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Housing development

Gilbert Properties wood fuel case study

  • Location: Jedburgh, Scottish Borders
  • Wood fuel usage: district heating scheme for a development of eleven (will eventually be twelve) domestic properties (a mix of steading conversion and new build)
  • Installation date: November 2009

Reasons for choosing woodfuel

Gilbert Properties wanted to use a renewable, carbon-lean fuel to reduce the carbon footprint of their new development.

The site is in an area with no main gas network but situated just six miles from a source of woodfuel. Alternative fuels (oil or LPG) would have been more costly to operate as well as less environmentally friendly.

Having a secure local sustainable source of energy, not subject to the price fluctuations of fossil fuels, means that annual energy costs are predictable.

System features and benefits

Gilbert Properties augerThe nine properties are connected by a heating pipe network which distributes heat generated from a central wood fuel boiler.

Known as a district heating scheme, this system is cost effective since a single boiler, boiler house and fuel store supply all nine properties, reducing installation and maintenance costs.

In addition, each property saves space with only a heat exchanger and small heat meter needed inside the house.

The heat meters allow accurate fuel bills to be produced for each customer based on delivered heat.

Each house is also fitted with solar panels that connect to an independent hot water cylinder. This heats water in the summer, further reducing energy bills.

A solar programmer automatically activates the biomass boiler if the water temperature is not high enough.

Wood fuel supply

Woodfuel is supplied by Border Ecosystems, an energy services company (ESCo), who also maintain the system and read meters.

Wood chips are delivered from a source six miles away, every three weeks in winter and every six weeks in summer.

To maintain this supply, the ESCo is working alongside local wood suppliers to guarantee a continuous cycle of replanting following harvesting.

Lessons learned

  • Work with local timber suppliers to source supply of fuel prior to installation design in order to ensure compatibility
  • The district heating pipework insulation works very well, with minimal thermal losses
  • Installation personnel with a depth of experience are recommended
  • Seek multiple sources of advice to compare opinions
  • Investing in independent advice to ensure the correct system and design to suit your needs at the beginning might save you money in the long term
  • Information on how to meter and charge customers can be difficult to locate, so seek information from your experienced installer
  • Get a qualified heating engineer to guarantee the system so that you have some come back if it does not deliver what is promised
  • Gilbert Properties have found the woodfuel experience, on the whole, very positive. Now they have had the system for a while and fully understand it, they definitely consider it superior to a fossil fuel system. They find that woodfuel boilers produce more heat than equivalent sized oil boilers
  • Running the boiler at optimum capacity and efficiency maximises the economic benefit of a woodfuel system.

Facts and figures

Note: figures are approximate

Building
Fabric Timber frame kits with stone skin and 150mm of insulation
Heating system
Boiler system ETA boiler with accumulator vessels and underground delivery pipework, plus integrated solar panel programmer
Maximum boiler output 130 kW
Fuel type Wood chip
Fuel specification Moisture content: 30% (M30)
Back-up/top-up system Each house has solar panels linked to wet system
Wood fuel store and handling A purpose-built wood chip blower trailer provides the delivery service to an above ground storage hopper
Wood fuel store capacity 48m3
Fuel Supply Contract ESCo Service - supply and deliver chip, read meters and maintain boiler
Fuel consumption, costs and savings
Annual wood fuel use 60-70 tonnes- this figure will rise with the recent addition of new properties to the system
Annual energy consumption 260,000 kWh
Annual CO2 savings 62 tonnes
Wood fuel cost £100 per tonne for supply, delivery, system maintenance and meter reading
Annual fuel cost saving £5,080 (this figure will likely change with the addition of thenew properties)
Installation cost and funding
Boiler system £110,000 overall project cost
Funding source Scottish Biomass Heat Scheme (see note below)
Funding support rate 50% of additional costs over fossil fuel equivalent
  • Environmentally friendly heating solution
  • Lower energy bills for householders
  • Local employment created through wood fuel harvesting and processing
  • Short distance to secure fuel supply reduces energy costs