Description:TECHNICAL FIELD
The present disclosure generally relates to space heating units, and in particular relates to a space heating system that utilizes solar energy for heating commercial or household spaces, especially spaces located at higher altitudes during winters and nights.
BACKGROUND OF THE DISCLOSURE AND PRIOR ARTS
All over the world there is a drive to minimize use of fossil fuels for generating energy, reducing carbon footprint by reducing production of harmful gases, and providing environment friendly and sustainable solutions, in order to fill the gap left by the non-use of fossil fuels. In view of this various equipment manufacturers have developed alternative solutions for achieving the primary objective, for example for private transportation vehicles that run on rechargeable Li-ion batteries have been developed, equipment like solar cells and wind mills have been developed to harness solar energy and wind energy, respectively, for powering households or commercial spaces.
Solar space heating is one of the more intuitive use of solar thermal energy by using the sun’s heat to subsequently heat spaces within buildings. The technologies within space heating can be separated into two distinct categories: passive and active. Passive solar heating systems make use of the building components to collect, store, and distribute solar heat gains to reduce the demand for space heating. Active heating captures sunlight, either as heat or electricity, to augment heating systems, while passive heating captures heat from the sun as it comes into home through windows, roofs and walls to heat objects in the room. Active space heating uses large flat-plate or evacuated tube collectors on a roof to absorb the thermal energy and redistribute the heated fluid. In this product we are using active mode of space heating. However, passive solar heating is less effective than active solar heating as in passive solar heating solar energy is only absorbed and not enhanced while active solar heating takes the help of mechanical equipment that in turn enhances the conversion rate of solar energy to heat.
Phase change materials (PCMs) provide much higher energy storage densities and the heat is stored and released at an almost constant temperature. PCMs can be used for both active and passive space heating and cooling systems. In passive systems, PCMs can be encapsulated in building materials such as concrete, gypsum wallboard, in the ceiling or floor to increase their thermal storage capacity. In active space heating a thermal storage unit using phase change material or PCM can be employed. The PCM are mainly of three types organic (paraffin and non-paraffin), inorganic (salt hydrates and metallic alloys), and eutectic (mixture of two or more PCM components: organic, inorganic, and both).
However, due to certain advantages as compared to other PCMs such as safety, reliability, predictability, cost-effectiveness, very high latent heats and non-corrosive nature of paraffin wax, it is most preferred in case of storing thermal energy.
For example, paraffin wax has been employed as PCM in European patent publication (machine translated) 2896898, wherein facade elements for air conditioning a building with latent heat storage modules, corresponding latent heat storage modules and a method for air conditioning a building using such facade elements. However, usage of façade elements utilizing wax as PCM is not cost-effective due to arrangement of façade elements outside air-conditioning, which also affects heat exchanging capability of the air conditioning system.
Therefore, there exists a need of a space heating system that employs paraffin wax for storing thermal energy trapped by solar collector from the heat component of sun rays and releasing the stored thermal energy on demand, in an efficient and cost-effective manner.
Thus, the present disclosure is directed to overcome one or more of the problems as set forth above. In particular, there is a need of a space heating system, which address the aforementioned drawbacks.
OBJECTIVE OF THE DISCLOSURE
One objective of the present disclosure is to provide active solar space heating system.
Another object of the invention is to provide an efficient and cost-effective paraffin wax based thermal storage system for solar space heating.
Yet another object of the present disclosure is to provide solar space heating customized to meet the requirement of 10 kWh of thermal energy for heating a space volume of 10*10*10 cubic feet during non-sunshine hours.
Further, an object of the present disclosure is to provide solar space heating system which is easy to install and maintain.
SUMMARY OF THE DISCLOSURE
In a first aspect of the present disclosure a solar space heating system is disclosed. The solar space heating system includes a solar thermal collector with a series of evacuated tube collector to harvest solar energy, a PCM based thermal energy storage in fluid communication with the solar thermal collector to store thermal energy, a radiator in fluid communication with the thermal energy storage to heat the required space, a water circulation unit arranged in a plumbing panel to circulate water via a flexible hose to the solar thermal connector, the thermal energy storage and the radiator . The present invention advantageously facilitates an innovative and efficient solar space heating system that utilizes solar energy for heating commercial or household spaces, especially spaces located at higher altitudes during winters and nights
The present disclosure further discloses a method adapted for space heating with the solar space heating system. The method includes circulating water at 60°C in the solar thermal collector via a circulation pump during sunny hours, heating circulated water in the solar thermal collector from 60°C to 70°C through absorbed solar radiations by the evacuated tubes in the solar thermal collector configured with heat pipes; circulating hot water at 70°C coming out from the solar thermal collector to the thermal energy storage , the hot water at 70°C exchanges heat with the paraffin wax phase change material in the thermal energy storage, converts paraffin wax to molten state and gets cooled to 60°C; and circulating water at 40°C to the thermal energy storage during night hours, employing heat of paraffin wax in molten state in the thermal energy storage to heat water from 40°C to 50°C, circulating heated water at 50°C to the radiator, passing it through the small tubes in the radiator to heat the cold air drawn by the fan of the radiator for heating the required space.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
FIG. 1 shows a perspective view of a space heating system, in accordance with a preferred embodiment of the present disclosure.
