Climate Berkshire: Rural Renewable Energy Study Phase II: Pre-feasibility

Transcription

1 Climate Berkshire: Rural Renewable Energy Study Phase II: Pre-feasibility December 2010

2 This report has been prepared by TV Energy Ltd for West Berkshire Council under the auspices of the Climate Berkshire initiative. Report reference TVR183. Aerial photographs courtesy of Google Earth. Prepared by: Approved by: Michael Beech Technical Advisor Keith Richards Managing Director TV Energy, Liberty House, The Enterprise Centre, New Greenham Park, Newbury, Berkshire RG19 6HS Website: Telephone: Fax:

3 CONTENTS EXECUTIVE SUMMARY INTRODUCTION Background and Objectives Report Methodology Scope of Report SITE DETAILS & ENERGY DEMANDS Site Description Building Details, Existing Energy Supplies & Heat Demands SITE ASSESSMENT Location of Biomass Boiler Central Heat Plant & Enclosure Woodfuel Delivery, Storage & Transfer Woodfuel Delivery & Storage Volumes Heat Supply & Connections Project Economics ANALYSIS Technical Analysis Equipment Sizing & Energy Calculations Core Heat Loads Extension Heat Loads Financial Analysis Operating Costs & Revenues Core Heat Loads Extension Heat Loads Project Capital Requirements Central Boiler House District Heating Heat Interface Units Capital Costs Environmental Analysis SUMMARY & CONCLUSIONS TV Energy/ Report183 3 December 2010

4 EXECUTIVE SUMMARY This report assesses the village of Brightwalton as the subject of a proposed biomass district heating (and provision of hot water) scheme fuelled from locally sourced woodchip, and aims to determine outline technical and financial feasibility. The report forms Phase II of three phases of the Rural Renewable Energy Study, part of the Climate Berkshire initiative. The village does not support the application of Combined Heat & Power (CHP) plant to supply the majority of the total heat load, a CHP plant needs to operate essentially year-round for economic viability, and in any case is technically challenging at small (kw) scale when fuelled by woody biomass. A biomass heat-only boiler is therefore examined as the application for this project. The following extended summary provides an overview of the project concept, results of the technical and initial financial analysis, assessment of overall viability and an outline of the third stage of the project. Deploying such a scheme as is envisaged here will markedly reduce the carbon footprint of the village and would form the core of a wider initiative to harness local green energy resources potentially making Brightwalton one of the most sustainable rural communities in the United Kingdom. An exemplar to be replicated elsewhere and a demonstration of the Big Society in action. The analysis examines the case for a district heating scheme supplying heat from a central biomass boiler to a number of core heating loads including the primary school, church and village hall in various combinations. Further analysis considers additional heat loads separately as extensions to the core scheme, comprising three sets of social housing and a selected number of privately owned dwellings. Heat demand is currently provided by a mix of individual boilers fuelled by either heating oil or LPG, electric storage heaters or solid fuel. The total current heat demand of the buildings forming the core loads is estimated to be approximately 110MWh/yr, plus around 500MWh/yr for the total heat demand of the buildings making up all of the extension loads. The total heat demand for the largest scheme examined is therefore approximately 610MWh/yr. An aerial photo of the village showing individual heat users and approximate routes for district heating pipework is shown below. TV Energy/ Report183 4 December 2010

5 A Energy centre location Option 1 B Energy centre location Option 2 1 School main boiler 2 School second boiler serving hall 3 Village hall boiler 4 Church boiler 5 District heating pipework route to Southern Housing properties 6 District heating pipework route to A2 Dominion Housing properties 7 District heating pipework mains to residential connections 8 Individual connections to private dwellings 9 District heating pipework mains to residential connections 10 Individual connections to Sovereign Housing properties NB. Additional private dwellings along The Street/ Ash Close might also wish to join a scheme. This has not been considered in the initial appraisal but would undoubtedly add to the technical and economic feasibility of the scheme. The analysis has determined that the project is technically feasible. The majority of the annual demand for heat can be supplied from new biomass boiler plant located either at the school or the village hall, supplemented by sufficient oil boiler capacity to provide peak loads and full backup capability, replacing the need for existing local heating plant. Heat would be supplied through a new district heating system, a network of insulated flow and return pipes buried below ground, and connected to each end user via heat exchangers and including a heat meter to measure individual heat consumption, as heat interface units (HIUs). The core heat loads would require between 30 and 38tonnes per year of woodchip at 30% moisture content, the full extension heat loads would require an additional 175tonnes of woodchip per year. Woodchip would be delivered to the fuel store using a tractor-trailer vehicle, requiring a minimum period between deliveries of 4 days for the largest project (core plus all extension loads) during a very cold period, assuming a trailer capacity of 18cubic metres or around 4.5tonnes of woodchip. TV Energy/ Report183 5 December 2010

