Photovoltaic design and top rated solar panels


When designing a photovoltaic (PV) system, many factors should be considered. In the coming months, we will attempt to cover the important elements of designing a PV system.

Site Review

  • Expected irradiation (sunlight) available monthly at PV System location
  • Five year grid energy cost review – power usage by month, yearly grid cost increases
  • Available Space for the Solar Panels
  • Desired Energy Generation from PV System

PV System Review

  • Efficiency of solar panels
  • How solar panels are rated
  • Types of Solar Panels
  • Top rated solar panels
  • Complete list of Solar Panel Wattage Rating from California Energy Commission report July 2015
  • Cost of Solar Panels
  • Solar Panel Mounting System
  • Solar Panel Monitoring
  • How Power Inverters are Rated
  • Types of Power Inverters
  • Wiring
  • Expected life of PV System components
  • Maintenance costs
  • Component warranties
  • Cost benefit analysts of PV System compared to Grid
  • Installation Options

Site Review

Expected irradiation (sunlight) available monthly at your location

The best Photovoltaic (solar) Calculator I’ve found is provided by the NREL (National Renewable Energy Laboratory) of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy (our tax dollars at work 🙂

http://pvwatts.nrel.gov/

This amazing tool accepts an address within the U.S.A, integrates with Google Map Satellite images of house lots to estimate available surface area for Solar Panels. Then using sunlight patterns and weather history data, estimates solar radiation in kWh for each month of the year based on the solar array that will fit in the available space. Manual adjustments can be made to fine tune the estimated energy production.

Five year grid energy cost review – power usage by month, yearly grid cost increases

Coming Soon

Available Space for the Solar Panels

Solar panel come in different sizes and are rated by wattage output such as 180, 200 and 220-watts. If limited space is available, use solar panels with the highest rated power output for a particular physical size. Both mono- and poly-crystalline solar panels are good choices and should be reviewed.

Mono-crystalline solar panels are more expensive, but more space efficient. If you had one poly-crystalline and one mono-crystalline solar panel, both rated 220-watt, they would generate the same amount of electricity, but the one made of mono-crystalline silicon would take up less space.

Thin-film solar panels are the lowest cost solar panels currently available for power generation. Of course, additional space and mounting hardware is required. If micro inverters are used, additional micro inverters, solar panels, and wiring is required. These factors should be weighted when to evaluating total deployment costs.

Photovoltaic (PV) System Review

Efficiency of solar panels

The processes used to enhance the purity of silicon are costly. The efficiency of solar panels goes hand in hand with the purity of materials used to create the solar panel cells. Efficiency must be balanced with cost and panel size. Solar panels efficiency is a measurement of converting solar irradiation (Sun light) to electricity. Efficiencies range from as low as 10% for cheaper thin film panels, to 14-15% for poly crystalline panels and as high as 20% for panels that use advanced technologies (or combinations of technologies).

Using less efficient panels requires a larger number of panels to produce the same amount of solar electricity. The obvious case to use higher efficiency panels would be limited space for the panels.

How solar panels are rated

Two tests currently exist to rate solar panels – PTC (PVUSA Test Conditions) and STC (Standard Test Conditions). The State of California uses the PTC rating system within the California Solar Electric Incentive Program to rate solar panels. While PV manufacturers attempt to use the Standard Test Conditions (STC) rating for their products. All ratings are based on DC (direct current) watts.

PTC was developed to test and compare PV systems as part of the PVUSA (Photovoltaics for Utility Scale Applications) project. PTC are units of measure, equal to 1,000 watts per square meter of solar irradiance at 20 degrees C air temperature with a wind speed of 1 meter per second at 10 meters above ground level.

STC are units of measure, equal to 1,000 watts per square meter of solar irradiance at 25 degrees C, PV cell temperature, with air mass equal to 1.5, and ASTM G173-03 standard spectrum.

The PTC rating (which is lower than the STC rating) is generally recognized as a more realistic measure of PV output because the test conditions better reflect “real-world” solar and climatic conditions, compared to the STC rating.

