Daniel Stouffer asked:


This article explains the fundamental terms related to sunlight and residential solar energy systems. You will learn about units of measure, forms of solar radiation, spectral distribution, energy distribution, and solar position. Germany and Japan are often cloudy or foggy but is where most solar panels now sold in the United States are produced. Because of the way solar modules produce power from direct, diffused and reflected light it works great in these conditions. A very high performing solar array can be found on a foggy beach in California. Measuring Light and How Solar Panels Use It The following terms related to different aspects of light and their characteristics as they come in contact with different physical formations on Earth. The definitions below will help explain how some residential solar energy systems seemingly in areas with poor sun quality can actually achieve respectable power output. Irradiance - The rate of solar radiation falling on a given area at a moment in time. Irradiance is measured in units of kW/m2 (read kilowatts per square meter). Irradiation - The amount of solar energy over time. Irradiation is measured in units of kWh/m2/day and read kilowatt-hours per square meter per day. Different locations through the United States (and the World) have different levels of irradiation. As in previous articles, you can find many maps on the Internet that will show the average annual solar irradiation throughout the United States. Light Characteristics and Solar Fundamentals Deflection - The amount of light lost when the solar panels aren't facing the sun squarely as the sun moves across the sky. This loss of light is called deflection. Even though solar cells are etched on the surface into little pyramids to collect light from all angles, coated with a light diffusing coating, and protected with light diffusing glass, more light is deflected when the sun is not directly in front of the panels. Spectral distribution - The bulk of the solar light spectrum which reaches the Earth's surface is ideally suited for conversion by solar (PV) cells into electrical energy. The Sun's Position as It Relates to Solar Energy Systems Two coordinates describe the position of the sun at any given time. The orientation provide the information to home solar installers to figure out and orientate the solar energy system to collect and convert as much sun energy as possible into residential electricity. Azimuth - Describes the direction from east to west in degrees (°). North is 0 degrees. East is 90 degrees. South is 180 degrees. West is 270 degrees. The layout of this grid is not unlike the face of a compass. The markings are in degrees indicated on the face. Altitude - Is the measurement in degrees, like on a compass, that the sun is from the horizon. Altitude is measured in degrees as well. Altitude is the point in the sky where it is located right over head often referred to it's highest point in the sky. Just like a plane has an altitude that it travels at across the sky as it is measured above the horizon. So does the sun. Irradiation Example for a Solar Energy System In the coast area of California, residential solar energy systems are sized using an average of 5.5 sun hours per day. More often than not, most people think or comment that their house gets more like 8 to 15 hours of sunlight per day. This is true but sunlight is different than solar sun hours per day. The sun hour numbers take into account things like fog, rain, night and, most importantly, deflection. The sun hour ratings listed for different places throughout the United States is the amount of solar irradiation available to be converted into electricity by a fixed mounted solar array facing true south at the optimal tilt angle. A solar module produces its full rated power only when in direct sunlight, so when the sun is to the East or the West of the module it is not at full production. reThinking the Economics of Residential Solar Energy Doing your part to choose green, solar power can be a bit confusing and complex at times. There are many terms, aspects of the installation, and details about your sun light hours per day that all influence decisions to upgrade your home to solar energy. A very interesting and attractive option currently development in the solar market is the option to rent a residential solar energy system versus having to pay out up to $40,000 for your own solar panels and related equipment. The economics of residential solar power have changed. Every American homeowner can decide to upgrade to solar energy and avoid large purchase of a solar energy system. New rental programs are now available that give homeowners the chance to adopt residential solar energy without having to make a huge investment.

