Design and Operation Optimization of a Solar Collector System

This thesis introduces the concept of Concentrated Solar Power utilization for the production of Electrical Energy. As the world economy grows and the technology growth booms, the dependability on more robust, ingenious and cost effective ways of generating electricity becomes essential. Solar Energy is currently striving to become a major player in fulfilling the energy needs of the modern world with environmental aspects guaranteeing a safer future for our generations. There are two main ways through which solar energy from sun is employed to produce electricity i.e. Photo-voltaic cells and Concentrated Solar Power. Little work has been carried out in the field of Concentrated Solar Power (CSP) but there is still room for significant improvement. Concentrated Solar Power has a lot of potential in our country considering the abundance of solar radiation throughout the year particularly in the southern region. The proposed design will be scalable to industrial level. This research project is one of its kind considering not much work has been carried out previously in this regard in Pakistan. The following report contains detailed design strategies for making a Heliostat. We carried out work on Heliostat design in our institute and significantly improved the previous designs of any such tractable heliostat thus enhancing the efficiency of the system.

Heliostat Design

1        Heliostat Design

The Design of the heliostat is a very important task. A good design can enhance the efficiency of the system significantly. It is also necessary in order to effectively withstand various static & dynamic loads that the heliostat will face.

Following are some of the aspects of Heliostat design and other parameters associated with or related to the design of heliostat.

•      Field Selection for Heliostats/Polar Field

•      Selection of Frame Arrangement/Horizontally rectangular main frame

•      Shape and design of the Mirror/Slightly tilted mirrors

•      Wireless And autonomous control

•      Tracking of primary axis

•      Wind Protection

•      Hail protection /Rain protection

Design Features of A Heliostat

1        Heliostat Field Selection

From case studies of different mega projects involving SCSs (solar tower) we observed that the heliostats were arranged in one of the following configurations

1.      Surround Field

2.      Polar Field

1.1      Surround Field

In this configuration the solar tower is completely surrounded by heliostats on all sides. This configuration has an added advantage that the total insolation remains relatively more uniform throughout the day. When the sun moves from one side of the tower to the other side then the heliostats on the opposite side start to reflect the sun rays more effectively hence maintaining a uniform profile.

It has been experimentally observed that the efficiency of the heliostats nearest to the tower is maximum & it decreases as the distance increases. In surround field configuration more heliostats can be placed inside this high efficiency region.

This type of field is used in Ivanpah (392 MW).

1.2      Polar Field

In this type of field all the heliostats are placed on one side of the tower.

This characteristic can be utilized in medium to large sized solar tower systems(STS). If the same number of heliostats is arranged in polar field instead of surround field then due to their increased efficiency more energy will be generated with the same initial cost

Due to above mentioned reasons we are going to use “Polar Field”.

1.2.1    Mechanical Design

The mainframe of the heliostat is designed to be rectangular with its length greater than its height. This arrangement will give us following benefits

1. Due to smaller height, the heliostat will cast a smaller shadow on the mirrors behind it as opposed to a vertically erect rectangular heliostat.
2. The distance between consecutive rings can be decreased due to smaller shadow of front row heliostat which will result in increased system efficiency.
3.   The center of gravity will be lower to the ground which will increase stability of the mechanical system while facing wind.
4.      Smaller height will result in smaller moment arm so the assembly can bear high forces without being overturned.
5. The frame will be rotated along the horizontal axis while the mirror will rotate along the vertical axis.

Mirror Manufacturing for Solar Concentrator

Selection of Reflective Mirror

In almost all of the STSs plane mirrors are used. The reason is that the cost of manufacturing curved mirrors is enormous which results in an increased amount of capital required to install the plant.

Despite the higher cost, curved mirrors were selected for this project due to following reasons

1.      Through literature survey we came to know that in terms of “Levelized Cost of Electricity” (LCOE) reduction, a design improvement that results in 1% performance improvement is equivalent to a design improvement that reduces solar field cost by about 2.3% i.e. the leverage of performance vs. cost on LCOE is better by a factor of about 2.3x

The exact improvement in efficiency due to this decision is unknown at this stage & it is possible that this improvement might not be able to balance out the increase in capital cost. Any and all results will be reported at the end of the project including the impact of this decision.

