Archive for category Engineering
Transparent solar cells
Posted by bumscientist in Engineering, Science on December 23, 2009
Can a solar cell be transparent?
The answer is yes, but you wouldn’t particularly want to unless you have some application like solar windows. The sun is a black body radiator at 5777 K. For a solar to be transparent it has to allow the visible spectrum (380 to 750 nm) through, but absorb the rest.
If we look at where the energy from the sun lies, you get
- 10% in the short wavelength
- 44% in the visible
- 46% in the long wavelength
So there is about just as much energy in the infrared and longer as there is in the visible, but the peak energy is in the visible. The way inorganic solar cells work is that they start absorbing at a certain wavelength and lower wavelengths with less efficiency.
MIT is working on solar cells that can be integrated into windows. Here’s a treehugger article.
One thing that decreases long wavelength energy production is that molecules in the atmosphere absorb certain frequencies as vibrational modes.
Engineering’s Grand Challenges reduced
Posted by bumscientist in Engineering on December 12, 2009
- Make solar energy economical
- Advance personalized learning
- Engineer the tools of scientific discovery
This is entirely manageable. All it says is to make solar energy economical, which is only a matter of time. I should just write a report on solar technologies.
Prioritizing Projects
Posted by bumscientist in Engineering, Fun, Ramblings on December 12, 2009
Currently I have 4 projects listed and open, but it’s time to prioritize them
- spacepirate game – long term, needs a lot of work, a fun project
- Engineering’s Challenge – long term, needs a lot of work and decisions, prelude to graduating
- icc profile – immediate use to calibrate scanner
- audio power amplifier – a year or two out in time scale, after I buy speakers, no immediate use, should be fairly quick to design and build, lots of attention to detail possible. I could sell these out the back of my car.
Prioritizing them and assigning tasks to complete before moving on to next step, I get
- Engineering’s Challenge, par down choices some more
- icc profile, finish project
- audio power amplifier, design circuits
- space pirate game, the movement AI working
Audio Amplifier Project
Posted by bumscientist in Engineering on December 11, 2009
I saw the HTD Level 3 bookshelf speakers on Tekzilla and I want. The only problem is that I need an amplifier to drive it. HTD also sells the A-2050 Stereo Amplfier, a 50 Wpc at 8 Ohms power amplifier. The speakers are 8 Ohms and rated to a max of 120 W, but I doubt I will drive them that hard. I have the Logitech Z-2300 2.1 that have 40 W satellites and I never run them at full volume. I keep them rather low. When you have good speakers, you don’t need to run them loud. I actually did make an audio amplifier to drive an electromagnetic for research, so I doubt it would be that hard to make another one to drive my speakers. I used the chip they used for the gainclone. The only difference between my home audio amplifier and magnetic field driver is that I won’t have a power supply that I can dial in to a DC voltage. I will have to put a transformer in there encased in the box.
For 50 Watts at 8 Ohms, P = I*V, V = I*R, P = V^2/R, so V = 20 volts and I = 2.5 amps, which is a lot of current. I’m going to have to supply at least a consistent +-20 volts
Things in need to consider
- Power Supply – need to think of safe, efficient way
- Input plugs – which connectors do I use?
- Switches and knobs – on/off, volume, mute, others?
- Case – metal or not
- Amplifier circuit – probably use the spec sheet circuit
- Heatsinks – important
- Output plugs – which connectors?
I wonder if I can make it for under $200.
Octave and MATLAB
Posted by bumscientist in Computing, Engineering on December 4, 2009
Since I can’t afford MATLAB for my own machine. I’m making an effort to make my code OCTAVE-compatible, so I will be able to reuse the code on my own computer. This will involve creating some toolboxes I bet; along with cataloging the differences.
Differences
- fopen.m, ‘ieee-le.l64′ does not exist in ocatve as an arch, use ‘ieee-le’ instead.
- daspect.m does not exist, make a function that does a set(gca,’dataaspectratio’,x);
Engineering’s Challenges: Fusion I
Posted by bumscientist in Engineering on November 18, 2009
Provide energy from fusion
So the first thing one should understand is the fusion reaction. Then go into the ways to initiate a fusion reaction.
