energy consumption
Direct Current highly promising alternative in horticulture
The use of Direct Current in greenhouse horticulture appears to be a very promising alternative. A pilot in the greenhouse horticulture sector demonstrated a positive business case for the use of Direct Current (DC) for greater durability of components, as well as cost and material savings. DC also supports the idea of climate-neutral greenhouse horticulture, as demonstrated in the Direct Current Roadmap.
The DC Roadmap, presented last Friday, is a report compiled by Berenschot at the order of RVO.nl for the Energy Top Sector and TKI Urban Energy. This DC Roadmap focuses on ‘DC microgrids’ and seven specific areas of application. A microgrid is defined as follows: ‘a system of interconnected sources and users that can operate, either independently or linked, on a higher-level grid and can exchange energy’.
Greenhouse horticulture comprises a DC microgrid
The various DC microgrids are, with respect to the innovation phase, at the beginning of the S curve: there is a great deal of uncertainty and there are numerous, divergent opinions and ideas about the value (social or otherwise) of DC microgrids. The report, however, revealed that DC is highly promising in greenhouse horticulture; only second to the market for public lighting. The reporters visited greenhouses whose entire indoor electrical system is set to DC. In this, a single, centralised AC to DC transformer is used, to which a lighting system with DC light fixtures (SON-T or LED) and in some cases a CHP unit is connected.
Advantages of DC in comparison to AC
The use of DC in greenhouses extends the life of the light fixtures. Using thin film condensers instead of electrolytic condensers allows greenhouse growers to opt for components with a longer useful life. In addition to this, material savings can be achieved because a DC system uses cables that are smaller in diameter, which therefore require less copper. Researchers also reported that DC makes the integration and control of systems easier. It enables light fixtures to be dimmed individually because the DC cabling simultaneously allows for the control of lighting (powerline communication). Lastly, the centralised conversion of AC to DC will ensure that less energy is lost in comparison to local conversion per lamp (2 - 3%) at the start of operations.
Rounding off the pilot phase
The Roadmap predicts that the pilot phase for using DC in greenhouse horticulture will be rounded off soon. Sustained growth is possible due to the increasing demand for sensors and PV systems. The first successful pilot was completed in the Netherlands and demonstrated a positive business case. This pilot is being conducted at the Jaap Vreeken bouvardia nursery. The pilot is currently being continued at a larger scale.
Conducive to LED systems
Newly built or renovated greenhouses can now also be fitted with DC electrical systems. This applies primarily to nurseries with DC-fed SON-T or LED (in the near future) light fixtures. It is anticipated that using DC will also decrease the costs of LED systems. In the future, priority will be attached to the use of PV panels and the integration of smart innovations (such as controllable light fixtures and smart sensors) in greenhouse horticulture. The integration of these technologies can strengthen the benefits of a DC microgrid.
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Contributing to the region’s self-sufficiency in vegetable production
Agro-Invest’s new 20 ha greenhouse, located in the Kaluga region of Russia, has successfully completed its first growing season. This is the first stage in a project which will ultimately comprise a total of 100 hectares of greenhouse on 238 hectares of land. The Kaluga region is a special economic zone, located around 300 km from Moscow. The local government is committed to improving the diversification of the region’s economy with the cultivation of tomatoes, cucumbers and leafy vegetables. This greenhouse complex will make a tangible contribution to the region’s goal of becoming self-sufficient in the production of vegetables in the longer term.
Mr. Evgeniy Gorlach joined Agro-Invest in July 2014 to coordinate the greenhouse construction project in the Kaluga region. At first there was nothing but an empty field. Now, less than 18 months later, the company has completed its first growing season and started the second season of cucumbers and tomatoes in the new greenhouse complex, which was built in record time: just one construction season.
The greenhouse comprises 10 ha for the production of tomatoes (four varieties: one beef tomato variety, one truss tomato variety and two varieties of cherry tomatoes), 8 ha of cucumbers and a 2 ha propagation area for young plants and seedlings, plus a packing area/irrigation room and an energy building.
