DAY 24: CHARGE CONTROLLERS ( PWM and MPPT)

PWM (Pulse width controller) charge Controller

    This type of charge controller charges the batteries by sending out short pulses of current to the batteries, hence the name.

    It monitors the battery state and varies the nature of the pulse it sends accordingly, during the bulk stage when the battery is low, it sends long and continuous pulses and it sends it out rapidly. It monitors the battery and as the battery starts getting fully charged, the frequency of the pulse decreases, It doesn’t send it as rapidly as before anymore and the pulses become shorter and shorter, this is done so that the battery is not overcharged.

   

 




  PLEASE NOTE. For a PV module to charge your batteries, the voltage of the PV module must be higher than that of the batteries,

Advantages

.1) Cost

      PWM charge controller is cheaper than the MPPT charge controller, it is easily affordable. It can be used for small scale solar projects.

Disadvantages

.1) Efficiency

      It is not as efficient as the MPPT charge controller.

.2) Small scale projects

    It can’t be used for large scale projects 60amps and above.

.3) Voltage conversion

    It can’t convert the excess voltage to current.

    

MPPT (Maximum Power Point tracking) charge controller

 This is actually a much more recent type of charge controller. The MPPT charges the battery by sending out the maximum power possible to the battery hence the name. It monitors your PV module and your battery and determines the most appropriate power to send.

One of its most distinguishing features is its ability to convert excess voltage from the panel to current for your systems.

Advantages

.1)  Efficiency

It has a higher efficiency compared to the PWM.

.2) Voltage conversion

It converts excess voltage to current for the system.

.3) Large scale projects

It can be used for large scale projects

Disadvantages                                                                         

.1) Cost

It has a higher cost compared to PWM.

DAY 23: CHARGER CONTROLLERS (The charging stages)

Day 23 of #100daysofsolarnuggets

As mentioned earlier there are two types of charge controllers

.1) Pulse width modulator (PWM) charge controller

.2) Maximum power point tracking (MPPT) charge controller

Before we look at the two types of charge controller I want to discuss briefly the charging process that occurs between the charge controller and the batteries.

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There are three basic stages in the charging of a battery.

.1) BULK STAGE

This stage accounts for the major part of the charging process. This is the first stage of the charging process, the battery is charged with the maximum current possible and the aim of this process is to push as much power as possible into the batteries to get them filled up.

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.2) ABSORPTION STAGE

This stage occurs when the battery is getting filled up, the charge controller reduces the amount current sent to the battery, this allows the charge controller efficiently monitor the charging process to prevent over charging.

 This stage is important in the charging process because if the charge controller continues charging the batteries at bulk stage till the end of the charging process, it may *mistakenly overcharge the battery.

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.3) FLOAT STAGE

This stage begins when the battery is almost completely fully charged, at this point the charge controller sends what we call trickle charges to the batteries. This trickle charge is most times equal  to the rate of self-discharge of the battery.

In other words, during this process the charge controller is simply topping  up the battery, getting to 100%. This is  to compensate for the loss that  happens due to the internal reaction of the batteries(self-discharge).The charge controller does this by sending very little charges now and then to the battery.

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Picture this

The Charging process can be viewed as this,

Imagine Someone driving a car(B) a distance away and approaching a traffic congestion ahead.

When he is still far away, he can drive at the maximum speed possible (BULK STAGE) until he gets closer to the traffic congestion, as he gets to the traffic congestion he begins to slow down (ABSORPTION STAGE) so that he would not mistakenly hit the car(A) that's in front of  him. Once he gets close to the car(A) he stops.The traffic congestion eases a little, so the car(A) ahead slowly moves and then stops again, and the driver of car(B) also follows it moving slowly(trickle charge) to cover the gap created between him and the car(A)(FLOAT STAGE).

Though the PWM and the MPPT charge controllers use different techniques to charge the batteries, they still follow this three stages when charging batterieS.

DAY 22: CHARGE CONTROLLERS

 

Day 22 of #100daysofsolarnuggets

What is a charge controller?

     A charge controller is a device that controls the charging of the batteries in the battery bank. It is placed between the battery and the solar panel. The main purpose of a charge controller is to prevent the batteries from getting overcharged. It regulates the current flowing in and out of the batter,this is done to ensure your batteries last long and more importantly this is done for users safety.Charge controllers come in different shapes sizes and color.

