Smart Grid Battery: Molten Salt Battery

The energy storage market is blossoming. Because we need renewable energy storage to supply our smart electrical grids at daily moments the demand for energy is high.

The Molten Salt Battery is a battery to watch right now. An overview. 

In Molten Salt Batteries (also known as liquid metal batteries) two liquid electrodes are separated by a molten salt electrolyte.

Characteristic of salts is that these are guiding in the liquid state because the ions are allowed to move freely. The salt and the electrodes separate themselves by their different densities and immiscibility.

Molten salt batteries are characterized by:

• cheap materials
• simple production
• the potential for an infinite life
• a high degree of safety
• a high operating temperature
• low energy density
• high self-discharge certain formulations

The composition discharge speed and have an influence on the efficiency of a molten salt battery.

Prices

In laboratory environment, the materials are priced $ 50-100 / kWh or $ 50-400 / kW with energy densities between 70 and 1100 mA / cm2. In the real world, the system cost will be about five times higher.

Aquion Energy’s batteries are about as expensive as lead-acid batteries only stands twice as long.

Attractive alternative

Due to the high demand for lithium and limited reserves, sodium as electrolyte (also called sodium-ion battery or sodium ion) is an attractive alternative because of the large supply and low cost. This advantage is partly offset by the lower energy density of sodium because it’s both heavier and less electropositive as lithium is.

Sodium-sulfur battery

Sodium-sulfur battery cells (NaS batteries) are different because they typically have a cylindrical shape (Energy Storage Association, 2015).

Hereby, the (liquid) sodium cathode is situated on the inside and the (liquid) of sulfur anode is on the outside.

The cathode and anode are separated by a membrane which allows sodium ions to pass. As a result an alloy is generated in the anode.

Sodium-sulfur batteries have a high efficiency (typically above 89%), but they must also be heated to more than 300 degrees C.

Research

The high operating temperature needed, has led to much research on sodium-sulfur batteries at lower temperatures. In theory, these cells have a much higher energy density (1672 mAh / g), but in practice researchers have to deal with chemical side effects.

A breakthrough will lead to a very suitable material for load shifting purposes, especially in combination with the high efficiency and long life.

Case studies

1. Japan

In Japan a lot of NaS is used as energy storage in the grid.

 

 

 

 

 

 

2. Aquion Energy

Aquion Energy (StartUp from Carnegie Mellon University) claims with its second generation production, to have developed a battery that is 85% more efficient with a 20 hours discharge time.

Based on their data (Aquion Energy, 2015) the Peukert number can be calculated showing that the M100-LS82 battery module is much more sensitive to the discharge rate than many other batteries. But … we must note that the uncertainty in figures is highly influencing the results. The data of Aquion seems to made rounded up.

3. Ambri

Ambri (spin-off from MIT) uses manganese and antimony. In 2012 an efficiency of 69% was achieved at a current of 50mA / cm2 (Bradwell, Kim, Sirk, & Sadoway, 2012).

Data from Ambri result in a Peukert number of 1.25 and a lifetime of 15,000 cycles.

More

Opportunities for Desalination (fresh water supply)

Over 97 percent of the world’s water supply is held either as saline ocean water or brackish groundwater reserves.

If an effective, economical desalination process could be developed, it would provide a virtually unlimited supply of fresh water, solving the world’s water issues.

Currently, most of the word’s desalination capacity is based on thermal technologies, primarily multi- stage flash (MSF) distillation and multi-effect distillation (MED). MSF and MED are popular in parts of the world where thermal energy is readily available and inexpensive.

These technologies require large thermal energy inputs to vaporize water, produce problematic brine discharges, and result in relatively low water recoveries. Significantly, these technologies have electrical requirements for ancillary operations that often approach those of Reverse Osmosis.

Molten Salt Reactor

Without more effective water resource management, fresh water availability will not keep up with demand. Molten Salt Reactor (MSR) technology offers a powerful potential solution to the impending global freshwater crisis.

MSRs produce economical, high temperature process heat that can be used for a variety of valuable applications.

A co-generation/manufacturing synergy of a MSR and coal with access to seawater or brackish groundwater can provide electricity, industrial heat, gaseous and liquid transportation fuels, fertilizer, and most importantly, clean potable drinking water for agriculture, industrial, and domestic use.

Overview Salt Battery Companies and StartUps

 

General Electric

GE is one of the largest corporations in the world is in the energy storage business as well. GE’s Durathon Battery is used for both stationary purposes and electric vehicles, including electric buses. The Durathon Battery consists of both sodium batteries and lithium-ion batteries.

Younicos

Younicos combines lithium-ion batteries with sodium-sulfur batteries and vanadium redox flow batteries in order to create something akin to a superbattery.

But its biggest competitive advantage is reportedly the software that optimizes these batteries for the best performance and greatly extended lifespan in grid storage applications.

Overview latest energy storage systems

• Smart Grid Battery: Molten Salt Battery
• Smart Grid Battery: Lithium-ion Battery 
• Smart Grid Battery: Redox Flow Battery
• Smart Grid ‘Battery’: what about Compressed Air?
• Smart Grid Energy storage: Flywheels
• Smart Grid Energy storage: UltraCapacitors

Promising systems

• New: factory sea salt batteries in the Netherlands
• Floating train at 2000 km/h set to store 10% of Dutch electricity
• World’s first ‘Solar Battery’ runs on light and air
• NEW: clean ‘battery’ Hydrogen Storage Solution
• NEW: Organic Battery for almost every Renewable Energy Power Facility
• Aluminum battery loads in 1 Minute (Stanford)
• Green Battery Using Hydro-pneumatics
• Expected: sustainable battery from sea salt
• New water tank can retain > 90 percent of the energy
• Geothermal energy from old, closed coal mines

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