L.E.D.

by Bob Johnstone

  C H A P T E R S E V E N T E E N

  Strawberry Yields Forever B ack in Victorian times, if you were the owner of a big house and you wanted to show off to your guests, you would serve them fruits out of season, fresh strawberries in Spring for example. To achieve this feat you

  would instruct your head gardener to create beds of hot mulch to warm the soil, orient the beds towards the sun, cover them with glass, then instal a boiler and pipes to supply additional heat. This technique of bringing on plants early was called “forcing.” Sir William Siemens was the owner of a big house, a country seat called Sherwood, near Tunbridge Wells in southeast England. A scion of the pioneering German electrical industry family, Siemens was in his latter years a gentleman inventor. In a series of experiments at Sherwood beginning around 1879 he demonstrated that new-fangled electric lights could be used to enhance the growth of plants. Siemens wrote about “night-time gardening” in a paper he presented to the Royal Society. He predicted that, thanks to electric light, “the horticulturalist will be able to make himself practically independent of solar light for producing a high quality of fruit at all seasons of the year.”

  A hundred years later metal-halide and high-pressure sodiumvapor lights had routinely been pressed into service to provide horticultural lighting as a supplement to sunlight to extend the greenhouse growing season, particularly during winter in northern hemisphere countries. Though efficacious, this was far from optimal. To transform light via photosynthesis into the nutrients they need in order to grow and flourish, plants thrive on a broad spectrum of wavelengths ranging from almost ultraviolet to near infrared, that is, 400~700 nanometers. But the coverage that conventional lighting technologies can manage is much narrower, just 560~630 nanometers. Legacy lights also generate copious amounts of heat, wasting energy and ruling out their use in confined areas, like spacecraft for example.

  So long as LEDs were only capable of emitting red light, the idea of employing them to promote plant growth seemed far-fetched to most scientists. But Ray Bula, director of the Wisconsin Center for Space Automation and Robotics (WCSAR) at the University of WisconsinMadison, thought otherwise. He was convinced that monochromatic LEDs

  - in particular ones which could produce what would later be known as “horticultural red,” that is, with a wavelength of 660 nanometers, deeper than the red used for traffic and brake lights - would suffice to power what he called “a bio-factory in space.” In 1996, after several failed attempts, WCSAR finally succeeded in persuading leaf cuttings from a potato to sprout tubers under red LED lights while onboard one of NASA’s Space Shuttles. “The potential is definitely there to create new products and get new values in agriculture,” a delighted Bula told a reporter. But it would take more than a decade before LEDs became powerful and versatile enough to realize that potential.

  Though not himself a biologist - his training was in law and finance - Lars Aikala had always loved plants. He found it impossible to throw them away. He still owned a cactus that had been given to him as a six-year-old. On special occasions like birthdays he would present his wife with living plants. “She may not like them,” he conceded, “but I don’t like cut flowers, because they’re dead.” In his native Finland Aikala had worked for years with clean technology startups. “It was always difficult to sell something on purely green values,” he had learned the hard way. “But when green values aligned with cost savings or increased revenue, the whole story changed.” One day he found himself in a greenhouse. “The grower was complaining to me that he spends tens of thousands of euros per day in electricity costs for illumination.” That gave Aikala pause for thought: “3.6 million euros per year in a relatively small greenhouse? — there must be room for improvement!” But when he suggested LEDs, the grower was dismissive. “They don’t work,” he told Aikala flatly. His negative response piqued Aikala’s curiosity. “Well, why don’t they work?” he wondered. “What needs to happen to make them work?” He consulted some researchers he knew. They told him the same thing. But Aikala was like a dog worrying a bone: he simply would not let the topic go. “I couldn’t accept the fact that you can’t [use LEDs to] grow plants,” he told me, adding, “I needed to get this working.”

