Heat storage systems: Key technologies for sustainable heating supply

FAU and TH Nürnberg take a closer look at seasonal heat storage systems

Which technologies are particularly suitable for storing heat? Which storage capacities are advisable and economical for regional suppliers? Which role do space requirements, costs and temperature ranges play? These are some of the questions investigated in two consecutive studies conducted by Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and Technische Hochschule Nürnberg.

In future, heat will increasingly be produced using electricity, for example by using heat pumps or direct electrical heating. At the same time, the volatility of the electricity market is increasing, including during what is known as “dark doldrums”, or “Dunkelflaute”. These are phases in which the sun barely shines and where there is only very little wind. They last between two and twelve days and occur several times each winter. Energy suppliers such as N-ERGIE are then faced with the challenge of having to bridge such phases with little electricity from renewable energies and therefore high electricity prices. Heat storage systems can help to bridge these phases, secure the heat supply and also integrate renewable energies.

Storing heat for regional heat supply

The study, led by Prof. Dr. Jürgen Karl from the Chair of Energy Process Engineering at FAU, investigates various technologies for N-ERGIE for long-term heat storage and evaluates their cost effectiveness. Technology screening showed which technologies are suitable for offsetting fluctuations between winter and summer months or at least for bridging dark doldrums of one or two weeks effectively.

According to the study, there are enough tested technologies for seasonal heat storage in the gigawatt hour range. Alongside profitability, the main problem lies with the space required for large storage systems. In addition, the study also shows that heat storage with low-temperature storage systems can be realized economically over a period of time of up to one month. Low-temperature storage systems (between 20 and 60 degrees Celsius) would serve as heat sources for heat pumps in this case. To do so, surplus electricity from the summer months, from solar panels for example, could initially be stored by heating a warm water reservoir and used during the following winter to operate heat pumps.

“Heat storage systems are the key to making heating using renewable energies become independent from weather conditions and the seasons and thus also drive forward heat transition. Low-temperature heat storage systems are particularly promising because of the comparably low investment costs,” says Prof. Dr. Jürgen Karl.

The study titled “Wirtschaftlich vorteilhafte Speicherkapazität zum Transformationsplan für die Wärmeversorgung Nürnbergs”

(Economically viable storage capacity for the transformation plan for Nuremberg’s heat supply) carried out by Technische Hochschule Nürnberg investigates how N-ERGIE can fulfill its supply obligations in the most cost-effective way by potentially using storage systems.

The analyses were based on N-ERGIE’s aim to decarbonize district heating by using various components while simultaneously increasing the number of consumers it supplies. The study looked at cost estimates for different types of storage as well as prognoses for managing storage systems in a sample period and the market conditions of this period.

Further information:

Nora Elhaus
Phone: +49 911 5302 99050
nora.elhaus@fau.de