Hello all! This week has been absolutely amazing! I've been going to Intel's energy department in Chandler this week and have had an amazing time! The food court is wonderful: there is Korean barbecue, Indian food, American grill, Italian food, and free coffee and fruits! I am also getting a tour of one of their six solar installments and the Intel product room! I can't wait for these tours and to share my experience with all of you!
My supervisor, Dr. Godart, and I have discovered a significant issue with grid tie inverters (the type of solar inverter mentioned in my last post). As I mentioned, a grid tie inverter, by definition, is intertwined with the grid. This means that when the utility grid shuts down (i.e., power outage, blackout), the inverter shuts off (meaning one cannot use their solar energy). This is due to safety protocols: if an inverter continued to function and provide energy to the house, some might be sent to the grid (like net metering) and shock a line worker sent to fix the problem. A solution to this problem is to add what is called a battery backup system. In this case, a set of rechargeable batteries is connected to the inverter and utility grid. Either the AC from the circuit or from the inverter recharges these batteries as they discharge, so in the case of a power outage, the inverter disconnects from the grid (this is known as anti-islanding protection) and relies on battery power. Furthermore, only priority appliances are powered by these batteries during the blackout.
So what exactly is the problem if we solved the issue with the battery backup system? The problem with the battery backup system is three: it is inefficient, costs more money to buy and maintain, and only powers primary appliances during power outages. This will idealy be a capability of a smart inverter: to allow solar power to be used at full capacity during a blackout and not endangering line workers. I will be asking this among many other questions in my interviews! Too look at the questions I have prepared, please click on the link "Interview Questions" under "Related Links" in the right column. I would strongly appreciate any feedback on the questions I have or suggestions on other questions!
Thanks for stopping by this week and I hope you enjoyed! Next week I will be conducting my interviews with people from Intel, APS, SRP, and Siemens. Fingers crossed all goes well! See you next time!
Signing off,
Kayvon Tadj
Friday, February 26, 2016
Friday, February 19, 2016
Greetings to all my readers,
It has been another week of skimming through different articles and books to fill my brain with inverter, grid, and solar technology. Although this background phase will be the driest of my project, I am thoroughly enjoying every moment of it!
This week I have studied specific types of inverters, rather than just a general power inverter, and analyzed them for their strengths and weaknesses. Of the many that inverters that exist and are used, I will be focused on solar inverters. Although the name suggests that these are the only inverters used for to convert solar energy to AC, there are many other inverters that preform this function; however, soalr inverters are the most popular/useful. In this post, I will be focusing on a specific kind of solar inverters, grid tie inverters (GTI).
The GTI is one of the only, and most efficient, methods of connecting to the power grid. To do so, the GTI synchronizes with the frequencies of the grid using an oscillator and limits its output voltage with that of the grid's voltage. The more advanced GTI's have fixed unity power factors (output voltage and current are perfectly synced). The downside to the modern GTI's is that they are almost too perfect! Shocking, right? The problem with perfectly syncing the voltage with the current is that we get rid of reactive power (the byproduct of current and voltage being out of phase). Usually, we supply the grid with this reactive power; however, by getting rid of it, we now create too much power for the grid to handle at peak times (i.e., noon) and we break our aforementioned limitations. One other downfall to using a grid tie inverter is that it must be connected to the main power grid. In other words, a grid tie inverter cannot be used to convert DC solar energy to AC electrical energy to power an appliance directly; it must first be connected to the grid, which can then power the appliance. This indirect route is less efficient as it provides more time and space for friction losses.
Finally, grid tie inverters, like many, can use different kinds of transformers, or none at all. This differentiation may seem insignificant; however, getting rid of a transformer not only reduces the production cost of an inverter, it also makes the inverter more efficient. Many European countries have taken the first step towards smarter inverters and primarily use transformerless inverters. The U.S.'s reluctance to follow Europe stems from a safety concern: would the lack of a transformer lead to faulty DC energy to leak into the AC side. However, since 2005, the NFPA's NEC has allowed the use of transformerless inverters and regulations have even been amended in order to encourage their use. Hopefully, the U.S.'s reluctance eventually fades as they observe the lack of danger that transformerless inverters pose.
That's it for this week! Next week I will begin working at Intel itself and cannot wait to start my journey! I will also be finishing my background phase of my project and entering phase 2 by the end of the week! See you then and thanks for stopping by!
