One of the most striking features of Jupiter – a gaseous giant with no solid surface – is the coloured bands that encircle the planet.
These bands are so large and distinct that they can be seen from here on Earth using a modest telescope, and thus have fascinated astronomers since the era of Galileo.
In research published today in The Astrophysical Journal, Jeffrey Parker, from Lawrence Livermore National Laboratory in the United States, and I have developed a theory that could help explain what is going on beneath these bands and why they only go so deep into the planet.
Winds on Jupiter
These bands are actually strong steady winds, or jets, that flow in Jupiter’s atmosphere, carrying with them clouds of ammonia and other colourful elements. These jets are similar to the jet streams that flow high up in Earth’s atmosphere.
But there is more to these jets than meets the eye. What goes on below Jupiter’s clouds is, to a large extent, still a mystery.
Although there exist many theories for how the jets on Jupiter form and how deep they penetrate beneath the clouds, until recently we had no direct observations to support them.
In mid-2016, NASA’s spacecraft Juno headed to Jupiter with a mission to approach the planet closer that any probe has done before. It reached distances of less than 4,500km above Jupiter’s clouds at its closest approach (about the distance from New York to Los Angeles).
Upon arrival, Juno began to make precise measurements of Jupiter’s gravitational and magnetic fields.
This created a new puzzle for scientists: why do the jets penetrate as deep as they do, but no deeper?
Here is where our research comes into the picture. We have developed a theory that explains how magnetic fields have a tendency to shut down the jets.
What does this have to do with Jupiter?
Inside the gas giant
Jupiter’s gaseous bulk consists mostly of hydrogen and helium. As you go deep beneath the clouds into the interior, the pressure of the gas increases (similar to how the pressure increases when you dive deep into the ocean here on Earth).
Scientists understand that at about 3,000km below Jupiter’s clouds, the pressure is so high that electrons can get loose from the molecules of hydrogen and helium and start to move around freely, creating electric and magnetic fields.
Is it just a coincidence that this happens at about the same depth that the jets break down? Scientists speculate that it is not. As Steve Levin, Juno project scientist at NASA’s Jet Propulsion Laboratory, explains:
It’s very interesting that (the jets disappear at) about 3,000km, because that’s about where it might be conducting electricity enough to make a magnetic field.
So, it could be that the magnetic field has something to do with why the belts and zones only go that deep (…) But we don’t know this yet; this is just speculation.
Here is how our theory ties in. Using principles from statistical physics of turbulent systems, we devised a mathematical model which predicts that when magnetic fields are strong enough, the jets shut down.
Specifically, within our model a jet organises magnetic fluctuations in such a manner so that the coherent effect of these fluctuations acts to dampen the jet itself.
This offers a partial explanation as to why the jets terminate at about 3,000km below the clouds.
It’s hoped that theory and observation together will continue to give deeper insight on the physics of the universe as Juno and other probes, such as NASA’s new Parker Solar Probe, explore and gather data from our Solar system and beyond.
People who oppose wind farms often claim wind turbine blades kill large numbers of birds, often referring to them as “bird choppers”. And claims of dangers to iconic or rare birds, especially raptors, have attracted a lot of attention.
Wind turbine blades do indeed kill birds and bats, but their contribution to total bird deaths is extremely low, as these three studies show.
A 2009 study using US and European data on bird deaths estimated the number of birds killed per unit of power generated by wind, fossil fuel and nuclear power systems.
wind farms and nuclear power stations are responsible each for between 0.3 and 0.4 fatalities per gigawatt-hour (GWh) of electricity while fossil-fuelled power stations are responsible for about 5.2 fatalities per GWh.
That’s nearly 15 times more. From this, the author estimated:
wind farms killed approximately seven thousand birds in the United States in 2006 but nuclear plants killed about 327,000 and fossil-fuelled power plants 14.5 million.
In other words, for every one bird killed by a wind turbine, nuclear and fossil fuel powered plants killed 2,118 birds.
A Spanish study involved daily inspections of the ground around 20 wind farms with 252 turbines from 2005 to 2008. It found 596 dead birds.
The turbines in the sample had been working for different times during the study period (between 11 and 34 months), with the average annual number of fatalities per turbine being just 1.33. The authors noted this was one of the highest collision rates reported in the world research literature.
