INTRODUCTIONDIRECT GAIN SYSTEM INDIRECT GAIN SYSTEM - Trombe wall, Roof PondISOLATED GAIN SYSTEM – Sunspace(Solarium) COMPARISON OF PASSIVE SOLAR HEATING SYSTEMSYSTEM COMBINATIONHYBRID SYSTEMROOF RADIATION TRAP

PASSIVE HYBRID ACTIVE

Energy Collection and Storage is by NATURAL means

Energy Collection and Storage can be by NATURAL means

Energy Collection and Storage is by Forced means

Energy distribution is by natural means

Energy distribution from COLLECTOR to STORAGE to LIVING SPACE is by mechanical means

Energy distribution is by forced

The system mostly works without External Power

The system uses External Power

The system works only with External Power

Daylight is extensively used

Daylight is extensively used

Less use of Daylight

Passive heating and cooling can be inherent in the building construction

Passive Heating and cooling can be inherent in the building construction

Heating and cooling systems and their controls are not an integral part of the building

Advanced passive heating techniques are used by architects in building design to achieve thermal comfort conditions in cold climate.

Passive solar heating systems can be broadly classified as: DIRECT GAIN SYSTEM INDIRECT GAIN SYSTEM – TROMBE WALL, ROOF POND ISOLATED GAIN SYSTEM – SUNSPACE (SOLARIUM),

Greenhouse SYSTEM COMBINATIONS HYBRID SYSTEMS

Most common passive solar solution

SUN----LIVING SPACE ----STORAGE MASS

Actual Living space is directly heated by the sun and serves as a LIVE-IN Collector

In this system, sunlight enters rooms through windows, warming the interior space.

The glazing system is generally located on the southern side to receive maximum sunlight during winter (in the northern hemisphere).

The glazing system is usually double-glazed, with insulating curtains to reduce heat loss during night. South-facing glass admits solar energy into the building, where it strikes thermal storage materials such as floors or walls made of adobe, brick, concrete, stone, or water.

The direct gain system uses 60-75% of the sun’s energy striking the windows.

The interior thermal mass tempers the intensity of heat during the day by absorbing heat. At night, the thermal mass radiatesheat into the living space, thus warming the spaces.

Direct gain can be achieved by various forms of openings such as clerestories, skylight windows, etc. designed for the required heating. Direct gain systems have some limitations.

They cause large temperature savings (typically 10 °C) because of large variations in input of solar energy. Strong sunlight, glare, and ultraviolet degradation of the house material are some disadvantages of direct gain systems.

However, being relatively simple to construct and inexpensive, they are by far the most common systems used world wide.

S. No. REQUIREMENTS VARIATIONS

1 A large South facing glazed (Collector) area to admit the maximum useful radiation

Storage on Exterior Building walls

2 Living Space exposed directly behind the collector

Storage on internal walls

3 A Floor/wall storage mass to store solar heat for longer time heating

Storage on Floor

4 A method for isolating storage from exterior Climatic Conditions

Free standing Masses on Floor

5 A proper Sunshade to prevent unwanted heat Gain

6 A proper Insulation on the glazed collectorarea to prevent unwanted Heat Loss

In an indirect gain system, thermal mass is located between the sun and the living space.

The thermal mass absorbs the sunlight that strikes it and transfers it to the living space.

The indirect gain system uses 30-45% of the sun’s energy striking the glass adjoining the

thermal mass.

Range of storage Materials includes CONCRETE, ADOBE, STONE, BRICK, AND even WATER

TROMBE WALLS

1. A trombe wall is a thermally massive wall with vents provided at the

top and bottom.

2. It may be made of concrete, masonry, adobe, and is usually located

on the southern side (in the northern hemisphere) of a building in

order to maximize solar gains.

3. The outer surface of the wall is usually painted black for maximizing

absorption and the wall is directly placed behind glazing with an air

gap in between.

4. Solar radiation is absorbed by the wall during the day and stored as

sensible heat.

5. The air in the space between the glazing and the wall gets heated up

and enters the living spaces by convection through the vents. Cool

air from the rooms replaces this air, thus setting up a convection

current.

The vents are closed during night, and heat stored in

the wall during the day heats up the living space byconduction and radiation.

Thickness of the storage wall is between 200 mm and

450 mm, the air gap between the wall and glazing is

50-150mm, and the total area of each row of vent is

about 1% of the storage wall area. The trombe wall

should be adequately shaded for reducing summer

gains.

WATER WALLS Water walls are based on the same principle as that for

trombe walls, except that they employ water as the thermal storage material.

A water wall is a thermal storage wall made up of drums of water stacked up behind glazing. It is usually painted black to increase heat absorption.

