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An Educational Reader from Solar Schoolhouse WHAT’S INSIDE Take a Solar Home Tour ........................ 2 Tracking the Earth’s Path ....................... 4 Heating Things Up ............................... 5 Passive Solar Design ............................ 6 Solar Hot Water .................................. 7 What is Photovoltaics? .......................... 8 How Photovoltaics Works ...................... 9 Cooking with Sunlight ......................... 10 Solar Fountains Run by the Sun............ 12 Building a Model Solar Village .............. 13 Solar Student Builders ........................ 14 The Next Generation of Solar Homes .... 15 Solar Laundromat .............................. 15 Sun & Games ................................... 16 solarschoolhouse.org Using the Sun to Heat, Cool and Power Your Home Sponsored by: P Take a Solar Home Tour On the outside this house looks like many others. Walking past Solar-assisted hot water it, you might not even know it was a solar home. However, once system heats water and you examine the details of its design and construction, you’ll see contributes to space heating. that for this house, its all about the Sun! Deciduous trees shade the house in summer and let the Sun’s warmth heat the house in the winter when their leaves have fallen off. Solar panels on the roof generate electricity used for lighting and appliances. Extra insulation in the roof and walls. Front overhang shades the house from the hot summer Sun, keeping it cool. Low-e windows insulate the house from fluctuations in temperature. South facing windows absorb the solarschoolhouse.org warmth of the Sun in the winter. Drought resistant landscaping A backyard clothesline lets the and water efficient irrigation Sun dry clothes energy free. uses less water than a lawn. 2 Your Solar Home Educational Reader Heavy duty blown-in recycled cellulose insulation acts as a barrier between indoor and outdoor temperatures. Some solar home features are found in homes of all varieties. How many can you find at your house? High clerestory windows let light in and keep heat out. The sunlight reflects off of the ceiling and walls illuminating the house. Energy efficient fluorescent and LED lighting uses about 75% less energy than traditional lighting. Ceiling fans move warm air down in the winter and provide a cooling breeze in the summer. solarschoolhouse.org Window coverings can be adjusted to allow heat or Energy Star® refrigerator and light in, depending on the oven use less electricity than outside temperature. traditional appliances. Photos courtesy of SMUD. Now you’ve seen a solar home, time to find out how it works! Your Solar Home Educational Reader 3 B Tracking the Earth’s Path On the first day of summer, As the Earth continues to travel it passes around June 21st, the northern another point where the axis is tilted hemisphere is tilted toward the sideways to the Sun. Once again day and Sun. This is called the Summer night are the same length. This is the first day Solstice, and the Sun’s path of spring and called the Vernal Equinox. is higher in the sky than it is �W¡ ¡ ring in on any other day of the year. �Sp ter Because the Sun is in the sky for more hours, the Summer Solstice is also the longest day of the year. The Earth reaches the other side of the Sun on the shortest Su ¡ day of the year, the m n Winter Solstice. m tum As the Earth continues its orbit, it reaches er ¡ Au This is the first day a point where it’s tilted sideways to of winter, and the the Sun. This is called the Autumnal northern hemisphere Equinox. Both the day and the night are is tilted farthest away the same number of hours. from the Sun. Why are there Different Seasons? To understand what causes the seasons of the year, Planning is Step One remember that the Earth is always moving. It is spinning on The first step in designing a solar or energy efficient home is a its axis daily and also making a huge circular orbit around the solar site evaluation. Before plans are begun, architects and home Sun once a year. builders evaluate the annual path of the Sun in relation to the specific At different times of the year, different hemispheres are construction site. That knowledge is useful when making decisions such tilted toward or away from the Sun. When an area is tilted as the building orientation, floor plan, roof design, overhangs, window toward the Sun, days are longer and the area receives more placement, building materials and landscaping. Small Winter hours of light than when it is tilted away. These extra hours The Sun’s path also effects the optimal size, location and positionSun Angleof a of sunlight give the Sun more time to heat the Earth. The solar electric (photovoltaic) system for maximumNORTH exposureSOUTH to sunlight. The northern hemisphere is tilted towards the Sun between