Lift storage power plant

A lifting storage power plant , also known as a storage power plant , is a type of storage power plant in which electrical energy is temporarily stored in the form of potential energy (positional energy) of the lifting body. The term is usually only used when a solid body is used as storage mass. Water storage power plants , especially pumped storage power plants that use liquid water as storage mass, do not fall under the term, although they also store potential energy.

state of development

Although the physical fundamentals are very simple and the necessary techniques from other applications on a smaller scale are sufficiently tried and tested, the concept of a large-scale lift storage power plant, which can compete with other storage power plant types in terms of performance and storage capacity, is still in the concept phase. There are various ideas, inventions and patent applications as well as research projects. The University of Innsbruck (UIBK) has built a prototype and another is under construction.

A first prototype with a diameter of 20 meters and a height of 30 meters is due to go into operation in Saudi Arabia in 2019 . ^[obsolete] As of January 2018, negotiations were held with the Saudi Arabian government about a funding grant.

An Energy Vault test facility up to 120 meters high is currently being built near Bellinzona (as of early 2020).

Potential and profitability

The volume of a body and thus its mass change to the third power of its dimensions (example: ten times the edge length, the mass of a cube increases a thousand times), while the costs of lifting technology are usually linearly scalable. Lifting storage units with small dimensions are therefore disproportionately expensive and can hardly compete with other storage concepts such as accumulators . For example, for a block with a volume of 1 cubic meter, which consists of solid steel (density 7.85 t / m³) and which is lifted 500 meters into the air, energy storage of around 10.7 kilowatt hours results , which corresponds to the energy content of approx 10 motor vehicle starter batteries . In the case of very large masses, on the other hand, according to the developers, lift tanks would be extremely economical.

The gravity storage system developed by the Swiss company Energy Vault is said to have an efficiency of 90 percent. The Softbank has already invested 110 million US dollars in the company.

Physical basics

The positional energy that a stroke storage system can absorb corresponds to the product of mass, acceleration due to gravity and the difference in altitude. Expressed in formulas: The stored positional energy when lifting / lowering a storage mass against the acceleration due to gravity by a height difference is calculated in simplified form as: ${\displaystyle E_{\mathrm {pot} }}$ ${\displaystyle m}$ ${\displaystyle g}$ ${\displaystyle h}$

${\displaystyle E_{\mathrm {pot} }=m\cdot g\cdot h}$

If you know the volume and the mean density of the storage mass, you can replace the mass: ${\displaystyle V}$ ${\displaystyle \rho }$

${\displaystyle E_{\mathrm {pot} }=V\cdot \rho \cdot g\cdot h}$

Technical concepts

Lifting technology

Any technique that moves objects in a vertical direction can be considered. The vertical movement can be perpendicular, such as in an elevator, or at an angle, e.g. B. be done in a rack railway .

Basically almost all types of construction that are also used in conveyor technology or in transport vehicles are conceivable as conveyor systems, such as wire ropes , chains , racks , but also lever mechanisms and threaded spindles . At an angle, the masses z. B. be moved up and down on rails. The movable masses, regardless of whether they are individual weights or bulk goods, are relatively small in all of these cases.

Hydraulic lifting devices are suitable for large masses , especially with water as the hydraulic medium. Lifting large masses over considerable differences in height has been tried and tested , for example, from the construction of ship lifts . The conversion of the potential energy back into electrical energy can then be done using conventional turbine technology. A hybrid form of lift storage and pump storage power plant is created. The advantage over classic pumped storage power plants that only work with water is that, due to the higher density of metals or rock compared to water, a multiple of the energy can be stored with the same volume. The efficiency would be as good as that of pumped storage power plants (approx. 75–85%).

The concept Power Tower (engl., Dt. Mutatis mutandis energy tower ) of the University of Innsbruck denotes a hydraulic energy store, in which, in a column, shaft or tower-like structure heavy cylinders are pumped upwards. The water flow created by their pressure drives a turbine. "Well over 80%" is specified as the degree of efficiency ; the goal is an energy storage capacity of one megawatt hour. Comparable with this concept, albeit in a much larger dimension, is Eduard Heindl's design of the energy storage system with a planned cylinder of approx. 65 m radius and 130 m height, which would be sawn out of a rock that was as homogeneous as possible. This cylinder size results in a storage capacity of around 500 megawatt hours.

The Buoyant Energy concept (also from the University of Innsbruck ) consists of hydraulic, floating offshore systems for converting and storing electrical energy. The core of the idea is “a kind of floating pumped storage power plant”. Water is moved back and forth between a reservoir integrated in a large floating body (e.g. made of steel or concrete) and the surrounding lake or ocean, depending on the needs of the energy industry (excess electricity / demand).

Energy recovery

The crucial difference between a lift storage power plant and normal conveyor systems is the fact that the stored energy is not "destroyed" in a conventional brake (i.e. converted into heat) during the downward movement , but is converted back into electrical energy. This reverse conversion has been tried and tested from other applications.