  For guidance Aikala turned to some friends who were specialists in materials technology. From them he learned that LEDs could be made to emit light of any color. The question was, Which colors were best-suited for growing plants? Initially, they assumed that everything about how light affects plants would have long since been figured out. All they would have to do was to look up the answers in a book. That turned out not to be the case. Since neither he nor his friends were professional plant growers or horticultural biologists, the obvious first step was to link up with a local Finnish crop research institute. Here geography was in their favor. Finland is a very dark country. In far northern Europe - Helsinki lies at about the same latitude as Anchorage, Alaska - crops can only be grown outdoors for three months of the year. But Finns love their lettuce and cucumber, which they use to make kurkkusalatti, a sweet-and-sour salad whose dressing invariably includes dill, “the garlic of the north.” To ensure that the supply of fresh vegetables and herbs is maintained throughout the long winter months, Finns have spent decades honing the art of growing plants under artificial light. With the result that today, Finnish horticulturalists boast that their greenhouses produce the world’s highest crop yields per square meter. The downside is that, to achieve these outcomes, they have to use copious amounts of electricity, meaning that food in Finland is very expensive.

  Aikala and his friends built some prototype lights then approached the leading local experts on indoor horticulture. This initial encounter did not go well. “Basically, they told us we should take our toys away from their greenhouse,” Aikala recalled. LEDs would obviously not work because they did not produce radiant heat on the leaves, so plants would not transpire (which they need to do to access nutrients). It took a lot of convincing to get the researchers to accept funding to run the first trial. It was not a success. But Aikala and his colleagues quickly tweaked the spectrum that their lights output. The second trial produced promising results. At that point they decided to back their vision with their own money. In 2009 Aikala formed a startup which he named Valoya, Finnish for “lights.”

  The company’s initial goal was simply to slash the amount of energy needed to grow plants in greenhouses. But during the course of doing trials, the researchers noticed that varying the spectrum always changed the outcome. Soon it became clear that plants not only used light for photosynthesis, light was also a kind of information system that told the plants how to grow. Biologists call this process “photomorphogenesis.” Aikala came up with his own explanation for what was happening. “First, the plant needs energy; second, it needs to decide what to do with that energy. Does it expend energy on making a root, a flower, a seed, or on stretching itself? For example, when the plant is overshadowed by another plant, it doesn’t feel the absence of light, it feels the over-representation of dark red. That could be a problem, so the plant will stretch in competition with its neighbor to get its leaves on top of the other plant.” Horticulturalists might object that this was an oversimplification, but Aikala argued that it was all about survival. “What happens at the end of the summer is you have a lot of these dark-red colors and you have a change in night-length, which is also related to light. When autumn comes, what does the plant need to do before it is killed by the frost? It needs to make a seed, and to do this it has first to flower.”

  Over the years, by observing how different plants reacted to different spectrums of light, Valoya gradually accumulated a trove of proprietary knowledge about how to manipulate plants. “We’re selling a light that not only grows your plants well, it also helps the grower quicken the flowering or strengthen the root, whatever is important for him,” Aikala said. In the seven years since its founding, Valoya had run around three hundred trials, with fifty more underway, on more than a hundred and fift
y different types of plant. “Now we know how many plants react to certain lights, and we know which customers value these reactions — this really is the core of our company. And of course many times there’s also energy savings involved, but for us and our customers who are in the business of growing plants, saving energy is not the most important factor. We focus on cases where we can push the yields of the plants. So: highvalue crops, increasing yields, and solving light issues.”

  For Aikala, the plant trials were endlessly fascinating. On the one hand, they provided an ongoing source of competitive advantage for his little company battling against much bigger rivals. “It’s like a FinlandSweden ice hockey game,” he said, “it’s who wins.” On the other, it was fun finding out new things. “We realized after we started the company that there is so much that is still unknown about plants — we have seen stuff in our trials that no-one else has ever seen before.” One such phenomenon, which went against conventional wisdom, was that bumble bees, which are essential for pollinating plants, become active when LEDs are switched on, even when there is no natural light to provide the ultraviolet that bees are supposed to need. “It’s not something that we’ve been able to monetize,” Aikala laughed, “it’s just one of those really nice things, that we can figure out something that some scientist later has to explain.”