Raptor collisions accounted for 36% of total bird deaths (214 deaths), most of which were griffon vultures (138 birds, 23% of total mortality). The study area was in the southernmost area of Spain near Gibraltar, which is a migratory zone for birds from Morocco into Spain.
Perhaps the most comprehensive report was published in the journal Avian Conservation and Ecology in 2013 by scientists from Canada’s Environment Canada, Wildlife Research Division.
Their report looked at causes of human-related bird deaths for all of Canada, drawing together data from many diverse sources.
The table below shows selected causes of bird death out of an annual total of 186,429,553 estimated deaths caused by human activity.
Mark Duchamp, the president of Save the Eagles International is probably the most prominent person to speak out about bird deaths at wind farms. He says:
The average per turbine comes down to 333 to 1,000 deaths annually which is a far cry from the 2-4 birds claimed by the American wind industry or the 400,000 birds a year estimated by the American Bird Conservancy for the whole of the United States, which has about twice as many turbines as Spain.
Interest groups have regularly cited this endangered bird when trying to halt a range of developments.
These include a chemical storage facility and a boating marina. The proposed Westernport marina in Victoria happened to also be near an important wetland. But a professor in biodiversity and sustainability wrote:
the parrot copped the blame, even though it had not been seen there for 25 years.
Victoria’s planning minister at the time, Rob Hulls, described the Bald Hills decision as blatantly political, arguing the federal conservative government had been lobbied by fossil fuel interests to curtail renewable energy developments. Hulls said there had been:
some historical sightings, and also some potential foraging sites between 10 and 35 kilometres from the Bald Hills wind farm site that may or may not have been used by the orange-bellied parrot.
Perhaps the final word on this topic should go to the British Royal Society for the Protection of Birds. It built a wind turbine at its Bedfordshire headquarters to reduce its carbon emissions (and in doing so, aims to minimise species loss due to climate change). It recognised that wind power is far more beneficial to birds than it is harmful.
Simon Chapman and Fiona Crichton’s book, Wind Turbine Syndrome: a communicated disease, will be published by Sydney University Press later this year.
Last week, Sydney radio announcer Alan Jones lambasted those concerned about climate change and what he called “renewable energy rubbish”.
Jones has been loose with the facts in the past, having been Factchecked in 2015 after confusing kilowatts with megawatts and quoting a cost for wind power he later confessed “where the 1502 [dollars per megawatt hour that he stated] comes from, I have absolutely no idea”.
Jones, who chaired the much hyped but poorly attended 2013 national rally against wind farms in June 2014 (see photo) told his listeners last week wind farms are “buggering up people’s health”.
Their report predictably savaged wind farms, while Labor Senator Anne Urquhart’s minority report was the only one I found to be evidence-based.
Jones then went on to interview Dr Mariana Alves-Periera, from the private Lusophona University in Portugal (world university ranking 1,805, and impact ranking 2,848) whom he described as a distinguished international figure.
She was “recognized internationally” and had published “over 50” scientific papers over 30 years, something of a modest output. Jones, who may or may not have read any of these publications, told listeners her findings were “indisputable”, there was “no opposing scientific evidence” and again in emphasis, “none of [her papers] have been disputed” to which Alves-Periera agreed instantly “no they haven’t”.
This is an interesting interpretation of the scientific reception that has greeted the work of the Lisbon group on the unrecognized diagnosis of “vibroacoustic disease” (or VAD), a term they have made their own.
I first encountered Alves-Periera when she spoke via videoconference to a NHMRC meeting on wind farms and health in 2011. She spoke to a powerpoint presentation which highlighted the case of a schoolboy who lived near wind turbines. Her claim was the boy’s problems at school were due to his exposure to the turbines, as were cases of “boxy foot” in several horses kept on the same property.
Intrigued by this n=1 case report, I set out with a colleague to explore the scientific reception that “vibroacoustic disease” had met. We published our findings in the Australian and New Zealand Journal of Public Health 2013.
We found only 35 research papers on VAD. None reported any association between VAD and wind turbines. Of the 35 papers, 34 had a first author from the Lusophona University-based research group. Remarkably, 74% of citations to these papers were self-citations by members of the group.
