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Special - Spatial Planning and Energy for Communities in All Landscapes Town and Country Planning Association European Union

Knowledge Pool

Module 4: Implementation of Sustainable Planning

4.4 Storage


The storage of energy is one of the most important challenges for the transformation of the actual fossil based energy systems towards a sustainable climate friendly energy supply system. Storage is important for both, (a) power- and (b) heat/cold supply for settlements and industry. The storage mediums are very different: water, compressed air, gas, liquid, batteries, soil and so on. For example stored heat can be used in winter and cold obtained from winter air can be provided for summer air conditioning. Furthermore such systems can (partly) be a component of fuel supply for mobility purposes. In brief, storage systems are very important because:

  1. use/storage of surplus energy from renewable sources (e.g. wind/sun power)
  2. help to discharge of grids - in cases of overload
  3. stabilisation of grids in cases of unsteady supply by renewables – control unit
  4. provider of energy in a flexible way – heat, cold, power
  5. provider of energy in  different times because systems can store energy for hours, days, or months – heat in winter.

For the background of the expansion of renewable energies through e.g. wind farms and PV it will be more common that the produced energy is higher than the demand – that means a surplus on energy. In addition the grid load is subject of fluctuations by renewables which have to be balanced. Energy storage is accomplished by devices or physical media that store energy to perform useful operation at a later time. Some technologies provide only short-term energy storage, and others can be very long-term. Energy storage systems in commercial use today can be broadly categorized as mechanical, electrical, chemical, biological and thermal.
For the implementation of storage systems for energy also the modification of the grid system towards a smart grid is sensible.

Relevant parameters to be considered

Pumped-storage Hydroelectric systems (PSH) need big constructions which have often considerable effects/impacts on nature and landscape.  In general a regional planning procedure is needed to implement a PSH.

Compressed air energy storage (CAES) systems have more or less minor impacts on landscape and nature because it is underground. But it will have an impact on the use competition in the underground. Salt caverns are also usable for storage of gas or CO2. The caverns have to flush out which produces high amount of brine. Geological circumstances play an important role for such technique, because big underground storage capacities like salt caverns or abandoned mines are needed.

Power to gas can be an important part of the future energy supply system which should be recognized in planning. The efficiency is not very high concerning the losses during the transformation processes. But it´s better to convert surplus renewable energy then lose it. Furthermore the gas can be storage in existing infrastructure systems (e.g. gas pipes). 

Underground thermal energy storage (TES) can have an impact on the groundwater system, drinking water production, and the subsurface environment. See: http://www.ecologyandsociety.org/vol16/iss1/art22/

Planning relevant issues

Planning can help to support the establishment of such necessary systems for the energy transformation. Areas where renewable energy is produced are perfect for such storage systems but geological conditions (topography, etc.) play an important role. Planners can combine the planning for locations for renewables with localisation of possible storage possibilities.

Aspects of formal or informal planning on local and regional level:

1. Local level
The formal binding land use plan on local level can be an instrument to foster energy storage systems (e.g. seasonal thermal storage systems) for example on quarter level (see example: QuarterStorage Weinsberg). Also informal instruments like municipal climate protection concepts can be used.

2. Regional level
Positive analysis in regional planning can be an element for the localisation of sites. Use of formal regional development plan, or use of an informal instrument like the regional development concept.

For some systems like the underground thermal storage sytsems a cross-sectoral subsurface planning is required to minimize negative conflicts between underground thermal energy storage (UTES) and other subsurface interests.

Storage tends to be an application specific resource and therefore the costs and benefits can vary greatly between technologies.

  • costs of a technology are greatly influences by the particular application in which that technology is deployed
  • an energy storage system varies on two dimensions: power (how much electricity can be discharged at one time) and energy (how many hours can be discharged continuously)
  • energy storage system costs are impacted by system efficiency
  • the frequency of how often and deeply the system is charged and discharged also impacts costs. An energy storage technology's cost cannot be meaningfully estimated independently of the way in which it is used
  • lifecycle cost of an energy storage system is made up of two basic components: capital costs and operating and maintenance costs (O&M). Energy storage O&M costs include the cost of buying the energy used to charge the system, fixed costs that do not depend on how much or often the system is used, and variable costs, the bulk of which are usually replacement costs.

