Light Emitting Diodes (LED) for Aqueous Light Bleaching of Paper

High performance daylight LED lamps are compared with HID lamps for light bleaching of paper. The LED can be placed in closer proximity to the object than the HID lamps, causing a significantly increased, uniform light exposure. Two commercial LED systems with 4000 K and 6500 K colour temperature were installed in a convertible test device with a polypropylene tray in default exposure distance of 10 cm and 20 cm. A HID lamp in 60 cm and 120 cm distance served as a reference. Samples of two naturally aged rag papers were bleached with both LED systems and with the HID while immersed in water. All three light sources increased brightness (CIELAB L*), though the LEDs with 4000 K colour temperature were most effective. They had no negative effect on the molar mass and the cellulose carbonyl group content while LEDs with 6500 K colour temperature caused molar mass decrease and carbonyl group increase. LEDs of a 4000 K or similar colour temperature are a promising option for improved light bleaching of paper, reducing the treatment and aqueous exposure time and eliminating UV radiation.

Roadway Lighting Retrofit: Environmental and Economic Impact of Greenhouse Gases Footprint Reduction

Roadway lighting retrofit is a process continuously developed in urban environments due to both installation aging and technical upgrades. The spectacular example is replacing the high intensity discharge (HID) lamps, usually high pressure sodium (HPS) ones, with the sources based on light-emitting diodes (LED). The main focus in the related research was put on energy efficiency of installations and corresponding financial benefits. In this work, we extend those considerations analyzing how lighting optimization impacts greenhouse gas (GHG) emission reduction and what are the resultant financial benefits expressed in terms of emission allowances prices. Our goal is twofold: (i) obtaining a quantitative assessment of how a GHG footprint depends on a technological scope of modernization of a city HPS-based lighting system; and (ii) showing that the costs of such a modernization can be decreased by up to 10% thanks to a lowered CO 2 emission volume. Moreover, we identify retrofit patterns yielding the most substantial environmental impact.

Light Flicker Frequencies in the HID lamps

In order to reduce the electric consumption for high intensity discharge lamps (HID), the use of high frequencies electronic ballasts represents both a solution and many advantages such as, the decrease in the congestion, low costs and weak losses, approximately 10%. However it is not regarded as perfectly reliable, this is due in a great part to the appearance of Acoustic Resonances inside the arc tube which can result in low frequency light flicker and even lamp destruction. Experimentally we used a HID lamp of 50 W and we determined, light flicker frequencies and the arc motion frequencies using a photodiode which detects the light intensity fluctuation and a camera to record the arc motion. The experiment was done in the Department of Mechanical Engineering and Production, Hamburg University of Applied Sciences.

Experimental Measurement of Arc Motion and Light Flicker Frequencies in the HID Lamps

<p>In order to reduce the electric consumption for high intensity discharge lamps, the use of high frequencies electronic ballasts represents both a solution and many advantages such as the decrease in the congestion and low costs. However, high frequency operation is not regarded as perfectly reliable due to the appearance of acoustic resonances inside the arc tube, which can result in low frequency light flicker and even lamp destruction. Here we experimentally determined light flicker frequencies using a photodiode which detects the light intensity fluctuation for a high intensity discharge lamp of 50W. Additionally, the arc motion frequencies<strong> </strong>are determined with the aid of a camera. The results obtained are compared with those of a lamp of the same type but with different power (35W).</p>