Download Free Android App For REnergy!!

This is a free android app for this blog : REnergy. I've built this app for the users of my blog to access my posts, works with ease. The best thing of this app that you can now view, comment, share and everything else just by some taps with your android smart phone. I'm trying to add an option to login and post an article directly via this app from the user's smart phone. You still can download it and install in your android smart phone for easy access of this blog. please see more of this post for download and documentation.

NOTE: This app is yet not published in google play android market. I'm using a free android market - ibuildapp.com to host this application. So at the time of installation the android smart phone will ask to change the setting of your phone. Please change it to accept apps from other than google play store.

Feel free to download and use this app, checked and verified by:

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REJUVENILE INVENTION BY MIT

MIT engineers have transformed bacterial cells into living calculators that can compute logarithms, divide, and take square roots, using three or fewer genetic parts.
Inspired by how analogue electronic circuits function, the researchers created synthetic computation circuits by combining existing genetic “parts,” or engineered genes, in novel ways.
The circuits perform those calculations in an analog fashion by exploiting natural biochemical functions that are already present in the cell rather than by reinventing them with digital logic, thus making them more efficient than the digital circuits pursued by most synthetic biologists, according to Rahul Sarpeshkar and Timothy Lu, the two senior authors on the paper, describing the circuits in the May 15 online edition of Nature.

“In analog you compute on a continuous set of numbers, which means it’s not just black and white, it’s grey as well,” says Sarpeshkar, an associate professor of electrical engineering and computer science and the head of the Analog Circuits and Biological Systems group at MIT

Analog computation would be particularly useful for designing cellular sensors for pathogens or other molecules, the researchers say. Analog sensing could also be combined with digital circuits to create cells that can take a specific action triggered by a threshold concentration of certain molecules.
“You could do a lot of upfront sensing with the analog circuits because they’re very rich and a relatively small amount of parts can give you a lot of complexity, and have that output go into a circuit that makes a decision — is this true or not?” says Lu, an assistant professor of electrical engineering and computer science and biological engineering.
Lead author of the Nature paper is MIT postdoc Ramiz DanielJacob Rubens, a graduate student in microbiology, is also an author of the paper.
Analog advantages
Sarpeshkar has previously identified thermodynamic similarities between analog transistor circuits and the chemical circuits that take place inside cells. In 2011, he took advantage of those similarities to model biological interactions between DNA and proteins in an electronic circuit, using only eight transistors.
In the new Nature paper, Sarpeshkar, Lu and colleagues have done the reverse — mapping analog electronic circuits onto cells. Sarpeshkar has long advocated analog computing as a more efficient alternative to digital computation at the moderate precision of computation seen in biology. These analog circuits are efficient because they can take in a continuous range of inputs, and they exploit the natural continuous computing functions that are already present in cells. In the case of cells, that continuous input might be the amount of glucose present. In transistors, it’s a range of continuous input currents or voltages.
Digital circuits, meanwhile, represent every value as zero or one, ignoring the range of possibilities in between. This can be useful for creating circuits that perform logic functions such as AND, NOT and OR inside cells, which many synthetic biologists have done. These circuits can reveal whether or not a threshold level of a certain molecule is present, but not the exact amount of it.
Digital circuits also require many more parts, which can drain the energy of the cell hosting them. “If you build too many parts to make some function, the cell is not going to have the energy to keep making those proteins,” Sarpeshkar says.
Doing the math
To create an analog adding or multiplying circuit that can calculate the total quantity of two or more compounds in a cell, the researchers combined two circuits, each of which responds to a different input. In one circuit, a sugar called arabinose turns on a transcription factor that activates the gene that codes for green fluorescent protein (GFP). In the second, a signaling molecule known as AHL also turns on a gene that produces GFP. By measuring the total amount of GFP, the total amount of both inputs can be calculated.
To subtract or divide, the researchers swapped one of the activator transcription factors with a repressor, which turns off production of GFP when the input molecule is present. The team also built an analog square root circuit that requires just two parts, while a recently reported digital synthetic circuit for performing square roots had more than 100.
“Analog computation is very efficient,” Sarpeshkar says. “To create digital circuits at a comparable level of precision would take many more genetic parts.”
Another of the team’s circuits can perform division by calculating the ratio of two different molecules. Cells often perform this kind of computation on their own, which is critical for monitoring the relative concentrations of molecules such as NAD and NADH, which are frequently converted from one to the other as they help other cellular reactions take place.
“That ratio is important for controlling a lot of cellular processes, and the cell naturally has enzymes that can recognize those ratios,” Lu says. “Cells can already do a lot of these things on their own, but for them to do it over a useful range requires extra engineering.”
That extra engineering included modifying the circuits so that they can compute with inputs over a range of 1 to 10,000 — much wider than the range of a naturally occurring cell circuit.
“It’s nice to see that frameworks from electrical engineering can be concisely and elegantly mapped into synthetic biology,” says Eric Klavins, an associate professor of electrical engineering and adjunct associate professor of biological engineering at the University of Washington who was not part of the research team.
The researchers are now trying to create analog circuits in nonbacterial cells, including mammalian cells. They are also working on expanding the library of genetic parts that can be incorporated into the circuits. “Right now we’re using three of the most commonly used transcription factors in biology, but we’d like to do this with additional parts and make this a generalizable platform so everyone else can use it,” Lu says.
“We have just scratched the surface of what sophisticated analog feedback circuits can do in living cells,” says Sarpeshkar, whose lab is working on building further new analog circuits in cells. He believes the new approach of what he terms “analog synthetic biology” will create a new set of fundamental and applied circuits that can dramatically improve the fine control of gene expression, molecular sensing, computation and actuation.
The research was funded by MIT Lincoln Laboratory, the Office of Naval Research and the National Science Foundation.