PSH and CAES: While general cost estimates are of questionable value as to the accuracy of the cost of the system, such an analysis does indicate the relative cost of the technology compared to the other options of energy storage. Considering pumped hydro, this technology's efficiency and costs depend on a variety of factors. Schoenung and Hassenzahn (2002) identify the head of water, the civil costs of excavation, tunneling and dam building as several of these factors. An average value for the power-related part of installations under construction today is $1000/kW, while the cost of the storage component is relatively inexpensive, at about $10/kWh. The typical round-trip efficiency of large plants is about 0.75. This technology has been the primary type of energy storage for utilities to date. Today, however, only a few locations exist where adequate water and sites for upper and lower reservoirs are available.

In comparison to battery systems CAES is shown to be the least expensive technology, followed by pumped hydro. This is primarily because of the low cost of storage. Pumped hydro with variable speed drive is slightly more expensive than conventional pumped hydro, even though it is more efficient. This is offset by large benefits due to greater operational flexibility. On a component basis, it can be seen that CAES and pumped hydro have relatively low costs. This is partially due to the lack of replacement costs for the installation. For instance, batteries have components which have a maximum number of charges after which capacity losses occur. In the study by Schoenung and Hassenzahn (2002) it is assumed that pumped hydro and CAES have no replacement costs throughout the lifetime of the installation.


Schoenung, S., M., & Hassenzahn, W., V., 2002. Long- vs Short-Term Energy Storage Technology Analysis: A life cycle cost study.

Thermal energy storage includes a number of different technologies, each one with its own specifi c performance, application and cost. TES systems based on sensible heat storage off er a storage capacity ranging from 10-50 kWh/t and storage effi ciencies between 50-90%, depending on the specifi c heat of the storage medium and thermal insulation technologies. Phase change materials (PCMs) can off er higher storage capacity and storage effi ciencies from 75-90%. In most cases, storage is based on a solid/liquid phase change with energy densities on the order of 100 kWh/ m3 (e.g. ice). Thermo-chemical storage (TCS) systems can reach storage capacities of up to 250 kWh/t with operation temperatures of more than 300°C and effi ciencies from 75% to nearly 100%. The cost of a complete system for sensible heat storage ranges between €0.1-10/kWh, depending on the size, application and thermal insulation technology. The costs for PCM and TCS systems are in general higher. In these systems, major costs are associated with the heat (and mass) transfer technology, which has to be installed to achieve a suffi cient charging/discharging power. Costs of latent heat storage systems based on PCMs range between €10-50/kWh while TCS costs are estimated to range from €8-100/kWh. The economic viability of a TES depends heavily on application and operation needs, including the number and frequency of the storage cycles.

Source: IRENA. Thermal Energy Storage 2013

Description of the most innovative aspects involved

The storage of energy is a necessary technique for the transformation of our energy systems. Most innovative are:

  • storage of surplus power energy from wind, sun and other renewable sources
  • short starting time for using the energy (minutes)
  • balancing the net
  • solution for power and heat (see: power to gas)
  • use for mobility purposes (see: power to gas)
  • existing infrastructure can be used (see power to gas)
  • long time storage of heat for use in winter
Innovations and social aspects

The storage of energy (typically from renewable energy sources, waste heat or surplus energy production) can replace power, heat and cold production from fossil fuels, reduce CO2 emissions and lower the need for costly peak power and heat production capacity.

For example the storage of thermal energy only in Europe has the estimated potential to save
around 1.4 million GWh per year — and 400 million tonnes of CO2 emissions avoided—in the building and industrial sectors by more extensive use of heat and cold storage. However, TES technologies face some barriers to market entry. In most cases, cost is a major issue. Storage systems based on TCS and PCM also need improvements in the stability of storage performance, which is associated with material properties.

Source: IRENA. Thermal Energy Storage 2013.

Links, literature to PSH – Hydropower storage

Schoenung, S., M., & Hassenzahn, W., V., 2002. Long- vs Short-Term Energy Storage Technology Analysis: A life cycle cost study.

Links, literature to Thermal Energy Storage (TES)


Links, literature to CAES – Compressed air


Links, literature to Power to Gas


Further documents, presentations:

Specht, Power-to-Gas (P2G®): Technology and System Operation Results


M. Bonte, et. al., Underground Thermal Energy Storage: Environmental Risks and Policy Developments in the Netherlands and European Union


Energy Resources and Renewable Energy Technologies by UP-RES

(also available in German, Italian, Hungarian, Swedish)