15-01-2013, 01:01 PM
DESIGN AND SIMULATION OF PHOTOVOLTAIC WATER PUMPING SYSTEM
DESIGN AND SIMULATION.pdf (Size: 1.43 MB / Downloads: 158)
ABSTRACT
This thesis deals with the design and simulation of a simple but efficient photovoltaic
water pumping system. It provides theoretical studies of photovoltaics and modeling
techniques using equivalent electric circuits. The system employs the maximum power point
tracker (MPPT). The investigation includes discussion of various MPPT algorithms and
control methods. PSpice simulations verify the DC-DC converter design. MATLAB
simulations perform comparative tests of two popular MPPT algorithms using actual
irradiance data. The thesis decides on the output sensing direct control method because it
requires fewer sensors. This allows a lower cost system. Each subsystem is modeled in
order to simulate the whole system in MATLAB. It employs SIMULINK to model a DC
pump motor, and the model is transferred into MATLAB. Then, MATLAB simulations
verify the system and functionality of MPPT. Simulations also make comparisons with the
system without MPPT in terms of total energy produced and total volume of water pumped
per day. The results validate that MPPT can significantly increase the efficiency and the
performance of PV water pumping system compared to the system without MPPT.
Introduction
Water resources are essential for satisfying human needs, protecting health, and
ensuring food production, energy and the restoration of ecosystems, as well as for social and
economic development and for sustainable development [25]. However, according to UN
World Water Development Report in 2003, it has been estimated that two billion people are
affected by water shortages in over forty countries, and 1.1 billion do not have sufficient
drinking water [26]. There is a great and urgent need to supply environmentally sound
technology for the provision of drinking water. Remote water pumping systems are a key
component in meeting this need. It will also be the first stage of the purification and
desalination plants to produce potable water.
In this thesis, a simple but efficient photovoltaic water pumping system is presented.
It provides theoretical studies of photovoltaics (PV) and its modeling techniques. It also
investigates in detail the maximum power point tracker (MPPT), a power electronic device
that significantly increases the system efficiency. At last, it presents MATLAB simulations
of the system and makes comparisons with a system without MPPT.
Water Pumping Systems and Photovoltaic Power
A water pumping system needs a source of power to operate. In general, AC
powered system is economic and takes minimum maintenance when AC power is available
from the nearby power grid. However, in many rural areas, water sources are spread over
many miles of land and power lines are scarce. Installation of a new transmission line and a
transformer to the location is often prohibitively expensive. Windmills have been installed traditionally in such areas; many of them are, however, inoperative now due to lack of proper
maintenance and age. Today, many stand-alone type water pumping systems use internal
combustion engines. These systems are portable and easy to install. However, they have
some major disadvantages, such as: they require frequent site visits for refueling and
maintenance, and furthermore diesel fuel is often expensive and not readily available in rural
areas of many developing countries.
Energy Storage Alternatives
Needless to say, photovoltaics are able to produce electricity only when the sunlight
is available, therefore stand-alone systems obviously need some sort of backup energy
storage which makes them available through the night or bad weather conditions.
Among many possible storage technologies, the lead-acid battery continues to be the
workhorse of many PV systems because it is relatively inexpensive and widely available. In
addition to energy storage, the battery also has ability to provide surges of current that are
much higher than the instantaneous current available from the array, as well as the inherent and automatic property controlling the output voltage of the array so that loads receive
voltages within their own range of acceptability [16].
Concluding Remarks
Issues of energy and global warming are some of the biggest challenges for humanity
in the 21st century. Energy is so important for everyone, and in fact, taking control of the
world’s supply of oil is one of the most important national agenda for United Sates. The
world is getting divided into two groups: the countries that have access to oil and natural gas
resources and those that do not. In contrast, renewable energy resources are ubiquitous
around the world. Especially, PV has a powerful attraction because it produces electric
energy from a free inexhaustible source, the sun, using no moving parts, consuming no fossil
fuels, and creating no pollution or green house gases during the power generation. Together
with decreasing PV module costs and increasing efficiency, PV is getting more pervasive
than ever.