How Do Solar Panel Work?

What is a Solar Cell – Monocrystalline-Polycrystalline

Semiconductors are the special materials which make up a “Solar” or “Photovoltaic” cell of which the most common used is “Silicon”. When light source energies strike the cell(s) a part of the source is absorbed by the semiconductor material which loosens electrons allowing them to move freely.

Silicon is a poor conductor of electricity so further ingredients, such as phosphorous and boron are added to the mix to create the “semiconductor”. Adding these ingredients allows the silicon to conduct electricity and also allows electrons freed by the light absorption to flow in a certain direction. Placing metal contacts on the top and bottom of the solar cell allows the current generated to be drawn of and used to perform work.

Monocrystalline/Polycrystalline Solar Collectors are modules consisting of an aluminium framed sheet of highly durable low reflective, tempered glass that has had individual solar cells adhered to the inner glass surface which are wired together in a series parallel configuration so as to obtain the necessary voltage and current.

Monocrystalline/Polycrystalline individual cells are wired in series strings to increase the module’s voltage and the series strings are wired in parallel to increase the current of the module. Glass or Tedler sheeting is used to protect the back of the cells and form the back of the module.

The parallel connections are brought through the back of the Monocrystalline/Polycrystalline protective sheeting and then connected to a weather proof junction box which is a permanent mount on the back of the Monocrystalline/Polycrystalline module. This junction box is where the output connections are made.

Several Monocrystalline/Polycrystalline solar modules wired together are what forms the solar panel/collector.

There are two types of solar cells – Monocrystalline & Polycrystalline which are the technologies used today form solar panels.

Monocrystalline (single crystal) solar cells are cut from a silicon boule that is grown from a single crystal – this means the crystal has been grown in only one plane or direction. Monocrystalline are more expensive to manufacture and have a slightly higher efficiency than do the Polycrystalline cells which has the result of smaller individual cell and thus typically a slightly smaller module.

Polycrystalline solar cells are created from multicrystalline technology and are cut from silicon boule that has grown from multifaceted crystalline material – a crystal that has grown in multiple directions. Polycrystalline solar cells have slightly lower efficiency which results in a larger individual cell and therefore creates a larger module.

The advent of new silicon nitride Polycrystalline (multycrystalline) cells has made efficiency even higher than similar sized Monocrystalline (polycrystalline) cells.

It is always important to remember that 100 watt Monocrystalline/Polycrystalline module is a 100 watt module whether it is made from Monocrystalline cells or Polycrystalline cells.

April 25, 2011 Posted by | Uncategorized | Leave a Comment

How MPPT Solar Controller Work

Here is where the optimization, or maximum power point tracking comes in. Assume your battery is low, at 12 volts. A MPPT Solar Controller takes that 17.6 volts at 7.4 amps and converts it down, so that what the battery gets is now 10.8 amps at 12 volts. Now you still have almost 130 watts, and everyone is happy.

Ideally, for 100% power conversion you would get around 11.3 amps at 11.5 volts, but you have to feed the battery a higher voltage to force the amps in. And this is a simplified explanation – in actual fact the output of the MPPT charge controller might vary continually to adjust for getting the maximum amps into the battery.

On the left is a screen shot from the Maui Solar Software “PV-Design Pro” computer program (click on picture for full size image). If you look at the green line, you will see that it has a sharp peak at the upper right – that represents the maximum power point. What an MPPT controller does is “look” for that exact point, then does the voltage/current conversion to change it to exactly what the battery needs. In real life, that peak moves around continuously with changes in light conditions and weather.

A MPPT Solar Controller tracks the maximum power point, which is going to be different from the STC (Standard Test Conditions) rating under almost all situations. Under very cold conditions a 120 watt panel is actually capable of putting over 130+ watts because the power output goes up as panel temperature goes down – but if you don’t have some way of tracking that power point, you are going to lose it. On the other hand under very hot conditions, the power drops – you lose power as the temperature goes up. That is why you get less gain in summer.

MPPT’s are most effective under these conditions:

Winter, and/or cloudy or hazy days – when the extra power is needed the most.

Cold weather – solar panels work better at cold temperatures, but without a MPPT you are losing most of that. Cold weather is most likely in winter – the time when sun hours are low and you need the power to recharge batteries the most.
Low battery charge – the lower the state of charge in your battery, the more current a MPPT puts into them – another time when the extra power is needed the most. You can have both of these conditions at the same time.
Long wire runs – If you are charging a 12 volt battery, and your panels are 100 feet away, the voltage drop and power loss can be considerable unless you use very large wire. That can be very expensive. But if you have four 12 volt panels wired in series for 48 volts, the power loss is much less, and the controller will convert that high voltage to 12 volts at the battery. That also means that if you have a high voltage panel setup feeding the controller, you can use much smaller wire.

