In-situ comparison between the energy performance of an in-slab gas heating system and a split system air conditioning in classrooms

• Published in: Energy and buildings 2023-01, Vol.279, p.112713, Article 112713
• Main Authors: Kokogiannakis, Georgios, Daly, Daniel, McDowell, Clayton, Roth, James, Tibbs, Michael, Cooper, Paul
• Format: Article
• Language: English
• Subjects: Gas in-slab heating; In-situ heating systems comparison; Opening windows energy burden; School energy use; Split system Air-Conditioner
• ISSN: 0378-7788
• DOI: 10.1016/j.enbuild.2022.112713

•Sub-metered energy use of an in-slab gas hydronic heating system was compared with the energy use of a newly installed split system air conditioner.•Preliminary comparison was also undertaken to quantify the heating penalty for the existing gas-fuelled hydronic heating systems when windows remain open (e.g. to comply with COVID-19 guidelines in schools).•For three days of unoccupied tests, the gas hydronic system used 41.5 kWh while the AC split system used 7.2 kWh.•For selected days of the occupied period when both systems were used for long periods, the AC split system used approximately 4 to 7 times less metered energy than the in-slab gas hydronic system.•The in-slab hydronic system used 66.8 kWh of metered energy in 3-days as opposed to 25 kWh for the windows open and closed cases respectively. Sub-metered energy use of an in-slab gas hydronic heating system and a newly installed split system air conditioner in thermodynamically-equivalent classrooms are compared during unoccupied (with artificially imposed internal heat gains) and occupied periods. A preliminary comparison is also undertaken to quantify the heating penalty for the existing gas-fuelled hydronic heating systems when windows remain open (e.g. to comply with COVID-19 guidelines in schools) against the energy needed for heating by the same system in a control classroom with windows closed. The performance evaluation of the heating systems during three unoccupied days where internal heat gains were artificially imposed demonstrated that the gas hydronic system used 41.5 kWh of metered energy while the AC split system used 7.2 kWh, with the AC split system being able to maintain the internal conditions above the set point by operating for approximately-one third of the time the hydronic system was operating. Occupied tests confirmed the observations of the unoccupied tests of equivalent operation. Over a period of 2 occupied winter weeks, the in-slab gas hydronic heating system used 274.6 kWh of metered energy and operated for 35¼ hrs, while the AC split system used 34.7 kWh and operated for 22¼ hrs, albeit on some occasions the occupants in the AC split system’s classroom chose not to turn on the system. After selecting days from this occupied period when both systems were used for long periods, it was observed that the AC split system used approximately 4 to 7 times less metered energy than the in-slab gas hydronic system (or 3.3 times in terms of primary energy when worse-case primary e