6 Project Operation The financial picture in terms of operation of the scheme is summarised in the tables below. The cost of woodchip is set at 90 per tonne (30% moisture content) and heating oil at 55pence per litre. Other operating costs include central plant utilities (electricity and mains water), maintenance of the central plant & local equipment and administration costs associated with operation of the district heating scheme. The cost of capital replacement is also included, to cover the cost to replace plant and equipment over the life of the project. Project revenues are made up of fixed and variable charges to heat users. Fixed or standing charges are calculated as equivalent to the avoided cost of local heating plant maintenance, insurance and capital replacement. Variable heat charges are based on the amount of heat supplied as measured by each local heat meter, charged at a rate equivalent to the cost of heating oil (55pence per litre) and applying a boiler seasonal efficiency of 85%, giving a heat charge of 6.28p/kWh. The effect of the anticipated Renewable Heat Incentive (RHI) is also shown, based on a rate of 5.2p/kWh of heat supplied from biomass. Variations in any of the fixed or variable costs and/ or revenues will affect the financial performance of all of the projects examined. Core Project Option 1 Option 2 Option 3 Option 4 School School plus church School plus village hall School plus village hall plus church Project Net Income Without RHI Option 1-13,539 /yr Option 2-11,349 /yr Option 3-12,378 /yr Option 4-10,368 /yr Including RHI Option 1-9,094 /yr Option 2-6,670 /yr Option 3-7,086 /yr Option 4-4,842 /yr The figures suggest that none of the core scheme options are commercially viable in terms of project net income. It is apparent, however, that with increased heat supply the situation improves, as a significant percentage of the operating cost of the district heating scheme is associated with plant and equipment maintenance, and administering the operation. The effect of the RHI is not sufficient to provide a financially viable project. Extensions Extension 1 Extension 2 Extension 3 Extension 4 Social housing no.1 (Southern Housing) Social housing no.2 (A2 Dominion Housing) Typical private dwelling (up to 7 potential connections) Social housing no.3 (Sovereign Housing) TV Energy/ Report183 6 December 2010

7 Project Net Income (largest core scheme plus each extension) Without RHI Extension 1-9,353 /yr Extension 2-9,906 /yr Extension 3 (for one connection) - 9,875 /yr Extension 3 (for all 7 connections) - 6,917 /yr Extension 4-11,113 /yr All extensions - 6,185 /yr Including RHI Extension 1 1,105 /yr Extension 2-33 /yr Extension 3 (for one connection) - 3,079 /yr Extension 3 (for all 7 connections) 7,499 /yr Extension 4 1,464 /yr All extensions 24,562 /yr The largest core scheme (option 4) plus extensions increases the amount of heat supplied and hence project revenues, these being greater than the increase in operating costs. A critical mass of heat load is therefore required in order for the project to demonstrate financial viability. The core scheme plus all extension projects as a group of connections demonstrate a net project income when the RHI is included, excluding project financing. Without the RHI none of the extensions to the largest core scheme are financially viable, neither individually or together as a group. Project net income for the largest core scheme plus all extensions including the 7 private dwellings is 24,562 per year when including the RHI. All of the heat connections show significant reductions in CO 2 emissions associated with providing heat compared to the existing situation, around a 90% saving in most cases. This is principally due to the difference between the carbon intensity of heating oil compared to locally sourced woodfuel. The largest core scheme would provide CO 2 emissions savings of 32.2tonnes per year, when combined with all of the extension connections the CO 2 emissions savings would total 87.2tonnes per year. Project Capital The capital cost of the central boiler house, biomass boiler (90kW) and oil boiler (200kW), fuel storage and associated mechanical and electrical equipment is estimated at 116,000, to supply the largest core scheme (option 4). To supply all of the extension connections as phase 2 of the project an additional 74,500 is required to install a second biomass boiler (150kW) and oil boiler (300kW) plus mechanical and electrical connections. Oil boiler capacity would be sufficient for the supply of peak loads and the entire connected load for all buildings as backup. The central boiler house building would measure approximately 6m by 8m by 3m high (internal) excluding the biomass fuel store which would be sited adjacent to the boiler house either above or below ground, the latter providing many operational advantages over the former but with higher capital cost (including in the above figures). The fuel store would measure 4.5m by 4.5m by 3m deep (internal), sufficient in capacity for the largest core project plus all of the extension connections. TV Energy/ Report183 7 December 2010