Neither PTC nor STC account for all “real-world” losses. Actual solar systems will produce lower outputs due to soiling, shading, module mismatch, wire losses, inverter and transformer losses, shortfalls in actual nameplate ratings, panel degradation over time, and high temperature losses for arrays mounted close to or integrated within a roof line. These loss factors can vary by season, geographic location, mounting technique, azimuth, and array tilt. Examples of estimated losses from varying factors can be found at: http://pvwatts.nrel.gov/

Types of Solar Panels

Crystalline Silicon (c-Si)

Almost 90% of the World’s photovoltaics (PV) panels in use today are based on some variation of silicon. In 2011, about 95% of all shipments by U.S. manufacturers to the residential sector were crystalline silicon solar panels. The silicon used in PV takes many forms. The main difference is the purity of the silicon.

But what does silicon purity really mean? The more perfectly aligned the silicon molecules are, the better the solar cell will be at converting solar energy (sunlight) into electricity (the photoelectric effect). Crystalline silicon forms the basis of mono- and poly-crystalline silicon solar cells.

Mono-crystalline Silicon Solar Cells

Solar cells made of mono-crystalline silicon (mono-Si), also called single crystalline silicon (single-crystal-Si), are quite easily recognizable by an external even coloring and uniform look, indicating high-purity silicon.

Mono-crystalline solar cells are made out of silicon ingots, which are cylindrical in shape. To optimize performance and lower costs of a single mono-crystalline solar cell, four sides are cut out of the cylindrical ingots to make silicon wafers, which is what gives mono-crystalline solar panels their characteristic look.

A good way to separate mono and poly-crystalline solar panels is that poly-crystalline solar cells look perfectly rectangular with no rounded edges.

Advantages

  • Mono-crystalline solar panels have the highest efficiency rates since they are made out of the highest-grade silicon. The efficiency rates of mono-crystalline solar panels are typically 15-20%.
  • Mono-crystalline silicon solar panels are space-efficient. Since these solar panels yield the highest power outputs, they also require the least amount of space compared to any other types. Mono-crystalline solar panels produce up to four times the amount of electricity as thin-film solar panels.
  • Mono-crystalline solar panels live the longest. Most solar panel manufacturers put a 25-year warranty on their mono-crystalline solar panels.
  • They perform better than poly-crystalline solar panels in low-light conditions.

Disadvantages

  • Mono-crystalline solar panels are higher cost. From a financial standpoint, a solar panel that is made of poly-crystalline silicon (and in some cases thin-film) can be a better choice when space is available.
  • Based on the circuit of a solar panel, if cells are partially covered with shade, dirt or snow, a section of the panel does not produce energy. Micro-inverters .vs central inverter can monitor the output of each panel and reduce the impact of share on the entire solar array.
  • The Czochralski process is used to produce mono-crystalline silicon. It results in large cylindrical ingots. Four sides are cut out of the ingots to make silicon wafers. A significant amount of the original silicon ends up as waste.
  • All solar panels are impacted by extremely warm weather.  Mono-crystalline solar panels are less impacted while Poly-crystalline solar panels are more impacted by increased temperatures.

Poly-crystalline Silicon Solar Cells

The first solar panels based on poly-crystalline silicon, which also is known as poly-silicon (p-Si) and multi-crystalline silicon (mc-Si), were introduced to the market in 1981. Unlike mono-crystalline based solar panels, poly-crystalline solar panels do not require the Czochralski process. Raw silicon is melted and poured into a square mold, which is cooled and cut into perfectly square wafers.

Advantages

  • The process used to make poly-crystalline silicon is simpler and cost less. The amount of waste silicon is less compared to mono-crystalline.
  • Poly-crystalline solar panels tend to have lower heat tolerance than mono-crystalline solar panels. This technically means that they perform worse than mono-crystalline solar panels in high temperatures. Heat can affect the performance of solar panels and shorten their lifespans.

Disadvantages

  • The efficiency of poly-crystalline based solar panels is typically 13-16%. Because of lower silicon purity, poly-crystalline solar panels are not as efficient as mono-crystalline solar panels.
  • Lower space-efficiency. You generally need to cover a larger surface to output the same electrical power as you would with a solar panel made of mono-crystalline silicon.

String Ribbon Solar Cells

String Ribbon solar panels are made from poly-crystalline silicon. String Ribbon is the name of a manufacturing process used to produce a form of poly-crystalline silicon. Temperature-resistant wires are pulled through molten silicon, which results in very thin silicon ribbons. Solar panels made with this technology looks similar to traditional poly-crystalline solar panels.

