Study Work on Parabolic Solar through Water Heating system with Various Type of Coating on Reflectors with or without Glass

Abstract

Solar energy serves as the wellspring of all forms of energy present on Earth, establishing its role as a significant contributor. The contemporary surge in global energy demand exerts pressure on traditional energy reservoirs, including coal, petroleum, natural gas, and fossil fuels. These resources, limited in nature, face potential depletion in the absence of recourse to alternative sources. Solar energy emerges as a viable substitute for diverse energy production processes due to its renewable attributes, devoid of any contribution to the emission of greenhouse gases or environmental contaminants. Furthermore, its enduring nature safeguards against imminent depletion. This study delves into the prospect of harnessing solar energy for hot water generation through a thermal system. The research involves the construction of a solar radiation tracking system operated manually. A comparative evaluation ensues, featuring parabolic trough solar water heaters utilizing distinct reflector materials, both with and without the incorporation of glass covers. The reflective component materializes as a stainless steel sheet-formed trough, skillfully cut and welded, integrated with aluminum foil and mirror strips for reflective enhancement. Functioning as the absorber, a copper tube boasting an 18mm diameter and 240mm focal length is adopted. The experimental protocol spans four phases, each involving varying reflector configurations, including instances with and without a glass cover affixed to the trough\'s surface to mitigate wind-induced losses below. Performance metrics are meticulously documented, subsequently subjected to comparison against three alternative scenarios. The experimentation transpired within the precincts of SRCEM College, Banmore, during the summer season of May 2023, situated in the region of Madhya Pradesh, India. The study\'s culmination sheds light on the potential of solar thermal systems for hot water generation. The insights gained from the comprehensive evaluation of parabolic trough solar water heaters, encompassing diverse reflector configurations and the influence of glass cover presence, lay the groundwork for a potential revolution in sustainable energy utilization. Amidst the contemporary energy conundrum, this research unveils innovative avenues that harness the abundant offerings of solar energy, promising a cleaner and enduring energy landscape.

Introduction

I. INTRODUCTION

Manifesting as electromagnetic waves, the sun radiates energy uniformly in all directions. This celestial entity bestows the essential life-sustaining energy upon our solar system. A clean, inexhaustible, copious, and universally accessible renewable energy resource, it refrains from engendering the emission of greenhouse gases or other contaminants into the ambiance. Its sustainability thrives over the long term, a stark contrast to the finite temporal scope characterizing conventional oil, coal, and gas reserves. Nonetheless, solar energy is not without its limitations, predominantly as it manifests as a dispersed form of energy, intermittently and sporadically accessible, rather than perpetually and consistently. Notably, the sun generates a yearly energy yield of 2.81023 kw/year.[1]

A. Energy Consumption and Standard of Living       

A nation's energy consumption is apportioned across distinct domains or sectors contingent on energy-centric activities. These sectors can be further disaggregated into subcategories:

1. Residential sector (comprising households and offices, inclusive of commercial edifices).
2. Transportation realm.
3. Agricultural domain.
4. Industrial sector.

Heightened energy utilization within a country signifies the intensification of specific industries. This could entail enhanced household comforts engendered by multifarious appliances, improved transportation networks, and augmented agricultural and industrial output. Cumulatively, these dynamics culminate in an elevated standard of living. Consequently, a nation's per capita energy consumption mirrors its populace's quality of life or affluence (i.e., income). Table 1 presents outcomes, underscoring this concept, wherein comparative data pertaining to annual primary energy consumption across select nations is presented to accentuate the notion.[2]

The global annual energy consumption is currently estimated at 500 hexajoules. In the context of this energy distribution, the United States, representing approximately 6% of the world's population, accounts for 26% of the total energy consumption. Conversely, India, encompassing roughly 17% of the global population, contributes only 3.4 percent to the total energy usage. This disparity is mirrored in the discernible contrast in the quality of life experienced by the populace of these nations. Electricity assumes a pivotal role as a prerequisite for a nation's economic and societal advancement. In 2007, the per capita electrical energy consumption in the United States stood at 12,123 kWh, while India's corresponding figure was 702 kWh.[3]

B. Depletion of Solar Radiation

Various components compose Earth's atmosphere, including gaseous elements, suspended dust, and minute solid and liquid particles. Among these substances are air molecules, ozone, oxygen, nitrogen, carbon dioxide, carbon monoxide, water vapor, dust, and water droplets. Consequently, solar energy encounters hindrance as it navigates through the atmosphere. Notably, different molecules serve distinct functions, such as selectively absorbing specific wavelengths, resulting in an increase in the energy and temperature of the absorbing molecules:

1. Absorption

a. Different molecules selectively absorb specific wavelengths, elevating their temperatures due to absorbed radiation.

b. X-rays and strong ultraviolet light are absorbed by atmospheric gases like nitrogen and molecular oxygen.

c. Ozone effectively absorbs UV energy within the (2.3 μm) range.

d. Water vapor (H2O) and carbon dioxide predominantly absorb infrared light beyond the range (> 2.3 μm) while diminishing near-infrared energy within this range.

d. Dust particles and air molecules, regardless of wavelength, absorb a portion of solar radiation energy.[4]

2. Scattering  

The dispersed incoming energy is redistributed by dust particles and air molecules of various sizes, resulting in a portion of radiation being lost to space and the remaining diffused and directed downwards to the Earth's surface from multiple angles. A significant portion of incoming solar radiation is reflected back into the atmosphere by clouds. Another portion is absorbed by clouds, while the remainder is scattered and transmitted downwards to the Earth's surface in cloudy conditions

3. Beam Radiation

Solar radiation that propagates in a straight line and reaches the Earth's surface without altering its course, aligned with the sun, is referred to as beam or direct radiation.

