HVAC Control System Using Predicted Mean Vote Index for Energy Savings in Buildings

Daniel Fernando Espejel-Blanco,Jaime Arau,Guillermo Valencia-Palomo,Héctor Ricardo Hernández-De-León,José Antonio Hoyo-Montaño,Abel García-Barrientos,Jorge Luis Camas-Anzueto

doi:10.3390/buildings12010038

Abstract

Nowadays, reducing energy consumption is the fastest way to reduce the use of fossil fuels and, therefore, greenhouse gas emissions. Heating, Ventilation, and Air Conditioning (HVAC) systems are used to maintain an indoor environment in comfortable conditions for its occupants. The combination of these two factors, energy efficiency and comfort, is a considerable challenge for building operations. This paper introduces a design approach to control an HVAC, focused on an energy consumption reduction in the operation of the HVAC system of a building. The architecture was developed using a Raspberry Pi as a coordinator node and wireless connection with sensor nodes for environmental variables and electrical measurement nodes. The data received by the coordinator node is sent to the cloud for storage and further processing. The control system manages the setpoint of the HVAC equipment, as well as the turning on and off the HVAC compressor using an XBee-based solid state relay. The HVAC temperature control system is based on the Predicted Mean Vote (PMV) index calculation, which is used by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to find the appropriate setpoint to meet the thermal comfort of 80% of users. This method combines the values of humidity and temperature to define comfort zones. The coordinator node makes the compressor control decisions depending on the value obtained in the PMV index. The proposed PMV-based temperature control system for the HVAC equipment achieves energy savings ranging from 33% to 44% against the built-in control of the HVAC equipment, when operating with the same setpoint of 26.5 grades centigrade.

Highlights

Managing energy consumption in buildings is a critical issue nowadays due to the fact that energy consumption in buildings, mainly electrical energy, is approximately 40% of the total worldwide consumption [1,2,3]
This paper presented an alternative control system to reduce energy consumption in HVAC equipment
The proposed control system is based upon the Predicted Mean Vote (PMV) index and, it controls the operation of the HVAC equipment via wireless XBee modules

Summary

Introduction

Managing energy consumption in buildings is a critical issue nowadays due to the fact that energy consumption in buildings, mainly electrical energy, is approximately 40% of the total worldwide consumption [1,2,3]. This study compared a PMV-based control with a temperature conventionalbased control conducted in a typical glazed office room subject to solar radiation for an occupied day This model used PMV index values from −0.2 to 0.2 and obtained 1.6% of energy savings. Unlike previous works, based upon different thermal comfort, PMV methods to control the temperature in HVAC systems, the PMV index values proposed in this paper are −0.6 to 0.6 in the maximum range and −0.2 to 0.2 in the minimum range. Is proposed, this control works with PMV index values in the −0.117 to 0.528 range and, it uses the psychometric chart to visualize the operating setpoint This control was developed to work in a test room in the summer season in the City of Hermosillo, Mexico.

Predicted Mean Vote Index

Control System

Sample Size

Tests Descriptions

Results and Discussion

Conclusions