Implementation of Desk Fans in Open Offices in Brazil: Proposition for Optimizing Thermal Comfort and Energy Consumption

Maíra Afonso de André
Prof. Roberto Lamberts, Dr

The global warming scenario drives nations to adopt strategies to reduce greenhouse gas emissions and electricity demand. Buildings in Brazil account for more than 50% of the country's electricity consumption, and cooling is one of the main end-uses in commercial buildings. One way to reduce this consumption is to extend the setpoint temperature of cooling systems and use personal conditioning systems (PCS) to maintain occupants’ thermal comfort. In Brazil, the prevalence of high temperatures and preference for high air speed indicate that desk fans would be a good fit for office spaces. Despite numerous research in recent years, there is still a lot to be understood about the best way to implement PCS in buildings. One of the biggest challenges is defining setpoint temperature limits for achieving both comfort and energy savings. Considering these possibilities and issues, this thesis aims to evaluate the feasibility and best practice of applying desk fans into shared workspaces in Brazil. The thesis is structured in five articles: (1) literature review; (2) assessment of fans for equipment selection; (3) potential expansion of setpoint temperature for Brazilian climates with the use of desk fans; (4) current operation procedures in Brazil and a comparison to other countries; (5) guidelines for implementation based on a field study. The first article helped to understand the gaps in the topic and to define the methods of the thesis and the following papers. The second article is based on a controlled study with 40 people assessing 4 desk fans. Air flow sensation, the possibility of adjustment, noise, and cost are the most important aspects for selecting a device. Users preferred the evaporative cooling fan, however, considered its cost-benefit not worth it. Therefore, two other fans, with similar rates were selected for the field application presented in paper 5. The third article presents, through computer simulation, the potential extension of setpoint temperature when desk fans are associated with mixed-mode operation in offices in Brazilian cities. Results show that fans can expand up to 30 % comfortable occupancy hours in open offices and increase energy consumption by up to 1.5 %. The simulation and prediction models indicate 28 °C setpoint is applicable for Brasilia, Manaus, and Fortaleza, and 30 °C for Florianopolis with a low risk of overheating. However, the interviews with building operators carried out for paper 4 indicate the most common setpoint in Brazil is 23 °C in office spaces. This temperature is the most common also in Canada, while in Singapore and Italy, which have warmer summers, 26 °C is the main cooling setpoint. Therefore, there was not found a clear relation between setpoints and climate, which indicates the adaptive concept not to be applicable to setpoint selection. The fifth paper was based on a field implementation of desk fans with setpoint temperature increment from 23 °C up to 27 °C in Florianopolis. Occupants’ expectations was found to have a great impact on the applicable setpoint limits. Occupants felt more pleased with fans changing indoor temperature from 24 °C to 25 °C. However, many limitations hindered the experiment results and gradual changes are suggested for future implementation, associated with engaging operators and occupants, and monitoring thermal perception with timely surveys.

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