alternative, dubai, energy, lighting, pavegen

Walk the watts

people on a busy crossroads in shibuya, tokyo, japan - not model released

Hundreds of thousands of footfalls = megawatts of energy

People-generated energy, and this is not a plot of Matrix franchise. in 2009 Lawrence Kemball-Cook, a graduate of Loughborough University, UK, has filed a patent and started up a company Pavegen. The company makes a 600mm x 450 mm tile, its surface of recycled tires. A typical footfall compresses the polymer surface by 5 mm and this motion generates electricity. According to the company’s data, each step could create up to 7W of 12V DC. Technology behind this invention is a guarded secret, but a quick sniff around the web hints it is of the similar nature to piezoelectric effect and induction.

Tiles are waterproof, certified according to British and EU electrical and safety standards. Generated electricity is then stored in a battery, and is activated at required intervals to light up a street, alley or a park. Pavegen stipulates that unlike solar and wind sources, there is no limitation to use a field of tiles within a city limits, and therefore efficiency of an installation is way optimal.

Installing a Pavegen field

Installing a Pavegen field

Paving a busy street in a bustling city is great, but what about the Middle East? Could this technology find its way here? 160 million legs marching through Dubai Mall yearly answer: yes, it could!

Images courtesy of http://www.freeimageslive.co.uk and Pavegen

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health, lighting, wearables, wellbeing

Portable Light to Read Your Heart

Fitbit Surge flashes its diode to read your heart

Fitbit Surge flashes its diode to read your heart

On our blog we often talk about things around light, or things light can be and can do. Here is another example of what a light can do: measure your blood pressure. Two LED flicker while you wear it on your wrist and an optic sensor “reads” how the blood pulsates.

This technology is known as photoplethysmography. Blood absorbs light and fluctuations of light correlate to heart rate. LED emits light in AC and DC current (alternating current flickers, and direct gives steady light). The waveform of the latter corresponds to the detected transmitted or reflected optical signal from the tissue. DC component also changes slowly with respiration. The AC component shows changes in the blood volume during the phases phases of the cardiac cycle; the fundamental frequency of the AC component depends on the heart rate and is superimposed onto the DC component.

Graphics courtesy of Toshiyo Tamura, Yuka Maeda, Masaki Sekine and Masaki Yoshida

If you ever used such device you might have mused about the choice of green color LEDs. The answer lies in the spectrum or wavelengths (to be even more scientific, between 500 and 600 nm). Green or green-yellow light is much better reflected and detected by a sensor when blood pulsates through skin, and gives a more accurate result compared to infra-red.

From purely medical use, these sensors found their way to popular wearables, and many a runner already tear off their chest-strapped monitors. Devices like my Fitbit combine BPM with distance and speed, sleep monitor and all at a convenience of a wrist-band.

Reference: Paper on Wearable Photoplethysmographic Sensors by Toshiyo Tamura, Yuka Maeda, Masaki Sekine and Masaki Yoshida

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