A solar energy operated mechanism for mitigating heat stress in cattle barn

Introduction

It is being strongly observed that the climate change has increased the intensity and duration of heat waves by trapping more heat in the atmosphere. This is leading to severe health impacts on humans and animals. The heat stress experienced by humans and animals is associated with air temperature in conjunction with humidity of the environment. The negative impacting is being felt in their production and reproduction, intensive selection of production traits, and evoke of physiological responses (Schüller et al., 2014; Yasobant et al., 2025, Habeeb et al., 2018) [18,20,6] . It also negatively impacting the lactation phase and milk production in dairy cattle, as high productivity dairy cattle show a high amount of metabolic heat production and requires a cool surrounding for releasing excess heat (Wolfenson and Roth, 2019; Oliveira et al., 2025; Lambertz et al., 2014) [19,14,9] . The environmental risk factors on animals are assessed by an indicator, called Temperature-Humidity Index (THI). Some of the popular mathematical formulae for calculation of THI are reported in Table1. This indicator gives the effect of thermal stress in terms of ambient temperature and relative humidity (Bohmanova et al., 2007) [3] . Based on experimental observations, the resilience of animals against the heat stress is classified by several researchers however the widely acceptable classifications of Hahn et al. (2009) [7] is enumerated in Table 2. Based on these facts this paper describes the heat stress faced by dairy animals in the barns often erected with bricks walls and roof of tin sheets supported by iron angles. Such types of cattle barns are located at ICAR Research Complex for Eastern Region Patna (25.59°N, 85.08°E) and therefore selected for study and describes about a prototype solar energy operated mechanism for mitigating heat stress. [10] T is the temperature (°C) and RH: relative air humidity (%) of animal environment

Materials and Methods

The increasing trend of dairying at commercial level necessarily requires good infrastructure and high productivity dairy cattle. This has led to construction of sizeable barns often made of bricks walls, good number of windows fitted with wire mesh for proper ventilation, and iron angles supported painted tin sheets roof. The physical dimension of the barn selected for study was of 20 m × 7 m × 4 m. During intense heat waves conditions barn windows were covered with canvas cloths to avoid direct exposure of hot air. In the month of March to June, random measurements of temperature and relative humidity inside the barn showed that the absolute temperature difference between the barn temperature (Tb) and outdoor temperature (To), i.e., never exceeded 10 percent of the To, and similarly the absolute difference in relative humidity of barn ) and outdoor relative humidity ), i.e., was always below 11%. The and both were directly dependent on the wetness of barn, number of cattle in the barn and the wind flow through the windows. If windows were not covered then and were minimum, as suggested in studies (Patil et al., 2025) [16] . With these observations, there were following possibilities:

Temperature and humidity of barn were same as outdoor Temperature was same but the relative humidity was higher than the outdoor Temperature was same but the relative humidity was less than the outdoor Temperature was higher than the outdoor but humidity was same Temperature and humidity both were higher than the outdoor Temperature was higher than the outdoor, but relative humidity was lower Temperature was lower than the outdoor, but relative humidity was same Temperature was lower than outdoor, but relative humidity was higher Temperature and relative humidity both were lower than the outdoor To outdoor temperature and relative humidity data were acquired from the nearby aerodrome weather station. The variation of maximum temperature and relative humidity of critical summer months of 2024 are shown in Fig. 1 and Fig.

Results and Discussions

The THI of the barn at 8.00 am, 12.00 pm and 4.00 pm for critical summer month, of March-June is reported in Table 3.

Interpretation of data shows that the heat stress level exceeded the permissible limits (> 74) almost in all the months throughout the day and therefore cattle were facing heat stress in all the months from March-June, and the degree of stress increased towards the June. This necessitated measures for the barn to assuage heat stress. As suggested in literatures (Bernabucci, [2,13,11,1,5,15,4] some common measures for heat stress mitigation include roof sprinkling, forced air supply, misting or fogging, but the selection of type of measures should be cost-effective and easy in maintenance. Further, to assess the changes in of barn from reference vale more elaborately under different scenarios, the was plotted for different month for different scenarios and is shown in Figure 2. , i.e., when temperature and humidity both were decreased simultaneously. This condition requires air conditioner, but it was a costly affair for a barn. The next maximum change was with the scenario and this could be achieved by air blowing. But air blowing mechanism has a limitation that it has limited capacity of temperature reduction. The third maximum change was possible with the scenarios and this can be achieved by misting or fogging. Further a fogging mechanism needs continuous energy supply for operation. The required energy can be supplied either by electricity or by fossil fuel. Due to the lack of grid power connectivity and increase in fossil fuel cost and associated environmental factors, the solar energy application could be a better option. To assess the solar energy availability at experimental site the mean monthly averaged daily solar radiation of the site measured by pyranometer by Rahman and Bhatt (2014) [17] is shown in Figure 3. From Figure 3 it was observed that the solar irradiance was ranging from 200-953 W/m 2 over a day and the mean monthly daily averaged radiation intensity from March to June was 6.4-4.8 kW/m 2 /day and could be good source of energy for operating heat stress mitigation mechanism in the cattle barn. To utilize solar energy of the site a fogging mechanism was designed (Figure 4) using a permanent magnet DC motor of rating 1500 W, a 1.8 kWp photovoltaic solar array, a compressor of power dissipation rating of 1000 W, a plastic tank of 500 liters capacity, nozzles with adjustable aperture, ¾ inch GI pipe, high pressure flexible conduit and some control volves. The selection criteria of compressors were based on its working pressure and choosing nozzles with variable aperture was to get fine size water droplets even at low solar irradiance, as droplets size was inversely proportional to nozzle aperture. To assess the performance of the developed fogging mechanism under different solar radiation conditions, the working pressure of the mechanism was measured and plotted against the solar irradiance (Figure 5). The solar irradiance between 8.00 AM to 3.00 pm on a clear day of March to June was ranging from 400-900 W/m 2 and corresponding to this incident solar radiation range, the working pressure of the mechanism was 53-134 psi (Figure 5). For the selected barn six nozzles were networked using GI pipe from mechanism to barn and flexible pipe segments were used to connect the nozzles with GI line. These nozzles were installed at the windows of the barn (Figure 6). At relatively low pressure, the nozzle aperture was adjusted to reduce aperture area to get fine droplets. The operating view of the mechanism in the Bufalo barn is shown in Fig. 7. There had been a substantial cooling once mechanism was operated for ½ hour. This mechanism cools the surfaces and air through the process of evaporative cooling where fine water droplets absorb heat from the surrounding air as they evaporate. Further, the tiny droplets remain suspended in the air a longer period and allowing evaporation for a longer period and lowers the temperature with increase in humidity. Further, a single mechanism can covered a large barn by operating only few nozzles at a time and can cover a number of nearby barns barns by diverting supply line other barns at a certain interval of time. The solar array operating the mechanism can also be used for groundwater pumping or lifting pond water from a nearby pond when fogging in barn was not required. Again, the outdoor conditions of temperature and humidity of the site is nearly similar to the temperature and humidity conditions as well as solar radiation conditions of other parts of the country, hence the developed mechanism has wider applicability.

Acknowledgement

AcknowledgementsThe authors gratefully acknowledge the research was supported by the Indian Council of Agricultural Research, Department of Agricultural Research and Education, Government of India.

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