photovoltaic systems

In this article I am going to talk about the first type of photovoltaic systems

On-grid system

**The mechanism

The solar panel convert the sunlight to electromotive force And give (DC) current .
This current transferred through the dc wire to the inverter
 Alternating current then this current will injection to the local grid

The components**

-          (The solar panel )
It convert the sun line to electromotive force


 

-          (Inverter )

It convert the direct current to Alternating current






-          Ac breaker 
to provide  the necessary protection for the system





-          Dc and Ac conductor
"Dc"  wire to transfer the dc current from the solar panel to the inverter 
"Ac"  wire to transfer the ac current from the inverter to the grid 


 in the next post we are going to talk about off-grid system and the main differences
 between on and off grid system 
                
 
 



 


 
 
 

Wind Energy

Wind Energy :
we are always looking for ways to protect the earth that we are living on, these ways contains the renewable energy.
We will talk about one of these energies and that will be the wind energy.
We call these type of energy as green energy, because it helps to make our earth still green as we know it.
Wind Energy: is a clean energy source that can be found for a long time I future. Wind energy converts the natural wind in our environment and coverts that wind motion to a mechanical energy.
As we know the different location in the world have different speed or power of wind that is caused by difference in pressure. So there some locations better than other to have a power from the wind there.
Wind Turbines: it’s a big structure with spinning blades. The blades are connected to an electro-magnetic generator that give us the electricity power when the wind makes the blades spin.

advantages of Wind Energy 

1. Clean Source of Power

The production of wind energy is “clean”. Unlike using coal or oil, creating energy from the wind doesn’t pollute the air or require any destructive chemicals. 

2. Renewable Source

Wind is free. In the event that you live in a geological area that gets a lot of wind, it is ready and waiting. As a renewable asset, wind can never be drained like other regular, non-renewable assets. The expense of delivering wind energy has dropped fundamentally lately, and as it becomes more popular with the general population, it will just continue to be cheaper. You will recover the expense of obtaining and introducing your wind turbine over time.

Winds are caused by rotation of the earth, heating of the atmosphere by sun, and earth’s surface irregularities. We can harness wind energy and use it to generate power as long as sun shines and wind blows.

3. Cost Effective

Wind turbines can give energy to numerous homes. You don’t actually have to possess a wind turbine keeping in mind the end goal to harvest the profits; you can buy your power from a service organization that offers wind energy for a specific area. That means, you don’t even necessarily have to invest any cash in order to reap the benefits of wind energy for your home or business.

4. Extra Savings for Land Owners

Land holders who rent area to wind homesteads can make a considerable amount of additional cash, and wind energy likewise makes new employments in this developing engineering field. Government organizations will also pay you if they can install wind turbines on your land. Also, in some cases, the electric company may wind up owing you. If you produce more power than you require from wind power, it may go into the general electric matrix, which in turn will make you some extra cash. A win all around

Boilers

A boiler (or steam generator, as it is commonly called) is a closed vessel in which water, under pressure is transform into steam by the application of heat. Open vessels and those generating steam at atmospheric pressure are not considered to be boilers.

 In the furnace the chemical energy in the fuel is converted into heat, and it is the function of the boiler to transfer this heat to the water in the most efficient manner. thus the primary function of a boiler is to generate steam at pressure above atmospheric by the absorption of heat that is produced in the combustion of fuel .

A boiler should be designed to absorb the maximum amount of heat released in the process of combustion. This heat is transmitted to the boiler by radiation, conduction, and convection, the percentage of each depending on the boiler design. 

Boiler types :

1) Fire-tube boilers : are so named because the product of combustion pass through tubes that are surrounded by water. They may be either internally fired or externally fired. 

2) Water-tube boilers :is one in which the products of combustion pass around tubes containing water.

3) package boiler 

Nomographs in hybrid system

A Nomograph is a kind of chart that conveys the relationship between

different sets of numbers. The hybrid operation nomographs below

convey the relationship between RPM for MG1, MG2 and the engine.

Because MG1, MG2 and the engine are mechanically connected in the

Planetary Gear Set, if one of the components changes rpm, the rpm of

the other components will be affected. So in the nomograph, the rpm

values of the 3 power sources maintain a relationship in which they are

always connected by a straight line.

Figures down below shows nomographs for different  modes of Toyota Prius

1. Ready-on

 

2. Starting out

3. Engine starting

4. Light acceleration with engine

5. Low speed cruising 

6. Full acceleration

7. High speed cruising 

 

8. Maximum speed

9. Braking

10. Reverse 

Stairs

Stairs :

is a set of steps leading from one floor of a building to another, typically inside the building or   a series of steps or flights of steps for passing from one level to another.

