Smart Photovoltaic Systems

It is new philosophy to generate high electricity production from large scale photovoltaic systems with low operation and maintenance cost.

Smart photovoltaic system means to use simplified design and hardware and latest technology to improve maintenance and operation of photovoltaic power plant.

This smart system can automatically discover faults in a high speed and have the ability to diagnose and rectify that faults by using a fully automated component and new technology of communication systems.

How can you implement smart photovoltaic system at your new PV plant?

This can be done by achieve some procedures at three main layer of your project as following:

First: At bottom layer: This layer contains your PV plant main component, I mean the modules as they consider the engine room of your PV system, at this layer the module strings will be equipped by a smart controller that can monitor the voltage and current of each string all over the plant so that the fault location can be precisely indicated.

Second: At intermediate layer: This layer contains PV monitoring and production management systems where an integrated computer monitoring system is deployed on unified communication platform to monitor the running status of each device of the power plant.

Third: At top layer: this layer contain centralized operation and maintenance center which manage the whole PV plant by collecting all data geographically distributed in various area and make analysis to help the operators to take decision for increasing the electricity production and reduce management cost based on the above two layers.

So smart PV system is a fully automated system which can automatically discover, diagnose and rectify faults, thereby improving the electricity yields, lowering operation and maintenance cost and increases the system revenue. 

Solar Photovoltaic Inverters Types

We know that Inverter is an essential component of nearly all types of solar photovoltaic system; it is defined as the device that converts DC electricity to AC electricity.

Now I will introduce to you all types of solar photovoltaic Inverters present at the market:

First:  Stand Alone Solar Inverter, which characterize by the following:

1-     It coverts DC electricity to AC electricity.

2-   It runs by pulling DC current from batteries charged from any DC electricity source like engine generator or wind turbine …etc.

3-   In the same time it refill batteries with DC electricity from any AC current Source when it possible.

4-   It used in feeding homes and small industrial system by AC electricity as a power backup.

In most cases as conclusion we use it in stand alone solar photovoltaic system with backup.

Second: Battery Backup Solar Inverter, which characterize by the following:

1-     It used to get AC electricity from batteries and this AC electricity will go to a selected area which needs power during outage and in the same it brings extra electricity to utility grid "feed in tariff ".

2-   It contain onboard charger to manage the batteries energy.

In most cases as conclusion we use it in stand alone solar photovoltaic system without backup.

Third: Grid Connected Solar Inverter, which characterize by the following:

1-     It used to convert DC electricity to AC electricity and it is programmed to automatically turn off during grid power outage.

2-   It allows the home owner to sell electricity to Electricity Company.

In most cases as conclusion we use it in grid connected photovoltaic system without battery backup.

Fourth: Micro Inverter, which characterize by the following:

1-     It attaches directly to individual photovoltaic modules.

2-   It is used to extracting maximum electrical power from each module.

3-   Although it is highly efficient as it produces more electrical power than on grid inverter but it is more costly.

Power Quality Analysis & Power Quality Analyzer

The purpose of electricity feeding system (electrical distribution system) is to feed the electrical loads with good and reliable electricity wave form, making them operate properly. So if the electrical load doesn't operate properly, you should suspect that there is some thing wrong in the quality of electricity feeding system.

What will you do if your electrical system fails to meet its purpose?

At this moment you should investigate the problem trying to find the causes and then you will do a corrective action, this process called Power Quality Analysis.

How can we do power quality analysis job?

First Step:

We do Electrical Measurements by an effective and specialized instrument called power quality analyzer. By using this analyzer you can observe the real time measurements for all electrical parameters and in the same time you can record all these electrical parameters at the extended analyzer memory.  This is done for a predetermined time period which may be one day or week or more or less according to load cycle.

The most typical electrical measurements which done by power quality analyzer are :  amperage, voltage, frequency, power factor, harmonics currents and voltages, crest factor, k factor, inrush current, transient currents, voltage and currents unbalance, flickers, active and reactive power and energy.

Second Step:

We connect the power quality analyzer to the computer and get all these recorded parameters in form of excel sheets and graphs.

Third Step:

We do analysis study to detect power quality problems in the electrical distribution system according to standards and regulations.

What kinds of power quality problems have been noticed?

The most infamous electrical power quality problems from our experience are one of the following:

Over voltage , Swell, Under Voltage, Sag , Voltage and Current Unbalance , Low Power Factor ,Flickers and Presence of Harmonics Voltage and Currents.

What are success keys in doing power quality analysis study?

The four successes keys in doing power quality measurements and analysis study are the following:

One: Good selection of measured points by reviewing single line diagram and setting the goal and plan before connecting power quality analyzer to the electrical networks and loads.

Two:  Good knowledge of your power quality analyzer functions and features and how to use it to capture the needed electrical parameters.  

Three: To be conscious of what you search for in the electrical data after it is downloaded at your computer, also to be conscious of the meaning of the increase or decrease of electrical parameters during the measured period and to think, why does this happened and what does its side effect ?

Four: To have a good learning and knowledge about power quality problems and how to solve it and the international standards that governs the deviation of the electrical parameters from the normal values. Like for example IEEE 519-1992 standard which govern harmonics deviation.

Fortunately, I have an effective and amazing power quality analyzer and I can help our colleague and customers in doing such power quality analysis job and also I welcome every one have any question or inquiry …  

Solar Photovoltaic Cables

One of the most important components in your electrical solar photovoltaic plant is wiring and cables, in order to generate reliable electricity.