Specific expertise
Headquartered in Moscow, Agro-Invest operates numerous farms in Russia and its business activities include land, crops, livestock farming, equipment, technology and logistics. In his role as Technical Director, Gorlach was tasked with coordinating the project together with Dutch company Dalsem – a company specialised in the development and realisation of complete high-tech greenhouse projects – and the Russian sub-contractors.
The first point of contact for him and everyone else on the project site was Dalsem’s Maurits Zomer as Project Supervisor. “He virtually moved to Russia to work on the project – I think he spent just three weeks back in the Netherlands during the whole year,” recalls the Technical Director. “Although I’d worked on many similar projects in the past, I had no specific experience in greenhouse construction. We benefited tremendously from the expertise of Zomer and his colleagues in terms of greenhouse building and quality control of sub-contractors.”
Complete solution
In addition to the greenhouse framework, the Dutch high-tech specialist provided Agro-Invest with a complete solution for the greenhouse facility, including all machinery and equipment for the installation of the cold storage and the loading and discharge section. The growing area is fully equipped with a heating/climate control system, high-pressure fogging, roof sprinkler system, substrate irrigation, substrate cultivation, CO2 dosing, overhead (1,000W) and intermediate (250W) lights and screens. The propagation areas are equipped with aluminium rolling benches and ebb and flood irrigation.
Power is generated by four Rolls Royce Gensets of 9,285 MW each, two of which are equipped with selective catalytic reactors for the production of CO2. Additionally there are four hot-water boilers with a capacity of 11.6 MW each. The water management system also includes rainwater collection, reuse of drainage water and purification of well water.
Tight coordination
“One of our biggest challenges on this project was to complete everything on time,” comments Gorlach. “We had a very tight schedule so we worked in parallel with the project institute, which meant we made a start on the construction work for greenhouse as soon as we obtained the drawings from Dalsem. This created quite a stressful situation because we ran into various problems, such as due to the soil and a lake which meant that we had to recalculate the foundations as we went along. Later on in the project, we were particularly under pressure to get the pipework for heating finished and the water circulation system in place so that the pipes wouldn’t freeze when the first snow arrived – which is usually late November – so work started on the boiler room before all the sandwich panels were finished. We wasted no time; for example, the small irrigation room was finished on a Monday, and the tomato seeds were planted in the cubes on Tuesday – the very next day,” he recalls.
“And we even conducted ‘real-life testing’. We were testing the systems when seeds were already on the table.” This tight coordination was the key to fast completion of the project, which took less than eight months for the construction part. “No one else in Russia has ever achieved that so quickly,” states Gorlach. “It’s thanks to such terrific collaboration between all of us, including our sub-contractors, that the preparation and building work ran relatively smoothly and was completed in time for the growing season as planned. I’m also grateful for the tremendous help we received from the people at our sister companies within the holding.”
Multiple language options
The climate management system plays an important role in the control of all processes in the facility. “From an efficiency perspective, it’s important for us that everything can be managed in one, single system,” says the Technical Director. Based on the flexibility, reliability and user-friendliness of the system, the project group made a conscious decision for the iSii climate computer from Hoogendoorn, an international developer and supplier of automated climate management, water management, energy management and data management solutions for horticultural businesses.
“The system controls literally everything in our greenhouse: climate, irrigation, CO2, ventilation windows, screening and energy consumption. Everything is connected to Hoogendoorn, without it, nothing will work.” he adds. All the settings of the new climate computer are flexibly configurable. Furthermore, thanks to the multiple language options, the Dutch crop advisor and the Russian managers can log into the system and adjust the settings in their own respective language.
