Presentation on

“SOLAR WATER HEATER”

Himanshu KumarM.Tech. (First Year)

Department of Renewable Energy Engineering

IntroductionIndia is blessed with solar energy in abundance at no

cost.India is having high solar insolation of about 4.4-6.6

KWh/ /day for an average of 280 sunny days and most of that resource has been left untapped.

The highest annual global radiation is received in Rajasthan, northern Gujarat, Tamilnadu and parts of Ladakh region, the parts of Andhra Pradesh, Maharashtra, Madhya Pradesh, Karnataka also receive fairly large amount of radiation.

m²

Average Solar Insolation Data

One of the popular cost-effective devices that harness the solar energy is Solar Water Heating System (SWHS).

Solar water heating system is a commercially viable and technologically mature product, is existing in country for many years with enormous potential.

Solar water heating is the direct use of solar energy that has been practiced most extensively in the last two decades.

The use of solar energy for heating water in many respects quite similar to its use for heating buildings.

Scope in IndiaIndia has a varying climate extending from

extreme to moderate due to its unique geographical features.

Wood or biomass is used for heating and in urban areas electricity or fossil fuels are used for this purpose. This practice is either expensive or degrades the environment.

Solar water heating system can be a suitable alternative to meet the growing demand of hot water in the country without exerting further pressure on electricity or cutting of forest trees from the forest areas.

The SWHS has the potential to save millions in energy costs in our country.

Why Solar Water Heating?

Electricity or natural gas water heating Solar Water Heating

Pay 100% of hot water heating bill Eliminate up to 80% of bill

Surrender to continued rising energy costsEnjoy a constant increasing savings in non-taxable income

Add zero equity to your homeIncrease home’s value through your investment

Make monthly payments for hot water with no return on investment

Profit from an income generation opportunity that produces a monthly positive cash flow

Contribute to air pollution and add heavy toxic metals into the air and water

Utilize a safe, free, non-polluting energy source—the sun

Basic Components of SWHSFlat plate collectorInsulated water storage tankWell insulated pipes connecting flat plate

collector and to the storage tankAuxiliary heater ( for cloudy days)Control of the system

Flat Plate collector It is a device which is used to convert solar

energy into thermal energy & consists of the following components:

Absorber

Transparent cover

Insulation

Tubes, Fins

Frame

Tilting angle: 0.9×latitude of the place

Insulated water storage tankPurpose: A hot water storage tank (also hot water

tank, thermal storage tank, hot water thermal storage unit, heat storage

tank) is a water tank that is used for storing hot water for space heating or domestic use

Material: Mild steel or Steel(Density:7850 kg/m³, Thermal conductivity: 47.6 w/m ºc)

Insulation:The most common type of water heater blanket is fiberglass insulation with

a  vinyl film on the outside.

Properties of fiberglass lightweight; tight structure ; resistance to corrosive attacks; superior shock and wear resistance; cheap maintenance in service; damage and breakage resistance; at temperatures below zero it doesn’t become

slippery or covered with ice; hardly bendable material; low thermal conductivity .

Properties of Vinyl

Vinyl is resistant to moisture and humidity; It is a very strong and durable plastic

materialVinyl can be manufactured in variety of

colors, both transparent and solid;It is low cost materialIt can easily be recycled.

Cut-view of storage tank

Anti-corrosion material for tank

Material Properties

Epoxy, air dry Cost-effective, corrosion resistant coating

Epoxy, thermal cure Excellent impact resistance, plus corrosion and abrasion resistance

Inorganic zincCorrosion and weathering protection for steel

Molybdenum disulfideFriction protection for high pressure loads

Insulated pipes Purpose- To transport fluid to the lower header

of the collector (cold water) to the top

of the storage tank (hot water).

Material- Galvanized Iron sheet.

Properties->This material is tough and strong,

> It can be fairly easily worked (bent or formed),

  > It lasts a long time, too, because the zinc coating (the galvanizing)

inhibits corrosion quite well.

Properties of glass wool

Used as insulation material for pipe connectionDensity : 10-100 kg/m³Average fiber dia. : 5.5 µmWater content : ≤ 1%Shrinking temperature: ≥ 250 °C Thermal conductivity: 0.038–0.06 w/mºK Non combustible in nature

Auxiliary heater ( for cloudy days)

Purpose: An auxiliary heater is attached in the tank to

provide supplement heat during cloudy days. Freezing protection during winter

season. Act as heat exchanger.

System control

Purpose: To protect the system from damage and for efficient working.

