We covered this story back in 2013 and it seems they have moved forward and have been commissioned to build a grid connected system. Gravity is a great way to store energy. It also comes at half the cost of any other known energy storage system.
These Concrete Gravity Trains May Solve the Energy Storage Problem
Energy grids fluctuate throughout the day as demand and production increase and decrease. Usually, during peak hours, demand for electricity is close to or exceeds the production capacity at that time. During off hours, usually in the night, production capacity far exceeds what is being drawn from the grid. This results in a natural unsteadiness to the energy grid and experts have been experimenting with ways to make sure that the lights always stay on.
One of the most common ways that energy is stored in large scale for the grid is through pumped hydro electric storage dams. The Taum Sauk reservoir is one of these types of “physical batteries” that essentially stores excess energy through potential energy in water mass. When there is excess power, water is pumped to the high elevation of the reservoir. When there is too little power, water is released thus generating electricity again. While this is a current solution, it is only suitable in the perfect geographical location.
One California company has come up with another solution, the Advanced Rail Energy Storage System, or ARES for short. This technology is essentially a land based train that takes excess electrical energy and stores it through potential energy gained in large train masses. In rudimentary terms, it’s the equivalent of pushing a large rock up a hill when you have the energy so you can push it down later when you need more energy.
ARES technology uses rail cars that essentially carry extremely heavy blocks of concrete to the top of a hill or specific grade. The rail cars can be powered by electricity off the grid during off-peak hours when there is little demand. During peak hours, the rail cars are then released from the top of their grade to move down the hill, transferring potential energy into electrical energy through regenerative braking.
While the technology may seem too simple to work, the company claims an 80 percent efficiency rate of energy input to energy output through storage. Each car can deliver constant power for up to 8 hours.
The Nevada Public Utilities Commission commissions ARES
The company has put together several test systems including a 268-meter track in California. The Nevada Public Utilities Commission has tasked ARES with constructing the grid energy system in the mountains of Nevada in order to stabilize their grid.
While it may sound absurd, in only a few years, Nevada’s electrical grid may be stabilized by a fleet of automated trains weighing 300 tons each. The company has specifically designed the system to work best on a grade of 7.2%. This allows the best transfer of energy from potential to kinetic while also allowing the trains to maintain stability. When each 300-ton train moves down the slope, it can provide 50MW of power to help stabilize the grid. In total, the track for the Nevada system will stretch 9.2 kilometers through the desert with an elevation differential of 640 meters (2100 feet).
[Image Source: ARES]
One of the most advantageous qualities to the energy system is the low cost compared to other energy storage techniques. The company states that it can be implemented for half of the cost of the cheapest electrical energy storage system. The system also requires no external input in the form of fuel or water, it purely operates from the energy coming from the grid. These qualities are impressing many electrical companies across the world and have taken a fairly rudimentary design and turned it into a possible universal solution
Santa Barbara, California-based company Advanced Rail Energy Storage (ARES) has come up with a land-based alternative that would provide grid scale energy storage using electric locomotives.
ARES recently held an open day at its R & D facility in California. Built as a proof of concept for its patented Regulation Energy Management (REM) system, the pilot plant is designed to even out intermittent power supply from a neighboring wind farm. This facility features a pilot vehicle that weighs 12,500 lb and runs on that is 880 ft in length.
WHY IS ENERGY STORAGE TECHNOLOGY SO IMPORTANT
The following video from ARES explains why storage is important and outlines a technical description of the technology
ARES Supports the Expanding Renewable Energy Market
Although pumped hydro is the most widespread energy storage technology currently in use for utility applications, the potential for expansion of pumped hydro is severely limited
by the high capital cost of these facilities together with the limited availability of suitable
geographic locations with adequate water supplies. Permitting pumped hydro projects is
also difficult and prolonged.
Unlike pumped hydro technology limitations, there are many locations across the US and
around the world where ARES technology can be deployed with minimal environmental
implications. Utility-scale energy storage currently represents approximately 3 percent of world electric power generating capacity; however this capacity must increase dramatically to accommodate an increasing reliance on low-carbon energy generation technologies.
Solar and wind generation sources are fundamentally intermittent and cannot vary output
in response to changes in demand. Peak generation may occur when the output cannot be
economically used. The efficacy of these energy sources depends on storing energy when
demand is low so it can be economically deployed when demand is high. Energy storage can
also be used to increase the efficiency of traditional generation systems. ARES high capacity storage can be combined with renewable energy and traditional power plants to provide overall system flexibility that would not be possible with other forms of energy storage. ARES systems and technology are ideally suited for arid regions where existing transmission capacity is attempting to keep up with the increasing deployment of large-scale wind and solar generation facilities. ARES facilities promote the growth of renewable energy by stabilizing its input into the grid.
ARES is a rail-based technology that stores energy by raising the elevation of mass against the force of gravity and recovering the stored energy as the mass is returned to its original location.
Specifically, ARES energy storage technology employs a fleet of electric traction drive shuttle-trains, operating on a closed low-friction automated steel rail network to transport a field of heavy masses between two storage yards at different elevations.
ARES facilities integrate significant recent advances in motor/generator traction drives and power control technologies with proven rail technology to produce a reliable and highly
capable system that approaches an 80% charge / discharge efficiency.
The facility designs are highly scalable in power and energy ranging from small installations
of 100MW with 200MWh of storage capacity up to large 2-3GW regional energy storage
systems with 16-24GWh energy storage capacity. ARES technology does not require the use of water nor does it release noxious emissions
PERFORMANCE AND COST
An ARES facility will provide the full range of energy storage capabilities generally associated with pumped-storage hydro at approximately 60% of the capital cost and at a significantly higher efficiency. Additionally, ARES has system features which are not traditional to competing forms of energy storage, including but not limited to the following attributes:
Reactive Power Production – The shuttle-trains onboard Dual 3-Level Active Rectifier/Invertors are capable of supplying 25% of generated system power as reactive power for grid VAR support in full discharge mode and in excess of 100% of system power as reactive power while synchronized to the grid in standby.
Heavy Inertia – When in direct grid synchronization the ARES shuttle-trains provide beneficial heavy inertia — augmenting grid stability against the loss of heavy generating facilities and increasing reliance on solar energy.
High Efficiency Regulation – While providing Regulation-Up and Regulation-Down support to the ISO a separate dedicated pool of loaded ARES shuttle-trains are available to dispatch from mid-system elevation complying with ISO regulation commands without having to overcome the efficiency loss of operating on pre-stored energy. As such an ARES facility is able perform a round-trip regulation Reg-Up/Reg-Down command at over an 86% operating efficiency.
Variable Output at Constant Efficiency – Unlike CAES and pumped-storage hydro there is no loss of system pressure during discharge. ARES system efficiency is constant over the full range of discharge and power output.
This technology could be a game changer given the restrictions and storage penalties being imposed on new wind and solar farm development. More importantly it could be deployed as a stand alone for stand alone and smart grids. Imagine a small town or community with wind or solar having this as there main storage, no need to connect to the grid at all.
The devil will be in the detail and the economics of storage. As we have seen companies like EOS with their battery technology are now around 10c kWH storage. It will be interesting to see how the numbers stack up on this in comparison.