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Boilers at Gelston Lodge Estate

Gelston Castle Cottages wood fuel case study

  • Location: Castle Douglas, Dumfries & Galloway
  • Wood fuel usage: heating system for four holiday cottages, two residential properties and one office
  • Installation date: May 2007

Reasons for changing to woodfuel

The need to replace old, often problematic boilers at each property at a time when the estate was developing its own wood fuel harvesting operation, meant that woodfuel was the obvious solution when it came to choosing a new heating system.

There are clear financial benefits in terms of greatly reduced and stable fuel costs. In addition, the improved woodland management should raise the quality and future productivity of the woodlands, offering further business opportunities.

System features and benefits

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Gelston uses a wood fuel district heating scheme where heat is distributed via an underground pipe network from a single centralised boiler to each of the properties. As hot water travels round the network, it is drawn off to heat each property. District heating schemes have a number of advantages:

  • Cost effective: a single boiler, boiler house and fuel store can supply many properties
  • Highly energy efficient due to heat recovery system
  • Delivered heat to each user is measurable and accurate, and allows individual billing

The new system is much more efficient and reliable than the previous old boilers. It is loaded and fired on a daily basis.

After two years of continuous operation the owners are very happy with the development of their own fuel supply chain. The efficiency, both financial and environmental, continues to improve as prices on world energy markets increase.

Wood fuel supply

The estate's own hardwood logs are being processed, stored and delivered from estate woodland resources less than a mile away.

Installation issues

The wood fuel heating system was retro-fitted into seven old stone buildings and required a complete redesign of the previous system, including replacement of four oil boilers.

The other properties were previously heated by electric storage heaters and required new wet heat distribution networks to be installed.

The boiler was installed in the former coach house which has listed building status, so a sympathetic and patient design process was required, especially for the flue.

Lessons learned

  • If using your own resources, you need to plan your fuel supply one year ahead
  • Get training from your installer so that you clearly understand the controls of your system
  • Adjust the user definable parameters to suit the site conditions.

Facts and figures

Note: figures are approximate

Building
Heated area 840 m2
Heated volume 2,000 m3
Fabric Stone
Heating system
Boiler manufacturer Fröling
Maximum boiler output 70 kW
Fuel type Logs
Fuel specification
  • Moisture content: <30% (M30)
  • Log size: 500 mm split lengths
Back-up/top-up system Oil boiler (100 kW)
Fuel consumption, costs and savings
Weekly woodfuel use 2-3 tonnes
Annual CO2 savings 58 tonnes
Wood fuel cost Approx £4,000 (estimated cost of staff to process woodfuel)
Annual fuel cost saving at 2008/09 prices £6,000
Payback period 12 years (inc. cost of radiator system)
Installation cost and funding
Boiler system £42,000
Funding source Scottish Biomass Heat Scheme
Funding support rate 50% of additional costs of woodfuel system
  • Utilises estate-owned timber and adds value to woodlands
  • Improves woodland management and silvicultural practices
  • Self-sufficient fuel supply
  • Increases fuel security
  • Provides efficient heating and hot water for nine units
  • Reduces heating costs