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Michael Read asked:


As solar power is continues to gain popularity, manufacturers are now offering solar powered attic fans to consumers to help ventilate attics and keep attics cooler. The solar powered fans that are used for attics generally have a smaller solar panel to help power a DC motor when the sun is shining. By using solar powered attic fans, you will enjoy a plethora of benefits, including the four I will discuss in this article. 1. Save money There is no arguing the fact that electric rates are always on the rise, which makes solar powered fans so popular. By storing more solar energy because the roof is always in direct contact with the sun, you will make use of much more energy without paying a penny. Also, by continuously keeping your attic cool because of the low cost of solar powered fans, you no longer have to worry about dealing with mildew and mold. 2. Maximize exposure of sun to the solar panel Because of the way that many solar powered attic fans are designed, there is a mounting bracket that houses the solar panel. This helps optimize the angle of the panel to put it to use much more than an electric fan. The mounting bracket will also allow for remote mounting of the solar panel, which allows for optimal panel placement. 3. Minimize the ambient temperature of the solar panel With a powder coating that rests over the entire assembly in neutral gray color, this helps minimize the power output losses as temperatures increase. In doing so, it will help cool the attic and ensure that the solar powered fan does not act like a heat sink. Also, the mounting bracket allows for an envelope of cooler air to continuously circulate around the entire solar panel. By doing this, it provides the maximum electricity output from the panel to help run the fan motor. 4. Adaptable for all environments Although solar power is just becoming popular, technology has grown to allow solar powered attic fans to be adaptable for all locations, roof types and environments. Obviously, if you live in an environment that sees more sun you will be able to create more solar energy. However, the powder coat over solar powered fans allows these fans to withstand any environment. Solar powered attic fans are perfect for every attic to help eliminate the heat while decreasing the electric bill at the same time. Because of the high efficiency, environment friendly capability, and lower electric bills, solar powered fans are suitable for everyone in any environment around the world.

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Daniel Stouffer asked:


The first thing you might ask - what is solar radiation and how does it related to solar generated electricity? That is a good question and a topic discussed in our next article in our series dedicated to home solar power. This article, on the other hand, explains how kilowatts are calculated based upon the energy output of your solar array. We will also highlight the difference between solar cells connected in parallel versus in series. The average American home uses about 25 kWh of electricity per day. The following example illustrates how to calculate the power produced by a residential solar energy system. Looking over a solar radiation grid, we can determine that a residence gets five daylight hours of solar radiation in one day which is then averaged out over the entire year. Solar radiation maps are highlighted on may websites throughout the Internet. You can do a quick search for "solar radiation" to find one. In any area across the entire United States, they detail out the amount of sunshine hitting a given location based upon the time of year and its address. Calculating the power from a solar energy system Divide the average kWh per day by the average sun hours per day. For this example, we take 25 kWh divided by 5 hours of sun per day = 5 kW system This 5 kW system will generate 25 kWhs under optimal conditions in direct sunlight for 5 hours, or 25 kWh on an average day with some at peak production and most of the sunlight at less than optimal angles. Future articles related to solar energy will continue to explain the effects of sun angle, reflection, and refraction on the design, output, and installation of solar panels. Energy as it Pertains to Solar Modules Individual solar modules that are measured in watts have a particular voltage (around 40 volts) and a particular amperage (around 5 amps). A solar module with 40 volts and 5 amps is called a 200-watt module, which means that it has the potential to produce 200 watts of electricity when in direct sunlight, away from trees or shading, and clear of snow or debris. Since most electrical components around your house are only rated for 600 volts DC, it is rare to see a solar array with a string larger the 15 solar modules. On the other hand, since inverters need a minimum voltage or pressure to turn them on, you will seldom have a solar array with a string solar modules with a size smaller then 6. Electrical components, like solar cells, panel modules or batteries, can be connected in either series or parallel. This makes a big difference in the total quantities of energy produced from the solar energy system, as well as the stability of the technology over time. Each solar module or component has a positive and a negative pole. In essence, this is the same way batteries have their negative and positive poles arranged. Take a look at how you but batteries in a flashlight. Same idea here. The manner in which these poles are connected makes a big difference. Connect Solar Panels in Series When you connect residential solar energy systems in series, you connect the positive (+) pole on one component to the negative (-) pole on the next. When modules are connected in series, the voltages are added. Adding voltage together in this fashion creates a long chain of solar modules all working together, depending upon each other, and creating a flow of current that increases along the length of the system. These modules in series are called Strings. The average string is 8-12 modules so the voltage would be 320 - 480. Unfortunately, we encounter some negative aspects of of this type of construction. Connecting Solar Panels in Parallel When you connect solar panels or components in parallel, you connect the panels so current can travel to your inverter and to your house via multiple paths. Unlike adding solar modules in series which increases the volume of current as it goes, the solar panels connected in parallel has the effective of leaving the current or volume of electricity passing through the system the same. Solar panels or strings of solar arrays tied together in parallel are called parallel systems. Their amps are combined together but the total voltage remains the same. Adding amps is like increasing the volume, the pressure stays the same but the volume goes up. Inverters can only handle so much volume so you will seldom see more than 1 to 3 strings in parallel; positive ends to positive ends with negative ends to negative ends. One of the advantages of parallel connection is that electricity continues to flow, even though one of the components (or strings) is damaged. If a system is entirely in series, one damaged component stops the entire system. You may remember the ever-frustrating Christmas lights that were connected in series. Often difficult to trouble shoot, strings of lights connected in series are hard to fix when one bulb blew out. Now, the modern Christmas lights are connected in parallel. You are able to determine this easily. There are usually two different wires coming in and out of each bulb. You can feel this via their less frustrating maintenance and operation. Options for Residential Solar Energy Systems In this article, we explained in some detail how solar modules calculate the power they produce as well as how connecting solar arrays in series or parallel can have an large impact on energy output as well as complexity of design. Our next article will cover how sun angle affects solar energy systems and how to quantify the solar power produced from the sun. New solar energy system rentals allow you to upgrade your home to solar generated electricity with no large system to purchase. You can rent the solar energy equipment needed to generate up to 100 percent of your electricity needs. Exciting aspects related to clean, green solar energy are emerging all around us.

