Sunday, November 11, 2012

Combining low voltage lighting and WiFi

On my visit to Indonesia the mains power failed several times. As with many developing nations there is a shortage of electrical generating capacity, as well as storms interrupting distribution. So I suggest that a good area to focus for green energy technology would be the combination of low and backup electrical power. The idea would be to have equipment which could run at three power levels as circumstances require: a low power mode during a blackout to run from batteries, medium mode during peak periods when power prices are high and normal power mode the rest of the time.

Backup generators can be used for critical infrastructure. As an example when waiting for a car outside Pekanbaru airport I noticed that while the lights in the main terminal building went off during a thunderstorm, the lights in the control tower remained on. But such generators are expensive to purchase and maintain.

Homes and offices can use batteries for essential lighting and communications. But much ICT equipment does not have a low power mode for running from batteries. While laptop computers are designed to run on batteries, devices such as Ethernet and WiFi routers are not.

One area for research may be to combine different types of equipment for low power use. As one example, I suggest using low power LED lighting systems for carrying WiFi signals. Offices, hotels, apartment blocks and universities have WiFi routers to cover each few hundred square meters of floorspace. These must be placed to provide sufficient signal coverage. An alternative approach would be to use a leaky feeder.

A long antenna cable can be attached to a WfFi router to carry the signal around a building. As an example, the router can be placed at one end of a corridor and the cable run trough the ceiling down the length of a corridor to the other end of the building. In multi-story residential building, such as an apartment block, the cable can be run up the stairs.

Installing cables is an expensive and complex task. Leaker Feeders are usually only used in locations such as mines, where radio signals are blocked. One way to reduce the cost of a leaky feeder would be to combine it with the building's lighting cabling. Normally a mains power cable would not be used for radio signals, due to safety and interference concerns. However, it may be possible to combine a radio antenna and low voltage cabling used for LED lights.

Some LED lights are now available as a adhesive tape which is cut to length and the stuck to the ceiling. This saves having to install cabling in the ceiling and cutting holes through to attach light fittings. One such strip could be attached to the ceiling of a corridor to provide lighting and also carry WiFi signals. Led lights have electronics for power conversion and some work may be needed to prevent this interfering with WiFi signals.

Multiple routers would normally be installed for redundancy.  This could be done by attaching both to the one LED cable, or to cables on alternate corridors, or floors, of the building.

Where more communications capacity is required, multiple WiFi units could be used on the same or alternate LED cables. At times of low demand, or when there is a shortage of power, some routers could be switched off.

Providing more reliable WiFi communications may remove the need for communications cabling in the building, for telephones and computers, making for significant savings in installation costs.

No comments: