Tuesday, June 09, 2009


Mark Davis writing in the SMH on the weekend has raised the question of whether subsidising household photovoltaic solar power is a cost effective form of carbon abatement.

It allows me to blog about an issue that's worried me for some time - which is the related question of how much power is wasted through heat loss in domestic transformers. Basically electric energy is used in four main ways in households. These are heating, lighting, powering motors and driving consumer electronics. The first - heating - is one where direct conversion of sunlight to thermal energy works really well, primarily solar hot water. Other heating is household heating and heat for cooking (and clothes dryers). For these gas can be a good substitute, or for a cook top at least the use of electric power in an induction cooktop.

Lighting has seen huge advances in lower power consumption devices, and various applications that rely on motors have been made more efficient (especially refrigeration).

But consumer electronics continues to consist of devices operating at somewhere in the range of 6-15V DC but mostly powered by a 240V AC connection hooked up to its own transformer. Each of those transformers wastes a lot of energy in heat. I keep wondering whether there isn't a better way to provide household DC power. Wouldn't one transformer lose less heat? What is the loss of DC power f we try to reticulate it over the whole house? More importantly if we did have a DC power rail, wouldn't a battery and photovoltaic cell arrangement work very well for powering this component only? Significantly, hooking these household devices into a DC rail with battery backup would ensure that all the communications devices continued to operate in times of power outages.

This is becoming an increasing issue in telecommunications policy as we move from copper connections to fibre connections. Because of history the telephone service was built powered from the exchange and with battery back-up in the exchange. This has led to an expectation that the telephone still works as a "lifeline" service during power failures. But with fibre connections there is a need for a powered device in the home.

In its discussion paper on greenfield estates the Department of Broadband etc has referred to the question of whose responsibility providing the battery for the network terminating unit is. This ignores the fact that increasingly households have been relying on powered phones or computers requiring power to communicate anyway. Surely the more effective emergency management question is "is there a better way to manage power in the home so that emergency power is available for all communications devices?" It would certainly be true that that would be better supplied as a DC source rather than an AC source.

Perhaps I should pose the question to the equipment industry through something like the Digital Living Network Alliance.


Howarth said...

second that. It's "Edison's Revenge" - his electric power system used DC but, because of the transmission advantages of AC, it was overtaken.

A good start would be a standard on the voltage and plug size/format these devices use. That might at least encourage people to only have one charger, rather than an array of them warming away 24/7.

Another idea I've often thought would be useful (and could integrate nicely with your DC rail) is a "standby kill switch" by the front door - similar to the master switch in some hotel rooms - so with one switch you can turn off everything except appliances connected to an always-on circuit, like the fridge and washing machine, clocks and so on.

Anonymous said...

oh come on....transformers in CE,,,mostly a thing of the past..switch mode is the go these days..narky little closed loop power converters operating a freqs even above what a dog can hear