Photovoltaic Systems

This study seeks to have an in-depth insight of the PV system. The below is a picture that gives a sneak preview of the house model that utilizes the PV technology as its main source of energy. This technology comes in as the primary source of energy to most of the houses within the tropics and the power from the national grid comes as secondary options which mean they only kick-in when the PV cannot generate power or is faulty. This saves on the expenditure on encouraging the green environment. It is a clean source of energy.

The typical house utilizes the PV:

• A PV system utilizes solar panels to capture the solar energy and converts into an electrical form
• The inverter which comes in between the appliances and the solar, converts the direct current from the solar to an alternating current that can then be used by the electronics
• Grid system power comes in as the other option when the PV system fails.

Photovoltaic (PV) technology is still pretty new in the market and the innovation is still being conducted in depth. PV has been used to power homes for decades of years now and with good reason. It is one of the renewable energy systems and it utilizes the PV modules to harness the sunlight energy and convert it to the electricity that can then be used in powering the electrical components and appliances. The below is a snippet of a PV system;

It is a widely used form of technology especially in tropical countries such as Africa and Australia. Sufficient sunlight falls on the tropical countries surfaces to supply the required total energy needs many times over. By installing solar modules (or panels), the homeowner is able to capture some of this abundant energy.

In essence it is a form of renewable energy source since it can be harnessed in solar panel and stored on batteries

Types of PV panels

The PV technology is evolving almost every day. Developed countries like Germany, China, and the USA are constantly improving their PV solar systems to keep abreast on the market. Though not so much advancement has been noticed, at least it has gotten better, as improvements in quality, efficiency, and versatility continue to develop.

The main types of PV that are currently on sale include:

The monocrystalline panel can be assumed as the original product that was realized through the PV technology. As much as that holds to be true, new technologies have emerged and hence challenging monocrystalline by a versatile facet of technology on factors likes efficiency and price.

The variety of solar power technologies available runs on a scale of key essential factors and measures such as:

• Efficiency: this is the ability of the PV system to produce power in a consistent manner that is regarded as reliable and always available to drive the appliances that are connected to it.
• Price: The price or cost of the materials that makes up the PV system should be moderated. The price of the system should also be within the market price in regards the economy and the affordability.
• Durability: the system or the product should be durable enough.
• Flexibility: the system should be flexible in that it should allow the additional appliances to be connected to it. Again, the system should allow room for future expansion and to be improved.

The above consideration varies from one client to another and also depending upon the need of the client's project.

How PV System works

Silicon is a major component of a PV solar technology. Silicon component generates generate an electrical current when they absorb sunlight, which translates to the electrical power output in the PV. The process of generating electrical current by the silicon is known as the photovoltaic effect. The maximum voltage that can be generated by the PV depends on the purity of the silicon component that has been used. This is because silicon is a semiconductor and these substances need purified silicon to get the best efficiency. The process therefore that is behind the PV technology is researching is the crystalline silicon purification process.

The below are the main PV technologies of PV panels that are in the market:

Polycrystalline Silicon Solar PV

Polycrystalline solar manufacturing or production process is realized through the pouring of molten silicon into a cast. These construction methods lead to the formation of an imperfect crystal structure creating boundaries where the crystal formation breaks. The content of impurities in the silicon is high.

Advantages

It is less costly compared with monocrystalline since the production process uses less materials and lesser energy

Disadvantages

It is less efficient due to the impurities on the silicon when compared to the monocrystalline

Monocrystalline Silicon Solar PV

Monocrystalline PV solar is realized through the growing of a single crystal. The crystal formation in a monocrystalline is even giving it the best purity which translates to the highest efficiency levels.

Advantages

It is the best PV technology to deliver efficiency. This is achieved in the amount of energy out in regards the panel size

Disadvantages

It is costly

Thin-Film Solar PV

This PV type of technology has the lowest market share. Its constructed process includes a variety of materials, with the main options being amorphous silicon.

Advantages

• It is the best for projects that use less power.
• It is light weight and therefore is portable
• Has the best efficiency
• Is expected to be less expensive

Disadvantages

Cannot be used by high power intensive projects

Typical System Components:

• PV Array: This is made up of PV modules. The PV modules convert the solar energy to electricity, a form that can be used by the appliances.
• Balance of system equipment (BOS): This includes all the mounting systems and wiring components used in the integration process to realize the structural and electrical systems of the home.
• Dc-Ac inverter: In essence, the PV array generates power in dc form. The dc-ac converter comes in to assist in the conversion of the generated dc power to standard ac Power used by the house appliances.
• Metering: this measures the amount of power underutilization and an indication of system performance
• Other components: utility switch (depending on local utility)

Battery and the battery enclosures

Battery charge controller

And the sub-panel that is separated but is crucial in regards the critical load circuits

PV System Design

Basic Principles

The below are the basic and the main principles that should be followed when designing a PV system

• The system or the package under development should have the customers’ needs on the frontline. Issues like the cost and the amount of power required by the client should be some of the major factors that should be considered.
• The rooftop or the installation platform should be large enough to accommodate the size of the panel.
• Any outdoor equipment should be solar and waterproof to avoid damage during the rainy season.
• The installation point should be away from tall buildings or trees to avoid blockage of the sunrays.
• The design should comply with all the electrical codes and the design principles
• The design should be in a position to handle the battery just in case it is required.

