EW-R-3: Electricity storage options

The picture shows the view along a large tube and a steep track down to a building and a water surface that is only visible in a small section.Click to enlarge
Pumped storage power plants like the one in Edersee can help control the electricity supply system
Source: Photograph: © parallel_dream / stock.adobe.com

2019 Monitoring Report on the German Strategy for Adaptation to Climate Change

Table of Contents

 

EW-R-3: Electricity storage options

At present, pumped-storage power plants are the most important technology for the storage of energy on a major scale. For generating electricity, these power plants have a turbine installed capacity of approximately 9 Gigawatt; for filling the storage facilities, pumps are installed with a total capacity of approximately 8 Gigawatt.

A block diagram shows with two columns each for the years 2011 to 2017 the net nominal capacity for installed and under construction turbine operation as well as the gross nominal capacity for installed pumping operation in gigawatts. There is a significant increasing trend for both installed turbine operation and turbine capacity under construction. No trend is discernible for installed pumping operation.
EW-R-3: Electricity storage options

A block diagram shows with two columns each for the years 2011 to 2017 the net nominal capacity for installed and under construction turbine operation as well as the gross nominal capacity for installed pumping operation in gigawatts. There is a significant increasing trend for both installed turbine operation and turbine capacity under construction. No trend is discernible for installed pumping operation.

Source: BNetzA (monitoring according to § 35 EnWG; power plant list)
 

Flexibilising the electricity system

While conventional electricity generation used to respond to demand, electricity systems nowadays have to integrate the weather-dependent infeed of electricity from renewable energy sources. The requisite flexibilisation of the overall system is achieved by the expansion and enhanced utilisation of electricity networks, by competition among flexible electricity producers and by means of storage within the electricity market. In order to achieve a large-scale equilibrium of generation and demand, the expansion of electricity networks is being promoted. In this way and by means of intensified links with the networks of European neighbours, it is possible to access the most economical locations of electricity generation. This approach also supports the adaptation of the electricity supply system to climate change, for instance in future cases when temporarily increased as well as regionally occurring imbalances between electricity supply and demand may arise. When there are bottlenecks in grid operation, network operators have to adopt the most efficient remedy available at that particular time. To that end, they might, for instance, access suitable generation and storage facilities (within the scope of Redispatch) as well as flexible loads (within the scope of regulations on interruptible loads).

The demand for electricity is met by flexible generators, load and storage facilities competing in the electricity market. When as many providers as possible – open to various technologies – compete in the electricity market with regard to meeting a specific demand, or – as the case may be – for utilising overcapacities, this will spread the risk of individual shortfalls thus ensuring that in each case the most favourable provider secures the deal.

Through the abstraction of electricity, i.e. the electricity consumption required for filling storage facilities and subsequently feeding this electricity back into the electricity system, storage technologies can cushion increasing fluctuations in electricity generation from renewable energies. For example, apart from battery storage facilities, power-to-gas (PtG) facilities can contribute to the flexibility of the electricity system. To a minor extent, the hydrogen produced in this process as well as methane, to a major extent, can be fed into the extant natural gas network where they can be stored. On demand, the gases fed into this network can be reconverted. Compared to the direct use of electricity, PtG is more expensive owing to the loss of efficiency, and it requires additional renewable energy capacities. However, this option is limited due to lack of space and lack of public acceptance.

In Germany, the storage technology with the greatest productivity and capacity is currently embodied in pumped-storage power plants. During the storage process, water is transported by pumps from a lower to an upper reservoir using electrical energy. At a later stage, the energy stored in the water is used during the process of discharging water from the upper into the lower reservoir, to drive a turbine and to generate electricity in a generator. In Germany, pumped-storage power plants have a turbine installed capacity of 6.2 Gigawatt (GW); in addition, power plants in Luxemburg (1.1 GW) and Austria (1.8 GW) are linked to the German electricity network. In theory, the turbine installed capacity is available for as long as the turbine operation in all power plants can be fed by the water from the upper reservoirs, i.e. for approximately three to four hours. After that point, the capacities of the storage facilities are successively exhausted which means that the turbine capacity becomes less and less available for electricity generation.

A further expansion of pumped-storage power plants in Germany would come up against a variety of objections thus limiting its likelihood. Such projects often meet with massive public resistance among residents and people looking for rest and recreation, not least in view of substantial encroachments on nature and landscape. Furthermore, potential sites for pumped-storage power plants are usually not located in places where a surplus of renewable energy is produced. However, there has also been a change in terms of economic circumstances. High infeeds of electricity from photovoltaic units at lunchtime mean that lunchtime peaks in electricity prices at the electricity exchange tend to bottom out, thus decreasing revenue streams from pumped-storage power plants.

Against this background, the technological advancement of storage technologies, alongside increased flexibilisation of electricity generation and demand, would make good economic sense in order to achieve essential cost savings. Currently, various technologies are being scrutinised and there is ongoing work on the advancement of hydrogen and other gas and battery storage facilities.

 

Objectives

Medium-term access to available German potentials for pumped-storage power plants within the scope of technical and commercial opportunities; intensification of research into new storage technologies and providing support for the achievement of market maturity (Energiekonzept 2010, p. 21)