Letter: Wired for savings

Sir: Arthur Tarrant (letter, 12 August) dismisses much too casually the advantages of low-voltage direct current (DC) wiring in buildings. Six volts may be too low; 12 or 24 volts might be preferable. But the choice of voltage is less important than the choice of DC itself.

As Keith Bailey (letter, 11 August) correctly notes, many of the loads in modern buildings require low-voltage DC - all electronics, computers and data-processing equipment, for example - and others can operate equally well on DC as on alternating current (AC). Within a single building, the distances involved are not so great as to require cables "of enormous size". A single AC-to-DC converter between the mains and the building could supply the DC wiring. DC losses may be compensated by the savings achieved by eliminating the AC-to-DC "power pack" in every piece of consumer electronics. Using DC directly also avoids the problem of AC disturbances or "spikes" that can fry every chip in a database.

Moreover, many of the most promising new generating technologies, including fuel cells and photovoltaics, deliver DC directly. A building wired for DC can use this supply on the premises.

WALT PATTERSON

Senior Research Fellow, Energy and Environmental Programme

Royal Institute of International Affairs

London SW1