Solar Panel Installation

How Much, How To, and Upkeep

You’ve been reading the news – you’ve noticed your home energy bill rising – and you know the damage we are doing to our environment. But, you’ve also been reading up on ways to conserve. You’ve heard of solar panels, their benefits, their costs, and their return on investment. Now, you’re interested in possibly having a solar electric system installed in your own home. What’s involved in the installation process? Read on below to find out.

How Many and What Type of Solar Panels Will You Need?

This depends on a variety of factors, including the space you have, where you live, and how much money you have to spend on solar panels. Some solar panels are much more efficient, but much more costly. Some less efficient types of solar panels are more affordable, but will require you to buy more solar panels to compensate for their lags in efficiency. Maybe you live in an area that doesn’t have much sun (e.g., Seattle, Chicago). Maybe you live in an area that enjoys plentiful sun (e.g., California, Arizona). These are all factors you’ll need to consider when choosing the correct solar panels and determining which is the right type of system for your residential needs.

There are three main types of solar panels: monocrystalline silicon solar panels, polycrystalline silicon solar panels, and thin-film solar cells. They are listed in decreasing order from efficiency of the panels and cost. Monocrystalline silicon solar panels are your most efficient panels, but they come with a more hefty price tag than thin-film solar cells. Thin-film solar cells are great if you have a lot of space, because they cost less, but you’ll need to install more of them to get the same benefits and return on energy. But, most homeowners don’t have the space required for these types of solar cells. Everything’s a tradeoff, and you’ll be ahead of the game by researching the pros and cons of each type before calling an installer to figure out which system is the best for your needs.

Beginning the Installation Process

Let’s flash forward and assume you’ve done the research, have contacted a reputable solar installer, and are ready for installation. What’s involved? And how soon will you start to notice your return on investment?

Let’s start by talking about what really happens when you install solar panels in your home, and how they convert sunlight into energy. First, solar panels convert sunlight to DC current. An inverter (part of your solar power system that converts stored energy into voltage needed to run standard electrical equipment) converts this DC electricity to AC. Your home takes the energy it needs based on the number of electrical units requiring energy. If your residential solar system is also connected to the grid, any extra , unused electricity, is fed back to the grid (or to a battery, if you have a battery backup). In cases like this, you are typically eligible for something called net metering. This is essentially a credit that is given to your energy account from the utility company. When you draw energy from the grid (because you no longer have enough solar energy to consume), net metering compensates for the amount of energy you gave the grid. In essence, it’s possible to come out with a zero balance because what you put into the grid (from your solar panels) is roughly the same amount that you took from the grid (e.g., during nighttime).

In some extremely rural places, with limited or no grid availability, you may install home solar systems that are not connected to the grid. Your sunlight conversion is the same; however, you won’t have the option of connection to the grid when you run out of solar energy. This type of solar electrical system requires considerable monitoring of your energy use to make sure you have enough energy to get you through the day.

Before anything is installed, a solar engineer will come to your home and assess your home for the proper type of installation – asking you and consulting on the following things:

* How much sun will you have
* Where will the system be placed (on the roof, on the ground)
* How big will the system need to be to satisfy your energy needs
* Will you be connected to the grid or not connected to the grid
* How can you optimize the safety and functionality of the system once installed

Once you have gone over these things, and the solar engineer has recommended the best solar system for your residential needs, the solar panel installation process can begin.

Installing Solar Panels

When it comes to solar panel installation, hiring a professional is the best route. These individuals are well-versed in solar energy, know the ins and outs of installation, can maximize your return on investment by installing and positioning the panels correctly, and can give the system a once-over to make sure everything is safe for use.

There are some things you’ll need to consider prior to choosing a solar installer. Here are the most important things to consider:

* How much experience does the installer have installing solar panels?
* Are you dealing with a licensed and reputable solar installer?
* Have you contacted your state electrical board to determine if the solar company you are dealing with has any pending or active judgments or liens against it?
* Have you gotten multiple bids for the project?

Once you have done all your homework, done your due diligence, and chosen a contractor, it’s time to get started!