  Valoya addressed three main markets. The biggest was supplementary lighting to support sunlight in greenhouses. Here tomatoes, cucumbers, and leafy salad greens were the main crops. But flowers, like roses and orchids, and ornamentals, like begonias and chrysanthemums, were also a significant market. In Holland, seventy percent of greenhouse illumination is used for ornamentals versus just thirty percent for vegetables. This included a great deal of what the industry calls “cyclic” lighting, small bursts of light administered during night-time that are either used to trigger or inhibit flowering. The second market was crop science undertaken by universities, seed companies, and crop protection firms. In the growth rooms at such centers researchers typically try to simulate outdoor light levels, so the density of light is extremely high. A small room at a crop science company might use as many fixtures as a large commercial greenhouse. Valoya claimed that seven out of the world’s top ten seed companies use its lights to breed their plants.

  The third market was vertical farms. These employ multi-storey stacks in cleanroom environments to produce high-value, short-shelf-life crops like specialty lettuce, baby salad greens, and fresh herbs. Vertical farms are typically located in or just outside cities, close to the end-market, radically reducing transport time and cost. They are particularly attractive in advanced Asian countries like Japan, Taiwan, and Singapore, where arable land is scarce or degraded and the labor force ageing. Unaffected by the vagaries of weather, vertical farms are like plant factories, where every variable can be controlled. Since there is no natural light in such facilities, artificial illumination is essential. LEDs are ideal for vertical farms because, in addition to using far less energy, they do not generate radiant heat, meaning that plant trays can be closely stacked together without fear of scorching the leaves. But the expense of equipping such facilities is still prohibitive for application to mass markets.

  An entrepreneur needs to be in the right place at the right time. For Steve Edwards the place was Rothamsted Research, the time 2010. Located in Harpenden just north of London, Rothamsted was founded in 1843, making it the world’s oldest continuously running agricultural research station. The center grows plants year round. Edwards was installing LED fixtures as replacements for fluorescent troffers in the conference suite at Rothamsted. On his way to meetings with the facilities manager, he would walk past rows of orange-glowing greenhouses whose high-pressure sodium lighting was wasting lots of energy and generating “oodles of carbon,” as he put it. “So I asked the inevitable question,” Edwards recalled: “What can I do to help?” The manager introduced him to Julian Franklin, head of horticulture and controlled environments at Rothamsted, who was in charge of growing plants in the greenhouses. Over a cup of tea the pair discussed the potential for substituting LED lights for sodium. Attempting to replicate a summer environment all year round takes heaps of electricity. Anything which could reduce that cost would be of interest. Franklin had looked at LEDs before and found them wanting. Intended for the household market as replacements for 40- and 60-watt bulbs, LEDs had been too low-power for application to greenhouses, where a single room might gobble up as much as 80 kilowatts of lighting. The discussion ended with Franklin posing Edwards a challenge. If he could provide a broad-spectrum light that could stimulate a comparable plant response to a 400-watt sodium lamp then Rothamsted would be seriously interested in switching to LED. “So that’s exactly what I did,” Edwards said.

  Steve Edwards describes himself as “one of those people who is just fascinated by technology, and how it can be used to improve people’s lives.” Like his friend Lars Aikala, he had the desire to make a difference. Edwards trained as an engineer in the defense industry, working for British Aerospace. He enjoyed his job, but when the company announced plans to move his division to the north of England, he quit. He went into the clean technology sector, becoming technical director for a firm that made LED fixtures.

