Passive Solar Energy

Description Passive Solar Energy is the use of energy from the sun without the help of photovoltaics.

What it does Passive solar energy is used to convert sunlight into usable heat, cause air-movement for ventilation or cooling, or store heat for future use. It is commonly used to help meet a building's energy needs by means of architectural design, such as special arrangement of windows, and utilizing materials such as floors that store heat, or other thermal mass.

Main Concepts There are three main concepts of passive solar energy. They are: -Daylighting -Passive heating -Passive Cooling

Daylighting Daylight is the use of natural light to supplement and/or replace artificial lighting. Strategies include: The proper orientation and placement of windows Use of light wells Light shafts or tubes Skylights Clerestory windows (Window openings in buildings that are well above ground level and provide sufficient amounts of daylight.) Light shelves Reflective surfaces Shading The use of interior glazing to allow light into adjacent spaces.

Passive Solar Heating: Passive solar heating happens when sunlight strikes an object, and in turn, that object absorbs the heat. It will occur in a building if windows are oriented correctly. The most powerful (and common) window orientation is south, but any orientation within 30 degrees of due south is still adequate and useful. For Passive Heating to be most effective, approximately eight percent of window to floor area is required for south walls. Once the heat is inside the building, various techniques can be adopted to keep, and spread the heat as needed.

Passive Cooling: Techniques opposite to passive solar heating are utilized. Here, buildings are designed to keep solar and air heat away. Internal heating from animate and inanimate objects is minimized and dissipated in the environment through ventilation. Shading devices (fixed or adjustable) reduce solar radiation. We can shade a building by natural vegetation and using special glazing in windows. External shading devices can reduce solar gains by up to 90%, while still admitting a large amount of indirect light. External heat gain can also be minimized by good insulation, reduced window size and by the use of reflective materials in the walls and roof. During the building design stage, attention should be paid to cross-ventilation and the direction of prevailing winds, the source of cooling nighttime breezes.

Possible Uses Passive solar energy methods are a very good way to make use of the the clean and inexhaustible energy from the sun. Passive heating technology is used as the direct or indirect gain for power consumption. It is used for : -Well-planned indoor heating techniques -Trombe walls -Space heating -Water heating -Thermo siphon (Thermo siphon is the technique that is based on the natural convection methods circulating liquids without using mechanical pumps.) It is used for the thermal mass (also known as the thermal capacitance or heat capacity) which is used to store the heat. Passive heating systems are also used in more common household things, such as: solar ovens, solar cookers, solar chimneys, earth sheltering, etc.

Solar Ovens The solar oven works following the principle of the greenhouse effect:  the sun’s short-wave rays cross the two glass walls without losing energy.  In touching the internal walls of the oven which are covered with a non-toxic paint, they are transformed into heat rays that can no longer cross the glass walls.  This creates an energy trap  that allows us to cook or heat meals.

Trombe Walls Trombe walls are sun-facing walls constructed from either stone, concrete, adobe, or an array of water tanks. These materials can each function as a thermal mass, and when combined with insulated glazing on the outside, and vents running along the perimeter of the mass, these walls effectively become a solar thermal collector. Herein lies the value of the Trombe Wall as a means of passive solar energy.

Trombe Wall with an overhang to prevent the hot summer sun from causing extreme heat.

History 1838 Edmund Becquerel observed and published findings about the nature of materials to turn light into energy. They were considered interesting, but were not pursued.

1860 - 1881 Auguste Mouchout was the first man to patent a design for a motor running on solar energy. He designed a device that turned solar energy into mechanical steam power and soon operated the first steam engine. He later connected the steam engine to a refrigeration device, illustrating that the sun’s rays can be utilized to make ice.

1883 Charles Fritz turned the sun's rays into electricity 1883 Charles Fritz turned the sun's rays into electricity. His solar cell had a conversion rate of only 1-2%.Another big milestone for solar energy history.

1904 Henry Willsie recognized the need to store generated power and built 2 huge plants in California. He was the first person to successfully use power at night, after generating it during the day.

1956 The first commercial solar cell was made available to the public at a very expensive $300 per watt.

1970 The Energy Crisis arose, and suddenly it became important to find an alternative form of energy, as people realized just how reliant we really are on non-renewable, finite resources like coal, oil and gas for our existence and everyday needs. Solar energy history was made as the price of solar cells dropped dramatically to about $20 per watt.

Today There is a renewed focus as more and more people see the advantages of solar energy, as it becomes more and more affordable. Solar electric systems are now used to power many homes, businesses, holiday cottages, and even entire villages in Africa. We now commonly see solar cells powering anything from household appliances to cars.

Sustainability With an expected lifetime of another five or six billion years, the sun is virtually a limitless source of clean energy. The amount of solar energy reaching the Earth's surface is enough to fulfill total global power consumption thousands of times over!

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Advantages

Saves Money After the initial investment has been recovered, the energy from the sun is practically free. It will save you money on your electricity bill. Solar energy does not require any fuel. The savings are immediate and for many years to come.

It is Very Environmentally Friendly Solar Energy is clean, renewable and sustainable, helping to protect our environment. Solar Energy does not contribute to global warming, acid rain or smog. It actively contributes to the decrease of harmful green house gas emissions. It's easily generated where it is needed.

A Passive Solar Energy System is Independent Solar Energy can be utilized to offset utility-supplied energy consumption. It not only reduces your electricity bill, but will also continue to supply your home with electricity in the event of a power outage. A Solar Energy system can operate entirely independent, not requiring a connection to a power or gas grid at all..

Low Maintenance Solar Energy systems are virtually maintenance free and will last for decades. Once installed, there are no recurring costs. They operate silently, have no moving parts, do not release any smells, and do not require you to add any fuel. More solar panels can be added in the future as your energy needs increase.

Disadvantages

The initial cost is the main disadvantage of installing a solar energy system, largely because of the high cost of the semi-conducting materials used in building one. The cost of solar energy is also high compared to non-renewable utility-supplied electricity. As energy shortages are becoming more common, solar energy is becoming more price-competitive. Solar panels require quite a large area for installation to achieve a good level of efficiency.

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