It is more effective in reducing temperature swings, but the time lag is less.

Heat transfer through water walls is much faster than that for trombe walls.

Therefore, distribution of heat needs to be controlled if it is not immediately required for heating the building.

Buildings that work during the daytime, such as schools and offices, benefit from the rapid heat transfer in the water wall.

Overheating during summer may be prevented by using suitable shading devices.

A large south-facing Glazed area to admit Maximum useful radiation

A storage Mass (Masonry, water wall etc) directly behind the collector

A provision of External movable insulation to reduce wasteful heat loss during night in winters

A provision of preventing unwanted heating of the storage mass by shading the glazed area in summer

A provision for suitable vent at the top of glazed area to provide induced ventilation for summer cooling of the living space

A thermal Storage Roof In this roof pond system, water is stored in black

plastic bags on a metal deck roof and during a winter day the sun heats the water bags

The heat is quickly conducted down and radiated from the ceiling into the living space

At night, movable insulation covers the water to keep the heat from being lost to the night sky

Not only heats passively in winter but also passive cooling in the summer.

DISADVANTAGE Weight of the water and potential

water leakage No one has been able to develop a

workable, movable insulation system for the roof

Due to Cosine law, flat roofs receive less solar radiation than sloped or vertical surfaces in the winter. Higher the latitude the worse this problem

A body of water – “ROOF POND” located in the roof.

A provision to protect the pond by exterior movable insulation to reduce heat loss in winter and heat gain in summer

A provision of cover to stop loss of water due to evaporation

The system finds application when the space is in Direct thermal contact with the thermal storage.

SOLAR COLLECTION AND STORAGE are thermally isolated from the LIVING SPACES of the building

It thus allows COLLECTOR & STORAGE to function somewhat independently of the building, while the building can draw from them as its thermal requirements dictate.

SUNSPACE

A sun space or solarium is the combination of direct and indirect

gain systems.

The solar radiation heats up the sun space directly, which in turn

heats up the living space (separated from the sun space by a mass

wall) by convection and conduction through the mass wall.

In the northern hemisphere, the basic requirements of buildings

heated by sun space are (a) a glazed southfacing collector space

attached yet separated from the building and (b) living space

separated from the sun space by a thermal storage wall.

Sunspaces may be used as winter gardens adjacent to the living

space.

A provision of “SUNSPACE” to collect solar energy. This space is isolated from the living space

A provision to thermally link sun-space to storage mass for heat retention and distribution

The size of the sunspace can be variable in size. It may extend upto full size of the south exposure

A provision of movable insulation to prevent unnecessary heat losses on winter nights or cloudy days

A provision of shade to prevent overheating of glazed spaces during the summer.

ADVANTAGE DISADVANTAGE

Promotes the use of large windows.

Least expensive

Most efficient

Effectively used clearstories, daylighting and

heating can be combined ,which makes it

appropriate for schools, small offices etc.

Very flexible and best when total glazing area

is small

Too much light ,which can cause

glare and fading of colours

Thermal-storage floors must not be

covered with carpets

Only few and small paintings can

be hung on thermal mass walls.

Over heating can occur if

precautions not taken.

Fairly large temperature swings

must be tolerated.(10*F)

Gives high level of thermal comfort

Good in conjunction with direct gain to

limit lighting levels

Medium cost

Good for large heating load

More expensive than direct gain

Less glazing available for views

and day lighting

Not good for very cloudy

climate

Avery attractive amenity

Extra living space

Can function as greenhouse

Most expensive

Least efficient

Prof. B. Givoni developed the Roof Radiation trap System

The glazing on the roof is tilted to maximize winter collection at any latitude (Tilt = latitude + 15o)

After passing through the glazing, the solar radiation is absorbed by the black painted concrete ceiling slab.

The building is heated by radiation from the ceiling. The sloped roof is well insulated and a movable shutter can reduce heat loss through the glass at night. This system can also be adapted for summer passive cooling

The greenhouse acts as a solar collector, building up the sun-heated air. The air circulates by natural convection to an insulated earth bed, where

it is stored and can be retrieved when needed Architect Lee Porter Butler designed this house in Tennessee for interior

climate control by natural means through cold and hot seasons Vents and dampers direct solar heated air into the rooms to warm them

or force summer heat out through the top of the house to cool it

The angle of the balcony is calculated so that the summer sun misses the house interiors. The bed of earth rock, as well as a water pool beneath the house, act as reservoirs to provide heat in winter and cool air in summer.In addition, intake vents in the earth bring air through the ducts into the house, routing it thro the house interiors for summer air cooling