The entire installation process averages about two days. But, that doesn’t mean once you’ve decided on what type of system you want installed, they’ll be up and running by the end of the week. The installation process can be long and drawn out, because of the number of contracts that are involved. Once you’ve chosen your system, and if you’ll be connecting to the grid (as the overwhelming majority of homeowners with residential solar systems do), you’ll have to sign contract upon contract. One with the installer. Another with the electrical company. But, it doesn’t stop there. Once you sign your contract with the electric company, they’ll need to approve it, because you will be tying into their grid. The electric company will have a number of hoops that your system will need to pass through, including the efficiency of the system and the safety of the connections. Because we’re dealing with electricity, any malfunction or safety issue can be a huge pickle for the utility company and its equipment.

What other types of consultation will you need to have? If you’re installing solar panels on your roof, a roofing contractor will need to come out to determine if your roof can bear the weight of the solar panels. These types of “hang-ups” with the contractors can take weeks for approval. Then, you’ll need to work yourself into the installation schedule of the solar installers. So, what seems to be a simple two day process, could in fact, take a couple of months when it’s all said and done. What’s the payback? The money you’ll be saving on your first energy bill. And the financial incentives you get to take advantage of by going green and reducing your carbon footprint!

Maintenance, Repair, and Cost

Like with any type of system, you’ll need to maintain it, and at times, repair it. These repairs could come from malfunctioning parts, or ones that are just worn out and need replacing. Like your car, as long as you get it oiled and tuned every few thousand miles, you’ll enjoy many years of energy cost savings from your installed solar energy system.

How long can you expect your solar system to last? The majority of residential solar panel systems last for 25+ years. So, when you’re considering the hefty price tag of these systems, try to think of the energy cost savings of that long of a period. In the United States, most homes consume about 1 kW of electricity per hour, with the average utility bill nationwide, averaging at $0.10 for a kWh of electricity. Conservatively speaking, you can generate about 10 watts of solar energy/square foot. Electrically-speaking, you’ll need about 100 sq. ft. of solar panels for every kW you generate. The nationwide average cost for solar panels is $7 to $9 per watt. For the average size home, in a state with average sunlight, a 5 kW installed solar panel system will cost you about $25,000 to $35,000. I know that seems like a lot. But, you want to know the good news. The price of solar panels are dropping considerably year over year. In fact, in the next year or so, it’ll be feasible that you can purchase a system at $1 to $2 a watt (the solar companies are starting to get very aggressive with price drops to increase the number of people buying their systems). If we go off that scenario, a 5kW system could only cost you $10,000, with a 10-year payback. And considering the life of the system is at 25+ years, you’ll benefit from a huge return on investment.

In Conclusion

It’s a lot to think about, it’s a lot to research, and it’s a lot of money. But, it’s also a huge benefit to your wallet and a huge benefit to the environment. At the rate the use of solar energy is expanding, it’s a great bandwagon to be on. Once you get through the upfront, and you get through your payback period, you’re generating pure profit from your installed solar system. In the long run, what’s a few months of headache dealing with utility, solar, and roofing contractors, when you consider the benefits waiting for you over the next 25+ years.

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What is Solar Energy and How Do Solar Panels Work?

Solar energy works by capturing the sun’s energy and turning it into electricity for your home or business.

Our sun is a natural nuclear reactor. It releases tiny packets of energy called photons, which travel the 93 million miles from the sun to Earth in about 8.5 minutes. Every hour, enough photons impact our planet to generate enough solar energy to theoretically satisfy global energy needs for an entire year.

Currently photovoltaic power accounts for only five-tenths of one percent  of the energy consumed in the United States. But solar technology is improving and the cost of going solar is dropping rapidly, so our ability to harness the sun’s abundance of energy is on the rise.

A 2017 report from the International Energy Agency shows that solar has become the world’s fastest-growing source of power – marking the first time that solar energy’s growth has surpassed that of all other fuels. In the coming years, we will all be enjoying the benefits of solar-generated electricity in one way or another.

How Do Solar Panels Work?

When photons hit a solar cell, they knock electrons loose from their atoms. If conductors are attached to the positive and negative sides of a cell, it forms an electrical circuit. When electrons flow through such a circuit, they generate electricity. Multiple cells make up a solar panel, and multiple panels (modules) can be wired together to form a solar array. The more panels you can deploy, the more energy you can expect to generate.

