The task:

A Primary School building in need of a new heating system which complied with Durham County Council policy. The building was built in 1921 and extended to 1250m² in 1970 when a new oil-fired heating installation was built in. The school is in a rural setting between the villages of Cassop and Quarrington Hill in an area of declining population with 90 children of primary school age.

 

The Client:

Durham County Council has had a policy of phasing out solid fuel and oil heating since 1995. 53 oil-fired boiler plants have been converted to natural gas, 34 sites remain on oil and half of these are in rural areas without mains gas. 52 solid fuel sites have been converted to gas and 3 to wood pellet fuel, 4 sites remain on solid fuel. In 1995, when the last deep mine closed in County Durham, tests were carried out on using woodchips from forestry waste as a fuel. These were partially successful but there was general agreement that pellets are more easily handled and the calorific value and moisture content is more constant. After a lot of work, the County Council installed a pellet plant at its Joint Stocks land fill site where clean waste wood is pelletised and dirty waste wood processed for the raw material for chipboard. Wood that would normally be land fillers is reused so there is a saving on landfill tax.

 

Before :

From 2000 to 2003 the school used 22,000 litres of oil per year on average at a cost of about £4,000 a year. The County Council has a contract for oil. The price can vary week to week, however. The 5-year high between 1998 and 2003 was 23p/litre and the 5-year low 10p/litre – an additional disadvantage is that the oil price is affected by world events. The school's central heating is a low temperature hot water system serving radiators and mechanical convector units with a single calorifier for DHW.

 

Installation:

A Köb PYROT 220 kW boiler was selected for the school to be used in conjunction with a 2,2000 litre heat storage accumulator tank. The boiler includes automatic ignition and modulating control as standard and features flue-gas recirculation and automatic cleaning options. A 30m³ fuel store was created from the old coalhouse and a spring extractor and auger system installed to transfer the pellets to the boiler. At the special request of the County Council the boiler and feed system was supplied with a conversion kit to allow woodchips to be used as an alternative fuel should reliable supplies become available.

The boiler is operated in an “always-on-mode” sensing the heat load from the accumulator temperature. The school central heating is controlled by a Siemens weather-compensating control system with optimum start capability. The Siemens controller operates the main school circulating pumps, the 3-port mixing valve and the immersion heater for the DHW when the heating systems is switched off Operation and Pellet Fuel Consumption.

The school caretaker has happily taken on the responsibilities for the boiler. His responsibilities includes a daily visual check on the boiler and weekly cleaning of the ashbox. He shuts down the boiler for a thorough clean every month.
The boiler has now been in use for 3 and a half years and fuel costs have been in line with previous oil bills. Wood pellet fuel is purchased from Wood Pellet Energy Ltd. The pellets are manufactured from clean wast wood at Chilton, 6 miles from the school.

 

After:

The Head Teacher commented: “The woodfuel boiler has made such a difference to the school, it has never been so comfortable. This has obviously an excellent effect on staff and pupils and the fact that we are doing something positive for the environment is an added bonus.” Woodfuel boilers compete with gas on convenience. While a biomass boiler requires a suitable chimney, a larger boiler house, a fuel store with suitable vehicle access, ash removal and periodic maintenance and has potentially higher initial costs, longer term there are many advantages, including the fact that the woodfuel price is more stable and in this case the price has been set for 5 years. The most important benefit to the council is the obvious reduction of CO2 emissions. In 2002 Durham County Council made the MACC2 declaration intending technology. Three other schools in County Durham have had their existing solid fuel boilers adapted to burn emerging technology. Three other schools in County Durham have had their existing solid fuel boilers adopted to burn wood pellets. Cassop was the first schools to receive a purpose-built wood boiler. Augers were purchased enabling wood pellet fuel or woodchips to be used and the County Council is growing short rotation coppice on some land reclamations sites.