SOLAR WATER HEATER

This presentation deals with solar water heaters.

There are two categories (passive, active)

There are two common types (conventional, vacuum tubes); uncommon - reflective

Any of these may operate on one of two principles : direct or heat exchange.

objective

A B

C D

CXC CSEC PHYSICS SYLLABUSSECTION C : THERMAL PHYSICS AND KINETIC THEORY

Objective 4.6 b : Students should be able to relate the principle of thermal energy transfer to the design of devices – solar water heater.

Our Focus : Conventional passive direct. Pre-requisite : (a) Thermal transfer

( b) Absorption of radiation lesson

Conduction

(solids) Convection

(fluids)Radiation

(vacuum)

Flat black

objects

PASSIVE : ACTIVE

Passive : Outlet from collector is lower than inlet of hot water inlet to storage tank.No pump required.

Active : Outlet from collector is higher than hot water inlet to storage tank.Pump required.

More passive

More active

EXAMPLES OF PASSIVE

To active slide

EXAMPLES OF ACTIVE

CONVENTIONAL : VACUUM TUBE

More conventional

More vacuum tubes

CONVENTIONAL

To vacuum tubes

MORE VACUUM TUBE

REFLECTIVE

DIRECT : HEAT EXCHANGE

OUR FOCUS : CONVENTIONAL PASSIVE DIRECT

DETAILS OF HOW IT WORKS

A : How heat reaches Earth from SunB : Why the glass?C : Copper tubes with heat sinks, painted flat black.D1 – D2 : Collector slanted with outlet at upper end and inlet at lower end.E : Insulated storage tank.F : Hot water outlet from tank to house at top of tank.

critical thinking

CRITICAL THINKING

State two correct features of the above diagram and one bad feature.

Please pause the video now, think about this for a few minutes, and then continue to find out how your answers compare with mine.

DO YOU THINK THIS SYSTEM WILL WORK?

questions

Please pause the video now, think about this for a few minutes, and then continue to find out how your answers compare with mine.

QUESTIONS: 1: By what method does heat from the sun reach

Earth? Radiation 2. What effect does the glass of the collector

produce? Greenhouse effect 3. Why is everything in the collector painted flat

back? Flat black – best absorber of infrared radiation 4. What is the process by which heat is

transferred through the walls of the copper tubing? Conduction

More questions

QUESTIONS 5. In the passive system, by what process does

the water flow through the tubes and into the storage tank?

Convection 6. Why would 4 mm PVC (plastic) be a better

material for the inside of the storage tank than 1 mm steel (assuming that both have the required strength)?

4 mm PVC is a better insulator. 7. Why is the hot water pipe to the home

connected to the top of the storage tank? The hot water, being less dense, floats at the top.

passive

resources

RESOURCES:

http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12850

http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm

http://chinasolarwaterheater.blog.com/working-principle-of-solar-water-heater.html/

http://www.motherearthnews.com/Renewable-Energy/1979-09-01/A-Homemade-Solar-Water-Heater.aspx

http://www.youtube.com/watch?v=oBpKPes3cEE

passive

Conventional passive

Please visit http://csecphysics.weebly.com to view this presentation and to download a copy of the accompanying brochure or this PowerPoint presentation. To take the quiz, you will need an access code (available to my students).

EXAMPLES OF PASSIVE

To active slide

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