All posts by Alex Martin

Renewable Energy – Fuel Cells

A fuel cell is an energy conversion device that uses an electrochemical process to convert hydrogen into electricity without combustion. It produces electricity with a conversion efficiency of up to 50 per cent. In a combined heat and power (CHP) installation, an overall efficiency of up to 80 per cent may be possible by utilising the heat that is also produced as a by-product of this process.

Fuel Cells produce electricity and heat by combining hydrogen and oxygen in an electrochemical process. They are similar to batteries but the fuel and oxidant are stored externally, enabling them to continue operating as long as the chemicals are supplied. In most applications the oxygen is taken directly from air, so that only the fuel has to be stored. The ideal fuel for fuel cells is hydrogen, but other hydrogen containing fuels (such as natural gas or petrol) may be used if they are passed through a reformer, which converts them into a hydrogen rich gas.

A fuel cell contains an anode and a cathode insulated by an electrolyte situated between them. Hydrogen is supplied to the anode while oxygen is supplied to the cathode. The two gases try to join, but because of the electrolyte, the hydrogen atom splits into a proton and an electron. The proton passes freely through the electrolyte. The electron takes a different route, creating an electric current before recombining with the hydrogen and oxygen, creating a molecule of water. This chemical process generates electrical and thermal energy but produces pure water as a by-product.

There are many different types of fuel-cell technology, with different characteristics such as power output and operating temperature. Each fuel-cell technology will only be suitable for certain types of application.

A fuel-cell system utilising hydrogen from any source including hydrocarbon fuels, such as natural gas and methanol. However, emissions from this system can be lower than the cleanest method of normal fossil fuel combustion.

An Example of Fuel Cell Technology

The first fuel-cell combined heat and power (CHP) system in the UK was installed on behalf of Woking Borough Council at the Woking Park leisure complex by BTU (Heating). As part of a ‘private wire’ district energy system (a separate network that allows electricity from the system to be sold directly to those facilities or buildings connected to it – rather than selling the electricity into the national grid), the fuel-cell CHP system provides the leisure complex with heat for the swimming pool water systems, high-grade heat for the heating systems, chilled water for the cooling and air conditioning systems via heat-fired absorption chilling, electricity and 100 per cent pure water via a water recovery system.

Not only does the combined system meet all the energy requirements of the leisure complex, but it is also self-sufficient in electricity and a net exporter of electricity all year round. The surplus electricity is exported to other council sites and, in conjunction with the council’s public/private joint venture energy services company, Thamesway Energy Ltd, it will also be supplied to local sheltered housing residents and businesses as part of its green generation portfolio. Woking Borough Council has been officially recognised by gaining the Queen’s Award for Enterprise: Sustainable Development 2001 for the development of its local sustainable community energy systems.

Further information can be found at the DTI website

Gainclone, Audio Amp

What is a gainclone? Well a few years ago back in the late 90’s a relatively unknown manufacturer 47-Labs released the “Gaincard” which received excellent reviews in music magazines and alike. It immediately caused controversy because it was based around a power amplifier IC (Integrated Circuit) that only cost a few pounds, yet a typical setup would cost you a couple of thousand.
It was not long before people (the DIY audio electronics man in shed type) started to copy the design and add little bits here and there to improve things, these copies of the Gaincard were appearing on internet sites and discussion forums around the globe and soon the name Gainclone was given to it.
Typical designs are based around the LM3876 and similar IC’s from national semiconductor and only require a handful of external components. For this reason the Gainclone is ideal for audio hobbyist and DIY’ers. We has put together a collection of files and components lists in kit format available on our products page.

Related Links:

Where it all started http://www.sakurasystems.com/

The GainCard http://www.sakurasystems.com/products/47amp.html

National Semiconductor http://www.national.com/pf/LM/LM3876.html

Gainclone on wikipedia http://en.wikipedia.org/wiki/Gainclone

Lithium Polymer Batteries

Lithium Polymer (commonly called Li-Poly)
Lithium Polymer (commonly called Li-Poly)

Lithium Polymer (commonly called Li-Poly) are one of the latest developments in rechargeable battery technology, these new cells are a great advancement in technology from the older Nickel cadmium cells (referred to as NiCd) and nickel metal hydride cells (NiMH).

Li-poly cells are slightly different from there predecessors in the fact that they provide a average of 3.7 Volts compared to the 1.2 Volts of NiCd and NiMH cells. Additionally they also provide a greater power to weight ratio, it’s now normal to see from a Li-Poly a few hundred mA from a cell that only weighs a few grams.

Li-Poly cells require slightly more attention to both the charging circuit and also a monitoring circuit whilst being used. Thus they have to be protected from overcharge by limiting the applied voltage to no more than 4.235 V per cell. During discharge on load, the load has to be removed as soon as the voltage drops to around 3.0 V per cell, if the cell is continued to be used below the 3 volts then you will find that the cell will no longer accept a charge resulting in a cell that is of no use to anyone and can only be chucked into the bin (recycled).

Among the advantages of Li-poly cells one of it unique features is that there is no metal disks in the cells unlike others this enable the cell to be virtually any shape desired. This means that for the mobile phone and laptop market these cell are ideal. Due to this usage of the cell in such markets as the telecommunication, it has meant the mass production of cells and hence the price of the cells is constantly dropping.

Lithium Polymer Suppliers and manufactures:

Kokam

Kokam possesses its own unique, proprietary technology (the Superior Lithium Polymer Battery or SLPB), which has proven marketability over existing and perceived competition. Substantial opportunities exist to tap into the market of cellular phone manufacturers and distributors who seek better lithium-ion batteries than those readily available on the market. The challenge is to bring cost-efficiency to the major channel members and OEMs, and Kokam has met this challenge. As more and more of the world’s population have gained an interest in these products (as well as notebook computers and similar portable devices), the demand for lithium-ion batteries has also increased and will continue to increase over the next five years. Kokam’s particular patented design employing the next generation lithium-ion/polymer technology, will increasingly occupy more and more of the total rechargeable battery sales in this industry. Based on its advanced technology and price competitiveness, Kokam’s market share will be extended as fast as it is able to increase production capacity. The cellular phone industry represents very strong demand for this next generation technology, which far exceeds the overall industry’s production capacity. Additionally, the size of market for notebook pc and PDA is being increased fast will be a great opportunity for Kokam. Kokam makes high standard and reliable re-chargeable Lithium battery and its processing equipments and also develop new advanced technologies for future.

http://www.kokam.com/english/biz/kokam.html

 

SANYO

SANYO has developed a lithium polymer battery that is ultra-thin (under 4mm) & ultra-light with superior performance, SANYO reliability, and new technology developed in our labs. Lithium polymer batteries employ a new gel-type electrolyte to provide power to the most demanding application in the hand-held world. Once again, SANYO has developed the answer to the demand for ultra-thin, ultra-light, high-power applications.

http://www.sanyo.com/batteries/lithpol.cfm

PowerStream


Lithium Polymer Batteries from PowerStream. Battery chargers, power supplies, dc to dc converters, custom, semi-custom and off-the-shelf

http://www.powerstream.com/li-pol.htm