The Benefits of Renewable Energy Credits

The United States has several companies that are currently developing new renewable energy projects that include the study of photovoltaic or solar power. These projects are financed from renewable energy credits. The definition of a renewable energy credit is a tradable unit that is a representative of a commodity. The commodity represented is a form of environmental attributes of a unit of renewable energy or a generated unit of electricity. There are many benefits to collecting renewable energy credits.

One of the major benefits of earning renewable energy credits is that this is a tradable commodity. Renewable energy credits can be traded in order to reduce projects from fossil fuel sources. The REC’s or renewable energy credits can be used in order to host an environmental friendly event. An event that was created from these credits is the “Carbon Neutral” conference.

The renewable energy credits are used by participants to pay for their travel expenses. Renewable energy credits are used with mandated programs such as renewable energy portfolio standards. What this entails is that a percentage from energy sales must be derived from a natural, renewable resource. An example of a practice of the renewable energy portfolio is understood when discussing energy practices in the state of Maine. In Maine thirty percent of the amount of electricity generated must be from a renewable source such as solar energy.

The United States government along with governments around the world have been finding out that renewable resources are essential to ensuring a future energy resource. Our energy resources become more and more depleted each day. Fossil fuels are quickly disappearing. It is very important to start using and rewarding the use of renewable sources of energy such as a photovoltaic system.

A photovoltaic system can generate enough energy for the whole world. This type of system is a valuable resource for our energy demands and the energy demands of our children. We must choose energy sources, like photovoltaic systems, that are not only natural but renewable. These are the energy sources of the future.

Solar Energy and the Future

An advantage to solar power is that it can reduce expenses. It can also be portable. When one is backpacking in the wilderness or traveling far from power grids, solar power can provide a means of powering electronic equipment.

Another advantage is, of course, the lack of pollution created by solar energy production. In fact, if all of our electrical energy were produced by such means, we might not be worrying about global warming and the other destructive effects of pollution on our environment.

These threats to our environment also pose a threat to mankind. Solar power could be developed to a point where it, along with other forms of renewable energy, would replace harmful means of electricity production.

It isn't necessarily impossible to have a clean and safe Earth. We just have to work on it.

What is Photovoltaic Conversion?

Photo means "light." It comes from the Greek word “phos,” which means "light."“Voltaic” means, "producing electric current." The word comes from the name of Alessandro Volta, an Italian physicist who was a pioneer in the field of electricity during the 1700's. (His name is also where the word "volt" comes from.)

Photovoltaic means, "creating electrical energy when exposed to light."A “cell” is a device that produces electricity. An example of an electrical cell is a flashlight battery.Photovoltaic cells produce electricity when they are exposed to light. They usually consist of panels. The panels contain two layers of different materials.

When light hits these two layers, one of the layers becomes positively charged, and the other becomes negatively charged.

This works similarly to a regular flashlight battery, which has a positive end and a negative end. When a wire connects the two ends, they produce an electric current.When the two layers of material in a solar cell are exposed to light, they create an electric current.

The AMOUNT of electricity generated by a solar power cell depends on several factors.

Mainly:

-How big is the solar power device, and how much surface is exposed to the sun?

-How strong is the sun? (This depends on time of day, weather, latitude, etc.)

-How long is the solar power device exposed?

-How much impediment is there to the light? (Clouds, mist, dust, dirt, etc.)

In other words, a solar power cell generates electricity faster when the sun (or light) is brighter. A device with larger solar panels will produce more electricity than one with smaller panels. Exposing the cell for a longer period of time will create more electricity than exposing it for a shorter period of time. A panel near the equator will be more effective than one in an arctic region. A solar panel in misty or dusty conditions does not create as much electricity as it would in full, unobstructed sun.

Some solar cells produce only enough current to power small electronic devices, but can be "daisy-chained" (connected together) in order to create more electricity for other items.

Solar cells which produce enough electricity to run larger equipment (such as laptops) may be larger, more expensive, or heavier than the others.But there are many varieties available.

Individuals and companies are consistently striving to create lighter and more efficient portable solar cells.

What is Solar Thermal Conversion?

Solar thermal conversion systems use reflectors or mirrors to concentrate sunlight to extremely intense levels of heat. (Solar means "of the sun," thermal means "of heat" and conversion means "changing something from one form to another.")

