Posted by: dkrainwater on: April 25, 2009
The US Department of energy has also listed five considerations when picking materials to build on or add on your passive solar house. The following five elements constitute a complete passive solar home design. Each performs a separate function, but all five must work together for the design to be successful.
Aperture (Collector) The large glass (window) area through which sunlight enters the building. Typically, the aperture(s) should face within 30 degrees of true south and should not be shaded by other buildings or trees from 9 a.m. to 3 p.m. each day during the heating season.
Absorber is the hard, darkened surface of the storage element. This surface—which could be that of a masonry wall, floor, or partition (phase change material), or that of a water container—sits in the direct path of sunlight. Sunlight hits the surface and is absorbed as heat.
Thermal mass The materials that retain or store the heat produced by sunlight. The difference between the absorber and thermal mass, although they often form the same wall or floor, is that the absorber is an exposed surface whereas thermal mass is the material below or behind that surface.
Distribution The method by which solar heat circulates from the collection and storage points to different areas of the house. A strictly passive design will use the three natural heat transfer modes—conduction, convection, and radiation—exclusively. In some applications, however, fans, ducts, and blowers may help with the distribution of heat through the house.
Control Roof overhangs can be used to shade the aperture area during summer months. Other elements that control under- and/or overheating include electronic sensing devices, such as a differential thermostat that signals a fan to turn on; operable vents and dampers that allow or restrict heat flow; low-emissivity blinds; and awnings.
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Posted by: dkrainwater on: April 25, 2009
According to the United States Energy Saving website (2009) opaque objects absorb 40%–95% of incoming solar radiation from the sun, depending on their color—darker colors typically absorb a greater percentage than lighter colors. This is why solar-absorber surfaces tend to be dark colored. Bright-white materials or objects reflect 80%–98% of incoming solar energy.
Inside a home, infrared radiation occurs when warmed surfaces radiate heat towards cooler surfaces. For example, your body can radiate infrared heat to a cold surface, possibly causing you discomfort. These surfaces can include walls, windows, or ceilings in the home.
Clear glass transmits 80%–90% of solar radiation, absorbing or reflecting only 10%–20%. After solar radiation is transmitted through the glass and absorbed by the home, it is radiated again from the interior surfaces as infrared radiation. Although glass allows solar radiation to pass through, it absorbs the infrared radiation. The glass then radiates part of that heat back to the home’s interior. In this way, glass traps solar heat entering the home.
Thermal capacitance refers to the ability of materials to store heat. Thermal mass refers to the materials that store heat. Thermal mass stores heat by changing its temperature, which can be done by storing heat from a warm room or by converting direct solar radiation into heat. The more thermal mass, the more heat can be stored for each degree rise in temperature. Masonry materials, like concrete, stones, brick, and tile, are commonly used as thermal mass in passive solar homes. Water also has been successfully used.
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Posted by: dkrainwater on: April 25, 2009
To truly understand how passive solar energy works, you have to know a few things about heating and cooling works within the house. A basic law of physics is that heat moves from materials that are warm to materials that are cooler. The transference is constant until the temperature is the same in both materials. A passive solar home uses this knowledge by following the ideas of heat movement and heat storage.
One of the laws of science is conduction. Conduction is the movement heat makes when it moves between materials. When heat enters a material it makes the molecules in the material to vibrate. As the molecules vibrate they influence the molecules around them and cause them to vibrate also. This vibration transfers the heat between the molecules. For example, if you are cooking with a metal spoon, the heat from the pan and food will transfer through the molecules of the spoon. A wooden spoon, with less dense molecules, will not conduct the heat as well and other materials will not conduct the heat at all.
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Posted by: dkrainwater on: April 25, 2009
There are other ways to save money with solar energy. Passive solar home design is one of them. You windows, floors, and even walls can be designed to collect solar energy in the winter and convert it to heat. In the summer the same surfaces can be reversed and will reject heat and make your house cooler. This is call passive solar design and is very different then using solar cells and solar panels. It is heat energy and not electrical energy. It is solely for the purpose of heating and cooling your house and not for running electrical appliances.
Some passive solar homes are simple and simply have windows that face southward. North facing windows, especially in northern climes, are accessible to cold north winds that can infiltrate the home and make it cooler. Other passive solar homes are more intricate in design and more thought out. Not all passive solar homes are the same and it is best to build or redesign your home so that the building itself can take advantage of the particular location. Wind, sun, shadow, and other factors go into building the most productive dwelling. The length of winter or summer is also a deciding factor when the design is first initiated (USDE, 2009).
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Posted by: dkrainwater on: April 25, 2009
Solar energy that is converted to electrical power is called photovoltaic power. This technology uses wafers (semiconductor cells) that are about a couple of square centimeters in size. In physics terms, the cell is an area of a p-n diode. The cell coverts the sun light into energy. The number of cells that are placed upon a panel will dictate how much electricity is generated. Unlike other forms of green energy, solar power is static and does not need large amounts of equipment or towers to operate.
The cost of solar energy thirty years ago was quite expensive and did not really make much sense since the cost of energy was relatively low. Starting at twenty dollars a watt in the 1980s, solar energy today can be as low as fifteen cents a watt. The pv cell that is attached to the panel is energy intensive and will even start producing electricity in the early morning and evening even with the decline of sunlight during sunrise and sunset. With rotatable panels that are equipped with light sensors, the panel can be rotated to follow the sun’s path to get all energy that is accessible.
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Posted by: dkrainwater on: April 25, 2009
Even our children that are born now will not know the kind of earth we have had as adults in our lifetime. We are making huge fuel demands on our planet and we are not cutting back. Fossil fuels and their emissions are causing global climate changes and are destroying the entire environment in huge sections. With such a doom and gloom statement, some people would be surprised to know that the sun shines down more energy in a few days than all the fuel spent by humans on earth in history. That’s a lot of fuel. Only three weeks of good sunshine will offset all the fossil fuels that have ever been burned.
We have enough sun to live on the planet but how do we tap into the immeasurable amount of energy that is bounced off our planet and sent wheeling back into space? With the conquest of space and the development of micro-electronics, we as humans have a small hold on the vast amount of energy that is available to us. Solar energy and solar cells are now the best and cleanest way to for us to sustain the amount of energy we need to keep up the modern lifestyle in which we live today.
For more information on solar power, water power, and other alternative energy solutions, including energy saving products for sale, please visit: http://astore.amazon.com/rainwaterenterprises-20