What are Solar Panels Made of?

Photovoltaic (PV) solar panels are made up of many solar cells. Solar cells are made of silicon, like semiconductors. They are constructed with a positive layer and a negative layer, which together create an electric field, just like in a battery.

How Do Solar Panels Generate Electricity?

PV solar panels generate direct current (DC) electricity. With DC electricity, electrons flow in one direction around a circuit. This example shows a battery powering a light bulb. The electrons move from the negative side of the battery, through the lamp, and return to the positive side of the battery.

With AC (alternating current) electricity, electrons are pushed and pulled, periodically reversing direction, much like the cylinder of a car’s engine. Generators create AC electricity when a coil of wire is spun next to a magnet. Many different energy sources can “turn the handle” of this generator, such as gas or diesel fuel, hydroelectricity, nuclear, coal, wind, or solar.

AC electricity was chosen for the U.S. electrical power grid, primarily because it is less expensive to transmit over long distances. However, solar panels create DC electricity. How do we get DC electricity into the AC grid? We use an inverter.

What Does a Solar Inverter Do?

A solar inverter takes the DC electricity from the solar array and uses that to create AC electricity. Inverters are like the brains of the system. Along with inverting DC to AC power, they also provide ground fault protection and system stats, including voltage and current on AC and DC circuits, energy production and maximum power point tracking.

Central inverters have dominated the solar industry since the beginning. The introduction of micro-inverters is one of the biggest technology shifts in the PV industry. Micro-inverters optimize for each individual solar panel, not for an entire solar system, as central inverters do. This enables every solar panel to perform at maximum potential. When a central inverter is used, having a problem on one solar panel (maybe it’s in the shade or has gotten dirty) can drag down the performance of the entire solar array. Micro-inverters, such as the ones in SunPower’s Equinox home solar system, make this a non-issue. If one solar panel has an issue, the rest of the solar array still performs efficiently.

How Does a Solar Panel System Work?

Here’s an example of how a home solar energy installation works. First, sunlight hits a solar panel on the roof. The panels convert the energy to DC current, which flows to an inverter. The inverter converts the electricity from DC to AC, which you can then use to power your home. It’s beautifully simple and clean, and it’s getting more efficient and affordable all the time.

However, what happens if you’re not home to use the electricity your solar panels are generating every sunny day? And what happens at night when your solar system is not generating power in real time? Don’t worry, you still benefit through a system called “net metering.”

A typical grid-tied PV system, during peak daylight hours, frequently produces more energy than one customer needs, so that excess energy is fed back into the grid for use elsewhere. The customer gets credit for the excess energy produced, and can use that credit to draw from the conventional grid at night or on cloudy days. A net meter records the energy sent compared to the energy received from the grid. Find out more about net metering here.

