DAY: 25 INVERTERS ; THE INTRODUCTION.

Day 25 of #100daysofsolarnuggets

Inverter

Over the course of the program, we’ve discussed on the basic components of a solar system, we have talked about Solar panels, batteries, and charge controllers. 

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Today we would be introducing Inverters.

   Inverters are like the brains of the solar energy system. Their main function is to take D.C. current from the Solar panels or the batteries and convert them to AC current that can be used by our appliance, this is to say that we can’t use our solar system without an Inverter.

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  Things to note.

1.       Inverter does not supply Electric Energy (Power) on it’s own, it merely converts from one form to another (From D.C. to A.C.). The Inverter must be connected to an energy source (Battery) for it to function. If it is not connected to a battery bank it simply cannot be used.

2.       There are inverters and there are Inverter/chargers.

i.                     Inverters: All they can do is to convert D.C. energy from the batteries to A.C. Energy that can be used by our appliances and devices, they do not have inbuilt charges in them to charge the battery bank from an A.C power source.

ii.                   Inverters/charges: They convert D.C. Energy from the batteries to A.C. Energy that can be used by our appliances and devices, they also come with in-built chargers. The chargers enable them to charge the batteries from an A.C. power source (Utility power supply or maybe Generators).

   Inverter/chargers are particularly very useful for solar systems that are also connected to the grid. What this means is that you have the option of charging your batteries with your solar panels and you also have the option of charging your panels with either the utility or your generators.

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3.      Inverter ratings

Inverters are rated in this format 1.5kw 12V, 2.5kw 24V , 6kw 24V,48v and so on

Let me explain in terms of power and voltage..

i.                     Power(Kw)

1.5kw 12V. This means that the maximum power that your system can take is 1.5kw (Please note 1.5Kw is equal to 1500 watts, 1kw =1000watts; kw=Kilo watts).If your system supplies a higher power than yourIinverter capacity, let’s assume 2kw, not only would the extra 500watts of energy be wasted, the higher power could damage your inverter if care is not taken.

ii.                   Voltage(V)

2.5KW 24V.This mean your Inverter works with a 24 Volt system. The voltage rating of the Inverter you buy is depended on the system voltage of your solar system. It is very important that you do not purchase an Inverter with a different voltage rating from your system.

You determine your system voltage from the voltage of your batteries and Solar panels in your solar system.

Some modern Inverters can work with two or more voltage systems for example 7KW 24V, 48V

Now there are three different types of Inverters used in solar installation..

(To be continued).

IMPORTANT NOTICE

This is day 25 and we are through with the first quarter of our online solar class, It has been an interesting journey so far as we have covered the basic of solar energy systems and a few other things.

 Solar Nuggets would be going on a 3 days break, this is to enable everyone that has followed me so far properly revise and understand what we have learnt so far.

 We would resume officially on Tuesday morning as we continue in the second quarter of the online solar class.

Feel free to ask questions concerning any area you do not understand, I would be available to answer any of your questions.

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.