8 The cost of the district heating pipework to supply the core heat loads ranges from 22,500 for the school alone, 12,000 to additionally supply the church, and an additional 30,000 to supply the school and the village hall together. The costs of final connections from the district heating terminations to the existing internal heating systems at each building are 7,500 for the school (two HIUs), 5,000 for the church and 3,500 for the village hall. The cost of the district heating network to supply all properties within the block owned by Southern Housing (Butts Furlong) is 18,000. The cost of the district heating network to supply all properties within the two blocks owned by A2 Dominion Housing (Dunmore Meadow) is 32,000. The cost of the district heating pipework mains to supply the privately owned dwellings immediately to the south of the school and church is 42,000, the cost of extending this main further east along Ash Close to supply properties owned by Sovereign Housing is 50,000. The cost of district heating pipework supplying each individual domestic property ranges between 1,000 for private dwellings to 1,500 for the Sovereign-owned houses. The cost of final connections as HIUs to each dwelling is 2,500, excluding the cost of any new internal radiator systems and hot water cylinders required. In terms of capital contribution and project financing, it is anticipated that the cost of the central plant as a minimum would be borne by the district energy scheme owner(s), minus any contributions from capital grants. It is anticipated that the cost of any district heating mains not dedicated to supply any single end user would also be borne by same. End users would be expected to contribute a % of the capital cost of district heating pipework branches dedicated to supply those users along with individual HIUs, the cost equivalent to that of replacing the existing local heating plant with a new oil boiler. It is assumed that this contribution by end users to the cost of connection is equal to the cost of district heating pipework branches from the mains, plus HIUs (i.e. 100% of the capital cost). The breakdown of capital costs is as follows: Capital cost breakdown Central Plant Building (largest core scheme plus all extensions) 190,500 District heating pipework to school 22,500 Heat interface units for school 7,500 District heating pipework to church 12,000 Heat interface unit for church 5,000 District heating pipework to village hall 7,500 Heat interface unit for village hall 3,500 District heating pipework to Southern Housing properties 18,000 Heat interface units for Southern Housing properties 15,000 District heating pipework to A2 Dominion Housing properties 32,000 Heat interface units for A2 Dominion Housing properties 20,000 TV Energy/ Report183 8 December 2010

9 District heating pipework mains to 7 private dwellings 42,000 District heating branches plus HIU for each private dwelling 3,500 (average) District heating pipework mains to Sovereign Housing properties 50,000 District heating branches plus HIUs for Sovereign Housing props. 20,000 The total capital required to implement the largest project and thus provide a significant amount of operating income to the scheme is estimated at 508,500. This does not include the cost of providing new central heating systems in those residential properties which are currently served by electric storage heaters or solid fuel systems. Some of this cost would be expected to be provided by end users, to cover the cost of connection of the district heating to each individual property or groups of properties. Depending on precisely how this cost is determined and allocated to end users as groups or individuals, the capital cost of common items of energy plant and infrastructure to be borne by a third party contracted to deliver and operate the district heating scheme is likely to be in the region of 300,000, to include the central plant building and district heating mains serving a mix of end users. The third phase of this study will deal in detail with the opportunities for obtaining contributions towards the capital cost of the scheme. A significant level of grant support will be essential to make this project viable. The following sources are currently under investigation: RDPE funding through the local LEADER project (North Wessex Downs AONB) and directly through SEEDA Greenham Common Trust and West Berkshire Partnership Ashton awards Various utilities The target is of the order of 50% of the core costs (around 150,000). The third phase will also investigate different business models and a potential community ESCo (Energy Services Company) that might manage and administer the scheme for and on behalf of the local community. TV Energy/ Report183 9 December 2010