By :- Vijay Kushwah

Information of Solar energy

1. What Is Solar Energy?
Solar energy is energy that comes from the sun. Every day the sun radiates, or sends out, an enormous amount of energy. The sun radiates more energy in one second than people have used since the beginning of time!
Where does all this energy come from? It comes from within the sun itself. Like other stars, the sun is a big gas ball made up mostly of hydrogen and helium. The sun generates energy in its core in a process called nuclear fusion. During nuclear fusion, the sun's extremely high pressure and hot temperature cause hydrogen atoms to come apart and their nuclei (the central cores of the atoms) to fuse or combine. Four hydrogen nuclei fuse to become one helium atom. But the helium atom weighs less than the four nuclei that combined to form it. Some matter is lost during nuclear fusion. The lost matter is emitted into space as radiant energy.
It takes millions of years for the energy in the sun's core to make its way to the solar surface, and then just a little over eight minutes to travel the 93 million miles to earth. The solar energy travels to the earth at a speed of 186,000 miles per second, the speed of light.
Only a small portion of the energy radiated by the sun into space strikes the earth, one part in two billion. Yet this amount of energy is enormous. Every day enough energy strikes the United States to supply the nation's energy needs for one and a half years!
Where does all this energy go? About 15 percent of the sun's energy that hits the earth is reflected back into space. Another 30 percent is used to evaporate water, which, lifted into the atmosphere, produce's rain-fall. Solar energy also is absorbed by plants, the land, and the oceans. The rest could be used to supply our energy needs.
2. History of Solar Energy
People have harnessed solar energy for centuries. As early as the 7th century B.C., people used simple magnifying glasses to concentrate the light of the sun into beams so hot they would cause wood to catch fire. Over 100 years ago in France, a scientist used heat from a solar collector to make steam to drive a steam engine.
In the beginning of this century, scientists and engineers began researching ways to use solar energy in earnest. One important development was a remarkably efficient solar boiler invented by Charles Greeley Abbott, an American astrophysicist, in 1936.
The solar water heater gained popularity at this time in Florida, California, and the Southwest. The industry started in the early 1920s and was in full swing just before World War 11. This growth lasted until the mid- 1950s when low-cost natural gas became the primary fuel for heating American homes. The public and world governments remained largely indifferent to the possibilities of solar energy until the oil shortages of the 1970s. Today people use solar energy to heat buildings and water and to generate electricity.
3. Solar Collectors and Solar Space Heating
Heating with solar energy is not as easy as you might think. Capturing sunlight and putting it to work is difficult because the solar energy that reaches the earth is spread out over a large area. The sun does not deliver that much energy to any one place at any one time . How much solar energy a place receives depends on several conditions. These include the time of day, the season of the year, the latitude of the area, and the clearness or cloudiness of the sky.
A solar collector is one way to collect heat from the sun. A closed car on a sunny day is like a solar collector. As sunlight passes through the car's glass windows, it is absorbed by the seat covers, walls, and floor of the car. The light that is absorbed changes into heat. The car's glass windows let light in, but don't let all the heat out. (This is also why greenhouses work so well and stay warm year-round.)
So, a solar collector does three things:

• it allows sunlight inside the glass (or plastic);
• it absorbs the sunlight and changes it into heat;
• it traps most of the heat inside.

