Biomass case study

Case Study

Biomass Boiler Installation at Fonthill Primary School, Bristol

IntroductionLocated in the north of Bristol, Fonthill Primary School has some 250 pupils. It includes pre-school/reception years, runs a breakfast club as part of the extended school’s curriculum, and houses the Bristol Arts and Music Service on the site. The existing heating system consisted of two oil-fired boilers in each of the two main blocks on site, both of which were nearing the end of their life, and incurring increasingly high running costs. A more modern gas-fired boiler also heated part of one block. The move to biomass rather than gas was part of Bristol City Council’s overall strategy to reduce the carbon footprint of public sector buildings.

Project HighlightsThe installation of a 300kW biomass heating system at Fonthill Primary School in Bristol has enabled the school to remove its old oil fired heating system, reducing the site’s annual energy costs by the equivalent of a teaching assistant salaried post, and delivering savings of around 182 tonnes of CO2 per year. The installation also provides a real example of sustainability which is being incorporated into the curriculum. The school is part of the growing number of public sector buildings Bristol City Council has converted to biomass heating, in conjunction with developing a public/private sector partnership in woodfuel supply from its own Blaise Nursery and a local fuel supply initiative.

Fuel delivery to Fonthill Primary School

Biomass case study

Project AimsFonthill Primary School, in conjunction with Bristol City Council Energy Management Unit, wanted to reduce their dependency on oil and replace an ageing, inefficient heating system with a more modern and cost effective solution which also offered a reduction in carbon emissions. With the growing initiative of Bristol City Council Energy Management Unit to pioneer and develop biomass installations as well as its own wood fuel supply system, a wood-chip fired system was an obvious choice. With the school facing budget cuts, the need to reduce energy costs added increased urgency to the programme. Fonthill Primary School’s installation is an important stepping stone in Bristol’s programme, including the establishment of their own wood fuel supply system from the nearby council–run Blaise Nursery using their own scissor lift trailer.

Project DevelopmentHaving been identified by the Carbon Trust’s Biomass Heat Accelerator as a key site to take advantage of biomass heating, Vollmer Engineering were tasked with assessing the viability of a number of different options in terms of plant and wood fuel store locations, plant specifications, fuel type, buildings to heat and cost effective levels of building insulation. In collaboration with the client, it was concluded that a 300kW wood chip boiler with 600kW gas back-up boiler sited in the main (Block A) plant room with a district heat main to the two separate heating systems in Block B was the optimum design solution, and that both buildings should be upgraded with roof and cavity wall insulation. The specification included converting the oil tank store within Block A boiler room to a wood fuel silo, with lifting roof to facilitate delivery and make maximum use of available space. Extensive re-work was necessary internally within the boiller plant rooms and oil stores, including removal of redundant boilers, oil tanks and pipework, asbestos lagged piping from the original heating system, and removing the roof in the main Block A boiler room to install the new boiler.

The design solution reduced the number of

boiler rooms from three to one, and included removal of a total of six oil tanks across two boiler rooms. The project was progressed to the next phase of development through the Carbon Trust’s Biomass Heat Accelerator which covered the following activities:

• Detailed system design.

• Gaining Planning Permission.

• Technical specification of all plant items.

• Assistance with tendering for boiler supplier and main contractors.

• Technical support throughout construction, evaluation and handover.

Through the expert technical assistance provided by Vollmer Engineering Ltd supported by the Carbon Trust, the project delivered a fully integrated biomass solution, incorporating fuel supply and storage within the existing space available for retrofit, and optimising overall system performance to reduce fuel, heating and through-life costs to the school.

Construction began in April 2011, commissioning and handover of the plant was completed in November 2011.

Slinging in new boiler and auger

Projected Biomass SavingsThe cost of processing and supplying Fonthill Primary School with wood fuel is estimated to be 2 pence per kWh. The biomass boiler will deliver nearly 400 MWh of renewable heat per year to buildings. Based on this, the annual income from the Renewable Heat Incentive will be £19,411 per year as shown to the right:

Technology (kWh) Tariff (p/kWh) RHI Value per year

Biomass Boiler – Medium Scale Tier 1 heat generation = 1,314hours x boiler Maximum Continuous Rating (300kW) = 394,200

4.9 £19,316

Tier 2 heat generation = annual heat delivered (398,961) – Tier 1 (394,200) = 4,761

2.0 £95

£19,411

Biomass case study

The total cost savings of the project, through a combination of building insulation, fuel cost savings and reductions in Carbon Reduction Commitment payments, are summarised in the table below:

Table notes: 1. Total heat use has been reduced through improved building insulation.

2. The increase in maintenance cost for a wood chip boiler compared to a fossil fuel boiler is expected to be at least balanced by the fact that the number of boilers has been reduced from five to two and all boilers are modern.

