Impact of Weather Uncertainties on Active Building Envelopes (ABE): An Emerging Thermal Control Technology

In this paper, we investigate the impact of weather uncertainties on the optimal design of Active Building Envelopes (ABE). Recently, ABE systems have been proposed as a technology that uses solar energy to maintain a comfortable indoor environment. ABE systems are multidisciplinary in nature, where solar radiation energy is converted into electrical energy by means of a photovoltaic unit (PV unit) that powers a thermoelectric heat pump unit (TE unit). Our earlier work focused on a deterministic optimization of ABE systems. In this paper, we account for critical uncertainties in the outside temperature and solar radiation. Two conflicting issues of interest are: (1) objective function minimization, and (2) minimization of constraint violation under uncertainty. The main design constraint in ABE systems is to ensure that (i) the heat absorbing capacity of the TE unit and (ii) the amount of heat entering the house (also called cooling load) are as close to each other as possible under uncertainty. Also, we must ensure that the underlying physics of the interacting subsystems is not violated. The above requirements, which are imposed as equality constraints in the deterministic problem, need to be appropriately formulated to ensure feasibility under uncertain conditions. In this paper, we use an equality constraint formulation to address the above issues, which results in a multiobjective optimization problem. This yields several designs of the ABE system, each offering a different tradeoff between the objective function value and the ability to match the heat absorbing capacity with the cooling load. As we show in the paper, this uncertainty based design approach gives the designer a realistic understanding of the tradeoff involved in selecting an appropriate design of ABE systems.