June 2nd 2018


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Articles from this issue:

COVER STORY The Greens: the political equivalent of bilgewater

EDITORIAL Malaysian election sends shockwaves across South-East Asia

GENDER AND SPORT Transgender playing in women's football league gains attention

CANBERRA OBSERVED Beyond tomorrow a bridge too far for politicians to plan

ENERGY Why renewables destabilise the power grid

LAW AND FREEDOM Exemptions: at issue with Dr Zimmermann

INTERNATIONAL AFFAIRS Behind the U.S.-North Korea rapprochement

INTERNATIONAL AFFAIRS Two to tango: Where to now for U.S. and China?

LIFE ISSUES So, is this not pro-life?

POLITICS AND CULTURE The West won the world but may lose its soul

MILITARY BIOGRAPHY Commanders: the men who resolve questions of life and death

HUMOUR

MUSIC Eurovision: Wailing and gnashing of teeth

CINEMA Superhero movies: A Chestertonian consideration

BOOK REVIEW A man for all seasons and hemispheres

BOOK REVIEW Mid-century gem of Catholic fiction

POETRY

LETTERS

ECONOMICS Vatican document nails some of the causes of the GFC

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ENERGY
Why renewables destabilise the power grid


by Peter Westmore

News Weekly, June 2, 2018

While advocates of renewable energy (for example, solar and wind power) extol their low carbon-dioxide emissions, the increased problems (and cost) caused by fluctuating power supply is rarely acknowledged.

South Australia's Tesla big battery

When Australia’s power supply was provided entirely by large base-load power stations, surplus generating capacity was built into the system.

This ensured that the large daily and seasonal variations in demand were managed by the relatively simple task of load-shedding, accompanied by use of fast-acting hydro-power generators in Tasmania and the Snowy Mountains.

Typically, power demand fluctuates on a daily basis with two peaks, one in the morning and one in the evening, higher demand during the day, and low demand at night. Hence, electric water heaters had a cheaper off-peak rate.

However, there are also large seasonal fluctuations superimposed on the daily variations. Power demand is highest in the heat of summer, when air-conditioning is widely used in homes and offices, and in the depth of winter, when electricity is widely used for heating purposes.

Intermittent supply

Renewable energy provided from wind and solar power is, of its nature, intermittent, as it depends on the availability of wind and sunlight.

Typically, generators located in windy areas produce power at around 30 per cent of their rated capacity, but the supply is intermittent. Solar electricity generation is even less efficient.

The problem with renewable electricity is that it requires batteries to store surplus energy that can then be returned to the grid when shortfalls occur. Even with advances in technology, batteries are expensive and, once discharged, cannot be used again until recharged.

Balancing supply and demand becomes increasingly difficult (and costly) as use of renewable energy increases.

For example South Australia, the state that has closed all its coal-fired power stations and has the highest reliance on renewables, built the world’s largest battery plant last year, a 100 megawatt/hour lithium-ion battery, at a cost of $150 million.

This was widely reported as a breakthrough development that paves the way for reliable renewable power.

In a widely reported speech at the launch of the Tesla-built 100 MWh battery complex on December 1 last year, then SA Premier Jay Weatherill called it “history in the making”. He added: “South Australia is now leading the world in dispatchable renewable energy, delivered to homes and businesses 24/7.

“While others are just talking, we are delivering our energy plan, making South Australia more self-sufficient, and providing back-up power and more affordable energy for South Australians this summer.

“The world’s largest lithium-ion battery will be an important part of our energy mix, and it sends the clearest message that South Australia will be a leader in renewable energy with battery storage.”

As base-load demand in SA is about 1.2 gigawatts, the plant would supply the South Australian grid with enough energy for about five minutes’ base-load operation before it went flat.

The intermittent supply from renewables affects not only the amount of power being supplied into the grid, but also its frequency. In Australia, domestic electricity is supplied at 240 volts alternating current, at a frequency of 50 Hertz (cycles per second).

Electrical equipment designed for use in Australia requires fixed voltage and almost constant frequency. Sudden variations in either voltage or current can cause electrical equipment to fail, sometimes catastrophically. To avert this contingency, the Australian Energy Market Operator is required to manage supply voltages and frequencies surprisingly closely.

The AEMO website says: “Australia’s power systems, including the interconnected National Electricity Market (NEM) power system, operate at a frequency range as close to 50 Hertz (Hz) as possible.

“At 50 Hz, and within a few hundred millihertz either side of 50 Hz, the power system safely and securely transmits power from generators to consumers. AEMO is required to keep frequency in the range 49.85 Hz and 50.15 Hz.”

It adds that if the frequency goes outside this range, the system doesn’t operate as it should. Generators, and large motors drawing power from the network, can start disconnecting to protect themselves against damage.

“If these disconnections are uncon­trolled and create more imbalance bet­ween demand and supply in the system, affecting frequency further, consumers can experience a full or partial blackout.”

AEMO has constantly to monitor the supply and demand in the system to prevent such failures.

“We coordinate generation coming into the system and demand going out so they are always balanced and frequency doesn’t go outside the set range.”

The complexity in managing supply into the grid when it is dependent on factors as variable as wind speed, cloud cover and sunlight helps to explain why no country in the world has been able to create a power system entirely on renewables, despite the lavish subsidies which have been provided over the past 15 years.




























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