10 1 INTRODUCTION 1.1 Background and Objectives This report forms Phase II of the Rural Renewable Energy Study, part of the Climate Berkshire initiative. Phase I of the project described the methodology and outcome of a site selection process to determine the most suitable location for a woodfuelled district heating scheme to provide low carbon heat to a community within West Berkshire. The results of the analysis and subsequent review with project sponsors confirmed the village of Brightwalton to be the subject of further analysis via a prefeasibility report to outline the technical and financial aspects of the potential scheme. The key objective of this study is to investigate the potential for using locally supplied biomass in the form of woodchip to fuel a new boiler, supplying heat to domestic and non domestic buildings in Brightwalton village. The district heating scheme would be expected to evolve from supplying core anchor loads initially, extending over time to include additional buildings depending on technical and financial viability. A biomass-fuelled heat supply system will generally result in lower operating costs compared to conventional systems due to the cost differential between woodchip and fossil fuels. CO 2 emissions will also be substantially reduced compared to conventional systems and fuels. Other benefits of introducing biomass as a fuel are the potential to be able to source fuel locally, provide fuel flexibility, present opportunities for local employment and ensure increased long term security of energy supply. 1.2 Report Methodology The characteristics and heat consumptions associated with the buildings to be supplied with biomass fuelled heat are analysed and presented from historical data describing consumption of heating fuels (heating oil, electricity and coal-based solid fuel) and estimates heat demand for properties where no consumption information is available. A biomass district heating scheme is then assessed to supply the buildings as required, to tie into existing energy supply systems. This takes the form of a technical feasibility which assesses the operational requirements of the buildings on a daily and seasonal basis leading to determination of peak heat loads which in turn provides a calculated boiler capacity. Estimated annual heat consumptions are translated into requirements for biomass fuel which enables the fuel store to be sized, taking into account the size of the boiler, duration of the maximum heat demand and capacity of woodchip delivery vehicles. The size of the boiler house is estimated based on the biomass heat system and inclusion of backup boiler plant if required. District heating pipework sizes are determined from the difference in temperature between supply and return temperatures and the maximum heat load occurring in each portion of the network. An approximate route is laid out based on the proposed location of the boiler house, the buildings to be connected and existing constraints in the area such as public access routes, other buildings and utility services. A financial analysis considers the capital investment in the central biomass boiler, associated supporting equipment, civil works and heat supply infrastructure, and

11 compares this with ongoing operating costs and revenues over the project lifetime to determine the economic viability of the project. The impact of including potential capital grant funding is assessed, along with revenue support mechanisms such as the Renewable Heat Incentive (RHI), anticipated to be introduced in June All costs presented exclude VAT. 1.3 Scope of Report The report seeks to address the initial stage of feasibility assessment, to include the following items. Analysis of existing energy demands Determination of core heat loads and potential for additional future connections Sizing and operation of central biomass boiler and associated infrastructure Sizing and layout of heat supply network, outline heat user connections Assessment of biomass fuel supply, storage, consumption of fuels Assessment of CO 2 emissions associated with energy use Estimates of capital costs, operating costs and revenues Outline of capital and revenue support measures Financial analysis to determine economic viability of project 11

12 2 SITE DETAILS & ENERGY DEMANDS 2.1 Site Description Brightwalton village is located in West Berkshire, approximately 15km to the north of Newbury, and has a population of approximately 350. An aerial photo of the village is shown below. Brightwalton village Brightwalton is not connected to mains gas and the buildings and other services rely on a mix of individual oil boilers, electric heating or solid fuel to provide space heating and hot water. The village falls within the North Wessex Downs AONB and parts within an additional designated conservation area. The buildings providing the focus of the village are the primary school, church and the village hall, these are shown below. 12

13 Brightwalton village showing the school, church and village hall The core buildings subject to this study comprise: Brightwalton CofE Primary School Brightwalton All Saints Church Village Hall In addition, some or all of the following domestic properties offer additional heat loads as extensions to the district heating scheme: Social Housing no.1 (James Butler Housing Association) A Social Housing no.2 (A2 Dominion Group Housing Association) B Social Housing no.3 (Sovereign Housing Association) C No. 44 Brightwalton D Elm Cottage E School House F Appletree Cottage G Hazelnut Cottage H Christmas Cottage I Edmunds Cottage J NB. Additional private dwellings along The Street/ Ash Close might also wish to join a scheme. Likewise the old vicarage complex. This has not been considered in the initial appraisal but would undoubtedly add to the technical and economic feasibility of the scheme. The properties considered are shown below. 13