An attractive stair  can enhance a location: fascinating, perfectly attuned to the architecture; a show piece. As a beautiful addition to your office, home or shop. Because there are so many options when it comes to style, materials and installation, staircase prices can vary tremendously. 

Stairs may be in a straight run, leading from one floor to another without a turn or change in direction. Stairs may change direction, commonly by two straight flights connected at a 90 degree angle landing. Stairs may also return onto themselves with 180 degree angle landings at each end of straight flights forming a vertical stairway commonly used in multistory and highrise buildings. Many variations of geometrical stairs may be formed of circular, elliptical and irregular constructions.

Step

Each step is composed of tread and riser.

Tread

The part of the stairway that is stepped on. It is constructed to the same specifications (thickness) as any other flooring. The tread "depth" is measured from the outer edge of the step to the vertical "riser" between steps. The "width" is measured from one side to the other.

Riser

The vertical portion between each tread on the stair. This may be missing for an "open" stair effect.

Nosing

An edge part of the tread that protrudes over the riser beneath. If it is present, this means that, measured horizontally, the total "run" length of the stairs is not simply the sum of the tread lengths, as the treads overlap each other.

Types of stairs :

• Straight Stairs.
• Straight Stair with central landing.
• L Shaped Stair.
• L Shaped Winder Stairs.
• Spiral Stairs.
• Curved Staircase.
• Library Ladder.

Geotechnical engineering

The first step to start any construction is the geotechnical investigation studies , these studies include type of soil , types of rock in the site and the it's topography .

Soil : 

There are many things that we have to know about the soil :
1- type of soil
2- physical properties
3- friction coeffecient angle
4- shear stresses
5- normal stresses
6- thermal resistivity

Any factor of these will affect on the excavation and foundation , for an example , for the weak soil may be we should use raft foundation or piles but for strong soil may be we use single footing . It doesn't affect just the type it's affect the thickness and other dimensions .

Rocks : 

The rocks are divided in three types :
1- Igneous rocks
2- sedimentary rocks
3- metamorphic rocks

Each one of these types differ from the others by physical properties , chemical properties , uses , textures and the procedure that resulted from .

Igneous rocks :

The igneous rocks is the result of magma or lava cools or hardens .

*magma is inside earth's interior 

*lava is outside earth crust

Igneous rocks are classified depending on : 

Texture size : texture mean how a rock looks and feels , and its based on the grain size .

Where the rock is made : rocks that cool slowly have larger crystals , but rocks that cools fast have smaller crystals .

Materials that the rock made from : the major silicate rock forming elements are : O , Si , Al , Fe , Mg ,K , Na , Ca . 

*When the silica percentage decrease the rock will become darker .

*Glassy texture means that the rock have no crystal grains .

In the next post we will talk about other types of rocks : sedimentary and metamorphic rocks .

Hybrid system overview

The hybrid system is the wave of the future, and now there are more incentives to purchase one. Owners of the Prius, or any other hybrid gas-and-electric vehicle, may be eligible for a federal income tax deduction. According to the internal revenue service, hybrid vehicles qualify for a long-standing tax deduction that applies to vehicles powered by clean burning fuels. The policy allows a one-minute deduction, which can be claimed by the consumer for claimed by the consumer for the year the car was first put in use.

In its simplest form, a hybrid system combines the best operating characteristics of an internal combustion engine and an electric motor more sophisticated hybrid systems, such the Toyota hybrid system,  recover energy otherwise lost to heat in the brakes and use it to supplement the power of its fuel-burning engine. These sophisticated techniques allows the Toyota hybrid system to achieve superior fuel efficiency and a massive reduction in CO2.

Hybrid system components:-

• IC engine {internal combustion engine}
• Motor generator 1
• Motor generator 2
• Planetary gear set 
• Inverter 
• HV Battery 
• HV ECU

/-Motor generator 1 

MG1

Motor generator 1 operates as the control element for the power splitting planetary gear set. It recharges the HV battery and also supplies electrical power to drive motor generator 2. MG1 effectively controls the continuously variable transmission function of the trans-axle and operates as the engine starter. 

/-Motor generator 2

MG2 is used for motive force at low speeds and supplemental force at high speeds. It provides power assist to the engine output as needed and helps the vehicle achieve excellent dynamic performance. It also function as a generator during regenerative braking.

