Music Several weeks ago, I attended the Henri Sack Memorial Lecture. This lecture, called Photovoltaics Power Source for the Future was given by Professor Martin A Green from the Australian Centre for Advanced Photovoltaics and University of New South Wales. Professor Green told us about photovoltaics, and why they are likely to be an important source of energy in the future. Photovoltaic cells are made of silicon crystals. They were initially developed during the 40's, but were greatly improved during the 50's. In the 60's people started using them in spacecraft. Photovoltaics underwent further improvements during the 70's. They began.
Having a textured surface, so there would be less reflection of light off of them. During the 80's the first 20 efficiency cell was developed. Now, there are cells that have 25 efficiency. There are currently 1 million homes in Australia that have solar power. Most residential solar panels have about 16 efficiency. In the past, thin layer solar cells were more cost effective. The layer of photovoltaic could be applied to any substrate, and they looked nice. The silicon wafer type of solar cell has had many improvements in the past few years. The cost for manufacturing them.
Is decreasing due to new technologies and techniques. Photovoltaics are a promising power source is that not only a clean energy source, but the cost of them is decreasing, while the cost of other types of energy is increasing. Techniques for making more pure silicon cells are improving, making the efficiency likely to improve a lot in the near future. One idea to make solar cells more efficient is to have multilayer cells. In these, each layer would absorb photons at a different energy level. This technology would greatly increase how much energy photovoltaics can give us.
Another useful thing about photovoltaics is that they produce the most energy during peak demand times, during the day when the sun is out. Unlike other power sources that need to store energy during the night to provide extra energy during the day, photovoltaics produce more at the right times, so less would need to be stored. This lecture gave me more information about a topic I was already somewhat interested in. It convinced me that solar energy is going to be very, if not the most important source of energy in our future. Overall, I learned a lot, and this was definitely an adventure.
Forces acting on an individual wind turbine blade section
We said now in BEM theory, we're actually looking at individual blades. That is important. What's happening at an individual blade section or a strip that cut out of the blade Wind is coming from the left from left to right hitting a turbine blade. I cut out a section, wind is coming from the left. There's an airfoil. Look at your picture, the wind is hitting the lower surface or the upper surface of the airfoil Lower. What does a propeller do Upper. What would you have expected Lower or upper If I had asked you before class.
Lower I found that weird when I saw that the first time, that the wind hits the lower surface. Because you would expect, like for a propeller, that it would hit the upper surface. Well, there is a fundamental difference. The propeller puts energy into the flow and what the propeller does, it sort of tries to swim through the air and push the aircraft forward with it. So the lift vector is going to be directed forward. For a wind turbine, we want to do the opposite. We don't want to put energy in, we want to get energy out.
And sell it to the electrical grid and make money with it. The forces along a section of a wind turbine blade, they look differently. In the end, what you want to do is you want to generate torque. Because that torque times the rotor speed, capitol Omega, is going to produce the power to the generator that you can sell. The rotor thrust is a side effect associated with it. You can do anything with the rotor thrust. The rotor thrust is just annoying because it's a large force that's acting on top of an 80 meter.
Tower and creating a humongous bending moment to the foundation. So it's a side effect that you have to live with. And if you look at that figure well to call it a thrust is a little bit of a stretch because it's acting in the air speed direction. For a propeller the thrust would be defined opposite , because that's what pulls you forward. For a wind turbine, the thrust is actually a drag. But we call it a thrust. Let's keep that in mind. But these torque what we want and thrust what we have to live with unfortunately.
Tankless Hot Water Heater Day 132 The Garden Home Challenge With P. Allen Smith
You know, the only thing better than a good, hot shower is a good, hot shower that's energy efficient. Let me show you what we're doing here. They say an ecofriendly house can't be built in 150 days for $150,000, and I say it can. I'm Allen Smith, join me as I push the limits with time, budget and creativity with the Garden Home Challenge, exclusively on eHow Home. So guess what this is. Yeah, I know it doesn't look like a hot water heater, but it is. It's not the conventional tank type, this is tankless. And the reason we.