14 Brightwalton village showing core and extension heat loads The overall thermal performance of the buildings is expected to be mixed depending on the age and construction quality, with some of the older properties anticipated to be difficult to heat efficiently due to high thermal losses through building fabric and fittings due to poor thermal insulation properties and generally significant uncontrolled ventilation. It can be assumed therefore that some scope exists to improve upon the existing situation through the fitment of additional wall and roof insulation, replacement double glazed windows and draught exclusion materials where existing physical constraints and planning restrictions allow. There may also be scope for improving the efficiency of hot water provision through fitting additional or replacement insulation material. These actions will result in reduced demand for heat and consequently reduced consumption of fuel. Conversely, the availability of heat priced competitively (against existing fuels) may lead to higher use providing a better quality environment. This is particularly the case for the church where higher use is anticipated if such a scheme is implemented. This has the additional benefit of helping to conserve this historic building and its contents. 14

15 2.2 Building Details, Existing Energy Supplies & Heat Demands A summary of potential connected heat users, existing boiler details and estimated heat demands are shown in the tables below. Heating Existing heating plant oil consumption heat demand estimated main 2nd space heating estimated hot water Property kw kw l/yr kwh/yr kwh/yr kwh/yr notes Primary school , ,150 80,520 6,000 2nd boiler serves hall Village hall 53 2,000 20,600 14,480 2,000 Church 180 1,000 10,300 7,210 0 existing boiler due for replacement Social Housing 1 (Southern Housing HA) Social Housing 2 (A2 Dominion HA) Social Housing 3 (Sovereign HA) 15 ea. 72,000 24, ea. 56,000 32, ea. 101,250 36,000 estimated figures. 2 x 3bed, 4 x 2bed, 100% electric heating estimated figures. 3 x 3bed, 5 x 2bed, oil boilers estimated figures. 9 properties, solid fuel, electricity and oil mix Privately owned houses 25 3,000 30,900 20,720 4,000 average figures, per dwelling (7), each Table of potential individual heat connections Existing heating plant Heat demand main 2nd estimated space heating estimated hot water total Potential heat connections kw kw kwh/yr kwh/yr kwh/yr Core Primary School, Village Hall, Church ,210 8, ,210 Extension Social Housing 1 (James Butler HA) 90 72,000 24,000 96,000 Social Housing 2 (A2 Dominion HA) 96 56,000 32,000 88,000 Social Housing 3 (Sovereign HA) ,250 36, ,250 Private residential ,008 32, ,760 Subtotals 376, , ,010 Totals 478, , ,220 Summary table of potential heat connections by group Heating oil and LPG consumption figures are taken from individual records of previous deliveries to each property where available. Heat demands are estimated based on oil and LPG consumption figures, applying a seasonal boiler efficiency figure in each case of between 70% and 85% depending on the estimated age of the boiler. In cases where no heating fuel consumption data is available, estimates of space heating and hot water demand are based on the size and age of construction of the individual property. The split between space heating and hot water demand is estimated based on a hot water demand figure typical for each building type and 15

