Ashley C of E Primary School

Background

Ashley C of E Primary School in Walton-on-Thames consists of a main school building containing the assembly hall, classrooms, canteen and offices, with 2 other buildings both housing classrooms only. Each building had its own gas fired boiler providing both space heating and hot water.

The main building has a boiler room in its basement, which until early 2007 had two gas boilers; one for the provision of hot water via a calorifier, the other providing space heating. During February 2007 the heating boiler completely failed, leaving the school to rely on portable electric radiators to provide back up heating. This proved to be both expensive and inadequate, and the school looked to install a new boiler for the following winter.

With a general increasing awareness of environmental issues and the need to look to alternative fuels, the school decided to consider the installation of a biomass boiler.

Solution

The ideal location for a biomass boiler is in the existing basement boiler room. The reason for this is the adjacent basement store room, which had previously been a coal store when the school had had a coal fired boiler many years before. A manhole cover outside the building accesses a chute through which coal had been delivered. Access to the boiler room is via an outside door and down two flights of stairs.

A variety of potential fuel types for a biomass boiler were discussed with the school, however it was decided that the preferred fuel would be wood pellets. This decision was in part made because of the relatively small storage space available which made the use of wood pellet, instead of woodchip, more practical.

From energy consumption data for the school it was decided that a 35kW biomass boiler would act as the lead boiler with back up from the existing gas boiler. The lead boiler would provide both space heating and hot water, with the gas boiler providing assistance during periods of extreme demand only.

Installed Boiler Type

KSM Multistoker 375-35 Automatic

This unit is designed to operate with an externally located fuel hopper or store and features a fire damper, filling indicator and flexible screw control. As installed, the boiler is located in the basement boiler room with the existing gas fired boiler. The adjacent store room has been fitted out, by Asgard Biomass, with a stud wall to create a square pellet store. A single sloping floor and sweeping arm device with fuel feed screw has been installed. This screw discharges, through the joining wall, directly into the back end of the boiler.