Have it is because it really cuts down on the cost of energy. Remember, we're all about saving energy with this house. Now I've been familiar with these tankless hot water heaters for some time I've used them on several projects. But I first learned about them from some friends in Europe. This is what they use this is the standard in Europe because of the energy efficiency. The tankless, it doesn't really run, you know, unless it's you call for the water. You know, there's not a it don't always kick on and off,.
And always has to heat that water. It only heats the water when you actually turn the faucet on. What it does, it just basically doesn't run when you're not home. It's not always heating and cool you know, water don't have to heat up and cool off heat up, cool off. It just runs when you need it. You see, the good thing about having a hot water heater that goes on vacation when you go on vacation is it's not charging anything to your account while it's on vacation or you're on vacation. Admittedly, you're gonna.
Spend more money on a tankless hot water heater, initially, but it will begin to pay for itself over time, to the tune of about 25 to 30 percent a year savings in what you would normally spend on energy to heat the water that you use in your home. It's a gas burning unit, so you have to you can't it has to vent to the exterior. And what we're doing is we're coming out of the side of the wall here, so you really won't see it it really won't.
Be a retina irritant. They make models that actually come out on the exterior that vent directly out to the atmosphere without the venting itself. You know, electric heaters don't have a vent, because they don't have any fuel to burn. They make them indoor or outdoor model on these tankless heaters. Either way, you're gonna have to have some of the fundamental things that you're gonna need for one of the conventional tank hot water heaters You're gonna need a source of electricity to ignite the fuel to heat the water. And.
What Is A Stock Market Crash
Market regulators are accusing a British national of almost singlehandedly causing a Flash Crash to American stock markets in 2010. During the incident, the Dow Jones Industrial Average dropped about 9, and lost more than $1 trillion dollars in minutes. Fortunately, stocks rebounded relatively fast after the shock, but we wanted to know, what does it take to crash a stock market Well, there have been countless financial crashes throughout history. They even go back to the 1600s when modern stock exchanges were first evolving within the European trade economies. A crash represents a steep, sudden decline in the value of market prices, and.
They can often lead to an economic depression. The most devastating crashes are usually the result of an overlyinflated market, also known as a bubble. In short, the value of a stock is dependent on what people think it will be worth in the future. When the economy is good, or there are other motivating factors, investors expect their stocks to rise in price, which in turn does increase their value. Investment bubbles occur when prices of market shares are driven upwards past their real value. According to some market theorists, a bubble is encouraged by a herd mentality, where.
People first jump on the bandwagon of a profitable stock, and then, when the bubble bursts, they engage in panicselling. The most famous example of this was during the 1929 American Stock Market Crash. In the years after World War I, optimism in the economy inspired many to take on risky loans, and invest in stocks. But when the economy slowed down, the public began to doubt the market's longevity, and started selling their shares at first slowly, and then in droves. Market prices went into freefall, and with no failsafe rules, the.
Market inevitably crashed. Stock markets can also be spooked into a decline or a crash following catastrophic events. For example, San Francisco's massive 1906 earthquake is thought to have played an integral role in the financial panic of 1907. During that time, the market sank to about 50 of the previous year's valuation. Additionally, In 2001, after the September 11th terrorist attacks, the stock markets were closed for almost a week. In the first five days back, the markets faced a loss of about $1.4 trillion dollars. The digital era has also introduced new threats to the stock market in the form of high.
Frequency trading. HFT is when thousands of trades are carried out by computers in fractions of a second. The swiftness of computer programs at buying and selling puts traditional traders at a disadvantage. Also, HFT creates potential volatility in the stock market. Computer programs that are designed to automatically respond to price points can trigger mass selling before anyone has time to react. This was said to have contributed to the 2010 Flash Crash, after a large enough downtick in stocks caused many HFT programs to further withdraw, leading to a drastic crash.
After that event, government regulators imposed new laws, called circuit breakers, which temporarily pause trading if a stock falls by a certain percentage, usually 10 or more, within a short time. These safeguards give traders breathing room to reexamine their options instead of panicking and selling everything before the stock bottoms out. The Securities and Exchange Commission works hard to regulate the wild swings of the stock market. But for the modern era, stock markets remains more volatile, and susceptible to crashes than one might ever think. Investing is a pretty risky thing to do, but sometimes big risks can have even bigger rewards.
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