One solution to variable renewables is to create customers that have no problem with ramping up and down production along with the power. In fact, when the wind and solar is producing too much power for the grid it can be bought very cheaply, making intermittent customers very happy. Jim Conca describes a new design for a Chlor-Alkali Chemical Plant that can “idle” without critical components of the plant degrading – the main reason for a plant to be “always on”. Energy costs are 75% lower than the traditional design. By abandoning the “always on” fossil fuel source, emissions are much lower too. Such plants produce chlorine, caustic soda and hydrochloric acid. The ambition is to extend the innovation to the production of steel, titanium, aluminium, magnesium, silicon and other chemicals. Conca observes that instead of curtailing wind and solar we should be designing curtailable industries – plants that can turn off and on as power is available.
Coupling simple earth materials with clean non-fossil energy allows basic commercial chemicals, like chlorine, caustic soda and hydrochloric acid, to be made without carbon emissions or toxic waste, at lower costs than normal. Even cement can be made without emitting CO2.
With our focus on the global pandemic, it’s good to be thinking of a better future. The temporary drop in carbon emissions from the pandemic lockdown of industrial and commercial activities around the world has shown what is possible by decarbonising society.
And how quickly the ecosystems can respond.
One of the biggest carbon emitters, and general polluters, is our chemical and manufacturing industries. Manufacturing without carbon would be a huge step in the right direction.
This idea is embodied in a new company called Achíni Scientific, brain-child of Deóis Ua Cearnaigh and Shannon Lark. An Apache term for “We will not abandon the children”, Achíni combines special hardware and software components that allows steel, titanium, aluminium, magnesium, chemicals, and silicon to be electrochemically produced using a variable power source, like wind.
Making use of electricity fluctuations
But this goes beyond just purchasing power from a renewable source. It strategically takes advantage of electricity fluctuations while solving the energy storage problem.
Their first project is called Aztlán (pronounced “Oz” and “Lawn” and refers to the Aztec Garden of Eden in Nahuatl). Aztlán is a green Chlor-Alkali Chemical Plant using the abundant low-cost, but intermittent, wind energy from West Texas to run electrochemical processes to make these chemical products without using fossil fuels or clean water.
Traditional methods: emissions, waste
Traditional Chlor-Alkali Chemical Plants use fossil fuels for the large amount of energy required (see figure below). Fresh water is also used for power, chemical production and cooling water. Salt deposits are used as a source of NaCl. The combination produces chlorine, caustic soda and hydrochloric acid, valuable products.
Depleted brine wastewater is usually dumped into rivers, electrochemical sludge goes into waste barrels for disposal, waste minerals go into landfills and CO2 goes into the atmosphere.
A “green” Chlor-Alkali Chemical Plant
In the Aztlán Chlor-Alkali Chemical Plant (see figure below), wind energy provides relatively green electricity, brackish (salty) water is pumped out of the ground and desalinated into fresh water, several million gallons a day. This waste brine from the desalination is used to make the chlorine, caustic soda and hydrochloric acid products, and hydrogen is formed as a by-product.
The intermittency of renewables is usually a problem, one that we try to use storage to handle. But wind doldrums can last many days to weeks, and storage cannot handle that much energy without unimaginably high costs.
Therefore, traditionally electrochemical cells can’t be turned off, as bad things happen chemically. That’s why traditional plants basically never shut down. They require constant energy like fossil fuel, and cannot use intermittent sources like wind. In fact, most plants must have spinning reserve power capacity as backup, usually idle gas turbines.
Ramping the manufacturing process
Enter Achíni’s special ramping technology, a way to put the system in stasis when no energy is available. Instead of fitting the power to the process, Achíni fits the process to the power. The Aztlán Chlor-Alkali plant can ramp between ~10% and 110% capacity on a five-minute timescale.
It does this by keeping the structure and chemistry inside the electrochemical cell that is about the same as that during operations – maintaining the double-layer charging capacitance through sub-potential polarisation (controlling the charge across the electrodes), operating heating and cooling loops to maintain thermostatic conditions at any production level, purging active species, while resupplying inactive species to maintain osmostasis, controlling the dissolved chemicals at any point in time.
Idling the plant
These systems and similar refeeding hardware allow the plant to maintain an idle, non-producing state without reverse currents or pressure failures, keeping constant temperature, salt ion concentration gradients, and other critical conditions during the time necessary to wait until new energy is provided as the wind or solar comes back up, without letting the system relax back to the ground state that would ruin the system, as happens in traditional plants.
The plant basically acts as a huge capacitor.
Cutting energy costs and emissions
This approach enables electrochemical technologies to go beyond simply purchasing power from a renewable source; it strategically takes advantage of electricity fluctuations while solving the energy storage problem without batteries.
By solving these problems, the energy cost of the plant is reduced by 75% or more. The direct offset of a million tons of CO2 or so per year, with the potential for millions more in downstream industries, is an added bonus.
Some key proprietary steps also allow the plant to use mechanical vapour recompression at ambient temperatures to desalinate brackish or salty water to create distilled water, thus not requiring heat from fossil fuel or clean water.
The waste brine is then used to make the industrial chemicals using green energy, in this case wind.
The initial CAPEX is larger than normal, but the operating costs are substantially lower due to the energy savings. One of the by-products is green hydrogen, which is used for power on-site as well as sent to the grid. Another by-product is caustic soda.
Chemicals: the perfect product for variable renewables
Aztlán’s model is scalable, pairs with wind and solar on-or-off grid (before-or-after the meter), and does not require base load energy sources. The plant’s returns are autonomy from the power markets so the margins on power provide strong economic incentives. Aztlán will utilise this renewable power to produce easily shipped commodities with indefinite shelf-life, bypassing congestion rents and electrical transmission constraints while solving the energy storage problem.
In parts of the Southwest, especially in west Texas, wind congestion causes power to drop to negative prices about a quarter or more of the time, mostly at off-hours (source: ETA). It’s why so many high school football stadiums are paid to keep their lights on all night. Being immune to energy price swings is quite a strategic property to have in a competitive industry.
Traditional industries cannot run idle through peak hours, nor can they be turned off and on as needed. In any renewable energy future, industry must have dispatchable, or spinning, loads acting as reserves that respond to the power, not the other way around. This is what Achíni does – it’s an electrochemical clutch, like on a car, that allows the plant to spin on neutral.
In fact, if the United States, and the world, intend to go renewable in any significant way, society has to embrace curtailable industries – plants that can turn off and on as power is available.
If we want to go green, this is what we need to do.
James Conca is an earth and environmental scientist and a regular contributor to Forbes magazine