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Planning for the future with solar forecasting

Given the supply of energy from solar panels varies according to cloud cover and other weather conditions, could there be a way to accurately predict what will happen in the future at a particular solar installation?

Natural weather fluctuations could pose problems as more solar comes online, potentially undermining the stability of the local distribution network and limiting the amount of excess solar power than can be exported.

In the search for solutions, ARENA has provided funding to researchers at the Australian National University (ANU). Together with most of Australia’s electricity distribution network service providers (DNSP), they have developed a system able to predict the near-term output of power solar panels, factoring in natural variables like weather.

The scale of the challenge was outlined in a report published by ARENA late last year. Mapping out the challenges that network operators face from the rise in rooftop solar, the research also details opportunities likely to arise from the work underway to improve forecasting.

How does solar forecasting work?

Utilising state of the art forecasting technologies, Australian company Solcast is partnering on the project. They will detect, track and predict the future positions of cloud cover using weather satellites and weather models. This information allows Solcast to forecast solar PV output, which can be converted to power output predictions.

Given the output of a solar PV system is dependent on the strength of sunlight available, better understanding the variables could help DNSPs to forecast the amount of electricity they will need to supply from the grid.

In areas with low PV penetration, making these calculations is rarely a problem. Energy produced from rooftop installations is first consumed on-site with any excess exported into the local network and consumed nearby, where the supply of grid power is generally sufficient to provide voltage stability.

The problems start when the number of solar systems increases and the power generated by PVs approaches – or exceeds – the total load in that area at any point in time. This can make it hard to predict the total load on the system and lead to voltage fluctuations, increased wear and tear on transformers and tripping of protection devices.

ANU’s project has set out to address two of these issues – the lack of visibility of how much energy is generated by solar, and the voltage fluctuations associated with short-term variability PV output.

The first challenge arises from the way that energy from rooftop solar systems is metered. Because only the amount exported to the grid is measured, not the total produced by the solar panels, DNSPs cannot know how much energy the systems generated, how much they are likely to generate in future, or at what time of day they are likely to generate it in future.

To address this problem, the ANU project is using the Solcast forecasting and modelling systems to estimate the amount of power produced every 10 minutes. If there is sustained cloud cover in an extreme weather event and the grid is needed to supply all of the energy load, this will provide an understanding of true level of demand.

The project aims to address the second problem by providing short-term forecasts (“nowcasts”) and work with DNSPs to prepare for solar induced voltage fluctuations arising from clouds shading solar systems, particularly in areas of high penetration when large numbers of systems are affected at the same time.

As DNSPs do not have the tools required to execute the necessary response to these events, this information alone won’t be enough to manage potential drops in voltage. However, the project will improve the modelling of load flows in a network where energy flows in two directions. This is different to previous studies undertaken prior to the growth of solar which assumed a unidirectional energy flow.

Not only will this help DNSPs to identify where there is potential for overload on the grid as a result of drops in voltage, it provides a step towards developing the tools required to respond to these events.

The report acknowledges that ‘significant’ investment will be needed to develop systems that allow the network to communicate with customer devices and even operate them remotely, so it won’t happen overnight. But once these tools are developed, the data collected through the ANU project could help distribution businesses to act on variations in solar output.

What does this mean for the network of the future?

Relevant to large solar farms as well as distributed installations such as household rooftops, the forecasts aim to provide system operators with the information they need about how much load can be met by solar, and how much of the heavy lifting will need to be met by centrally dispatched generation.

This type of information will be vital to maintain stable energy supplies as the shift to renewables accelerates, and the network becomes increasingly distributed.

The technology underpinning the forecasting system is already working. The ANU project is complementing work Solcast has underway with large Australian solar farms to provide forecasts from just five minutes ahead.

Looking to the future, there are options available to manage the potential impacts of a high penetration of solar.

Distributors could invest network improvements and uprate feeders and substations, or install line drop compensators to help maintain a constant voltage. Restrictions could be placed on the amount of power that can be exported back to the grid, or in the longer term consumers could allow DNSPs to take control of their solar system and storage to manage variability in output.

Together with ARENA funded projects like NOJA’s Power Intelligent Switchgear, UTS’ Networks Renewed and UQ’s Increasing Visibility of Distribution Networks to Maximise PV Penetration Levels, there is work underway to develop tools and techniques to manage high solar penetration.

