Strange Science: water

Wednesday, 19 December 2012

Cloud forest trees drink water through their leaves

Dec. 12, 2012 — Tropical montane cloud forest trees use more than their roots to take up water. They also drink water from clouds directly through their leaves, University of California, Berkeley, scientists have discovered.

While this is an essential survival strategy in foggy but otherwise dry areas, the scientists say that the clouds the trees depend on are now disappearing due to climate change.

"The study highlights the vulnerability of this rare and already endangered ecosystem to climate change," said Todd Dawson, senior author of the study and UC Berkeley professor of integrative biology. Changes in cloud cover have already been correlated to declines and disappearances of cloud forest animal populations, such as frogs and salamanders.

The new study will be published next year in the journal Ecology Letters and is available online this month.

In tropical montane cloud forests, leaves are constantly bathed in clouds, making them wet. The leaves of the most common cloud forest trees drink this cloud water when water from the soil just isn't enough, said Greg Goldsmith, lead author of the study and a graduate student in Dawson's lab.

"Many cloud forests experience an annual dry season when the primary water source isn't rain, but rather, the moisture from the clouds," he said. "This is when the trees are most likely to draw water in through their leaves."

Working in Monteverde, Costa Rica, the researchers studied patterns of leaf wetness caused by the clouds by setting up small plastic "leaves" that use changes in the voltage of an embedded electrical circuit to detect wetness. Then, they installed miniature sensors on the branches of cloud forest plants to see whether or not water was entering leaves when they were wet.

"The textbooks teach us that water enters roots, moves up the trunk and into the branches, then finally exits the leaves. That's true, but it's not the whole story," Goldsmith said. "With our sensors, we observed water entering the leaves and actually moving back down the branches toward the trunk."

The research builds on previous work by Dawson, who demonstrated a similar phenomenon in California redwoods.

However, the study found that not all trees can drink the same amount of cloud water.

"The trees that are drinking the most water through their leaves may be more vulnerable to decreases in cloud cover resulting from rising temperatures," said Goldsmith, who received funding from a National Geographic Society Young Explorers Grant to conduct the research.

"The study provides a clear demonstration of the interactions between clouds and cloud forest plants and will serve as a cornerstone for future research on the effects of climate change on tropical montane cloud forest ecosystems," Dawson added.

In addition to funding from the National Geographic Society, Goldsmith was supported by a National Science Foundation Graduate Research Fellowship, a Smithsonian Institution Short-Term Fellowship and a Wang Family Fellowship from UC Berkeley.

UC Berkeley graduate student Nicholas J. Matzke is also a co-author of the report.

Editor's note: More information available at http://www.canopyintheclouds.com/

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Story Source:

The above story is reprinted from materials provided by University of California - Berkeley. The original article was written by Robert Sanders.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Gregory R. Goldsmith, Nicholas J. Matzke, Todd E. Dawson. The incidence and implications of clouds for cloud forest plant water relations. Ecology Letters, 2012; DOI: 10.1111/ele.12039

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Electricity from water mains: Inline hydropower system generates power from water pipelines

Dec. 10, 2012 — Generating electricity from water is not a new thing. Hydro power stations have already sprung up across the world in China, United States and Canada. However, scientists will not stop exploring advanced technologies for further improvement to benefit people's lives.

Recently, PolyU's Department of Building Services Engineering and the Water Supplies Department (WSD) of the Hong Kong Special Administrative Region Government have been working together to turn water mains into an alternative source of power.

Hong Kong has a network of water mains travelling over 7,800 km, which is comprehensively monitored by WSD using monitoring devices to make sure our water supply remain clean and well-maintained. Water mains need power for those devices. Conventionally, they are putting small turbines into our pipes to produce electricity from drinking water.

Our water main pipes present a real challenge. They are just one metre across and hold far less water volume and potential energy compared to giant water dams, say for example. In pushing the boundaries, specialists in hydrodynamics, mechanical engineering and renewable energy have created a highly efficient device in harnessing the power of water. The resulting turbine is small enough to fit into a pipe, and uses just a fraction of hydro-energy to generate about 80 volts, enough to power four compact fluorescent light bulbs.

The novel device consists of an external hydroelectric generator and highly efficient spherical water turbine which dips into flowing water and reclaims residual pressure. When water passes through, the turbine drives a central rotating shaft and a micro generator to produce electricity.

The key lies in a number of intelligent designs to extract more energy from flowing water. The 8-blade turbine would only take away a fraction of kinetic energy because it strikes an accurate balance between water volume, water pressure and consumption of hydrokinetic energy, which boosts efficiency without reducing the momentum of running water to guarantee a reliable water supply. Turbine blades are carefully sized to intersect the largest possible area of water flow and minimise water bypassing.

To achieve maximum power output, a revolutionary design made the central rotating shaft hollow on the inside to minimise energy losses when driving the generator and utilize the harvested energy in full. The team also made the water more energetic and produced a strong current with a special metal block placed at the centre of the pipe to compress and accelerate the water flow. To further protect our drinking water, the turbine does not have moving parts and does not need any lubricant to eliminate the slightest change of contamination.

The mini-hydro power has been put to test in a number of locations including underground pits and outdoor environments. The principal investigator, Prof. Hong-xing Yang from Department of Building Services Engineering commented, "We have made the water pipes self-sufficient." In full operation, an array of in-pipe turbines is expected to save 700kWh of electricity and reduce 560 kg of carbon dioxide emission per year.

It is not only a green innovation to further cut our reliance on coal-based power plants, but also an engineering triumph that gives WSD an easy access to electricity in areas without power grid, such as treacherous terrains and underground. "This technology also points to viable turbine solutions for waters that have little potential for energy generation," added Prof. Yang.