Inventor creates incredible 100 mile to the gallon engine using 200-year-old Stirling technology

  • A man from Texas has built his device based on the Stirling engine
  • Dr Robert Stirling, a Scottish clergyman, invented the engine in 1818
  • Design combined Stirling engine with modern thermopile technology 
  • Inventor will test the engine by driving from East to West coast of US

For thrifty motorists, squeezing an extra few miles out of each gallon of fuel can become an obsession.

But some have been striving for a semi-mythical goal of achieving 100 miles per gallon of fuel from their vehicles.

Now an inventor in Texas claims to have built an engine that can reach this efficient milestone – using a design that is more than 200 years old.

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SUPER EFFICIENT CARS 

While most commercial cars can just about manage 60 miles to the gallon if driven carefully, engineers have been building some with truly staggering levels of efficiency.

French team MicroJoule have broken the world record for most efficient gasoline-powered vehicle three times.

In 1999 they managed to squeeze 9,845 miles out of just one gallon of fuel and then in 2001 they beat this with 10,227 miles per gallon.

In 2003 they set a new world record with 10,705 miles per gallon at the annual Shell Eco-Marathon competition.

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Josh MacDowell, combined a Stirling engine – first created by a clergyman in Scotland 200 years ago – with thermopile technology that converts heat energy into electricity.

Mr MacDowel, from San Antonia, Texas, is currently testing his invention in a Hybrid electric car, allowing it to drive at highway speeds without the need for recharging.

He believes the engine would also be capable of letting an SUV achieve 100 miles to the gallon. He is now hoping to patent his design. 

The Stirling engine was invented by Robert Stirling, a Scottish clergyman, in 1816, using the exchange of hot and cold air to power an engine.

Since then, his basic model has been used extensively, from sewing machines, to submarine engines.

Stirling's original 1816 patent contained all the elements of what is now called the 'Stirling cycle engine' – a power piston, a displacer to move air between hot and cold ends, and a regenerator.

The power piston compresses air in the cold end of the displacer cylinder, which then shifts the air from the cold to hot end. The piston is driven back by the air expanding in the hot end.

WHO WAS THE INVENTOR OF THE STIRLING ENGINE? 

Robert Stirling, who designed the famous Stirling engine, was a Scottish clergyman who lived in Perthshire in the 1800s

Robert Stirling, who designed the famous Stirling engine, was a Scottish clergyman who lived in Perthshire in the 1800s

The Reverend Dr Robert Stirling was a Scottish clergyman who lived in Perthshire in the 1800s.

He invented what he called the 'Heat Economiser' – a device for improving the thermal and fuel efficiency of a variety of industrial processes.

Stirling obtained a patent for his engine in 1816, however he described a number of additional applications for use in glass and other furnaces.

In 1818, Stirling built his first practical version of his engine, designed pump water from a stone quarry.

In the 1820s, he teamed up with his brother, James, who suggested that greater power output might be obtained using air pressures greater than atmospheric pressure.

The brothers received further patents in 1827 and 1840 for improvements to their air engine.

His original 1816 patent contained all the elements of what is now called the 'Stirling cycle engine' – a power piston, a displacer to move air between hot and cold ends, and a regenerator.

The power piston compresses air in the cold end of the displacer cylinder, which then shifts the air from the cold to hot end. The piston is driven back by the air expanding in the hot end.

Unfortunately, none of his experimental work of papers have survived, except two model engines, which now live in the Universities of Glasgow and Edinburgh.

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Robert Stirling's original design was called the 'Heat Economiser', a device for improving the thermal and fuel efficiency of a variety of industrial processes

Robert Stirling's original design was called the 'Heat Economiser', a device for improving the thermal and fuel efficiency of a variety of industrial processes

Internal combustion engines currently used in cars only use 14 per cent of the energy they produce, but Stirling's engine design can use almost 50 per cent, making them much more efficient.

Speaking to KHOU, Mr MacDowell said: 'I imagine in 20 years the only place you will see an internal combustion engine is on a Harley-Davidson motorcycle because people like the way they sound.'

Mr MacDowell's concept has received scientific backing by researchers at Texas A&M University.

Dr Mirley Balasubramanya, a mathematical physicist at Texas A&M University, said: 'This is a wonderful idea, why didn't someone else think of this?'

The Stirling engine used by Mr MacDowell came from Nasa, who experimented with one in vehicles in the early 1980s. Their experiments saw a Dodge pickup achieve roughly 54 miles per gallon.

While his current engine is used in a Hybrid electric car, Mr MacDowell believes he will have the Stirling engine running in a Ford F-150 pickup truck, getting at least 58 miles per gallon. 

The original Stirling engine was fairly bulky, but Mr MacDowell has redesigned his to look more like a small four cylinder engine.

In a Stirling engine, the power piston compresses air in the cold end of the displacer cylinder, which then shifts the air from the cold to hot end. The piston is driven back by the air expanding in the hot end

In a Stirling engine, the power piston compresses air in the cold end of the displacer cylinder, which then shifts the air from the cold to hot end. The piston is driven back by the air expanding in the hot end

Be claims this will allow him to put the engine in a smaller SUV, where he believes it could achieve at least 100 miles per gallon.

His next plan, is to use his current engine in an SUV, starting on the east coast of the US, and driving to California - a journey around 2000 miles long. 

However, with his engine, he believes he can make the trip on less than 40 gallons of fuel.

In the UK, the price of petrol is currently around £4.50 per gallon. If Mr MacDowell's predictions are correct, his journey would only cost around £180.  

On his journey, Mr MacDowell says he will put his vehicle together and document everything, then send his findings to the Southwest Research Institute in San Antonio to verify the results. 

Trying to describe just how significant this invention could be, Mr MacDowell said his design is to the Hybrid industry, what Diesel-electric locomotives were to steam engines.

If his journey across the US confirms his hypothesis, car companies may well be interested in his Stirling engine.

 

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