Results from a commercial-scale experimental validation of a quantitative strategy to minimize energy used in conditioning of dry air in buildings in summer with fluctuating ambient and room occupancy rate

• Published in: Chemical engineering science 2018-12, Vol.192, p.1231-1241
• Main Authors: Chu, James Y.G., Davey, Kenneth R.
• Format: Article
• Language: English
• Subjects: Conditioning of dry air in buildings; Energy strategy for air conditioning; Fr 13; Fr 13 assessment; Greenhouse gas (GHG) reduction; Probabilistic risk modelling
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2018.07.038

[Display omitted] •Conditioning of dry air in large buildings important globally.•Alternative on-only strategy practical with fluctuating ambient and occupancy rate.•Demonstrated AUD $0.75 (9%) saving per day per suite over 77 days of summer.•Concomitant 12% reduction in greenhouse gases (GHG).•Findings of immediate benefit to managers of conditioning in large buildings. Conditioning of room air in summer is important globally. Many building however do not have an energy strategy predicated on quantitative unit-operations principles. To address this, a new probabilistic model was synthesised (Chem. Eng. Sci. XXX (2017) xxx-xxx) and a quantitative on-only strategy proposed to minimize electrical energy used. Here for the first time we report an extensive commercial-scale test of this strategy over 77 contiguous days of summer (Jan. to Mar.) in a large hotel (169 rooms) in S-E Australia (latitude −37.819708, longitude 144.959936) – a hot and dry clime. Two, dimensionally-identical suites (each of two rooms), with the same fit-out and (S-E) aspect, together with identical air conditioner (8.1 kW) and ‘smart’ (National Meter Identification) meters to automatically transmit contiguous (24–7) electrical use (at 30 min intervals) (n = 3696). Each suite (10.164 × 9.675 m floor plan) was auto-set to a bulk interior air temperature of 22 °C. In one (treated) the air conditioner was operated continuously (on-only), whilst in the other (control) it was left to wide-spread industry practice of switching on whilst the room is occupied, and off, when un-occupied (on-off). The suites had standard, single-glazed pane windows or curtain wall with heat-attenuating (fabric) internal curtains. Ambient peak temperature ranged from 17.8 to 39.1 °C. There were 32 days with recorded rainfall. Overall occupancy rate of both suites was almost identical at 69.6 and 71.2% respectively for the treated and control suite. This coincided with a typical business period for the hotel. Based on independent electrical energy invoices, results showed the treated suite used less energy on 47 days (61%) of the experimental period. Greenhouse gases were reduced by 12%. Savings in electrical energy cost of AUD $0.75 per day (9%), averaged over the period, were found for the treated suite adopting the alternative on-only strategy. Experimental findings overall therefore support the energy strategy hypothesis that continuous on-only air conditioning will use less energy in summer. The hypothesis app