Research Overview: Building Control

The trouble with weather forecasting is that it's right too often for us to ignore it and wrong too often for us to rely on it.
- Patrick Young

The most critical challenge facing society today is climate change. There are many causal factors for the current state of affairs, but it's fair to say that a massive reduction in global energy usage will be central to any successful mitigation strategy. One of the largest uses for energy is the maintenance of internal environments in buildings; accounting for 2,589 Mtoe (mega tonnes oil equivalents) globally, which is approximately 40% of all energy used. Other large consumers can be clustered under the headings 'industry' and transport, which take approximately 30% each. [Ref: International Energy Agency `Energy efficiency requirements in building codes, energy efficiency policies for new buildings']

Acting quickly to reduce energy consumption in buildings is particularly critical when one compares the half-lives of these three main energy consuming sectors. An average car will only last about 5-10 years before being replaced, which means that we only have to live with a gas-guzzler built today for a few years before it can be replaced with something better. However, a building constructed today will be with us for 50-100 years, motivating two important directions of research into building technology: improving current construction techniques and reducing the energy usage of existing buildings. Our work here is primarily focused on the latter of these activities.

There are two principle disturbances acting on buildings. The first are the people occupying the building, who generate heat, CO2 and set demands for temperature and air quality. The second is the external environment - the weather. The overarching idea for this project is to combine some foreknowledge of these disturbances into the design of the controller. This knowledge comes in the form of weather predictions from our partners at MeteoSwiss and is readily incorporated into the control action in a model-predictive control configuration.

In this project we study both practical and theoretical questions relating to building control. On the theoretical side we examine the effect of uncertainty in model predictive control. Specifically, we are looking to incorporate our knowledge of disturbance distributions into the control action and hence are studying various forms of stochastic model predictive control. Practically, we apply these (and other) techniques to accurate building and climatological models tuned to various parts of Europe in order to gauge the impact of different construction and control methods in real environments. The accuracy and efficacy of these techniques requires a very broad range of skills, which is why our work is carried out as part of the large multidisciplinary OptiControl project.

Publications

F. Oldewurtel, C.N. Jones, M. Morari, A Tractable Approximation of Chance Constrained Stochastic MPC based on Affine Disturbance Feedback, Conference on Decision and Control, 2008

This paper deals with model predictive control of uncertain linear discrete-time systems with polytopic constraints on the input and chance constraints on the states. Recently, it has been shown that when having merely polytopic constraints and bounded disturbances, the conservatism of a robust solution can be reduced by applying a closed-loop prediction formulation. We show that in the presence of chance constraints and stochastic disturbances, this closed-loop formulation can be used together with a tractable approximation of the chance constraints to further increase the performance while giving probabilistic guarantees on the constraints.

Accepted for publication. Details will be updated when final version is available.

Talks

D. Gyalistras, M. Gwerder, V. Dorer, T. Frank, C. Gähler, C.N. Jones, B. Lehmann, M. Morari, F. Oldewurtel, F. Schubiger, V. Stauch, P. Steiner, J. Tödtli, OptiControl - Verwendung von Wetter- und Anwesenheits-Vorhersagen für die optimale Gebäudeklimaregelung., Poster presentation, «swisselectric research award 2007», Technopark Zurich, Switzerland., 4. Sep. 2007

More details available here

Further reading

• IfA building control group webpage
• OptiControl group
• International Energy Agency
  In particular, the policy report on "Energy Efficiency Requirements in Building Codes" and their pages on energy efficiency in general.