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We can change sunlight directly to electricity using solar cells. Every day, light hits your roof’s solar panels with photons (particles of sunlight). The solar panel converts those photons into electrons of direct current (“DC”) electricity. The electrons flow out of the solar panel and into an inverter and other electrical safety devices. The inverter converts that “DC” power (commonly used in batteries) into alternating current or “AC” power. AC power is the kind of electricity that your television, computer, and toasters use when plugged into the wall outlet.
Solar cells are small, square-shaped panel semiconductors made from silicon and other conductive materials, manufactured in thin film layers. When sunlight strikes a solar cell, chemical reactions release electrons, generating electric current. Solar cells are also called photovoltaic cells or “PV cells” and can be found on many small appliances such as calculators.
The word is used to explain how photovoltaic (PV) or solar electric technology work. First used in about 1890, the word has two parts: photo, a stem derived from the Greek phos, which means light, and volt, a measurement unit named after Alessandro Volta (1745-1827), a pioneer in the study of electricity. So, photovoltaic can literally be translated as light-electricity. And that’s just what photovoltaic materials and devices do; they convert light energy to electricity, as Edmond Becquerel and others discovered in the 18th Century.
When some semiconducting materials, such as certain kinds of silicon, are exposed to sunlight, they release small amounts of electricity. This process is known as the photoelectric effect. The photoelectric effect refers to the emission or ejection of electrons from the surface of a metal in response to light. It is the basic physical process in which a solar electric or photovoltaic (PV) cell converts sunlight to electricity.
Sunlight is made up of photons, or particles of solar energy. Photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum. When photons strike a PV cell, they may be reflected or absorbed, or they may pass right through. Only the absorbed photons generate electricity. When this happens, the energy of the photon is transferred to an electron in an atom of the PV cell (which is actually a semiconductor).
With its newfound energy, the electron escapes from its normal position in an atom of the semiconductor material and becomes part of the current in an electrical circuit. By leaving its position, the electron causes a hole to form. Special electrical properties of the PV cell—a built-in electric field—provide the voltage needed to drive the current through an external load (such as a light bulb).
A PV system is made up of different components. These include :
1) PV modules (groups of PV cells), which are commonly called PV panels.
2) One or more batteries.
3) A charge regulator or controller for a stand-alone system.
4) An inverter for a utility-grid-connected system and when alternating current (Ac) rather than direct current (Dc) is required, wiring.
5) Mounting hardware or a framework.
A PV system that is designed, installed, and maintained well will operate for more than 20 years. The basic PV module (interconnected, enclosed panel of PV cells) has no moving parts and can last more than 30 years. The best way to ensure and extend the life and effectiveness of your PV system is by having it installed and maintained properly. Experience has shown that most problems occur because of poor or sloppy system installation.
There are four main types of solar energy technologies:
1) Photovoltaic(PV) systems, which convert sunlight directly to electricity by means of PV cells made of semiconductor materials.
2) Concentrating solar power (CSP) systems, which concentrate the sun’s energy using reflective devices such as troughs or mirror panels to produce heat that is then used to generate electricity.
3) Solar water heating systems, which contain a solar collector that faces the sun and either heats water directly or heats a “working fluid” that, in turn, is used to heat water.
4) Transpired solar collectors, or “solar walls,” which use solar energy to preheat ventilation air for a building.
PV can be used to power your entire home’s electrical systems, including lights, cooling systems, and appliances. PV systems today can be blended easily into both traditional and nontraditional homes. The most common practice is to mount modules onto a south-facing roof or wall. For an additional aesthetic appeal, some modules resemble traditional roof shingles.
PV systems can be blended into virtually every conceivable structure for commercial buildings. You will find PV being used outdoors for security lighting as well as in structures that serve as covers for parking lots and bus shelters, generating power at the same time.
A photovoltaic (PV) system needs unobstructed access to the sun’s rays for most or all of the day. Shading on the system can significantly reduce energy output. Climate is not really a concern, because PV systems are relatively unaffected by severe weather. In fact, some PV modules actually work better in colder weather. Most PV modules are angled to catch the sun’s rays, so any snow that collects on them usually melts quickly. There is enough sunlight to make solar energy systems useful and effective nearly everywhere on earth.
The size of solar system you need depends on several factors such as how much electricity or hot water or space heat you use, the size of your roof, and how much you’re willing to invest. Also, do you want the system to supply your complete energy usage or to supplant a portion of your higher cost energy usage? You can contact a system designer/installer to determine what type of system would suit your needs.
: People decide to buy solar energy systems for a variety of reasons. For example, some individuals buy solar products to preserve the Earth’s finite fossil-fuel resources and to reduce air pollution. Others would rather spend their money on an energy-producing improvement to their property than send their money to a utility. Some people like the security of reducing the amount of electricity they buy from their utility, because it makes them less vulnerable to future increases in the price of electricity.
