The Base-Load Myth
To every complex problem there is a simplistic response, which is usually wrong. For instance, to the challenge of generating all of Australia’s electricity from renewable energy, the deniers repeatedly utter the simplistic myth that renewable energy is intermittent and therefore cannot generate base-load (that is, 24-hour) power.
However, detailed computer simulations, backed up with actual experience with wind power overseas, show that the scoffers are wrong.
Several countries, including Australia with its huge renewable energy resources, could make the necessary transition to an electricity generation system comprising 100% renewable energy over a few decades.
Case studies include the UK http://www.zerocarbonbritain.org, Europe www.erec.org, Germany Klaus 2010. Energieziel 2050: 100% Strom aus erneuerbaren Quellen, Denmark Energy, 34: 524–31, northern Europe International Journal of Energy Research, 32: 471–500, New Zealand Energy, 34: 524–531], and the whole world Energy Policy 39:1154-1190; Int. J. of Global Energy Issues, 13, nos 1-3; http://www.ecofys.com/com/publications/The-Energy-Report-Ecofys.htm.
Supplying base-load power is not a major obstacle.
Firstly, nighttime demand is low compared with daytime demand. This base-load demand could be further reduced by improving efficiency of energy use and by the forthcoming phase-out of electric off-peak hot water and its replacement with solar hot water and instantaneous gas.
This is the reverse of previous policies, which deliberately encouraged an increase in nighttime demand to allow inflexible coal-fired stations to generate 24/7.
Secondly, some renewable energies are just as reliable sources of base-load electricity as coal, while being 50 times less greenhouse polluting. These include bio-electricity generated from burning the residues of crops and plantation forests, concentrated solar thermal power with low-cost thermal storage, and hot-rock geothermal power.
Of these, bio-electricity from residues is ready for rapid growth. It already contributes to both base- and peak-load power in parts of Europe and the USA.
Several different types of concentrated solar thermal power are already in limited mass production in Spain and California.
However, we still need several years of experience with different types of collectors, heat-storage and heat-transfer systems before choosing second-generation systems for mass production. Meanwhile Australia should implement a feed-in tariff for large-scale solar, to can gain experience, optimize systems and then move into local manufacture of the best designs.
Hot-rock geothermal power is being demonstrated on a small-scale in France, Germany, the USA and will soon be demonstrated in Australia.
Until solar thermal power with thermal storage is ready to be rolled out rapidly, the cheapest renewable electricity option for replacing several coal-fired power stations is one of the so-called “intermittent” sources, wind power, a fully commercial technology.
Wind supplied the biggest contributions to new generating capacity in Europe in 2008 and 2009. It already provides 24% of Denmark’s electricity generation and over 14% of Spain’s and Portugal’s.
It’s undergoing enormous growth in China, which doubled its wind generating capacity each year during 2006-2009.
So, what about intermittency? There is no doubt that the output from a single wind farm fluctuates greatly. However, the fluctuations in the total output from a number of wind farms, which are geographically distributed in different wind regimes, are much smaller and partially predictable.
Modeling (see below) shows that it’s relatively inexpensive to lift the reliability of the total wind output to a level equivalent to a coal-fired power station by adding a few low-cost peak-load gas turbines that are operated infrequently.
Even in the absence of renewable energy power stations, electricity supply systems are designed to handle fluctuations in supply and demand. A power station or a transmission line may break down. An advertising break in a popular TV show may result in millions of kettles being switched on.
These fluctuations are handled by peak-load plants, such as hydro and gas turbines, that can be switched on and off quickly, and by reserve base-load plants that are kept hot. Up to a point, these existing back-up systems can also handle fluctuations in wind and solar power without storage.
With large amounts of wind and solar photovoltaic capacity in the grid, some additional peak-load plant may be required.
Gas turbines (essentially jet engines) are suitable because they can be turned on and off quickly, have low capital costs and, provided they are not operated a lot, have low fuel costs. They are reliability insurance with a low premium. They can be fuelled by gas or preferably biofuels produced sustainably.
Feasibility has been established by computer simulations of electricity generation systems by several research groups around the world, including my own in CSIRO in 1980s.
See “The Base-Load Fallacy” http://www.energyscience.org.au/factsheets.html and the book “Renewable Energy and the Grid” edited by Godfrey Boyle, Earthscan 2007.
Two recent detailed studies, funded by the National Renewable Energy Laboratory in the USA, found that wind power could supply 20-30% of electricity, given improved transmission links and a little low-cost flexible back-up [see http://www.nrel.gov/wind/systemsintegration/ewits.html and http://www.nrel.gov/wind/systemsintegration/wwsis.html ].
So a plausible Australian scenario for the next decade is the phase-out of several coal-fired power stations simultaneously with a rapid growth in efficient energy use, solar hot water, wind power and bio-electricity.
These clean technologies would buy us time to commercialise solar thermal and possibly geothermal power and then integrate them on a large scale in the 2020s as the remaining coal stations are shut down. Thus Australia could achieve a sustainable electricity system.
Clearly this solution is more complex and subtle than simplistic statements from renewable energy deniers that “The Sun doesn’t shine at night and the wind doesn’t blow all the time” and false statements that “Renewable energy cannot supply base-load power”.
In reality, there several renewable electricity technology options with different statistical properties. There is also the prospect of substantial modifications of demand by means of ‘smart grids’.
A mix of sources with appropriate transmission links and “smart grids” could provide a reliable system of 100% renewable electricity.
Such a system supersedes the concept of ‘base-load’. The important thing is not the reliability of one type of energy source, such as wind or solar, but the reliability and sustainability of the whole supply-demand system.
[Associate Professor Mark Diesendorf is Deputy Director of the Institute of Environmental Studies at UNSW. His latest book is Climate Action: A campaign manual for greenhouse solutions. This article first appeared in Online Opinion].