New material could up efficiency of concentrated solar power

Above a certain temperature, it becomes possible to replace the steam with supercritical carbon dioxide. This works more efficiently, potentially providing a boost of more than 20 percent, but it requires temperatures in excess of 1,000K. That makes things a bit more challenging, given that many metals will melt at such temperatures; others will react with carbon dioxide under these conditions. Finding a material that could work involves balancing a lot of factors, including heat and chemical resistance, ea

Source: New material could up efficiency of concentrated solar power | Ars Technica

Matchstick-sized sensor can record your private chats

Conventional microphones work when sound waves make a diaphragm move, creating an electrical signal. Microflown’s sensor has no moving parts. It consists of two parallel platinum strips, each just 200 nanometres deep, that are heated to 200 °C. Air molecules flowing across the strips cause temperature differences between the pair. Microflown’s software counts the air molecules that pass through the gap between the strips to gauge sound intensity: the more air molecules in a sound wave, the louder the sound. At the same time, it analyses the temperature change in the strips to work out the movement of the air and calculate the coordinates of whatever generated the sound.

via Matchstick-sized sensor can record your private chats – 26 September 2013 – New Scientist.

Acoustic Vector Sensors

In acoustics this movement of air is called particle velocity. The Microflown sensor is based upon MEMS technology, and uses the temperature difference in the corss section of two extremely sensitivy platinum wires that are heated up to 200°C in order to determine Acoustic Particle Velocity. When air flows across the wires, the first wire cools down a little and due to heat transfer the air picks up some heat. Hence, the second wire is cooled down with the heated air and cools down less than the first wire. A temperature difference occurs in the wires, which alters their electrical resistance. This generates a voltage difference that is proportional to the Particle velocity and the effect is directional: when the direction of the airflow reverses, the temperature difference will reverse too.

via Overview – Acoustic Vector Sensors – Microflown AVISA.

World’s largest OTEC power plant planned for China

OTEC uses the natural difference in temperatures between the cool deep water and warm surface water to produce electricity. There are different cycle types of OTEC systems, but the prototype plant is likely to be a closed-cycle system. This sees warm surface seawater pumped through a heat exchanger to vaporize a fluid with a low boiling point, such as ammonia. This expanding vapor is used to drive a turbine to generate electricity with cold seawater then used to condense the vapor so it can be recycled through the system.

via World’s largest OTEC power plant planned for China.

How Google Cools Its Armada of Servers

Here’s how the airflow works: The temperature in the data center is maintained at 80 degrees, somewhat warmer than in most data centers. That 80-degree air enters the server, inlet and passes across the components, becoming warmer as it removes the heat. Fans in the rear of the chassis guide the air into an enclosed hot aisle, which reaches 120 degrees as hot air enters from rows of racks on either side. As the hot air rises to the top of the chamber, it passes through the cooling coil and is cooled to room temperature, and then exhausted through the top of the enclosure. The flexible piping connects to the cooling coil at the top of the hot aisle and descends through an opening in the floor and runs under the raised floor.

via How Google Cools Its Armada of Servers » Data Center Knowledge.

Google’s custom servers also have a bare bones look and feel, with components exposed for easy access as they slide in and out of racks. This provides easy access for admins who need to replace components, but also avoids the cost of cosmetic trappings common to OEM servers.