Solar Space Heating
Space heating means heating the space inside a building. Today many homes use solar energy for space heating. There are two general types of solar space heating systems: passive and active. A "hybrid" system is a mixture of the passive and active systems.
Passive Solar Homes
In a passive solar home, the whole house operates as a solar collector. A passive house does not use any special mechanical equipment such as pipes, ducts, fans, or pumps to transfer the heat that the house collects on sunny days. Instead, a passive solar home relies on properly oriented windows. Since the sun shines from the south in North America, passive solar homes are built so that most of the windows face south. They have very few or no windows on the north side.
A passive solar home converts solar energy into heat just as a closed car does. Sunlight passes through a home's windows and is absorbed in the walls and floors.
To control the amount of heat in a passive solar house, the doors and windows are closed or opened to keep heated air in or to let it out. At night, special heavy curtains or shades are pulled over the windows to keep the daytime beat inside the house. In the summer, awnings or roof overhangs help to cool the house by shading the windows from the high summer sun.
Heating a house by warming the walls or floors is more comfortable than heating the air inside a house. It is not so drafty. And passive buildings are quiet, peaceful places to live. A passive solar home can get 50 to 80 percent of the heat it needs from the sun.
Many homeowners install equipment (such as fans to help circulate air) to get more out of their passive solar homes. When special equipment is added to a passive solar home, the result is called a hybrid system.
Active Solar Homes
Unlike a passive solar home, an active solar home uses mechanical equipment, such as pumps and blowers, and an outside source of energy to help heat the house when solar energy is not enough.
Active systems use special solar collectors that look like boxes covered with glass. Dark-colored metal plates inside the boxes absorb the sunlight and change it into heat. (Black absorbs sunlight more than any other color.)
Air or a liquid flows through the collectors and is warmed by this heat. The warmed air or liquid is then distributed to the rest of the house just as it would be with an ordinary furnace system.
Solar collectors are usually placed high on roofs where they can collect the most sunlight. They are also put on the south side of the roof where no tall trees or tall buildings will shade them.
Storing Solar Heat
The challenge confronting any solar heating system--whether passive, active, or hybrid--is heat storage. Solar heating systems must have some way to store the heat that is collected on sunny days to keep people warm at night or on cloudy days.
In passive solar homes, heat is stored by using dense interior materials that retain heat well--masonry, adobe, concrete, stone, or water. These materials absorb surplus heat and radiate it back into the room after dark. Some passive homes have walls up to one foot thick.
In active solar homes, heat may be stored in one of two ways--a large tank may store a hot liquid, or rock bins beneath a house may store hot air.
Houses with active or passive solar heating systems may also have furnaces, wood-burning stoves, or another heat source to provide heat in case there is a long period of cold or cloudy weather. This is called a backup system.
4. Solar Hot Water Heating
Solar energy is also used to heat water. Water heating is usually the second leading home energy expense, costing the average family over $400, a year. Depending on where you live, and how much hot water your family uses, a solar water heater can pay for itself in as little as five years. A well-maintained system can last 15-20 years, longer than a conventional water heater.
A solar water heater works in the same way as solar space heating. A solar collector is mounted on the roof, or in an area of direct sunlight. It collects sunlight and converts it to heat. When the collector becomes hot enough, a thermostat starts a pump. The pump circulates a fluid, called a heat transfer fluid, through the collector for heating. The heated fluid then goes to a storage tank where it heats water. The hot water may then be piped to a faucet or showerhead. Most solar water heaters that operate in winter use a heat transfer fluid, similar to antifreeze, that will not freeze when the weather turns cold.
Today over 1.5 million homes in the U.S. use solar heaters to heat water for their homes or swimming pools.
5. Solar Electricity
Besides heating homes and water, solar energy also can be used to produce electricity. Two ways to generate electricity from solar energy are photovoltaics and solar thermal systems.
Photovoltaic Electricity
Photovoltaic comes from the words photo meaning "light" and volt, a measurement of electricity. Sometimes photovoltaic cells are called PV cells orsolar cells for short. You are probably already familiar with solar cells. Solar-powered calculators, toys, and telephone call boxes all, use solar cells to convert light into electricity.
A photovoltaic cell is made of two thin slices of silicon sandwiched together and attached to metal wires. The top slice of silicon, called the N-layer, is very thin and has a chemical added to it that provides the layer with an excess of free electrons. The bottom slice, or P-layer, is much thicker and has a chemical added to it so that it has very few free electrons.
When the two layers are placed together, an interesting thing happens-an electric field is produced that prevents the electrons from traveling from the top layer to the bottom layer. This one-way junction with its electric field becomes the central part of the PV cell.
When the PV cell is exposed to sunlight, bundles of light energy known as photons can knock some of the electrons from the bottom P-layer out of their orbits through the electric field set up at the P-N junction and into the N-layer.
The N-layer, with its abundance of electrons, develops an excess of negatively charged electrons. This excess of electrons produces an electric force to push the additional electrons away. These excess electrons are pushed into the metal wire back to the bottom P-layer, which has lost some of its electrons.
This electrical current will continue flowing as long as radiant energy in the form of light strikes the cell and the pathway, or circuit, remains closed.
Current PV cell technology is not very efficient. Today's PV cells convert only about 10 to 14 percent of the radiant energy into electrical energy. Fossil fuel plants, on the other hand, convert from 30-40 percent of their fuel's chemical energy into electrical energy. The cost per kilowatt-hour to produce electricity from PV cells is presently three to four times as expensive as from conventional sources. However, PV cells make sense for many uses today, such as providing power in remote areas or other areas where electricity is difficult to provide. Scientists are researching ways to improve PV cell technology to make it more competitive with conventional sources.
Solar Thermal Electricity
Like solar cells, solar thermal systems use solar energy to make electricity. But as the name suggests, solar thermal systems use the sun's heat to do it.
Most solar thermal systems use solar collectors with mirrored surfaces to concentrate sunlight onto a receiver that heats a liquid. The super-heated liquid is used to make steam that drives a turbine to produce electricity in the same way that coal, oil, or nuclear power plants do.
Solar thermal systems may be one of three types: central receiver, dish, or trough. A central receiver system uses large mirrors on top of a high tower to reflect sunlight onto a receiver. This system has been dubbed a "solar power tower." Another system uses a dish-shaped solar collector to collect sunlight. This system resembles a television satellite dish. A third system uses mirrored troughs to collect sunlight. Until recently, trough systems seemed the most promising.
The world's first solar electric plant used mirrored troughs. LUZ, as the plant was called, was perfectly situated in the sunny Mojave desert of California. LUZ was the only solar plant to generate electricity economically. Dollar for dollar, it had always been cheaper to use conventional sources of energy (coal, oil, nuclear) to generate electricity. But the LUZ solar plant turned that around, producing electricity as cheaply as many new coal plants, and with no hidden pollution costs. The future looked bright for this pioneering solar plant and then the dream cracked. LUZ closed its doors at the end of 1992 because of a drop in oil prices and an over-budget construction project at LUZ's home-base.
LUZ may be gone, but most solar energy engineers believe solar power towers will be ready to take the place of trough systems very soon.
6. Solar Energy and the Environment
In the 1970s, the push for renewable energy sources was driven by oil shortages and price increases. Today, the push for renewable energy sources is driven by a renewed concern for the environment.
Solar energy is the prototype of an environmentally friendly energy source. It consumes none of our precious energy resources, makes no contribution to air, water, or noise pollution, does not pose a health hazard, and contributes no harmful waste products to the environment.
There are other advantages too. Solar energy cannot be embargoed or controlled by any one nation. And it will not run out until the sun goes out.

