One of the companies bidding for a 100-megawatt storage plant in South Australia is standing by claims that its technology could beat lithium-ion.
Adelaide-based 1414 Degrees, named after silicon’s melting point (and formerly known as Latent Heat Storage), claims to have developed a molten silicon thermal energy storage system (TESS) that can store 500 kilowatt-hours of energy within a 70-centimeter cube.
This is 36 times the capacity of a 14-kilowatt-hour Tesla Powerwall 2 lithium-ion battery, the company claims. 1414 Degrees says it could build a 10 megawatt-hour plant for around AUD $700,000 (USD $528,000), or a tenth of the price of a Tesla battery-based project.
Kevin Moriarty, executive chairman at 1414 Degrees, made headlines in Australia after saying his company’s technology could spell the end of lithium-ion batteries. “There’s no comparison,” he told the Australian Financial Review. “Except for a few specialized circumstances, it will make them totally uneconomic, frankly.”
If there's any lesson to be learned over the last decade, it's to be wary of these kinds of sweeping claims from startups.
News reports omitted one important detail: The most obvious way to generate electricity from molten silicon would be to boil water and make steam to drive a turbine. In this case, the efficiency would be like that of a combined-cycle gas turbine, at around 30 percent.
Moriarty told GTM that 1414 Degrees could achieve storage efficiencies of up to 90 percent, but only when used for combined heat and power generation (CHP).
“Our technology provides high-flow, very hot air for multiple uses in addition to electricity,” he said, “meaning we can achieve 80 percent to 90 percent efficiency. We can recover most of the energy stored, which other technologies cannot, except pumped hydro.”
The theoretical Carnot efficiency for stored energy at 1,400º C is at least 84 percent, he said.
“Even where heat is not a primary requirement, our systems are so low-cost, long-lasting and high-power-rated that they will provide the required service at much lower cost than batteries,” he claimed.
Julia Attwood, an emerging-technologies analyst at Bloomberg New Energy Finance, confirmed that 1414 Degrees could only really claim superiority over lithium-ion in a CHP setting.
“The current electrical efficiency of 1414's prototype is 31 percent,” she said, “but they're hoping to get to 40 percent or 50 percent for their commercial units. That's a pretty low efficiency compared to lithium-ion batteries, which are over 80 percent.
“However, if you're using the TESS not just to supply electricity but also heat, then the efficiency improves to over 80 percent, as you're removing the turbine from part of the equation.”
A TESS unit providing district heat in combination with grid services could indeed be competitive with a battery, based on efficiency, she said.
And beyond CHP, there may be a couple of other areas where the 1414 Degrees TESS has an edge over lithium-ion batteries, which make up the vast majority of energy storage installations.
One is lifetime, since a TESS is unlikely to lose its ability to store thermal energy over time. And another is duration; although Attwood said 1414 Degrees was lagging on this front.
“The true gap in the storage market is in long-term energy storage,” she said. “1414 is attempting to target this gap, but it's missing the mark a bit, as its TESS can only store energy for a week, rather than the months that are really needed for seasonal storage.”
Lithium-ion batteries can technically store energy for months, she noted, but “it's just very economically inefficient to use them that way.”
Meanwhile, the long charging and discharging times of a TESS also mean it can't participate in lucrative short-duration grid services.
1414 Degrees is currently planning an AUD $10 million (USD $7.5 million) public share issue in mid-2017 to finance the building of two 200-megawatt storage plants. (Along with making such grandiose claims before commercialization, an early public offering is also not a historically good sign for a cleantech startup.)
It is also said to be among the bidders for a 100-megawatt storage plant contest in South Australia, sparked by Tesla.
In March the company said it had raised AUD $2.5 million (USD $1.9 million) in seed funding “from professional investors in a heavily over-subscribed offer” for a 10-megawatt-hour commercial-scale pilot and its stock market launch.
“Overall, 1414's silicon TESS system is an interesting technology and clearly an improvement over molten salt storage, but it will probably only be useful in a specific niche, with a wider system designed around it," said Attwood.
This story was amended to reflect the actual efficiency of a steam-condensing turbine.