IP (Intellectual Property) Australia is the federal government agency charged with issuing patents for new inventions.

General manager, patents and plant breeder's rights, Victor Portelli, who has been with the agency for more than 26 years, said he had seen some odd things come through.

But the most talked about inventions were the perpetual motion machines.

"We constantly have people coming to us trying to prove that they have a machine that will run forever," Mr Portelli said.

IP Australia gets at least a couple of attempts to patent perpetual motion machines each year. Mr Portelli jokes the enthusiasm for such devices means the government might soon be out of money due to tax losses.

Unlikely. Since such an invention needs to violate the laws of nature to work IP Australia examiners routinely lodge objections to its patent.

"There are some weird and wonderful things that we get," Mr Portelli said. "We had an inventor who applied for a plane that could go under water with retractable wings and engines. That was an interesting one."

Not all inventions are so exotic.

Canberra roofing specialist Kevin Baker invented a ventilated tile that solved serious condensation problems in building roofs.

The idea sprung from a major job for airport mogul Terry Snow.

"They had massive condensation problems," Mr Baker said. "He had every engineer and god knows who to work out the condensation problem and he finally got on to me and said, 'I know you can fix the problem'."

The big problem was Mr Snow insisted on not having any kind of extraction device protruding from the roof.

"I thought it was an impossibility," Mr Baker said. "Anyway I went out to my daughter's horse-riding lesson and I was just sitting there and it came to me."

He fleshed out the idea and, with encouragement from Mr Snow, ended up patenting the idea. He would also win the New Inventors show on the ABC for the idea.

"I'm not a millionaire but I make a good living out of it," he said.