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Kincardine Castle, Aberdeenshire

Kincardine Castle, Aberdeenshire

Work was carried out to install a more efficient, economical and sustainable heating system in Kincardine Castle.

Overview

This study describes the installation and running of a biomass system. It concerns the work carried out to install a more efficient, economical and sustainable heating system in Kincardine Castle in Aberdeenshire. Two biomass boilers were installed reusing the existing heating pipe runs and radiators, minimising intervention to fabric. The owner is using timber from the Estate to provide fuel for the boilers. The project was considered viable due to funding available under the UK Government’s Renewable Heat Incentive.

Kincardinecastle

Image: Kincardine Castle ©Historic Scotland

Approach

Building Details

Kincardine Castle is a Scottish Baronial style, B-listed country house in Deeside. It was constructed in 1894 and has been a family home ever since. The current owners began to use the Castle for commercial purposes (weddings, parties, events) in 1985. Modifications to the building to ensure it complied with fire regulations and to increase the bathroom provision were carried out prior to this study.

Existing Heating Provision

Originally there were two heating circuits within the building. The first served the main house, providing heating and hot water from a multi-fuel boiler and hot water cylinder. The owners had tried using coal and wood to fuel the boiler before settling on oil as restoking and de-ashing was a problem. The heating in the main house would run 24 hours per day, controlled by thermostats.

The second heating circuit served the basement area which was previously a self-contained flat. This circuit had an oil fired boiler with a time-clock control.

In total, 23,000 litres of oil were consumed per year. The heating system was felt to be inefficient as rooms were not at a suitable temperature and the running costs were too great.

Biomass System

A wood chip boiler and a smaller log burning boiler (total capacity of 153kW) were installed in a purpose built boiler house adjacent to Kincardine Castle. Wood was chosen as the most suitable fuel as the Castle's large forested estate make producing logs and chips on-site a viable option. The new biomass boilers are connected to the existing circuits and the oil boilers remain as a back-up as it was expensive to remove them. New radiators were installed in a number of rooms to replace electric heaters.

The plan is to use windblown softwood trees and SRW (small round wood) from Kincardine Estate, and thinnings and fellings from the estate and surrounding area, and/or timber sourced off site to feed the biomass boilers.

Wood that is to be chipped must first be dried to the required moisture content (less than 30%) to prevent them composting during storage. A ventilated storage shed was used as a temporary storage facility while a purpose built storage area is constructed.

 

Performance

Heat Production

The cost of wood chip depends on the type of wood used and the amount of timber chipped at one time. As can be seen below, it is more economical to chip larger amounts of timber at one time.

Cost of Chipping
Time 1 hour 2 hours
Cost of Timber (at £28/tonne) £700 £1,400
Cost of Chipper (positioning fee of £145 plus £120/hour) £265 £438
Cost of Lorry £100 £180
Cost of Fuel £40 £80
Total Cost £1,105 £2,008
Tonnes of Wood Chip Produced (Dry weight) 12 24
Cost of Wood Chip/Tonne £92.08 £83.66
Cost of Wood Chip/kWh (assuming 3,200kWh/tonne of dry chips) 28.8p 26.1p

 

During the first year of operation, the biomass boilers produced 238,149kWh, of which 35,919kWh was lost between the boiler house and the main house. The log boiler produced 12,000kWh over the first year. From March to November, wood chip was procured off-site, thereafter it was produced within the Estate. The table below shows the estimated cost of fuel for the boilers.

 

Cost of Fuel
Log Boiler Free (excluding labour)
Wood Chip Boiler 2.8-3.12p/kWh (estimated buy-in costs)
Oil (previous fuel) 7p/kWh (approx.)

 

Although there were savings in electricity due to the replacement of old electric heaters in some rooms (estimated at £833/annum), the new biomass boilers do require electricity to run the pumps, stoker and ignitor. The total cost of electricity for these functions is around £2,000 per annum. However, savings on oil costs were significant at £8,089.

 

Net fuel savings for year one were almost £7,000.

Renewable Heat Incentive

RHI Payment Calculations
Tier kWh RHI per kWh Service Contract per kWh RHI net of Service Contract Net RHI receipts
Tier 1 201,042 7.9p 1.3p 6.6p £13,268
Tier 2 1,188 1.9p 0.6p 1.3p £15

Total

202,230

-

-

-

£13,283

 

 

Adding the RHI payments to the calculated fuel savings gives a total positive cash flow of £20,205 per annum.

This results in a ten year payback period (on an initial capital cost of £201,538). Excluding RHI payments, the payback period would be extended to over 30 years.

Around 56.3 tonnes of fossil fuel related CO2 emissions have been saved by the introduction of the biomass boilers.

Lessons

During the first year the back-up oil boilers were used due to a number of relatively minor issues; de-pressurisation of the system (air bubbles moving around the circuit and being vented at air-valves), running out of wood chip, failing to empty ash container in time, failure of the igniter and failure of the flue-gas temperature sensor. Oil consumption in future is expected to be reduced as the de-pressurisation problems have been resolved and operational errors should reduce as staff become more familiar with the system.

Based on the first year’s usage the biomass boiler system is expected to use approximately 65 dry tonnes of wood chip each year. This equates to around 130 tonnes of fresh timber, which in turn, equates to the annual growth from about 12 hectares of woodland.

Transmission losses are greater than expected at 15%. Heat is lost from the pipework that carries heat 50 metres into the building from the external boiler room. Improving the insulation of the pipework, by utilising a twin-pipe solution, rather than the current twin-core option would reduce these losses.

 

The project was economically viable due to the availability of RHI funding which reduced the payback period from over 30 years to 10 years, however for the owners, the greatest benefit is that the Castle can now be kept comfortably warm all winter.

 

The video below was produced by the biomass boiler providers, hwenergy and features the owner of the Kincardine Estate, Andrew Bradford who discusses the project.

Links

Historic Scotland   

Kincardine Castle

hwenergy

Refurbishment Case Studies   

 

Resource Efficient Scotland supported the preparation and presentation of this case study for the Retrofit Scotland website.

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