Solar pond pioneers tell their story

May 25, 2020

Services: Intyalheme

It’s often said that Cen­tral Aus­tralia has a strong his­to­ry of renew­able ener­gy inno­va­tion; a his­to­ry which is per­haps a lit­tle longer than you might imagine.

Back in the 1980s, what start­ed as a fun exper­i­ment in a back­yard swim­ming pool in Alice Springs, turned into a com­mer­cial ven­ture, lead­ing to projects all over Australia. 

The pool belonged to long-term Alice Springs res­i­dent and for­mer Con­nel­lan Air­ways pilot David Fred­erik­sen, usu­al­ly known as Fred­do. He enlist­ed the help of his friend — Amer­i­can physi­cist Bob Collins who worked at Pine Gap. Togeth­er they built Australia’s first solar pond. 

David Fred­do” Fred­erik­sen at the solar pond he built with Bob Collins in Alice Springs

Solar pond tech­nol­o­gy was pio­neered in Israel in the 1950s. By the ear­ly 80s it was show­ing signs of becom­ing eco­nom­i­cal­ly viable. It seemed a prac­ti­cal and rel­a­tive­ly straight­for­ward way to gen­er­ate pow­er for out­back Australia. 

The pond is made up of a salt gra­di­ent,” said Freddo. 

The bot­tom lay­er is a stor­age zone of sat­u­rat­ed brine (24%), with each lay­er get­ting less saline, and fresh water on top. Grav­i­ty holds each lay­er in place,” he said. 

Sun­shine hits the bot­tom, gets trapped in the stor­age lay­er, and then con­verts into con­vec­tive energy.” 

Once the salt has trapped the heat at the bot­tom of the pond, the hot water is piped into an evap­o­ra­tor and put through a process which pow­ers a gen­er­a­tor. The phe­nom­e­non was first dis­cov­ered about a cen­tu­ry ago. 

There’s a lake in Hun­gary that has a salt deposit at the bot­tom, and when peo­ple dived into it, they could feel a huge tem­per­a­ture change,” said Freddo. 

Moth­er Nature’s been doing it for thou­sands of years.”

Fred­do in the engine room

The small pro­to­type pool was built at Freddo’s home near the Château Horns­by vineyard. 

A gov­ern­ment min­is­ter was din­ing at the restau­rant and we invit­ed him to have a look at the Territory’s new ener­gy sys­tem,” said Freddo. 

He put his hand in, burnt him­self, said the f‑word, and put his hand in again,” he said. 

The Min­is­ter returned to Dar­win and in no time they were all over us like a rash!” 

The part­ners were then encour­aged to build a 40 metre by 40 metre in-ground solar pond near the vine­yard, 15 kilo­me­tres south of Alice Springs; now a res­i­den­tial area known as Con­nel­lan. There was enough pow­er gen­er­at­ed to pump water to the vine­yard and pro­vide the restau­rant and a home with electricity. 

We used to get lots of vis­i­tors such as politi­cians, sci­en­tists from all over the world, tourists, and school kids,” said Freddo. 

The 40m x 40m solar pond in the Alice Springs rur­al area. It no longer exists, but the wind­mill is still there

Large-scale pow­er pro­duc­tion from solar ponds wasn’t viable, but it was thought it could be an effec­tive way to pro­vide pow­er to remote com­mu­ni­ties, and save on diesel costs. 

How­ev­er, man­ag­ing the tech­nol­o­gy wasn’t as easy as it might have looked. 

It was like a fussy swim­ming pool. It had to be looked after each day,” said Freddo. 

Rab­bits and things like leaves would fall in, then we’d get an algae bloom run­ning across the pond, cre­at­ing a blind and block­ing sunlight.” 

Fred­do invent­ed a salt har­vest­ing machine to gath­er enough salt for the solar pond

There was also the issue of sourc­ing enough salt. 

The big pond need­ed up to 800 tonnes of salt, which was har­vest­ed from the salt lakes near Erl­dun­da, using a sim­ple but clever mechan­i­cal salt-har­vester invent­ed by Freddo. 

The need for dai­ly atten­tion and access to salt ren­dered solar ponds less than ide­al for bush communities. 

By this time, Fred­do had been shown a hot bore on a friend’s prop­er­ty in out­back Queens­land which opened up new possibilities. 

Bob Collins said the solar ponds had a big impact” on him, and were the rea­son he stayed in Alice Springs, lead­ing to a 50-year stint in the town. He only recent­ly moved to north­ern New South Wales.

Fred­do and I made a good com­bi­na­tion, as I learned a lot of prac­ti­cal skills from him and I think he gained the­o­ret­i­cal knowl­edge from me,” said Bob. 

The solar ponds were not a tech­ni­cal suc­cess, but the heat engine we devel­oped for it then led us to geot­her­mal work.”

Fred­do and Bob’s expe­ri­ence and knowhow were applied else­where. Most notably, they were part of the team which built the geot­her­mal pow­er plant at Birdsville, which ran suc­cess­ful­ly for three decades. The team includ­ed Jim Lawrence (diesel mechan­ic), Steve Sawyer (elec­tri­cal engi­neer) and Tony Greatorex (elec­tron­ic engineer).

I think the team of peo­ple that helped us with all these devel­op­ments gen­er­at­ed a lot of inter­est in renew­ables, and the real­i­sa­tion that local peo­ple could do amaz­ing things,” said Bob. 

Bob and Fred­do are still enthu­si­as­tic about renew­able ener­gy; but also prag­mat­ic about the role of solar as a per­cent­age of the total gen­er­a­tion capa­bil­i­ty in Alice Springs. 

In 1974 it was over­cast for a month,” said Freddo. 

So even if you have 70 or 80 per cent solar, you still need a back­up sys­tem. Solar is a fuel saver but it can only be num­ber one if you’ve got big bat­ter­ies,” he said. 

Vari­ety is the way to go.”

Bob is sim­i­lar­ly technology-agnostic. 

A lot of the work for the future of renew­ables will have to be in stor­age and a more robust, smarter grid,” he said. 

No sin­gle tech­nol­o­gy has all the answers. You have to be open and flex­i­ble in your thinking.”

Fred­do at his home in Alice Springs (2020) stand­ing beside his swim­ming pool, which is lined with solar pond liner!

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