The energy modelling team worked with a South African energy venture developing a new technology for reliable and cost-effective long-duration storage of energy from intermittent solar and wind. 

The proposed solution is a gravity storage system that uses power from renewable sources to raise and lower weights, in the process storing and releasing energy over longer cycles than can be achieved with chemical battery technologies. Not only does the ‘gravity battery’ offer the potential to store energy over longer time periods, but it does so far more cost efficiently than would be possible with alternatives.

The technology is being trialled in the South African market in collaboration with the mining industry, where high energy consumption and an ongoing energy crisis provide an ideal opportunity to test the potential savings.


To support our client with effective market engagement we worked closely to develop the investment case for this new technology. Critical for this was an ability to model the performance of a storage installation and establish the attractiveness of the associated economics.

The study focused on assessing the value of the storage technology when integrated into pre-defined renewable energy development plans (carbon neutral goals).

Our analysis involved modelling the renewable production potential from several candidate mixes of solar and wind facilities and then simulating how the available energy could best be used to contribute directly to load and charge the gravity battery system. The objective was to identify optimal charging and discharging strategies when taking account of other commercial factors such as:

  • PPA pricing for the solar and wind procurement
  • variable tariffs for any remaining grid inputs, and
  • all other charges associated with utilisation of the grid infrastructure.

A further key factor to consider was the existing and planned renewable developments, which defined the modelled scenarios, and significantly influenced the techno-economic feasibility of the proposed storage systems.


Modelled use case

Whilst there are multiple commercial use cases for the new storage technology, our work focused on quantifying the potential for reducing energy costs. To do this, our consultants modelled real-world scenarios characterised by:

  • An off-taker with a known energy consumption profile.
  • Potential to co-locate utility-scale solar at the off-taker’s mining facilities.
  • Potential to source additional wind generation from off-site locations, and
  • Installation of a properly specified gravity storage system.



By the end of the initiative our client had detailed, quantitative evidence supporting a positive investment case for the new storage technology, complete with a high impact visual story telling aid to further enable effective market engagement.

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