“DOMESTIC SOLAR WATER HEATER SYSTEM WITH EXTENDED HEATING CYCLE”

Abstract

ABSTRACT “DOMESTIC SOLAR WATER HEATER SYSTEM WITH EXTENDED HEATING CYCLE” comprising a solar heat collector (1), a heat transfer element (2), a primary oil tank (3), connecting tubes (4), a secondary oil tank (5), a water tank (6), a water outlet (7), and a water inlet (8). The system operates through thermal expansion and contraction of oil, wherein during daytime operation, solar energy captured by the collector heats oil in the primary tank through the heat transfer element, causing the oil to expand and rise through connecting tubes into the secondary oil tank. The heated oil in the secondary tank transfers heat to the water tank. During nighttime, as the collector cools, oil in the primary tank contracts and recedes through the connecting tubes, creating a thermal break between primary and secondary tanks. This thermal isolation allows the secondary tank to maintain heat for an extended period while the primary tank cools, enabling continuous hot water availability throughout day. The cycle automatically repeats the next day when sunlight becomes available, providing a self-sustaining heating system without external power requirements. Refer Figure 1

Specification

DESC:FIELD OF INVENTION
[0001] The present invention relates to a solar water heater. Particular, the present invention relates to a domestic solar water heater system that allows the heating cycle to be extended making hot water available throughout the day.
BACKGROUND OF INVENTION
[0002] Existing systems for heating fluids such as water and the like may operate on gas, diesel fuel, electricity or solar energy. Due to the rising cost of gas, diesel fuel, and electricity it is desirable to use solar energy for heating. In
addition, solar energy is a green resource and its use does not generate pollution. In order to save the cost of buying a new boiler it is desirable to convert existing heating system to operate on solar energy or even mix the existing method together with operation on solar energy, and thus save the cost of a new boiler.
[0003] Solar water heaters (SWH) are increasingly becoming popular as a sustainable solution for domestic and commercial water heating needs. These systems harness renewable solar energy, providing a cleaner alternative to traditional electric or gas-powered water heaters. Despite their benefits, conventional solar water heaters often face limitations in terms of continuous hot water availability, especially during cloudy days, nights, or periods with limited sunshine.
[0004] Conventional solar water heating systems employ a straightforward mechanism comprising solar collectors, storage tanks, and circulation systems. These components work together to convert solar radiation into usable thermal energy for domestic water heating purposes. While this basic principle
has proven effective during optimal conditions, the system's performance is heavily dependent on direct sunlight availability, leading to significant operational limitations.
[0005] To overcome these challenges, there is an opportunity to develop an advanced solar water heater system with extended heating cycles. Such a system would ensure uninterrupted hot water availability by efficiently managing heat. By utilizing improved heat storage, better thermal insulation, the system can minimize energy loss and limit dependence on auxiliary
heaters. An extended heating cycle will also optimize energy usage by making the most of the solar heat collected during the day and recycling residual heat to maintain consistent water temperatures.
[0006] The present invention employs energy-efficient storage solutions to preserve heat for longer periods and integrates smart controllers that intelligently manage the switch between solar energy and backup heating. The use of advanced heat-exchange mechanisms and superior thermal insulation helps in minimizing heat loss, ensuring that water remains at optimal
temperatures even beyond solar hours.
[0007] Accordingly, there is a need for a domestic solar water heater system which allows to extend the heating cycle so that the hot water is made available throughout the day.
[0008] The domestic solar water heater System with Extended Heating Cycle of the present invention fills gap in existing technologies by ensuring reliable hot water availability throughout the day. This offers a cost-effective and ecofriendly
solution tailored for domestic use, particularly in areas with
unpredictable weather with enhanced thermal management, energy
efficiency, and reduced operational costs, the system provides a compelling alternative for households seeking sustainable water heating options.
[0009] Some of the prior arts are given below:
US4003367A discloses a solar water heater includes an insulated housing with a large storage compartment and a smaller collector compartment, linked by two liquid flow passages. These passages create a thermosiphon effect that circulates water between compartments when solar energy heats the collector. One passage connects the lower parts of both compartments, with sections extending within the insulated front wall and an intermediate section enabling heat exchange to the upper storage compartment. This setup prevents reverse flow when the collector water is cooler than the storage compartment.
KR100767279B1 explains about a system for condensing solar energy for hot water is provided to improve the heat accumulating effect of the solar energy by using a heat accumulating medium such as oil. A system for condensing
solar energy for hot water includes a plurality of solar energy condensing pipes, a case, a heat accumulating vessel, and a hot water vessel. The case surrounds the solar energy condensing pipes to separate the solar energy condensing pipes from outside. The heat accumulating vessel accumulates the
heat condensed in the solar heat condensing pipes. The hot water vessel exchanges heat with the heat accumulating medium stored in the heat accumulating vessel. A medium such as an oil is filled in the solar energy condensing pipes and the heat accumulating vessel.
