The sun doesn’t always shine and the wind doesn’t always blow, what do we do if there is no renewable energy when we need to turn on the lights? Normally, pulling lithium batteries either pumped hydroelectric plants. But cities that build vertically like Benidorm have another untapped option.
In short. A comprehensive University of Waterloo study has shown that the height of buildings can be used to create a system of gravity energy storage. An idea that transforms cities built in height into a huge device to store and release energy at will.
Mechanical batteries. The concept is, in essence, very simple. It is made up of a heavy mass (concrete or steel blocks), a system of pulleys and cables similar to that of an elevator, and a motor that also works as a generator.
The operation is as follows. When there is a surplus of energy, for example at midday, when the building’s solar panels are at full capacity, the motor uses that electricity to lift heavy dough along a vertical gaplike that of an elevator. Electrical energy is converted into potential energy.
When electricity is needed and renewables are not producing, at night or on a day without wind, the mass is dropped in a controlled manner. The force of gravity does the rest: the descending weight moves the generator, which converts the potential energy back into electricity ready to use.
Tested successfully. The researchers propose this system as the heart of a hybrid energy ecosystem integrated into the building itself, which includes photovoltaic panels on facades, small wind turbines on the roof and backup lithium-ion batteries.
As pointed out PV Magazinecompanies such as the Scottish Gravitricity have already demonstrated the viability of this technology with functional prototypes and have full-scale commercial projects of 4 and 8 MW underway. Energy is generated with the sun and the wind. Gravity acts as the main battery for daily storage, managing large charge and discharge cycles.
Is it viable? To test whether their idea was more than just an interesting theory, the University of Waterloo team ran a massive simulation. They analyzed 625 different building designs, varying parameters such as height, the shape of the floor plan (more square or more elongated) and the energy efficiency of the building.
The results are very promising. The system (facade solar panels + small wind power + gravity storage + a battery support) achieved a levelized cost of electricity of between 0.051 and 0.111 dollars per kWh.
This figure is very competitive, and even improves the costs of other renewable energy systems integrated into buildings located in areas with moderate solar or wind resources. And taller buildings with larger floor plans benefit the most, so Benidorm It is our best asset.
Image | Diego Delso (CC BY-SA 3.0)
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