In other words, just shy of three quarters of all references to VAD were from the group who were promoting the “disease”. In science, median self-citation rates are around 7%. We found two unpublished case reports from the group presented at conferences which asserted that VAD was “irrefutably demonstrated” to be caused by wind turbines. We listed eight reasons why the scientific quality of these claims were abject.
In 2014 Alves-Periera and a colleague defended their work in a letter to the journal and I replied. They described themselves as the “lead researchers in vibroacoustic disease”. But as we had shown, they are almost the only researchers who were ever active on this topic, with self-citation rates seldom seen in research.
Other experts have taken a different view of the group’s work. One of the world’s leading acousticians Geoff Leventhall who also spoke at the NHMRC’s 2011 meeting, wrote in a 2009 submission to the Public Service Commission of Wisconsin about the Lisbon group’s VAD work.
The evidence which has been offered [by them] is so weak that a prudent researcher would not have made it public.
disease itself has not gained clinical recognition.
Leventhall concluded his review by saying:
One is left with a very uncomfortable feeling that the work of the VAD group, as related to the effects of low levels of infrasound and low frequency noise exposure, is on an extremely shaky basis and not yet ready for dissemination. The work has been severely criticised when it has been presented at conferences. It is not backed by peer reviewed publications and is available only as conference papers which have not been independently evaluated prior to presentation.
Jones told his listeners the reason wind turbines are not installed on Bondi Beach, down Sydney’s Macquarie Street or Melbourne’s Collins Street was because governments “know they are harmful to health”. His beguiling logic here might perhaps also be the same reason we don’t see these iconic locations given over to mining or daily rock concerts. Most people would understand there are other factors that explain the absence of both wind turbines, mines or daily rock concerts in such locations.
Jones has given air time to a Victorian woman who is a serial complainant about her local wind farm and who has written:
Around the Macarthur wind farm, residents suffer from infrasound emitted by the turbines, even when they’re not operating.
At a time when we are seeing unparalleled increases in renewable energy and reductions in fossil fuels all over the world, one wonders why this is still public discussion in Australia.
Across the world, solar photovoltaics (PV) and wind are the dominant clean energy technologies. This dominance is likely to become overwhelming over the next few years, preventing other clean energy technologies (including carbon capture and storage, nuclear and other renewables) from growing much.
As the graph below shows, PV and wind constitute half of new generation capacity installed worldwide, with fossil, nuclear, hydro and all other renewable energy sources making up the other half. In Australia this dominance is even clearer, with PV and wind constituting virtually all new generation capacity.
Moreover, this trend is set to continue. Wind and PV installation rates grew by 19% in 2015 worldwide, while rates for other technologies were static or declined.
PV and wind dominate because they have already achieved commercial scale, are cheap (and set to get cheaper), and are not constrained by fuel availability, environmental considerations, construction materials, water supply, or security issues.
In fact, PV and wind now have such a large head start that no other low-emission generation technology has a reasonable prospect of catching them. Conventional hydro power cannot keep pace because each country will sooner or later run out of rivers to dam, and biomass availability is severely limited.
Both wind and PV access massive economies of scale. Their ability to saturate national electricity markets around the world severely constrains other low-emission technologies. Some of the other technologies may become significant in some regions, but these will essentially be niche markets, such as geothermal in Iceland, or hydro power in Tasmania.
Around 80% of the energy sector could be electrified in the next two decades, including electrification of land transport (vehicles and public transport) and electric heat pumps for heat production. This will further increase opportunities for PV and wind, and allows for the elimination of two-thirds of greenhouse gas emissions (based upon sectoral breakdown of national emissions data).
Storage and integration
What about the oft-cited problems with the variable nature of photovoltaics and wind energy? Fortunately, there is range of solutions that can help them achieve high levels of grid penetration.
While individual PV and wind generators can have very variable outputs, the combined output of thousands of generators is in fact quite predictable when coupled with good weather forecasting and smoothed out over a wide area.
What’s more, PV and wind often produce power under different weather conditions – storms favour wind, whereas calm conditions are often sunny. Rapid improvements in high-voltage DC transmission allows large amounts of power to be transmitted cheaply and efficiently over thousands of kilometres, meaning that the impact of local weather is less important.
