How Plant Raisers Ltd Are Taking Propagation ‘Off Grid’

Plant Raisers Ltd, the largest propagator of glasshouse salad crops in the UK, has in addition to a recent expansion of its conventional glasshouse facility, partnered with sister company IGrowing Ltd to develop a system to produce seedlings using an off-grid LED lit vertical farming facility.

Eliminating carbon footprint
The concept has been designed to eliminate the carbon footprint associated with vertical farming and maximize the yield of seedlings per unit of electricity. To achieve this, every aspect of power demand for urban farming systems was analyzed and optimized. A key focus in developing a sustainable and efficient vertical plant production system targeted the excess heat created by the inefficiency of existing systems. Eliminating this waste energy has allowed the parasitic loads associated with heat management to be negated saving energy and unnecessary capital cost and making off-grid operation a reality.

LED fixture and power infrastructure producing negligible heat
The first task for the designers was to produce an LED fixture and power infrastructure which produced negligible heat. Collaboration with Extreme Low Energy, a UK company with knowledge and expertise in DC infrastructures provided the electrical solution and the APP-based control system that delivered crop-specific lighting recipes. Several iterations of light unit design were required before the targeted level of energy efficiency and lighting performance was achieved. The end result is a bespoke fixture that has excellent light uniformity, full spectral and intensity control and emits virtually no waste heat. The control of spectral lighting recipe and duration allows for further energy gains building on Plant Raiser’s horticultural understanding of crop requirements at each stage of growth. Additionally, as the luminaires are only 8 mm thick there is an opportunity to maximize the number of growing levels in any given space maximizing space utilization.

With no surplus heat load from the installation, controlling the environment required a different approach to the conventional HVAC systems. Instead, environmental control is provided by fans and sensors. These are switched by the App-based program which allows for remote control at any time of day or night. The app also has the ability to continuously record data to aid management decisions on the most appropriate climate and lighting settings.

Container system with low energy demand
The total energy demand of the container system is now so low that it can support off-grid production with power provided by locally mounted solar panels and/or a small scale wind turbine with a stand by gas generator available as an optional extra. Battery technology allows storage and control of the power generation. These aspects are also controlled and monitored using the app-based program.

The resulting system is the culmination of over three years' research at Plant Raisers Ltd focussed on containerized growing seedlings with the minimum energy input. The project is now fully operational and will be further developed by iGrowing Ltd for customer-specific applications. The system components can also be fitted into larger vertical farm developments looking to take advantage of the energy savings and design methodology.

For more information:
Nick Denham
iGrowing Ltd
nick@igrowing.co.uk