Australian policy makers show no signs of tiring from their unflinching belief in centralised power stations.

Some experts insist there is another way. The City of Sydney highlighted one avenue this week with details of its plan to provide for its own energy needs through a network of co-generation and trigeneration plants.

Solar researcher David Mills presents another intriguing option that has provoked much interest. Last week’s exclusive story in Climate Spectator about his questioning the need for baseload power was the most read story on this website since it was launched in July (apart from our cheeky suggestion late that month that Malcolm Turnbull should form his own political party).

Some would say that a first world economy powered by the sun and the wind would be as improbable as Turnbull leaving the bosom of the Liberal Party, but people are clearly fascinated by the idea.

The study that Mills has completed with Weili Cheng and Phillippe Larochelle found that wind and solar could have covered – on an hour by hour basis – the entire electrical load for the US in 2006. No baseload required.

Mills gave further details on how this would work in his keynote address in Canberra on Wednesday night at the Australian Solar Energy Society’s conference, expanding on his idea of replacing the concept of baseload and peaking power with a new system based around flexible and inflexible energy mechanisms.

In Mills’ view, the task is to match higher-cost flexible technologies with lower-cost inflexible technologies, and in doing so he challenges the accepted view of energy sources by lumping  wind and solar PV in the same category as coal, gas and nuclear.

“The components in each of these two buckets – inflexible technologies and flexible technologies – must compete in price with each other, not with elements from the other bucket. They do different jobs,” he says.

Mills says inflexible technologies include not only technologies that can, or must, be run as baseload, such as coal, nuclear, and geothermal, but non-baseload technologies like non-storage photovoltaic, non-storage concentrating solar thermal and, of course, wind.

“It is logical that these technologies must compete with each other for the lowest price and best environmental outcome, but wind is already competitive against coal in much of the USA and is very low in emissions.

“An important outcome is that nuclear, geothermal, coal with sequestration and photovoltaic without storage have to compete against wind per kWh because they provide the same product – inflexible electricity output. This might be a real challenge for these technologies."

Mills says flexible technologies include intermediate peaking natural gas combined cycle plants, gas turbines, concentrating solar with thermal storage, peaking hydro, and photovoltaic with battery storage. Again these must compete with each other on price and environmental factors.

“Costs are dropping so quickly that we may be able to very soon construct an inflexible plus flexible combination from solar and wind at much the same levelised cost as current coal plus natural gas combined cycle systems in the USA, and perhaps for Australia as well," says Mills. "Wind is already there.”
 

Source: ABC Science

The diagrams above illustrate Mills’ argument. Diagram A shows the traditional baseload model. The blue baseload section is nearly flat, except when load drops at night below the baseload power output. The advantage of baseload is that the generator is working flat out most of the time and makes better economic use of its equipment. The middle orange section is called 'intermediate peaking' and it means a system that rises and fall slowly during the day and night to roughly match the rise and fall of electricity grid demand. It uses its equipment for fewer hours than baseload and this has a higher kWh cost.

“In the USA, most natural gas combined cycle plants are used for intermediate peaking,” Mills says. “If we didn't care about the cost of the gas fossil fuel, we would probably run natural gas combined cycle for both intermediate and baseload sections, because it delivers about half the emissions of coal. If you ran this system with every natural gas combined-cycle plant following the load, there would be no baseload in the system, but it would work perfectly well.

Mills says Diagram B shows his work using load data from 2006 to run models on an hour-by-hour basis. He says it shows that demand can be met using a combination of inflexible technologies (in this case wind) topped up with flexible technologies (in this case solar).

“The wind is mostly uncontrolled (the only thing you can do is turn the wind generator on or off) and the concentrating solar thermal plants are equipped with low cost thermal (heat) storage like the plants recently installed in Spain, which can follow the grid load.

“The solar output in the figure rises and falls to balance the total output with the grid demand and takes the place of both intermediate peaking and fast peaking. The essential load-matching function is performed by the solar thermal storage.

“In such a wind/solar scenario, wind does not fit the traditional baseload paradigm. Wind is, in fact, cheaper as an uncontrolled variable source, rather than as a baseload source, because adding electrical storage like an expensive battery to make the output flat would increase its cost per kWh hugely.

“But – and this is important – wind, like baseload, is still inflexible because the output cannot be changed, short of shutting down the plant; neither wind, nor coal, nor nuclear can follow the load without changing the technology and increasing the kWh cost.”

On this basis, Mills argues that it is not appropriate to compare the cost of solar to coal if solar has energy storage, because it is in the wrong bucket. He says it is appropriate, however, to compare the costs of concentrating solar thermal with storage against a combination of natural gas combined-cycle and peaking gas turbines, and he notes that gas peaking plants are extremely expensive.

“This new way of thinking is quite general: it is actually possible to construct a generating system using any inflexible system partnered with any flexible system, such as nuclear with concentrating solar thermal, or wind with gas turbines,” he says.

“However, baseload is no longer a relevant prerequisite for a modern generating system.

“Matching of inflexible and flexible low-emissions technologies is much more a core requirement, and something that is not reflected in current government policy. With the huge resources of wind and solar available, and the need for low-carbon solutions, it is clear what the pillars of the new system must be.”