The Power point tracker is a high frequency DC to DC converter. They take the DC input from the solar panels, change it to high frequency AC, and convert it back down to a different DC voltage and current to exactly match the panels to the batteries. MPPT’s operate at very high audio frequencies, usually in the 20-80 kHz range. The advantage of high frequency circuits is that they can be designed with very high efficiency transformers and small components. The design of high frequency circuits can be very tricky because the problems with portions of the circuit “broadcasting” just like a radio transmitter and causing radio and TV interference. Noise isolation and suppression becomes very important.

There are a few non-digital (that is, linear) MPPT’s charge controls around. These are much easier and cheaper to build and design than the digital ones. They do improve efficiency somewhat, but overall the efficiency can vary a lot – and we have seen a few lose their “tracking point” and actually get worse. That can happen occasionally if a cloud passed over the panel – the linear circuit searches for the next best point, but then gets too far out on the deep end to find it again when the sun comes out. Thankfully, not many of these around any more.

The power point tracker (and all DC to DC converters) operates by taking the DC input current, changing it to AC, running through a transformer (usually a toroid, a doughnut looking transformer), and then rectifying it back to DC, followed by the output regulator. In most DC to DC converters, this is strictly an electronic process – no real smarts are involved except for some regulation of the output voltage. Charge controllers for solar panels need a lot more smarts as light and temperature conditions vary continuously all day long, and battery voltage changes.

April 23, 2011 Posted by | Uncategorized | Leave a Comment

What Advantage of MPPT solar controller

What Advantage of MPPT solar controller?

In any applications which PV module is energy source, MPPT solar controller is used to correct for detecting the variations in the current-voltage characteristics of solar cell and shown by I-V curve.

MPPT solar controller is necessary for any solar power systems need to extract maximum power from PV module; it forces PV module to operate at voltage close to maximum power point to draw maximum available power.

MPPT solar controller allows users to use PV module with a higher voltage output than operating voltage of battery system.
For example, if PV module has to be placed far away from charge controller and battery, its wire size must be very large to reduce voltage drop. With a MPPT solar controller, users can wire PV module for 24 or 48 V (depending on charge controller and PV modules) and bring power into 12 or 24 V battery system. This means it reduces the wire size needed while retaining full output of PV module.

MPPT solar controller reduces complexity of system while output of system is high efficiency. Additionally, it can be applied to use with more energy sources. Since PV output power is used to control DC-DC converter directly.

MPPT solar controller can be applied to other renewable energy sources such as small water turbines, wind-power turbines, etc.

April 20, 2011 Posted by | Uncategorized | Leave a Comment

What is MPPT solar controller

1.What is MPPT Meaning ?
MPPT Meaning maximum power point tracker.

a high efficiency DC to DC converter that presents an optimal electrical load to a solar panel or array and produces a voltage suitable for the load.most commonly for a solar panel or array, and converts the power to a voltage or current level which is more suitable to whatever load the system is designed to drive.

Panel tracking – this is where the panels are on a mount that follows the sun. The most common are the Zomeworks and Wattsun. These optimize output by following the sun across the sky for maximum sunlight. These typically give you about a 15% increase in winter and up to a 35% increase in summer.

This is just the opposite of the seasonal variation for MPPT Solar Controller. Since panel temperatures are much lower in winter, they put out more power. And winter is usually when you need the most power from your solar panels due to shorter days.

Maximum Power Point Tracking is electronic tracking – usually digital. The charge controller looks at the output of the solar panel, and compares it to the battery voltage. It then figures out what is the best power that the panel can put out to charge the battery. It takes this and converts it to best voltage to get maximum AMPS into the battery. (Remember, it is Amps into the battery that counts). Most modern MPPT’s are around 93-97% efficient in the conversion. You typically get a 20 to 45% power gain in winter and 10-15% in summer. Actual gain can vary widely depending weather, temperature, battery state of charge, and other factors.

Grid tie systems are becoming more popular as the price of solar drops and electric rates go up. There are several brands of grid-tie only (that is, no battery) inverters available. All of these have built in MPPT. Efficiency is around 94% to 97% for the MPPT conversion on those.

April 19, 2011 Posted by | Uncategorized | Leave a Comment

185w Solar Panel

185w solar panel, mono crystalline solar panel

185W Solar Panel FeaturesHigh Efficiency
CE,TUV junction box
Lifetime:25 years
Warranty:2 years
90% power 10 years
80% power 20 years

185W Solar Panel SpecificationModel                                                                CNCB185W-24
Nominal power Pm                                        185W
Power allowance                                            ±3%
Optimized working voltage Vm                     37.0V
Optimized working current Im                       5.00A
Open circuit voltage Voc                                 44.4V
Short circuit current Isc                                   5.92A
Module efficiency                                             13.50%
Withstanding voltage                                       DC1000V
Dimension of module (mm)                          1580*808*35
Net weight (kg)                                                 15.0

April 18, 2011 Posted by | Uncategorized | Leave a Comment