You can understand this better if you consider the example of using a magnifying glass to start a fire. You may have heard of this or even tried it before. You can hold a magnifying glass under the sun, and concentrate the light on a small pile of flammable materials. The magnifying glass will make the sun's heat much stronger, and will light the materials on fire. It has been said that a magnifying glass one meter in diameter, held under the sun, will create a ray hot enough to melt stone.

If you would hold a magnifying glass flat under the sun and put your hand under it, you would need to move your hand away very quickly in order to avoid burning yourself.

Solar thermal conversion systems use mirrors or reflectors to concentrate sunlight onto containers full of liquid. Sometimes water is used. Sometimes other liquids are used, which retain heat better than water.

The liquids are heated up to high temperatures, and this produces steam. The steam is used to turn a turbine. The turning motion of the turbine is used to create electricity.

How does a rotating motion create electricity? When you set up a coiled wire or similar device to rotate between two magnets, it generates an electric current. This is how electric generators work, as well as windmills, nuclear power plants, and other energy plants which use such things as coal, gas, or petroleum.

Windmills use the wind to create the turning motion. Nuclear power or fossil fuels are used to heat water up, thus creating steam to turn the turbines.

Solar heating is another form of solar thermal conversion. In solar heating, an absorber is used to take in sunlight and convert it to heat. The absorber could be something simple, like black paint, or it could be a special ceramic material. A heat absorber is considered to a be good one when it collects at least 95 percent of the sun's radiation.

The absorbers are then used to heat a fluid, which is then circulated to warm up buildings or to create hot-water supplies.

What is Solar Energy?

Light (particularly sunlight) can be used to create heat or generate electrical power. This is referred to as solar energy.It is a clean form of energy production, which doesn't pollute the environment as some other forms of energy production do.There are two forms of solar energy. The first is solar thermal conversion, which uses sunlight to create heat and then electrical power. The second is photovoltaic conversion, which uses sheets of special materials to create electricity from the sun. "Photo-" means "light," and "voltaic" means "producing electricity."

Trouble Shooting Solar Panel Problems

You bought a solar panel system and after a while you notice that your solar panels are not living up to the standards that your sales representative claimed when they were sold to you, it may not be a faulty panel. There could be a number of issues plaguing them and making your blood pressure sky rocket. Don’t panic or send the panels to the landfill, here are some reasons why your panels are not working correctly.

Position is keyAre your panels facing the right direction toward the sun? Almost all panels need to be adjusted through the year at least 3 times. this is so that they can be in the optimal position for maximum absorption. For completely stationary panels, make sure they are facing south in the northern hemisphere and north in the southern hemisphere. the reason is that sun is never directly straight up from where you standing. unless you are on the equator your panels should always have a tilt in the direction of the sun. Some systems have automatic trackers, they rotate as the sun crosses the sky, these are optimal, because even at sun rise and sun set the panels on a stationary panel setup will not be in direct sunlight. It is best to grab every last drop of sun.

Clean upOne of the major problems people face with solar panels is dirt, a solar panel system is not a set up and forget, dirt or dust will cover the glass making the crystals inside useless. Like the windows in your home, if there is dirt on them, you can’t see out very well, and it progressively can get worse through time. It is necessary to clean off your solar panels by wiping them off, maybe even using Windex if needed, try not to leave streaks because they also will keep the sun from passing through.

Cloudy dayClouds in the sky will bring your solar intake to 30%. Solar panels require focused light, clouds defuse the solar rays. On a cloudy day your electricity will run by the utilities again or if off grid a backup generator system. People who live in places that are normally cloudy should find an alternative energy source because the price of solar will not be justifiable.

ObstructionsShading from a tree, a branch, your hand, any shading, even a small corner or something as big as a leaf will cut your solar intake by 75%. The full panel needs to be in direct light, there is no compromising this issue. Even stand in front of the panel will put a dent in the intake of solar energy for as long as the panel is covered. Clear all trees away from your solar array that can block the sun. The best place to put a solar array is in a clear open area of the yard or on the roof of your home. Hale, rocks, or bullets are common culprits of damage to panels making them un-usable. In the off chance a bullet hits your solar panel, electricity and money saving is not your highest priority. There are no quick fixes to damaged panels; you may need to replace them completely depending on the severity of the damage. Replacing the glass is your best bet at fixing cracked glass on a solar panel, note that you need to make sure there is no moisture between the glass and the crystal because the glass will fog when the panel is heated. If the crystal is cracked or broken, replace the panel.

