Evaluating Solar Power Options: Plotting Your Sun Chart
Plotting a sun chart tells you how much direct sunlight you can expect over the course of a day so you can determine whether solar power is a viable option where you live. Sun charts are easy to plot and provide a way to represent the movement of the sun across the sky. Here's how to create your own sun charts and how to use them to evaluate the amount of sunshine you can expect to receive at your home.
Chart the basic path of the sun
The position of the sun may be plotted with two angles: azimuth and elevation.
Azimuth is the sun's angular distance from a fixed line; in the northern hemisphere, that fixed line will probably run directly south. Theoretically, at noon, when the sun is directly overhead, the azimuth angle is 0.
Elevation is the angle created by a line parallel to the ground and a line going from the ground to the sun. If the sun is directly overhead, its elevation measurement is 90 degrees; when it sits on the horizon, the elevation is 0.

Plot the location of the sun in the sky.
Then create a graph of the sun's passage over the course of a day. Imagine a sheet of graph paper wrapped around your house. As the day progresses, you make dots where the suns shines on the graph paper.

Making a sun chart.
The following figure shows your sun chart looks like if you plot the movement of the sun. The arc in the middle represents either spring or fall. All other paths lie somewhere between the two extremes, represented by summer and winter solstice, which are the longest and shortest days of the year (June 21 and December 21, respectively).

Daily sun charts at different times of the year.
Add skyline effects
You can easily add a skyline impediments, which include horizon, buildings, trees, towers, and so on to your sun charts.
When the sun goes behind a mountain or a tall building, you don't get any direct sunlight at all. If the sun goes behind a tree, you may get some direct sunlight, but mostly you get shading. Impediments on the horizon also change the time of dawn and dusk. If a big mountain lies directly west of your house, dusk falls a lot earlier.

Add skylines to a sun chart.
You can either buy (very expensive, and you only need it once) or rent ($25 per week) a Solar Pathfinder, which works as follows: You stand at the site you want to measure, aim the device south (it has a compass), level it (it has a bubble level), and then read the shade reflections on a domed indicator.
Note sunlight intensity
When the sun is lower in the sky, solar radiation must pass through more atmosphere, and it's therefore reduced by scattering and absorption.
The sun is the most intense when it's directly overhead. And summer sunlight is much stronger than winter.

Plot the sunlight intensity over the course of a day and season.
Sunlight likewise changes along with the weather. If your climate is often foggy or hazy in the morning, the charts show a very shallow curve on the left-hand side, and then when the fog burns off, the chart goes back up to normal.

Sunlight intensity varies with weather conditions.

Green Living Glossary
acid rain
A mild acidic solution that falls in rain or as dry particles caused when fossil fuel burning produces sulfur dioxide and nitrogen oxides. Acid rain has been linked to damaging effects on waterways and forests.

Green Living Glossary
active solar design
A strategy for designing high-performance, ultra-energy-efficient buildings. Active solar incorporates all the elements of a passive solar design with additional mechanical equipment, such as pumps or fans, to take advantage of the heat from the sun.

Green Living Glossary
alternative energy sources
Wind, hydro (water), biomass (fuel from natural material such as crops and agricultural waste), and solar power.

Green Living Glossary
biodegradable
Made from materials that will decay and break down into naturally occurring elements in a fairly short amount of time.

Green Living Glossary
biomass
Fuel made from natural material such as crops and agricultural waste.

Green Living Glossary
Bokashi
A Japanese term referring to a process of fermenting organic matter

Green Living Glossary
carbon emissions
Carbon released when many substances — particularly fossil fuels such as oil, gas, and coal — are burned by vehicles and planes; by the manufacturing processes of many consumer goods; and by the heating, cooling, and electricity for your home.

Green Living Glossary
carbon neutral
The state of reducing a person’s carbon emissions as much as possible and balancing the remaining carbon emissions by offsetting them with processes that consume carbon.

Green Living Glossary
carbon offsets; carbon credits
Paying for or participating in programs that reduce the carbon in the atmosphere. Purchased shares go toward reducing the same amount of environmental costs that an activity expends. Carbon offset programs or projects often involve tree planting because trees have a huge capacity to absorb carbon from the atmosphere. Other programs involve everything from supporting solar and wind power to replacing fossil fuel–burning stoves in developing countries with more sustainable energy sources.

Green Living Glossary
carcinogen
A cancer-causing substance.

Green Living Glossary
carpooling
Reducing the number of vehicles going to the same destination by having two or more people ride in the same vehicle. In most cases, carpoolers take turns being the driver and using their own vehicles.

Green Living Glossary
car-sharing
A system in which a person pays a fee that gives them access to a vehicle (or a pool of vehicles), usually parked in an easily accessible location. Car-sharing can eliminate the need for a personal vehicle.

