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The villagers of Wildpoldsried are celebrating a bumper harvest this year – not of wheat, or flax, a traditional crop in this part of southern Bavaria, but energy.
The village of 2,500 inhabitants has so many solar panels, wind turbines and biomass digesters that it generates three times the energy it consumes. The surplus is sold into Germany’s electricity grid, creating a big revenue stream for the locals.
The people of Wildpoldsried are “prosumers” – both producers and consumers of energy. It is a class that is growing fast in this part of the world, as Germany steams ahead with its Energiewende – its hugely ambitious switch away from polluting fossil fuels to renewable energy.
But the stunning success of places such as Wildpoldsried has created a dilemma for Germany’s electricity system. All that surplus energy can undermine the stability of the grid.
That is why Wildpoldsried is now the site of a unique experiment. It has become a testing ground for intelligent control systems designed to ensure that renewable energy does not put electricity networks at risk.
Interest in smart grids has grown as the world’s energy transition gathers pace. All over the world, countries are striving to achieve three often competing objectives – reduce carbon emissions, guarantee security of supply and make sure energy remains affordable for consumers. The significance of smart grids in meeting these goals keeps growing.
In a Siemens laboratory in the Bavarian town of Erlangen, a group of engineers is working out the ramifications of this new energy model. The lab contains a small experimental grid which allows researchers to test the network solutions of the future. It houses cabinets of batteries, an emergency generator, transformers, inverters, two refrigeration units and a water purification system.
The batteries store surplus power or feed it into the grid when needed. If demand rises fast, the diesel generator kicks in. In other words, this self-contained micro-grid works just like an ordinary high-voltage one. The aim is to make sure it remains stable in all types of load scenarios.
The Siemens lab is playing a crucial role in the Wildpoldsried experiment. It has teamed up with AUW, the local grid operator, and two universities to launch a project called Irene – Integration of Regenerative Energy and Electric Mobility – which is designed to test large-scale smart grids. The project involved installing some 200 measuring devices to give an overview of how the Wildpoldsried grid performs.
Michael Metzger, project manager for Irene at Siemens Corporate Technology, points to a map of Wildpoldsried and the surrounding area, projected on to the wall from one of the lab’s computers. It shows the location of the many solar panels, wind turbines and biogas plants, all connected to a series of purple lines representing the medium-voltage grid. Zooming in, he points to a profusion of small boxes: these are the measuring devices, each one of them connected by mobile phone to the lab.
“We’re measuring all the currents, voltages, harmonics – all the electrical variables – and doing a data analysis to look into problems in the grid,” he says.
One key piece of equipment used in Irene is a variable transformer, a big metallic-grey box with thick black wires coming out of the top. Photovoltaic power in rural areas “causes problems for power quality because the voltage in the distribution grid changes”, says Mr Metzger. “If it’s uncontrolled, lights would burn out and household appliances would break down.”
The problem, he adds, “will become more common as renewables’ share of generating capacity grows”. The variable transformer is able to offset such fluctuations in the voltage and so prevent disruption to supplies.
Siemens has also come up with a system called SoEasy – or “self-organising energy automation system” – which is designed to balance supply and demand and so keep the grid stable. The software knows the minimum price the owner of any given solar panel is willing to accept for the electricity he generates. It then submits the quote to a Balance Master, representing the grid operator, which then decides whether or not to accept the quote.
Meanwhile, residents of Wildpoldsried have been given electric vehicles, which have been integrated into the village’s smart grid and serve as a buffer for electrical energy.
“The idea is to use excess photovoltaic power to charge vehicles, which reduces the overload,” says Mr Metzger. Siemens is also looking at ways that such cars can return electricity to the grid in the event of power shortages.
Meanwhile, Wildpoldsried is going from strength to strength. The village currently has nine megawatts of generation capacity – three times more than its 3MW peak load, or demand. “This is no longer an energy consuming region – it’s a power plant,” says Mr Metzger. “It shows how much people want to be part of the Energiewende.”