First-season results
“We received a lot of help with the program settings as well as local training for our employees to help them select the right parameters. The contact was very intensive,” continues Gorlach. The system went live at the end of November 2014 so that the first plants could be irrigated. “Because the system is so comprehensive, the software is very complex so there were a few teething troubles. But we were helped remotely from the Netherlands, and if necessary we received on-site support. In one case, we needed a spare part and a specialist from Dalsem flew in to Moscow and delivered it to our greenhouse on the very same day. You can’t ask for better, quicker and more flexible service than that.”
Despite it being such a whirlwind project, Agro-Invest can look back on the first season with satisfaction. “Apart from the teething troubles, we had no major problems during our first year. A manager from Hoogendoorn recently visited us to answer all our practical questions based on the first-season results and to help us to further optimise the precise settings, so we’re now ready to achieve maximum results in our second season,” he concludes.
Summary
Agro-Invest’s new, high-tech 20 ha greenhouse in the Kaluga region of Russia was constructed in record time thanks to tight project management and excellent collaboration between all members of the project team. The climate management system controls everything in the greenhouse, from irrigation and CO2 to ventilation, screening and energy consumption. Following on from a successful first growing season of tomatoes and cucumbers, the second season is already underway.
Text: Lynn Radford
LEDs for energy savings of 50%
LED lighting allows energy consumption to be reduced in the cultivation of tomatoes with assimilation lighting. Even better: energy consumption can be cut in half. Eight PhD candidates and three post-graduate researchers are conducting research as part of the ‘Led it be 50%’ project to achieve this.
‘Switching from high-pressure sodium (SON-T) lamps to LED lighting will result in energy savings of 25% with regard to the conversion of electricity into light. In a few years that will even be 30%, since LEDs are becoming increasingly effective. A more even distribution of light across foliage by suspending LEDs at the right position dispersed throughout the crop will enhance light absorption by 15%.
‘Another variable is the application of different colours of light, which will enable you to control the intensity of the light throughout the day. This should lead to a photosynthesis intensification of 10%. We also want to investigate the possibility of sending relatively more assimilates to the fruit to enable 5% more fruit to be formed with the same photosynthesis level. A total amount of 60% in electricity can be saved on lighting.’
As LEDs produce little heat, will greenhouses require more heating?
‘Net energy savings of 50% are realistic. I don’t think that growers will need to raise their heating quotas, because my theory is based on the idea of crops being cultivated under higher humidity conditions. The humidity can be higher particularly during the night-time, so that less moisture will evaporate from the plants. Vaporisation costs energy, which is why we are seeking ways to cut back on vaporisation and to achieve cultivation under slightly more humid conditions.
‘A low evaporation rate and high humidity conditions allow you to save on heat. That has to compensate for the lack of heat otherwise produced by SON-T lamps.
‘Cultivation under higher humidity conditions, however, increases plants’ susceptibility to mildew and fungi. We hope to enhance the resistance in plants being grown under LED lighting through such measures as the controlled application of red light during the night.
‘We aim to achieve a production increase of 30% with the same amount of light - or the same production levels with 30% less light. But will professional growers opt for these possibilities?’ Marcelis has to smile. This question is reminding him of the introduction of a tomato variety 35 years ago. This variety could be grown at a lower temperature, but when exposed to normal temperature conditions the crop yielded decidedly more fruit. Growers unanimously preferred the latter option. ‘We examine the relationship between the amount of light used and the plant’s response to this. An entrepreneur will decide for himself where his priorities are.’
Is interlighting the answer to a more efficient use of light?
‘Light needs to be absorbed by a plant in order for it to contribute to its growth. Of all the light that shines on a plant from above, 5 to 7% is refracted. This is what you see when you fly over a greenhouse at night with the lighting on. It is not true that a portion of the light is refracted upwards on its own accord. The lamps direct their beams downwards. Another portion of the light is lost because it hits the ground. This is around 5 to 10%. In conclusion, another small portion of light is lost through transmission. This is the light that shines straight through a leaf.
