Overseas Weekly Selection | What kind of refrigerator? Liquid air engine is the future

Produced by: Sina Technology

Compiled by: Muir

As early as 2001, a middle-aged man took a video of his car and shared it with several friends around him. The main character in the video is a dilapidated Vauxhall Nova car, which is in the midst of smog and circling in the messy yard. The man sitting behind the steering wheel is Peter Dearman, a slovenly middle-aged man who is eager to learn and do it himself. Over the past 40 years, he has spent most of his time imagining a steam engine that can embody the ultimate of engineering: an engine driven only by air.

Dillman was born in 1951 on an egg farm in north London. Combined with his background, he seems not the right person to solve this problem. He dropped out of school at the age of 15, worked on his own farm for a while, and then went to work in a local sheet metal factory. At night, like most British people, they repair in the garage or backyard. However, Dillman's talent and ambition make him stand out from amateurs. Over the years, he has applied for various patents, such as improved adjustable wrench, solar water heating system and portable resuscitator still used in ambulances. However, his most outstanding achievement is the Nova. The engine of this car was assembled by Dillman himself with wires, old beer cans, red plastic garbage cans and liquid nitrogen that can fill as many coffee cans.

　　 From engine to refrigerator

Dillman's project inspiration dates back to at least 1899. At that time, a Danish inventor named Hans Knudsen claimed that he had designed a car that could use "clean blue" fuel, that is, liquid air, which sold for only one cent per gallon as power. This kind of car will not emit pollutants and greenhouse gases, leaving only harmless condensation traces and driving at a leisurely speed of 12 miles per hour. Knudsen was highly praised by the media at that time, but his company declared bankruptcy in just a few years. The cynics believe that Knudsen directed and acted in a Theranos style hoax, partly because no one knows how his designed car works. For years, an effective liquid air engine seemed as absurd as a perpetual motion machine.

Even so, the underlying principle behind the liquid air engine is not ridiculous. Most engines rely on thermal differential for operation. Take a gasoline engine car as an example. After the fuel and air are mixed, they enter the piston chamber. After ignition, the temperature can reach 1000 ℃ instantly. The gas expands rapidly, pushing the piston and turning the wheel. In the same process, reduce the temperature of Celsius and change it to Fahrenheit, which is called liquid air engine. The boiling point of nitrogen fuel is minus 320 degrees Fahrenheit. When liquid nitrogen enters the (higher temperature) piston chamber, it will instantly evaporate into gas. The temperature change of nitrogen fuel is less than that of gasoline fuel, so the piston's power sense is not so strong, but it is enough to rotate the wheel. The real problem lies in the rear: the low-temperature fuel flowing through the engine will quickly freeze the engine, thus making the heat difference disappear cleanly. Then the air stopped expanding and the car lost power.

Dillman said the obstacles were obvious. He has been thinking about how to solve this problem since he was a teenager. For internal combustion engines, you need a radiator to cool the engine. However, if it is a "cold gas engine", you need a heater to heat up the engine. "I have an implicit solution in my mind, but I know that nothing can be done without some practical research," he said.

The breakthrough took place in 1999. Dillman watched an episode of the BBC series "Tomorrow's World" which has stopped broadcasting. In the program, the host came to Washington University to introduce a very clumsy modified mail car. This mail car has some difficulty going up the mountain. The maximum speed is only 22 miles per hour. Its fuel is liquid nitrogen. However, the "fuel consumption" is a little high, and it consumes 5 gallons of liquid nitrogen per mile. The person who came up with this idea is Abe Hertzberg, an eccentric professor in Guri who has previously proposed the concept of laser powered aircraft. A major innovation has been applied to this mail car: the extremely cold fuel passes through a heat exchanger before being sent to the engine. This heat exchanger is actually a series of concentric tubes that circulate outside air around the fuel tubes. Graduate student John in the project· Williams (John Williams) explained that the heat exchanger can ensure that "the whole device will not become a big ice ball". However, the core problem has not been solved - liquid nitrogen will still rapidly cool the engine, thus preventing liquid nitrogen from evaporating into gas. "Our project is just a proof of concept," Williams said. "Recognize this possibility."