Advantages

  • The manufacturing of String Ribbon solar panels required half the amount silicon as mono-crystalline manufacturing. This contributes to lower costs.

Disadvantages

  • The manufacturing of String Ribbon solar panels is more costly.
  • Efficiency is at best on par with the low-end poly-crystalline solar panels at around 13-14%. In research laboratories, researchers have pushed the efficiency of String Ribbon solar cells as high as 18.3%.
  • String Ribbon solar panels have the lowest space-efficiency of crystalline-based solar panels.

Thin-Film Solar Cells (TFSC)

Depositing one or several thin layers of photovoltaic material onto a substrate is the basic gist of how thin-film solar cells are manufactured. They are also known as thin-film photovoltaic cells (TFPV). The different types of thin-film solar cells can be categorized by which photovoltaic material is deposited onto the substrate:

  • Amorphous silicon (a-Si)
  • Cadmium telluride (CdTe)
  • Copper indium gallium selenide (CIS/CIGS)
  • Organic photovoltaic cells (OPC)

Depending on the technology, thin-film module prototypes have reached efficiencies between 7–13% and production modules operate at about 9%. Future module efficiencies are expected to climb close to the about 10–16%.

The market for thin-film PV grew at a 60% annual rate from 2002 to 2007. In 2011, close to 5% of U.S. photovoltaic module shipments to the residential sector were based on thin-film.

Advantages

  • Mass-production is simple. This makes them potentially cheaper to manufacture than crystalline-based solar cells.
  • Their homogenous appearance makes them look more appealing.
  • Can be made flexible, which opens up many new potential applications.
  • High temperatures and shading have less impact on solar panel performance.
  • In situations where space is not an issue, thin-film solar panels can make sense.

Disdvantages

  • Thin-film solar panels are in general not useful for many residential situations.They are low cost, but require a lot of space.
  • Low space efficiency increases other PV deployment costs (e.g. support structures and cables) will increase.
  • Thin-film solar panels tend to degrade faster than mono- and polycrystalline solar panels, which is why they typically come with a shorter warranty.

Solar panels based on amorphous silicon, cadmium telluride and copper indium gallium selenide are currently the only thin-film technologies that are commercially available on the market.

Amorphous Silicon (a-Si) Solar Cells

Because the output of electrical power is low, solar cells based on amorphous silicon have traditionally only been used for small-scale applications such as in pocket calculators. However, recent innovations have made them more attractive for some large-scale applications too.

With a manufacturing technique called “stacking”, several layers of amorphous silicon solar cells can be combined, which results in higher efficiency rates (typically around 6-8%).

Only 1% of the silicon used in crystalline silicon solar cells is required in amorphous silicon solar cells. On the other hand, stacking is expensive.

Cadmium Telluride (CdTe) Solar Cells

Cadmium telluride is the only thin-film solar panel technology that has surpassed the cost-efficiency of crystalline silicon solar panels in a significant portion of the market (multi-kilowatt systems).

The efficiency of solar panels based on cadmium telluride usually operates in the range 9-11%.

First Solar has installed over 5 gigawatts (GW) of cadmium telluride thin-film solar panels worldwide. The same company holds the world record for CdTe PV module efficiency of 14.4%.

Copper Indium Gallium Selenide (CIS/CIGS) Solar Cells

Compared to the other thin-film technologies above, CIGS solar cells have showed the most potential in terms of efficiency. These solar cells contain less amounts of the toxic material cadmium that is found in CdTe solar cells. Commercial production of flexible CIGS solar panels was started in Germany in 2011.

The efficiency rates for CIGS solar panels typically operate in the range 10-12 %.

Many thin-film solar cell types are still early in the research and testing stages. Some of them have enormous potential, and we will likely see more of them in the future.

Building Integrated Photovoltaics (BIPV)

Integrated photovoltaics can be placed on facades, roofs, windows, walls and other areas. Rather than an individual type of solar cell technology, building integrated photovoltaics have several subtypes (or different methods of integration), which can be based on both crystalline-based and thin-film solar cells allowing more area of a structure to be covered with PV material. This increased area provides can generate additional energy that is not possible using solar panels.

