For solar PV to fulfill everyone’s expectations as a mainstream source of energy in the grid it must lose some of its reputation as an irregular generator. It won’t be easy but it can be done, the audience heard.

The panel:

  • Dhananjay Sambare, project development manager, Ovida (moderator)
  • Paul Nidras, principal consultant, Jacobs
  • Sally Torgoman, infrastructure lead advisory, PwC
  • Chris Halliwell, manager of renewable energy and environmental markets, TFS Green & Renewable (pictured above)
  • David Manning, global head of hybrid, Juwi Renewable Energy

For solar to shoulder aside coal and gas it needs to convince buyers that it is reliable. That’s hard to do when generation ends at sunset every day. There is a strong case for firm solar in the NEM – and luckily there are more than a few ways to achieve it.

About 80% of demand in the NEM is traded through the forward contract market, said Paul Nidras, principal consultant at Jacobs. Because generation is variable from wind and solar – and very hard to predict – it has been hard for these renewable energy sources to compete in this market.

“Contracting capability is a key risk-management strategy in the volatile electricity market, so that becomes important as we see more and more of these technologies,” Nidras said.

Steady as she goes

Solar has an important role to fill as Australia nears the deadline for its Renewable Energy Target and its coal fleet is retired, but how can supply be firmed? The first strategy is a portfolio approach, Nidras said, where solar is increasingly included among a range of dispatchible sources – hydro, gas, coal – to supply a contract. “Over the longer term we’d expect the dispatchible supply mix would change, with more coal retirement, and that energy storage would play an important role.”

The cost of firming can be brought down, he said, by including solar and wind in the portfolio of generating assets. “The important factor is complementarity of generation profiles,” Nidras said. “You might not look at one wind farm but a diverse geographical portfolio of wind farms [to complement solar]. The flatter you make that composite profile, the least cost you would expect the firming to be.”

Storage will begin to help level out supplies as the cost of battery technology falls and pumped hydro sites are developed. “That’s going to come into play over the next decade and beyond,” he said, citing relatively low development costs for some pumped hydro sites. “The prospects for these technologies is good.”

Beyond the cities and towns

David Manning, global head of hybrid at developer and EPC company Juwi Renewable Energy, spoke about integrating renewables in mine sites, in particular referencing a study for a project in Western Australia where energy options include piped gas, diesel or renewables. (Juwi delivered the DeGrussa project for Sandfire Resources in Western Australia, with 10.6MW of solar and 1.8MWh lithium-ion storage.)

The project site has a good wind resource, he said, “quite strong during the evening, tapering off during the day and picking up again in the late afternoon … so we were able to back-fill the low wind resource throughout the day with PV.” With gas or diesel supplying the balance, the Juwi study found a hybrid wind-solar-and-storage solution could supply more than 80% renewable energy during summer and about 75% during winter.

In reserve

The battery is pivotal in taking on load while gas or diesel generation comes online, which can take up to five minutes for gas, he said, and 20 seconds for diesel. “The size of the battery has a significant impact on the LCEO [levelised cost of energy],” Manning said. There is also the weather to deal with. “We’ve also seen cloud events can reduce solar output up to 80% in 10 seconds,” he said. “In some situations where we lose wind and solar at the same time batteries are required to take the full load until thermal engines are up to speed.”

At this stage the project is likely to be comprised of 70MW solar, 86MW wind and 50MW battery storage. This would cut diesel demand by 90 million litres a year, or 900 deliveries. “PV and wind can provide off-grid energy at rates that are comparable with pipeline gas,” he said. “It’s the battery that allows us to provide 99.8% reliability and continuous supply for the mine site.”

Sally Torgoman said pumped hydro, with the right technology installed, can respond in seconds.

Pumped hydro, let it flow

Lawyer and engineer Sally Torgoman, infrastructure lead advisory with PwC, focused on pumped hydro and the need to encourage investors, who are the “lifeline that makes all the work we’re doing come to life”. It’s just a matter of how complex are the solutions and what size the costs. The big issues regarding firming are the solar duck curve – or “duck curse”, in Torgoman’s words – and the complexity around pumped hydro energy storage.

Pumped hydro is expensive and response times of 1-2 minutes place the storage option between your typical gas peaker, at 6-12 minutes, and batteries, measured in milliseconds. Using different technology types within pumped hydro can bring response times down to a few seconds, she said, “so [pumped hydro] can be quite competitive with batteries”.

Around the world, China is planning for 90GW of pumped hydro supported by solar and wind; in Germany developers are exploring ex-mining sites; and around Europe in general there is a belief pumped hydro should account for up to 6% of capacity. Using that benchmark there is about 4GW of opportunity in Australia, she said.

Site selection is key, including access to water and transmission. “This is where firming comes in, as you can use solar for part of the pumping and be able to export to the grid,” Torgoman said. Depending on the turbine-type and configuration “there are many, many solutions here”.

New innovations

In markets, firming can be handled in a number of ways, said TFS Green & Renewable manager of renewable energy and environmental markets Chris Halliwell. Current convention says it’s up to the retailer to provide firming services, “and historically that’s been a reasonably manageable process”, but the future will be different.

The entrance of variable and intermittent generators has changed everything, and “a new suite of innovations [is needed] in terms of wholesale contracts to be profiled and designed to align with the new generation and capacity capabilities” including batteries, pumped hydro, demand response, virtual power plants and of course solar and wind have some different contractual requirements.

“As we have more contracts available … more people will be able to participate in the new wholesale energy market and price efficiencies should hopefully prevail.”