Cloud Seeding – A Silver Bullet For Super Cool Water

September 7th, 2010

Chris Booth, fresh tracks in Thredbo August 19, 2010. Image:: Dominic Kieler

Alpine Weather | Aaron Cook – Mountainwatch Alpine Meterologist

In a win-win situation for renewable energy and the Australian Ski Industry, scientists are giving nature a helping hand. Aaron Cook takes a look at cloud seeding.

For the last 100,000 years people have mostly left the weather up to the gods, the friendly local witch doctor, or pure dumb luck. But Australian meteorologists are now more certain than ever that they can change the weather on demand.

A massive experiment in the Snowy Mountains by hydro-electric generator Snowy Hydro has shown that releasing microscopic particles of a chemical called silver iodide into the atmosphere can coax up to 14 per cent more snow from passing weather systems.

The technique, called ‘cloud seeding’, has been around for over 50 years, but it has taken over six years of data collection for the Snowy Precipitation Enhancement Research Project (SPERP) to prove that it can lead to gains over the Snowy Mountains.

Charlie Timmins in the Thredbo Backcountry. Image:: Ben Hansen

Cloud seeding 101
The weather systems that pass over the snowy mountains are made up of clouds that contain large amounts of liquid water. The water in these clouds is very pure and can exist in a “super-cooled” liquid state well below zero degrees. But if a drop of this water comes into contact with a suitable piece of dust or clay, called an ice nucleus, it will freeze, creating a snowflake that rapidly sweeps up other water droplets and then falls from the cloud once it is too heavy.

The problem for snow-lovers is that these clouds often don’t contain enough ice nuclei to mop up all of the available water, and some of it escapes and evaporates as air flows down the other side of the ranges. (In the business they call these clouds “in-efficient”, but perhaps it’s never wise to use words to like that with nature.)

This is where cloud seeding comes in. Scientists add small amounts of a chemical called silver iodide to a gas burner on the western side of the ranges. The microscopic particles float up into the clouds and provide extra ice nuclei on which snowflakes can form, thereby increasing the amount of snow that falls to be enjoyed by skiers, renewable energy generators and eventually farmers downstream.

Snowfalls thanks to cloud seeding? Image:: Andrew Fawcett

A new hope
Snowy Hydro’s managing director Terry Charlton said the project provides hope to all stakeholders who depend on the snow. “This of course includes generation of additional renewable energy, as well as downstream farming communities in the Murray and Murrumbidgee catchments and of course the NSW ski industry, not to mention those plants and animals that depend on adequate winter snow cover for their survival,” he said.

The trial has been granted permission to continue seeding about 50 per cent of suitable weather systems until 2015 by the NSW Government. But David Harris, the executive officer for water at Snowy Hydro, said that with the results proven, the project should now move to full operation to seed all passing cold fronts.

Ski resorts in the Snowy Mountains have been quick to support this idea. The Australian Ski Areas Association released a statement on behalf of Perisher, Thredbo, Charlotte Pass and Selwyn Snowfields applauding the work so far. They have also contacted Minister for Primary Industries, Steve Whan to request changes to legislation to allow this.

Farmers and the Snowy Hydro Electric Scheme also rely on the benefits of cloud seeding. Image:: Alexander Evans

Easy money
SPERP cost $20 million over the first six years of operation, of which Snowy Hydro paid $16 million and the Federal Government paid $4 million. But the potential benefits to Snowy Hydro make it easy to see why they have bothered.

A spokesman for Snowy Hydro said the Snowy Hydro scheme could expect up to 70 billion litres of water extra per year from cloud seeding, which it could use to generate more electricity.

Because hydro-electric turbines can start up almost instantly, Snowy Hydro is able to maximise the price it receives for its power by timing its output for when electricity prices are most favourable.

Rough calculations made by Mountainwatch.com, based on information on Snowy Hydro’s website and the company’s latest annual report, show that every extra billion litres of water could generate electricity worth over $200,000. So the company, jointly owned by the NSW, Victorian and Federal Governments, stands to reap millions of dollars in extra generation revenue per year.

For more info on cloud seeding visit the Snowy Hydro Website.

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