Another option is “load management”, in which power demands for things like domestic and commercial water heating, and household and electric car battery charging, are moved from night time to day to coincide with availability of sun and wind. Existing hydro and gas or biogas generators, operated for just a small fraction of the year, can also help.
Finally, mass power storage is already available in the form of pumped hydro energy storage (PHES), in which surplus energy is used to pump water uphill to a storage reservoir, which is then released through a turbine to recover around 80% of the stored energy later on. This technology constitutes 99% of electricity storage worldwide and is overwhelmingly dominant in terms of new storage capacity installed each year (3.4 Gigawatts in 2015).
Australia already has several PHES facilities, such as Wivenhoe near Brisbane and Tumut 3 in the Snowy Mountains. All of these are at least 30 years old, but more can be built to accommodate the storage needs of new wind and PV capacity. Modelling underway at the Australian National University shows that reservoirs containing enough water for only 3-8 hours of grid operation is sufficient to stabilise a grid with about 90% PV and wind – mostly to shift daytime solar power for use at night.
This would require only a few hundred hectares of reservoirs for the Australian grid, and could be accomplished by building a series of “off-river” pumped hydro storages. Unlike conventional “on-river” hydro power, off-river PHES requires pairs of hectare-scale reservoirs, rather like oversized farm dams, located in steep, hilly, farm country, separated by an altitude difference of 200-1000 metres, and joined by a pipe containing a pump and turbine.
In Australia, if wind and PV continue at the installation rate required to reach the 2020 renewable energy target (about 1 GW per year each), we would hit 50% renewable electricity by 2030. This rises to 80% if the installation rates double to 2 GW per year each under a more ambitious renewable energy target – the barriers to which are probably more political than technological.
PV and wind will be overwhelmingly dominant in the renewable energy transition because there isn’t time for another low-emission technology to catch them before they saturate the market.
Wind, PV, PHES, HVDC and heat pumps are proven renewable energy solutions in large-scale deployment (100-1,000 GW installed worldwide for each). These technologies can drive rapid and deep cuts to the energy sector’s greenhouse emissions without any heroic assumptions.
Apart from a modest contribution from existing hydroelectricity, other low-emission technologies are unlikely to make significant contributions in the foreseeable future.
By 2030 renewable energy sources such as solar and wind will cost a similar amount to fossils fuels such as coal and gas, thanks to falling technology costs, according to new forecasts released in the CO2CRC’s Australian Power Generation Technology (APGT) Report.
The report also shows that technology costs will fall faster under climate policies that limit the concentration of carbon dioxide in the atmosphere to 450 parts per million. (The current CO₂ concentration is around 400 parts per million).
While the practice of forecasting is often derided, with multi-billion dollar assets that can last 50 years or more, the electricity industry and the policy-makers, academics and stakeholders who study it have no choice but to get involved.
Updating the data
A key input to all energy crystal-ball gazing is the cost of generating electricity, and performance data. However the last comprehensive update of electricity generation costs was the then Bureau of Resource and Energy Economics’ Australian Energy Technology Assessment (AETA) in 2012 (followed by a minor update to selected data in 2013).
The lack of consistent up–to-date data disadvantages technologies such as solar photovoltaic power systems whose costs have been improving rapidly since then.
To avoid misrepresenting the possible future role of fast-moving technologies, many analysts have had to slowly abandon use of the old data and create their own more up-to-date estimates.
While diverse opinions are sometimes useful, a proliferation of inconsistent alternative cost data sets creates confusion for the industry as it makes each published study less comparable.
The delivery today of a new and consistent electricity cost data set therefore is an important and long awaited addition to the electricity industry’s toolkit. The new report was conducted over the July-November period and utilised an electricity industry reference group of around 40 organisations to provide input and feedback along the way.
Given the often heated debates in Australia around energy sources, the CO2CRC recognised that it is crucial that studies like these are conducted in an open and unbiased manner.
The report includes key “building block” data such as capital and operating costs, and performance data such as emissions intensity, water usage and expected usage rates.
