How much energy that we can enjoy from sun

How much energy that sun can give us as a free gift? I stumbled across a term, solar constant (=1361 Watt/m^2), which means the maximum energy density that sun can give us is 1361 Watt/m^2.  This term is associated with the energy that our rooftop solar panels can generate and probably any engineer that learned Planck's radiation law before should know how to calculate this 1361 W/m^2.   Since sun surface temperature can reach 5800K, it will generate 2.04e7 W/m^2/sr energy flux density.   The subtended angle from earth to sun is 0.53 deg.  Therefore, maximum power density that sun can give us is 2.04e7 *3.14 *sin(0.53/2)^2 = 1370 Watt/m^2 (God never allows sun to give us more energy density than this solar constant!)  However, at average 5500K sun surface temperature and consumer-grade silicon solar panel can absorb only 0.4-0.8 um wavelength, sun only emits 7.4e6 W/m^2/sr to silicon solar panels.    This implies that solar panel can best absorb 7.4e6 *3.14 *sin(0.53/2)^2 = 500 W/m^2.   At 20% efficiency, no wonder most of the rooftop solar panel can only generate 100 Watt/m^2 (i.e., 7% of solar constant).  That means for 10m^2 rooftop solar panel, it can only generate 1 kWh electricity per hour.

Solar-thermal renewable energy with 28,000 sun-equivalent brightness

Recent article in TIME has covered Ivanph, a solar-thermal project in California desert which can generate 14 億度/yr (臺灣的總電力裝置容量為每年2800億度, 核四每年240億度). It sprawls over 16 平方公里 with three gigantic solar towers, each with 150m height and 28,000 sun-equivalent brightness. In addition to 3 towers, it has 173,000 constantly adjustable mirrors, each with the size of garage door. Unlike solar-panels on the rooftop or wind-power farms, solar-thermal is a reliable renewable energy (if located in the year-round sun-drenched desert!). However, with price of solar-panels plummeting in recent years due to a glut of solar panels made in China, solar-thermal energy is still not as cost-effective as solar-panel energy, let alone the coal-fired power plant.

office building with robots and nothing but robots?

Picture this, 10 years from now, the office building is staffed only with security guards and a whole bunch of mobile autonomous robots, each with 21" LCD display that constantly shows your face and what you are doing at home. Everyone can work at home since there is always one robot incarnation in the office that represents you. You can navigate this incarnated robot to any room in the office building to join the meeting, to make presentation or even just to have casual watercooler conversation when you are physically at home. This is actually available now but way too expensive ($25k/yr to rent a robot). It's likely that it will be very popular in the years to come.

iRobot and Cisco Team Up to Create Ava 500 Telepresence Robot - IEEE Spectrum

spectrum.ieee.org

This robot knows how to drive itself around your office

Powerful boss may face comeuppance?

Powerful people are always undone by hubris? Probably it is true according to the study from the article in Economist. If you feel your boss is too arrogant or condescending, according to the study, he or she may face comeuppance. Former Intel's famous CEO, Andy Grove, had a sobering dictum: only the paranoid survive.

Who’s behind me?

www.economist.com

Everyone wants cheap U.S. natural gas

Every country wants to have U.S. cheap shale natural gas which is only 30% of Japan's cost (1 million BTU on the following chart is equal to 293度電) because of its advanced fracking technology. Taiwan's natural gas comprises 11.6% of total energy consumption and imported 12.8M MT (million-tonne) natural gas last year. U.S. has already exported 33.5M MT/yr natural gas to Mexico and Canada through pipes. Now US is building facilities to liquefy natural gas to -162C for export purpose. Its total export capacity can reach 27.4M MT/yr in the next few years to Japan, U.K, Spain, Korea and India. Though A.I.T. has expressed willingness to sell Taiwan U.S. natural gas, it is hard for me to imagine Taiwan can get more than 5% of its 27.4M MT/yr.

The Battle Over Who Gets U.S. Natural Gas

www.businessweek.com

Gold rush for adaptive-learning market?

The latest issue of TIME magazine has an article, "A Is For Adaptive", which may give a hint for any up-and-coming would-be entrepreneurs to jump into this gold rush for the global $4.6 trillion education market. It has been well-known that one-size-fits-all curriculum is only a compromise in the educational system. Adaptive learning materials for each student is only a dream for many centuries until recently when digital technology is finally mature enough to make it possible. Knewton, a start-up targeting adaptive learning has attracted $33M from investors and has already proven impressive differences in students' learning from its products. Many companies are jumping on this adaptive-learning bandwagon. Since adaptive-learning may have nuanced cultural difference, it may be up for grabs for aspiring programmers and educators to foray into this promising (and lucrative) virgin market in Taiwan.

A Is For Adaptive

No more alpha male

Women accounts for 40.4% of the American households as the sole or major breadwinners nowadays compared with 10.8% more than 50 years ago. And women earn more than men in 15% of all American households. Actually, women college enrollments are 25% more than men's in the U.S. nowadays. The mindset of "alpha male" is guaranteed to subside gradually and steadily.