Solar Energy

Importance of Solar Energy

Solar Energy is very reliable and cheap way of electricity especially in very hot countries like Saudi Arabia, Dubai, Pakistan, India etc.

The maintenance cost and initial cost of the solar power system are low.When it is installed in the feasible region it will work a long time.

Solar System

There are  no easy way to build a solar system you have to know how much amount of sunlight is required and completely know the location of the sun on sky which very time to time but can be determine by by using complex set of equations.
We have to find the average intensity of sun (clear day, partly cloudy day, cloudy day) from the complicated set of the equation.

Solar Spectrum

For solar system we use Sun as a insulation source. The diameter of sun is 1.4 million Km with nuclear blast of hydrogen atom into the helium and as a result 3.8 * 1020 MW amount of Magnetic energy emits out word (toward space) and small amount of energy come on earth.

Black Body Effect

According to this concept black body is perfect emitter (emits more energy as compared to other real object for same temperature) and absorb (absorb more energy that fall upon it). Black body is used to a standard to measure the radiation of anything which radiate and its wavelength which is emitted depends upon the Temperature of the body.
Planck's Law explains by this equation.

The radiation of-of the sun move across the earth surface faced difficulty because a lot of small constituents are present in our atmosphere which cause by decrease the radiation and spectrum of the earth deformed or choppy shape.

Air Mass Ratio

It is the ratio of path h₂ use the rays of sun after passing the atmosphere and h₁ the short path length from the sun to earth. When the sun at 90-degree w.r.t to earth.

Formula:

B = The sun  altitude angle.

The air mass ratio ' m ' calculation.

Solar spectrum for  (m = 0),for sun directly overhead

(m = 1), and at the surface with the sun low in the sky, m = 5. From Kuen et al. (1998),

based on Trans. ASHRAE, vol. 64 (1958), p. 50.

SUN PATH DIAGRAMS FOR SHADING ANALYSIS

Photo voltaic is very important to find the exact path of sun at any region in particular time duration with complete information of shade shape and size because Photo voltaic is very shadow sensitive. This diagram gives complete knowledge about the signs of obstruction in specifics periods of time. It give the time when area will be in shade and sun will be back of obstruction.

There are a lot of method and product to find out the hurdles on the way of sun. One of the good and cheap way is to use your geometry box tools with a typical compass but it’s your effort. By using plumb bob 

,protector and compass. Azimuth angle is measured from the compass and altitude angle from plumb bob.

Magnetic Declination or Deviation

 According to the phenomena, compass should point towards magnetic north but they point true north this difference called magnetic declination or deviation.

Example

Here in it show that due to trees the sun light not reach through November to January at the time of 8:30 AM to 9:30 PM approximately 1 hour.

The shade projection causes the sun light lost round about 3 o clock.

Sun Path diagram with obstruction and time period

Solar Angle 

Parameters and  Summary Solar Angle 

Photovoltaic System

An individual PV cell is usually small, typically producing 1 or 2 watts of power which is enough to run low-power calculator. Since the PV cell is essentially a diode, forward bise voltage of diode is typically .7 V. The PV cells are connected together in parallel and series arrangement to increase the power rating. To boost the power output of PV cell. They are connected together to form large unites called modules.  If V is the voltage of cell and m is number cells are connected in series, the voltage of modules is V mod = mV. Modules in turn can be connected in parallel to form even larger unit called array. Which can be inter connected to produce more power. If I is the current capability of a cell and n number of modules are connected in parallel, the current capability of an array is

iar = ni

Therefor output power of cell array becomes Par = mnVI.

That is the array power becomes mn times of a single cell power PC. PV system can be built to meet almost any electric power need small and large. Several of these array from PV system. The tracking devices are tilt on arrays to maximize the exposure of the cells to the sun arrays. A PV system is normally operated to maximize the power at Vmp and Imp. The operating point is known as Maximum Power Point (MPP).