Solar energy is energy that comes from the sun. Every day the sun radiates, or sends out, an enormous amount of energy. The sun radiates more energy in one second than people have used since the beginning of time!
Where does all this energy come from? It comes from within the sun itself. Like other stars, the sun is a big gas ball made up mostly of hydrogen and helium. The sun generates energy in its core in a process called nuclear fusion. During nuclear fusion, the sun's extremely high pressure and hot temperature cause hydrogen atoms to come apart and their nuclei (the central cores of the atoms) to fuse or combine. Four hydrogen nuclei fuse to become one helium atom. But the helium atom weighs less than the four nuclei that combined to form it. Some matter is lost during nuclear fusion. The lost matter is emitted into space as radiant energy.
It takes millions of years for the energy in the sun's core to make its way to the solar surface, and then just a little over eight minutes to travel the 93 million miles to earth. The solar energy travels to the earth at a speed of 186,000 miles per second, the speed of light.
Only a small portion of the energy radiated by the sun into space strikes the earth, one part in two billion. Yet this amount of energy is enormous. Every day enough energy strikes the United States to supply the nation's energy needs for one and a half years!
Where does all this energy go? About 15 percent of the sun's energy that hits the earth is reflected back into space. Another 30 percent is used to evaporate water, which, lifted into the atmosphere, produce's rain-fall. Solar energy also is absorbed by plants, the land, and the oceans. The rest could be used to supply our energy needs.
2. History of Solar Energy
People have harnessed solar energy for centuries. As early as the 7th century B.C., people used simple magnifying glasses to concentrate the light of the sun into beams so hot they would cause wood to catch fire. Over 100 years ago in France, a scientist used heat from a solar collector to make steam to drive a steam engine.
In the beginning of this century, scientists and engineers began researching ways to use solar energy in earnest. One important development was a remarkably efficient solar boiler invented by Charles Greeley Abbott, an American astrophysicist, in 1936.
The solar water heater gained popularity at this time in Florida, California, and the Southwest. The industry started in the early 1920s and was in full swing just before World War 11. This growth lasted until the mid- 1950s when low-cost natural gas became the primary fuel for heating American homes. The public and world governments remained largely indifferent to the possibilities of solar energy until the oil shortages of the 1970s. Today people use solar energy to heat buildings and water and to generate electricity.
3. Solar Collectors and Solar Space Heating
Heating with solar energy is not as easy as you might think. Capturing sunlight and putting it to work is difficult because the solar energy that reaches the earth is spread out over a large area. The sun does not deliver that much energy to any one place at any one time . How much solar energy a place receives depends on several conditions. These include the time of day, the season of the year, the latitude of the area, and the clearness or cloudiness of the sky.
A solar collector is one way to collect heat from the sun. A closed car on a sunny day is like a solar collector. As sunlight passes through the car's glass windows, it is absorbed by the seat covers, walls, and floor of the car. The light that is absorbed changes into heat. The car's glass windows let light in, but don't let all the heat out. (This is also why greenhouses work so well and stay warm year-round.)
So, a solar collector does three things:

• it allows sunlight inside the glass (or plastic);
• it absorbs the sunlight and changes it into heat;
• it traps most of the heat inside.