In Bishop Stofford, Dillman sat on his sofa and watched this episode, feeling suddenly enlightened. Herzberg's design logic and improvement methods are on paper. How can we ensure the continuous expansion of liquid nitrogen? Antifreeze, of course. "The truth is simple, but it's only simple when you really understand it," Dillman said. He went into the garage, grabbed a blue plastic pot from the shelf, and then began tossing his lawn mower. First, he tamped the engine on it, and every time he started, he injected antifreeze and water into the piston chamber. This sends room temperature heat directly to the critical place - and then greatly improves the efficiency of the engine. This idea is adopted by Nova.

Dillman has an older brother who works as a contractor. He also paid for patent applications. If he hadn't mentioned it to big customers, the story might have ended here. In 2004, the big customer introduced Dillman to Toby Peters. Peters used to be a war photographer, but later he changed his career and became a business strategy consultant, specializing in corporate social responsibility planning. Peters was suspicious at first. So he took Dillman's engine to the University of Leeds for comprehensive research. Science is the most powerful lobbyist. After research, they found that the efficiency of Dillman engine is comparable to that of gasoline and diesel engines; The fuel utilization rate is close to one third, and the rest can only be wasted. In addition, no amount of antifreeze can solve a fundamental problem: the same gallon of liquid air contains far less energy than fossil fuels. In other words, liquid air fuel can not provide the high horsepower and torque expected by car owners in any case.

Then, in 2011, Peters also suddenly realized that the unique selling point of the Dillman engine obviously does not lie in its use as a "car engine". The traditional engine emits heat, while Dillman's engine emits cold air. Peters later said that air conditioning is the "real value". In other words, the newly established Dillman Company is trying to sell mobile cooling devices instead of engines. As a result, there are many potential customers, such as those in the refrigerator car industry.

The advertising words are ready-made: the diesel engine cooling device not only emits greenhouse gases, but also pollutes the air; Instead of using a device that is harmful to the environment, customers can choose a Dillman cooling device that only discharges nitrogen. Moreover, at the same cost, compared with the traditional system, the Dillman cooling device operates more quietly, replenishes fuel faster and has higher cooling efficiency. It is true that generating liquid nitrogen will consume energy. Even if this factor is taken into account, the Dielman engine also has 40% less emissions than the diesel engine. If the power grid supplying the fuel plant also uses renewable energy, the emissions of Dillman engine can be reduced by 95%.

The logic seems perfect, but is it really persuasive enough? Historically, there are many examples of new technologies without a market. They are either at the wrong time, failed to promote, or submerged in a large number of competitive products launched by companies with strong financial resources. The capitalist economy believes in the law of natural selection, that is, the survival of the fittest. However, in the actual process, what survives may not be the best. For example, when household refrigerators were just emerging, there were two designs on the market: one used electricity, and the other used natural gas. However, even if the natural gas refrigerator runs more quietly and costs less, as you know, the refrigerator will still be handed down. Because big companies have huge advertising budgets to promote refrigerators, and consumers listen to them. If Dillman and Peters are determined to transform the cold chain system of the global low-temperature food transportation system, it is not enough to have an excellent idea.

The process from garage prototype to commercial equipment is also very long. Peters is responsible for financing and business development; Dillman, together with his son and the developing engineering team, further improved his original design in terms of efficiency, compactness, portability and reliability. In 2015, a truck equipped with Dillman refrigeration device drove for several miles in Warwickshire for testing to ensure that the device that works normally in the laboratory environment can also work normally on muddy and slippery rainy roads in the real environment.

A year later, Senbaoli, the second Dalian Lock Supermarket in the UK, rented a Dillman device for three months, and delivered the goods from the storage center in Essex to various supermarkets in London. Another year later, a Dillman refrigerator truck was Unilever Delivered food from Bangeli in the Netherlands without losing any goods.

At present, there are 3 million refrigerated vehicles in the world. It is expected that this number will increase to 17 million by 2025. Peter Dillman's invention seems to be a perfect replacement for the diesel engine. Soon, the Royal Society, Britain's most authoritative scientific institution, also sent an invitation to Dillman for dinner.

　　 Cold storage: a great breakthrough in food preservation

It may be difficult for modern foodies to imagine the extent and speed of mechanical refrigeration changing human diet and global climate. This technology has just entered commercial application after the Civil War; The early technology adopter was a German brewer in the Midwest of the United States, who hoped to keep the beer cool in the hot summer. Gradually, other industries have also realized that refrigeration technology can be used to solve a problem that has plagued mankind for a long time: food deterioration.