Top rated solar panels

Kyocera KD315GX-LPB

This solar panel received top marks for high solar efficiency. At 16 percent, this solar panel is not the most efficient on the market, but it ranks high. (Silicon-based solar cells like this one usually operate at an efficiency of 18 percent or lower, according to the University of Pennsylvania.) The Kyocera KD315GX-LPB panels are durable and come with a complete five-year warranty. The company guarantees that the panels’ power output will remain at 80 percent of the minimum power promised by manufacturers for at least 20 years.

The panels meet industry standards for withstanding loads (it can hold up under 113 pounds per square foot of pressure from snow or ice on the roof) and can handle a beating by hailstones with a 1-inch diameter in winds of up to 51 mph.

The Kyocera panels are easy to maintain, requiring occasional cleaning with water and mild detergent and an annual check of the connections and hardware.

The company provides answers to frequently asked questions on its website and will respond to individual queries by phone and email.

Canadian Solar CS6X-305M

Canadian solar offers its panels in 50 countries. The company’s Canadian Solar CS6X-305M model took second place for power, durability and visual appeal. The efficiency of these panels is rated at 15.9 percent, barely behind the No. 1 Kyocera model. The Canadian panels also meet industry standards for durability and are able to handle up to 113 pounds of snow per square foot. The warranty guarantees 95 percent output for one year, and 80 percent output for 25 years.

The model is advertised as self-washing. That means that with a sufficient roof angle, rain will keep dirt and dust off the solar panel surface. Owners may need to take a sponge and soapy water to the panels on occasion.

Canada Solar offers support by phone and by email, and the company’s website includes some information on frequently asked questions. Canada Solar offers a 10-year warranty on materials and workmanship.

Grape Solar 390W

Grape Solar is a Eugene, Oregon-based company founded in 2009. It makes solar panels, largely manufactured in Asia but assembled in the United States. The Grape Solar 390W panel has an efficiency percentage of 15.21 and can handle 50 pounds of snow per square foot. The warranty promises 90-percent power output for 10 years and 80-percent output for 25 years. Grape works with Costco and Home Depot and has a network of installers throughout the United States.

These solar panels can be cleaned with just water, no soap necessary. You can also contact the company via email or get in touch with the its technical team through a customer hotline.

Hyper X Solar

Hyper X Solar distributes Sunpreme Bifacial N-Type solar panels developed in Silicon Valley California by SmartSilicon HCT (Hybrid Cell Technology) and manufactured in China. SmartSilicon has created a frameless, bifacial cell architecture which places solar cells on both front and back of the panel. Yes, you read that right!

Solar panels generate energy from sunlight not heat. Material in solar cells generate energy when electrons are excited by visible or invisible sunlight spectrum. SmartSilicon claims indirect light reflections allow the backside of the solar panel to generate power increasing panel energy output and space efficiency.

Hummm, I’ll I can say about this claim is “let’s see the data, please”. The California Energy Commission report dated July 2015, states the Sunpreme SNPM-GxB-370 has one of the highest PTC ratings.

Hyper X states the Sunpreme double glass panels offer lower thermal coefficient of efficiency, providing a greater output at high operating temperatures.

Sanyo Solar

coming soon – one of the top panel mfg

SunPower Solar

coming soon – one of the top panel mfg

Solar Panel Wattage Ratings

The California Energy Commission report dated July 2015 contains information on over 15,000 solar panels. I’ve placed the data within an Excel file for easy sorting and searching. Excel and PDF formats available.

Cost of Solar Panels

coming soon

Solar Panel Mounting Systems

coming soon

Solar Panel Monitoring

coming soon

How Power Inverters are rated

coming soon

Power Inverter Options

SolarEdge inverters

In addition to using SmartSilicon HCT (Sunpreme) panels, Hyper X uses inverters which offer panel level power optimization and monitoring from SolarEdge similar to Enphase micro inverters. SolarEdge claims to having deployed over two million units in the field. An NREL (National Renewable Energy Laboratories) study performed by PV Evolutions Labs determined that SolarEdge inverter/power optimizers outperformed both Enphase micro inverters and string inverters in shaded environments.

More coming soon

Wiring

coming soon

Expected life span of PV System Components

coming soon

Maintenance Costs

coming soon

Component Warranties

coming soon

Cost Benefit Analysts of PV System compared to Grid

coming soon

Installation Options

coming soon

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