Solar Space Heating
Space heating means heating the space inside a building. Today many homes use solar energy for space heating. There are two general types of solar space heating systems: passive and active. A "hybrid" system is a mixture of the passive and active systems.
Passive Solar Homes
In a passive solar home, the whole house operates as a solar collector. A passive house does not use any special mechanical equipment such as pipes, ducts, fans, or pumps to transfer the heat that the house collects on sunny days. Instead, a passive solar home relies on properly oriented windows. Since the sun shines from the south in North America, passive solar homes are built so that most of the windows face south. They have very few or no windows on the north side.
A passive solar home converts solar energy into heat just as a closed car does. Sunlight passes through a home's windows and is absorbed in the walls and floors.
To control the amount of heat in a passive solar house, the doors and windows are closed or opened to keep heated air in or to let it out. At night, special heavy curtains or shades are pulled over the windows to keep the daytime beat inside the house. In the summer, awnings or roof overhangs help to cool the house by shading the windows from the high summer sun.
Heating a house by warming the walls or floors is more comfortable than heating the air inside a house. It is not so drafty. And passive buildings are quiet, peaceful places to live. A passive solar home can get 50 to 80 percent of the heat it needs from the sun.
Many homeowners install equipment (such as fans to help circulate air) to get more out of their passive solar homes. When special equipment is added to a passive solar home, the result is called a hybrid system.
Active Solar Homes
Unlike a passive solar home, an active solar home uses mechanical equipment, such as pumps and blowers, and an outside source of energy to help heat the house when solar energy is not enough.
Active systems use special solar collectors that look like boxes covered with glass. Dark-colored metal plates inside the boxes absorb the sunlight and change it into heat. (Black absorbs sunlight more than any other color.)
Air or a liquid flows through the collectors and is warmed by this heat. The warmed air or liquid is then distributed to the rest of the house just as it would be with an ordinary furnace system.
Solar collectors are usually placed high on roofs where they can collect the most sunlight. They are also put on the south side of the roof where no tall trees or tall buildings will shade them.
Storing Solar Heat
The challenge confronting any solar heating system--whether passive, active, or hybrid--is heat storage. Solar heating systems must have some way to store the heat that is collected on sunny days to keep people warm at night or on cloudy days.
In passive solar homes, heat is stored by using dense interior materials that retain heat well--masonry, adobe, concrete, stone, or water. These materials absorb surplus heat and radiate it back into the room after dark. Some passive homes have walls up to one foot thick.
In active solar homes, heat may be stored in one of two ways--a large tank may store a hot liquid, or rock bins beneath a house may store hot air.
Houses with active or passive solar heating systems may also have furnaces, wood-burning stoves, or another heat source to provide heat in case there is a long period of cold or cloudy weather. This is called a backup system.
4. Solar Hot Water Heating
Solar energy is also used to heat water. Water heating is usually the second leading home energy expense, costing the average family over $400, a year. Depending on where you live, and how much hot water your family uses, a solar water heater can pay for itself in as little as five years. A well-maintained system can last 15-20 years, longer than a conventional water heater.
A solar water heater works in the same way as solar space heating. A solar collector is mounted on the roof, or in an area of direct sunlight. It collects sunlight and converts it to heat. When the collector becomes hot enough, a thermostat starts a pump. The pump circulates a fluid, called a heat transfer fluid, through the collector for heating. The heated fluid then goes to a storage tank where it heats water. The hot water may then be piped to a faucet or showerhead. Most solar water heaters that operate in winter use a heat transfer fluid, similar to antifreeze, that will not freeze when the weather turns cold.
Today over 1.5 million homes in the U.S. use solar heaters to heat water for their homes or swimming pools.
5. Solar Electricity
Besides heating homes and water, solar energy also can be used to produce electricity. Two ways to generate electricity from solar energy are photovoltaics and solar thermal systems.
