Special Report: Solar power aids German nuclear shutdown

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This article is part of our special report Solar Power.

Germany has imported more lignite coal and nuclear energy from its neighbours since the Fukushima disaster pushed it to begin closing its ageing nuclear reactors. But it is still exporting one source of electricity to France: solar power.

"When there is a lot of solar production at midday, then even France imports from us," a trader told Reuters.

Germany is one of the world's leading solar photovoltaic (PV) energy producers, with a solar capacity of almost 17GW, 40,000 employees and a 2% electricity market share. In 2010, the country set a world record for installations of solar PV in one year.

But supplies from variables such as wind and solar are intermittent – depending on the elements – and their electricity generation on one day measured in February varied from a high of 32% of supply at midnight, to a low of 18% at sunrise.

Solar PV generated more than 8,000 MW of that amount – 13% of the overall supply – for two hours at midday. But conventional sources such as oil and gas generated some 50,000 MW during the same period.

Despite this, advances in weather forecasting are making variables increasingly attractive,  according to a report in the Guardian newspaper yesterday (25 May).

Nuclear 'will never provide electricity for peak hours'

Paolo Frankl, head of the International Energy Agency's (IEA) Renewable Energy Unit, told EURACTIV that concentrating only on "base load" providers such as coal and nuclear energy would be a mistake.  

"You need to balance all the load demand and supply," he said, "and nuclear will never provide electricity for peak hours".

"This is why the huge quantities of solar PV in Germany are helping to meet the peak demand in France," he added.  

Balancing demand and supply dynamics in power systems with large shares of 'variables', has traditionally raised questions about grid integration and stability.

But a new report released on Tuesday (24 May) by the IEA, 'Harnessing Variable Renewables: a Guide to the Balancing Challenge', proposes a four-step method for measuring existing resources.  

After assessing the flexibility of different energy sources, the constraints of their power systems are then analysed, maximum flexibility requirements are calculated, and the amount of extra variability that can be balanced in demand and supply chains is identified.

The IEA study found that Denmark had a 63% potential to balance large shares of variable renewable energies, while the Nordic countries' potential was 48%, the UK and Ireland's was 31% and Spain and Portugal's was just 27%.

According to Frankl, "national political willingness" to harness solar PV power had partially eclipsed better criteria for locating plants.

Some well-known environmentalists, including George Monbiot, oppose tariffs for solar PV in cloudy countries such as Germany and the UK on account of their low financial returns.

"In the future, we hope that peak demand [in France] will be covered more by PV installations in the country's south or from Italy than from the north," Frankl said.

Some analysts predict that by 2050, solar PV could supply up to 25% of Germany's electricity. But for now, across Europe, 'base load' power plants fired by coal and nuclear are currently used most of the time for cost reasons. By contrast, 'peak power' generators are dispatched only when energy demand is at its highest.

This is because base load plants have high capital and maintenance costs but low fuel costs. The reverse applies to 'peak power' systems such as gas turbines – and sometimes to solar PV arrays, depending on the level of feed-in tariff (or state subsidy).  

In Germany, historically high tariffs – 43 cents per KiloWatt hour in 2009 – led one study to decry "solar electricity's grave lack of competitiveness". But solar enthusiasts argue that because prices in Germany's deregulated market rise at peak times, the financial returns on technologies such as solar PV will continue to rise accordingly.

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