DESIGN, CONSTRUCTION AND INSTALLATION OF 5KVA SOLAR SYSTEM

DESIGN, CONSTRUCTION AND INSTALLATION OF 5KVA SOLAR SYSTEM

CHAPTER ONE

1.0       INTRODUCTION

In recent times there has been an increasing demand for alternative energy sources as global oil reserves dwindle and concerns for the environment continue to grow.Today, just about everyone increasingly depends on devices that require electricity,but in Nigeria, one of the most populated nations in Africa, only 40% of the people are connected to the energy grid; those connected experience brownouts and total blackouts around 60% of the time. Meanwhile, it is sunny 43% of daylight hours in Nigeria, which is an average of 1885 hours of sunlight per year, this means solar as an alternative energy solution is very much feasible in this part of the world.

There is therefore a growing need for inverters to convert low voltage DC to high voltage AC which are of lower cost and more efficient.This project focuses on DC to AC power inverter whose aim is to efficiently convert a DC power source to a high voltage AC source, similar to power that would be available at an electrical wall outlet.Inverters are used for many applications as in a situation where low voltage DC sources such as batteries, solar panels or fuel cells must be converted so that devices can run on AC power. One example of such a situation would be converting electrical power from a car battery to run a laptop, television, lighting or cell phone etc.

The method in which the low voltage DC power is inverted, is completed in two steps. The first being the conversion of the low voltage DC power to a high voltage DC source, and the second step being the conversion of the high DC source to an AC waveform using pulse width modulation. Another method to complete the desired outcome would be to first convert the low voltage DC power to AC, and then use a transformer to boost the voltage to 220 volts. This project focused on the design, construction and implementation of 5KVA Solar system which specifically the transformed a high voltage DC source from the sun into an AC output.

1.1       BACKGROUND INFORMATION

Beginning from the late 19th century to the middle of the 20th century DC to AC power conversion was accomplished using rotary converters, or Motor Generator(MG) sets. In the early 20th century, vacuum tube and gas filled tube began to be used as switches in inverter circuits. The most widely used type of tube was the thyraton.

The origination of electromechanical inverters explains the source of the term inverter. Early AC to DC converters used on conduction or synchronous AC motor are directly connected to a generator (dynamo), so that the generators commutation reversed its connection exactly the right moments to produce DC. A later improvement is the synchronous converter, in which the motor and generator windings are combined into one armature, with slip-rings at one end and a commutation at the other end and only one field frame.

The result is either with AC-on, DC-out. With an M.G sets, the DC can be considered to be separately generated from the AC with a synchronous converter,in a certain sense, it can be considered to be mechanically rectified AC. Using the right auxiliary and control equipment, an M.G set or rotary converter can “run backward”, converting DC to AC. Hence, an inverter is inverter converter.It should also be noted that early inverter did not use transistors for switching purposes, because its voltage and current ratings were not high enough for most inverter applications. However, in 1975, the Silicon Control Rectifier (SCR) was introduced as switches, hence initiating a transition to solid state inverter circuits.Today, however due to an increased knowledge in technology, modern inverters are less bulky, and more efficient with the use of various components such as ICs (Integrated Circuits).

1.2       PROBLEM STATEMENT

Lack of incentives to invest in the aged and inefficient national grid, transmission and distribution infrastructures, as well as the fact that energy from decentralized,renewable sources is not well fashioned to work on the electricity grids in the country has led to incessant power outage all over the country. Some of the solutions to this problem is an auxiliary AC power generator, nuclear power plants,wind turbines, solar power etc., but the cost of fossil fuels continues to increase rapidly and hence will not be cost effective in the future; while solar power has some aesthetic, economic and technical drawbacks. A more effective and reliable alternative is battery power back-up system which can be converted to AC power using power inverters.

1.3       OBJECTIVES

The main aim of this project is to design, construct and install a 5kVA solar system inverter with48volts supply so as to achieve the following objectives:

1. To produce pure sine wave output voltage that can be used to power Electrical/Electronic Department.
2. To back-up the erratic power supply by PHCN.

1.4       SIGNIFICANCE OF THE STUDY

The important of an inverter is that, it has the capability to convert the DC power into AC power making it useful to operate equipment such as household items,computers, power tools and much more, by simply plugging typical equipment into the inverter.

It is also important because it can deliver efficient power to run an electrical product with high power requirement usually as electric utility heater, air conditioners with additional batteries connected because of it high current it will draw.

1.5       JUSTIFICATION

Designing a pure sine wave inverter with the above listed features is of great significance for it serves to unveil the challenges and possible flaws that are associated with modern inverters in the market and hence give insight and practical design experience to students which will in turn encourage more researches in the area of solar inverter power system as an alternative power supply for homes and industries.

This project also serves to widen the horizon of students especially in the area of modern day solar technology and hence can serve as an area for further research and development in schools and industries.Solar power inverter systems find application in the following areas of life:

• In homes and offices as stand-alone power supply or supplement to the mains power supply
• In industries and factories as grid-tie or stand-alone system
• In camping grounds and off grid locations as a portable power supply
• In hospitals as back-up power supply in case of mains outage
• In other power critical places as emergency power supply, etc.
• In our case, it serves to provide an alternative power source for the department during the times of mains power outage.

1.6       SCOPE OF WORK

This project work covers the design and installation of a 5kVA solar inverter that can power the loads that are within its capacity. The design’s focus will be in designing an inverter that will power the department’s first floor and be dependent on power from the mains or solar cells. The battery bank is limited to 19,200 Watt-Hour (i.e. 48V x 400Ah) and can be charged by either the mains power or the power from the array of solar modules. The design is capable of automatically switching to mains or inverter mode when appropriate and features all forms of protection techniques/schemes to guard the system and the connected appliances against any form of danger that may arise during operation.

The design does not accommodate a high power surge beyond its stated capacity and hence cannot be used to power high inductive loads like industrial electric motors and high power air conditioners. It can be used to power very sensitive and life dependent devices/equipment like medical equipment and servers because of the near absence of harmonic content in the final power output of the design.