Photovoltaic Electricity
Photovoltaic comes from the words photo meaning "light" and volt, a measurement of electricity. Sometimes photovoltaic cells are called PV cells orsolar cells for short. You are probably already familiar with solar cells. Solar-powered calculators, toys, and telephone call boxes all, use solar cells to convert light into electricity.
A photovoltaic cell is made of two thin slices of silicon sandwiched together and attached to metal wires. The top slice of silicon, called the N-layer, is very thin and has a chemical added to it that provides the layer with an excess of free electrons. The bottom slice, or P-layer, is much thicker and has a chemical added to it so that it has very few free electrons.
When the two layers are placed together, an interesting thing happens-an electric field is produced that prevents the electrons from traveling from the top layer to the bottom layer. This one-way junction with its electric field becomes the central part of the PV cell.
When the PV cell is exposed to sunlight, bundles of light energy known as photons can knock some of the electrons from the bottom P-layer out of their orbits through the electric field set up at the P-N junction and into the N-layer.
The N-layer, with its abundance of electrons, develops an excess of negatively charged electrons. This excess of electrons produces an electric force to push the additional electrons away. These excess electrons are pushed into the metal wire back to the bottom P-layer, which has lost some of its electrons.
This electrical current will continue flowing as long as radiant energy in the form of light strikes the cell and the pathway, or circuit, remains closed.
Current PV cell technology is not very efficient. Today's PV cells convert only about 10 to 14 percent of the radiant energy into electrical energy. Fossil fuel plants, on the other hand, convert from 30-40 percent of their fuel's chemical energy into electrical energy. The cost per kilowatt-hour to produce electricity from PV cells is presently three to four times as expensive as from conventional sources. However, PV cells make sense for many uses today, such as providing power in remote areas or other areas where electricity is difficult to provide. Scientists are researching ways to improve PV cell technology to make it more competitive with conventional sources.
Solar Thermal Electricity
Like solar cells, solar thermal systems use solar energy to make electricity. But as the name suggests, solar thermal systems use the sun's heat to do it.
Most solar thermal systems use solar collectors with mirrored surfaces to concentrate sunlight onto a receiver that heats a liquid. The super-heated liquid is used to make steam that drives a turbine to produce electricity in the same way that coal, oil, or nuclear power plants do.
Solar thermal systems may be one of three types: central receiver, dish, or trough. A central receiver system uses large mirrors on top of a high tower to reflect sunlight onto a receiver. This system has been dubbed a "solar power tower." Another system uses a dish-shaped solar collector to collect sunlight. This system resembles a television satellite dish. A third system uses mirrored troughs to collect sunlight. Until recently, trough systems seemed the most promising.
The world's first solar electric plant used mirrored troughs. LUZ, as the plant was called, was perfectly situated in the sunny Mojave desert of California. LUZ was the only solar plant to generate electricity economically. Dollar for dollar, it had always been cheaper to use conventional sources of energy (coal, oil, nuclear) to generate electricity. But the LUZ solar plant turned that around, producing electricity as cheaply as many new coal plants, and with no hidden pollution costs. The future looked bright for this pioneering solar plant and then the dream cracked. LUZ closed its doors at the end of 1992 because of a drop in oil prices and an over-budget construction project at LUZ's home-base.
LUZ may be gone, but most solar energy engineers believe solar power towers will be ready to take the place of trough systems very soon.
6. Solar Energy and the Environment
In the 1970s, the push for renewable energy sources was driven by oil shortages and price increases. Today, the push for renewable energy sources is driven by a renewed concern for the environment.
Solar energy is the prototype of an environmentally friendly energy source. It consumes none of our precious energy resources, makes no contribution to air, water, or noise pollution, does not pose a health hazard, and contributes no harmful waste products to the environment.
There are other advantages too. Solar energy cannot be embargoed or controlled by any one nation. And it will not run out until the sun goes out.

By :-  Vijay Kushwah