Could it be wiring?If these have been solved and you still don’t get the energy, check the cable connectors between the panels and batteries or your house. These may not be connected correctly, faulty or loose.

The batteries could also be a problem; they may be damaged or not able to hold a charge. If you do not understand what might be wrong ask a technician or the company who installed them. If there is a problem, check the panels and work your way back. There could be several things wrong with the system if it is hooked up wrong, do not discount operator error.

And finally, after all is said and done, and your panels are the culprit, replace them. Check warranty or call your provider.

The Seven Solar Myths

Learning About PV: The Myths of Solar Electricity
Solar electric, otherwize known as photovoltaics (PV), is a great business in the us. It is good on its promise of "delivering clean, reliable, on-demand power."

Pogress and research continues, better positioning current and next-generation photovoltaic (PV) technologies to meet future electricity needs. But these successes seem to spark some criticisms and questions. Some are warranted. Some are based on partial truths. And others are perpetuated from urban legends or myths about the technology.

The seven myths of solar electricity:

Myth 1:

Solar electricity cannot serve any significant fraction of U.S. or world electricity needs.
PV technology can meet electricity demand on any scale. The solar energy resource in a 100-mile-square area of Nevada could supply the United States with all its electricity (about 800 gigawatts) using modestly efficient (10%) commercial PV modules.

A more realistic scenario involves distributing these same PV systems throughout the 50 states. Currently available sites—such as vacant land, parking lots, and rooftops—could be used. The land requirement to produce 800 gigawatts would average out to be about 17 x 17 miles per state. Alternatively, PV systems built in the "brownfields"—the estimated 5 million acres of abandoned industrial sites in our nation's cities—could supply 90% of America's current electricity.

These hypothetical cases emphasize that PV is not "area-impaired" in delivering electricity. The critical point is that PV does not have to compete with baseload power. Its strength is in providing electricity when and where energy is most limited and most expensive. It does not simply replace some fraction of generation. Rather, it displaces the right portion of the load, shaving peak demand during periods when energy is most constrained and expensive.
In the long run, the U.S. PV Industry Roadmap does expect PV to provide a "significant fraction of U.S. electricity needs." This adds up to at least 15% of new added electricity capacity in 2020, and then 10 years later, at least 10% of the nation's total electricity.

Myth 2:

Solar electricity can do everything — right now!
No way. Solar electricity will eventually become a major player in the world's energy portfolio. The industry just doesn't have the capacity to meet all demands right now. But assuming that the proper investments are made now and are sustained, the industry will become significant in the next few decades.

In 2000, for example, worldwide PV shipments grew by 37% from the previous year. In 2001, they grew by another 38%. Although this brought shipments to about 400 megawatts per year, it's hardly enough to meet the entire burden of U.S. or world electricity needs... yet.

Myth 3:

Photovoltaics cannot significantly offset environmental emissions.
PV systems produce no atmospheric emissions or greenhouse gases. Compared to fossil-generated electricity, each kilowatt of PV electricity annually offsets up to:
16 kilograms of nitrogen oxides
9 kilograms of sulfur oxides
2,300 kilograms of carbon dioxide (CO2)
If the industry grows by the 25% per year as predicted PV in the United States will offset 10 million metric tons of CO2 per year by 2027 — equivalent to the annual increase emitted by U.S. fossil fuel electricity generation. This means that the emission rate will become negative thereafter as the PV contribution grows!

Myth 4:

Photovoltaics is a polluting industry.
The PV industry is neither "squeaky clean" nor a major environmental, safety, or health problem. When it comes to emissions, PV's electricity-generating portion of the fuel cycle is the clear winner versus fossil fuel sources. However, semiconductor processing can involve the use of chemicals and toxic materials.

Some 80% of the current PV industry is silicon. Basically, it uses the same processing as the semiconductor industry, which is touted as being comparatively clean. It also has the same risk. There are various codes, controls, and regulations in place that oversee PV silicon industry operations, ensuring that it's relatively safe.