FIG. 2 shows a process flow diagram of solar space heating system during day time.
FIG.3shows process flow diagram of solar space heating system during night hours.
DETAILED DESCRIPTION OF THE DISCLOSURE
Provided below is a non-limiting exemplary embodiment of the present disclosure and a reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Wherever possible, corresponding or similar reference numbers will be used throughout the drawings to refer to the same or corresponding parts. Moreover, references to various elements described herein, are made collectively or individually when there may be more than one element of the same type. However, such references are merely exemplary in nature. It may be noted that any reference to elements in the singular may also be construed to relate to the plural and vice versa without limiting the scope of the disclosure to the exact number or type of such elements unless set forth explicitly in the appended claim.
The present disclosure provides for an innovative active solar space heating system (100) comprising a solar thermal collector (102) with a series of evacuated tube collectors employed to harvest suns energy, a thermal energy storage (106) with paraffin wax as a phase change material to store thermal energy and a radiator (110) to dissipate heat to required space. The solar space heating system (100) is designed to transfer heat using water or ethylene glycol.
Referring to FIG.1, Fig 1 illustrates a process and instrumentation diagram of a solar space heating system in accordance with a preferred embodiment of the present disclosure. FIG. 1 shows the solar space heating system (100) provided with a solar thermal collector (102), a thermal energy storage (106), a radiator (110), and a water circulation unit. The system (100) is provided with the solar thermal collector (102) having evacuated tube collectors with a heat pipe configuration employed to harvest the suns energy, the evacuated tube collectors are provided with absorber coating to collect solar radiations and transfer it to heat pipes within using aluminium fins. In an embodiment of the present disclosure the diameter of the evacuated tube is 0.047m with a length of 1.8m, there are four headers (104) of solar collectors (102) with preferably twenty evacuated tube collectors with heat pipe, wherein collector area is 6.75 m2 and diameter of the evacuated tube is 0.047m with a length of 1.8m. The header (104) consists of a rectangular section of dimension 50 mm * 25 mm with heat pipes inserted to it in order to increase the heat transfer area.
FIG 1, further shows a PCM based thermal energy storage (106), the PCM based thermal energy storage (106) employs a copper heat exchanger and is provided with an insulated rectangular tank with dimensions 710 mm X 550 mm X 950 mm having a rock wool insulation and a 50mm thick aluminium cladding. In an embodiment of the present disclosure the heat transfer area required to store 10 kWh thermal energy in PCM is 17 sq. m, the required area has been arranged in the form of a copper tube having outer diameter 15.87 mm and assumed PCM thickness of 21 mm/m length of the tube. A total of 93 m tube length has been arranged in such a fashion with liquid PCM on the outer side of the tubes, the tubes are arranged in modular fashion inside the insulated rectangular tank. In an embodiment of the present disclosure the phase changing material used for the thermal energy storage (106) is a Paraffin wax because of its low melting point and high latent heat storage capacity. The PCM material has a melting temperature of 57°C and latent heat value of 176 kJ/kg.
A water circulation unit in solar space heating as shown in FIG.1, 2 and 3 comprises of pump (P), solenoid valves (S) for switching over between daytime and night time operation., hand operated valves for isolation, temperature gauges, pressure gauges, check valve (C) and flow meters for parameters measurement. The components for water circulation have been arranged in a plumbing panel as per requirement in process and instrumentation diagram in FIG.1.The solar thermal collectors (102), the thermal energy storage (106) and the radiator (110) are connected to the plumbing panel through a flexible hoses with hose insulation for avoiding heat loss, a circulation pump (P) of flow rate of 6 LPM and head 8m circulates water through the solar thermal collector (102), the thermal energy storage (106) and the radiator (110). The close loop system (100) is pressurised at 1.5 bar and an expansion tank (108) of 24 litre volume is provided to accommodate volume changes in hot water due to heating/cooling and to maintain the pressure in the system. In an embodiment of the present disclosure, the radiator (110) is a finned type heat dissipater with a fan employing forced convection mode of heat transfer to transfer the heat from hot water to room air.