16 assumed occupancy, taking into account the total fuel consumption figure for each property where available. The anticipated core of the district energy scheme, to include the school, village hall and church presents a combined total heat demand of 110,210kWh/yr. The school individually has a heat demand of 86,520kWh/yr or 80% of the total. All three buildings are currently supplied with heat from individual oil fired boilers and each is understood to feature an internal wet heating system supplying radiators. Social housing 1 and 2 are located adjacent to each other to the north of the village hall and are arranged in two separate areas, together these provide a total heat demand of around 184,000kWh/yr. Social housing no.1 comprises 6 dwellings in a single block estimated to be roughly 20 years old, these feature electric heating using storage heaters and immersion elements within hot water storage cylinders. Double glazed windows are fitted throughout. These properties would require new internal wet heating systems supplying radiators and hot water storage cylinders if connected to the district heating scheme. Social housing no.2 comprises 8 dwellings arranged in two blocks of terraces, these are recently constructed and would be anticipated to perform well in terms of heat loss. These are heated using individual oil fired boilers located at the rear of each property. Social housing 3 comprises nine properties as semi-detached dwellings located east of the core heat loads, and generally dispersed. The heating systems are mixed, with five understood to use solid fuel, three 100% electricity and one an oil boiler. With the exception of the oil heated property these would require new internal wet heating systems supplying new radiators and hot water storage cylinders if connected to the district heating scheme. The heat demand of all nine dwellings is estimated to be around 137,000kWh/yr. There are seven remaining properties to the south and within relatively easy reach of the core heat loads, all are privately owned detached dwellings each with its own oilfired boiler and central heating system, with at least one including an aga to provide hot water. One property additionally includes an LPG fuelled boiler to heat an outdoor swimming pool. The combined heat demand of all seven properties is estimated to be around 180,000kWh/yr. The average combined space heating and domestic hot water demand per property is approximately 25,000kWh/yr. There may be further connections which could be made to the district heat network which would increase the amount of heat supplied, however these have not been specifically examined in this report. These potential connections would be made to privately owned dwellings on an individual basis. It should be noted that the heat mains which supply collectively both the core and secondary (extension) heat loads would be sized with sufficient additional capacity to support additional connections in future. The total space heating demand for all potential connections is calculated at 478,468kWh/yr, for hot water 132,753kWh/yr. The total heat demand is 611,220kWh/yr. The overall heat demand is evidently for the most part seasonal, representing 78% of the total. In the case of the core loads the total heat demand is even greater skewed towards space heating, with 102,588kWh/yr out of a total of 16

17 110,210kWh/yr, or 93% as a seasonal heat demand. This situation does not support the application of Combined Heat & Power (CHP) plant to supply the majority of the total heat load, a CHP plant needs to operate essentially year-round for economic viability, and in any case is technically challenging at small (kw) scale when fuelled by woody biomass. A biomass heat-only boiler is therefore examined as the application for this project. The school is assumed to experience peak heat demand between and Monday to Friday, after which the load will reduce. The village hall will require heat depending on the timetable of activities and occupancy, anticipated to be a mix of uses as a nursery during weekdays and various meetings and social events at other times. The church is understood to be used infrequently, this is borne out by the small annual heat demand compared to the size of the building and boiler capacity. The remaining loads are domestic and these would be expected to experience peak heat demands between around and days per week, tailing off during the daytime depending on occupancy and increasing again towards the end of the afternoon and into the evening. This mix of heat demand profiles are relatively complimentary in that peak demands occur at different times which when supplied from a single central heat source means a much reduced boiler capacity compared to the total of all individual boilers, giving longer plant operating hours and improved efficiency of capital. The figures described above are used within the analysis tables and subject to further interpretation within the calculations which follow. 17

18 3 SITE ASSESSMENT The following section details the analysis relating to the inclusion of biomass heating to serve the village. The main elements of energy plant along with supporting infrastructure are outlined below. 3.1 Location of Biomass Boiler The site is examined for the potential to supply heat generated from a central biomass boiler, taking into account the opportunities and constraints due to the layout and nature of the buildings, vehicular access, location of existing services and other physical obstructions. The connected loads included in the analysis for central biomass heat supply are those as described in the previous section, split as core and extended supply. Due to the physical size of the boiler equipment and space restrictions within and directly adjacent to existing buildings the new biomass boiler plant is likely to be located remote from the buildings to be served, within a new boiler house where there is sufficient access and space for woodfuel deliveries, reception and storage. A potentially suitable location has been identified to the rear (west) of the village hall, this is shown in the photo below. Possible location for biomass boiler plant near to the village hall The central heat supply location is considered suitable from the point of view of access for fuel deliveries, available space for plant and equipment, proximity to heat loads and potential routes for new heat supply pipework to connect buildings to the central system. Further investigation will be required to assess whether the building/ land owner is willing to offer this site as the location for the central boiler plant. A potential alternative location is within the school grounds. A suitable space would need to be found, currently all areas appear to be allocated for car parking, recreation or storage buildings. The access into the area appears to be suitable to accept 18

