Mechanical Engineering BlogA Complete Online Guide For Every Mechanical Engineers

Polymer electrolyte membrane (PEM) fuel cells—also called proton exchange membrane fuel cells—deliver high-power density and offer the advantages of low weight and volume, compared with other fuel cells. PEM fuel cells use a solid polymer as an electrolyte and porous carbon electrodes containing a platinum catalyst. They need only hydrogen, oxygen from the air, and water to operate and do not require corrosive fluids like some fuel cells. They are typically fueled with pure hydrogen supplied from storage tanks or on-board reformers.

PEM Technology:

Polymer electrolyte membrane fuel cells operate at relatively low temperatures, around 80°C (176°F). Low-temperature operation allows them to start quickly (less warm-up time) and results in less wear on system components, resulting in better durability. However, it requires that a noble-metal catalyst (typically platinum) be used to separate the hydrogen’s electrons and protons, adding to system cost. The platinum catalyst is also extremely sensitive to CO poisoning, making it necessary to employ an additional reactor to reduce CO in the fuel gas if the hydrogen is derived from an alcohol or hydrocarbon fuel. This also adds cost. Developers are currently exploring platinum/ruthenium catalysts that are more resistant to CO.

PEM Fuel Cell Applications:

PEM fuel cells are used primarily for transportation applications and some stationary applications. Due to their fast startup time, low sensitivity to orientation, and favorable power-to-weight ratio, PEM fuel cells are particularly suitable for use in passenger vehicles, such as cars and buses.

Disadvantages of Fuel Cell:

A significant barrier to using these fuel cells in vehicles is hydrogen storage. Most fuel cell vehicles (FCVs) powered by pure hydrogen must store the hydrogen on-board as a compressed gas in pressurized tanks. Due to the low-energy density of hydrogen, it is difficult to store enough hydrogen on-board to allow vehicles to travel the same distance as gasoline-powered vehicles before refueling, typically 300–400 miles. Higher-density liquid fuels, such as methanol, ethanol, natural gas, liquefied petroleum gas, and gasoline, can be used for fuel, but the vehicles must have an on-board fuel processor to reform the methanol to hydrogen. This requirement increases costs and maintenance. The reformer also releases carbon dioxide (a greenhouse gas), though less than that emitted from current gasoline-powered engines.

The Wind up battery is the endless independent source of power. It is the only tool you will need to charge your mobile phone batteries, notebook batteries, GPS or any other modern gadget which is in this information-packed world essential life companion. The use of wind up battery charger is easy and being that it is totally portable and independent power supply, it is a valuable part of accessory of every trekker’s, backpacker’s, traveler’s adventures journey. It is also an essential back up power supply for any critical emergency events when there is no power supply available nearby.

How does it work?

The wind up battery mechanism uses internal generator, which is usually hand-powered by spinning the handle on the device. The hand motion, in which AC alternator is driven by a crank converts human mechanical energy and generates the electrical power, by spinning magnets past a coil of wire, which is stored in battery. To charge the device, utilizing the wind up mechanism the hand crank needs to be pulled out of the folded position, and spun in clockwise/counterclockwise direction. After some time of cranking, when the device is charged the handle is folded into position and the device is available to use.

There are also foot powered wind up battery devices, which generate power and self charge by human energy through step action. These are able to jump-start a boat or automobile battery, and power a wide array of instruments and accessories and present a valuable and versatile tool for power supply.

The Devices using wind up mechanism

There are several devices on market which utilize the wind up mechanism. It can be used as a wind up battery charger, wind up flashlight, wind up radio, wind up clock, mp3 player, or a larger electricity supply unit. Usually there are hand cranks folded into the devices, which can be pulled out when needed. The wind up devices are a great way to promote environmentally clean green energy source as the power is derived through windup mechanism which efficiently harvests the human energy and converts it to electricity.

If you are an environmentally conscious consumer who likes to travel and have a power charger available for his electric devices and an emergency power supply then the wind up battery is the device to look for.