IN202011037025 discloses a solar water heater comprising of a storage shell for storing a fluid to be heated, a solar radiation collector coupled to the external surface of the storage shell, a heat exchanger is provided inside the
storage shell and is coupled to the solar radiation collection and a reflector is provided below the storage shell for concentrating maximum solar radiation towards the solar radiation collector. The storage shell is having an internal
surface and an external surface. The internal surface being in contact with the fluid to be heated. The solar radiation collector includes a plurality of tubes wound around the external surface of the storage shell. The plurality of tubes
being equipped to carry a heat transfer fluid for absorption of solar radiation.
OBJECT OF THE INVENTION
[0010] The primary object of the invention is to provide a domestic solar water heater system that efficiently harnesses and retains solar energy, enabling a continuous supply of hot water throughout the day.
[0011] Another object of the invention is to provide a dual-tank oil circulation system that maximizes heat retention capabilities through the implementation of a secondary oil tank that maintains heat during non-sunlight hours.
[0012] Yet another object of the invention is to provide a self-regulating solar water heating system that automatically manages oil circulation between primary and secondary tanks through a thermal expansion process.
[0013] Further object of the invention is to provide a domestic solar water heater system that maintains consistent water temperature by intelligently isolating the secondary oil tank during cooler periods.
[0014] Lastly, this invention provides an environmentally friendly and cost-effective solution to daily hot water needs by maximizing solar energy utilization, reducing dependency on auxiliary power sources, and maintaining effective heat retention.
SUMMARY OF THE INVENTION
[0015] The present invention relates to a domestic solar water heater system that employs an unique dual tank configuration, operates through a thermal expansion process to supply hot water consistently throughout the day.
[0016] The domestic solar water heater system of the present invention consists of a solar heat collector (1), a heat transfer element (2), a primary oil tank (3), a secondary oil tank (5), connecting tubes (4) and a water tank (6) fitted inside the secondary oil tank, all configured to achieve efficient water heating through thermal expansion and heat transfer.
[0017] The solar heat collector (1) absorbs sunlight, transferring the captured heat to oil in the primary oil tank (3) via a heat transfer element (2). As the oil heats up, it begins to expand, moving upward through connecting tubes (4)
similar to the behavior of mercury in a thermometer. This expansion continues until the heated oil reaches the secondary oil tank (5).
[0018] The oil in the secondary tank (5) also begins to heat up, transferring this heat to the water in the water tank (6) and warming it up. The system continues this heating process as long as sunlight is available, allowing for ongoing water heating throughout daylight hours.
[0019] As sun goes down during night the solar collector cools the oil in the primary tank also begins to cool down, gradually reducing in volume. This contraction causes the oil in the connecting tubes to recede back into the primary tank, effectively breaking the connection between the primary and
secondary tanks. As a result, the primary tank cools down, but the heat in the secondary tank and the water tank remains insulated, preserving the temperature for an extended period.
[0020] With the next sunrise, the oil in the primary tank heats up again, restarting the cycle. This design ensures a steady supply of hot water during the day and retains heat through the night by isolating the secondary tank when the solar collector is inactive. This invention thus provides a reliable, energy-efficient solution for continuous hot water supply using solar energy.
DESCRIPTION OF INVENTION
[0021] The present invention relates to a domestic solar water heater system that employs a series of interconnected tanks and heat transfer mechanisms to optimize heat capture, transfer, and retention for continuous hot water availability.
[0022] The domestic solar water heater system comprises multiple key components including a solar heat collector (1), a heat transfer element (2), a primary oil tank (3), a secondary oil tank (5), connecting tubes (4), a water tank (6), a water inlet (8) and a water outlet (7) each engineered with specific
characteristics to facilitate efficient thermal cycling process and energy retention to optimize overall system performance.
[0023] The solar heat collector (1) is positioned to directly receive sunlight and functions as the primary source of energy for the system and is constructed as a sophisticated thermal capture device. It features a flat panel constructed with high thermal conductivity materials, typically copper or aluminum. The collector's surface is coated with a specialized dark-colored, heat-absorbing material that achieves a 90-95% absorption rate while minimizing radiative heat loss. A tempered glass cover with high solar transmittance is installed
above the absorber surface, creating an efficient greenhouse effect within the collector. The entire collector assembly is housed within an insulated enclosure that minimizes heat loss through conduction and convection. The collector is mounted using precision-engineered brackets that allow for optimal angular positioning, typically between 30-45 degrees from horizontal, depending on the installation's geographical location.