19 woodfuel delivery vehicles. One possible location at the school is shown below. Possible location for biomass boiler plant within the school grounds In both cases the provision and arrangements for woodfuel deliveries would require careful management to ensure that suitable access was available during delivery times and that measures are put in place to allow woodfuel to be delivered safely, given the nature of the buildings and activities which take place within. In any case the woodchip delivery vehicle access will be from a convenient point from the public highway to the open end of the store. Sufficient space should be made available for the vehicle to manoeuvre into position, offload and exit the area safely. 3.2 Central Heat Plant & Enclosure The biomass heating plant will require a new enclosure to be built so as to provide a secure, weatherproof environment for the boiler equipment, fuel store and supporting services. An alternative is to use a pre-fabricated container which houses the boiler and all necessary mechanical and electrical equipment, this can be delivered to site fully assembled ready for connection to fuel feeds, utilities and district heating pipework. Advantages include improved quality control of the assembly of equipment and components within the plant room and potentially improved asset value to an investor as the entire heat supply package can easily be removed from site to serve another project if required. The complete biomass boiler system includes the boiler with twin wall flue, fuel feed mechanism linking the fuel store to the boiler, a buffer tank linking the boiler to the heat supply pipework, heat supply pumps capable of supplying low temperature hot water (LTHW) from the boiler house to the existing heating system connection points, complete mechanical and electrical services linking all items of equipment, and a controls package as major elements. Additional boiler capacity is often included to provide for peak loads and/or full backup capability as required. The alternatives in 19

20 this case are to use any existing local boilers which would be retained or to provide a new boiler located alongside the new biomass unit, fuelled by either heating oil or LPG. Load growth over time may require a smaller capacity boiler to be installed initially to serve the first connected loads, with the addition of a second boiler to deliver additional heat as required. Utility services required for the central boiler plant are a 415V 3-phase electrical supply with a minimum rating of 16A, and mains water at a pressure of between 1.0 and 3.0bar. The biomass boiler is usually sized significantly below the peak heat demand of all connected loads which enables efficient operation at full rated output for a greater number of hours per year via a suitably sized buffer tank which provides control of heat output to follow variations in heat demand throughout the 24 hour period. The buffer tank can combine with the boiler to supply heat at a greater output than the boiler rated output for limited periods if required and can therefore provide for a portion of the peak loads, with the remainder provided by the peak/ backup boiler(s). As a starting point the analysis assumes that the biomass boiler system will supply 95% of the total annual heat demand of the connected loads as detailed above. 3.3 Woodfuel Delivery, Storage & Transfer The fuel storage bunker would be located adjacent to the boiler plant enclosure. The fuel store can be either above or below ground, for a project of this size and type the former being generally simpler and cheaper, the latter more expensive but which allows the greatest number of fuel delivery options and generally straightforward fuel deliveries. It is envisaged that the woodfuel type proposed for this project will be in the form of chip to ensure local supply, and delivered via a tractor-trailer vehicle. An above ground store will require the woodchip to be raised up and delivered in through a roof hatch or opening towards the top of one of the side walls of the store in order to fill the space. This will usually require some form of additional mechanism, usually either a chip blower (integral to the vehicle or a trough-type into which woodchip is tipped), a mobile conveyor, or a front loader vehicle to take woodchip offloaded from the trailer onto a hard standing or from an intermediate bulk store. Alternatively specialist delivery vehicles have been known to be used where available, for example a scissor lift tipping trailer. All of these options require either the use of additional equipment which can be noisy, energy/ labour intensive and time consuming to operate, and/ or requires additional space around the fuel store. The use of a specialist delivery vehicle such as a scissor lift tipping trailer severely limits fuel supplier options. A further alternative to deliver into an above ground store is to take advantage of an existing or a specially constructed bank or ramp against one side of the storage bunker to allow a standard tipping trailer to reverse up and tip under gravity. A fuel store located below ground allows direct unloading of fuel from a standard tipping vehicle under gravity. This method provides the ability to accept fuel deliveries from all standard tipping/ moving floor vehicles, including tractor-trailers 20

21 Brightwalton Wood Fired District Energy Scheme and tipping pick-up vehicles. A waterproof pit would need to be excavated in the area adjacent to the boiler house, with sufficient space allowed to auger fuel from the pit base up and above floor level inside the existing boiler room where the biomass boiler would be located. The pit would need to be ventilated to prevent moisture build-up and fitted with suitable hinged or sliding access doors to protect woodfuel from the weather and to allow efficient deliveries. A biomass boiler to serve a project of this size would make use of a spring arm agitator enclosed by fuel store walls, and a screw feed auger feeding woodfuel through an aperture within the dividing wall between the fuel store and the main boiler house. Vehicle access from the public road to the village hall (left) and school Vehicle access from the public road to the rear of the village hall 21