Green Living Glossary
climate change; global warming
Changes in the concentrations of various gases in the atmosphere that are affecting the planet’s climate. Many scientists believe that the increase of carbon dioxide is a primary contributor to global warming, which occurs when gases trap warmth in the earth’s atmosphere instead of letting the atmosphere release it.

Green Living Glossary
compact fluorescent CFL bulbs
Fluorescent light bulbs that fit into a standard light bulb socket and use a fraction of the energy of their incandescent counterparts.

Green Living Glossary
compost
Decayed plants and other organic matter that breaks down into rich soil.

Green Living Glossary
core aerating
Poking small holes in the top few inches of lawn to encourage the flow of air, water, and nutrients.

Green Living Glossary
corporate social responsibility
Principles adopted by a business to make sure that its operations harm no one and instead benefit everyone around it and involved in it.

Green Living Glossary
daylighting
Bringing natural light into a home.

Green Living Glossary
ecosystem
A community of living organisms and nonliving materials.

Green Living Glossary
ecotourism
Sustainable and ethical travel in a natural environment.

Green Living Glossary
Energy Star
The federal government system for rating energy efficiency in appliances.

Green Living Glossary
Environmental Protection Agency EPA
Federal agency that regulates environmental laws.

Green Living Glossary
Fairtrade
System to ensure that workers and producers receive fair value for their products and that mandates sustainable practices in producing those products.

Green Living Glossary
food miles
The distance food travels from where it’s produced to the consumer.

Green Living Glossary
foodprint
The amount of land that various diets require to sustain them.

Green Living Glossary
fossil fuels
The energy-rich organic substances, traced back to the remains of organisms that lived 300 to 400 million years ago, that modern societies burn to provide power.

Green Living Glossary
geothermal
Energy within the Earth in the form of heat.

Green Living Glossary
greenhouse effect
The warming of the planet caused by gases in the atmosphere trapping the sun’s heat instead of letting it get through to space. This action is very similar to what happens in a greenhouse.

Green Living Glossary
greenhouse gases
Gases such as carbon dioxide, methane, and nitrous oxide produced by the burning and processing of fossil fuels and that contribute to global warming and acid rain.

Green Living Glossary
greywater
Water already used for washing, laundry, or showering that is appropriate for household functions from toilet flushing to watering plants.

Green Living Glossary
Leadership in Energy and Environmental Design LEED
A scoring system to rate how ecologically friendly buildings are.

Green Living Glossary
light shelves
White or light-colored horizontal fins above windows that bounce sunlight up onto the ceiling to bring it deeper into the room.

Green Living Glossary
light-emitting diode LED
A tiny semiconductor that emits light.

Green Living Glossary
natural gas
An energy source that burns cleaner than coal and oil but still releases carbon dioxide when it burns and methane during production, storage, and transportation.

Green Living Glossary
organic
Of living things; in food, grown without chemical fertilizers or pesticides or genetically modified organisms.

Green Living Glossary
passive solar design
Building design that takes advantage of the fact that the summer sun is higher than the winter sun. Overhangs shade the building from the summer sun and allow the lower winter sun to enter the building and heat it.

Green Living Glossary
petrochemicals
Chemicals derived from petroleum.

Green Living Glossary
phantom load; standby power
Energy drawn by a plugged-in appliance even when the appliance is turned off.

Green Living Glossary
plastic identification code
A triangle with a number from 1 to 7 inside indicating what type of plastic an item is made from.

Green Living Glossary
PV cell
A photovoltaic cell; a cell with a thin semiconductor that converts solar power into electricity.

Green Living Glossary
recycling
Collecting goods that have reached the end of their lives and processing them, their parts, or some of their parts, into the raw materials from which new goods are made.

Green Living Glossary
renewable energy
Energy from sources that cannot be used up, such as wind, water, and the sun.

Green Living Glossary
skylight
A rooftop window that brings in twice the light of a traditional window of the same size.

Green Living Glossary
solar panel
A panel containing cells that convert sunlight into electricity.

Green Living Glossary
sun tunnel
A passage that brings light into a room by bouncing sunlight through a small dome skylight on the roof connected to another skylight on the ceiling of the room. (Also known as a sun tube, sun pipe, and solar tube.)

Green Living Glossary
sustainable
Using natural resources in a way that allows for continued viability.

Green Living Glossary
thermal hole
An opening such as a window that leaks heat and air-conditioning energy.

Green Living Glossary
thermal mass
The ability of a material to absorb and store temperature.

Green Living Glossary
three Rs
The environmental practices of reducing consumption, reusing items, and recycling.

Green Living Glossary
top-dressing
Applying a light scattering of compost, other mulch, or sometimes fertilizer, over soil surfaces to add organic matter or nutrients without digging it in

Green Living Glossary
toxic waste
Disposed materials that can cause harm to people, animals, or the environment.

Green Living Glossary
vermicomposting
Composting with worms.

Green Living Glossary
xeriscaping
Landscaping for water conservation; a practice of garden planning and maintenance.