By Nichola Davies
SA Water’s Glenelg Wastewater Treatment plant faced a unique energy dilemma. For one, the wastewater process generated biogas containing corrosive elements, which was being converted into electricity via huge, expensive and high-maintenance engines. Secondly, the inability to time-shift energy meant paying high prices when buying off the grid when demand wasn’t being met by the biogas. Thirdly, SA Water needed to produce hot water and heat for industrial operations.
So, they approached 1414 Degrees to design a unique energy storage system that would meet all of their needs. Accepting the challenge, the world’s first commercial pilot of the biogas Thermal Energy Storage System (GAS-TESS) technology was up and running in less than two years. Here’s how they did it.
1414 Degrees Thermal Energy Storage System (TESS) is a molten silicon energy storage system that has several unique characteristics, the primary one being its ability to at large scale harness the very high energy ability of silicon.
Because silicon melts well above 1000 degrees, you need special materials and environments. 1414 Degrees Executive Chairman Dr Kevin Moriarty explains, “what we’ve got to do is get energy into it at a high rate and get it out again efficiently to be useful again.
“So yes, people do store energy with hot rocks and molten salt but these are all at temperatures where you can use steel and other components. Those would melt at the temperatures we operate at.
“So why do we bother? Well, silicon has pretty much the highest energy density of virtually any solid element on the surface of the earth. It’s very plentiful but to melt it takes a very large amount of energy. And you can then melt it and recover that, and it can be operating at its melting point, storing a lot of energy without changing the temperature.
“That was the key – finding something that had several times the energy density of existing types of solutions – around 10 times that of water and two or three times above molten salts.
“What it enables you to do is have very compact solutions for very large scale energy storage, and that’s where we’re headed.”
Originally 1414 Degrees’ energy storage technology was developed with a focus on electrical input, such as wind or solar with the idea to be based close to these renewable generation sources. SA Water approached the company and asked if they could produce technology that would allow a biogas input. 1414 Degrees’ engineers looked at the plans and said in principle it could be done – and it was in less than two years from the idea stage to the first working commercial pilot of any of the company’s machines. The technology was proven in the 1414 Degrees workshop, but it hadn’t been executed on a commercial scale before. Naturally, there were a few challenges along the way.
“Firstly, we didn’t have any guide to go by,” Dr Moriarty says.
“Nobody’s done this before so we couldn’t see who’s been using things in a similar application, but the sorts of burners we used for the biogas are available and they’re used in things like brick kilns.
“Getting the gas burnt wasn’t the big problem, but the problem with the gas is that it has quite a low calorific value – methane content is quite low and that causes problems with their existing engines.
“The advantage of our burners turned out to be that once they’re above the ignition point of the gas you don’t need any other source of ignition. So it’s operating at something like 1100 degrees, 1200 degrees, so when the gas enters the chamber automatically ignites.
“The burner system is quite complicated, it’s called a regenerator burner and these have to switch on and off alternately every few seconds, so getting it all tuned up was thought to be a big problem.
“As it happened, they had them working within a few days, which was remarkable and no one expected that.”
The next challenge for the 1414 Degrees team was integrating the brand-new technology into an existing plant with a need to get it working within a very short space of time.
“Basically SA Water said to us that we needed to have it operating before the next financial year so they could make investment decisions around it. So that really put the pressure on,” Dr Moriarty said.
“Normally this would be a four or five year project in my view where we would have tested everything out. So we’re actually testing things and getting it operational in a working environment, which normally you might have tested them out in a workshop.”
The fact the wastewater treatment plant is located in a developed neighbourhood added extra pressure, and the 1414 Degrees team had to be very careful of noise. They were also working directly under a flight path of a nearby airport where aircraft were taking off and landing. Planes would fly as low as 60 metres overhead so in many cases the team had to work in the small hours of the morning with cranes and other machinery when there were no flights scheduled.
“Then we had all the issues of where the pipes were and how to access them in an old, existing plant,” Dr Moriarty says.
“That said, SA Water were very, very helpful. They really partnered with us on it. Then again they are a government owned utility and they have a lot of stringent operating conditions and OH&S.
“For a new machine in an old environment, the engineers did a marvellous job frankly and to have it working within a few weeks of start up is just amazing.
“Even the most optimistic wouldn’t have predicted that happening. Now that it’s sitting there, its generating electricity and we’re waiting for SA Water to get their grid connection so we can export to the national electricity market. So we’re ahead.”
As well as continuing the management of the GAS-TESS system, 1414 Degrees is building another of its electrically charged devices, which will be charged off the grid, most likely with power purchase agreements from a renewable energy aggregator. The TESS will be able to time-shift that energy produced and put it back in the grid at peak times.
“It’s certainly one of the solutions for the future of energy storage,” Dr Moriarty says.
“Certain batteries like lithium batteries have particular characteristics to make them suitable for particular applications.
“What we’re targeting is large-scale because given the scalability of the silicon storage, that’s where we think it should sit.
“Where we want to go is to position our devices near large industries where they have a large heat offtake. Then we would enable those industries to burn less, or even replace all of their gas or coal heat source with renewable energy.
“In other words the more renewable supply that comes on, we can provide large-scale storage, and this storage in principle can work day in day out for years without any degradation.
“We want to compete on a scale with pumped hydro but distributed through the grid, so not relying on having a mountain nearby.”