Sustainability

Image: Aahrus University

Scientists in Denmark have developed a storage technology that utilizes large underground water balloons and the pressure of the soil to activate a turbine to generate power. They are currently building a first 10 m x 10 m demonstrator to select critical technologies related to the membrane and to the construction of the “movable hill” that will form the terrain part of the battery.

From pv magazine

Researchers from the Aarhus University in Denmark have conceived an energy storage technology to store large amounts of power from renewable energy sources such as wind and solar.

The scientists said the new technology is similar to pumped-hydro storage, as it uses water as a storage medium and responds to the same basic mechanism, but explained that it can be used in a flat country such as Denmark, where no hydropower plants have ever been built. The new tech uses surplus power from wind and photovoltaics to pump water from a reservoir into giant underground water balloons.

According to AquaNamic, which is a Danish startup partnering on the project, a full-scale balloon may reach a size of 330 m x 330 m and, when buried under thousands of cubic meters of soil, can be raised up to 14 meters when the balloon is filled up with water in the charging phase. This balloon would reportedly have a storage capacity of 230 MWh. In the discharging phase, a valve opens and the pressure of the soil pushes the water out of the balloon and through a turbine to generate power. According to the scientists, this system has an efficiency of around 85%, which they say is in line with most pumped-hydro stations.

AquaNamic and the Aarhus University are currently planning to build a 10 m x 10 m demonstrator and have secured DKK 4.9 million ($674.147) from the Energy Technology Development and Demonstration Program. “We’re about to begin analyzing, designing and testing selected critical technologies related to the membrane and to the construction of the ‘movable hill’ that will form the terrain part of the battery,” said researcher Kenny Sørensen. “Naturally, we’ll have a strong focus on abrasion testing for the membrane, and we’ll need to develop a specially designed test rig to carry out lifetime tests for representative membrane solutions.”

One of the crucial aspects of the demonstrator will be assessing the extent of possible energy losses. “We want to retain as much energy in the system as possible, and this is a complex process with such a large system, which in principle will fill up every night, when the turbines are spinning and the world is sleeping, and then empty every day, when the energy is needed,” Sørensen further explained. “But every time the soil moves, the system is deformed, and these deformations contribute to the energy loss. They’re called plastic deformations. Our job is to optimize the system, using advanced calculation models.”

The new technology is also being developed in partnership with Danish wind energy giant Vestas and renewable energy developer European Energy.

Author: EMILIANO BELLINI

The hydrogen is consumed on-site. Image: J. A. G. I.

A Spanish scientist has developed a system that reportedly produces hydrogen on-site without expensive electrolysis.

From pv magazine

Spanish scientist José Antonio G. I.  has developed a system that is able to generate and store hydrogen on-site from tap water without electrolysis.

“Until now, the most common way to produce hydrogen is by electrolysis. However, this process implies a significant electrical consumption that makes it not interesting from an economic point of view,” he told pv magazine.

The prototype consists of a water tank that is initially filled with water and two more chemical elements that the researcher doesn’t want to reveal. Hydrogen production begins when a 20 W compressor discharges pressurized air in the lower part of the tank.

“It is the air that causes the reaction between the different chemical components and generates hydrogen,” the scientist explained. “Then, the generated hydrogen leaves through the upper area of ​​the tank to be introduced into an equally pressurized tank. The water in this second tank collects the possible impurities and hydrogen comes out through the upper part of the tank.”

After the hydrogen is purified, it flows via an upper conduit to another tank equipped with closed contacts, a safety valve and an outlet pipe assisted by a solenoid valve.

“Currently, we are developing a model with a 220-liter tank that can work with a pressure of 1 kg/cm2 and a flow rate of 30 liters per minute,” González Ibáñez went on to say. “This can generate heating, hot water and electricity for a household or a small business.”

The group is also designing a larger model that can work with a pressure of 750 Kg/cm2 and can reportedly supply a thermal power plant or a container ship.

“Hydrogen is produced at the place of consumption, so transportation disappears, it only needs a water tap,” the scientist emphasized. “The system is capable of generating the energy equivalent to a liter of gasoline –30 Mjoules or 8.333333 kW– for €0.0151515 ($0.0153749).”

Author: PILAR SÁNCHEZ MOLINA