Climate swords to plowshares: Hyme re-jigs old power plants for clean energy
Denmark's Hyme Energy wants to save decommissioned fossil-fuel heat and power plants by repurposing them as super-cheap renewable energy storage and release facilities, using cutting-edge molten salt technology borrowed from the advanced nuclear sector. Its first plant will be online by 2024.
There's no point throwing out the baby with the bathwater; yesterday's dirty power plants have plenty to offer tomorrow's clean energy grid. They've already got billions of dollars' worth of infrastructure in place, like well-established connections to the power grid, steam turbines, transformers and the like, and the right clean energy projects can make the most of what's left behind.
Earlier this year, we wrote about MIT spinout Quaise, and its plans to re-power old coal- and gas-fired plants with ultra-deep geothermal energy. But to get there, it's going to need to drill holes much deeper than anyone's ever managed, using bleeding-edge energy beam technology developed for heating up plasma in nuclear fusion experiments. That'll take time.
Hyme's plan is simpler. It'll concentrate on combined heat and power plants, replacing the heat from combustion with heat from hydroxide molten salt energy storage systems. These will charge up using excess energy from the grid, and discharge by sending heat out directly for domestic and industrial use, and also by driving steam turbines to put electricity back into the grid when renewable production is low.
The system will place two tanks either side of a boiler. The hot tank will hold the salts at temperatures around 700 °C (1292 °F), and the salt will loop through the boiler to heat up water and create steam. The steam will drive turbine generators before being piped out for district or industrial heating, and the salt will return back to a cool tank at about 350 °C (662 °F), where heating elements will get it back up to temperature. The company tells Recharge that in combined heat and power applications, its round-trip efficiency is close to 90%.
The system relies on proprietary corrosion control technology borrowed from sister company Seaborg Technologies. We've written before about Seaborg's remarkable plan to mass-produce advanced nuclear reactors, stick them on floating barges and deploy them all around the world. These reactors will use molten sodium hydroxide as a liquid moderator, allowing for a super-compact reactor running at very low pressure, and which promises a relatively safe and easy cleanup in the event of a catastrophic accident or terrorist bombing.
Sodium hydroxide is a super-cheap salt produced from seawater as a byproduct of chlorine production. It's easily available and will pose no barrier to scaling up the Hyme energy storage solution. But it's also known as drain cleaner – a powerfully caustic alkaline substance that can be particularly corrosive to metals at high temperatures.
"The key technology enabler here," says the company, "is the chemistry control that limits the corrosion of structural materials in contact with the molten salt. The chemistry control is developed by Seaborg and is the core IP in the company. Hyme has been granted the rights to mature the concept and take it from the laboratory to a global market within energy storage."
So it'll be fascinating to learn how long these facilities will last, since the answer is of direct relevance to Seaborg's nuclear products.
The first Hyme plant will be relatively modest, and is set to open in 2024 on the Danish "energy island" of Bornholm. It'll store and release up to 20 MWh of energy, with a maximum output around 1 MW. Once this is operational and proven, Hyme plans to scale up into gigawatt territory, with relatively compact plants capable of storing between 200 MWh and 10 GWh – representing between four and 24 hours of full-load energy discharge.
Hyme doesn't nominate a a projected Levelized Cost of Storage (LCoS), but according to Seaborg, "Hyme expects to be able to halve the price of long-term and large-scale energy storage facilities independently of geographical constraints." That would certainly make for a transformational technology.
Source: Hyme Energy
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I’m no fluid dupynamics, thermodynamics or chemical expert, but that 90% percent efficiency claim smacks of snake oil. Electrically heating the salt, storing the heat, then later making steam, to spin a mechanical turbine, to drive a generator to make electricity with only 10% loss? Hmm.
It might be a poor choice for building new facilities, but since there is a strong demand for energy storage (including district heating), repurposing existing facilities might be economical, and can be implemented quickly. This could help tide us over until better storage systems are developed and constructed. Some intermittent energy production projects might be on hold due to lack of adequate energy storage.
In any case, the reuse of the turbine output steam is clever and valuable.