/-The planetary gear unit

Is a power splitting device. MG1 is connected to the sun gear, MG2 is connected to the ring gear and the engine output shaft is connected to the planetary carrier. These components are user to combine power delivery from the engine and MG2, and to recover energy to the HV battery.

/-Inverter

Current between MG1,MG2 and the HV battery is controlled by the inverter. The inverter converts high voltage battery DC to AC power, and it rectifies high voltage AC from MG1 and MG2 to recharge the HV battery.

/-HV battery 

The battery stores power recovered by MG2 during regenerative braking and power generated by MG1. The battery supplies power to the electric motor when starting off or when additional power is required.

 *THS (2001−2003 Prius)   

 38 Nickel−Metal Hydrid modules 

Total voltage: 273.6V

 *THS−II (2004 and later Prius) 

    28 Nickel−Metal Hydride modules

Total voltage: 201.6V

  

Atkinson cycle

THE ATKINSON CYCLE

the Atkinson cycle significantly improved the fuel-efficiency of a four-stroke spark ignition engine through one particularly ingenious modification.

The four basic phases of the Otto cycle remained but Atkinson introduced a new timing sequence to delay the closing of the intake valve during the compression stroke. Keeping the intake valve open slightly longer effectively reduced the engine’s displacement during the intake cycle but retained the full ratio of expansion in the combustion or power stroke.

In simple terms, the Atkinson cycle was designed to minimise the use of fuel during the intake stroke yet exploit the part of the cycle that generates power.

All explained in the video below:

  https://youtu.be/uhtMEvfZkdM

Bridges engineering

Bridges is the structure element that carrying a road or a path , bridges consist from deck slab , abutment and piers .

Types of bridges :

1-slab bridge : the type of bridge that doesn't have beam , just slab on abutment and piers .

2-T-beam bridge : slab bridge subjected by T- beam consists from abutment , piers , deck slab and T-beam

3- prestressed bridge : type of bridges that have prestressed piers and slabs so the spans will be much longer and the slab is thinner .

4- Box girder bridge : is the bridge in which the main beams consist from hollow box , it may be done using prestressed concrete , steel structure or composite section from steel and reinforced concrete .

5- stayed-cable bridges : this type of bridges has towers to connect the cable with which carry the deck slab.

6-voided bridge : is a bridge that has voids inside the deck slab to reduce amount of concrete and reduce weight of structure , the voids usually circular made from galvanized steel .

Solar Energy

now we are going to talk about solar energy 

solar energy has tow main type :

1- thermal energy 

2- photovoltaics 

photovoltaics

 in this article we are going to show some information about photovoltaics technology 

Before start to explain the photoelectric technology we must know from where the sun got this enormous energy .

inside the sun it happens nuclear fusion interactions produce heat and light energy between the atoms of helium and oxygen .

The amount of light from the sun reach the Earth penetrates the atmosphere and clouds. Some of this energy is refracted and some distracted and some is absorbed by the atmosphere is up to the earth in the form of photons with high kinetic energy .

in this period pv technology was discovered and it is based on converting the kinetic energy of the photons into electrical energy

By using a semiconductor material where photons editing a stream of electrons and move them to the outside of the cell through the conductor material and is this flow of electrons so-called the current .

 types of solar cell :

till now we have three type of solar panel 

1-monocrystalline

2-polycrystalline

3-thin-film 

the most efficient is the monocrystalline but the most used is the polycrystalline because it does not affected by high temperature 

Thank you for your attention

note : in the next article we are going to know the compound of pv-system and the two main types on grid and stand alone systems .

steel structure

Today we will talk about steel structures in general and for the most important advantages and disadvantages:

The pros and cons of steel structure*

First the pros :-

1. beauty form.
2.  performance efficiency.
3.  low cost.
4.  lighting in all parts during the day.
5.  spaces and wide without prizes or columns, which provides good visibility extensive work, movement and space
6.  the possibility of a significant increase in the earth's load without additional costs
7. few dangerous incidents
8. possibility of vertically rise to the distances can not be accessed by any other material
9. Ease of installation and thus save time achievement
10. can be ceiling temporarily and then utilized unzip it and move it to another place
11. iron compliant borne vibration (such as winches in the laboratory)

Then the cons of steel structure:-

1. Deliver and store more heat and cold
2. iron needed for maintenance.
3. extensive glass areas increase the likelihood of maintenance, which means that maintenance costs are high.
4.  need for large land area for Sheds labs and spatial structures in which the roof is uncharted territory.