Solar cables interconnect solar panels and other photovoltaic system component. They are designed to be ultraviolet and weather resistance as they are always laid outside, so single core cables with max DC voltage of 1.8 kv and of temperature rang from 40° c to 90° c are usually used for DC side and three core cables or five core cables are used at AC side in case of single or three phase inverter respectively.

The Question is what solar cable features are, we should care about?

The First feature is the insulation: as the insulation must withstand mechanical and thermal stresses so usually cross linked plastic using electron beam are used as the insulation and jacket materials are resistance to weather conditions and the jacket is always halogen free flame retardant.

The second feature is Dc connection: as we know that we use individual cables (2 cables) to connect modules to form strings and then strings leads to junction box. Here in order to avoid ground fault and short circuit, the positive and negative cables should be laid separately.

The third feature is how to minimize cable losses: this can be done by choosing the right cable cross section area in the condition that losses shouldn't be more that 1 %.Usually we have string cross section area of 4 to 8 square millimeters.

The fourth feature is the standard: meaning that solar cable should be manufactured according to standards like UL4703 standard which applies for solar cable in North America.

One of the most important ways in order to assure that solar cable is good and suitable to various operating condition , you should assure that your cable have  TUV Rheinland Test Certificate which mean that the solar cable specification meet several international standard.

So in order to generate reliable electricity from solar photovoltaic plant you should care about the selection of solar photovoltaic cables and wiring.

Solar Photovoltaic Cells Types & Properties

All of us know that solar photovoltaic cell is a device that converts solar energy to electricity. Also we know that solar cells are integrated together to produce the module and modules are integrated together to produce panels and at the end panels are integrated together to produce the array which represents the final shape of the solar photovoltaic plant that generate electricity to you.

Solar cell is the essential unit of solar photovoltaic system, so you should care about its type and characteristics. The question is If you go around the market, what kind of solar cell you find and what is the pros and cons of each type, let us simply know the answer.

At the market you will find two popular types of solar photovoltaic cell:

Type one: Silicon Wafer also called crystalline silicon cells which represent nearly 93 % of the solar photovoltaic cells present in the market; it is the most famous type. This type is actually categorized into mono crystalline type and poly crystalline type.

Type two: Thin Film which represents nearly 7 % of the solar photovoltaic cells present in the market, this type categorized into amorphous silicon cells (4.2%), cadmium telluride (Cd Te 1 %) cells and copper indium compound cells (CIS 0.7 %).

Now let us now the differences between the main three types:  mono crystalline silicon, poly crystalline silicon and thin film (amorphous):

comparison	Mono crystalline	Poly crystalline	Thin film(amorphous):
Size ratio	Up to 170 w/m2	Up to 150 w/m2	Up to 80 w/m2
Efficiency	Up to 19%	Up to 18%	Up to 10%
life	Long (25 years)	Long (25 years)	short (10 years)
Performance In bad weather	Outstanding performance in cooler weather	Slightly better performance in hotter weather	Outstanding performance in hotter weather and less effective in cooler weather
Common use & Cost	Most commonly used	Less expensive that mono	Cheaper than mono & poly.

The selection of solar photovoltaic cell type is a key actor you should care about when you construct anew solar photovoltaic plant to generate electricity. You should select the most propitiate type according to your load wattage, solar photovoltaic system cost and the environmental condition.  

Design On grid Solar Photovoltaic at your home to Generate Electricity

Question, can we generate electricity locally at our homes and sell it to the electricity company? Is this is a good investment project I can do? The answer is yes off course you can do it….. That is done by construction on grid photo voltaic system at the roof of your home.

Most of people that construct on grid photo voltaic system aiming from that are to gain good monthly income from the electricity company under the popular regulation present in almost countries all over the world which called Feed in Tariff. There are two factors affecting your success in installing excellent and reliable on grid photo voltaic system to generate electricity and harvest good monthly income one of them is the good design and the other is the good selection of on grid photo voltaic system components to be according to specification.    

Kindly let me tell you a brief on how can the specialized solar photo voltaic engineers design on grid photo voltaic system in a simple way :

First: we will ask home owner about electricity bills for the previous 2 years to indicate the average monthly electricity consumption and also ask him about his budget.  

Second: we start to go to the roof area to indicate its characteristics by identifying the usable area that is suitable for installing the photovoltaic system (eliminating spaces of local and horizontal shadow) and indicting the roof azimuth and tilt angle which related to the good facing to the sun to get maximum electricity harvest.

Third: we select a photo voltaic modules type and manufacture from many various manufacturers present all over the world and racking system if needed. By knowing the size of module and racking system I will indicate the maximum number of modules I can installing at the roof and consequently the maximum electrical power I can gain from the array.

Fourth: by indicating the array max electrical power we can get the rated power of the inverter we will install.

 Fifth: by using software or by some calculation we indicate number of array strings and maximum /minimum number of modules in each string.

Sixth: by knowing the sun hours in the city and in my specific roof under design I can calculate the electricity that can be harvested each month then I will do my feasibility study introducing it to the home owner.

It's an effective and guaranteed project to generate electricity and sell it to Electricity Company by constructing on grid photo voltaic system … I am in help to my colleagues , any home owner or anew electrical engineer . all of your inquires are welcome …..