Earth Notes: General Bibliography (reguis2021challenges)

• [reguis2021challenges] Reguis, Antoine and Vand, Behrang and Currie, John Challenges for the Transition to Low-Temperature Heat in the UK: A Review (accessed 2023-03-01), 2021, Energies, volume 14, report/number 21, ISSN 1996-1073, doi:10.3390/en14217181 (article) (BibTeX).
  abstract

  To reach net-zero emissions by 2050, buildings in the UK need to replace natural gas boilers with heat pumps and district heating. These technologies are efficient at reduced flow/return temperatures, typically 55/2
  5~nbsp;°C, while traditional heating systems are designed for 82/7
  1~nbsp;°C, and an oversized heating system can help this temperature transition. This paper reviews how heating systems have been sized over time in the UK and the degree of oversizing in existing buildings. It also reviews if lessons from other countries can be applied to the UK's building stock. The results show that methods to size a heating system have not changed over time, but the modern level of comfort, the retrofit history of buildings and the use of margin lead to the heating system being generally oversized. It is not possible to identify a specific trend by age, use or archetype. Buildings in Scandinavia have a nascent readiness for low-temperature heat as they can use it for most of the year without retrofit. Limitations come primarily from the faults and malfunctions of such systems. In the UK, it is estimated that 10% of domestic buildings would be ready for a supply temperature of 5
  5~nbsp;°C during extreme external conditions and more buildings at part-load operation. Lessons from Scandinavia should be considered with caution. The building stock in the UK generally underperforms compared to other EU buildings, with heating systems in the UK operating at higher temperatures and with night set-back; the importance of providing a low-return temperature does not exist in the UK despite being beneficial for condensing boiler operation. Sweden and Denmark started to develop district heating technologies with limitations to supply temperatures some 40 years ago whereas the UK is only just starting to consider similar measures in 2021. Recommendations for policy makers in this context have been drawn from this review in the conclusions.
  note

  [Quote: "This is particularly true for non-domestic buildings, as they use weather-compensation control to reduce flow temperature during mild weather, combined with TRVs to trim local temperatures. Both weather-compensation and TRVs are mandatory equipment in non-domestic buildings. In domestic buildings, weather-compensated controls were not recommended in 2008, as they were deemed not to be cost effective, but TRV's have become mandatory since the 1990s. In 2017, weather-compensated controls represented only a 2% share of the domestic market, and in domestic buildings, it is common practice that the flow temperature of the heating circuit is set manually by the occupant with the adjustment of a dial on the boiler." Quote: "A well-balanced hydraulic heating system provides a uniform temperature drop across all radiators. This temperature drop, at nominal conditions, is expected to be
  5~nbsp;°C, 10–1
  2~nbsp;°C or 2
  0~nbsp;°C depending on the boiler type or the system type; typically, it is
  5~nbsp;°C for systems where a pump is installed, 10–1
  2~nbsp;°C for systems with gravity flow and 2
  0~nbsp;°C when there a condensing boiler is installed or higher with a connection to district heating. Most recommendations from radiator manufacturers are 10–1
  2~nbsp;°C." Quote: "Achieving net-zero emissions from the building sector in the UK involves replacing all gas boilers with new technologies such as heat pumps or low-temperature district heating commonly called fourth generation district heating (4GDH)." Quote: "The current radiator connection type BBOE [Both Bottom Opposite Ends] should not be allowed as this reduces the output capacity of radiators by 5 to 15%, limiting the ability to provide a low return temperature. "]