Decentralized temperature control via HVAC systems in energy efficient buildings: An approximate solution procedure

Abstract

In this paper, we design real-time decentralized and distributed control schemes for Heating Ventilation and Air Conditioning (HVAC) systems in energy efficient buildings. The control schemes balance user comfort and energy saving, and are implemented without measuring or predicting exogenous disturbances. Firstly, we introduce a thermal dynamic model of building systems and formulate a steady-state resource allocation problem, which aims to minimize the aggregate deviation between zone temperatures and their set points, as well as the building energy consumption, subject to practical operating constraints, by adjusting zone flow rates. Because this problem is nonconvex, we propose two methods to (approximately) solve it and to design the real-time control. In the first method, we present a convex relaxation approach to solve an approximate version of the steady-state optimization problem, where the heat transfer between neighboring zones is ignored. We prove the tightness of the relaxation and develop a real-time decentralized algorithm to regulate the zone flow rate. In the second method, we introduce a mild assumption under which the original optimization problem becomes convex, and then a real-time distributed algorithm is developed to regulate the zone flow rate. In both cases, the thermal dynamics can be driven to equilibria which are optimal solutions to those associated steady-state optimization problems. Finally, numerical examples are provided to illustrate the effectiveness of the designed control schemes.

HVAC Energy Cost Optimization for a Multizone Building via a Decentralized Approach

“…To cope with the difficulties and challenges to solve the problem, a hierarchical distributed method was proposed, in which the original optimization problem was divided into three-level subproblems and each corresponds to a part of the global objective function. Different from those mentioned above, [28], [29] studied the steady-state temperature regulation of the HVAC system for an energy-efficient building via a decentralized primal-dual gradient method while relaxing the global objective function. The problem was formulated as a static optimization problem without considering the thermal dynamics and the thermal coupling among the neighboring zones.…”

“…This damper can regulate air flow rate supplied to the zone, while the heating coil can reheat the supply air before supplied to the zone if necessary (in this paper, the heating coil of the local VAV box is not discussed). More details regarding HVAC systems for multi-zone buildings can refer to [10], [29].…”

“…In the two-zone case study, there exist heat transfer between the two zones. And the initial zone temperature is set as [26,28] • C, respectively. The outside air temperature usually fluctuates over the time as shown in Fig.…”

“…In this case study, we assume there exist heat transfer between any two of the zones. Without loss of generality, the initial temperature for the I = 5 zones are set as [26,28,28,27,27] • C, respectively. Similarly, the thermal load curves for the I = 5 zones are randomly generated according to the uniform distribution, which are shown in Fig.…”

Evaluation of a cost-responsive supply air temperature reset strategy in an office building

“…Though a valid approach for SAT reset (e.g. [26][27][28]), it requires expertise that is not common in the HVAC controls industry, and it requires additional hardware as it is too complex to implement inside the hardware and software environment of a building management system controller. Furthermore, many approaches require long training or parameter initialization periods.…”