The ARES North America test at the Gamebird Pit site in Nevada showed that the GravityLine system can move two masses with a combined weight of approximately 340 tonnes up a slope with an angle equivalent to roughly 55%, using a stationary motor and a chain system. However, the actual height traversed by the masses—approximately 36 meters—produces only about 33 kilowatt-hours of total stored gravitational energy.
These figures are the focus of Michael Barnard’s assessment in CleanTechnica, which takes a critical view of the viability of storing energy using solid masses moved up and down along rail tracks. The basic equation is simple: gravitational energy equals mass multiplied by gravity and height. The system can deliver power of up to several megawatts for a short period while the masses descend, but instantaneous power does not mean that it possesses a large energy reserve.
What Did the ARES Test Actually Demonstrate?
According to the article, the Gamebird test changed an important engineering detail compared with an earlier assessment published in 2024. The earlier assessment expected the forces on conventional cables used in inclined systems to limit the size of the masses that could be moved, whereas the ARES design overcomes this constraint by using a chain-driven system.
However, the author believes that the main commercial problem has not changed: the low energy density of solid masses means that storing useful quantities of electricity requires an enormous material inventory. To avoid judging the concept based on Gamebird’s limited height, Barnard assumed a scenario with an effective height of 400 meters and a plant producing 20 megawatts for 20 hours, equivalent to a storage capacity of 400 megawatt-hours.
In this scenario, the system is no longer merely a cheap way to move gravel up a slope. It requires hundreds of thousands of tonnes of masses distributed across specially designed carriers, storage yards at the upper and lower levels, operating tracks, stationary motors, transport and control systems, maintenance corridors, and a degree of operational redundancy that ensures access to the stored energy when some equipment fails.
A Different Comparison with Pumped Hydro and Batteries
The article compares this design with pumped-hydro storage, which uses the same gravitational principle but does not require a separate structure for each part of the mass. Water settles in reservoirs and moves through a shared channel or pipe; it does not need a metal frame, wheels, or a parking position for each unit of mass.
Lithium-ion batteries, meanwhile, require energy-intensive materials manufacturing, but benefit from permanent factories and a global supply market that allows a storage-project developer to purchase modular units rather than establishing a manufacturing system for heavy equipment near every geographically suitable site.
In the author’s view, rail-based gravity storage combines the disadvantages of both models without obtaining all of their advantages: it depends on a suitable geographic location, like pumped hydro, but adds a large inventory of moving equipment, as in manufactured industrial systems. The article notes that every carrier must be manufactured, inspected, scheduled, and maintained, and that its failure could make part of the stored energy unavailable even if the mass itself remains at an elevated position.
What Changes in Practice?
The calculations presented show that increasing the height alone does not solve the problem. If the system rises to 100 meters instead of 50 meters, the energy per mass can theoretically be doubled, but achieving the same energy at a lower height requires increasing the mass in proportion to the difference. Barnard argues that this means manufacturing thousands more steel cars filled with concrete and assembling them at the upper and lower levels.
The article also points out that the quarry provides relatively favorable conditions, such as the presence of aggregate, roads, and disturbed industrial land, but it does not necessarily provide significant height. Conversely, a high-elevation site may lack cheap aggregate, heavy industrial infrastructure, transmission lines, suitable storage areas, or easy geotechnical conditions. Therefore, it is not enough to find a steep hill; a set of conditions must be available simultaneously.
The article also mentions that Britain’s 2026 long-duration storage procurements included lithium-ion battery projects lasting more than ten hours, weakening the assumption that 20-hour storage automatically leaves substantial room for mechanical alternatives.
Editorial Reading
The core value of the material is not proving that the ARES system is incapable of movement; the test proves the opposite. The more important question is whether the energy produced by this movement justifies the material and operational infrastructure required to provide a major grid service. The article offers a sharply negative answer, which is the author’s viewpoint rather than an independently documented conclusion here.
Some questions remain open, particularly the actual cost per megawatt-hour, equipment lifetime, maintenance plan, and embodied emissions. Barnard states that he did not conduct a detailed emissions calculation for this project, but expects the use of steel, cement, and heavy machinery to create a substantial carbon burden. The material should therefore be read as a critical analytical assessment based on physics and design requirements, not as a completed economic or life-cycle study.