Sensor ( In case of forced circulation system) Control valveMaintain the height between top of the collector

to the bottom of the storage tank 0.3 -0.4 m to avoid reverse flow during night( in case of natural convection system).

Working Principle of SWHS

Either by gravity flow or forced circulation, water from the cold-water tank enters the solar tank and fills it up.

The cold water from the solar tank in turn flows in the bottom header pipe of the absorber, and into the copper tubes , until all the absorber tubes and the header at the top of the absorber are full.

When the sun rises to a certain level, its energy, which falls on the absorber fins and tubes, begins heating the water contained therein.

The heated water being lighter than the cold water rises and via the top header pipe of the absorber, flows into the top of the solar tank. 

Types of solar water heating system

The solar water heating systems are of two categories:

1) Closed loop system.

2) Open loop system

Close loop system:

In the closed loop system, heat exchangers are installed to protect the system from hard water obtained from bore wells or freezing temperatures in the cold regions.

The open loop system has two categories :

1) Natural circulation system (Thermosyphon).

2) Forced circulation system.

Natural Circulation SWHSWork on the principle of

thermosyphon effect.As water from the lower of

the tank enter into collector plate heated up and rises in the copper tube column.

Hot water enter at the top of the storage tank via upper header of the collector.

Forced Circulation SWHSSource of cold water

supply can be at any level as water shall be pumped into the system.

It is recommended to use where source of cold water is not placed at sufficient height and attain sufficient water pressure and to maintain uniform water temperature.

Salient Features of SWHS

Around 60–80˚C temperature can be attained depending on solar radiation, weather conditions and solar collector system efficiency

Hot water for homes, hostels, hotels, hospitals, restaurants, dairies, industries etc.

Can be installed on roof-tops, building terrace and open ground where there is no shading, south orientation of collectors and over-head tank above SWH system

SWH system generates hot water on clear sunny days (maximum), partially clouded (moderate) but not in rainy or heavy overcast day

Only soft and potable water can be used Stainless Steel is used for small tanks whereas Mild

Steel tanks with anticorrosion coating inside are used for large tanks

Solar water heaters (SWHs) of 100-300 litres capacity are suited for domestic application.

Larger systems can be used in restaurants, guest houses, hotels, hospitals, industries etc.

The optimum size of a solar water heater system to meet a particular service hot water need (load) depends on the followings:

Investment required in the solar system Coast of alternative (auxiliary energy) Collector orientation Climate and Temperature of cold water supply

Load and Sizing of the System

Heat storage in the system

Where,

Q= Heat storage in water (watt)

m= mass flow (kg/second)

c = Specific heat of water(1 kcal/kg ˚C or 4.187 KJ/kg ˚ k)

T1= Hot water temperature (˚C)

T2= Cold water temperature (˚C)

Collector Area

Average solar insolation: 5000 kcal/m² dayCollector efficiency: 30 %Hot water demand per day: 100 litresTape water temperature: 15 ˚CHot water temperature: 55 ˚C

= 5000×30/100= 1500 kcal/m² day

Specific heat of water = 1 kcal/kg˚c

Thus,

Q= 100×1×(55-15) = 40×10² kcal

Protection against freezingThe collector may be designed to be drained

during times when they are not operating or when freezing is a possibility.

Anti-freezing solution( Ethylene glycol) can be used in the collector , with heat exchanger to transfer energy to the water.

The collector may be covered with movable insulation.

Through the circulation of warm liquid from the storage tank or the operating of electric heat strips attached to the absorber.

Advantages: These systems use solar energy which is a free and

renewable source of energy. In sunny and warm places with high insolation

values solar water heating system are very cost effective.  

Relatively good payback period. These systems have low maintenance costs.   Some countries even offer the option of leasing

solar water heating systems which can significantly decrease initial costs. 

Disadvantages: The main disadvantage of solar water heating

systems is relatively high upfront costs.  In most areas they will require electrical or gas or

other fuel backup during the winter period.  Payback times can vary greatly mostly due to

regional sun (the more insolation, the shorter payback period). 

Relatively low efficiency of passive solar water heating systems. 

They require excellent overheating and freeze protection.

Application of SWHS

Bathing. Laundry application in hotels, hospitals, hostels. Cooking (Pre-Heating of water helps in

reduction of use of fuel). Various industrial applications.

Solar water heater for hotel application Hubei, China

Swimming pool solar water heater

Conclusion

Source is abundant and inexhaustible in nature so enjoy with free cost of energy.

Cheaper cost as compare to other heating system.

Due to constraints on energy availability, it is most suitable.

Keep the environment clean.