PV materials that incorporate heavy metals or toxic materials are continuously scrutinized to ensure safety. To date, the Environmental Protection Agency, Underwriters Laboratories, and others have conducted testing and investigations that indicate no problems. But the programs and companies involved remain vigilant and active in ensuring safety. Industry has made many improvements in areas such as:
Safer etching
Lead-free solders
Automated handling and robotics
Redundancy in ensuring critical operations
Stringent training

Myth 5:

Photovoltaics is merely a cottage industry, appealing only to small niche markets.

This is a real business — one that has been growing by more than 35% per year over the past 2 years. In 2001, PV module shipments closed in on the 400-megawatt mark, representing a $2.5 to $3 billion market. The U.S.-based industry itself is now approaching $1 billion per year and providing 25,000 jobs. It's expected to grow to the $10-$15 billion level in the next 20 years, providing 300,000 jobs by 2025. This sustained growth exceeds that of the semiconductor industry.

A market shift has sparked the recent growth in the PV industry. It has shifted from almost completely remote, off-grid, and consumer products to nearly 60% grid-connected, distributed power. And these applications don't represent small niche markets. They represent the significant growth path for PV — the true distributed power source.

Myth 6:

PV is too expensive and will never compete with "the big boys" of power generation. Besides, you can never get the energy out that it takes to produce the system.

The cost of producing PV modules, in constant dollars, has fallen from as much as $50 per peak watt in 1980 to as little as $3 per peak watt today. This causes PV electricity costs to drop 15¢-25¢ per kilowatt hour (kWh), which is competitive in many applications.

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 energy payback period is also dropping rapidly. For example, it takes today's typical crystalline silicon module about 4 years to generate more energy than went into making the module in the first place. The next generation of silicon modules, which will employ a different grade of silicon and use thinner layers of semiconductor material, will have an energy payback of about 2 years. And thin-film modules will soon bring the payback down to one year or less. This means that these modules will produce "free" and clean energy for the remaining 29 years of their expected life.

Myth 7:

Nothing remains to be done. Essential R&D is complete, the product works — just close the laboratory doors and let industry fight it out.

As high-tech energy production, PV has immense potential to evolve, develop, and advance. Our current technologies still have substantial potential for improvement.

Research and development (R&D) in processing, process understanding, and manufacturing remains in its infancy. There is much important R&D still to be performed, not just on cells and modules, but also on balance-of-systems components and on systems themselves.

Many new and next-generation materials, devices, and physics are only concepts. Others are still to be discovered. Among these will be authentic breakthroughs that will boost PV to the next levels of performance. It is up to us to make and manage the investments to own these. Delays in making these investments will mean lost opportunities. First, it will take longer to bring this clean energy source into widespread use for us and our descendants. Also, there will be a loss of technology leadership and ownership.

Failing to take R&D leadership creates a pathway of diminished U.S. innovation, technology ownership, and energy ownership and control, as well as the loss of substantial economic benefits. Investing in PV R&D and clean solar electricity for you.

Solar thermal devices use direct heat from the sun, concentrating it in some manner to produce heat at useful temperatures. The modern solar industry began with the oil embargo of 1973-1974 and was strengthened with the second embargo in 1979. The growth of the solar industry during this period of fuel shortages and high prices (1974-1984) soared from 45 solar collector manufacturing firms to 225 firms.The solar market was helped during this period by government assistance, both Federal and State. Currently, solar thermal devices do everything from heating swimming pools to creating steam for electricity generation.

What is Polycrystalline Silicon?

Polycrystalline Silicon - also referred to as "polysilicon" or "Poly-Si" is a material consisting of multiple small silicon crystals and has long been used as the conducting gate material in MOSFET and CMOS processing technologies. For these technologies, Polycrystalline Silicon is deposited using LPCVD reactors at high temperatures and is usually heavily n or p-doped. The main advantage of Polycrystalline Silicon over other types of silicon is that the mobility can be orders of magnitude larger and the material also shows greater stability under electric field and light-induced stress. This allows far more complex, high-speed electrical circuits that can be created on the glass substrate along with the amorphous silicon devices, which are still needed for their low-leakage characteristics.

When Polycrystalline Silicon and Amorphous Silicon devices are used in the same process, this is called "hybrid processing."

A complete Polycrystalline Silicon active layer process is also used in some cases where a small pixel size is required, such as in projection displays.

