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Power plant generates electricity Transmission lines carry electricity long distances Distribution lines carry electricity to houses

Transformer steps up voltage for transmission

Power Tower

Step-down transformer reduces voltage (substation)

Electric Poles

Neighborhood transformer on pole steps down voltage before entering house

ƒ Distributed Generation Because so much energy is lost in transmission from the power plant to the end user, such as a home or school, many people are beginning to focus on a concept known as distributed generation. This type of electrical generation places the source of generation at the site where the power will be used. The most common form of distributed generation is using solar panels to supplement or completely provide the electricity used in a building. Some multi-family buildings in large cities are using solar panels to create their own microgrid of interconnected residences in the building, drawing from a system of solar panels installed on the roof or near the building. The benefit of distributed generation is that it essentially eliminates energy loss through transmission lines, called line losses. And because most distributed generation occurs in the form of a solar system, it reduces the greenhouse gas emissions associated with electricity generation from fossil fuels. However, solar panels and their components can be costly to purchase and install. The good news for solar system owners is that sunlight is free.

Building Science

We don’t really think about buildings using energy, but rather the people inside those buildings as being the energy users. However, a wide variation in construction materials and building codes from one time period to another, and one geographical area to another results in big differences among the amount of energy used in different buildings. Even though “Joe Energy” doesn’t change his behavior, he may use very little energy in a new, efficiently designed building, and may use much more energy in an older or less efficient building. Construction materials and techniques make a big difference. There are four main systems in a building that use energy: The building envelope; the HVAC system; the lighting; and the plug loads. You’ve already read about lighting and plug loads.

BUILDING ENVELOPE?

How do I fold a building? The short answer is you don’t. The building envelope isn’t a literal envelope. It is the part of the building that envelops the inside – the separation between the interior of the building and the exterior of the building. When we talk about the building envelope, we are referring to the walls, doors, windows, floors, and roof. All of the components of a building envelope serve to keep the interior climate under control. We want warm homes in the winter and cool homes in the summer. Walls are insulated and the materials used to construct the walls need to block thermal conductivity through them.

ƒ Insulation and R-value The earliest homes built in the United States had little or no insulation in them. The walls were made of thick timbers with plaster or canvas applied to the interior and holes plugged with clay. The walls blocked wind and the interior stayed warmer than the harsh winter temperatures outdoors, but a lot of thermal energy was lost through the walls. People often awoke to ice in their wash basins.

During the Industrial Revolution, insulation was wrapped around pipes to keep them cool to the touch and avoid any burns. Asbestos was used to insulate those pipes; as a result asbestos insulation around pipes and heat duct work began appearing in homes around the turn of the 20th century. Asbestos was used until its health hazards were known in the 1970s. Many older homes still have asbestos pipe and ductwork insulation in place. Today, houses are usually insulated with fireproofed cellulose, fiberglass, or expandable spray foam. Each of these materials has their own benefits and drawbacks, but if handled correctly they are all safe to use in home construction.

Insulation is measured by its R-value, or its resistance (R) to thermal conductivity. In general, materials made from wood, paper, glass, or organic foam have higher R-values. The R-value of insulation depends on the insulation type and its thickness. Building codes set by local authorities dictate the minimum R-value required in new home construction. The U.S. Department of Energy has made recommendations for attic, wall, and floor R-values in new home construction based on geographical climate.

ƒ Windows and Doors The best building design for energy efficiency would include walls with no breaks for windows or doors. However, that is both impractical and undesirable. How would you get in and out of the room? How would you know what is happening outside? What about the benefits of natural light? The reality is that putting a window or a door in a wall breaks up the thermal barrier that is the wall. It effectively pokes a hole in the wall