How To Reinforce Skinny Rural SWER Connections With Solar Batteries

So you’ve made the tree change, shifted to the dream country block or taken over the farm now Dad has retired. While the peace and quiet is great, the fringe of grid power can prove problematic.

Today we’ll look at ways to take tenuous SWER connections from skinny to muscular. Everyone deserves cheaper, cleaner power; you just need a plan and a sensible budget.

Recently, we addressed skinny suburban supply cables and solar for strata. While rural setups face similar issues, the solutions differ when you need more capacity and, fortunately, have more space to maneuver.

Our Farm Was Coke Fired

In the early 1950s, my Grandpa ditched kerosene lamps & electrified them with a thoroughly up-to-date 32-volt DC “lighting set”. Sixteen lead-acid batteries in rebuildable glass jars, charged not by a windmill but by a 2 HP petrol engine and 800 watt brushed generator. So modest were these systems, if you could afford appliances, they were often “plugged in” to the light sockets.

Heavy lifting was left to coke (baked coal) for the AGA stove, later converted to oil. This was the heart of the house, it heated the kitchen and the hot water service in the roof.

In 1959, modernity arrived with publicly subsidised mains electricity. Nanna was so relieved to turn the stove off in summer.

Basic Electrification Was A Public Good

The SWER system, or Single Wire Earth Return, is very straightforward: it sends 19,000 volts through a transformer and completes the circuit by plugging it straight into the dirt. Broadly spaced posts and one very thin, taut steel wire made widespread electricity affordable for everyone.

This economy came with a trade-off: limited power capacity. Originally, managing a 3.6kW hot water system overnight and a fridge or stove during the day with a 5kVa transformer (providing 20 amps single phase) was enough. After all, houses didn’t even have power points in the bedrooms. Today, that wouldn’t cut it.

Electrification Is Difficult With Only Half The Supply

Most Australians have 63 amps or 14.5kW available (or triple that for a 400-volt 3-phase supply), but SWERs can sag badly, browning out before tripping off at 45 amps. They suffer similarly when exporting solar back into the network, so they are often export-limited.

Worse still, the DNSPs limit total inverter capacity on SWER to 5kW mostly, so even connecting solar is hamstrung compared to 10kW systems in town.

There are some “2 phase” SWER transformers, which are 180° split phase, best thought of as two parallel single phase supplies.

EV’s Will Cut Both Ways

To accommodate electric vehicles (EVs), we must manage legacy infrastructure to endure more throughput, which is especially important when a standard EV charger may use 30% more power than many SWER transformers can supply for 10 hours straight.

EVs have dirty big batteries, so there are opportunities for either charging up in town and bringing a tank full of fuel home or simply having more storage available that you can access via V2L or, hopefully, soon, the higher capacity of V2G.

What’s The Way Forward?

Farmers have always been savvy, so I’ll bet my boots that agricultural EVs will be popular soon. As soon as they’re available, quiet utes & reliable e-motor cycles will need charging though.

The Basic Solution

Reinforcing a SWER supply using a battery hybrid system to stiffen up what’s already available will be the most economical.

Modern, lightweight battery hybrid inverters like Fronius, Sungrow & GoodWe offer excellent performance on par with suburban pricing; however, in some jurisdictions, a 10kW single-phase inverter won’t be network-approved, and I couldn’t recommend running one off-grid. They’re not designed for it.

Getting Serious Will Need More Resources

Significant increases in energy consumption will be met with generation and storage on-site, while the existing SWER will be used for backup.

Having built, expanded, and maintained remote area power systems for years, I invariably used diesel generators to maintain security, either running daily to get the cool room down to temperature and charging batteries or doing random hours responding to long cloudy weeks in winter.

Backup generators are the most troublesome but equally essential part of remote area power. However, a grid connection for backup will be more reliable, electrically stable and cheaper.

I’ve transformed a farmer’s experience. Living beyond Ceduna put him at the very western extreme of the national network. With a saggy 5kW supply his welder struggled and didn’t work at all with the air compressor.

Using a relatively small battery and my favourite Selectronic SpPro, suddenly there was 12kW of surge capacity plus the SWER supply. With 19kW available the welder would throw beautiful hot arcs. All the workshop equipment worked better and when his neighbour’s tractor mowed down a power pole, the lights didn’t even flicker.

This is what reliability looks like

3 Phase Is Feasible

It’s easy enough to create a 3-phase supply, to run specific machinery, or, given the budget, power a village of 30 houses using three grid-forming inverters. This is the approach the network companies themselves use to take hamlets or individual houses “off-grid” and avoid costly maintenance for poles and wires and bushfire liability, too.

Treating The Grid With Contempt

Genuine off-grid solutions can be infinitely more capable, resilient, expandable and expensive. However, they can be 100 times more cost-effective than paying for grid augmentation if you need an 11kV distribution line.

Selectronic (or perhaps Victron) systems don’t need the authorities’ approval; better yet, DC-coupled solar means you can keep adding arrays until the cows come home.

Uncle Arni’s ready reckoner for pricing top-quality Australian-made off-grid solar power. It might sound expensive but grid hybrids can be half the price when you don’t need huge batteries or a 15kVa diesel generator costing $15,000. STC incentives still mean the actual solar panels are dirt cheap.

The Power Is Now Yours

Solar power is cheaper than ever, and the technology is now incredibly capable. My best advice to those on a skinny rural grid connection is to seek out a quality installer. One who can help identify what you need, will answer the phone and can swing by for after-sales service without much hassle.

Remember, when your generator won’t start, the phone rings out, and you can hear your freezer defrosting, skimping on quality could cost you three times more before you circle back to that first quality quote.

Original Source: https://www.solarquotes.com.au/blog/swer-solar-batteries/