It took Peter Dearman 30 years to develop his liquid air engine, tucked away in a tiny garage workshop in Hertfordshire, UK. But it only took Toby Peters, the Chief Executive of the Dearman Engine company, a tiny fraction of that time to decide that he wanted in. Not letting his initial excitement get the best of him, Peters took the technology to the University of Leeds to see if the science stacked up. Delighted with the positive results, he and Dearman teamed up and the Dearman Engine Company was born.
the Dearman Engine company
How does the Dearman liquid engine work?
The basic principle is if you take 710 litres of air and liquefy it, you get one litre of liquid air, which you store at atmospheric pressure. You just have to keep it cold, at -196 degrees Celsius, you don’t have to keep it under pressure. By introducing ambient heat, the liquid air boils and turns back into gaseous air: it expands 710 times and you can use that to drive an engine.
Historically, it was treated like a steam engine: you boiled a tank of liquid air and used the head of steam to drive the engine. But Peter came up with this very clever idea which was to keep it as a liquid and inject it into the piston. The void at the top of the cylinder just above the piston is filled with a heat exchanger – water and glycol mixed – into which a small droplet of liquid nitrogen is injected to get very rapid and instantaneous expansion inside the cylinder. That then drives the piston down, which drives the engine. It exhausts the air to atmosphere and recycles the heat exchanging fluid. Peter’s invention was actually what Andy Atkins [Chief Engineer of technology at Ricardo] describes as an ‘internal steam engine’ by using this heat exchange fluid.
The clever bit is that by using heat exchange fluid we can integrate the engine with other engines. So although you can use this as a zero emission powertrain for zero emission vehicles, this is where it becomes really exciting. We can actually integrate it with a diesel engine and harness the waste heat of the coolant loop rather than the exhaust – the coolant loop is at 90-100 degrees Celsius and our tank is -196 degrees Celsius.
We can broadly put this alongside a diesel engine, harnessing the waste which could, on a bus, reduce fuel consumption by about 25-30%; 30% of every litre of diesel is lost out of the radiator, let alone what goes out the exhaust.
We can also use it for cooling. If you think of the massive amounts of refrigerated vehicles on the roads, about 15-20% of the diesel consumption is to drive the cooling unit. We can use the liquid nitrogen as a far more efficient and zero emission way of providing the cooling, thereby reducing the diesel consumption in towns.
Does the engine work better as a liquid air-diesel hybrid, or are you planning to launch 100% liquid air engines?
We’re doing three applications, starting off with the cold and power engine: we’ve got a government grant and are working with MIRA on air products in Loughborough University; we will have a test vehicle operating next year. We can make significant savings on diesel consumption and have zero emission cooling. Equally, modelling shows that it’s quite cheap, so it’s got an economic case as well as an implemental case.
Application number two will be a waste/heat recovery engine alongside a diesel: we’re starting work on that and see it going on to test beds in 2015. So it’s not a case of either/or. We’re looking at all three because we think they are an opportunity. We’re not saying this is a silver bullet, we’re realistic. I’m not saying we’re going to be driving around in passenger vehicles in the next ten years driven by liquid air.
We do think that the zero emission application has some interesting off-road markets – mining vehicles, forklift trucks, those sorts of applications, which are still very big markets. But the waste/heat recovery, if you look at buses, heavy goods vehicles, is very interesting. In Hong Kong, 25% of the diesel consumption on a bus is to drive the air conditioning, so if you can replace that with a zero emission solution where you’re also harnessing renewable energy to replace the diesel, it becomes quite appealing.
Do you have any plans to invest in Hong Kong or similar markets?
Obviously cold refrigeration and power is a globally growing market. Once you go into Africa or Asia, it’s under massive, growing demand both for the transport of food and people. We see Asia as a prime opportunity for this technology.
I’d like to see the UK maintaining the lead. The government is investing very heavily in liquid air technologies: it has funded a new Centre for Cryogenic Energy Storage at Birmingham University so we’ve now got a centre for development. It is also funding a number of research projects and our demonstration project. We don’t want this technology to slip abroad. Whilst we’re absolutely targeting a global marketplace, we want the technology and the manufacturer and the IP very much to remain in the UK.
Would there need to be any infrastructure in place to make it work?
The beauty of it is that the actual broad infrastructure for manufacturing, the supply chain, is already in place. This is a piston engine, so you can build the first engine’s early development and first commercial deployment using existing supply chains.
And, although we talk liquid air, ‘liquid air’ is changeable with liquid nitrogen; air is 78% nitrogen. And liquid nitrogen is readily available from industrial gases. That means that, rather than having to put in infrastructure, to run a first commercial deployment, you can use the excess nitrogen capacity within the marketplace. There is already a distribution network for liquid nitrogen transporters all around Europe, because it’s used in many processes. You’ll find it at hospitals, factories, everywhere.
Would you say that is one of the main benefits of liquid air EVs and hybrids?
Every technology has its own strengths and weaknesses, so I don’t think it’s a case of this is better or worse, it is different technology. But I do think that a really big advantage of this technology is that you don’t have to invest in infrastructure. We don’t have to spend £1 million [US$1.6m] on a different filling system, or whatever it is. Equally, with EVs, if you put too many down then you’ve got to reinforce the grid. We don’t have those problems. I don’t want to start coming out and saying that we see liquid air as replacing EVs or hydrogen. We don’t. We see it having a role within the whole strategy.
Would the engine require any extra safety reinforcements?
Liquid nitrogen is already actually put on vehicles and used in some instances as a cooling solution so its management and safety is already quite well understood. The engine itself is going to be operating at relatively low pressure. It’s not a massively high pressure engine. It’s appropriate in diesels. It’s all within the bounds of known engineering. Clearly, it’s going to be a new engine and it will require certain forms of certification but we’re already starting to think about those.
Are you currently working with any OEMs or suppliers?
We’re working with MIRA and Air Products on engine number one. We’re working with Loughborough University, University of Birmingham, and we are in active engagement with a number of other partners in the project. At the moment, we are building the first commercial demonstrator, to get test data and then really start talking to the OEMs. We’re getting a lot of interest from end users because clearly they are the people who, if you can deliver economic savings and environmental values, environmental impact, are going to benefit.
Rachael Hogg
