Zero energy brighter future

A German architectural firm is to build the world's first tower with a zero carbon footprint in Bahrain.
Zero energy brighter future
By Benjamin Millington
Sat 03 Jan 2009 04:00 AM

Taking sustainability to a new level, German architectural firm Gerber Architekten is planning to build the world's first tower with a zero carbon footprint in Bahrain. How will they do it? Our How-To handyman Benjamin Millington finds out.

The word "sustainability" has become a popular marketing tool in the construction industry of late with many developers adding various energy-saving elements to their projects to earn the green tag.

But as anyone with a background in green design will tell you, using low-wattage light bulbs or even slapping photovoltaic solar panels on the roof are only small steps towards being truly sustainable.

We’re saving a third of the entire building’s consumption. - Thomas Lucking, Gerber Architekten

Hoping to set a new bench mark in this regard, Thomas Lucking, of architectural firm Gerber Architekten, said they have designed a tower which will be completely energy self-sufficient.

"We basically achieve this in two steps," he said.

"We first of all designed it to be a highly energy efficient building which requires 60% less energy compared to a regular building of the same size.

"Secondly, we cover the remaining 40% of energy with renewable sources such as sun and wind."

Gerber Architekten plans to build several of these Energy Towers around the world, the first of which will be in Bahrain and is being backed by developer Al Moayad Holding.

A plot of land has already been identified on which they will start a feasibility study next month. If all goes smoothly the tower could start construction in 2013 for completion in 2015.

Inspired by the traditional wind towers of the Middle East, the Energy Tower saves much of its power requirement through a natural ventilation system driven by the wind.

Lucking explains that when wind hits the tower it is naturally pushed to either side and accelerates which creates negative pressure or suction.

Where this occurs, sensor controlled louvers on the outside of the tower will automatically open and the suction will draw out exhaust air from inside the building's double-layered façade.

Thus, a ventilation cycle is created. Fresh cool air is pumped into the building, drawn towards exhaust vents on each floor, enters the double-layered façade and is then sucked out by the external louvers.

"By this method we can save a lot of power by not having continuously running mechanical fans for ventilation," said Lucking.

"We estimate that a regular building of that size would need a total of 30,000MW hours a year and about 9,000MW alone is for the ventilation.

"So we're saving a third of the entire building's consumption."

Cooling

Lucking said another third of a regular tower's energy consumption is used on cooling, namely running air conditioning systems.

Steering away from this energy intensive method, the supply air for the Energy Tower will be naturally pre-cooled through air channels buried in the sea before being further treated by air handling units.

Using chilled water, the units will cool the air down to 18 degrees before it is distributed to every floor through a central atrium and five perimeter atria that run the length of the tower.

Coupled with this, Lucking said they will also chill the ceiling slab by running chilled water through pipes in the ceiling. The cool ceiling will then absorb any radiation or heat generated from lighting, computers and people in the room.

The beauty of the system is that it's designed to be carbon neutral, said Lucking.The chilled water used in the process will come from solar cooling technologies that heat water up and convert it into cold water through an absorption process.

No fans are necessary to distribute the air due to the natural ventilation process already mentioned.

And the electricity used to run the handling units will be supplied from the tower's other renewable wind and solar sources.

Lighting

To minimise the amount of energy wasted on artificial lighting during the day, the Energy Tower tries to maximise its usage of daylight.

To harvest natural light, highly reflective mirrors called heliostats, will cover the entire roof of the tower and reflect sunlight to the tip of a light cone in the tower's centre.

The light cone runs the length of the building and reflects the light into each floor through a system of holographic optical elements.

Lucking said the tower's double-layered façade will also have clear glazing instead of light reflective tinned glazing commonly seen on most towers.

Solar shield and renewables

While the clear glazing will let in more light, the flipside is that it also lets in more heat. To combat this problem, the inner layer of the façade will be vacuum glazing, a new glazing which helps prevent heat transfer.

Additionally, the designers have developed a solar shield which will rotate around the building protecting it from the heat of the sun.

The semi-transparent shield runs the length of the building and rotates on rails within the double-layered façade tracking the sun around the building.

Not letting a good sun harvesting opportunity go to waste, the solar shield will be covered in 4,000m2 of photovoltaics solar technologies which will account for 20% of the tower's renewable energy.

Another 11,000m2 of photo-voltaics will be placed on the shopping mall rooftop at the base of the tower and 17,000m2 of solar collectors for the water cooling process will be on a floating solar island next to the tower.

The final renewable energy source will be the 60m wind turbine on top of the tower, the largest of its kind in the world.

"It called a Darrieus-rotor and is a proven technology, but no one has done it in that size before," said Lucking. "It has the advantage that you don't need to direct it towards the wind. Regardless of where the wind is coming from, it will turn."

Structure

According to Lucking the main structural element of the tower is the external columns which provide strength and support due to their lattice-like arrangement.

Lucking said strength is such that they've avoiding using any internal columns and have managed to save a tremendous amount of space.

The only internal load bearing structure is the central atrium, which in itself is utilised for the vertical transportation of people and fresh air.

Comfort

Throughout the design of the building Lucking said they tried to create the most comfortable interspatial experience for people in the tower.

Without confining structural walls, the interior will consist of open areas filled with an abundance of natural light; hanging gardens will run the entire length of the building within the five ventilation atria; and the ventilation and cooling system will be more comfortable than the cold draughts associated with air conditioners.

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