Most people would regard the availability of electrical power as a simple commodity; if it is required, it is supplied. This is not necessarily true for much of rural Australia. While 90% of the population is supported by a robust network of three phase power, beyond the cities there are serious power distribution issues that affect existing industry and projected economic development.
Expanding an existing network is an expensive process, and the cost must be borne entirely by individual consumers in remote locations. It therefore makes sense to explore different strategies that will more fully use the existing infrastructure.
Australian is unique as it has a vast terrain with very low population densities to serve. The cost of universal 3 phase distribution has been prohibitive. Much of rural Australia is therefore supported by Single Wire Earth Return (SWER) system to deliver 240V single phase power, or by the two-phase 480V’ variation. All Australian states use this type of technology to a small or large degree.
The SWER line connections that provide energy to thousands of rural Australians are not able to support three phase equipment. A common myth is that three phase equipment is used only for heavy industrial applications and that has little place in rural, agricultural environments. This is not necessarily the case. Three phase motors are cheaper to manufacture than their single phase counterparts. As a result much electrical machinery being built today includes small three phase motors as an integral part of their operation.
Some common three phase installations include milk chiller systems for dairies, refrigerated containers, chaff processing and elevating plants, fruit grading and packing equipment, pivot irrigators vehicle servicing hoists, MIG welding equipment, and electric roller doors and gates.
The simple absence of three phase power in much of the rural sector has placed serious limitations on the sorts of value adding activities that may be carried out. Farms with a reliable single phase supply will often revert to using diesel powered generators just to supply their three phase equipment needs. This can have an immense impact on operational costs for rural enterprises.
The daily demands on power infrastructure continue to rise, with an escalation of power customers wanting to install a range of new equipment at their rural locations.
A fundamental question for power customers often becomes: How can I get the most from the available energy of my existing supply? There are two broad approaches to this problem. One is to make the customer loads more efficient in order to reduce the actual power demand. The second is to spread the impact of the power demand over a longer time interval so that high current loads operate in staggered time delays of minutes, hours or even days.
A very common assumption is to blame the more conspicuous domestic appliances, like televisions and fluorescent light, for creating a large impact on their supply. The largest impact on rural infrastructure actually comes from equipment with heating elements and large single phase motors. Some common culprits that have high impact loads are electric fan heaters, hot water services, irrigation pumps and refrigeration compressors.
A common requirement for dairies is to have a large supply of hot water for cleaning and sterilising. Solar hot water panels have proven to assist with power reduction, as does additional insulation fitted to the water tank and pipe work. Modern heat-exchanger hot water systems work like reverse-cycle air conditioners, these can also provide huge reduction in power consumption when compared with heating elements.
Another popular option is the singe phase to 3 phase power converter unit, available from Phase Changer . These power converters create 415V, 3 phase power from a 240V power source. When the phase converters are used to drive 3 phase motor loads, they can halve the instant surge currents of medium and large motors, helping to reduce the creation of power line spikes in rural locations. Where 3 phase converters are used to replace 3-phase diesel generators, they may be five times more cost effective to operate. 3 phase power converters also don’t have the ongoing requirement of fuel replacement.
Grid-connectable PV (photo-voltaic) solar power systems are increasing in popularity. They will not help to deal with high start-current equipment, but they can make a serious overall reduction in kilowatt consumption during periods of daylight.
Another off-the-grid power reduction option is the use of high voltage D.C. pumps that run direct from solar arrays, without the need for storage batteries or inverters. Modern microprocessor control ensures that the pump won’t stall and burn out at dawn and dusk periods.
A creative way to supplement to home heating fully independent of the AC mains supply, is the solar air heater concept. A small DC solar panel drives low voltage fans to circulate household air through a solar air heater box and even with modest sunlight exposure the air passing through the system can be elevated by 20º.
Where the available power is extremely marginal it is possible to stagger the starting of loads using automatic time delay modules. Priority switching circuits can also be used so that high current start-up events don’t all try to occur at the same time.
Installing new equipment does not necessarily mean that more energy and infrastructure will be required. This article aims only to highlight the changes in power demand and smarter ways of getting the most out of the infrastructure that is already in place.