From my plasma physics class, I remember that tritium has a higher cross-section for reaction, so it is very desirable for fusion. The catch that tritium is rare. Hydrogen has a proton, deuterium has a proton and a neutron, tritium has a proton and two neutrons. Deuterium can be obtained from heavy water. Water molecules with deuterium instead of hydrogen are heavier, so those water molecules tend to sink in relation to normal water. About 0.0115 % of hydrogen is deuterium, so that’s about 1 in 8,700. That’s not actually too bad if you want to use deuterium.
It has been more than a day since my last engineering’s challenge post. I defintely need to whittle down the challenges to something manageable.
Working a Room
Posted by bumscientist in Engineering, Fun on November 16, 2009
I’m not what you would call the most social person in existence. When placed in a situation where anything social may occur, I tend to avoid it as much as possible. This hasn’t been a good thing, but I’ve lived with it and survived. Right now I’m wondering how much longer I can survive without being social. I’m not referring to the social skills required to be a pickup artist with the ladies, but the social skills required to be a successful entrepreneur. I read this post on the Stanford BASES website about what they don’t teach you at Stanford business school. I’ve taken business classes and interacted with business people. They are a different beast. So far I’ve thought I could survive by having a good idea and technical skills even though my professor pointed out that sales people are needed to make a company successful. I think his point is finally sinking in. I’m a believer now.
Better late than never. Now I should probably make an attempt to go to all the mixers on campus and various other social functions. I remember the time my boss’s boss’s boss’s administrative assistant forced me to attend a company social function.
Engineering’s Grand Challenge: Solar I
Posted by bumscientist in Engineering on November 11, 2009
Make solar energy economical
By economical, it means it just has to be cheaper than the alternatives.
By energy, it means mainly electrical energy. You could use solar energy to heat water, run machines, pumps, etc.
There are two kinds of solar generation that I can think of.
Solar Thermal – uses mirrors to focus incoming solar radiation to heat salts or a sterling engine.
Photovoltaic – uses photons pass energy to electrons.
I should probably do some thermodynamics calculation to figure out how efficient these processes can be since the sun is at some temperature and things on earth are at some temperature. Let’s see Carnot engine efficiency is 1-Tc/Th, which means maximum efficiency is about 94.8%. Do Carnot engines have anything to do with solar efficiency? I need to think about how these two heat reservoirare attached. Actually it is probably applicable, since heat from the sun, gets put through a system to do work and the heat has to dump to the earth eventually.
My background is more applicable to photovoltaics than solar thermal, but I should at least find some figures for solar thermal. Photovoltaics also have wider applications, because they can be put on a variety of places and have probably the most game changing results.
To Do list: Find solar thermal figures. I need to learn to be a better thief, because I went to a talk where someone outlined the maximum efficiency of a solar cell.
Next Time: Go over different types of photovoltaic technologies.
Efficiency
Posted by bumscientist in Engineering, Science on November 11, 2009
“I’ve always been a bit of an energy efficiency nut.
I’ve made it my mission to cut the utility bills at every home we’ve owned. Long before I learned about the risks of climate change, I was fanatical about energy efficiency because I’m cheap.” – Steven Chu, from a facebook post.
I think we can put a band-aid over some of the problems with energy and water by conserving and increasing efficiency. Things are inefficient, because people are lazy. People don’t conserve, because it doesn’t cost them enough to conserve. When gasoline increased in price near $5, people are changing their habits. The problem is that it may be too late for the free market to take its course, before people can change their habits. I previously wrote that sometimes making the sandbox smaller can lead to more creative ideas. Making things efficient is like a game along the lines of tuning your car for better performance. I think the #1 use for energy was heating, so properly insulating your home will reduce energy usage dramatically.
Maybe I’ll go over one of the 14 engineering challenges each day and try to advance my knowledge of the area bit by bit. Then I’ll reduce it to 7, so I can do one a day. Then continue to reduce the challenges until I find one that I wish to pursue after I graduate.