Comment: Flicking a switch to turn on the lights or power up our gadgets is something many of us do without a second thought. But that’s far from the case for everyone. Globally, about 760 million people live in remote communities without access to electricity.

For those living off the grid, stand-alone diesel generator systems are still the primary source of power generation. However, the dramatic fall in the price of solar photovoltaic (PV) and battery systems over the past decade is accelerating the switch from diesel dependence to reliable, affordable renewable energy.

That’s the good news. But there’s an important piece of the puzzle still missing – namely how to make sure the tech being installed today can cope with future energy needs.

The case of Aotea Great Barrier Island

Aotea Great Barrier Island, located 100km off the coast of Auckland, stands out as a shining example of a tiny island leading the green transition, with solar panels on almost every roof. 

Additionally, Aotea’s Claris Centre is home to the country’s largest off-grid centralised solar network, which boasts 250 solar PV panels, with a total capacity of 69 kW, supplying power to seven shops.

This centralised PV system is backed by Tesla battery packs to store surplus solar generation for use at night (when solar is not being generated). On top of that, EV drivers on Aotea can charge their vehicles in a public charging station at the Claris Centre.

Aotea has among the highest rates of privately-funded, small-scale solar PV uptake in the world. These stand-alone PV-battery systems play a direct role in decarbonising the island’s energy economy. They’re also recognised as one of the “no regrets” options for island communities generally, as they contribute to energy independence by reducing the need to import fuels.

But they may not be the best long-term solution.

First, recent high-profile natural disasters have shown that not all rooftop PV systems withstand extreme conditions to the same extent. So, there is an urgent need to provide an effective way for a household to use the neighbours’ energy assets if disaster strikes.

Second, power demand is set to rise with the electrification of heating and transport. This means household-level sustainable energy systems designed today will probably not be able to cater for power needs in a few years’ time – and hence will need capacity reinforcements, which might not be either technically or economically feasible at the household level.

Third, given battery storage is still relatively expensive, storing surplus solar generation is not cost-effective for everyone. Storage is especially important in remote areas where there’s no utility network to provide backup. Without storage, it’s not possible to soak up the excess solar generation and the surplus gets dumped.

How off-grid micro-grids can help

A micro-grid is essentially a self-sufficient energy system serving a specific area. It uses low-voltage poles and power lines to connect distributed energy resources and end-users. And it can integrate one or more types of energy, including solar PV and battery storage.

One of the most important characteristics of micro-grids is “intelligence”. Micro-grid controllers are responsible for providing this intelligence and making the best use of the available energy infrastructure. They can enable energy resources to be traded, matching eager sellers with willing buyers, including “prosumers” – producers and consumers of energy.

How would a micro-grid help Aotea Great Barrier Island?

Aotea has a lot of sunshine during summer. The island also has wind resources it can call on to meet its energy requirements. A prior feasibility assessment estimated that harnessing a combination of solar and wind for electricity generation could serve the needs of the island’s inhabitants for a reliable, affordable, and sustainable energy supply.

Recent research at Te Herenga Waka—Victoria University of Wellington looked at the technical feasibility and economic viability of independent micro-grids for three communities residing on the island, namely: Medlands, Tryphena, and Mulberry Grove.

Given the renewable energy potential at each site, we considered a battery-backed micro-grid, driven by solar PV and wind turbines for Medlands, and solar PV-battery micro-grids for Tryphena and Mulberry Grove. These micro-grids would serve residential and commercial users, as well as provide power to charge EVs in a scenario where the island’s transport is electrified.

Our analysis found the projects to build and operate these grids would reach a break-even point in the seventh year of operation – and deliver positive returns after that.

The “levelised cost of electricity” (a measure of the average net cost over the lifetime of the generation assets) is in the order of 10¢ per kWh and all the usual financial metrics indicate the projects can provide a high return with little or no risk.

Smart, integrated micro-grids represent a leap forward in how we coordinate the generation and consumption of variable generation and demand in remote regions, such as Aotea and Rakiura-Stewart Island, which relies on diesel generators. They have enormous potential to improve energy resilience, reliability, and power quality, while also reducing energy costs and increasing the proportion of clean energy use.

Accelerating the transition to stand-alone micro-grids deserves to be a key long-term strategic energy plan for any community far from the national grid.

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