What is Monocrystalline Silicon?

Monocrystalline Silicon is made from very pure Monocrystalline Silicon. Monocrystalline Silicon has a single and continuous crystal lattice structure with practically zero defects or impurities.

One of the many reasons Monocrystalline Silicon is superior to other types of silicon cells are their high efficiencies - which are typically around 15%.

Because the manufacturing process required to produce Monocrystalline Silicon is more involved and detailed than other types, this results in slightly higher costs for Monocrystalline Silicon than other silicon technologies.

Solar Industry Associations

American Solar Energy Society
http://www.ases.org/
Established in 1954, the American Solar Energy Society (ASES) is the nonprofit organization dedicated to increasing the use of solar energy, energy efficiency, and other sustainable technologies in the U.S.

Solar Energy Industries Association
http://www.seia.org/
Established in 1974, SEIA works to expand the use of solar technologies, strengthen research and development, remove market barriers, and improve education and outreach for solar.

Florida Solar Energy Industries Association
http://www.flaseia.org/
The Florida Solar Energy Industries Association (FlaSEIA), founded in 1977, is a nonprofit professional association of companies involved in the solar energy industry. Members include manufacturers, distributors, contractors, retailers and consultants who provide solar water heating, pool heating and solar electric systems. Research Centers and Utilities also are members.

Solar Electric Power Association
http://www.solarelectricpower.org/
The Solar Electric Power Association is a nonprofit organization, formed in 1992 as the Utility Photovoltaic Group. From national events to one-on-one assistance, SEPA is the go-to resource for unbiased and actionable solar intelligence. SEPA is comprised of 375 utility and solar industry members. Breaking down information overload into business reality, SEPA takes the time and risk out of implementing solar business plans and helps turn new technologies into new opportunities.

Solar Glossary

A-RACK
Holds glass on both sides. A shape structure configuration.

ACCUM
Work in Progress (WIP) Buffer

Al/Ag
Aluminum and gold are used in solar cell production to conduct electricity and reflect light.

AMORPHOUS SEMICONDUCTOR
Is the non-crystalline semiconductor material that has no long-range order.
A non-crystalline semiconductor material, that is cheaper than crystalline, but less efficient and slowly degrades over time. Also known as thin film.

AMORPHOUS SILICON (a-Si)
Non-crystalline allotropic form of silicon in which the atoms are disordered from optimum crystalline positions. To compensate for the resulting “dangling bonds,” hydrogen is alloyed with silicon.
AUTOCLAVE
Pressurized device designed to heat aqueous solutions above their boiling point to achieve sterilization. Autoclaving is used to improve adhesiveness between the PVB and glass substrates by removing trapped air.
BACK CONTACT
ZnO:Al
Zinc oxide and aluminum are used to prevent alloy formation between the silicon and metal layers. Aluminum and gold are used in solar cell productions to conduct electricity and reflect light. Ensures no gridlines or visible tabs are present on the front of the cells.
Creates a uniform appearance, unrestricted by reflectance.

BALANCE OF SYSTEM (BOS)
Mounting Structure
Cabling
Inverter
Land/Others
Maintenance
BUS
Bus Wire Attachment tool automatically installs the tabbing wire and the bus wire.
Cd-Te
Cadmium Telluride: a type of thin-film solar cell design that uses a cadmium-tellurium compound as the semiconductor layer.

CIS (CIGS)
Copper Indium Diselenide: a type of thin film solar cell material that uses a compound of copper, indium, selenium. A fourth element, gallium, may also be added to the compound (CIGS) to achieve higher performance in PV cells.
CELL
The solar cell is the basic electrical device in solar power. Multiple cells are wired together to form modules of the needed area.

CRYSTALLINE SILICON (c-Si)
A generic term for solar cell technology that uses a substrate of purified silicon in a crystalline structure. Gray color and metallic luster increase with crystal size.
Has properties similar to glass in that it is strong, brittle, and has a tendency to chip.
CVD
Plasma-Enhanced Chemical Vapor Deposition Tool (PECVD).
Substrates are exposed to one or more volatile precursors, which react and/or decompose on the substrate surface to produce the desired deposit.

CVD ABATEMENT
Tool used to abate toxic gases.
CVD PUMP
Tool used to pump process lines.
FAB300
MES (manufacturing execution system) software used to optimize factory performance.