  Edwards rose to the challenge that Franklin had set him. Working in his garage at home in his own time he built prototype lights that he would run up to Rothamsted for Franklin to trial on growing plants. Based on feedback from Franklin Edwards would modify the lights, a cycle that continued through several iterations. In retrospect Edwards realized that he had been fortunate to have hooked up with a research institute populated by scientists who were naturally curious to try new things. “After about eighteen months it got to the point where the lights were really beginning to make a difference,” Edwards said. “Julian looked at me and said, Steve, I think you’ve got a commercial product here — there’s a market for what you’ve got.” And so it proved. In 2011 Edwards found some backers and formed a startup named PhytoLux. Rothamsted would subsequently announce plans to replace the majority of the 2,000 highpressure sodium lamps in its greenhouses with PhytoLux’s LED lamps. Meantime, as one of the most influential horticulturalists in the UK, Franklin turned out to be invaluable in getting PhytoLux off the ground. He provided introductions to key organizations, like UK universities and research institutions. PhytoLux gave them free lights, encouraging researchers to grow whatever they wanted in return for information about their findings. Soon word was getting out to commercial growers who, spooked by the hype surrounding solid-state lighting, had thus far been nervous about adopting the new technology.

  Growers are understandably conservative — their livelihood depends on being able to produce crops reliably. Before making any changes in their growing methods they have to be convinced that those changes will work. But there was one crop where growers were more willing to take a chance. Supermarkets will pay a premium for out-ofseason strawberries. They know that a small but significant number of their customers are willing to fork out extra for fresh, locally-grown produce. But obtaining high-quality, good-tasting strawberries in the UK in winter is nigh-on impossible. Wholesalers have to rely on imports from Israel or Egypt. These berries tend to be slightly larger than normal and not quite ripe, partly white on the outside and hard on the inside. Because of the need to ship long distances, the fruit is picked while still not ready to eat. By the time the strawberries hit the shelves they have inevitably lost some of their freshness. Back in 1880 William Siemens had demonstrated that it was possible to persuade strawberries to set fruit early. “We have been able to bring strawberries to ripeness by means of electric light fully a fortnight before the usual time,” he wrote, “such fruit being remarkable for its colour and aromatic flavour.”

  Wallings Nursery, a fruit grower based in Essex, near London, wanted to extend the strawberry season for its biggest customer, Sainsbury’s, a leading UK supermarket chain. In 2013 Wallings hooked up with PhytoLux to see whether LEDs
could be used to simulate spring lighting conditions under glass. Strawberries are highly light-dependent. They are also a fickle fruit: you have to time their exposure to light perfectly. Initial experiments showed that by adding a small burst of cyclic light it was possible to increase yields and produce fruit a few weeks later than normal, when prices were higher. Encouraged by this initial result, Wallings went on to plant a second crop in November. Using LED lights the nursery was able to start the plants yielding flavorful fruit in December, just in time for the Christmas market. This was a win-win-win. Wallings doubled their yield, Sainsbury’s was delighted - “it was inconceivable even five years ago that we could supply British strawberries all year round,” a spokesperson for the chain said - and PhytoLux sold the grower more of its lights. A less obvious advantage of planting a winter crop was staffing. The ability to keep their greenhouses running all year means that growers do not have to lay off staff when the season ends, they can hire them on a permanent basis. That in turn means there is no need to continually retrain workers, skills improve as a result, and the business benefits overall. The key issue here, as elsewhere, was cost. By providing energy savings of fifty-plus percent, PhytoLux was able to offer its customers a payback of less than two years. But though equipment costs were coming down, for many growers the initial purchase price was still too high. Especially since it took almost one and a half LED fixtures to replace a high-pressure sodium equivalent.

  Julian Franklin saw in LED lighting the potential to bring about a fundamental change in horticulture. It would allow plants to be grown in a much more mechanized way, indoors, in combination with robot picking systems. “At the moment it’s only cost-effective for leaf-crops and herbs,” he told me. “But as LED prices drop and their energy efficiency increases, then we can start seriously looking at some of the agricultural crops, like growing wheat in a factory situation. We’ve still got quite a way to go, but that will be like the holy grail. If we could get to that, then our landscape starts changing.”