There are already z. B. cog railways such as the Zugspitzbahn , but also elevators , which generate electrical energy when moving downwards and feed it back into the network. Here are regenerative braking ( Rekuperationsbremsen ) or frequency used. In this respect, these systems are already lifting storage systems. The physical effect gives rise to an advantage over other storage power plants: Since the weight of the storage mass is almost independent of the height, the output of the power plant is independent of the "level". In addition, they do not lose any energy during their service life, and the performance can be accessed very quickly at any time; Such a storage power plant could therefore also be used as an emergency power supply . The size of the generator and the resulting starting current or the ramp of the upstream frequency converter are limiting for the starting time and the output of the power plant .

Location

In order to maximize the available height difference, which is directly proportional to the storage capacity of the power plant, it is often proposed to integrate lifting storage in thrown mining shafts . Such shafts, which normally have a height of several hundred, often well over a thousand meters, also have the advantage that the infrastructure of the previously existing shaft conveyance can be used to some extent. Winding machines with a capacity of up to 6 MVA are state-of-the-art. B. in the Kaiser Wilhelm shaft .

As an alternative to underground shafts, installation in the open sea would also allow strokes of several hundred meters or in deep-sea areas up to well over a thousand meters. Because of the depth of the water, the power plant would have to be built on a large floating body, the buoyancy of which bears the weight of the power plant and storage mass. The effective weight of the storage mass is then reduced by the buoyancy of the water, which on the one hand reduces the required floating body, but on the other hand also reduces the storage volume. Problems would arise, comparable to other floating structures such as semi-submersible drilling rigs , due to high swell, wind, ocean currents and other weather conditions as well as the necessary electrical connection to the mainland. In the case of floating construction, the combination with a floating wind turbine would be an option because of synergies .

Film documentaries

• campus TV: Ultra energy storage for solar and wind energy, 2011

Individual evidence

1. ↑ ^{a b c} Werner Rau: Lifting storage power plants - Lifting storage use gravity. Retrieved March 25, 2011 . 
2. ↑ ^{a b} Patent DE102007057323 : Lifting storage power plant as a special form of a storage power plant, which is used to store electrical energy by converting it into potential energy of a lifting mass. Published on June 4, 2009 , inventor: Jürgen Pesch. ‌
3. ↑ Frank Escombe: Logan Stone Energy Storage. (No longer available online.) Sure Insight, formerly the original ; Retrieved March 29, 2011 (in English).  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.    
4. ↑ Patent DE102011012594 : Offshore hydraulic energy storage. Published on August 30, 2012 , inventor: Robert Klar / Markus Aufleger. ‌
5. ↑ Patent KR20130100965 : SYSTEM FOR STORING POTENTIAL ENERGY AND METHOD FOR PRODUCING SUCH A SYSTEM. Published on September 12, 2013 , inventor: Eduard Heindl. ‌
6. ↑ Achim Gottscheber: Lifting storage power plant - an alternative to storing electrical energy. (No longer available online.) SRH Hochschule Heidelberg , archived from the original on February 14, 2011 ; Retrieved March 25, 2011 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
7. ↑ Markus Aufleger: Hydraulic energy storage. Retrieved May 7, 2015 . 
8. ↑ Tinkerers make gradient power plants possible without a gradient . In: Spiegel-Online , January 16, 2018. Retrieved January 16, 2018.
9. ↑ Peter Höllrigl: New super battery - Can this tower secure our energy future? In: srf.ch . January 3, 2020, accessed January 3, 2020 . 
10. ↑ Bernward Janzing : New energy storage: Concrete barrels on the crane rope . In: The daily newspaper: taz . December 22, 2018, ISSN  0931-9085 ( taz.de [accessed February 7, 2019]).
11. ^ Lena Masri, Simon Jessop: Vision Fund makes $ 110 million bet on renewable energy storage. In: reuters.com . August 15, 2019, accessed January 3, 2020 . 
12. ↑ powertower.eu
13. ↑ Deutschlandfunk , Forschung Aktuell , November 19, 2013, Thomas Gith: deutschlandfunk.de: New Storage for Energy from Wind Power Plants (November 21, 2013)
14. ↑ Eduard Heindl: Idea and function of a very large energy storage system. (No longer available online.) Archived from the original on July 27, 2014 ; Retrieved July 22, 2014 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
15. ↑ Robert Klar: Offshore Hydraulic Energy Storage. Retrieved June 17, 2014 . 
16. ↑ Jürg Nipkow: Electricity consumption and savings potential in elevators . SFOE Electricity Program , DIS Project No. 101106, Final Report November 2005. Ed .: Swiss Agency for Energy Efficiency. Federal Office of Energy ( full text [PDF; 769 kB ]). Full text ( memento of the original from October 7, 2009 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
17. ↑ Industrie-Service Argauer (ed.): Energy recovery, an environmental contribution that pays off! ( Online at henning-gmbh.de [PDF]).
18. ↑ Carriers and shafts. (No longer available online.) RAG Mining Solutions , February 2011, formerly in the original ; Retrieved March 25, 2011 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.    
19. ^ Heinz - Rüdiger Lenk: The Kaiser Wilhelm II shaft. Accessed on March 25, 2011 .