Features of a charge controller

Below are some of the feature of a charge controller, some charge controllers have more features than the other.

.1) Prevents the battery from overcharging.

This is the main function of a charge controller, batteries are very sensitive components, so care must be taken not to overcharge them. The charge controller regulates the voltage and current coming into the battery.

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.2) Blocking reverse current.

At night when the solar panels are not producing anything, the battery has a higher voltage than the panels because of this higher voltage, current from the battery would try to find its way back to the solar panels and if this is allowed,it could damage our solar panels. The charge controller prevents current from flowing from the battery to the solar panel. (newer models of solar panels also come with  a way of blocking reverse current in built as a precaution)

.3) To prevent deep discharging.

Discharging your battery below 50%  significantly reduces the lifespan of your batteries, the charge controller monitors battery usage and alerts  you, when your battery is about to be discharged  below the recommended level.

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.4) data logging

Some charge controllers record the values from your solar systems such as the maximum power generated from your solar panels, current , voltage, battery levels and the likes, this is done on a daily basis and it stores this data in the memory of the charge  controller .This helps you to monitor your solar system and detect any fault that may arise early enough. It also enables you to have a record and keep track of the performance of your system.

There are two types of charge controllers

.1) PWM (Pulse Width Modulation)

.2) MPPT (Maximum Power Point Tracking)

If you enjoyed this article,please like share or you could ask me any question.

DAY 21: SOLAR FARMS,THE QUEST FOR CLEAN ENERGY.

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    There is an interesting trend playing out in the global scene that I believe more people should be aware of. A lot of countries in the drive to create clean energy are investing massively in solar farms (photovoltaic power stations)

What are solar farms?

     A Solar farm is a large expanse of land that has a lot of solar panels installed together to generate electricity at a very large scale which is now fed back into the grid.Solar farms are also known as Photovolatic power stations. The capacities of this solar farms vary. There are solar farms that generate between 10 to 50 MW and there are those that generate as much as 500 MW and above.   #100DaysofSolarnuggets

   Currently the largest solar plant in the world is Longyangxia Dam Solar park in China, this has the capacity to generate a whooping 850MW. There are a lot of solar farms In the world we have kamuthi solar power project in India that has the capacity of 648MW,Solar star 1 and Solar star 2 both  located in the United states and each of them having a capacity of 597MW each.

   There are still many more solar farms in the world, as at writing this article the largest solar power plant is Longyangxia dam solar park but there is no guarantee that in next one or two years it would still be largest, lots of countries in their quest to cut down their carbon emissions and reduce their over dependence on fossil fuels are undertaking some ambitious solar farms project. As I write this article the Quaid-e-Azam Solar Power Park (QASP) in Pakistan is on a quest to becoming the largest solar farm in the world with an estimated capacity of up to 1000MW once completed, it aims to generate as much as 1.271bn KWh of energy annually. There are a lot more similar project being conceived by others.    #100DaysofSolarnuggets

 To give you an idea of how large this kind of project is the Longyangxia dam solar park in China has the capacity to power approximately 200,000 homes.

What are the limitations?

.1) Cost

Solar farms are cost intensive, costing quite a lot of money to create. To successfully build a solar farm you would need a lot of materials Solar panels, Inverters, transmission lines and a lot of other things.

A lot of solar panels are needed sometimes to generate about 100MW you would need somewhere between 300,000 to 400,000 panels. The largest solar farm has close to 4million panels, Inverters are needed to convert the DC current to AC current.

.2) Regular cleaning.

 Solar panels must be cleaned regularly especially during dusty periods, dirt accumulating on the solar panels significantly reduce the efficiency of the panels.This is a lot of work because a lot of panels are involved.

.3) Sun tracking vs fixed panels.

To efficiently utilize the intensity of the sun Solar panels should be facing the sun always, Solar trackers when installed alongside our solar panels help it track the movement of the sun at all times (from sun rise to sun set), a lot of solar farms have fixed solar panels placed at the optimum position to get solar light. Installing solar trackers comes at additional costs.

.4) Night.

As we all know solar energy can only be generated in the presence of sunlight, which means in the Night time nothing would be generated.

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To be continued.