GW
Gigawatt: One thousand (1000) MW

GWp
Giga Watt peak (1,000 MWp); solar industry unit for normal power.
HS20
Cutting liquid (glycol based).

HSEM Hand Seam Inspection
Used to round the edges and corners of the glass to reduce damage and improve factory yields.

INVERTER
An inverter allows DC power from solar panels to supply AC power that is normally supplied from a main power source or grid electricity.

JBX
Junction box attachment tool installs the J-Box, solder J-Box leads, and J-Box lid used to attach PV-Instant Seal Bond line.

JUNCTION BOX
Used to protect soldered electrical connections between the output and cables.
Provide an output wiring for the solar module.

KG
Kilogram

KM
Kilometer

KW
Kilowatt: 1,000 watts of electrical output.

Kerf Loss
Kerf loss is associated with the amount of material loss during a cutting process. In crystalline wafer production, kerf loss refers to the amount of silicon consumed as part of the wafering process and plays a vital role in determining the overall dimension, edge quality, and surface finish of a wafer.

LCD
Liquid Crystal Display.

LED
Light emitting diode.

LASER SCRIBE
Multiple lasers per system with indexing optics direct laser towards the glass at appropriate scribe separation.
First Laser – removes selected semiconductor and metal electrode layers (TCO) from the substrate.
Second Laser – etches a groove for the contact area for both the metal and transparent electrode (a-Si) layers.
Third Laser – produces a contact area groove for both the metal and a-Si layers

MM
Millimeter

mm2
Millimeter square

MW
Megawatt: One million watts, or 1,000 KW.

MWp
Megawatt peak (1MWp=1,000 kilowatt peak); a measuring unit for normal power output of solar cells in the solar industry.

MICRON
One-millionth of a meter, or 1,000 nanometers

MICRO-CRYSTALLINE
Is a crystallized substance or rock which contains small crystals that are visible through microscopic examination. i.e. Microcrystalline Silicon (µc-Si)

MICRO-CRYSTALLINE SILICON (µc-Si)
A form of thin film silicon with very small (0.5-2 micron) grain structure intermixed with amorphous silicon. It is usually deposited in a thin layer (typically 1-3 microns) for tandem (stacked) thin film solar cells.

MODULE
The solar module is the final packaged PV generator.

MONO-CRYSTALLINE SILICON
Crystalline silicon in which the wafer is cut from a single silicon crystal with a perfect crystalline lattice structure. Also used for Integrated Circuits.

MULTI-CRYSTALLINE SILICON
Crystalline Silicon in which the wafer is made from silicon that has been melted and cast into blocks, creating a structure of many large silicon crystal grains.

PECVD
Plasma enhanced chemical vapor deposition: a glow discharge based deposition technology used to form many kinds of coatings, including both a-Si (amorphous silicon) and SiN (silicon nitride) layers for solar cells.

PERCENT EFFICIENCY
% Efficiency = Electrical Energy / Sunlight Energy

PHOTOVOLTAIC (PV)
PV devices convert sunlight directly to electrical current
Relating to, or utilizing the generation of a voltage when radiant energy falls on the boundary between dissimilar substances (as two different semiconductors).

POLYVINYL BUTYRAL (PVB)
Shock-absorbing safety interlayer in safety glazing.
Safety glazing to provide features such as solar energy control, weight reduction by eliminating one glass layer (called a bi-layer structure), head-up displays in automobiles and liquid crystal and electro-chromic devices for privacy applications.

PV
See Photovoltaic

PVD
Physical Vapor Deposition or "sputtering" is a process by which a thin film of material is deposited on a substrate according to the following sequence of steps:
1. Deposited material is converted into vapor by physical means.
2. Vapor is transported across a region of low pressure from its source to the substrate.
3. Vapor undergoes condensation on the substrate to form the thin film.
A type of deposition method in which atoms are detached from a target of a certain material and then deposited on a substrate.

Si
Silicon

SRU
Slurry recovery unit

SINGLE-CRYSTAL SILICON
See mono-crystalline silicon

SINGLE JUNCTION
Single layer p-n junction diode (monocrystalline silicone c-Si)

SOLAR FARM
Solar power plants that generate electricity by converting solar energy to heat, to drive a thermal power plant.