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JU prof nominated for Becquerel Prize!!!

Courtesy: Times of India

A teacher of the electronics engineering department in Jadavpur University — has been nominated for the 2013 Edmond Becquerel Prize.

    Colleagues of Ghosh consider the nomination as a huge achievement in itself, given the rarity of the award been conferred to scientists beyond Europe. Japan’s Masafumi Yamaguchi is the only recipient of the award from Asia.

    World Council for Renewable Energy chairman Wolfgang Palz has nominated Ghosh “for his outstanding contributions in developing photovoltaic cells in general and thinfilm photovoltaic cells in particular.”

    “It is important considering one cannot self-nominate himself and neither can his institute recommend the name for the award,” said Ghosh, who is currently working in various projects in Kyrgyzstan and Sierra Leone.

    “In Kyrgyzstan, I have been working on a project to take solar power to the rural population of that country. In Sierra Leone, we have set up a business incubation centre and the solar power work was done by me. In Gujarat, I am involved in the solar power project of 10 mega watt.

    “In addition, the philosophy behind my nomination also mentions that I have taken PV power in 1984 to the deep island village in Bay of Bengal for their participation in education, entrepreneurship development, quality and effective economic activities. Implementation of PV power enhanced the human development index to 16-17% higher than its previous figure. The results have been published in a paper at the Solar World Congress.”

    It may be noted that Ghosh has authored 150 scientific and technological publications.

    Partha Pratim Biswas, his colleague at the university, said: “He is a valuable asset to the institution and has already received international recognition for his work. Now, his nomination for the award yet again proves the multi-dimensional excellence of JU.”

Biswajit Ghosh was nominated by World Council for Renewable Energy chairman Wolfgang Palz 

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Commonly Used Algorithms for MPPT

The amount of electrical power generated by a photovoltaic system depends on solar irradiance (solar energy per unit area of the solar panel’s surface) and other conditions such as temperature and cloud cover. The current and voltage at which a solar module generates the maximum power is known as the maximum power point. The location of the maximum power point is not known in advance.Solar inverters or charge controllers use maximum power point tracking (MPPT) to get the maximum possible power from the PV array. Solar cells have a complex relationship between solar irradiation, temperature and total resistance that produces a non-linear output efficiency known as the I-V curve.
It is the purpose of the MPPT system to sample the output of the cells and determine a resistance (load) to obtain maximum power f or any given environmental conditions. Essentially, this defines the current that the inverter should draw from the PV in order to get the maximum possible power (since power equals voltage times current).

