Tech Directions - December 2007 - (Page 18)

Here Comes the Sun! Residential Solar Systems Add Up to Savings By Harry T. Roman htroman49@aol.com E VERY day, the sun showers our planet with millions of times more energy than its people use. The only problem is that the energy is spread out over the entire earth’s surface and thus must be harvested. Engineers like me are learning to capture and use some of this energy to make electricity for homes. Solar panels make up the heart of a solar energy system. They can be large, and they require care and planning during the design phase. The panels are the big version of the familiar little solar cells that power the calculators we use. This article describes the planning of a solar system and gives a glimpse of some of the math involved. house where the panels will be located. The sun’s path differs greatly from season to season. It is high in the summer and low in the winter. For instance, at the 40° north lati- much sunlight is received during the entire solar day. In summer, the sun sweeps out a large arc in the sky from 30° north of east to 30° north of west. In the winter, it is just a very shallow, low arc in the cold sky. In Check the Sunlight First and foremost, for a house to take full advantage of solar energy, it must receive plenty of direct sunlight all year long. The solar sys= tem engineer must first determine the solar window—the area swept out in the sky that indicates how the sun moves through it. The engineer then considers the roof of the Harry T. Roman is an electrical engineer, inventor, writer, and strong supporter of technology education, East Orange, NJ. Photograph courtesy of MSK, a Suntech brand Solar panels can be large and require care and planning during the design phase of a home. tude where I live, in the middle of summer, the sun will be at an angle of 73° from the horizon. In the winter, it will be only about 23°; and during spring and fall, 40°. How big an arc the sun makes in the sky also differs greatly, and this affects how spring and fall it is simply east to west at a moderate angle. The math used to determine the angle of the sun at every hour of the year, and its ability to illuminate a panel with its own specific angle and orientation on the earth, can be 18 techdirections ◆ DECEMBER 2007

Table of Contents Feed for the Digital Edition of Tech Directions - December 2007

Tech Directions - December 2007 Technically Speaking Contents Direct from Washington The News Report Technology Today Technology's Past Mastering Computers Is This Op-Amp Any Good? Lab-Built Checker Removes All Doubt Here Comes the Sun! Residential Solar Systems Add Up to Savings Pinhole Cameras—For Science, Art, and Fun! Poster Project Maps Out Design Process Gifts for Geeks E-gallery More than Fun

Tech Directions - December 2007

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