Reducing Carbon Footprint at the University of Cambridge

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The Department of Plant Sciences is one of the most energy intensive departments at the University of Cambridge. One of the main reasons for this is that much of our research requires us to grow plants and algae under tightly controlled conditions. Variables such as temperature, humidity, day length and lighting levels must all be optimized and consistent to help guarantee the quality of our research.

Across our growth facilities, lighting in particular uses a huge amount of electricity as thousands of lights blaze away all year round to grow what our researchers need. Our electricity demand costs hundreds of thousands of pounds every year and gives the department a large carbon footprint.

To tackle this, over the last few years the department has been researching what exactly artificial lighting needs to provide to guarantee good growth from whatever plant and algae species need to be cultivated.

By engaging with our industrial partners, extensive trials of different LED types have led to the development of competitive LED alternatives to the standard fluorescent tube technology. Quality of growth is the same yet electricity usage has been slashed and various other benefits have been realized along the way.

Dr. Matthew Davey
Senior Research Associate, Department of Plant Sciences

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So in the Department of Plant Sciences we grow lots of plants, we grow lots of algae. Plants and algae are green because they absorb lots of blue light, they absorb lots of red light and they reflect lots of green light. And in the wavelengths that they do absorb – the blue, the red and so on – the fluorescent tubes we have been using in the past are highly tuned for wavelengths specifically for photosystem 1, photosystem 2 photosynthesis. So the plants actually grow really well under those fluorescent bulb conditions. With the LED lights, we want to be really confident that the plants grow, behave and perform in exactly the same way under the LED lights compared to the fluorescent bulbs.

Our efforts have so far been focussed on two applications for LED lighting. Firstly, we have been investigating how algae grow under LED, and through work with our partner Infors a ‘plug-and-play’ LED refit for incubation shakers has been developed.

Initially, a mule unit was produced by Infors which had high performance LEDs underneath where the algae flasks were placed. Algae grown in this shaker were tested for metrics such as dry mass, chlorophyll concentration and optical density. Results were compared with algae cultures grown in standard incubation shakers. The specifications of the optimum growth conditions for our algae were passed back to Infors, to fine-tune the next prototypes. It was much simpler to fit these LED arrays and the new system offers improved consistency of light level over the tray area. Set-up is also easier as LEDs can be dimmed with an illumination dial.

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The electricity usage demanded by the lights has been more than halved and the new LEDs produce less heat; so even more electricity is saved as the unit chillers don’t have to work as hard. Also, the new lights should last for the rest for the shaker’s lifespan, removing the current cost of periodically replacing the lamps.

The Plant Growth Facility on the Botanic Gardens site in Cambridge is home to the department’s second application of LED lighting. Here climate controlled growth rooms can be tuned to grow a wide variety of plants such as tobacco, Arabidopsis, tomato and wheat. Our first trials used LED types already available for growing crops commercially in greenhouses. The lighting spectrum that these produce is tailored for specific crop plants and researchers found that several species didn’t grow well or at all. The next LED array prototypes were developed more to mimic the light produced by the current standard fluorescent tubes.

Dr. Matthew Davey
Senior Research Associate, Department of Plant Sciences

We’ve been measuring lots of parameters involving photosynthesis like oxygen evolution, CO2 uptake, how well the electrons flow through photosystem 1, photosystem2, things like growth rate, how long it takes to get to flowering, biomass, seed set and so on.

The best performing array, produced by Conviron using Valoya LEDs was developed further and used to completely refit two rooms, each with twelve arrays. Researchers were invited to trial these and their results inform the rollout to the other rooms in the facility.

The new LED arrays use 60% less electricity than the old fluorescent arrays and produce much less waste heat. This means that the fans required to help duct heat from the old lights could be removed, reducing the baseload of the growth rooms. Once the other rooms are running with LEDs, the demand on the building’s chillers will also be noticeably reduced.

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The diligent work of department staff and our industrial partners Infors, Conviron and Valoya has brought high quality LED growth lighting solutions to market. They perform just as well as the current standard fluorescent tubes in growing plants and algae.

The justification for this project, ably supported by the University’s Energy & Carbon Reduction Project, has always been to deliver significant energy savings. Once refits are fully rolled out, annual savings approaching 500 tonnes of carbon dioxide equivalent and £100,000 are expected at the Department of Plant Sciences.

In addition, this project has helped to facilitate the more widespread adoption of LED growth lighting, which will unlock even more significant energy savings in the future.