Marc Fountain

A study of occupant cooling by personally controlled air movement

Abstract This study addresses the effectiveness of air movement cooling, an alternative to compressor-based cooling of the air itself. Subjects in an environmental chamber were exposed to a range of warm temperatures and allowed to adjust air movement to suit their individual preferences, while answering a series of questions about their comfort. Air movement was from the subjects side, in two modes of turbulent flow. The air speeds chosen by the subjects, and their subjective responses, are evaluated in the context of existing comfort standards and prediction techniques. Choosing air speeds up to 1.4 m/s, over 80% of subjects at 1.2 met were comfortable up to 29 °C, and at 1.0 met up to 31 °C. The cooling effectiveness was significantly affected by the nature of the turbulence. A zone is proposed within which personally controlled air movement provides a likely alternative to mechanical air conditioning.

Comfort control for short-term occupancy

Abstract This paper describes the logic of a microprocessor-controlled thermostat termed ‘comfortstat’ to address the needs of temporary room occupants such as hotel guests while reducing energy consumption. The ‘comfortstat’ design grew out of a study of thermal comfort control in a luxury hotel in San Francisco, California, USA. Hotel guests frequently arrive from widely disparate climates and have high expectations of the thermal environment. Their short-term occupancy (for periods ranging from one day to several weeks) provides a unique challenge for thermal comfort control. We examined the hotel complaint log, collected detailed physical measurements of the thermal environment in typical hotel rooms, assessed the HVAC (heating, ventilating and air-conditioning) system capacity and response time, and surveyed 315 hotel guests over a five-month period. The results of this study led to the design of a thermostat control system (the ‘comfortstat’) that would solve the most serious problems. The ‘comfortstat’ integrates an infrared occupancy sensor, door switch, radiant temperature sensor, and control logic to optimize room conditions while ‘learning’ about the occupants preferred comfort zone. This paper focuses on how the joint requirements of the guests and the hotel management guided the design of the ‘comfortstat’ for increased occupant satisfaction and lower energy use in the hotel. The concepts are completely generic and could be applied to the design of comfort systems for other types of short-term occupancy. We present control logic flowcharts and typical examples of the action of the hotel ‘comfortstat’ in response to data received from the physical environment and/or human input.