4. Diffused Radiation

Solar radiation scattered by aerosols, dust, and molecules is categorized as diffused radiation, characterized by its lack of a singular direction.[4]

II. SOLAR TIME

Solar time is anchored to the instance when the sun crosses an observer's meridian, known as solar noon. At solar noon, the sun occupies its zenith position in the sky. The sun traverses each degree of longitude in 4 minutes. Standard time is adjusted to solar time through the following equation:Solar time =Standard time   

III. APPLICATION OF SOLAR ENERGY

1. Power Plants: Solar energy facilitates power generation through methods such as utilizing the sun's heat to boil water, generating steam for turbine rotation and electricity production. Solar panels, photovoltaic and thermoelectric technologies, among others, convert sunlight into usable power.
2. Household: Solar energy is increasingly integrated into households, powering residential appliances and solar heaters for hot water. Photovoltaic cells installed on rooftops capture and store energy in batteries, providing a sustainable energy source for various purposes.
3. Commercial Use: Solar panels, including glass PV modules, installed on building rooftops provide reliable electricity to businesses, offering an independent power source for diverse applications.
4. Ventilation System: Solar energy aids in ventilation, powering fans for moisture, odor, and heat regulation in structures.
5. Power Pump: Solar power supports water circulation within buildings, enhancing ventilation and distribution.
6. Swimming Pools: Solar blankets and solar hot water heating systems maintain pool water temperature during winter.
7. Remote Applications: Solar panels and batteries enable remote buildings like schools and clinics to generate and utilize electric power on the go.[6]

IV. SOLAR COLLECTOR

Solar electricity has relatively low density per unit area (ranging from 1 kW/m2 to 0.1 kW/m2), resulting in inefficiency. Solar thermal collectors encompass a substantial ground area to address this limitation. The fundamental element of a solar thermal system is the solar thermal collector, which adeptly captures solar energy as heat and transfers it to a heat transfer fluid. This fluid then conveys the heat to a thermal storage tank/boiler, ready for subsequent phases of the system.[7]

A. Classification of Solar Collector

Figure 1 provides an overview of solar collector classification, categorized by their manner of solar light capture. Non-concentrating collectors absorb radiation upon impact with their surfaces, while concentrating collectors elevate radiation concentration per unit area before absorption. Concentrating collectors are subdivided into focus and non-focus types based on their radiation concentration techniques. The focus type further delineates into line or point focus depending on the focusing mechanism.[7]

XI. FUTURE SCOPE

1. Exploring the use of air as the working fluid, which could serve winter home heating and grain drying purposes.
2. Investigating the application of a single highly reflective mirror sheet for enhanced reflection, as opposed to mirror fragments.
3. Exploring the feasibility of using nickel coating as an alternative reflector material.
4. Experimenting with solar cells to generate electricity instead of utilizing the absorber tube, potentially storing energy in a battery. Enhancing heat absorption through Teflon or black paint coating on the absorber pipe could also be explored.
5. Incorporating automated sun tracking with LEDs into the collector's support structure.
6. Considering absorber tube coiling to further enhance efficiency.
7. Evaluating more efficient absorber materials to replace the copper tube.
8. Factoring in wind losses and efficiency calculations by employing a glass cover, which would account for real-world conditions.
9. Scaling up the trough size to impact its effectiveness and potentially integrating it into larger areas such as building roofs.

Conclusion

1) The highest working fluid outlet temperature, reaching 51.9°C, was achieved in the fourth experiment. This specific setup employed a mirror as a reflector and featured a plane glass cover over the trough face. Notably, this temperature is twice the inlet water temperature, which was 26°C. Correspondingly, the first, second, and third arrangements yielded maximum temperatures of 40.6°C, 50.4°C, and 51.7°C, respectively, around 2.00 p.m. 2) The greatest efficiency was observed in the second experiment, utilizing aluminum foil as a reflector with a plane glass cover, registering an efficiency of 52.03%. This marked a 68.70% improvement compared to the first experiment\'s maximum efficiency, which used aluminum as a reflector without a plane glass cover. 3) The third experiment, employing mirror strips as a reflector without a plane glass cover, demonstrated an efficiency of 77.80%, indicating a 15% increase over the second experiment\'s trough efficiency. 4) Ultimately, the fourth experiment achieved the highest efficiency of approximately 13.287%. This experiment employed mirror strips as a reflector with a plane glass cover and outperformed the third experiment\'s efficiency by about 42%. Remarkably, this fourth experiment\'s efficiency was about 82% higher than that of the first experiment. Given these outcomes, we conclude that, for troughs of the same specifications, the most efficient and cost-effective configuration involves using a mirror as a reflector along with a glass cover on the trough face.

References

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Copyright

Copyright © 2023 Dashrath Singh, Amit Agrawal. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.