[0024] The primary oil tank (3) serves as the initial heat repository and is engineered as a cylindrical vessel optimized for uniform heat distribution. This tank is constructed from high thermal conductivity materials, typically copper or aluminum with thermal conductivity. The tank features precision-welded construction with reinforced joints to prevent oil leakage and incorporates an interior surface treatment with anti-corrosion coating to prevent oil degradation. A multi-layer insulation system surrounds the tank to minimize heat loss.
[0025] The tank includes an integrated heat transfer element connecting it to the solar collector, an expansion chamber accommodating oil volume changes during heating cycles, and various monitoring ports for temperature and pressure measurement. Safety relief valves calibrated to system specifications are installed to prevent over-pressurization. The primary oil tank filled with appropriate medium/oil duly taking into consideration its viscosity, heat transfer coefficient etc.
[0026] When sunlight strikes the collector, the oil in the primary tank absorbs the heat and warms up. As it heats, the oil undergoes thermal expansion, increasing in volume and moving upward through connecting tubes. The primary tank is connected to the secondary oil tank via these insulated tubes, which allow for the smooth and efficient upward movement of the heated oil,
similar to the way mercury rises in a thermometer. The design of these connecting tubes is crucial, as they are insulated to prevent heat loss during oil transfer and direct the expanded oil toward the secondary tank without allowing it to cool.
[0027] The connecting tube (4) forms a crucial link between the primary and secondary tanks and is designed to facilitate efficient oil flow through natural convection. These tubes are manufactured from high-grade and feature carefully calculated diameters based on expected oil flow rates. The tubes are
installed with an optimized upward slope to promote natural flow and are arranged in parallel to ensure adequate flow capacity during peak heating periods. The entire tube network is covered with premium insulation incorporating vapor barriers to prevent condensation and Expansion joints are integrated to accommodate thermal movement.
[0028] The thermal expansion mechanism within the connecting tubes is one of the system's unique features. When the oil in the primary tank is heated, it expands and crawls up the tubes toward the secondary tank. This movement of oil is controlled and predictable, following the principles of thermal expansion. Once the oil cools, its volume decreases, and it recedes back into the primary tank, effectively isolating the secondary tank from the primary. This process, known as thermal isolation, prevents heat loss from the secondary tank at night.
[0029] The secondary oil tank (5) is engineered with a larger volume capacity compared to the primary tank, typically 1.5-2 times larger, and incorporates a multi-chamber internal design with baffles to prevent thermal stratification. This tank features a superior insulation system, often utilizing advanced
materials such as vacuum panels or aerogel. The tank includes an integrated heat exchange surface maximizing contact with the water tank, level monitoring systems ensuring proper oil distribution, and a pressure equalization system maintaining system balance. Multiple temperature sensing ports are installed at various levels to monitor thermal stratification and
system performance.
[0030] The secondary oil tank serves as an intermediary heat storage unit, receiving hot oil from the primary tank once it has expanded enough to flow through the connecting tubes. The secondary tank is strategically positioned above the primary tank to facilitate the natural upward movement of the heated oil.
[0031] Upon reaching the secondary tank, the hot oil begins to transfer its heat to the water in the water tank. The secondary tank incorporates a heat exchange mechanism, whereby the heat from the oil is conducted to the water without allowing direct mixing of oil and water. This feature maintains the quality and safety of the water while maximizing thermal efficiency.
[0032] The water tank (6) is designed to store and deliver hot water for usage and is placed within the secondary oil tank incorporates a sophisticated double-wall construction. The inner vessel is manufactured from food-grade stainless steel to ensure water quality and longevity. The tank features efficient heat exchange surfaces maximizing thermal transfer from the secondary oil tank maintaining temperature uniformity throughout the water volume.
[0033] Multiple temperature monitoring points and pressure relief mechanisms ensure safe operation, while inlet and outlet ports incorporate anti-scalding protection. A sacrificial anode is installed to protect against corrosion, and additional insulation layers minimize heat loss to the environment.
[0034] In the present invention, a low viscosity, non-flammable, oily medium having a boiling point of 100°C. or more is used, instead of ordinary water or water to which antifreeze is added, as a heat storage medium. It is known in the art that solar cells with conventional heat collecting pipes can theoretically
warm the medium up to 330-500°C, depending on the specifications. Therefore, when water is used as a medium, the temperature of the medium cannot exceed 100°C., so it is utilized to a much less than the capacity of the device. The oily medium is a low pressure, can generate a high temperature
heat, both liquid and excellent heat storage and latent heat.
[0035] The operation of the system relies entirely on solar energy, following a daily cycle based on temperature changes in the primary tank. The working principle of the present invention is given as follows:
[0036] During daytime operation, the system functions through a sophisticated thermodynamic cycle. Solar radiation incident on the collector is absorbed by the selective coating, creating a temperature gradient that transfers heat to the oil through conduction. As the oil temperature increases, typically reaching
60-80°C, thermal expansion occurs at a rate of approximately 0.7-0.9% per 10°C temperature rise. This expansion creates pressure in the primary tank, driving the oil upward through the connecting tubes at a rate naturally regulated by the temperature difference that it reaches the secondary oil tank.
