Energy efficient indoor climate control - A practical approach for enhanced implementability

Doctoral thesis, 2014

This work deals with energy efficient indoor climate control in office buildings, with an emphasis on implementability. More specifically, the aim is to suggest and evaluate improvements to building automation systems that are sufficiently simple and efficient to be realistic alternatives to commonly-used systems. The approach is focused on a technology that generates control signals by anticipating the influence of measured indoor climate disturbances, and this principle was evaluated for automating heating, cooling and ventilation on central as well as local building levels. The work was conducted through a combination of simulations in Simulink® and experiments in a laboratory environment. Each part has its own purpose in the whole, and the procedure follows a systematic and holistic structure. While some studies deal with technologies for measuring disturbances using few standard-type sensors, other focus on finding relevant ways for transforming this information into control signals without involving extensive algorithms or many parameters. Altogether, most practical aspects and relevant applications are addressed in order to provide an as complete picture of the research topic as possible. The general methodology was to re-create typical working days through office-like activities in office-like environments, and to repeat the same period with a suggested and conventional indoor climate control system. As both control systems were constrained to fulfill a desirable indoor climate, their performances were measured by the associated energy usages of the heating, ventilation and air-conditioning (HVAC) system. Furthermore, the influences of several conditions such as building structure, office room type, working activity and ambient climate are considered in the work. The investigated variants appear in pairs and were selected to cover most relevant configurations regarding some specific aspect. Using this approach, the aim is to spread the investigation so that most real scenarios can be found within the range of results. The combined results show that realizable technologies are sufficient to reduce the HVAC energy usage considerably, at the same time as a desirable indoor climate is achieved. It was moreover found that the largest potential benefits are allocated to ventilation system automation. Even a simple supply air temperature control strategy has the ability of reducing total energy usage with up to 30 % compared to a conventional outdoor temperature-compensated approach. Further, a single parameter controller for ventilation rate automation on room level can result in that up to 50 % less air is required for maintaining a desirable indoor climate.