Solar water heater, thermal energy, solar radiation, renewable energy, solar collector, energy efficiency, thermal collector, solar panel
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Abstract
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Abstract
This document presents a monograph on solar water heaters, explaining their principle of operation, sizing, construction, and optimization techniques to improve efficiency.
Extract
[...] For D2 concentrators, the limit is given by : . IV-2. Optimization of a flat collector's efficiency from the angle of inclination Ideally, a solar collector should be oriented in such a way that the angle formed by the incidence of solar rays and the collector is zero, i.e., the collector must be permanently perpendicular to the solar radiation. This is achievable through solar tracking systems, which are a necessity for concentrators. Unlike concentrators, flat thermal collectors are generally installed with a fixed inclination and orientation, chosen towards the south or north, depending on the geographical location of the site relative to the equator, so that the collectors can absorb the maximum amount of energy near noon, where the sun's height is at its zenith and the values of illumination due to solar radiation are maximum. [...]
[...] In the case of water, its characteristics are such that: - High specific heat and heat capacity; - High thermal stability. To calculate the heat power exchanged between the water and the wall of the heat exchanger, the following formula is applied: Pe = Qm . Cwater .?T Where Pe: the heat power exchanged by the water in Watt; Qm: the mass flow rate of water in kg/s; Cwater: the specific heat capacity of water = 4185 J/(kg.°C) = constant characterizing the body's ability to store heat; the temperature difference in °C during the heat exchange III-2-2-6. [...]
[...] Solar Water Heater Modeling and Sizing Modeling involves representing a system with mathematical equations in order to know how to dimension the main parameters involved in its realization. Figure Flat plate solar collector III-1. Modeling of solar water heater As we defined in paragraph III, that modeling is the representation by mathematical equations in this part we will present the equations that govern within a solar water heater. Figure Cut of the flat collector studied -The dimensions of the piping: : The internal diameter of the piping. [...]
[...] : Water flow rate of the sensor. - : Mass flow rate per unit area of the sensor : III-1-2. Thermal transfer at the level of a solar water heater Figure Schematization of convective fluxes in a glass solar sensor The thermal balance resulting and taking place at the level of the absorbing wall is written as : Qsa = Qu + Qst + Qp Where Qsa : the solar flux absorbed in [W/m< sup >2]2 Qp: the heat loss through the insulation in [W/m< sup >2]2 Qu: the useful heat flux transmitted to the heat carrier fluid in [W/m< sup >2]2 Qst : the heat stored in the sensor [W/m< sup >2]2 Let Qst, the energy stored per second in the sensor or heat flux, its expression is such that : Where Me : the water mass of the sensor, [...]
[...] To remedy this, we resort to optimizing the parameters influencing the efficiency by acting on the technology of the materials used in the construction of the solar water heater as well as the position of the collector facing the solar radiation. [...]
