variable renewable energy
From the very start of electricity, supply and demand had to be balanced.
Initially, it could be done by changing the output of the generators. The shifts in load were slow, mostly between day and night, and predictive.
This was the case through VWII, but after the war some fundamental changes, both load as well as of generation, made the balancing more demanding. On the load side the introduction of air conditioning significantly increased the amplitude between the bottom, referred to as the baseload, and the peak of demand. On the generation side nuclear power emerged. These plants had basically no flexibility and had to run all the time. Further, the increasingly large coal plants and the first generations of combined cycle gas turbines (CCGT) had limited flexibility. These generators, so called “baseload generators”, needed to be supplemented with more flexible generation to follow the load, from the baseload all the way to the peak power demand. Hydro power was the main flexible resource.
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Achieving 100% renewable energy was not so long ago seen as a dream. Now recognized to be viable, many cities around the world have set such targets.
Still it is not a trivial task to get to 100% renewable energy, while at the same time ensure reliable and affordable electric power. A key enabling factor is being connected to a large and robust electric grid. It gives access to remote renewable resources and it is the most cost efficient way to balance the variability of wind and solar. Let’s take a closer look at a couple of cases.
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In 2014 there were 3634 outages in the US electric system according to the Eaton Blackout Tracker. It affected in total over 14 million people. On average close to 4000 people were affected per outage, which on average lasted 43 minutes. 30 % of the outages were caused by weather and trees. 28 % were caused by faulty equipment and/or human error.
Almost all outages were at the distribution system level, Outages at the transmission level are very rare, but when they happen the consequences are bigger, affect more people and take longer time to restore. The Northeast Blackout in August 2003 hit 55 million people in United States and Canada. One month later the Italy Blackout had also about 55 million people in Italy, Switzerland, Austria, Slovenia and Croatia losing power. As recent as in March this year 90 % of Turkey with 70 million people lost their power. The largest blackout so far was in July 2012 affecting half of India and 620 million people. In fact the grid collapsed for a second time in two days.
2003 Northeast Blackout. Satellite pictures before and after the blackout. National Geophysical Data Center (NOAA/DMSP).
Lake Blåsjö, Norway.
Hydro storage is basically a renewable battery. Lake Blåsjö (“Blue Lake”) in Norway with a capacity of 7.8 terrawatthours (TWh) has become a symbol of Norway’s potential to become a “Blue Battery” for Northern Europe. To put the number in perspective 7.8 TWh would cover the electric consumption of over 750 000 residential homes. To accumulate the same amount of energy with lithium ion batteries it would take over 200 years of full production at Tesla’s planned Gigafactory.