FIG 2 shows a process flow diagram (200) of solar space heating system during day time. During solar hours, water at 60°C is made to flow inside the solar thermal collector system (102) with the help of the circulation pump (P), where it gets heated to maximum 70°C.The absorber coating on the evacuated tubes collects the solar radiations and transfers it to the aluminium fins inside. The absorbed heat is then further transferred through aluminium fins to the heat pipes where the water droplets get vaporised and converts to steam, the steam is used for heating the water flowing through the headers (104) provided with proper insulation to prevent any loss. As shown in Fig 2, the hot water coming out from the solar thermal collector (102) goes in to the thermal energy storage (106). In the thermal energy storage (106), the paraffin wax as the phase change material (PCM) gets melted by heat exchange with the hot water at 70°C, the water temperature comes down to 60°C and is again passed to the solar thermal collector (102).
FIG 3 shows process flow diagram (300) of solar space heating system during night hours. During night hours water at 40°C is circulated to the thermal energy storage (106) and is heated to 50°C by employing heat of molten state PCM paraffin wax, this heated water at 50°C then flows in to a heat dissipater unit, i.e., the radiator (110) where forced convection mode of heat transfer is employed to transfer the heat from hot water to room air, the radiator (110) is equipped with many small tubes having a honeycomb of fins and a fan to draw cool air from outside to the radiator tubes, during night hours the hot water at 50°C is made to pass through the small tubes in the radiator (110) , which thereby heats the cold air drawn by the fan eventually heating up the required space. After the heat exchange in the radiator (110), water cools down to 40°C and is gain circulated in to thermal energy storage system (106) through the centrifugal pump (P).
In an embodiment of the present disclosure, the heat stored in the paraffin wax can be dissipated at a rate to sustain for 10 hours during night to maintain a temperature difference of 10°C for room size of 10*10*10 cubic feet.
Example
The following example is given by way of illustration of the present disclosure and should not be construed to limit the scope of present disclosure. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present disclosure.
a) In the present disclosure the thermal energy requirement is 1kW for 10 hours of operation (i.e., 10 kWh) needs to be supplied by the solar collectors. Solar field is sized to produce the required energy at average GHI of 4 kWh/sq. m / day.
Heat required in the room = 1 kW
Hours of Operation = 10 hours
Total Energy to heat the room = 10 kWh
Average Solar Radiation = 4 kWh/ sq. m/ day
Solar Efficiency = 40%
Solar Area required = 6.25 sq. m
The diameter of the evacuated tube is 0.047m with a length of 1.8m. 20 sets of evacuated tubes are connected to a header. 4 set of such headers are used to form the solar collector system.
The header consists of a rectangular section of dimension 50 mm * 25 mm with heat pipes inserted to it in order to increase the heat transfer area. Water flows through these headers and over the heat pipe to transfer the heat collected from solar. The velocity of flow over the heat pipes is 0.15m/s.
b) In the present disclosure Paraffin wax is used as the PCM material due to its low melting point, low cost and high latent heat. PCM material has a melting temperature of 57°C and latent heat value of 176 kJ/kg. Water at 70°C flows inside the tubes and melts the paraffin wax. This stored thermal energy is used in the night hours to raise the temperature of water at 40°C to 50°C.
Heat transfer area required to store 10 kWh thermal energy in PCM is 17 sq. m. The required area has been arranged in the form of copper coil having outer diameter 15.87 mm and assumed PCM thickness of 21 mm/m length of tube. A total of 93 m tube length has been arranged in such a fashion with liquid PCM on the outer side of tubes. The tubes are arranged in modular fashion inside a tank of dimensions 710mm * 550mm * 950mm.
In an embodiment of the present disclosure, following charging cycle is obtained from PCM heat exchanger –
CHARGING Cycle of PCM during day time
Molten temperature of Paraffin Wax = 57 °C
Inlet temperature of Water = 40 °C
Outlet temperature of Water = 50 °C
? T (LMTD) = 11.27 °C
DISCHARGING Cycle of PCM during night time
Molten temperature of Paraffin Wax = 57 °C
Inlet temperature of Water = 65 °C
Outlet temperature of Water = 75 °C
? T (LMTD) = 12.33 °C
In view of the above, it can be observed that the heat stored in the paraffin wax can be dissipated at such a rate to sustain for 10 hours during night to maintain a temperature difference of 10°C for room size of 10*10*10 cubic feet
c) In the present disclosure Forced convection mode of heat transfer is employed to transfer the heat from hot water to room air with the parameters
Flow rate of hot water: 100 kg/hour (maximum)
Heat Transfer area: 0.24 sq. m
Flow rate of fan: 10 cfm (operation)
The above parameters provide for an active solar space heating customized to meet the requirements of 10 kWh of thermal energy for heating a space of volume of 10*10*10 cubic feet during non-sunshine hours.