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Paul Calhoun asked:


Introduction: Global warming impact to our quality and cost of living is large and very catastrophic. Homeowners are well aware of the increasing energy costs to heat, cool and illuminate their homes. The increasing costs of oil and other fossil fuels are daily headlines. The insatiable demand for energy to fuel world growth guarantees that the cost of these limited fuels will continue to increase. Political/economic forces will determine the rate of increase for fossil fuels. In addition, the increasing cost of global warming using fossil fuels is slowly being recognized. The world is slowly beginning to understand the urgent need for renewable energy sources. However, each of these alternative energy sources brings major advantages and disadvantages. An example is wind generated energy. Wind energy is available to the whole world and generates electricity competitively with fossil fuels. The technology is understood and easy to apply. But, there are big objections to a windmill in "my back yard". Also, the number of birds and bats that will be crushed with wind power generation is not a warming thought. Wind technology will be a component of our energy solution. However, because of the above concerns, we need other major solutions to meet our demand for energy sources. This search leads us to solar energy. The amount of sun energy striking our world in one day is sufficient to supply our energy demands for a year. We will not run out of this source in the foreseeable future. The major barrier to harnessing solar energy has been cost and convenience. For example, drying clothes in a dryer is easier than hanging clothes on an outside line, thus convenience precluded efforts to find more energy efficiency. We can convert solar energy to electricity but with a major capital cost. Greater acceptance and use of solar energy will lead to lower cost. Solar Energy: Energy from solar energy can be divided into two major categories: Passive Solar Energy: This technology ranges from clothes drying in the sun to solar heating for hot water and many other passive techniques. All are important for our present and future quality of life. The technology is well understood and can be implemented as economics and space conditions allow. Active Solar Energy: One of the active solar energy technologies is converting solar energy directly into electricity. It is called photovoltaic cell or PV. This is a device that converts light into electricity using the photoelectric effect. The first working solar cells were constructed by Charles Fritts in 1883. These prototype cells were made of selenium and achieved efficiencies around one percent. The silicon solar cell was created in 1954. The solar cell has benefited from the development of silicon semiconductors. Physics of Active Solar Energy: The physics of photon to electricity conversion is well understood by physicists. The basic model is of a photon from the sun which strikes the cell material and excites electrons that emit electricity. This model is simple compared to the complexity of modern day semiconductors. The major variables of PV electrical generation are cell material and impurities in the cell material. Manufacturing Technology for Active Solar Energy: Primarily single crystal, high purity silicon has been used to generate photon to electricity conversion. The manufacturing techniques for single crystal silicon and limited quantities of pure silicon impose a high cost for PV devices. Shortages of refined silicon have been hampering production worldwide since late 2004. This shortage persists to this date and has slowed PV growth. New materials are starting to come forward which should lower the PV materials hurdle. Efficiency growth of Active Solar Energy: Since the silicon PV invention in 1954, cheaper fossil fuel prices largely removed solar power from the public consciousness. Annual growth of electrical generation by PV ranged from 10 to 20% percent throughout the 1980's and 1990's. Worldwide installation of PV reached 1000 megawatts in 1999. Manufacturing costs for PV arrays has been dropping 3 to 5% over the recent years. This cost drop began to expand the use of PV electricity generation. Total peak power of installed PV was around 6000 megawatts at the end of 2006. Installed PV is projected to increase to over 9,000 megawatts in 2007. The average lowest retail cost of large photovoltaic arrays has declined from $7.50 to $4.00 per watt between 1990 and 2005. PV materials have also been improving in recent years. The most recent materials approach is to process discrete cells on silicon wafers cut from multi