The current and voltage at which a solar module generates the maximum power is known as the maximum power point

Maximum power point tracking (MPPT) modifies the electrical operating point of a solar energy system to ensure it generates the maximum amount of power. This involves finding the current or voltage of the solar panel at which maximum power can be generated. MPPT improves the electrical efficiency of a solar energy system, thus reducing the number of solar panels or arrays required to generate a desired output.

Different Types of MPPT Algorithm

There are various methods or algorithms available to implement Maximum Power Point Tracking. Among them, the most efficient and commonly used methods are-

• Perturb & Observe Method (P&O)

• Incremental Conductance Method (INC)

• Constant Voltage Method

• Current Sweep Method

I'll Discuss briefly on  P & O Method and INC as these two methods used commonly.

• Perturb & Observe Method (P&O)

In this method, the device (controller/inverter) adjusts the voltage by a small amount from the array and measures power; if the power increases, further adjustments in that direction are tried until power no longer increases. This method is most common, although this method can result in oscillations of power output. It is referred to as a hill climbing method, because it depends on the rise of the curve of power against voltage below the maximum power point, and the fall above that point. Perturb and observe is the most commonly used MPPT method due to its ease of implementation. This method may result in top-level efficiency, provided that a proper predictive and adaptive hill climbing strategy is adopted.
I've added a flowchart for better understanding of this Method.

• Incremental Conductance Method

In the incremental conductance method, the controller measures incremental changes in array current and voltage to predict the effect of a voltage change. This method requires more computation in the controller, but can track changing conditions more rapidly than the perturb and observe method (P&O). Like the P&O algorithm, it can produce oscillations in power output. This method utilizes the incremental conductance (dI/dV) of the photovoltaic array to compute the sign of the change in power with respect to voltage (dP/dV).
The incremental conductance method computes the maximum power point by comparison of the incremental conductance (ΔI/ΔV) to the array conductance (I/V). When these two are the same (I/V=ΔI/ΔV), the output voltage is the MPP voltage. The controller maintains this voltage until the irradiation changes and the process is repeated.

For Further details on Perturb and Observe Method, please follow this link: Perturb and Observe Method

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Maximum Power Point Tracking : Basic Overview

Solar inverters or charge controllers use maximum power point tracking (MPPT) to get the maximum possible power from the PV array. Solar cells have a complex relationship between solar irradiation, temperature and total resistance that produces a non-linear output efficiency known as the I-V curve. It is the purpose of the MPPT system to sample the output of the cells and determine a resistance (load) to obtain maximum power f or any given environmental conditions.
Essentially, this defines the current that the inverter should draw from the PV in order to get the maximum possible power (since power equals voltage times current).

Working Principle of Maximum Power Point Tracking:

A Maximum Power Point Tracking solar regulator will simulate the load required by the solar panel to achieve the maximum power from the cell.  The regulator will work out at which point the cell will output the maximum power and derive from this the voltage and current outputs required for maximum power to be achieved.  It will then calculate the load that it must simulate based on these voltage and current levels R=V/I.  The regulator, now receiving the maximum amount of power in, will then regulate the output according to what it is designed for.

In this image you can see that if we use a inverter which works without an MPPT algorithm, then the system become in-efficient or in other words there will be losses in utilizing the solar power. But we use an inverter which works on a MPPT algorithm then the utilizing of power is far better.

Now let's talk about the Fill Factor (FF) which is a very important and of course an integral part of the MPPT methodology.

The fill factor, more commonly known by its abbreviation FF, is a parameter which, in conjunction with the open circuit voltage and short circuit current of the panel, determines the maximum power from a solar cell. A solar micro-inverter in the process of being installed . The ground wire is attached to the lug and the panel's DC connections are attached to the cables on the lower right. The AC parallel trunk open circuit voltage and short circuit current of the panel, determines the maximum power from a solar cell. Fill factor is defined as the ratio of the maximum power from the solar cell to the product of Voc and Isc.