Advantages:
The solar space heating system enables sustained solar space heating for 10 hours during night to maintain a temperature difference of 10°C for room size of 10*10*10 cubic feet. The paraffin wax used a Phase change material helps in storing more thermal energy in a cost-effective manner. It provides for an efficient solar space heating system which is easy to install and maintain.
Industrial applicability:
The disclosed solar space heating system in accordance with various embodiments illustrated from FIG. 1 to FIG. 3 of the present disclosure finds its application in air conditioning systems used for space heating of buildings or commercial spaces at high altitudes at nights or winter season.
While aspects of the present invention have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by modification of the disclosed device without departing from the scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present invention as determined based upon claims and any equivalents thereof.
List of reference numerals and characters:
Elements/Features Reference Numeral
Solar Space Heating system 100
Solar thermal collector 102
Headers 104
Thermal Energy storage 106
Expansion Tank 108
Radiator 110
Solenoid Valve S
Centrifugal Pump P
Check valve C

, Claims:WE CLAIM:

1. A Solar space heating system (100) comprising:
- a solar thermal collector (102) with a series of evacuated tube collector to harvest solar energy;
- a PCM based thermal energy storage (106) in fluid communication with the solar thermal collector (102) to store thermal energy;
- a radiator (110) in fluid communication with the thermal energy storage (106) to heat the required space;
- a water circulation unit arranged in a plumbing panel to circulate water via a flexible hose to the solar thermal connector (102), the thermal energy storage (106) and the radiator (110).
2. The Solar space heating system (100) as claimed in claim 1, wherein the evacuated tube collector of the solar thermal collector (102) has absorber coating to collect solar radiations and transfer it to heat pipes within, by aluminium fins.
3. The solar space heating system (100) as claimed in claim 1, wherein the diameter of each evacuated tube is 0.047m with a length of 1.8m.
4. The Solar space heating system (100) as claimed in claim 1, wherein at least one header (104) of the solar thermal collector (102) is equipped with plurality of evacuated tube collectors configured with the heat pipe.
5. The solar space heating system (100) as claimed in claim 4, wherein the at least one header (104) of the solar thermal collector (102) has a rectangular section of 50 mm * 25 mm with heat pipes inserted to it in order to increase the heat transfer area.
6. The solar space heating system (100) as claimed in claim 1, wherein the PCM based thermal energy storage (106) is a copper heat exchanger with an insulated rectangular tank.
7. The solar space heating system (100) as claimed in claim 6, wherein the rectangular tank of the PCM based thermal energy storage (106) is provided with a rock wool insulation and an aluminium cladding.
8. The solar space heating system (100) as claimed in claim 6, wherein the copper heat exchanger has a copper tube having outer diameter 15.87 mm with assumed PCM thickness of 21 mm/m along the length of tube.
9. The solar space heating system (100) as claimed in claim 1, wherein the phase change material in the PCM based thermal energy storage (106) is a Paraffin wax.
10. The solar space heating system (100) as claimed in claim 1, wherein the radiator (110) is a finned type heat dissipater with a fan.
11. The solar space heating system (100) as claimed in claim 1, wherein an expansion tank (108) is employed to accommodate volume changes in hot water and to maintain pressure in the system (100).
12. The solar space heating system (100) as claimed in claim 1, wherein a water circulation unit includes a pump (P), solenoid valves (S), hand operated valves, temperature gauges, pressure gauges, check valve (C) and flow meters.
13. A method for heating a space with the solar space heating system (100) as claimed in claims 1-12, the method comprising:
- circulating water at 60°C in a solar thermal collector (102) during sunny hours;
- heating circulated water in the solar thermal collector (102) from 60°C to 70°C through absorbed solar radiations by a series of evacuated tubes of the solar thermal collector (102) configured with heat pipes;
- circulating hot water coming out from the solar thermal collector (102) to a thermal energy storage (106),
- converting a phase change material stored in the thermal energy storage (106) to molten state by exchange of heat between the hot water and the phase change material, and cooling the phase change material to 60°C;
- storing water coming out of the thermal energy storage (106) in an expansion tank (108);
- circulating water stored in the expansion tank (108) at 40°C to the thermal energy storage (106) during night hours;
- employing heat of the phase change material to heat water from 40°C to 50°C; and
- circulating heated water at 50°C to the radiator (110) by passing it through the small tubes in the radiator (110) to exchange heat with cold air drawn by a fan of the radiator (110) for heating a space.