more sunlight a solar module gets, the more electricity it will generate. June and September which is why summer is the northern Seasonal Sun Paths Summer Sun Angle hemisphere’s hottest season. Summer Sun Path Courtesy of Remu. Winter Sun Path Large Summer solarschoolhouse.org Sun Angle South NORTH SOUTH Community Planning The Sun’s path in the sky changes Winter Sun Angle The suburb of Nieuwland, as the Earth travels around the Sun. in Amersfoort Netherlands, During the summer months, the Sun is a modern example of is high in the sky. In the winter, the community planning to Sun crosses much lower in the sky. Small maximize use of solar energy. Homes were built to Winter Houses facing south can stay cooler Sun Angle face south allowing their rooftop solar modules to NORTH SOUTH get optimum Sun exposure regardless of the season. in the summer by using window overhangs to shield them from direct sunlight. In the winter, when the Sun is lower in the sky, the windows let in the heat from the solar rays. 4 Your Solar Home Educational Reader Large Summer Sun Angle NORTH SOUTH D Heating Things Up Understanding Heat Knowing how heat moves is important To heat our homes with sunlight in the winter and keep them cool in the summer, we need to understand what heat is, and how it is transferred when learning to design a solar home. from one object to another. Heat is a form of energy that moves in three different ways: radiation, convection & conduction. Heat always flows from warmer areas to cooler areas. It only stops flowing when both areas reach the same temperature. Using the principles of heat transfer allows us to heat objects, cool them, or keep their temperature static. Principle #1: Radiation Radiation: When sunlight shines on an object, it’s either absorbed The direct transfer of heat by electromagnetic waves. into the object or bounces off. There are many types of radiation. Light, heat and radio waves are just a Black surfaces absorb almost all Conduction: When an egg cooks few of the many kinds of radiation we use in our daily lives. of the sunlight that falls on them. in a frying pan, the cooler egg is in direct contact with the hot surface Radiation transfers heat between objects that are not touching. Sunlight When light is absorbed into an object it turns into heat. White of the pan, and absorbs heat by is a form of radiation that transfers energy from the Sun through the conduction. vacuum of space. and mirror-like surfaces reflect light and heat. Principle #2: Conduction The movement of heat through direct contact. Conduction is the transfer of heat by direct contact. Heat moves by conduction when two objects of different temperatures are touching each other. The warmer object will conduct heat to the cooler object until both reach the same temperature. Conduction is also the movement of heat within a solid object. Substances that transfer heat well are call conductors. Metals, especially copper and aluminum transfer heat easily and are good conductors. Still air and gases are poor conductors. Radiation & Convection: Heat Loss by Convection: Hold your hand in front of a When wind blows across the roof, Principle #3: Convection candle and you can feel the heat a house can lose a lot of heat to The movement of heat through gases & liquids. radiating to you. But put your the wind by convection; the faster Heat also travels through the air as moving currents. The faster the air is hand above the candle and it the wind is moving, the more heat moving, the more quickly it can transfer heat by convection. The air in quickly gets very hot. This extra it pulls from the roof. contact with the heat source absorbs heat, expands and rises. Cooler air heat is being transferred to your below moves in to take the place of the rising warm air. Liquids behave hand by convection. similarly when heated by convection, the warm liquid rises being replaced by the cooler liquid. solarschoolhouse.org Slow moving or still air is a poor conductor, transfers heat very slowly and can even act as insulation. Insulation Substances that slow down convection, conduction and radiation. Many materials, such as Styrofoam and leather, are poor conductors and transfer heat slowly. Poor conductors are also called insulators. Since Insulation: The down stuffing in a jacket or sleeping bag has thousands still air is an insulator, anytime we can trap air to keep it from moving, it of tiny spaces that trap air, and keep currents from flowing. This trapped provides insulation from heat transfer. air acts as an insulator. The thicker the layer of trapped air, the harder it is for the heat to escape. Your Solar Home Educational Reader 5 NPassive Solar Design Passive Solar Design Features Most homes use gas, electricity or heating oil to stay warm in the winter and keep air conditioners running in the summer.

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