Prestressed concrete

Prestressed concrete is the type of concrete that has a tensioned steel inside the concrete as strands , the basic concept of this concrete is to transform the section from tension - compression section to compression -compression section .
This can be happened when the steel is tension until we reach a certain limit then we cut the steel so the force that will applied from steel to the section is compression force .

And we can reduce the stress by introducing moment from the steel by make a eccentricity from the centroid (M=P*e) and the stress will equal (stress=My/I )

The profile of the steel is called tendon and there are many shapes of it :
1- linear profile : we can called this type constant eccentricity .
2- parabolic profile : we can called this type variable eccentricity .
3- linear - parabolic profile

Method of prestressed concrete :
1- pre-tensioning : the steel is tensioned then the concrete will be cast then the steel is cut.
2- post-tensioning : the concrete is cast then the steel is tensioned and cut .

Benefits of prestressed concrete :
Allows longer span , thinner slab and fewer beams .
Lower building height.
Prevent cracking because the cracking is introducing by tension .

There are two main methods to design prestressed concrete members :
1-allowable stress method : in this method we have to check that the actual stresses is equal or less than the allowable stress .
2- load balancing method : in this method we design prestressing steel to carry a percentage of dead load .

There are many things that can be affect on the design such as :
1- type of tendon : bonded or unbonded tendon
2-type of steel : low or normal relaxation
3-the strength of concrete

In the prestressing process the total force doesn't remain constant , there is a drop in force due to losses  :
1-short term losses : it is immediate losses occur during prestressed of tendons .
a-elastic shortening of concrete
b-slip at anchorage
c-friction

2-long term losses : it's time dependent losses
a-creep and shrinkage .
b-relaxation of prestressed steel .

Rankine Cycle

The figure above shows Rankine cycle which includes the following  processes :

2-3 Boiler : in this stage compressed water at point (2) enters the boiler to increase it's temperature by heat exchange between fire and water, it then leaves as superheated vapor at point (3).This process called Isobaric process since the pressure during this process remains constant .

3-4 Turbine : superheated vapor (high pressure and high temperature) enters the turbine, during this process the vapor will expand and rotate the blades of the turbine. the turbine connected with electrical generator to produce electricity,after this vapor leaves the turbine as mixture of liquid and vapor state at low pressure at point (4).This process called Isentropic process that means equal entropy process.

4-1 Condenser :  isobaric process, the mixture will condensate by convection or conduction heat transfer between the air or the pipes of cooled water, so it will leave as saturated liquid at point (1). 

1-2 Pump : isentropic process in which the saturated liquid will increase it's pressure and leave the pump as compressed liquid to enter the boiler again. 

Gearbox

Introduction:-

An automobile requires high torque when climbing hills and when starting, even though they are performed at low speeds. On other hand, when running
at high speeds on level roads, high torque is not required because of momentum.  So requirement of a device is occur, which can change the vehicle’s torque and its speed according to road condition or when the driver need. This device is known as transmission box.

Function of transmission box (gear box) in automobile:

The transmission box which is also known as the gear box is the second element of the power train in an automobile. It is used to change the speed and torque of vehicle according to variety of road and load condition. Transmission box change the engine speed into torque when climbing hills and when the vehicle required. Sometimes it is known as torque converter. Main functions of a gear box is as follow:

1. Provide the torque needed to move the vehicle under a variety of road and load conditions. It does this by changing the gear ratio between the engine crankshaft and vehicle drive wheels.

2. Be shifted into reverse so the vehicle can move backward.

3. Be shifted into neutral for starting the engine.

Main components of a gear box:

In any device two or more component works together and fulfills the required function. In a transmission box four components are required to fulfill its function. These components are-

1. Counter shaft:

Counter shaft is a shaft which connects with the clutch shaft directly. It contains the gear which connects it to the clutch shaft as well as the main shaft. It may be run runs at the engine speed or at lower than engine speed according to gear ratio.

2. Main shaft:

It is the shaft which runs at the vehicle speed. It carries power form the counter shaft by use of gears and according to the gear ratio, it runs at different speed and torque compares to counter shaft. One end of this shaft is connects with the universal shaft.

3. Gears:

Gears are used to transmit the power form one shaft to another. They are most useful component of transmission box because the variation is torque of counter shaft and main shaft is depend on the gear ratio. The gear ratio is the ratio of the driven gear teeth to the driving gear teeth. If gear ratio is large than one, the main shaft revolves at lower speed than the counter shaft and the torque of the main shaft is higher than the counter shaft. On other hand if the gear ratio is less than one, than the main shaft revolves at higher speed than the counter shaft and the torque of the main shaft is lower than the counter shaft. A small car gear box contains four speed gear ratio and one reverse gear ratio.

