‘Scheduled solar’: new forecast, management system ‘cracks’ NT solar impasse


Proa is currently in the final stages of commissioning two solar projects in the Northern Territory with 15 MW of combined capacity. Contracted by Lendlease, the two projects use a specialised ‘Capacity Forecasting System’ which the company says allows the solar farms to make 30 minute forecasts with 99% accuracy.

That is, the system promises “scheduled solar” by combining new energy management technology with environmental monitoring and a battery that need only be a fraction of the solar farm’s capacity.

“We think we’ve cracked the problem to make solar investible in the NT [Northern Territory],” Proa Managing Director, Victor Depoorter, tells pv magazine Australia. “This is the most advanced solution that has been developed to date, as far as we know… to manage the variability and uncertainty of solar at the generator level.”

Since the amount of time spent on real life testing in the commissioning of the two NT solar remains limited, Depoorter adds: “We want to have a little bit of caution still, but the results we’ve been seeing in recent months have been really, really exciting.”

Why the NT needs ‘scheduled solar’

Three years ago, Proa began building on its experience in solar forecasting, management and monitoring to enable solar farms to meet the strict export rules set out in the Northern Territory’s Generator Performance Standard.

This standard came into effect in 2020, introduced by the Power and Water Corporation, the Territory’s government-owned utility and primary electricity distributor.

These rules, specifically section, basically require solar farms in NT to operate like scheduled generators would in Australia’s grid, the National Electricity Market (NEM). That is, whatever a solar farm commits to generate in the next 30 minute dispatch interval, they actually have to satisfy. 

“It’s not like for semi-scheduled generators in the NEM where you can go above or below your dispatch target… depending on cloud cover,” Depoorter explains. In the NT, “whatever you promised, you have to do. And if you don’t, then you are not conforming with the rules.”

“It’s putting the bar really high for solar,” Depoorter says. Such a high bar that numerous solar farms like Batchelor 1 and 2, and Manton have been sitting idle for over three years, exporting nothing to the NT’s two islanded grids. Thanks to sizeable battery storage additions, other solar farms have been able to officially connect, but are reportedly still not dispatching.

The reason NT solar farms are not given the same flexibility as those connected into the national grid comes down to size. “The grid in the Northern Territory is a lot smaller than the NEM and a single generator could cause some serious instability to that grid. So the relative responsibility of single generators in that grid is a lot more significant and that responsibility has kind of been put on the generator’s side,” Depoorter says.

This is especially problematic because the Territory seriously lags behind the rest of Australia in terms of the share of renewable energy in its grids. According to the Clean Energy Council’s 2022 Clean Energy Australia Report, renewables are set to account for just 23% of consumption on the Darwin Katherine grid and 14% in Alice Springs by 2030, if current trends continue – well short of the Territory’s 50% target.

How Proa’s Capacity Forecasting System works

Proa has long worked in the space of solar forecasting, developing a system that relies on four different technologies, including skycams, satellites, live data and numerical simulations, to make predictions.

Its Capacity Forecasting System, however, builds significantly on this original technology – basically wrapping this system into an energy management platform that is capable of making bidding decisions. 

This system needs to be combined with some firming capacity, like a battery, because the nature of solar energy is heavily weather-dependent. However, the battery need only have 20% to 40% of the solar farm’s capacity, Depoorter says, with just half an hour of storage duration.

“At the end of the day, we are replacing lithium with smarts,” Depoorter says. Proa’s system relies on intelligent decision making to generate bids dynamically as function of the weather conditions and the batteries firming capacity.

“There is always a little bit of spillage if you have a small battery,” Depoorter notes. If there are really big ramps, solar farms need to pre-curtail to a level they will be able to satisfy as per the capacity forecasts. “So the peak in the solar price will get shaves, if you will,” Depoorter says.

“But even with the sort of proposal I was mentioning before [batteries sized to 20% of solar capacity], you can achieve very high solar utilisation rates, in the order of 85 to 95%.”

The company is currently in the process of making its Capacity Forecasting System solution commercially available to the market.

Certainty allows solar to become ‘scheduled’

Depoorter says Proa’s tool changes the paradigm around forecasting by creating certainty. “It’s not about being accurate anymore, it’s just about being certain.”

Using the technology, solar projects can commit to their generation with a really high degree of certainty. “When you do that, then you can really start making operational decisions on that [information],” Depoorter says.

“Solar forecasting is the art of trying to be the least wrong possible, or trying to provide the best guess of what the future looks like in different timescales… there is always uncertainty attached to those forecasts which mean that, in an operational context, it has always been treated with a touch of caution.”

Basically, forecasting has predominantly been seen as useful, but has had only a moderate impact on decision making by generators and market operators.

“But in the case of the NT, our system is basically the heart of the solar farm,” Depoorter says. “If the Capacity Forecasting Systems stops, the whole plant stops.”

“This project we’ve been working on is really kind of changing the role of forecasting, at least for solar generators.”

Applications beyond the NT

Depoorter believes the technology could have applications well beyond the Northern Territory as well. Microgrids are definitely a space the company will eventually investigate, he said. 

As solar penetration increases throughout the globe, the need for generation certainty will also grow, Depoorter predicts. At one stage, all solar farms in Australia were non-scheduled. Now, projects above 30 MW have to be semi-scheduled. The renewably-driven future, he says, may require more scheduling again.

“Scheduled solar sounds like quite a good idea in general terms.”

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