crystalline ribbons which form thin films. This approach is the least expensive of known technologies. This group of technologies includes amorphous silicon cells deposited on stainless-steel ribbon, cadmium telluride (CdTe) cells deposited on glass, and copper indium gallium dielenide (CIGS) alloy cells deposited on either glass or stainless steel substrates. The efficiencies of these new materials are currently at 20%. Many researchers are working to improve the efficiencies. An added advantage of the new thin films is that they are flexible and are currently being used in roofing materials. Current Trends in Generating Active Solar Energy: Commercial businesses like Google, IBM, BJ's Wholesale, Estee Lauder, Kohls, Target, Tiffany & Co., Wal-Mart are installing PV solar energy. From "big box" discount giants to high end commercial businesses PV solar energy is finding acceptance in 2007. The most recent retail-outfitter to become part of this trend is Macy's, which announced earlier this month that it will install solar powered systems on 26 stores throughout California. These leading companies are turning to solar power because it makes good business sense and supports their environmental initiative. Creative financial arrangements allow these companies to afford the upfront capital costs and payback their loans with energy savings. So what does all this mean to the average home owner? PV Cost per Kilowatt (kWh): In the California market, where state incentives and net metering are in place, PV electricity prices are dipping below 11¢/kWh, on par with some utility-delivered power. Moreover, according to the U.S. PV Industry Roadmap, solar electricity will continue this trend and become competitive by 2010 for most domestic markets. The outlook is very positive for PV generation of electricity. Once the capital investment is made, the cost of PV electricity is equivalent to fossil fuels and will continue to decrease. Cost of PV Installation: The cost of installation is the major barrier that has to be overcome for widespread PV acceptance. Around 59% of world solar product sales installed in the last five years were applications that are tied to the electricity grid. Solar energy prices in these applications are 5-20 times more expensive than the cheapest source of conventional electricity generation. This premium is well beyond the reach of the average home owner. Fortunately, there are financial models coming forward to enable the consumer to finance PV solar installation and pay for this installation with the electrical savings. In order to make these financial models successful, federal and state incentives are needed and the installation should be connected to the electrical grid. These connections allow the home owner to sell back electricity when excessive amounts are available and to receive electricity when solar conditions do not allow sufficient electricity. Only fifty percent of our states have modernized to allow on-grid PV solar energy. Berkeley, California is leading the way to enable it citizens to save electrical cost and meet environmental needs. Here is how their plan works. A property owner hires a city-approved solar installer, who determines the best solar system for the property, depending on energy use. Most residential solar panel systems in the city cost from $15,000 to $20,000. The city will pay the contractor for the system and its installation, minus any applicable state and federal rebates, and would add an assessment to the property owner's tax bill to pay for the system. The extra tax would include administrative fees and interest, which would be lower than what the property owner could obtain on their own, because the city would secure low-interest bonds and loans. The tax would stay with the property even if the owner sold, although the owner would have to leave the solar panels. The property owner would save money on monthly Pacific Gas & Electric bills because electricity generated by the solar panels would partly replace electricity delivered by the utility. After the assessment expired, the solar panels, of a simple technology that requires little or no maintenance, would continue to partly replace PG&E electricity. The Berkeley plan is a map for the rest of the world to allow us affordable electricity and meet our responsibilities to the environment. I have a BS and MS in Metallurgical Engineering. Thirty six years spent in the development of semiconductors. Business experience in start up business plan. Currently, an oyster farmer and interested in helping the environment by deploying solar energy. Please visit my Web Site http://www.charlestonenvironmentalhelp.com AddThis Social Bookmark Button