‘The challenge lies in being able to reduce light loss, and to distribute light as evenly as possible. When placed directly beneath the lamps, a plant may receive an excess of light, and placed lower down, it may receive too little. In this case it’s better to consider not only vertical but also horizontal distribution. Interlighting, however, doesn’t solve this problem entirely, but it can cut back this loss considerably. You lose less light to the open sky and the ground.’
Interlighting doesn’t enable light to be projected at a big distance.
‘There is not a lot of light behind a leaf. There must be a way to improve that. Perhaps distribution could be improved with a different shape of leaf. Or you could reduce the size of the lead and experiment with adding colours to the light. I’m certain that much more can be achieved, but this will require a great deal more research.
‘SON-t lamps do not emit their light in a uniformly distributed manner across the crop; most of the light is absorbed by the topmost leaves. With a diffuse distribution improvements of 5% could be achieved.
‘Seventy per cent of all assimilates are absorbed into the fruit. This means that 30% remain inside the plant, but does the plant need this much? Suppose that you can get 75% to the plant through more efficient light control. This is an interesting aspect to take consideration.
‘Placing a diffuse sheet of glass under an SON-T lamp will take away too much light. And even if you make that light diffuse, the reflection remains and you still have less light at the bottom. The question for the industry is: this is what we can do with the sun, now what can you do with the lamp? There are still numerous possibilities with LEDS by placing lenses in front of the light source.
‘Five years from now growers will probably be using a combination of SON-T on top and interlighting in between the crop. But in the end, they will be using LEDs exclusively. I’m not clairvoyant. Perhaps SON-T lighting will make giant strides forward, but there are more development possibilities for LEDs.’
Do plants derive other substances when exposed to LED lighting in comparison to SON-T light?
‘LED lighting directed at the bunch in tomato plants will double the Vitamin C content. This immediately raises new questions for further research: how does that work? What colour light would you need to achieve this? Research on this is currently in full sway. Perhaps this will show us that we can increase other beneficial substances as well. It is doubtful that professional growers will soon be positioning their lighting directly around every bunch of tomatoes, but we do want to discover the principle behind this. Perhaps this will offer growers new possibilities. Everyone can grow tomatoes under diffuse glazing, but if you can grow tomatoes that have a beneficial effect on health, you can distinguish yourself on the market. Specific types of LED lighting could also increase these substances in other crops, such as herbs.’
Plant growth can be influenced by the colour of LED lighting. Marcelis refers to a test conducted on tomatoes in the Wageningen UR test greenhouses incorporating varicoloured LED lighting. Conventional lighting with red and blue light resulted in plants at chest height, while the plants in the test area that were exposed to far-red lighting grew above Marcelis’ head.
‘The research we are conducting should teach us which light combinations will result in optimum production. We are, for instance, also examining the results of applying far-red lighting for short periods during the night. Of all the spectral colours, red is the most efficient. Our knowledge of plant response to LED lighting is, however, still in its infancy.’
The research is funded by the STW technology foundation, LED lamp manufacturer Philips, three seed producing firms (Rijk Zwaan, Nunhems and Bejo), two automation firms (HortiMax and B-Mex), two plant nurseries (Van der Lugt and Westlandse Plantenkwekerij) and Wageningen UR University and Research Centre.
Leo F.M. Marcelis (Elst Gld, 1963) studied horticulture at Wageningen University, where he obtained his PhD in 1994. He was a professor by special appointment of Crop Production in Low-Energy Greenhouses at Wageningen University until 2013 and team leader at Wageningen UR Greenhouse Horticulture. On 1 December 2013 Prof. Dr Leo Marcelis was appointed Professor of Horticulture and Product Physiology at Wageningen University.
Download the complete interview with prof. dr. ir. Leo Marcelis about diffuse glass, LED-lighting, urban farming, de-leafing and the effects on plants, energy consumption and cultivation strategy (login required).
Source/photo: Tuinbouwteksten.nl/Theo Brakeboer.