2.      There is another factor that inspired us to use curved mirrors. As the distance from the solar tower increases, the effect of scattering from dust particles becomes more and more pronounced. Thus the advantage of using a converging beam of light become more evident as this kind of reflected beam will be able to transfer a considerably more amount energy to the solar tower even after scattering.

3.      As the beam is converging therefore the area of the “wave front” formed at the receiver will be of small size. This enables us to design a receiver of smaller size which will reduce cost.

4.     Higher concentration of light due to converging beam will result in increased temperature which will result in increased efficiency of the system.

5.     Very high precision tracking is usually not feasible. The decreased wave front area of the reflected beam gives us an increased margin of tolerable error in our tracking.

Fabrication of Solar

Building a solar car is not a simple project. It needs determination and lots of study about solar energy. You must known that how to convert solar energy in to battery power. It is really a expensive project. This project includes lots of calculations on how much energy is required, how fast energy can be stored and how can we achieve maximum efficiency etc.

The solar powering system of the car consists of:
1. Solar Array which collects solar energy and converts it to electrical energy
2. Power trackers to achieve the proper voltage to be stored in batteries.
3. Batteries to stire power.
4. Motor controller which adjusts the power input to the motor.
5. An electric motor which drives the vehicle.

 The main component of a solar car is its solar array, which collect the energy from the sun and converts it into usable electrical energy. The solar cells collect sun energy and store it into the batteries of the solar car. Before that happens, power trackers converts the energy collected from the solar array to the proper system voltage, so that the batteries and the motor can use it. When the energy is stored in the batteries, it is available for use by the motor & motor controller to drive the car. The motor controller checks the amount of energy that flows to the motor to correspond to the throttle. The motor uses that energy to drive the wheels.

Author

William shih

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Vehicle Skid Control

Vehicle skid can be defined as the loss of traction between a vehicle’s tyres and the road surface due to acting of force on the vehicle. Most skids are caused by drivers mistake. About 15% accidents are caused due to vehicle skidding. Skids occurring in other accidents are usually the result of last minute action, by the driver, when faced with a crisis ahead rather than actually causing an accident. Skids can occur in any climatic condition weather it is dry or icy conditions, but the chances of losing vehicle control and having an accident increases by 50% in the wet. The most common type of skid we will be confronted with is when the rear end of the car slides out, causing an over steer or when the front of the car plows toward the outside of a turn without following the curve of the turn causing an under steer. Usually, over steer occurs as a result of going into a corner too fast or incorrectly hitting a slick area, causing the rear wheels to over steer. A third skid called the four wheel skid can also occur, where all the four wheels lock up and the vehicle slides in the direction where the forward momentum is carrying it, with no directional control.

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Design and Fabrication of Electric Bike

Electricity is an essential part of our life. Now-a –day electricity is used in public transport vehicles like local trains. With the shortage of fossil fuels, increasing fuel costs, rising levels of pollution, electricity fuelled vehicles are the future of personal transportation. The present project dealt with design and fabrication of electric bike (cycle). Modeling, Design and Analysis of the frame was performed in unigraphics. This was successful for a test run for 45 minutes with no decrease in voltage rating in the battery. The designed cycle is capable of taking 85 kg as Pay-load capacity.

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Hybrid Electric Vehicles (HEV) (Clean & Fuel Saving Technology)

In present age automobiles are identified as one of the major causes of air pollution and energy depletion. Vehicles are also identified for their low efficiency in other words high-energy loss. Hybrid Electric Vehicles have the capacity to overcome these situations and bring a new revolution. Hybrid vehicle combine two or more sources of power directly or indirectly provides propulsion power. The gasoline electric hybrid vehicle is of crossbreed between a gasoline powered vehicle and electric vehicle. Hybrid vehicles run both with a rechargeable battery as well as gasoline. In a hybrid engine, gasoline power and power from a set of batteries transmits power to an electric motor. There are less adverse effects due to the Hybrid electric vehicles. The batteries used in hybrid vehicles are rechargeable Nickel metal hydride, Lead acid batteries and Lithium Polymer batteries are disposable which will not pose any toxic hazards to the atmosphere. The fact about hybrid vehicles is that the DC machine is that it can run both as a motor as well as a generator .In addition to this hybrid vehicles use a system that recovers power from the momentum of the vehicle when we apply brakes. The Hybrid vehicles are complicated machines when compared to their counterparts of the gasoline-powered vehicles. But due to higher efficiencies, lower emissions of hybrid vehicles gain the attention of the new ERA.

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