If it’s designed correctly, a solar system might be able to provide power during a utility power outage, thereby adding power reliability to your home. Finally, some individuals live in areas where the cost of extending power lines to their home is more expensive than buying a solar energy system.
You could install a photovoltaic (PV) or solar electric system yourself. But to avoid complications or injury, you will probably want to hire a reputable professional contractor with experience in installing solar systems. PV systems have few moving parts, so they require little maintenance. The components are designed to meet strict dependability and durability standards so they can stand up to the elements. However, they are fairly sophisticated electric systems, so installation usually requires the knowledge and experience of a licensed electrical equipment contractor.
Unfortunately, there is no single or simple answer. But a solar rebate and other incentives can reduce the cost of a PV system. This cost depends on a number of factors, such as whether it is a stand-alone system or is integrated into the building design, the size of the system, and the particular system manufacturer, retailer, and installer. For solar water heaters and space heaters, you also have to consider the price of the fuel used to back up the system. In most cases, you would have to add the cost of natural gas or electricity to get a more accurate estimate of how much you can expect to pay for a solar energy system.
It is also difficult to say how much you will save with a solar energy system, because savings depend on how much you pay for electricity and how much your utility will pay you for any excess power that you generate with your solar system. You can ask your solar system provider how much your new system will produce on an annual basis and compare that number to your annual electricity or hot water demand to get an idea of how much you will save.
A net energy meter (NEM) keeps track of all the power your solar system produces. Any solar energy that you do not use simultaneously with production will go back into the electrical grid through the meter. At night or on cloudy days, when your system is not producing more than your building needs, you will consume electricity from the grid as normal. Your utility will bill for the “net” consumption for any given billing period and credit you for any excess during a given period. You can carry your bill credit forward for up to a year.
At any time of the day, a customer’s solar system may produce more or less electricity than they need for their home or business. When the system’s production exceeds the customer demand, the excess energy generation automatically goes through the electric meter into the utility grid, running the meter backwards to credit the customer account. At other times of the day, the customer’s electric demand may be higher than what the renewable energy system is producing, and the customer relies on additional power needs from the utility. Switching between solar system’s power and the utility grid power is instantaneous and customers never notice any interruption in the flow of power.
NEM is your gateway to optimizing the rate of return on your solar investment.
• Allows customers to zero-out their bills.
• Credits customer accounts at full retail rates.
• Accurately captures energy generated and consumed, providing customers with annual performance data.
Customers that generate a net surplus of energy at the end of a twelve-month period can receive a payment for this energy under special utility tariffs.
As of date, 30 states and UTs in India have implemented the policy to support “Grid Connected” Solar PV. Almost all states in the country have their own net metering policies.
APPC – Average Pooled Purchase Cost
The general definition of APPC is the cost at which the Distribution Licensee has purchased the electricity including cost of self generation, if any, in the previous year from all the energy suppliers, long-term and short-term, but excluding those based on renewable energy sources, as the case may be. It will include cost of power from sources like coal, hydro etc . It varies from year to year and place to place but is usually between Rs 2- Rs 4.
Net metering policy across various states
|State||Applicable||System Size Allowed /Power Injection allowed||Rate of power export|
|Andhra Pradesh||Upto 1 MWp||100% of annual consumption||APPC|
|Assam||1 kWp to 1 MWp||40% of contract demand||APPC|
|Bihar||1kWp to 1 MWp||100% of contract demand||–|
|Chattisgarh||50kWp to 1 MWp||49% of annual net generation||50% of regulated solar tariff|
|Delhi||>1 kWp||100% of contract demand||APPC|
|Gujarat||>1 kW||50% of contract demand||APPC|
|Goat & UTs||1 kWp to 500 kWp||–||Regulated solar tariff|
|Haryana||Upto 1 MWp||90% of annual consumption||No payment|
|Himachal Pradesh||Upto 1 Mwp||80% of contract demand||Rs 4.5 to 5 / unit|
|Karnataka||Upto 1 MWp||–||Rs 9.56/unit (without subsidy)
Rs 7.20/unit (with 30% subsidy)
|Kerala||1 kWp to 1 MWp||–||APPC|
|Maharshtra||Upto 1 MWp||100% contract demand||APPC|
|Meghlaya||Upto 1 MWp||90% of annual consumption||No payment|
|Odisha||–||90% of annual consumption||No payment|
|Punjab||1kWp to 1 MWp||80% of contract demand||As per retail supply tariff of consumer category|
|Rajasthan||1 kWp to 1 MWp||80% of contract demand||Regulated solar tariff|
|Tamil Nadu||–||90% of annual consumption||No payment|
|Uttar Prdesh||>1 kWp||100% of contract demand||Rs 0.5/unit|
|Uttarakhand||Upto 500 kWp||–||Rs 9.2/unit|
|West Bengal||>5 kWp||90% of annual consumption||APPC|