While we don’t necessarily have all the tools to solve these problems yet, work is underway to manage the challenges as the renewable energy transition accelerates, and Australia’s energy system becomes increasingly distributed.

Read the full report here.

Can this Tassie wind farm provide grid-stability services? We’re going to find out

On the edge of a clifftop in Tasmania’s rugged northwest corner the winds known as the roaring 40s blow regularly and strong.

And the Musselroe Wind Farm is perfectly situated to take advantage. On their own, these 56 turbines provide 5 per cent of Tasmania’s yearly electrical supply.

But, with support from ARENA, this 168 MW power generator is about to take on an even larger responsibility, attempting to answer questions that will be important for our renewable energy future.

Can a wind farm provide the grid-support services needed to ensure stable and reliable supply and which are currently contributed by coal or gas fueled power stations?

And, just as importantly, can they make enough money doing it to make it all worthwhile?

The project, to which ARENA has contributed $497,000 of the $1 million total cost, will use the farm’s wind turbines to supply frequency control ancillary services, known as FCAS.

Woolnorth Wind Farm Holding, which operates the Musselroe wind farm, will provide the remainder of the project budget.

WHAT IS FCAS?

The power system requires that both generation and load are in balance in order to operate safely. If there is a variation in generation without a corresponding variation in load then the frequency of the power system will deviate, which can lead to instability or, at extreme levels, cascading failure and blackouts.

FCAS is a process used by the energy market operator to maintain the frequency of the system within the normal operating band around 50 cycles per second.

Put simply, FCAS provides a fast injection of energy, or fast reduction of energy, to manage supply and demand.

Traditionally provided by generators such as coal and gas plants, these services are purchased by the energy market which is operated by the Australian Energy Market Operator to maintain frequency and ensure the stability and reliability of the grid.

This project aims to shake that up, instead using wind power for the same purpose.


SO HAVE WE TRIED THIS BEFORE?

Sort of.

In August, ARENA and the Australian Energy Market Operator (AEMO) signed an agreement with South Australia’s Hornsdale Stage 2 Wind Farm to trial whether it could provide FCAS, becoming the first Australian wind farm to attempt to do so.

The Musselroe project will also trial this approach, seeking to discover whether the provision of FCAS services is technically possible, but will add an additional layer of complexity, examining the potential commercial and economic value available to a wind farm from participating in the FCAS market.

It is expected that the provision of these services from wind farms will allow the electricity grid to integrate increasing levels of variable renewable energy while simultaneously improving grid security by broadening the sources from which FCAS can be obtained.

But if renewable sources are to be harnessed as providers of grid support services like frequency control it’s important to know not just that it is technically possible but that sufficient markets are in place to create the incentive for them to do so.

ARENA CEO Ivor Frischknecht said a successful trial at Musselroe could see FCAS be adopted at other Australian wind farms.

“Wind power is playing a big part in Australia’s transition to renewable energy and we want to explore how wind can provide essential grid stability services.

“Musselroe Wind Farm will be able to answer for us the key question that so far hasn’t been answered; does it make economic and commercial sense for a wind farm to provide FCAS and participate in the FCAS markets?” Mr Frischknecht said.

If Woolnorth find that there are real commercial drivers for wind farms, then we should see more and more of them providing FCAS which will lower FCAS prices and in turn lower electricity bills,” she said.

The project also offers several points of difference that make it a valuable complementary addition to the Hornsdale trial

Musselroe runs using Vestas turbines, which differ from the Siemens-built ones at the Hornsdale facility.

Tasmania also offers an environment where FCAS services are required more often, allowing the technical and economic factors at play to be tested more stringently.

The Musselroe site will also examine how a co-located battery storage system can create advantages for how the wind farm can supply frequency control on demand.

General Manager of Woolnorth Wind Farm Holding, Stephen Ross said very few Australian wind farms provide the network support offered by FCAS.

“This project aims to identify the true capability of wind power to provide system support, how that might work and what benefit there would be in terms of reliability and security at local and system level,” Mr Ross said.

“This is an opportunity to prove that wind farms can contribute to the stability and reliability of the electricity network.”

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