The Intermittency Challenge
Today, I had a meeting with an employee at Fraunhofer ISE. The Fraunhofer organization is made up of 66 applied research institutes conducting research in a wide variety of topics. Fraunhofer ISE (Institute for Solar Energy Systems) focuses on solar power and is based in Freiburg. The person I met with does research on the power markets in Germany and the EU. I want his job. His research is awesome and he has access to so many brilliant people and resources. I was drooling over his graphs.
For this post and those that deal with the challenge of intermittent renewable energy supply, when I talk about renewable energy I am primarily referring to solar and wind power, since these make up the largest renewable technologies in Germany and suffer the greatest intermittency problems. The other major renewable technologies in Germany such as hydropower and biomass aren't intermittent and so aren't addressed when I am using the term "renewable energy".
One of the main areas of my research in Germany has come to center on the grid transition necessary to incorporate a high percentage of renewable energy. As I will describe in subsequent posts, the main challenge facing Germany is not installing more solar, but redesigning their grid to deal with the fluctuating supply of renewable energy especially as they approach their target of 35% renewable electricity by 2020, and 80% by 2050.
I came into this fellowship thinking the biggest challenge so solar was going to be the cost, so the importance of dealing with intermittency came as a bit of a surprise to me. To me, the conventional wisdom stated, "solar is still too expensive." I thought the cost just needed to come down, and when solar was cheaper than fossil fuels we're done. The masses will flock to solar power because they can "do the right thing" and can save money (this being the critical factor) and voilá! Energy transition over.
Not ever close. There is this pesky little thing called intermittency that gets in the way. As we all know, the sun doesn't shine at night. Moreover, cloud cover, the time of day, and the orientation of the solar panels all influence the amount of energy supplied by a solar system during the daytime. Since people like to have the lights turn on when they flip the switch, something on the grid must make up the shortfall when the clouds roll in, when the sun goes down, and when the wind stops blowing.
There a several ways to try to make up for changes in energy production: flexible conventional generation such as natural gas power plants, energy storage, demand-side management, and diversifying the renewable energy supply to smooth out local effects in the weather.
Flexible conventional generation involves firing up power plants when the supply of renewable energy decreases. The power plants best suited for this purpose run on natural gas since they can be up and running in 15-30 minutes depending on how long the plant has been off. Another blog post describing the challenges to changing the mix of conventional generation in German to gas power is coming soon!
Energy storage involves storing excess energy when the sun is shining bright and releasing that stored energy when the clouds roll in. There are many technologies to store electrical energy such as pumped storage (pumping water uphill), compressed air, heat storage, batteries, super capacitors, hydrogen storage, and flywheels. Stay tuned for a detailed post on energy storage options!
Demand-side management consists of adjusting the demand for electricity to meet the fluctuating supply. This turns the current electricity paradigm on its head, since historically the supply has always been coordinated to meet the demand. Demand-side management basically involves incentivizing consumers to turn off equipment when the energy supply decreases and turn the equipment back on when there is enough supply. The incentive is done through time-of-use pricing. When the supply goes down the price per kWh goes up, making it more affordable for consumers to reduce demand. When the supply increases again, the electricity price will go down providing an incentive for consumers to turn the equipment back on.
The last solution, diversifying the supply, can take on many different forms. One example of diversification is to expand the grid in individual provinces in German to allow excess supply in one region to meet a shortfall in another. The most important grid expansion in Germany involves a high voltage power line corridor running from north to south Germany. This would allow the high concentration of wind power from the north and solar power in the south to complement each other. Another example of diversification involves strategically placing renewable energy plants in Germany where they are most needed. Achieving this strategic placement would likely involve incentivizing the construction of renewable power plants in certain areas through localized subsidies. The last major option of diversification is to increase German's connectivity to the rest of the EU, which allows Germany to import and export electricity when needed.
