Energy Storage - Think Big, Think Cheap

The search is on for grid level storage technology capable of meeting the demanding performance requirements of the grid.
Published: Wed 26 Mar 2014

The need for grid energy storage is growing fast and many new start-ups are responding to this need.

However, much to the frustration of these start-ups, the utility-scale market is going to take time to establish itself. This is mostly due to the fact that utilities are conservative and risk averse. According to Pike Research, reduced costs, regulatory support and business model clarification is required for utility-scale storage to become established.

Pike Research values the global market at US$1.5 billion by 2015 and this is a relatively conservative forecast. Lux Research, for instance, predicts the global grid-scale storage market to be worth US$114 billion by 2017 and Boston Consulting Group forecasts a US$400 billion market by 2020.

Few markets have demonstration projects for utility-scale battery based energy storage. They include China and the US.

Distributed storage projects escalating

In contrast, distributed storage demonstration projects are escalating globally even though they require fewer batteries than utility-scale storage applications. In countries such as California, Japan, South Korea and the UK, the government is providing support to some projects that will pilot battery storage. This will alleviate pressure on the low voltage (LV) network that the increase in PV systems, heat pumps, electric vehicles and other low carbon technologies will cause.

However, it seems the real value in the majority of future storage installations could lie in distributed storage on the semi-urban network. Solar suppliers and companies supplying energy storage systems and technologies are beginning to collaborate in order to develop innovative and cost-effective storage solutions.

Today the most popular primary applications for advanced battery in stationary storage applications is for load levelling/peak shifting, where typically sodium-sulfur (NaS) batteries are used. Other primary applications for batteries include integration of renewables, where NaS as well as flow and lead acid batteries are used. For frequency regulation as the primary application, lithium ion (l-ion) batteries are being used. Nickel cadmium (NiCd) batteries tend to be favored where spinning reserves is the main application. In Q2 2012, nearly 250 MW of installed capacity of NaS batteries were used for load levelling/peak shifting, according to Pike Research, with around 25 MW of installed lithium-ion battery capacity for frequency regulation applications.

New battery products developed for grid storage

As countries increase their renewables capacity to meet carbon reduction targets, many companies are responding by introducing to the market new cost-effective, scalable and safe battery technologies.

US zinc-air battery developer Eos scaled up battery prototypes (5 kW/30 kWh units) for delivery of MW-scale systems to their first customers in 2013. The company’s Aurora grid product is a 1 MW/6 MWh energy storage system for the electric grid with 1 MW optimal power for six hours with surge capability. The price of the battery for large orders is US$1000/kW.

US-based Aquion Energy was spun out of Carnegie Mellon University in 2009 to develop a low cost battery, initially for off-grid and microgrid applications. The battery is suitable for grid services such as deep-energy-daily-cycling (four or more hours), load shifting, diesel optimisation, renewables integration and transmission and distribution referral.

The Aquion battery is based on a propriety aqueous hybrid ion (AHI) chemistry. It provides long-life life, safety, durability, and low system costs. The anode consists of activated carbon, the cathode of manganese oxide and the electrolyte from water based sodium sulphate and the separator from cotton. The battery is sealed in a polypropylene casing, the cells are self-balancing and the architecture is modular and scalable, with no thermal management required, no maintenance and limited balance of system requirements.

Aquion is targeting different global markets through its various applications-rural electrification in Africa, weak grids in India, US and European grid arbitrage, as well as renewables integration worldwide.

Towards the end of 2012 Aquion entered pilot manufacturing of its batteries to meet demand for the various demonstration projects where it is sampling its batteries with potential customers. The company is now focusing on microgrid and off-grid opportunities for its batteries, where energy storage, integrated with solar, can be used instead of diesel power generation backup. The company is looking at south-east Asia, Australia, India as well as the US, where micro-grid markets are driven by the military and mission critical facilities, or even as back-up power support during extreme weather conditions. The company aims to work with system integrators and is looking for partners to sample its batteries so that the batteries can be introduced to the market as part of off-grid and microgrid energy storage systems.

Aquion then aims to shift into high-volume production to supply utility-scale projects and demand. The utility market will require batteries in much higher quantities while the microgrid and off-grid markets will provide manageable demand ahead of the company scaling production.
Ambri (formerly Liquid Metal Battery Technology) is targeting grid-scale opportunities for energy storage provided by the increased use of solar and wind.

Ambri, which was spun out from Massachusetts Institute of Technology (MIT) in 2010, is backed by investors that include Bill Gates, Total and Khosla Ventures. The company is bringing to market an all-liquid battery – a process known as reversible ambi-polar electrolysis. The design avoids cycle-to-cycle capacity fade. This is because the electrodes are reconstituted with each charge through an alloying/de-alloying process, enabling the battery to exceed 70% round-trip efficiency without degradation.

Low cost battery for grid-scale storage

Ambri’s cells consist of a molten salt electrolyte that sits between a high density metal on the bottom and a low density metal on top, when heated to melting point. In a charged state, a thermodynamic driving force between the top metal layer and the bottom metal layer creates a cell voltage. The movement of the electrons through the cell generate enough heat to keep the battery at temperature. An additional advantage is that no thermal management or control is required, ensuring the battery’s simplicity. All components are based on abundant elements. Each cell is a 16-inch square unit containing about 1200 Wh. The cells are then placed into 25 kW (100 kWh) refrigerator-sized modules. To produce commercial grid-scale storage battery banks Ambri will pack the modules into a 40-ft shipping container, rated at 500 kW and 2 MWh storage capacity.

Ambri’s strategy to commercialise its technology initially targets applications where large amounts of energy need to be stored and the battery can respond in milliseconds. This will potentially open up markets where Ambri can charge premium prices for storing and delivering electricity to the grid to make up for fluctuations in supply and demand, which will become more acute as more wind and solar power is installed.

To bring costs down, Ambri has a battery design that can be fabricated in existing factories using contract manufacturing.

The development of new, potentially game-changing battery technologies is risky. However, by exploiting abundant materials for their respective battery technologies, nascent players such as Ambi and Aquion are keeping cost at the forefront, because for intermittent renewables to become a mainstream form of energy generation, low-cost high performance storage technologies are going to be absolutely critical in the future.