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As human population are rapidly increase, the demand for energy resources and electricity supply are more and more high. There are two types of energy which is fossil-based energy and green energy .
Traditionally, fossil fuels like coal, natural gas and petroleum are mainly use to generate electric power. In year 2007, coal contributes the most share of world electricity generation which is approximate 42% and it is believed that its share will remain unchanged through year 2035 . As is known, fossil fuels are finite resources. The World Energy Forum has warned that fossil fuels will be exhausted in less than 10 decades . Besides, fossil fuels will caused major human health problems and negative impacts to our environment such as green house effect and pollution. Therefore, the use of renewable and greener energy is now the main direction of many countries.
Green energy is energy power that is fundamentally environment friendly for example tidal power, wave power, solar power and wind power. Nowadays, wind energy is one of the most widely used green sources of energy . Wind energy is a very clean energy which does not discharge any C02 in the process of generating electricity. Total wind turbines which been installed around the world are generating 340 TWh per year, which is about 2% of total electricity usage . However, the performance of wind resource are varies with different location.
Among all the green energy, solar energy is the most reliable source of clean, sustainable energy and it has the largest potential of any power source to solve the worldâ€™s energy problems . Around the world, there are about 1700 TW of solar power are available for photovoltaic (PV) which is the technology for solar electricity devices . Solar cell technology are being use to convert solar energy to electricity which is capable for normal application in home or vehicle.
Hybrid energy systems combine two or more energy conversion devices and overcome the limitation of each device. Hybrid systems offer higher efficiency and reliability compare to a single type of energy conversion device.
The efficiency and reliability of wind and solar energy in generating electricity are being question by many researches. The performance of wind power is varies at different location and seasons. When there is no wind blowing, no electricity is produced. Thus, wind power cannot be used as a reliable source of base load power.
Solar energyâ€™s largest limitation is its sporadic availability. Nightfall and clouds will interrupt the collection of solar energy. Thus, solar energy does not always provide the level of power enough to fulfil energy needs of cities.
In this project, a small scale hybrid power system is being design and the performance of this prototype will be evaluated. This hybrid power system combines solar energy and wind energy to generate electricity. Ideally, this hybrid power system will have better performance than a single type of energy conversion device.
Application and Scenarios
Hybrid power systems are being implemented in rural areas of Malaysia. Why hybrid system? Itâ€™s because rural areas like islands or mountain areas are far away from national grid and it need a very high cost to connect them. Besides, diesel generator engine may face higher failure and requires unscheduled site visits or permanent man power for servicing. Thus, hybrid systems are the better choice in generating electricity.
Objectives and Overall Project Description
To develop a functional prototype of a solar and wind hybrid power system and evaluate its performance.
Collect and analyze the data from both energy systems which is solar power system and wind power system.
Design a hybrid energy storage system that consists of SLA battery and utilize the electric current for DC application.
Structure of Thesis
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Wind turbine is a device that able to tap some of the power of wind and convert it to mechanical energy. Generator will be use to covert the mechanical energy into electricity. In 1891, Dane Poul LaCour invented the first wind turbine which able to generate electricity . After this, engineers improved the technology to overcome energy shortages during the World Wars 1 and 2.
Table 2.1 Development of wind turbine capacity and size between 1985 and 2002
From table 2.1, the size of wind turbine increase as the demand for capacity getting higher. Main objective of the development of wind turbine is to improve the reliability and performance of wind power in generating electricity. Figure 2.1 shows the process of wind turbines generate electricity.
Figure 2.1: Process of wind turbines generate electricity
Generally, wind turbines can be separated into two basic types which have different way of turbines spins. Wind turbines that rotate around the horizontal axis are called horizontal axis wind turbines while the other type is vertical axis wind turbines.
Horizontal axis wind turbine
Figure 2.2: Horizontal axis wind turbine
Horizontal axis wind turbines which also called HAWTs are the most common style of wind turbine. It has a similar design to a windmill; it has propeller look alike blades that spin on the horizontal axis . Horizontal axis wind turbines normally use different numbers of blade, depending on the function of the wind turbine . Normally, for electricity generation, three or two-bladed turbines are being used. At the top tower of horizontal axis wind turbines, there are rotor shaft and electrical generator which pointed into the wind.
Advantages of horizontal axis wind turbines are the tall tower base allows access to stronger wind with every 10 meters up, the wind speed can increase by 20% and this leads to higher power output. Besides, horizontal axis wind turbines have higher efficiency because the blades always move perpendicularly to the wind and delivering power through the complete rotation.
Anyway there are some disadvantages of horizontal axis wind turbines. HAWTs require additional yaw control system to turn the blades towards the direction of wind. During extreme wind, HAWTs need a braking or yawing mechanism to stop the turbine from over spinning and cause damaging to itself.
Vertical axis wind turbine
Figure 2.3: Vertical axis wind turbine
Vertical axis wind turbines which also called VAWTs have the main rotor shaft arranged vertically. The main benefit of this arrangement is the wind turbine does not need to be pointed to the direction of wind . This design is suitable on sites where the wind direction is strongly variable. With the vertical axis, the wind turbine and its components can be placed near the ground and this makes the maintenance easier.
There are few advantages of vertical axis wind turbines. No yaw control systems are requiring moving the blades towards the wind direction. A vertical axis wind turbine are easier to maintenance with its location are nearer to ground. VAWTs are suitable to install at lower locations like rooftops, hilltops and mesas.
Disadvantages of vertical wind turbines are most of them have lest efficiency than a common HAWT. This is because they have higher drag as their blades rotate into the wind. The main target is to reduce drag and produce more energy. Besides, VAWTs having rotors that located near to the ground where the wind speeds are lower.