The future of the German electricity grid will include a combination of all four options. Based on research the person I met with had done with Fraunhofer ISE, flexible generation is much more effective than energy storage for making the renewable energy supply more reliable, which came as a surprise to me. Flexible generation and grid expansion seem like the most important methods to dealing with the challenge of intermittency, but nothing is ever certain in this industry!
For this post and those that deal with the challenge of intermittent renewable energy supply, when I talk about renewable energy I am primarily referring to solar and wind power, since these make up the largest renewable technologies in Germany and suffer the greatest intermittency problems. The other major renewable technologies in Germany such as hydropower and biomass aren't intermittent and so aren't addressed when I am using the term "renewable energy".
One of the main areas of my research in Germany has come to center on the grid transition necessary to incorporate a high percentage of renewable energy. As I will describe in subsequent posts, the main challenge facing Germany is not installing more solar, but redesigning their grid to deal with the fluctuating supply of renewable energy especially as they approach their target of 35% renewable electricity by 2020, and 80% by 2050.
I came into this fellowship thinking the biggest challenge so solar was going to be the cost, so the importance of dealing with intermittency came as a bit of a surprise to me. To me, the conventional wisdom stated, "solar is still too expensive." I thought the cost just needed to come down, and when solar was cheaper than fossil fuels we're done. The masses will flock to solar power because they can "do the right thing" and can save money (this being the critical factor) and voilá! Energy transition over.
Not ever close. There is this pesky little thing called intermittency that gets in the way. As we all know, the sun doesn't shine at night. Moreover, cloud cover, the time of day, and the orientation of the solar panels all influence the amount of energy supplied by a solar system during the daytime. Since people like to have the lights turn on when they flip the switch, something on the grid must make up the shortfall when the clouds roll in, when the sun goes down, and when the wind stops blowing.
There a several ways to try to make up for changes in energy production: flexible conventional generation such as natural gas power plants, energy storage, demand-side management, and diversifying the renewable energy supply to smooth out local effects in the weather.
Flexible conventional generation involves firing up power plants when the supply of renewable energy decreases. The power plants best suited for this purpose run on natural gas since they can be up and running in 15-30 minutes depending on how long the plant has been off. Another blog post describing the challenges to changing the mix of conventional generation in German to gas power is coming soon!
Energy storage involves storing excess energy when the sun is shining bright and releasing that stored energy when the clouds roll in. There are many technologies to store electrical energy such as pumped storage (pumping water uphill), compressed air, heat storage, batteries, super capacitors, hydrogen storage, and flywheels. Stay tuned for a detailed post on energy storage options!
Demand-side management consists of adjusting the demand for electricity to meet the fluctuating supply. This turns the current electricity paradigm on its head, since historically the supply has always been coordinated to meet the demand. Demand-side management basically involves incentivizing consumers to turn off equipment when the energy supply decreases and turn the equipment back on when there is enough supply. The incentive is done through time-of-use pricing. When the supply goes down the price per kWh goes up, making it more affordable for consumers to reduce demand. When the supply increases again, the electricity price will go down providing an incentive for consumers to turn the equipment back on.
The last solution, diversifying the supply, can take on many different forms. One example of diversification is to expand the grid in individual provinces in German to allow excess supply in one region to meet a shortfall in another. The most important grid expansion in Germany involves a high voltage power line corridor running from north to south Germany. This would allow the high concentration of wind power from the north and solar power in the south to complement each other. Another example of diversification involves strategically placing renewable energy plants in Germany where they are most needed. Achieving this strategic placement would likely involve incentivizing the construction of renewable power plants in certain areas through localized subsidies. The last major option of diversification is to increase German's connectivity to the rest of the EU, which allows Germany to import and export electricity when needed.
The future of the German electricity grid will include a combination of all four options. Based on research the person I met with had done with Fraunhofer ISE, flexible generation is much more effective than energy storage for making the renewable energy supply more reliable, which came as a surprise to me. Flexible generation and grid expansion seem like the most important methods to dealing with the challenge of intermittency, but nothing is ever certain in this industry!
