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Swallowfield Nursery – 90 kW wood chip boiler

Swallowfield Nursery in Eastergate, near Chichester, West Sussex, is owned and run by Mr and Mrs Godsmark with the support of their Manager Greg Allen and a skilled team of staff.

The total nursery area is 1.1 hectares (11,000m2) with 7,282m2 under glass.  The remainder consists of polytunnels, buildings, storage and loading areas.

Swallowfield Nursery grows a varied selection of non-edible plants, including geraniums and climbers.

Mr Godsmark initially approached Forest Heat Energy Ltd. (FHE) in May 2014 to discuss the replacement of a 30 kW oil boiler, which had terminally failed.  This boiler had been used to heat two propagating benches.

Following site visits and in depth discussions, it was decided to increase the size of the replacement and to adopt a wood chip fired biomass boiler of 90 kW.  This would heat the two benches, provide heat to their adjacent residence and supplement the two existing oil fired Powrmatic direct air heaters supplying heat to 2935m2 of glass.

The objective being to reduce heating oil costs and to benefit from the Government’s Renewable Heat Incentive payment scheme over a minimum of 20 years.

FHE provided a specification and quotation to supply and install an ETA Hack 90 wood chip boiler with a 5000 litre accumulator tank to work in a closed loop through two coil/fan blowers to plate heat exchangers for the propagating benches and the residence. The system was to be RHI eligible and included approved meters to record the heat produced.

Mr Godsmark purchased an LS corrugated water tank 15’ diameter by 12’6” high to give a theoretical capacity of 62.5 m3.  After deduction for wasted space under the chip feed mechanism the total usable volume is approximately 56m3, which equates to 14 tonnes of wood chip at a 30% moisture.

With a decision made in late June, the objective was to have the system completed and running before the cut off date for an RHI tariff reduction on the 30th September 2014.

This deadline was achieved and a first meter reading submitted to Ofgem, with the RHI application completed by Laurence Gould, FHE’s preferred RHI consultant.

For optimal performance FHE returned to site to make any necessary tweaks to settings, and a heat loss assessment was submitted at Ofgem’s request.

The generally colder weather during January and February has tested the installation with the biomass system supplemented by occasional heat from the Powrmatics to maintain the 16+ degrees Celsius from as low as -5°C outside temperature.

In Mid February RHI approval was received.  This will enable Swallowfield Nursery to claim quarterly payments, which will contribute to a heating cost reduction for the nursery over a 20-year period and a likely payback of capital in under 6 years (depending on future oil prices).

Prior to the biomass installation, the propagating benches and the residence used approximately 12,600 litres of kerosene oil per annum.

Swallowfield Nursery Facts and Figures:

  • Target temperature in greenhouses: 16 degrees Celsius
  • Heating period: October to May
  • Oil price at the time of FHE quotation: 55p/litre approx.
  • Woodchip price Winter 2014/15: £110 per tonne *blown delivery
  • Oil heat output Calorific value: 10 kW/litre
  • Chip heat output Calorific value: 3.5 kW/kg
  • Estimated tonnage of chip per annum: 42 tonnes
  • Estimated RHI payments over 20 years: £215,220.00
  • Capital cost of the installation: Approx. £70,000.00
  • RHI tariff rate to 30th September 2014: 8.6p/kWh
  • Operational life of the ETA biomass boiler: 25 years

*Wood chip supplied by specialist trailer allowing blown delivery of 32 cubic metres (per load) from Woodmancote Contractors, an associate company of FHE Ltd.

For further information or to understand how your business may benefit from a biomass heating system, please contact: John Penfold, Director, Forest Heat Energy Ltd. Tel: 01243 543036 Email: john@forestheatenergy.co.uk

With thanks to our Partners:

David Blaber, Adept Heating and Mechanical Services Ltd. Technical partners

Claire Kingston, Laurence Gould Partnership, RHI consultant

Roy Campbell, Camco Design, Drawings and Schematic