Radical plan to produce power from evaporation of lakes could provide an almost endless source of energy

A miniature version of the engine was first developed by scientists in 2015
It could be scaled up to cover 70% of the US's energy production from that year
It could yield between 2W and 10W per square metre, three times wind power
By covering water supplies with generatros this would help to conserve them

By Mark Prigg For Dailymail.com and Tim Collins For Mailonline

Published: 17:33 EST, 26 September 2017 | Updated: 05:26 EST, 27 September 2017

e-mail

101

View
comments

'Evaporation engines' could be the key to providing a reliable and renewable source of energy to much of the world.

Water released over lakes and reservoirs by the sun's energy could drive power production, while at the same time conserving the resources they cover, a new study claims.

Researchers created a miniature 'evaporation engine' machine to prove their theory, and used calculations to scale up the results.

They found that their approach could generate three times the power of a wind farm that covered a similar sized area.

Scroll down for video

Evaporation could hold the key to providing a reliable renewable source of energy to much of the world, a new study has found. Water released over lakes and reservoirs by the sun's energy could drive power production, while at the same time conserving the resources they cover

Researchers at Columbia University found that US lakes and reservoirs could generate 325 gigawatts of power.

That is nearly 70 per cent of what the United States produced in 2015.

They made the finding using their Evaporation Engine, a small scale version of what could one day become an industrial sized evaporation power plant.

In a 2015 paper, Dr Sahin showed how this basic process can be exploited to do work.

The current study was designed to test how much power this process could theoretically produce.

The team estimates that natural evaporation could yield between 2W and 10W per square metre.

This is around three times as much as conventional wind power, according to the researchers, and more than coal.

It would however require every standing body of water larger than 0.04 square miles (0.1 sq km), excluding the Great Lakes, in 48 US states to be covered with the devices.

Covering Lake Windermere in Cumbria could generate enough power for 65,000 homes in the UK, around least 29.5MW.

'We have the technology to harness energy from wind, water and the sun, but evaporation is just as powerful,' says the study's senior author Ozgur Sahin, a biophysicist at Columbia.

'We can now put a number on its potential.'

Evaporation is nature's way of cycling water between land and air.

HOW IT WORKS

The Evaporation Engine, developed in 2015, controls humidity with a shutter that opens and closes, prompting bacterial spores to expand and contract.

The spores' contractions are transferred to a generator that makes electricity.

When water on the surface below evaporates, it drives piston-like back and forth motion.

When connected to a generator, that motion produces electricity.

The evaporation engine sits on the surface of water (blue) here. When water on the surface below evaporates, it drives piston-like back and forth motion. When connected to a generator, that motion produces electricity.

The current study was designed to test how much power this process could theoretically produce.

Researchers envisaged a larger version of the machine that uses a water-responsive plastic muscle to absorb moisture.

With its bottom and top shutters closed, the material expands and swells, turning a turbine.

This graphic shows how the process would work, with a water responsive muscle swelling to turn a turbine, before releasing moisture and starting the cycle again

At full capacity, the upper shutters open and lower shutters close.

This allows water to evaporate and restarts the cycle.

They estimate that natural evaporation can yield between 2W and 10W per square metre.

This is around three times as much as conventional wind power, according to the researchers.

Though still limited to experiments in the lab, evaporation-harvested power could in principle be made on demand, day or night.

This would overcome the problems of intermittent energy supplies plaguing solar and wind energy.

Another benefit of evaporation is that it can be generated only when needed.

Solar and wind power, by contrast, require batteries to supply power when the sun isn't shining and wind isn't blowing.

Batteries are also expensive and require toxic materials to manufacture.

'Evaporation comes with a natural battery,' said study lead author, Ahmet-Hamdi Cavusoglu, a graduate student at Columbia.

'You can make it your main source of power and draw on solar and wind when they're available.'

Evaporation technology can also save water.

The southern and western United States have the greatest capacity to produce evaporation-generated power from lakes and reservoirs, a new study in Nature Communications finds.

BENEFITS OF THE SYSTEM

Though still limited to experiments in the lab, evaporation-harvested power could in principle be made on demand, day or night.

This would overcome the problems of intermittent energy supplies plaguing solar and wind energy.

Another benefit of evaporation is that it can be generated only when needed.

Solar and wind power, by contrast, require batteries to supply power when the sun isn't shining and wind isn't blowing.

Batteries are also expensive and require toxic materials to manufacture.

Evaporation technology can also save water.

Covering the water contained in the lakes and reservoirs would help to protect it from evaporation.

In the study, researchers estimate that half of the water that evaporates naturally from lakes and reservoirs into the atmosphere could be saved during the energy-harvesting process.

In their model, that came to 25 trillion gallons a year, or about a fifth of the water Americans consume.

The UK's annual consumption is around 2.6 billion gallons.

Globally, we consume around 1056 trillion gallons of freshwater each year.

States with growing populations and sunnier weather can best capitalize on evaporation's capacity to generate power and reduce water waste, in part because evaporation packs more energy in warm and dry conditions, the researchers say.

Drought-prone California, Nevada and Arizona could benefit most.

The researchers simplified their model in several ways to test evaporation's potential.

They limited their calculations to the United States, where weather station data are readily accessible, but it could easily be applied elsewhere.

They excluded prime locations such as farmland, rivers, the Great Lakes, and coastlines, to limit errors associated with modeling more complex interactions.

They also made the assumption that technology to harvest energy from evaporation efficiently is fully developed.

Klaus Lackner, a physicist at Arizona State University who was not involved in the study, expressed support for the team's findings.

Lackner is developing artificial trees that draw carbon dioxide from the air, in part, by harnessing the power of evaporation.

Sahin and his colleagues previously created 'hygroscopy driven artificial muscles', or HYDRAs, by attaching bacterial spores to plastic tape. HYDRAs are artificial muscles that extend and contract in response to changing humidity. HYDRAs shown here power the evaporation engine by cyclically extending and contracting on the surface of water.

'Evaporation has the potential to do a lot of work,' he said.

'It's nice to see that drying and wetting cycles can also be used to collect mechanical energy.'

The researchers are working to improve the energy efficiency of their spore-studded materials.

They hope to eventually test their concept on a lake, reservoir, or even a greenhouse, where the technology could be used to simultaneously make power and limit water loss.

The full findings of the study are outlined in the September issue of Nature Communications.

THE CAR THAT'S POWERED BY EVAPORATED WATER

In their 2015 paper, the researchers unveiled the first rotary engine and even a tiny car powered by humidity.

It works using bacterial spore that expand when they become humid to drive an engine.

Inside the bacterial spores, water is confined to nanoscale cavities and depending on the humidity, large pressure changes are induced.

The breakthrough works using bacterial spore that expand when they become humid to drive an engine.

When water is applied, the tape changes its curvature in moist and dry conditions.

When multiple tapes are assembled in parallel they can lift weight against gravity.

The engines start and run autonomously when placed at air–water interfaces.

They generate rotary and piston-like linear motion using specially designed, biologically based artificial muscles responsive to moisture fluctuations.

The devices are put together piece by piece by hand. Shown here is the rotating part of the moisture mill.

The authors demonstrated that these engines can drive a mini car and power LEDs, highlighting the untapped capability of water in the environment to supply useful levels of power.

'Evaporation is a ubiquitous phenomenon in the natural environment and a dominant form of energy transfer in the Earth's climate,' Ozgur Sahin and colleagues wrote at the time.

'Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world.'