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solar charge controllers
Solar charge controllers are an integral part of your solar powered system to protect your batteries' life.It limits the rate of current drawn or charged by the batteries.The terms "Charge controller","Solar Regulators","charge regulator" or a "battery regulator" may refer to a stand alone device or as an integrated circuit within the battery pack.
A stand alone charge controller can be of two types- Series charge controller or shunt charge controller.
A series charge controller disables further current flow into the batteries when they are full whereas, a shunt regulator diverts excess electricity to a "shunt" load when the batteries are full.
In a nut shell, solar charge controllers :
Solar charge controller technologies
There are two technologies - PWM solar charge controllers and MPPT charge controllers. We have a detailed FAQ section explaining about them,pros and cons etc.
how do solar charge controllers charge the batteries
Most charge controllers manage 3,4, or 5 different stages of battery charging cycles to charge the batteries at different times and at different battery voltages.
The most common battery charging cycles are:
Bulk Charge: This first stage of battery charging is used whenever your batteries are low on energy. Most charge controllers automatically begin bulk charging as soon as power is drawn from the battery bank. In this stage, current is sent to the batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level.
Absorption Charge: This 2nd stage of battery charging is used to safely bring your battery bank up to 100%. Voltage remains constant and current gradually tapers off as internal resistance increases during charging.
Float Charge: The 3rd stage of battery charging is a "maintenance" charge cycle. After your batteries have reached full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. It's main purpose is to keep an already charged battery from discharging. PWM, or "pulse width modulation" accomplishes the same thing. In PWM, the controller or charger senses tiny voltage drops in the battery and sends very short charging cycles (pulses) to the battery. This may occur several hundred times per minute. It is called "pulse width" because the width of the pulses may vary from a few microseconds to several seconds.
Equalization Charge: Some charge controllers are capable of a manually engaged equalization charge on wet lead acid batteries. Equalizing refers to an overcharge performed on flooded lead-acid batteries after they have been fully charged. This maintenance step helps eliminate stratification and sulfation. This charge cycle should always be done while you are present to monitor your batteries, as they can release excessive amounts of gas, or become overheated during this process. Make sure to carefully follow all battery, and charge controller manufacturer instructions.
The following illustration shows how a typical three stage charge controller works (illustration courtesy of Xantrex Technologies):
In India, the energy crisis, MNRE support, and a growing social awareness with respect to solar energy has attracted land owners, government nodal agencies,promoters and investors to set up solar farms.Apart from small and more compact PV installations, solar farms contain larger PV modules installed in groups of parallel and series connection.These module banks are installed next to a substation and from there, the solar power generated is fed through the grid.There are Balance of Systems ( BOS) interconnected and the power produced depends upon the number modules installed.Most of the manufacturers price solar cables by the foot.All the wires are stranded. Solar cables include wires,cables, battery & panel interconnect,battery interconnect cables,inverter cables.
How to choose solar cable and wires for solar installation?
These are the basic criteria for choosing a solar cable :
Since the solar panels are installed in the outdoor, cables that interconnect panels and connection boxes should be able to function well from room temperature to 90 deg c with a life of 30 years.
PV installations are exposed to all extremes of atmospheric weather conditions.They are exposed to ultraviolet radiation and humidity.Therefore solar PV cables should be resistant to adverse weather conditions without compromising on the functional characteristics.
The solar cables should withstand Adverse weather conditions and offer mechanical and electrical characteristics.The wires and cables must be chosen in such a way that maximum current rating must not be exceeded. Cables are rated according to current rating in amps that can safely pass along .The higher the current, the thicker the wire.If the wrong type of cable is used, they might catch fire.
cables should be designed to assure protection against fire.They should also provide adequate protection against pests and offer mechanical aggression.
Where to buy solar cables and wires?
To find out manufacturers,suppliers of solar cables and wires in India,China,Taiwan and other countries, please click here.
Solar junction box
A solar junction box is an enclosure that is placed on the back side of the solar panel.Its main function is to convert the current carrying ribbon from the panel into cable and or connectors.
solar junction box
Bypass diode in a SPV module
The purpose of the solar junction box,other than converting the ribbon into cable ,is to protect the solar PV panels to make it more effective.The main component of the junction box is the bypass diode.
Bypass diodes are connected in a PV module as shown in the figure.They form an integral part of a solar junction box,when the panels are connected in series.
In normal conditions,current will flow through the module without going through the diodes.However,in cases, when a particular cell is covered by shadow or bird dropping or by leaves, the efficiency of the cell is reduced or the cell stops producing the current,since sunlight cannot penetrate through the cell.In such cases, the cell may become very hot or in extreme cases, it may even breakdown, bring down the efficiency of the entire module.It is under these circumstances, the diode that is connected in parallel to the disabled cell,allows the current to flow through itself.Hence the name "bypass diode".
See the illustrated figures below for better understanding.
Blocking diodes in Solar PV systems
The function of diodes in a PV system is different depending on where they are installed.When diodes are installed in series with a string of modules,they are called blocking diodes .They block the reverse flow of current from the battery through the modules at night ,thus preventing battery discharge.Blocking diodes are included in the construction of solar panels and a must for any solar Pv systems that uses batteries to charge and discharge the power during night.
How to select the right solar junction box ?
A good solar junction box should exhibit the following characteristics:
Solar PV calculator
Solar water pumps
Battery coupled solar water pumping systems
The Power produced by the PV panels are used to charge the batteries.Therefore,The solar water pumping system can still deliver water during night or low light conditions .Ideal for water requirements for live stock.
Batteries can reduce the efficiency of the overall systems as the efficiency of the overall system is dictated by the battery and not the PV panels output.Also the overall cost of the system is increased .
