiency of their air conditioner for the Energy label about 10 %.