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

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.

Effect of Sampietrini Pavers on Urban Heat Islands

Cool pavements are reflective and/or permeable pavements that improve microclimate of urban areas where heat islands cause discomfort to citizens. Stone pavements lower surface temperatures and reduce the amount of heat absorbed. This study assessed, using ENVI-met 4.3 LITE software, how air temperature and predicted mean vote depend on physical properties of the road pavement. A comparative microclimatic analysis was implemented on a rectangular square in Rome (Italy) in the summer, paved in three different ways: asphalt, traditional sampietrini, and permeable sampietrini. The model considered local weather parameters, surrounding fabric, and vegetation to give reliable results in terms of numerical and graphical output using the application tool Leonardo. The tested pavement types affected air temperature during the day, but did not influence this variable in the early morning. Permeable sampietrini pavement was more effective than traditional sampietrini pavement in reducing air temperature compared to the current asphalt surface. The road pavement did not, however, affect human comfort in terms of predicted mean vote. The obtained results are useful for further investigation of parameters that could modify the microclimatic conditions of urban areas.

Thermal Comfort Study Based on PMV-PPD in the Building of a Screening Center for COVID-19

Background: One way to achieve a standard heating, ventilating, and air conditioning system with maximum satisfaction is to use a thermal index to identify and determine the thermal comfort of people. In this study we intend to evaluate thermal comfort based on PMV-PPD (Predicted Mean Vote/Predicted Percentage Dissatisfied) model in workers of screening center for COVID-19. Methods: The study period was from March 1 to October 31, 2020. In this study, we used the ISO 7730 model to determinate PMV-PPD index. PMV index was used to determine thermal comfort at different scales in Birjand city with arid and hot climate. All data were analyzed using R software (version 3.3.0) and IBM SPSS statistics softwares. Results: The maximum and minimum recorded physical PMV values in the study period were observed in June as (2.09 ± 0.03) and March as (-1.27 ± 0.14), respectively. The amplitude of the thermal sense in the study period was varied between slightly cool (-1.5) and warm (+2.5). The PPD in spring was 40% which indicated slightly warm to hot condition. Conclusions: The October was the only month during the study in which thermal stress was in comfort or neutral thermal condition. Our results suggest that thermal comfort has dimensions and indices which are helpful in managing energy consumption.

Experimental Investigation of Adaptive Thermal Comfort in French Healthcare Buildings

The thermal comfort requirements of disabled people in healthcare buildings are an important research topic that concerns a specific population with medical conditions impacted by the indoor environment. This paper experimentally investigated adaptive thermal comfort in buildings belonging to the Association of Parents of Disabled Children, located in the city of Troyes, France, during the winter season. Thermal comfort was evaluated using subjective measurements and objective physical parameters. The thermal sensations of respondents were determined by questionnaires adapted to their disability. Indoor environmental parameters such as relative humidity, mean radiant temperature, air temperature, and air velocity were measured using a thermal microclimate station during winter in February and March 2020. The main results indicated a strong correlation between operative temperature, predicted mean vote, and adaptive predicted mean vote, with the adaptive temperature estimated at around 21.65 °C. These findings highlighted the need to propose an adaptive thermal comfort strategy. Thus, a new adaptive model of the predicted mean vote was proposed and discussed, with a focus on the relationship between patient sensations and the thermal environment.

An Efficient Method to Compute Thermal Parameters of the Comfort Map Using a Decreased Number of Measurements

This paper presents an empirical approach to design ideal workplaces using the PMV-PPD (predicted mean vote–predicted percentage dissatisfied) method set in ISO 7730 in terms of thermal comfort. The key concept behind our method is that the overall employee satisfaction might be improved if they can select the most suitable desk based on their personal comfort preferences. To support desk sharing, we designed a comfort map toolkit, which can visualize the distribution of comfort parameters within office spaces. The article describes the steps to create comfort maps with methods already widely used, as well as a new one developed by our research team, including the measurement procedures and the theoretical background required.

Conforto térmico em trabalhadores de aviários

Enquadramento: podendo existir vulnerabilidade dos trabalhadores avícolas face às temperaturas do interior dos aviários em comparação com as do exterior é importante analisar a sua exposição ocupacional em termos de conforto térmico. Objetivos: avaliar o conforto térmico em trabalhadores do setor avícola no ambiente interior e exterior dos aviários e analisar a sua possível relação com a fase de desenvolvimento do frango. Metodologia: o estudo efetuado foi observacional, transversal, com uma amostra por conveniência de 6 trabalhadores de 8 aviários. A recolha de dados foi realizada através de um questionário dirigido a todos os trabalhadores seguida da medição dos valores de Predicted Mean Vote (PMV) e Predicted Percentage of Dissatisfied (PPD). Resultados: em aviários de frangos com 8 dias de idade verificou-se uma total concordância entre os valores de PMV e PPD, nos de 35 dias uma concordância significativa e nos de 85 dias uma considerável concordância. Conclusão: existe desconforto térmico nos trabalhadores avaliados, especialmente nos que trabalham em aviários para frangos com 8 e 35 dias de idade. O desconforto térmico foi pior nos aviários de frangos com 8 dias, revelando assim a relação entre o índice de conforto térmico e a fase de desenvolvimento do frango.