HVAC Systems Applied in University Buildings with Control Based on PMV and aPMV Indexes

António Ruano,António Sousa,Eusébio Conceição,João Gomes

doi:10.3390/inventions4010003

António Ruano, António Sousa + Show 2 more

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https://doi.org/10.3390/inventions4010003

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Abstract

In this work, HVAC (Heating, Ventilation and Air Conditioning) systems applied in university buildings with control based on PMV (Predicted Mean Vote) and aPMV (adaptive Predicted Mean Vote) indexes are discussed. The building’s thermal behavior with complex topology, in transient thermal conditions, for summer and winter conditions is simulated by software. The university building is divided into 124 spaces, on two levels with an area of 5931 m2, and is composed of 201 transparent surfaces and 1740 opaque surfaces. There are 86 compartments equipped with HVAC systems. The simulation considers the actual occupation and ventilation cycles, the external environmental variables, the internal HVAC system and the occupants’ and building’s characteristics. In this work, a new HVAC control system, designed to simultaneously obtain better occupants’ thermal comfort levels according to category C of ISO 7730 with less energy consumption, is presented. This new HVAC system with aPMV index control is numerically implemented, and its performance is compared with the performance of the same HVAC system with the usual PMV index control. Both HVAC control systems turn on only when the PMV index or the aPMV index reaches values below −0.7, in winter conditions, and when the PMV index or the aPMV index reaches values above +0.7, in summer conditions. In accordance with the results obtained, the HVAC system guarantees negative PMV and aPMV indexes in winter conditions and positive PMV and aPMV indexes in summer conditions. The energy consumption level is higher in winter conditions than in summer conditions for compartments with shading, and it is lower in winter conditions than in summer conditions for compartments exposed to direct solar radiation. The consumption level is higher using the PMV control than with the aPMV control. Air temperature, in accordance with Portuguese standards, is higher than 20 °C in winter conditions and lower than 27 °C in summer conditions. In Mediterranean climates, the HVAC systems with aPMV control provide better occupants’ thermal comfort levels and less energy consumption than the HVAC system with PMV control.

Highlights

Large amounts of carbon dioxide are emitted to the atmosphere by transportation systems, energy production, industry, and buildings
The results showed that thermal comfort for the user and building energy efficiency are achieved with excellent control performance and robustness
The aim of this work is to develop a new type of HVAC control system based on Adaptive Predicted Mean Vote (aPMV) index and evaluate its performance numerically, by comparing it with the more usual HVAC control system based on Predicted Mean Vote (PMV) index

Summary

Introduction

Large amounts of carbon dioxide are emitted to the atmosphere by transportation systems, energy production, industry, and buildings. In buildings, Heating, Ventilation and Air Conditioning (HVAC) is the main energy-consuming equipment [1]. Energy efficiency can be improved by reducing the energy consumption of already installed equipment, making its use more rational and achieving the thermal comfort for the occupants of the air-conditioned spaces. HVAC energy demand is directly related to the indoor temperature setpoint, air infiltration, incident solar radiation, window type, window-wall ratio, internal loads, building type and climate [2]. An adequate evaluation of the thermal performance of the building envelope is needed [3,4], because it will influence the thermal load of the air-conditioned compartments and, the HVAC performance. The building envelope data (type of elements and their dimensions) is an important step in a building thermal behavior numerical simulation [5]. In this type of simulation, it is important to define the interior and external walls, floors, ceilings, transparent surfaces and other interior details characteristics, and the thermal conductivity, the thermal capacity, and the specific mass of the building envelope elements [5,6]

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