PV System Installation

Basic installation principles

• 1.The roof or the support structure that the PV system is mounted on should be in a position to accommodate the extra weight of the PV.
• 2. Ensure the roof area or other installation site is capable of handling the desired system size.
• 3. Follow the PV manufacturer's installation manual and refer where possible
• 4. The system parts that make up the PV system should be grounded correctly to avoid such hazards like the electrical shocks from happening

Sizing of the PV

Determine the size of power that is required: the first stage of determining the size of the PV system is carrying out an energy audit of all the appliances that are currently or are required to be powered. The main areas that are but into consideration are;

The calculation of the total daily power consumption of each appliance that needs to be powered.

Calculate the total amount of power in watts that the PV system modules will be using per day. Sizing the PV components and models: in essence, different sizes of the modules produce or generate different amounts of energy or power. The watt amount or the peak watt produced varies from one location to the other. To calculate determine the size above, the following are put into considerations;

The calculation of the total number of PV panels that the system will contain.

Then calculate the total watt peak or watt rating that the module will demand.

The result of the above calculation is regarded as the lowest number of the PV Panels. If the system is improved by increasing the number of the PV modules, the efficiency and the power generation of the system is enhanced. The process also will boost the operation and the life of the battery. The opposite holds to be true as well, that using a fewer number of PV modules will shorten the life of the battery and the system will not work or will not generate energy during cloudy seasons.

The sizing of the battery: the manufacturers of the PV systems have always recommended that the users use the deep cycle battery in these systems. The key reason behind this recommendation is that the battery is capable of charging and discharging day in day out for years without getting spoiled. Again, the size and the amount of power generated by the battery should be enough to supply power to all the appliances both during the night and even in cloudy days. The size of the battery is determined by using the below methods;

• Calculate the total amount of energy that is consumed by all appliances in watts on a daily basis
• Calculate the total power remaining by factoring in a 0.85% power loss that is lost by the battery
• Divide the result by 0.6 which is considered as the depth of discharge value
• Divide the result further by dividing by a factor of nominal battery voltage
• Multiply the result by the number of days that the system is expected to run the appliances when there is no power being generated by the PV system

The resizing of the inverter: the main function or the role of the inverter is to convert the generated DC current to an AC output that can then be used by the AC appliances. A measure should be taken into account when purchasing an inverter, in that, the total amount of energy used by the appliances in watts should be less than the power rating of the inverter. Again, the battery and the inverter must have the same nominal voltage.

The sizing of the solar controller charge: The rating mark on the controller charge is actually calibrated against the voltage capacities and the Amperage. The selection process should also be taken into account so that the charge controller chosen should be in harmony with the rest of the modules of the system. The below is a simple equation that can be used when choosing the charge controller to be used;

CASE STUDY (Test Prototype sample scenario)

A house in a given area named A has the below appliances and their power usage;

One 18 watt Television screen that is used for 4 hours on a daily basis

One 60 watt energy saving lights bulb that is used for 2 hours on a daily basis

And the presence of a one 75 watt refrigerator that runs for almost 12 hours per day.

The system or the PV system that is in control is calibrated as 110wp and 12 Vdc PV modules.

Use the above to calculate the amount of the power that is demanded

The size of the PV panel that is required to run the system

The inverter size that will be required to control the current of the system

The size of the battery that will be in a position to control the appliances when the need arises or in such a situation as the cloudy days or during the night.

The size of the solar controller that will be interfaced with the system.

Cost analysis

The cost of the development of the PV system includes the below;

Direct costs: this includes the cost of purchasing the solar panel, inverters, and batteries

Indirect Costs: this includes the cost of raising the floor or the roof to support the solar panel

Labour costs: this includes the hiring expenses to do the work

Installation costs: this is a subscription fee for the connection process

Conclusion and Recommendation

PV is a renewable source of energy. It is clean compared to other sources of energy like the hydro power. It is readily available especially within the tropical countries. Although the installation process of the above system is costly, the expenses reduce after the installation process. The expenses that might be incurred going forward may be the one for maintenance.