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Gravitational potential energy (device)

Creating Gravitational potential energy (device)

Idea

Find new applications to level out the inbalances of intermittend energy generation.

The seed of this page is the article Storing unsteady energy, like photovoltaically generated electric energy, as potential energy by Nadja Kutz.

Leveling out within smart grids may not be sufficient

Electric energy generated by photovoltaical, or thermo elements - here abbreviated as photosolar or thermosolar energy or -electricity, as well as energy generated by wind is rather unstable and in some sense unsteady and unreliable, in particular the unpredictability of weather provides still a rather big uncertainty. Thus these energy forms shall be abbreviated as “unsteady energy” or intermittend energy. It may not in all cases be possible to level out their unstability within a smart grid. Levelling out inbalances will especially be a problem if the share of unsteady renewable energy is big in comparision to other (renewable) steady means of electricity production.

Further possibilities of gravitational potential energy storage are not sufficiently mentioned in the literature (as of Feb. 13 2012)

It seems to be well established that for example lifting goods in warehouses at times where there is an electricity overload may be a method to balance unsteady electrical energy within a smart grid via potential energy. Using water reservoirs may be another established method. For example Lenzen [Lenzen2010] p. 547 writes:

As with wind power, solar power is well suited for demands that are insensitive to temporal variations in electricity output, such as water pumping for irrigation, or vehicle charging. Matching such loads with variable solar resources can overcome restrictions related to limited capacity credit.

These applications look however more like “niche”- applications. That is the “storing into potential energy” seems not be seen as a major possibility to make unsteady energy more reliable. So for example one finds in Weissbuch p. 45 under R&D needs, opportunities and recommendations:

Electricity storage and transport: supercapacitors, supra conductors, electrolysers should be further developed.

Lenzen writes about the storage of wind energy (p. 541):

Dedicated load-leveling applications such as desalination, aluminium smelting, space and water heating, or a chargeable hybrid vehicle fleet can deal with hourly variations in wind power since they only require a certain amount of energy over a period of many hours [202,215]. For example, large-scale vehicle-to-grid technology can significantly reduce excess wind power at large wind penetration and replace a significant fraction of regulating capacity, but as Lund and Kempton [239] shows in a study for Denmark, electric vehicles would not nearly eliminate excess power and CO2 emissions, even if they had long-range battery storage.

The DLR writes about an envisaged portfolio of future energy generation (p. 119): The different technologies of our portfolio contribute differently to secured power: fluctuating sources like wind and PV contribute very little, while fossil fuel plants contribute at least 90 \% of their capacity to secure power on demand.

As one reason for this choice it is written (p.120) that: PV power is strongly fluctuating and only available during daytime. There is no contribution to secured power, but a good correlation with the usual daytime power demand peak of most countries. PV is specially suited for distributed power supply.

In Without the hot air (p. 186 - 202) David McKay mentiones as options to store into potential energy via flywheels and water storage. He writes:

However, the capacity of the British hydro fleet is not currently big enough to make much contribution to our slew problem (assuming we want to cope with the rapid loss of say 10 or 33 GW of wind power).

and

How to ride through these very-long-timescale fluctuations? Electric vehicles and pumped storage are not going to help store the sort of quan- tities required. A useful technology will surely be long-term thermal storage.

Tom Murphy writes on the blog: Do the math

Intermittency is the Achilles Heel of solar PV, requiring storage solutions if adopted at large scale.

Possible applications, brief suggestions

In the article it will be argued, that the option to store unsteady energy via potential energy should be taken more into consideration. A focus on photosolar energy will be made for brevity reasons. The suggested examples are mainly intended for giving an outlook on the possible scope of storing via potential energy. The examples are thus in particular not exhaustive, nor exclusive.

The reader is kindly requested to read the article Storing unsteady energy, like photovoltaically generated electric energy, as potential energy. Further parts of the article and examples may eventually be included here on Azimuth at a later time.

The article had been featured at the blog Tikalon by Dev Gualtieri.