The cost of energy
Whenever a new electricity generation technology cost and performance data set is created there is an opportunity to update our view of the relative competitiveness of each technology.
This is calculated using a measure called the Levelised Cost of Electricity (LCOE). The LCOE captures the average cost of producing electricity from a technology over its entire life. It allows the comparison of technologies with very different cost profiles, such as solar photovoltaic systems (high upfront cost, but very low running costs) and gas-fired generators (moderate upfront cost, but significant ongoing fuel and operation costs).
The LCOE is the best technology comparison measure available but is not without limitations. It cannot recognise the different roles technologies might play in an electricity system (e.g. such as supplying everyday, baseload power, or power for periods of peak demand) or the relative flexibility of plant to increase or decrease power supply as needed.
Accepting the limitations, the updated LCOE analysis finds that in 2015 natural gas combined cycle and supercritical pulverised coal (both black and brown) plants have the lowest LCOEs of the technologies covered in the study. Wind is the lowest cost large-scale renewable energy source, while rooftop solar panels are competitive with retail electricity prices.
It is interesting to note that all 2015 LCOE estimates are higher than the current wholesale price of electricity of around A$40 per Megawatt-hour. The reflects reduced demand in the electricity network, which is putting downward pressure on electricity prices.
By 2030 the LCOE ranges of both conventional coal and gas technologies as well as wind and large-scale solar converge to a common range of A$50 to A$100 per megawatt hour. This outcome is consistent with observations from many commentators noting that the continuing reductions in wind and solar photovoltaic costs must inevitably lead to an intersection with the costs of the existing mature technologies before too long.
Of course, equality in LCOE will not necessarily translate to an equal competitive position in electricity markets, given differences in the flexibility of renewable and conventional coal and gas plants (which LCOE does not capture as already noted).
Falling technology costs
The convergence of conventional and renewable energy costs depends on the capital costs of these energy sources. These were modelled for the new report by CSIRO’s Global and Local Learning Model. This model is a relatively objective way of projecting costs based on historical learning rates. Learning rates show that for each doubling of installed capacity of an energy source, costs fall by a particular amount.
We can model these costs across different climate policies, as you can see in the chart below.
CSIRO’s projections included carbon price signals consistent with either concentration of 550 parts per million or 450 parts per million of greenhouse gas emissions. However, we found the total amount of cost reduction was fairly similar, but more accelerated in time, by approximately five years, in the 450 ppm case.
With the future policy environment of the electricity industry potentially becoming a little clearer after the COP21 meeting in Paris next week, the new report makes the job of understanding the role of different technologies in that future a little easier.
At the centre of claims about wind farms allegedly causing health problems is the infrasound that wind turbines generate as they turn in the wind.
Infrasound is sound below 20Hz, which is generally inaudible. Wind turbines are just one source of artificial man-made infrasound. Others include power stations, industry generally, motor vehicle engines, compressors, aircraft, ventilation and air conditioning units, and loudspeaker systems. Everyone living in an urban environment is bathed in infrasound for most of their lives.
As I sit at my inner Sydney desk writing this I’m copping infrasound from the planes that pass some 200-300 metres over my house sometimes many times an hour, the sound of passing road traffic on a quite busy road 100 metres from our house, and the stereo system I listen to as I write. Don’t tell anyone, but I feel fine and I’ve lived here 25 years.
But infrasound is generated by natural phenomena too. These include rare occurrences such as volcanoes and earthquakes, but also sources like ocean waves and air turbulence (wind) that countless millions, if not billions, are exposed to on most days. Anyone living close to the sea is surrounded by constant infrasound from waves.
The inclusion of wind as a source of infrasound is of particular significance to claims made that wind turbine-generated infrasound is noxious. In a Polish research paper published in 2014, the authors set out to measure infrasound from wind turbines and to compare that with naturally occurring infrasound from wind in trees near houses and from the sound of the sea in and around a house near the seaside.
The researchers used the average G-weighted level (LGeq) over the measurement period. This is the standardised measurement of infrasound which approximately follows the hearing threshold below 20Hz and cuts off sharply above 20Hz.