Directly coupled solar water pumping systems
The solar water pumps' efficiency is almost 100 % during sunny part of the day.Since there are no battery storage, the overall cost of the solar water pumping system is less compared to directly coupled one.
Water needs to stored in overhead tanks for use during the night. Directly coupled solar water pumping systems can only be used in areas of tropical climate such as India.
Every solar water pumping solution in India is different.You may be an installer, supplier,system integrator for solar water pumps in India. Often you might get casual Inquiries about a consumer asking for a solar water pump installation for agricultural purpose or feeding a live stock etc.As a consumer may not be fully aware of what exactly his requirements are, it becomes your responsibility to gather a detailed requirements spec . The following are the basic guidelines to understand the requirements for a solar powered pump in India.This simple questionnaire will lead to a no cost proposal, which can be done over phone itself and decide upon the seriousness of the lead by giving a tentative quote.
This information is also very vital for sizing and understanding your solar power pumping system.
The Solar photovoltaic Pumping systems are an ideal alternative to diesel operated water pumps. Solar water pumps need no diesel power and very simple to install and maintain.Some solar powered pumps are hybrid, in the sense they can be powered by both solar energy and the conventional energy.
Basics of solar water pumps
For any solar water pumping system,the capacity to pump water is a function of three mail variables:
Pressure can be thought of as the work that the pump must overcome to move a certain amount of water.It is measured as feet of head or psi( pounds per sqaure inch).
Some important facts to be considered by selecting the right solar water pump are:
This factor will affect how much pressure is needed to be created in order for the water to flow. As a rule of the thumb,a pump must create 0.433 psi for every foot of elevation increase.
Other factors that affect the pressure of the solar water pump are diameter of the pipe,length,bends and restrictions such as valves.
Flow is the amount of water , that a system can move during a given time period.It is measured in gallons per minute( GPM) or hour.The relationship between the flow and pressure are that they are inversely proportional. That is, Flow will increase when the pressure decreases.
Every solar water pump can produce a range of flows and pressures.Solar pumps need certain amount of power to create a certain pressure that in turn is needed to deliver the water.This power is measured in Watts and Photovoltaic panels output are rated in watts.This power needed is an input to select the required PV panels.One point to be noted is adding more PV panels enables the solar water pumps to be usable under low light conditions.,but might not increase the flow rate of the pump even when the sunshine is at its highest radiance.
Components of a solar powered pump
A Solar Photovoltaic Pumping System consist of a
The water source can be wells,ponds,fountains etc.The water source should be able to recharge faster than a solar water pump.Care should be taken to avoid water resources lacking volume of water as there is a potential risk of the solar water pump's damage.
The pump and other electronics
There are different types of solar water pumps. They form the heart and soul of the solar water pumping system.Click here to find an FAQ on solar water pump types.
Solar water pumps provide a combination of flow and pressure so select a pump that match with your pressure and flow requirements.Solar pumps are rated according to the voltage of electricity that should be applied.They come in all ranges from 12v,24 v or 48 v.The rule of the thumb is more the power, more water can be pumped.Of course, the cost of the wiring will increase with the power of the pumps. Other accessories for the pump to function are filter,valves and switches.
Solar PV array and mounting rack
Most solar pumps require 20 % more wattage than specified when connected directly to the pump.Some wiring accessories are needed to connect the panels to the pump.There are two configurations -either directly connecting the PV array the pump and it is called direct coupling or battery coupled, where the batteries are charged from PV through charge controllers .Other components of a battery coupled solar water pumps are pump controller,pressure switch. The advantages and disadvantages of a directly coupled and battery coupled solar water pumps can be found here.
The mounting rack for the PV panels can be either fixed or tracking.Fixed solar PV mounting racks are the simplest and the cheapest.
The solar water pumps can be procured from MNRE approved manufacturers,suppliers in Bangalore,Hyderabad,Gujarat and other parts of India.
In addition, there are Chinese and other companies in the world,that sell solar water pumps to Indian market ,suitable for agriculture, home use, ponds, fountains and other applications.
To contact the solar water pump suppliers that offer different types of solar pumps to suit your application and budget, please click here.
Evaluation criteria for SPV projects in Bihar 2012
The following are the criteria for selecting a Solar photovoltaic Power developer In the state of Bihar.
1. Location of the Project.
2. Capacity in MW
3. Financial criteria
4. Technical Criteria
5. Capacity of the proposed project
6. Quantum of power offered to Bihar State Electricity Board
7. Distance of Project site from Delivery point
8. NOC from Bihar State Pollution control board
9. Evidence of clear possession of required land
Each item is evaluated and graded accordingly.
Approved solar tariff in Bihar
The approved solar PV tariff is 10.9 INR/Unit
A step by step approach to Installing solar PV systems and availing subsidy from MNRE is as given below:
First identify list of solar manufacturers/suppliers approved by MNRE by clicking on this link.
Next is to write a requirements specification for your solar power system addressing these points and place a request for quote by clicking on this link:
and obtaining the cost and technical details of proposed solar system.
List of manufacturers approved by MNRE is also available thesolarindia website. Based on the details received, the beneficiaries may identify one of the suppliers and generate proposal in association with State Nodal Agency of respective State/
Accredited Manufacturer of MNRE.
The proposals generated may then be submitted to MNRE by State Nodal Agencies / Accredited Manufacturers in the prescribed format and as per the guidelines given on MNRE website.
The proposals will be examined by a committee in MNRE with sanctions issued to all concerned.
Based on the sanction, systems will be installed at beneficiaries site and subsidy released directly to the beneficiaries after 3rd party inspection on completion of the systems with required documents submitted to Ministry.