For thousands of years, the struggle between human beings and microorganisms has never stopped. Bacteria and fungi try to invade our food, while Renlai tries to stop their invasion with various preservation technologies. In this diffuse Long and During the slow struggle, after repeated attempts and failures, different regions found different anti-corrosion methods. Some even create other delicacies, such as stinky cheese, smoked salmon, salami, miso, jam and quince jam, etc. Even the gelatinous food such as Scandinavian alkaline fish or Chinese preserved eggs is also popular.

Most of these pickled foods have a very long shelf life and are easy to carry. However, they are very different from what they looked like when they were fresh: the chemical and physical changes needed to conquer microorganisms will inevitably change the original flavor, taste and appearance of food. However, the emergence of on-demand refrigeration has changed all this and overturned thousands of years of dietary history.

The earliest mobile mechanical cooling device was patented by Frederick McKinley Jones in 1939. Jones is also the first African American to receive the National Medal of Technology. Like Dillman, Jones dropped out of high school and became a self-taught person. Before he invented the cooling device, perishable food (such as meat, dairy products and agricultural products) had to be buried under the artificially stacked thick ice before it could be transported. At the beginning of the 20th century, a train full of California cantaloupes to be shipped to New York City needed 10500 pounds of ice, and then fresh ice was added along the way, about 7500 pounds each time. Even so, many cantaloupes were damaged after arrival. In fact, the opportunity that prompted Jones' invention was that one of his boss's golf friends lost a whole vehicle of raw chicken. When the transport truck broke down on the way, and all the ice used for fresh-keeping melted away, the chicken was also lost.

During World War II, the Ministry of Defense quickly used Jones's diesel device, "Thermo King", to provide troops with various items from plasma to iced cola. In the years that followed, refrigerated trucks quickly changed the diet of the United States. National distribution network replaces regional distribution network. Slaughterhouses and processing plants are becoming larger and larger, and the site selection is becoming more and more biased. The price of meat has also declined accordingly, becoming a daily necessity. Agriculture is concentrated in the area with the highest crop planting efficiency, so now half of the fruits and vegetables in the United States are produced in California.

In fact, in the United States today, three-quarters of the food on the table is processed, packaged, transported, stored and sold through refrigeration. This is why orange juice stored in a large juice store has a taste of soda water all year round; Why is the genetic improvement of tomato aimed at maximizing cold resistance rather than improving flavor, so that the tomato does not taste like a tomato. Cold storage makes us strong; Change the composition of our intestinal microbes; Redefining our kitchens, ports and cities; It has also reconfigured the global economy and politics. In 2012, six years before the Royal Society commended Dillman and the engine he invented, the outstanding members of the Society said that refrigeration was the most important invention in the history of food and drink - more important than knives, ovens, plows, and even the selective breeding of livestock, fruits, vegetables, etc. for thousands of years.

However, while the expansion of the cold chain system has brought permanent artificial winters to the world, it has also caused serious damage to the natural cryosphere, glaciers, icebergs and permafrost that maintain the Earth's climate system. Refrigeration has accounted for one sixth of human power consumption. In addition, as India and other countries are busy building their own American systems, the demand for refrigeration will continue to increase in the future. According to analysts' prediction, the global refrigeration market will quadruple in the next seven years.

Traditional refrigeration means that the more refrigeration, the more heat released. In addition to the uncontrollable power consumption, refrigerant leakage is also a problem. Once released into the air, these chemicals will lead to climate change. The latest household refrigerators lose less than 1% of refrigerant annually, while the leakage of refrigerant from commercial refrigerators is up to 35%. Different systems use different refrigerants, and some refrigerants (such as ammonia) have negligible impact on the climate. However, other refrigerants, such as hydrofluorocarbons, are regarded as "super" greenhouse gases because of their warming effect more than carbon dioxide.

Although HFCs have been phased out according to the global agreement signed in 2016, their use is still growing in developing countries. Therefore, a project "Project Drawdown" launched by environmentalist Paul Hawken aimed at mitigating climate change listed refrigerant management as the only and most effective global warming solution.

What if we don't do anything? If nothing is done, then suddenly, the slogan of the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAR) is no longer a commitment, but more like a threat: "Use today's actions to change the environment of tomorrow." Continue to use existing technology to save food for 9 billion people on the earth, and eventually this commitment will be fulfilled in the most disastrous way. However, since Jones applied for a patent for "Thermo King" 81 years ago, there have been few significant innovations in the cold chain field - until the emergence of Peter Dillman.

　　 Dillman refrigerator, a new hope for the future?