SYSTEM COST
Module Cost + Balance of System

t
Tons

TANDEM JUNCTION
Amorphous silicon and crystalline combined in thin layers, creating a layered cell.
Tandem solar cells designs use multiple light absorbing/semiconducting materials to increase conversion efficiency.

TCO
Transparent Conducting Oxide: this is typically the top active layer in a solar cell and is often made of zinc oxide or tin oxide. It needs to be transparent to allow light transmission, but be electrically conducive.

THIN FILM
Are thin material layers ranging from fractions of a nanometer to several micrometer thick.

TRANSPARENT CONDUCTIVE OXIDE (TCO)
Typically the top active layer in a solar cell and is often made of zinc oxide or tin oxide. It is transparent to allow light transmission and be electrically conductive.
In general, TCO thin films are transparent electrodes either polycrystalline or amorphous, except for single crystals which are grown epitaxially and exhibit a resistivity in an order of 10-3 Ω cm or less with an average transmittance above 80% in the visible range.

µm
An abbreviated form of micrometer. A unit of length equal to one millionth of a meter.

Wire Saw
Slices mono and polycristalline bricks into wafers

ZnO:Al
Zinc oxide and aluminum are used to prevent alloy formation between silicon and metal layers.

Will Solar Work at My Location?

Solar is universal and will work virtually anywhere, however some locations are better than others. Irradiance is a measure of the sun's power available at the surface of the earth and it averages about 1000 watts per square meter. With typical crystalline solar cell efficiencies around 14-16%, that means we can expect to generate about 140-160W per square meter of solar cells placed in full sun. Insolation is a measure of the available energy from the sun and is expressed in terms of "full sun hours" (i.e. 4 full sun hours = 4 hours of sunlight at an irradiance level of 1000 watts per square meter). Obviously different parts of the world receive more sunlight from others, so they will have more "full sun hours" per day. The solar insolation zone map on the right will give you a general idea of the "full sun hours per day" for your location.

How do Solar Cells Generate Electricity?

Photovoltaics or PV for short can be thought of as a direct current (DC) generator powered by the sun. When light photons of sufficient energy strike a solar cell, they knock electrons free in the silicon crystal structure forcing them through an external circuit (battery or direct DC load), and then returning them to the other side of the solar cell to start the process all over again. The voltage output from a single crystalline solar cell is about 0.5V with an amperage output that is directly proportional to cell's surface area (approximately 7A for a 6 inch square multicrystalline solar cell). Typically 30-36 cells are wired in series (+ to -) in each solar module. This produces a solar module with a 12V nominal output (~17V at peak power) that can then be wired in series and/or parallel with other solar modules to form a complete solar array to charge a 12, 24 or 48 volt battery bank.

Three Generations of Photovoltaics

First Generation

The first generation photovoltaic, consists of a large-area, single layer p-n junction diode, which is capable of generating usable electrical energy from light sources with the wavelengths of solar light. These cells are typically made using silicon wafer. First generation photovoltaic cells (also known as silicon wafer-based solar cells) are the dominant technology in the commercial production of solar cells, accounting for more than 86% of the solar cell market.

Second Generation

The second generation of photovoltaic materials is based on the use of thin-film deposits of semiconductors. These devices were initially designed to be high-efficiency, multiple junction photovoltaic cells. Later, the advantage of using a thin-film of material was noted, reducing the mass of material required for cell design. This contributed to a prediction of greatly reduced costs for thin film solar cells. Currently there are different technologies /semiconductor materials under investigation or in mass production, such as amorphous silicon, poly-crystalline silicon, micro-crystalline silicon, cadmium telluride, copper indium selenide /sulfide. Typically, the efficiencies of thin-film solar cells are lower compared to bulk silicon (wafer-based) solar cells, but manufacturing costs are also lower, so that a lower price in terms of $/watt of electrical output can be achieved. Another advantage of the reduced mass is that less support is needed when placing panels on rooftops and it allows fitting panels on light materials or flexible materials, even textiles.

Third Generation

Third generation photovoltaics are very different from the other two, broadly defined as semiconductor devices which do not rely on a traditional p-n junction to separate photogenerated charge carriers. These new devices include photoelectrochemical cells, Polymer solar cells, and nanocrystal solar cells.