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Anna Hart asked:


Solar energy is a potential source of free electricity and water heating. It offers the power to enjoy electrical power in remote areas of the world. It seems to offer health and safety along with power, but does it? Solar energy health risks are seldom mentioned. That may be partially due to the limited use of this source of energy. It may also be due to the lack of research in this area. Some have begun to study solar energy health risks, however, and if one researches long enough, a few estimates are available. Thermal Solar Energy Health Risks Solar energy health risks are inherent to the design and installation of most thermal energy systems. These are the systems designed to heat water and air for household use. Solar water heaters complete three basic operations before delivering hot water to your faucet or your heating unit: 1. collect sunlight and convert it into heat energy. 2. circulate fluids that transfer the heat energy to a storage unit 3. store the hot water until you need it The solar energy health risks with such a system usually occur in the storage units. Some units allow for the growth of allergenic molds and fungi. If proper materials are used for the storage unit, however, these solar energy systems present few, if any, health risks. Their advantages are that they are far safer than most fossil fuels or nuclear power - they have no emissions and do not pollute the air. PV Panel Solar Energy Health Risks The solar energy health risks associated with photovoltaic (PV) panels occurs before the panels are put into use on the consumer's home. PV panels are the panels used to collect solar energy from sunlight and convert it into usable electricity. The manufacture of PV panels requires the use of toxic materials. Silicon dioxide is mined from sand or quartzite and reduced with heat to pure silicon. Materials released during refining are the main health risks. Several steps in forming the photovoltaic cells utilize toxic materials. These are sprayed on the cells, and can readily be inhaled. It is estimated that solar energy health risks associated with producing PV panels per unit energy may be between 11 and 21 deaths per quadrillion joules of energy produced. Solar energy health risks from PV panels are very slight once the panels are produced and installed on the consumer's home. This type of solar energy is known for reliability and low maintenance. The home owner seldom needs to be involved in any repairs, and thereby cuts solar energy health risks. Passive Solar Energy Health Risks Passive solar energy provides safety and health. A new building that maximizes this technology can reduce energy costs by nearly one half. How? 1. Warming indoor air in a house through vertical, slanted windows facing the sun. The windows capture maximum solar energy from the sunlight. 2. Collecting solar energy in adobe or stone walls and floors, and then releasing it into the air as the temperature falls. 3. Collecting solar energy in a sun space, much like a greenhouse built on the sunny side of the home. This heat is sent into the home with proper ventilation. 4. Holding water in black roof tanks until needed, cutting the working time of the home's hot water heater. 5. Using clerestories - rows of windows near roof peaks that catch sunlight and bounce it through the building. The sunlight reduces the need for electric lights. In Summary Solar energy technologies present few, if any, health risks for the end user. Their use can reduce the health risks presented by other energy sources, providing cleaner, safer, more cost effective energy.

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