Last year, for a while, liquid air engines still seemed doomed. Although Dillman's device runs well, the company has run out of investment funds and is almost unable to pay the cost. By the beginning of December, the company had entered into bankruptcy and takeover procedures. Fortunately, the company did not go bankrupt: in January this year, Thomas Keller, an angel investor in Denver, suddenly appeared to bail out the company.

Keller said that the company's problems are very common for technology start-ups. "Dillman has so many opportunities - their technology can be used in many ways - that the company moves in so many different directions that it wastes resources," Keller said. Now, his plan is to streamline. He intends to focus on completing the next generation of engines. "Unilever trucks may use this engine this year," he said

However, when it comes to future challenges, Keller is not sure. On the one hand, the company needs to expand its manufacturing business, which is already a major difficulty. On the other hand, the company also needs to hire sales personnel, establish a maintenance team, and develop the supply chain for parts. To accomplish these things, companies can either get enough huge financing to build infrastructure from scratch, or cooperate with competitors - for example, traditional refrigerated logistics companies - to leverage their existing networks. "To be honest, we are under pressure," Keller admitted.

Toby Peters, who currently works at Birmingham University, is still optimistic about Dillman Company and believes that the company can overcome the recent financial obstacles. But he also pointed out that even if all the 3 million refrigerated transport trucks in the world were equipped with Dillman's engines, it would not be enough to save the world from the disastrous climate impact of refrigeration. "In the next three decades, even if we can deploy 13 to 18 refrigeration equipment per second, we still cannot meet the cooling needs of everyone," Peters said. In addition, he added: "We can't green so much electricity consumption." For example, in 2017 and 2018, the total energy demand for newly installed indoor air-conditioning equipment in developing countries exceeded the global total solar power generation.

Fortunately, the solution to the problem of fossil fuel refrigerators is not limited to making better refrigerators. We have other ways to preserve food, some new, some old. In Santa Barbara, California, a company called Apeel has designed a high-tech edible coating that can slow down the metabolism of fruits and vegetables, thus slowing down their decay rate. This edible coating is made of waxy substances extracted from avocado nuts, which can extend the shelf life of food like a refrigerator, while retaining more nutrition and flavor. Pasteurized milk is also one of the most wasted foods in the United States. Recently, in Australia, engineers recently proposed a new method to replace the pasteurization of milk. By using high-pressure treatment (about 75000 pounds of pressure is applied per square foot, which is to pile six elephants on a dime), they can extend the freshness of milk three times while maintaining its original flavor. Inspired by the traditional root cellar, Dutch designer Floris Schoondebeek recently designed a "ground refrigerator", a natural cooling chamber that can be buried under the ground in his backyard, with a capacity 20 times that of ordinary refrigerators. In Hokkaido, the northernmost part of Japan, agricultural product warehouses use winter snow to maintain low temperatures. Chefs in Tokyo said that the rice, asparagus and beef produced in this area taste more delicious than those refrigerated in the refrigerator.

All these solutions are improvements to mechanical refrigeration, not only in terms of climate impact, but also in terms of food quality and safety. However, none of these methods is universal. This means that the coating can keep blueberries fresh and juicy at room temperature for one month, and cannot be used to keep milk fresh; The wonderful idea of using snow to refrigerate meat products is feasible in Hokkaido, but Santa Barbara cannot; Urban residents also have no backyard to bury large refrigerators. However, the traditional cooling method has almost no use hindrance. But the feasibility of these alternative methods depends on the situation.

And this kind of "depending on the situation" is obviously not the answer we want. Compared with the solutions that can only be applied locally or depending on the situation, the solutions that should be comprehensive are really reassuring. In a sense, the only reason why mechanical refrigeration has become a problem is that it is the best answer to solve food deterioration. Once we have the mechanical refrigeration solution, all problems will be solved. This dominant trend - you can also call it technical barriers, confirmation bias or convenience - is understandable, but it is also worth fighting against. Given that this single solution thinking will put us in a dilemma, for future solutions, we must avoid repeating the same mistakes.

Unless Peter Dillman can build a Nova car that can travel through time and space, it may be too late to change the cooling habits of the whole world at this moment. But perhaps our blueberries, eggs, milk and carrots can - at least during the journey from the countryside to the dining table - no longer rely on refrigerators. At the same time, we should make efforts to ensure that there are more options for food conservation in regions that are not yet subject to the cold chain. We cannot - and should not - completely abandon traditional refrigeration, but traditional refrigeration will not be the only weapon we use to prevent food deterioration.