Signing off,
Kayvon Tadj
Finally, grid tie inverters, like many, can use different kinds of transformers, or none at all. This differentiation may seem insignificant; however, getting rid of a transformer not only reduces the production cost of an inverter, it also makes the inverter more efficient. Many European countries have taken the first step towards smarter inverters and primarily use transformerless inverters. The U.S.'s reluctance to follow Europe stems from a safety concern: would the lack of a transformer lead to faulty DC energy to leak into the AC side. However, since 2005, the NFPA's NEC has allowed the use of transformerless inverters and regulations have even been amended in order to encourage their use. Hopefully, the U.S.'s reluctance eventually fades as they observe the lack of danger that transformerless inverters pose.
That's it for this week! Next week I will begin working at Intel itself and cannot wait to start my journey! I will also be finishing my background phase of my project and entering phase 2 by the end of the week! See you then and thanks for stopping by!
Signing off,
Kayvon Tadj
Tuesday, February 16, 2016
Hello all! I am currently in Phase 1 of my research project, which, consists of me absorbing as much about solar, grid, and inverter technology as possible. My supervisor has provided me with a couple of books: Reinventing Fire and Solar Power Your Home for Dummies. Furthermore, I have pulled sources from slideshare.com, nrel.gov (the National Renewable Energy Lab), smartgrid.gov, and energy.gov (the Department of Energy).
Now that I have began researching, I can give a more detailed description of my research project. As I mentioned, my goal is to come up with a smart inverter for Interl. But what exactly is an inverter? And what makes it smart? An inverter converts direct current (DC) to alternating current (AC). Their most important application, on which I will be focusing, is to solar energy. When a solar panel converts the energy of the sun to electrical energy, it stores that electrical energy in a battery, which is DC. However, the power grid that the outlets are connected to are all AC; so the inverter is the bridge that connects the solar energy captured from the sun to the appliances in your home.
Current inverters fulfill their function of converting energy from DC to AC, but poorly. Many problems that current inverters pose include fluctuating power levels, dirty power, and weather-dependency. These three problems can be intertwined and can lead to serious problems. For example, after a week of changing weather (from cloudy to sunny), the power levels will spike and drop repeatedly, providing dirty power, which includes low power, power surges, changes in frequencies, etc., to the system. In the case of a hospital, for example, this dirty power can corrupt all the machines it is funneled to. A smart inverter, among other capabilities, would stabilize the power, voltage, and frequency levels while being more efficiently converting energy.
My next post (February 19) will further the background on inverters, grids, and solar energy that I uncover in the next few day. Next week, I will be going to Intel for 2 weeks every day in order to work more closely with other solar engineers. Furthermore, I will be finishing Phase 1 of 4 next week and beginning the more interesting, hands-on research! As I mentioned, I will be interviewing workers from the DOE, Intel, SRP, and APS! I will keep you informed on how each interview goes and what I learn. Thanks for reading!
Signing off,
Kayvon Tadj
Now that I have began researching, I can give a more detailed description of my research project. As I mentioned, my goal is to come up with a smart inverter for Interl. But what exactly is an inverter? And what makes it smart? An inverter converts direct current (DC) to alternating current (AC). Their most important application, on which I will be focusing, is to solar energy. When a solar panel converts the energy of the sun to electrical energy, it stores that electrical energy in a battery, which is DC. However, the power grid that the outlets are connected to are all AC; so the inverter is the bridge that connects the solar energy captured from the sun to the appliances in your home.
Current inverters fulfill their function of converting energy from DC to AC, but poorly. Many problems that current inverters pose include fluctuating power levels, dirty power, and weather-dependency. These three problems can be intertwined and can lead to serious problems. For example, after a week of changing weather (from cloudy to sunny), the power levels will spike and drop repeatedly, providing dirty power, which includes low power, power surges, changes in frequencies, etc., to the system. In the case of a hospital, for example, this dirty power can corrupt all the machines it is funneled to. A smart inverter, among other capabilities, would stabilize the power, voltage, and frequency levels while being more efficiently converting energy.
My next post (February 19) will further the background on inverters, grids, and solar energy that I uncover in the next few day. Next week, I will be going to Intel for 2 weeks every day in order to work more closely with other solar engineers. Furthermore, I will be finishing Phase 1 of 4 next week and beginning the more interesting, hands-on research! As I mentioned, I will be interviewing workers from the DOE, Intel, SRP, and APS! I will keep you informed on how each interview goes and what I learn. Thanks for reading!
Signing off,
Kayvon Tadj
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