Solar Technology

Solar energy is considered an attractive source of renewable energy that can be used for water heating in both homes and industry. Heating water consumes nearly 20% of total energy consumption for an average family. Solar water heating systems are the cheapest and most easily affordable clean energy available to homeowners that may provide most of the hot water required by a family.

The solar heater is a device which is used for heating the water, for producing the steam for domestic and industrial purposes by utilizing the solar energy. Solar energy is the energy which is coming from the sun in the form of solar radiations in an infinite amount when these solar radiations fall on the absorbing surface, then they get converted into the heat, this heat is used for heating the water. This type of thermal collector suffers from heat losses due to radiation and convection. Such losses increase rapidly as the temperature of the working fluid increases.

Approximately half of the global energy demand is used for heating purposes. At present, this demand is served largely by conventional energy sources such as oil, gas and coal, either directly or indirectly via electrification. Across the economy, heating is important for functions such as sanitary hot water preparation, domestic and working-space comfort, cooking and food preparation and preservation, and in many industrial and manufacturing processes.

Electricity is often used for heat generation, often due to simplicity, cost considerations, and the lack of distributed heat provision when heat generation and consumption are separated by large distances. Direct electricity-to-heat conversion is not thermodynamic-ally efficient, however, even when the inclusion of some renewable electricity has been considered.

Solar-thermal and hybrid PV-T technologies are affordable solutions that can be implemented within local energy systems to cover a large fraction of the corresponding heat demands at high efficiency, low cost and with low associated emissions, therefore enabling the emergence of such distributed systems.

Sunlight is converted directly into thermal energy in solar thermal collectors. The sunlight is absorbed by a material, converted to heat and transferred to a fluid stream.

The heated fluid (generally air, water, or antifreeze liquid) can be used for several purposes such as space heating, hot-water heating, process of heating, and even cooling.

Several designs of solar collectors are available, including with or without single or multiple glass covers, or with a vacuum for reducing the heat losses in so-called unglazed, glazed or evacuated collector designs. High-performance collectors feature thermal absorbers with special selective coatings that maximize the sunlight absorption and further reduce heat losses. Black chrome over a nickel base is often used on copper plates, or alternatively, a titanium-nitride-oxide layer12. By reducing heat losses, the presence of a glass layer or vacuum allows operation with higher efficiencies at higher temperatures over an extended temperature range.

A particularly interesting design is the evacuated-tube a collector with heat pipes, in which the fluid evaporates and condenses in tubes as it transfers heat, in a relatively efficient and affordable design.

Solar-thermal collectors can deliver heat over a wide range of temperatures with solar-conversion efficiencies in the range 40-70% ii. Domestic systems are well-established and commercially mature, with collector design-point efficiencies often exceeding 75%. Although solar-thermal systems require relatively high initial investments for system installation iii, typically in the range $1000-2300 per m2 24, 25, compared to the $290-860 per m2 for small-scale PV systems iv 26, 27, they have relatively few moving parts and, consequently, low operating and maintenance requirements. Running costs can be as low as $100 per year 28, with 20-year lifetime guarantees to maintain.

At the same time, solar-thermal collectors allow the design of heating systems with low-cost integrated thermal storage. As the solar resource follows largely predictable annual and daily cycles, the output of solar systems is also largely predictable, and this forecasting can help with the integration of storage. The thermal output can be stored with low losses

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Hot water storage tanks are already commonly employed in heating installations.