We Have the Technology: Energy Storage for 100% Renewables


Source:  PNNL

Three thousand metres underfoot in Wolfersberg, Southern Germany, the rock isn't solid. In fact, there's enough space in the porous rock that 365 million cubic metres of natural gas can be stored in the air spaces. Natural gas is pumped in when demand is low and it's pumped out when demand is high. It's part of a massive network underfoot in Germany that supplies energy stability and security.

Germany plans to have a 100% renewable energy system by 2050, which means this labyrinthine network won't always store natural gas. In the future, it will likely store hydrogen instead. Using only the natural gas storage capacity that already exists, Germany could store enough hydrogen to meet the country's energy needs for three weeks.

This is just one example of the storage solutions necessary to power a modern renewable energy system. Dr. Dirk Uwe Sander of the Institute for Power Electronics and Electrical Devices took the audience through a tour of the energy storage sector on Thursday March 14th at a Sustainable Energy Initiative event at MaRS.

Dr. Uwe Sander made one thing crystal clear: we have all of the technology we need, today.

"The problem about storage technology is cost, not space and technology." Dr. Dirk Uwe Sander, Institute for Power Electronics and Electrical Devices

Storage will play a pivotal role in the energy systems of tomorrow, but it won't look much like the current energy system. The modern energy system will have more interlinkages between electricity, heating, cooling, transportation and other sectors. As the amount of energy we get from renewable sources rises, the silos between sectors will have to come tumbling down.

Millions of electric car batteries will be plugged into the grid for hours at a time. It's flexible energy storage that will play a huge role in a system powered by renewables.

Dr. Uwe Sandner stressed is that there is no silver bullet for all storage. Pumped hydro is a solution for storage over a period of days, for example, but it is useless to solve problems at low level voltages, such as smoothing out power production from small solar photovoltaic systems. A range of solutions have to be applied at appropriate scales.

One size doesn't fit all in the storage world. 

An energy system has storage needs in the short, medium and long term. At the scale of minute-to-minute storage, technologies like fly-wheels can collect energy and store it to smooth out energy production as it happens. In the range of days, storage technologies such as batteries can be used to bridge common natural variations in sunlight or wind power. Meteorological data shows that about every ten years there is no wind anywhere in Europe for a period of three weeks, for example. We'll need long-term storage solutions to maintain the ability to power society during these rare, but predictable, droughts.

Big changes are needed to get to a system that is flexible enough for 100% renewable energy sources, but we aren't missing the technological solutions. The technology has already arrived.


work well for high number cycles that are just a few seconds each. They are perfect for applications like hybrid buses, but they are expensive and therefore are not appropriate in circumstances where they would only be used in one cycle per day.

Pumped hydro

is the cheapest option, but only works if the right geography is available. Existing hydro power plants can be retrofitted, which offers a huge potential in existing infrastructure.

Compressed air energy systems (CAES)

are also an option. The air that is compressed needs to be stored somewhere, but there is potential storage in salt caverns and underwater.

Chemical storage

is the classical battery or external storage, such as fuel cells. There have been speedy advancements in lithium ion batteries and the efficiency of the energy conversion has reached 95%. Lead acid batteries are the older technology, but they are still competitive because the raw materials are so cheap and recycling is cheaper than other technologies.


can be converted to gas using electricity when there is a surplus and stored underground in caverns or depleted oil and gas fields. The efficiency of the energy conversion is only about 40%, but the opportunity to use existing infrastructure is high.

To get serious about storage and to roll out these technologies on a massive scale, a number of policy strategies are necessary. From R & D support, to demonstration projects, to government market introduction programs - revolutionizing the energy system requires support. The fundamental change, however, is to adapt the design of the market to the new system. An energy system based on renewables has different peaks and valleys in energy production and the market rules have to recognize that reality.

It takes years to train a workforce of engineers, technicians, scientists, and other specialists needed to maintain a vast system of energy storage. Germany is starting now so that they are prepared for the country's planned transition to renewables over the next three and a half decades. Dr. Uwe Sandner showed the audience what it will take from the energy storage sector to get to 100% renewables, but he left the audience with an interesting point.

We need to take energy storage further than ever before to get to 100% renewables, but it isn't necessary when renewable power makes up a smaller percentage. Germany is already 25% powered by renewables without it.