INTRODUCTION• Solar Energy reaching the earth is incredible. By one calculation, 30 days of sunshine striking the Earth have the energy equivalent of the total of all the planet’s fossil fuels, both used and unused!• All chemical and radioactive polluting byproducts of the thermonuclear reactions remain behind on the sun, while only pure radiant energy reaches the Earth.
INTRODUCTION• The surface receives about 47% of the total solar energy that reaches the Earth. Only this amount is usable
Two categories of SolarEnergy• Active Solar: A method specifically designed to acquire energy from sun and move it to where needed, including:o Photovoltaic electric power generationo Solar Thermal power generationo Active solar heating using solar collectors• Passive Solar: A design of buildings that inherently takes advantage of the sun for daylighting and winter heating, and avoids solar gain in summer to minimize need for cooling.
Passive Solar• Passive solar architecture has been practiced by people living in hot regions of the world for millennia, eg. Adobe style.• A good example of contemporary passive solar architecture are Auroville
While designing• Latitude, sun path, and insolation (sunshine)• Seasonal variations in solar gain e.g. cooling or heating degree days, solar insolation, humidity• Diurnal variations in temperature• Micro-climate details related to breezes, humidity, vegetation and land contour• Obstructions / Over-shadowing - to solar gain or local cross-winds• Landscaping and interiors also play a major role.
TOPICS COVERED:• SUN CHART• SUN PATH• SHADED ENVELOPE• LIGHT PIPES• BUILDING ORIENTATION• THERMAL MASS• TROMBE WALL• SOLAR CHIMENY
SUN CHART• A Sun chart is a graph of the ecliptic of the Sun through the sky throughout the year at a particular latitude.• Most sun charts plot azimuth versus altitude throughout the days of the winter solstice and summer solstice, as well as a number of intervening days. Since the movement of the Sun is symmetrical about the solstice, it is only necessary to plot dates from one half of the year.
SUN CHART• The graph may show the entire horizon or only the half of the horizon closest to the equator. Sky view obstructions can be superimposed upon a Sun chart to obtain the insolation of a location.
SUN PATH• South orientation receives maximum solar radiation during winters which is preferable as composite climate receives severe winters. East and West receive maximum solar radiation during summer.• West is a crucial orientation because high intensity of solar radiation is received during summers.• Orientation also plays an important role with respect to wind direction.
SHADED ENVELOPE• All the elements of a building are vulnerable to heat gains. Proper shading is therefore a very important aspect in solar passive building design.SHADING OF ROOF:• Shading of roof through design features like pergolas or solar photovoltaic panels helps in reducing the incident direct solar radiation on the roof surface.
SHADING OF WINDOWS:• Incorporation of shading elements with windows help in: keeping out the sun‘s heat, block uncomfortable direct sun, and soften harsh daylight contrasts. Shading devices are therefore necessary to allow glare free natural light.• Shading devices for windows and walls moderate heat gains into the building.
SHADING OF WALLS• Shading walls from direct sun can be one of the simplest and most effective ways of reducing the heat load on a building.Impact of shaded wall:• In day time use buildings shaded east and west walls have higher energy saving potential than insulating the external walls.• The different kinds of shadings for wall are explained below:
DIFFERENT KINDS OF SHADINGDeep porches and verandas:• These are excellent at reducing the solar heat gain in a building because they completely shade the walls.•
DIFFERENT KINDS OF SHADINGSun-proof fabric covers:• For porches, or sails these can be attached to the building itself, and are a good seasonal solution.
DIFFERENT KINDS OF SHADINGVertical shading:• Vertical shading is the most advisable form of shading to cut the intensive solar heat gains for east and west walls especially in summer.
LIGHT PIPES• Light tubes or light pipes are used for transporting or distributing natural or artificial light. In their application of day lighting, they are also called as sun pipes, solar pipes, solar light pipes, or day light pipes.• They make it possible to transport daylight through thick roof structures and attics. They are easier to install in retrofit applications than skylights.
BUILDING ORIENTATION• A building must face the south in order to capture the sun’s energy.• The long side of the house should be on an east - west axis.
THERMAL MASS• A material that has thermal mass is one that has the capacity to absorb, store and release the sun’s heat energy.• Its density and levels of conductivity help to keep the internal temperature of a building stable.• Objects that have thermal mass have inherent qualities for both heating and cooling.
TROMBE WALL• The Trombe wall absorbs and radiates solar heat in the winter, while its mass keeps the house cool in the summer.• The Trombe wall is painted black to absorb the maximum amount of solar heat.
TROMBE WALL-PRINCIPLE• A Trombe wall combines the principles of thermal mass and a solarium.• A trombe wall consists of a sun-facing high thermal mass wall with vents at the top and bottom, placed behind insulated glazing with an air gap in between; together they act as a large solar thermal collector
TROMBE WALL-APPLICATION• During the day, the air between the glazing and the thermal mass wall gets heated up and flows through the vents into the interior space via convection, thus warming the interior space.• At the same time the thermal mass wall absorbs and stores the incident solar radiation.• During the night, the vents are closed and the thermal mass radiates the stored heat into the interior space through conduction and radiation.
SOLAR CHIMNEYPRINCIPLE• A solar chimney often, referred to as a thermal chimney is a way of improving the natural ventilation of buildings by using convection of air heated by passive solar energy.• In its simplest form, the solar chimney consists of a black-painted chimney, with a partly glazed surface area towards the top.
PRINCIPLE• During the day, solar energy heats the chimney and the air within it, creating an updraft of air in the chimney.• The suction created at the chimneys base can be used to ventilate and cool the building below through stack effect.
LIGHT SHELF-PRINCIPLE• A horizontal shelf positioned (usually above eye level) to reflect daylight onto the ceiling and to shield direct glare from the sky.• It will result in a more even light gradient.• This indirect light supplements and/or delays the artificial lighting requirement and thus reduces energy consumption
LIGHT SHELF-APPLICATION• A light shelf is a horizontal element installed within a window to divide it into two sections.• The light shelf is opaque, with a highly reflective upper surface and a diffusing white under surface.• Generally, the light shelf will split the window with one third of the glazing above and two thirds below.• This will allow reflection of both daylight and sunlight up on to the ceiling, whilst not obstructing the view through the window.