Once the oil from the primary oil tank reaches the secondary oil tank, the oil in the secondary oil tank starts becoming hot too, which in turn heats up water in the water tank. This process continues as long as the sun is available.
[0037] The nighttime operation phase begins as solar input decreases and the collector temperature drops. The oil in the primary tank begins cooling and contracting, causing the oil level in the connecting tubes to gradually descend. This effectively breaks the connection between primary oil tank and secondary oil tank. This recession creates a thermal break between the tanks, leaving the secondary tank thermally isolated. The multiple insulation layers maintain oil
temperature with minimal heat loss, typically less than 5°C per 12 hours. The secondary tank maintains its elevated temperature through the night, most probably with water temperature typically remaining above 40°C until morning.
[0038] The system is designed to restart naturally each morning. As the sun rises, the oil in the primary tank is reheated, expands, and the cycle begins again. This thermal cycling allows for a continuous supply of hot water during the day, with retained heat available during the night.
[0039] ADVANTAGES OF THE INVENTION:
? Allows to extend the heating cycle of the solar water heater
system so that the hot water is made available throughout the day thereby improving the performance of the solar water heating
system
? Allows optimum utilization of solar heat thereby allowing to
conserve electricity/gas
? As solar power is available plenty, money can be saved by
harnessing of the solar power
[0040] Additionally, the invention aims to minimize energy loss through the use of oil, which efficiently transfers and retains heat. The simplicity of the design promotes long-term functionality without the need for complex mechanical parts, enhancing durability and reliability.
BRIEF DESCRIPTION OF DRAWINGS
[0041] Figure 1 shows a schematic view of a domestic solar water heater system of the present invention.
[0042] Figure 2 shows a mechanism of the domestic solar water heater system of the present invention.
REFERENCE NUMERALS
1 Solar heat collector
2 Heat transfer element
3 Primary oil tank
4 Connecting tubes
5 Secondary oil tank
6 Water tank
7 Water outlet
8 Water inlet ,CLAIMS:CLAIMS
I Claim,
1. A domestic solar power heater system, comprising:
a. a solar heat collector (1) for capturing solar radiation and
transferring heat;
b. a heat transfer element (2) thermally coupled to said solar
collector configured to transfer heat from the solar heat collector;
c. A primary oil tank (3) connected to the solar heat collector,
containing a heat-transfer medium i.e., oil, configured to receive thermal energy;
d. a secondary oil tank (5) partially filled with oil, positioned above the primary oil tank to retain the heat
e. one or more thermally insulated connecting tubes (4) extending
between and fluidly connecting said primary oil tank and said
secondary oil tank;
f. a water tank (6) positioned within the secondary oil tank,
configured to receive heat from the secondary oil tank, and
g. a water inlet (8) and outlet (7) configured to circulate water through the water tank.
wherein said system is configured to provide continuous hot water supply through thermal expansion and contraction of oil between said primary oil tank and said secondary oil tank.
2. The system as claimed in claim 1a, wherein the said solar heat collector is a flat plate solar constructed of high thermal conductivity material;
3. The system as claimed in claim 1b, wherein the heat transfer medium is a low viscosity, non-flammable, oily medium having a boiling point of 15 100°C or more, capable of thermal expansion according to temperature rise.
4. The system as claimed in claim 1c, wherein the primary oil tank designed as a cylindrical vessel constructed from high thermal conductivity materials to promote uniform heat distribution.
5. The system as claimed in claim 1d, wherein the secondary oil tank comprises a multi-chamber internal design with baffles preventing thermal stratification and an integrated heat exchange surface maximizing contact with said water tank;
6. The system as claimed in claim 1e, wherein the connecting tubes are designed to facilitate thermal expansion-driven movement of oil from the primary tank to the secondary tank and are thermally insulated to prevent heat loss during transfer and are inclined upwardly to allow natural convection flow of the heated oil.
7. The system as claimed in claim 1f, where in the water tank arranged within the secondary oil tank made of conductive material such as copper, configured to maintain water temperature through prolonged heat retention in the secondary oil tank.
8. Method for heating water using a domestic solar water heater system as claimed in claim 1,
a. collecting solar heat using a solar heat collector;
b. transferring said solar heat to oil contained in a primary oil tank through a heat transfer element;
c. allowing said heated oil to expand and flow upward through
connecting tubes to a secondary oil tank;
d. heating oil contained in said secondary oil tank using said expanded oil from said primary oil tank;
e. heating water contained in a water tank disposed within said
secondary oil tank using heat from said heated oil in said secondary oil tank; and
f. maintaining said heated oil in said secondary oil tank in an isolated state when oil in said primary oil tank cools and contracts after sunset.

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