So, the mathematical expression of Fill Factor is FF=(Imp x Vmp) / (Isc x Voc)

Benefits By Using MPPT Based Devices In Solar PV System 

MPPT ensures that you get the most power possible from your solar panels at any point in time. It is particularly effective during low light level conditions. These calculations result in an output that delivers maximum current at the required voltage at any point in time.  During low light level situations it will compensate for the low light level and find the new point at which the solar cell delivers its maximum power output.

For Details on the Classification of MPPT and the MPPT Algorithm, please see the other posts.


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Solar Tracker : Advantage and Disadvantage

Solar tracker is a component/tool/plugin in solar PV system which let the solar panels/arrays facing the sunlight directly or you can say at 90 degree angle respect to the sun-light. In other words-"A solar tracker is a device that orients a payload toward the sun. Payloads can be photovoltaic panels, reflectors, lenses or other optical devices."
In flat-panel photovoltaic (PV) applications, trackers are used to minimize the angle of incidence between the incoming sunlight and a photovoltaic panel. This increases the amount of energy produced from a fixed amount of installed power generating capacity.
In standard photovoltaic applications, it is estimated that trackers are used in at least 85% of commercial installations greater than 1MW from 2009 to 2012.

Advantages:

The advantages of solar tracker are listed below:

• Solar tracking systems are used to continually orient photovoltaic panels towards the sun and can help maximize the investment in PV system.

• They are beneficial as the sun's position in the sky will change gradually over the course of a day and over the seasons throughout the year.

• Advantages to using a tracker system like this will depend mainly on it's placement in determining how well it will increase the effectiveness of the panels.

• energy production is at an optimum and energy output is increased year round. This is especially significant through out the summer months with its long days of sunlight available to capture and no energy will be lost.

• For those with limited space this means that a smaller array only needs to be installed, a huge advantage for those smaller sites with only a small area to place solar tracker.

Comparison between fixed and with-tracking solar PV system

Disadvantages

Now let's discuss about the disadvantages of solar tracking system. Today, with boom in solar technology, the use of solar tracker is not necessary as it increases the total set-up cost of the system. The main disadvantages of using solar tracking system are listed below:

• The stand alone PV home kit system is a very reliable and uncomplicated source of energy production; the panels don't move and require little maintenance. By adding a solar tracking system to your solar panels, you are adding moving parts and gears which will require regular maintenance of your solar system and repair or replacement of broken parts.

• The main disadvantage is the investment problem. It has seen that in comparison to the cost and increment in the efficiency, setup and maintenance cost of the tracking system leads. By using the solar tracker the overall efficiency of the system increased by 23-30% whereas the system cost increases by 31-35%  (in most of the cases).

• Also the maintenance and repairing of mechanical and electronic parts of the tracking system requires extra man-power and of course extra investment.

Last of all i'd like to conclude that the use of solar tracker in the solar PV installtation is not that much important. We can save this money and put it on utilising the Maximum Power Point Tracking which yields more output from the solar array than the tracker system.

Image courtesy: http://www.rimlifegreentech.com/



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MPPT based (Perturb & Observe) Solar Charge controller:: Paper Work

Maximum power point tracking (MPPT) based solar charger/charge controller plays a vital role in increasing the overall efficiency of solar PV based system. Implementing a MPPT algorithm in charge controller of a solar PV system is necessary because the current-voltage characteristics of solar PV arrays is non-linear where at a particular point the power output is maximum. So to extract the maximum power from the solar PV system, implementation of MPPT algorithm is must. Maximum Power Point tracking can be done in a few different methodology; they are i) Perturb and Observe (P & O) Method,
ii) Incremental Conductance (INC) Method and iii) Constant Voltage Method. In this paper, the details of Perturb & Observe (P & O) method algorithm and designing and implementing of the algorithm in a charge controller of a Solar PV system (applicable for both grid-tie and stand-alone system) has been presented.

Because of the limited function of this post editor I have to post the the original document of my work here.
Please read the document provided here and give your valuable feedback.



I'm providing the flowchart and block diagram that i've made in the above paper for better and clear view.

Algorithm



Block Diagram

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