Selecting a Solar Cell Type

For all practical purposes, how the different types of solar cells work in applications is very similar. What is important when buying panels is to choose the right panel based on how much power you need, how much room you have, and where they will be mounted. They will all do the same thing - make electricity when the sun hits them. Thin film are often less efficient, so will take up more room for the same power, but on the other hand they work better in hot climates due to not losing quite as much at high temperatures and are less expensive to manufacture.

You will see some manufacturers and websites claiming that panel XX is better because it is more efficient at low light. While it is true that monocrystalline ARE better, the difference in average daily production is less than 1%. If you have low light, you also have low sun energy. So converting 15% of very little is not much better than converting 14% of very little. So, yes, it is true, but about #18 on the list of things to worry about when buying solar panels.

Types of Solar Cells

Monocrystalline - made from a single large crystal, cut from ingots. Most efficient, but also the most expensive. Somewhat better in low light conditions (but not as good as some advertising hype would have you believe).

Polycrystalline - basically, cast blocks of silicon which may contain many small crystals. This is probably the most common type right now. Slightly less efficient than single crystal, but once set into a frame with 35 or so other cells, the actual difference in watts per square foot is not much.

Amorphous - "thin film", here the silicon is spread directly on large plates, usually of something like stainless steel. Cheaper to produce, but often much less efficient, which means larger panels for the same power. Unisolar is one example.

Vaporware - this is the 4th type - the one that pops up in the news about every 3 months, proclaiming the next major breakthrough that will make plastic spray on solar cells that will cost around 5 cents a watt, or some similar claim. None have reached production to date.

What is a Solar Cell?

A solar cell or a " photovoltaic" cell, is a device that converts photons from the sun into electricity. In general, a solar cell that includes both solar and non-solar sources of light (such as photons from incandescent bulbs) is termed a photovoltaic cell. Fundamentally, the device needs to fulfill only two functions: photo generation of charge carriers (electrons and holes) in a light-absorbing material, and separation of the charge carriers to a conductive contact that will transmit the electricity. This conversion is called the photovoltaic effect, and the field of research related to solar cells is known as photovoltaics.

Solar cells have many applications. Historically solar cells have been used in situations where electrical power from the grid is unavailable, such as in remote area power systems, Earth orbiting satellites, consumer systems, e.g. handheld calculators or wrist watches, remote radiotelephones and water pumping applications. Recently solar cells are particularly used in assemblies of solar modules (photovoltaic arrays) connected to the electricity grid through an inverter, often in combination with a net metering arrangement.

Solar cells are regarded as one of the key technologies towards a sustainable energy supply.

The History of Photovoltaics

The term "photovoltaic" comes from the Greek Word meaning "light", and the name of the Italian physicist Volta, after whom the volt (and consequently voltage) are named. It means literally of light and electricity.

The photovoltaic effect was first recognized in 1839 by French physicist Alexandre-Edmond Becquerel. However, it was not until 1883 that the first solar cell was built, by Charles Fritts, who coated the semiconductor selenium with an extremely thin layer of gold to form the junctions. The device was only around 1% efficient. Russell Ohl patented the modern solar cell in 1946. Sven Ason Berglund had a prior patent concerning methods of increasing the capacity of photosensitive cells. The modern age of solar power technology arrived in 1954 when Bell Laboratories, experimenting with semiconductors, accidentally found that silicon doped with certain impurities was very sensitive to light.

This resulted in the production of the first practical solar cells with a sunlight energy conversion efficiency of around 6 percent. This milestone created interest in producing and launching a geostationary communications satellite by providing a viable power supply. Russia launched the first artificial satellite in 1957, and the United States' first artificial satellite was launched in 1958. Russian Sputnik 3, launched on 15 May 1957, was the first satellite to use solar arrays. This was a crucial development which diverted funding from several governments into research for improved solar cells.

Applications and implementation

Solar cells are often electrically connected and encapsulated as a module. PV modules often have a sheet of glass on the front (sun up) side with a resin barrier behind, allowing light to pass while protecting the semiconductor wafers from the elements. Solar cells are also usually connected in series in modules, creating an additive voltage. Connecting cells in parallel will yield a higher amperage. Modules are then interconnected, in series or parallel, or both, to create an array with the desired peak DC voltage and amperage.