The infrasound levels recorded near 25 100-metre high wind turbines ranged from 66.9 to 88.8 LGeq across different recordings. Those recording infrasound in noise from wind in a forest near houses ranged from 59.1- 87.8 LGeq. The recordings of sea noise near seaside houses ranged from 64.3 to 89.1 LGeq. These infrasound levels were thus very similar cross the three locations.
The peak 88.8 LGeq was recorded very close to the turbines – virtually directly under the blades. The lower 66.9LGeq was 500m away, which is more like a common scenario for the nearest residences to turbines. Similarly, for the other sources, highest levels were nearest the source.
Wind is, of course, a prerequisite for wind turbines to turn and generate their mechanical infrasound. Here, the Polish authors noted that:
natural noise sources … always accompany the work of wind turbines and in such cases they constitute an acoustic background, impossible to eliminate during noise measurement of wind turbines.
This is a fundamentally important insight: wherever there are wind turbines generating infrasound, there is also wind itself generating infrasound. And it is impossible to disentangle the two. Indeed, every time I’ve been near wind turbines, easily the most dominant sound has been that of the wind buffeting my ears.
They reported that in urban settings, measured infrasound ranged between 60-70 decibels. In fact, at two locations – the EPA’s own offices and an office with a low frequency noise complaint – building air conditioning systems were identified as significant sources of infrasound. These locations exhibited some of the highest levels of infrasound measured during the study.
This study concludes that the level of infrasound at houses near the wind turbines assessed is no greater than that experienced in other urban and rural environments, and that the contribution of wind turbines to the measured infrasound levels is insignificant in comparison with the background level of infrasound in the environment.
Wind farm opponents claim infrasound is the cause of this Old Testament-like plague of plagues (now numbering 244 different problems). If that were true, how is it that hundreds of thousands of Australians who are daily exposed to infrasound in cities, in their houses surrounded by dastardly infrasound-generating fans, air conditioners and stereo systems, and those who live near trees or the sound of the ocean aren’t breaking down the door of those sworn enemies of infrasound Senators John Madigan, Nick Xenophon, Chris Back, David Leyonhjelm and Bob Day who brought us their scathing report on wind farms in June?
The explanation lies in factors we recognise frequently in risk-perception studies, popularised by Peter Sandman. Sandman has produced matrices of factors which have been often found to be associated with increased levels of community “outrage” about putative environmental threats to health.
Sandman distinguishes primary from additional factors, with primary factors being those which have been shown to be more strongly associated with increased levels of community concern.
I applied these to a case study of mobile phone tower complaints in the 1990s. I’ve now constructed the table below indicating the likely applicability of these factors to the case of predicting community worry about wind farms.
People don’t worry about infrasound in wind, trees and ocean waves because these sources are natural, while the same levels of infrasound from wind turbines are considered quite differently as they are sourced from what anti-wind farm activists like to call evil “industrial” wind farms.
The rare examples of people complaining who host wind turbines on their land for rental payment, compared with the far more common situation of non-hosting neighbours complaining, illustrates the voluntary vs coerced exposure factor, as well as the fair vs unfair factor. Those not benefiting from lucrative rental payments because of unsuitable local topography, while near neighbours can, understandably feel this as unfair.
Wind turbines are very memorable and exotic (a new experience to many), while wind in trees or the pounding of the ocean is very familiar and unremarkable, both factors likely to greatly diminish concerns.
Table: Primary and additional components predicting community outrage about putative environmental risks to health: the case of wind turbines. (two ticks = applies strongly to wind turbines; one tick = likely to apply less strongly)
The 2015 Senate (majority) report into wind farms roundly rejected the idea that psychosocial factors such as nocebo effects were largely responsible for the challenging historical and geographical variance in wind farm complaints. A nocebo effect is the opposite to a placebo effect: instead of exposure to an inactive agent making people feel better because of belief that it will, nocebo effects are when a benign agent makes people feel worse because they have been told it will.
The Committee, chaired by avowed wind farm opponent John Madigan, was emphatic that infrasound was the culprit but did not produce convincing evidence for this.
If the committee is sincere in its concerns about the health effects of infrasound, will we soon learn of a new inquiry about the pernicious and unappreciated dangers of living near the sea or trees, having air conditioners, stereos, ceiling fans, or travelling in motor vehicles?