An input capacitor is normally connected to the output of the PC array to provide a low path for the input current of the dc-dc convert. Equating the currents at the inputside of the boost convertor, we get

ip = i_cdp + ii = C_i (dvp/dt) + i_i

Under steady state condition is is equal current ii. Therefor operating point move toward MPP by adjusting ii. The algorithm shown in equation for implementation require measuring PV array voltage and current which is used to measure the Power and slop.  Therefor based on the sign of the slop (dpp/dvp), the reference current Iref is increased or decreased by moving the operating point toward the zero slope point. 

Importance Of Photo Voltaic In Solar System

Photo voltaic (PV) material and devices convert sunlight in to electrical energy and PV cell are commonly knows are solar cells. The PV cells are electricity producing device made of semiconductor material PV can literally be translated as light-electricity. PV has two part: photo drive from Greek word for light and volt relating to electricity pioneer.

PV system are already an important part of our daily life. Simply PV provides the power for small consumer’s items such as calculator and wristwatches. More complicated system provide power for communication satellite, water pumps and machines for home and small industries. Many road and power system are also powered by PV System. In many cases PV power are least expensive than the other electricity.

Photovoltaic Cells

PV cells are the buildings block for all PV systems because they are the device that convert sunlight to electricity. It’s come many size and shapes, for smaller then a postage stamp to several inches across. They are often connected to gather to from PV modules that may be up to several feet long. And few feet wide. Modules in turn can be combined and connected to form PV array of different size and power output. The modules of the array make up important part of the PV System.

When light shines on PV cell it may be reflected observed and pass through. But only the observed light produced electricity. The energy of the observed light transferred to the electron in the atom of the PV cell semiconductor material.  A special electrical property of PV cells are called a built-in electric field provides the force and voltage needed to drive the current through a external load such as light bulb.

Types of PV Cells

 Flat plate

The flat plate PV is rectangular and flat this is the most common type of PV array used in most comment appliances. Flat cells are often mounted at fixed angle that maximize the exposure to the sun through the year. In more flexible system, the angle of sola plate change and to track the optimal sun exposure during the day.

      Convex lens

Convex lens concentrating on PV cells require less material for the same power output then the flat plate cells. Thus they are smaller in size, however concentrating cell operate beat when the sky clear of cloud.

The PV current can be related to the cell voltage by the Schockley Diode equation.

What is Solar Tracking System &How it is Work

It is said that far a time that the collector which is not move because it is attached to the surface. in the most circumstances it is look that collector which is used to follow the path of sun in the vast sky due to permission of racks are most cost effective.
There are two types of tracker
Two- axis Tracker
Single-axis Tracker
Two- Axis Tracker tracks the sun in from of two angels-like Azimuth and the Altitude angels so that the collectors show the right direction of Sun always.

Here to calculate the diffuse insolation and the beam plus at the 2-axis tracker are simple.

The beam of sun hit to the collector completely fill the isolation IB which is perpendicular the rays calculated from this equation.

The tilt angle of the collector will be same or equal to the solar altitude angle which is

 The  reflected and diffuse angle combination exaim the following equations.

The Single- Axis Tracker can track one angle azimuth or the Altitude. The photovoltaic are always adjust by the manually north- south axis according to the tilt angle. The tracking phenomena which is used to rotate the east-west array of collectors shown in the figure.

Single axis tracking with West-East Movement

Polar mount

Mount tilt angle and the local latitude becomes equals knows as the Polar mount angle.

The center line of the collector point straight in to the Sun when the rotation of the polar mount about its axis becomes match the rotation of earth which is 15 degree per hour as shown in the figure (a).

(a)                  Pole mount single axis tracker   (b)        north pole

The angel of incidence which is perpendicular between rays of sun and collector. At this condition incidence angle equal to the solar declination. To estimate the radiation of diffuse and reflected one of the important is knowledge of collector angle.

 One-Axis, Polar Mount