Development and HIL Validation of a Low-Cost Two-Level Control Strategy for HVAC Systems

Jesús Clavijo-Camacho(1), Álvaro de la Cruz Álamo(1), Gabriel Gómez-Ruiz(2), Cristian Díaz-Martín(2), Juan P. Torreglosa(1), Reyes Sánchez-Herrera(1) 1. Department of Electrical, Thermal, Design and Projects Engineering, University of Huelva 2. Department of Electronic Engineering, Computer Systems and Automation, University of Huelva Higher Technical School of Engineering, Campus El Carmen, Avda. de las Fuerzas Armadas, Huelva, Spain 2026-06-27

Abstract

Buildings account for a substantial fraction of globalfinal energy consumption, with HVAC systems representing their dominant load. The progressive deployment of dynamic electricity pricing creates a strong economic incentive to shift thermal loads toward low-price periods; however, implementing optimization frameworks on low-cost embedded hardware remains largely unvalidated experimentally. This paper presents the design and 24-hour experimental validation of a two-layer hierarchical control architecture for HVAC systems targeted at resource-constrained embedded microcontrollers. The upper layer consists of a rolling-horizon dynamic programming optimizer computing a global binary on/off schedule over a 24-hour planning horizon, while the lower layer implements a real-time safety controller enforcing hard thermal comfort constraints at every control cycle. The architecture is validated through a hardware-in-the-loop platform, in which the microcontroller exchanges signals with a first-order RC building thermal model on a real-time emulation target. Results demonstrate a total electricity cost reduction of 19.71% relative to a conventional hysteresis thermostat, with indoor temperatures maintained within the prescribed comfort band for 98.8% of the trial duration, confirming that cost-optimal thermal management is achievable on severely resource-constrained hardware.

Key words: Hardware-in-the-Loop, HVAC Control, Dynamic Programming, Embedded Microcontroller.

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