Boiler room roof after fitting of lifting silo lid

Pre-installation fuel costs

Base Consumption Oil 620,000 kWh

Base Consumption Gas 102,000 kWh

Oil price (inc. CCL) 5.0 p/kWh

Gas price (inc. CCL) 2.7 p/kWh

Pre-installation fuel costs £33,754

Post-installation fuel costs

Expected wood fuel consumption 469,365 kWh

Expected gas consumption 49,254 kWh

Gas price (inc. CCL) 2.7 p/kWh

Wood fuel price 2.0 p/kWh

Post-installation fuel costs £10,717

Fuel cost savings £23,037

RHI income £19,411

CRC savings £2,192

Total expected cost savings £44,640

Biomass case study

Technical DetailsThe biomass boiler solution comprises a 300kW KWB moving grate boiler supplied via Econergy Ltd, with twin 4,500 litre thermal stores to maximise the operational efficiency of the biomass system. The thermal store can be charged up in periods of lower site demand and then used to supply low and peak heat demands that are outside of the operational

range of the boiler, in order to ‘even out’ the demand on the biomass boiler and reduce the requirement for heat from the 600kW gas backup boiler. The biomass boiler replaces oil and gas boilers which were installed across three previous plant rooms in two buildings, with a single integrated plant room, fuel store, and district heat main.

The fuel store is incorporated into the redundant oil tank room and comprises of a rotating agitator and screw auger. Incorporation of a lifting hydraulically powered silo lid enables chip to be tipped straight into the store, and ensures that it can be filled to maximum capacity.

A glass observation window and door access is provided to enable both checking of fuel levels and easy access to the store for non-operational maintenance. The scissor lift trailer delivery system adopted by Bristol provides the most cost-effective and flexible delivery system for this installation and other adjacent biomass sites and their chip production and distribution system at nearby Blaise Nursery. Fuel supply is being brokered through the Westwoods not for profit brokerage, itself mentored and established with the support of Bristol City Council, and a local businessman. Originally supplying clean joinery waste as chipped fuel for Bristol City Council installations, the Westwoods brokerage brings together wood fuel suppliers to tender

Included in these costs are additional improvements to the heating system which were not a necessary part of the biomass heating system, but were undertaken at the same time.

Project Costs for 300kW Biomass Boiler and 600kW Gas Boiler

Mechanical and Electrical Installation £384,190

Construction £89,393

New Gas Main to Site £13,664

Planning and Building Control £550

Structural Engineering Design £2,005

Asbestos Survey £1,500

Design and Project Management £13,632

Total project costs £504,934

for orders, and with its associated fuel quality assurance scheme, ensures chip of the right quality in terms of moisture content and size is supplied.

The biomass heating system and auxiliary boiler are fully integrated via a bespoke automatic control and monitoring system, which allows the entire heating installation to be controlled centrally via a single user interface. The integrated control system ensures that heat at the right temperatures is supplied to the different heating circuits at the right times, that heat is drawn from the biomass boiler in preference to the gas boiler whenever possible, and that all circulation pumps are run at the lowest speed required for successful heat distribution. This strategy reduces the use of fossil fuel and of electrical power to its practical minimum. The control system can be monitored and accessed remotely via the internet.

A breakdown of the project costs is shown below:

Boiler room roof after fitting of lifting silo lid

A summary of the main project facts are tabulated below. The performance and savings of the biomass boiler system are compared against the original oil and gas boiler installation.

Biomass case study

Fonthill Primary School is an important step for the City as part of its overall low carbon programme and introduction of biomass utilising local resources to supply low-cost fuel, including establishing our own internal self-supply system and the setting up of the Blaise Nursery depot.

James King Energy Management Unit, Bristol City Council

Component Unit Note

Biomass Boiler Installation 1no. 300kW KWB Powerfire TDS Boiler supplied by Econergy Ltd.

Auxiliary Plant 660kW Gas Modular Boiler Hamworthy Wessex ModuMax.

Biomass Fuel Source Wood chip Bristol City Council Self Supply.

Biomass Fuel Consumption 153 tonnes/yr At 30% moisture content.

Biomass Fuel Expenditure £9,380 £/yr 2p/kWh to cover cost of chipping.

Heat delivered from biomass 398,961 kWh/yr

Fuel Store Size 42 m3

CO2 Emissions Saved 182 t/yr

Installed Nov 2011 Commissioning and Hand-Over.

Capital Cost £504,934 Including system improvements not directly related to installation.

Annual Savings of Fossil Fuel 673,000 kWh/yr Oil and gas; equivalent to 67,500 litres of heating oil.

Annual savings on Fossil Fuel Costs £25,229 Includes CRC savings worth £2,192.

Estimated Annual RHI Income £19,411

Payback 11.3 years This is the payback for the whole project, including the RHI and additional measures not directly for biomass heating.

February 2012