4. Bearings:

Whenever the rotary motion, bearings are required to support the revolving part and reduce the friction. In the gear box both counter and main shaft are supported by the bearing.

Working of a principle gear box:

In a gear box, the counter shaft is mashed to the clutch with a use of a couple of gear. So the counter shaft is always in running condition. When the counter shaft is bring in contact with the main shaft by use of meshing gears, the main shaft start to rotate according to the gear ratio. When want to change the gear ratio, simply press the clutch pedal which disconnect the counter shaft with engine and change connect the main shaft with counter shaft by another gear ratio by use of gearshift lever. In an gear box, the gear teeth and other moving metal must not touch. They must be continuously separated by a thin film of lubricant. This prevents excessive wear and early failure. Therefor a gearbox runs partially filled with lubricant oil. 

Refrigeration Cycle

Simple form of refrigeration cycle is shown in the following figure : 

Refrigeration cycle  : is a closed loop where the refrigerant flows through it . 

The Refrigerant enters evaporator at low temperature low pressure, where it absorbs the heat from the refrigerated space by convection heat transfer between the air space and the refrigerant. Refrigerant leaves the evaporator and enters the compressor as a slightly superheated vapor at a low pressure, it then leaves the compressor at high pressure vapor to enters the condenser, in condenser the heat absorbed during evaporated process of the refrigerant, it will rejected by convection heat transfer between the refrigerant and ambient air or cooling water, whereas the refrigerant will condensate and leaves the condenser as a high pressure low temperature liquid. The function of the expansion valve is to reduce the pressure of the refrigerant before entering the evaporator.   

The refrigerant's safety properties :

•  unflamable

• nontoxic 

• does not react with air and materials 

• Cheap and easy production

Most common types of refrigerants :

Freons : R11 , R12 , R22 , R134 , R502 , R717 , R404

ammonia : NH3

The Energy

The energy 

Before we begin explained about renewable energy there is information that you should know about the the energy .

What is energy ?

I notice that when I ask this question , they usually have trouble giving an exact definition.

And I must say it is not easy.

The scientific definition for energy would be something like: the capacity of a system to perform work.

why we need energy ?

We humans use energy to do some work.

We use energy for heating air and water.

We use energy for transportation of people and products by cars, trains, trucks and planes.

We use energy to produce food and products.

We use energy to illuminate houses and streets.

We use energy to watch TV, do our laundry, working on computers and surfing the internet.

At the moment you are consuming energy to read our post 

 what is the types of energy ? 

Energy appears in many forms in our daily life, like, kinetic or mechanical energy, electrical energy, heat radiation, wave energy, chemical energy and nuclear energy.

The total amount of energy is always conserved.

This means that if we want energy to work for us, we usually convert it from one form to another form.

An example is the electric motor, this is a tool in which we convert electrical energy into mechanical energy.

The unit of energy :

The unit of energy is joule (J)

Power is the energy per time and is expressed in watts (W).

1 watt is 1 joule per second.

1 kWh equals the energy of a power of 1 kW being used for 1 hour .

Thanks for paying attention

note:{ the next post will be about the first type of renewable energy and the most popular type 

          "the solar energy " and we will learn the tow types of solar energy } .

Columns

The second structural element is column (compression member) ,this element which provide construction elevation and connects the footing with beams and slabs to transfer the loads .

types of columns according to braces :

1-braced column; this system prevent the side sway because of connection columns with beams , most of braced columns is made from steel , and this is one of it's good features and the other one is to carry lateral load like wind load and seismic load.

2-unbraced column; this types of column didn't prevent side sway and can't carry any of lateral loads .

types of columns according to column cross sectional shape :

1-Circular columns 

2-Rectangular columns

3-Square columns 

4-Hexagonal columns

types of columns according to column's length :

1-long columns : when the ratio of length to least cross sectional dimension is more than 12
2-short columns : when the ratio of length to least cross sectional dimensions is less than 12 and more than 3 

Buckling in columns 

The short columns will fail in compression before it reach buckling , but the long columns will fail firstly in buckling and this depends on many factors :

1-length of columns

2-cross section dimensions 

3-the fixity of column's end

4-slenderness ratio

ties in columns :

types of ties in columns :

1-rectangular ties

2-spiral tieds

we use ties in columns to :

1- bind and hold longitudinal bars .

2-prevent concrete from splitting outwards

3-resisting horizontal force (shear )

4-spiral ties are carrying 10% of the axial load on the column .

       columns reinforcement