Information Systems and Science for Energy

Smart Offices

Personal thermal comfort

Conventional centralized HVAC systems cannot provide office workers with personalized thermal comfort because workers in a single zone share a common air handling unit and thus a single air temperature. Moreover, they heat or cool an entire zone even if a single worker is present, which can waste energy. Both drawbacks are addressed by Personal Environmental Control (PEC) systems that modify the thermal envelope around a worker’s body to provide personalized comfort. However, most PEC systems are both expensive and difficult to deploy, making them unsuitable for large-scale deployment. In contrast, we present the design and implementation of a PEC system that is carefully designed for rapid and scalable deployment. Intuitive web-based interfaces for user controls allow our to be installed in only about 15 minutes, including user training.

 

A Hybrid Control System for Personal Thermal Comfort in Building

Most modern HVAC systems in office buildings are unable to  meet diverse comfort requirements of the occupants. Moreover, they heat or cool an entire zone even when the zone is only partially occupied, which wastes energy. Both issues can be mitigated by using personal comfort systems (PCS), which bridge the comfort gap between what is provided by a central HVAC system and the personal preferences of the occupants, and can cost-effectively provide personal comfort in partially-occupied zones. In recent work, we have proposed and deployed such a system, called SPOT.

We address the question, “How should an existing HVAC system modify its operation to benefit from the deployment of PCSs?” For example, energy use could be reduced during periods of sparse occupancy by choosing appropriate thermal set backs, with the PCS providing the additional offset in thermal comfort required for each occupant. We present the design of a PCS-aware HVAC control strategy based on Model Predictive Control (MPC) that employs a bi-linear thermal model and has two time-scales to accommodate the physical constraints that limit certain components of the central HVAC system from frequently changing their set points.

To study the effectiveness of our methodology,we use simulations to compare the energy use and comfort offered by our SPOT-aware HVAC system with that of a state-of-the-art MPC-based central HVAC system in a simplified setting. We study different room layouts and with full or partial deployment of PCSs. Numerical evaluations show that our system obtains significant savings in energy use in both summer and winter, compared both with a state-of-the-art system that does not deploy PCSs and with a similar system that deploys PCSs, but is not aware of them.

Smart Lighting

The cost of solid-state lighting has been reduced significantly over the past few years, while its efficiency keeps increasing. Compared to conventional lighting technologies, light emitting diodes also allow wider and faster control over dimming levels and colour properties of the light. Combine this with the advent of ubiquitous, cheap, and self-powered wireless sensing, and the number of applications for lighting increases dramatically. We are studying how to integrate these various technologies in order to provide more personalized and higher quality lighting comfort for occupants of indoor spaces, at the same time reducing costs of such systems.

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