22 3.4 Woodfuel Delivery & Storage Volumes The woodfuel storage volume within the fuel bunker should be sized to take account of significant demand for heat during a continuous cold spell and normally with consideration given to the likely maximum capacity of woodfuel delivery vehicle available. The fuel bunker should ideally be sized to hold a minimum of two weeks fuel supply during the coldest period of the winter heating season. The size of the potential heat load could conceivably grow in future to take in additional heat connections and the fuel store should be sized with this in mind. Further details of the fuel store and capacity are outlined in the section which follows. Tractor-trailer capacity is typically around 18 cubic metres or 4.5tonnes (assuming woodchip at 30% moisture content). A tipping truck can supply between 5 and 10 cubic metres depending on the size, roughly equivalent to 1.5 to 2.5tonnes. 3.5 Heat Supply & Connections Heat would be delivered from the biomass boiler via the buffer tank as LTHW at around 80deg.C supply temperature and connect into the existing heating systems at the existing boiler connection points in each building via motorised control valves and heat exchangers as heat interface units (HIU). Each end user would be metered to allow billing of heat consumption based on individual use. Space heating and hot water demand is controlled as per existing arrangements through thermostats and timers, with the required quantity of heat delivered to existing heating and hot water distribution systems through the heat exchangers. A new pre-insulated district heating connection (flow and return) buried approximately 0.8m below ground would be required to connect from the central heat supply to the existing heating systems at each local boiler. For heat supply at this scale the district heating pipe will likely be a flexible type. Water return temperature should ideally be as low as possible to give a the largest difference between supply and return temperatures (delta T) as is practical in order to keep pumping volumes low for a given load in kw. This minimises pumping pressure losses and keeps district heating pipe diameters small thus reducing operating as well as capital costs. In this case the operating temperatures of existing heating systems between heating flow and return are expected to be relatively small with a delta T of around 10 or 15deg.C, the district heating system and local heat exchangers will be designed accordingly. The heat losses associated with modern pre-insulated district heating pipework are minimal, a few % of the total annual demand. District heating pipe runs should be routed within soft ground wherever possible so as to minimise the additional cost associated with breaking through areas of tarmac or concrete and making good. The new network would need to avoid all existing buried utility services, the locations of which are not known at the time of writing. No official contact has been made with land owners who may be affected by the proposed routes of district heating pipework and therefore at this stage it has been assumed that access routes understood to be available via a visual inspection can be used, with the exception of private residential land. It is understood that Thames 22

23 Water are owners of land immediately west of the water tower located between social housing nos.1 and 2. Photos of possible access routes for the some of the district heating pipework are shown below. From the rear of village hall, east to heat loads To the main boiler serving the school From the public road to the school From the rear of village hall to social housing Access to social housing no.2 Access from social housing no.1 The district heating pipework routes shown below are illustrative at this stage and subject to further detailed assessment and availability of local access and other constraints. The existing boiler locations for residential properties are for the most part unknown and the termination points of district heating connections shown are therefore approximate. 23

24 Core heat loads showing routes for district heating pipework, final connections and options for location of energy centre Key to the above photo: A Energy centre location Option 1 B Energy centre location Option 2 1 School main boiler 2 School second boiler serving hall 3 Village hall boiler 4 Church boiler Extension 1 & 2 heat loads showing routes for district heating pipework 24

25 Key to the above photo: 5 Social housing no.1 district heating pipework routes 6 Social housing no.2 district heating pipework routes Extension 3 heat loads showing route for district heating pipework main and connections Key to the above photo: 7 District heating pipe main supply to residential connections 8 Individual connections to private dwellings Extension 4 heat loads showing route for district heating pipework main and connections 25

26 Key to the above photo: 9 District heating pipe main supply to residential connections 10 Individual connections to social housing no Project Economics The cost of woodchip is dependent upon many factors. For locally supplied woodchip a figure of 90/tonne would be an approximate market rate for 30% MC woodchip for this application and this is used as the baseline cost within the analysis. The current cost of heating oil is around 55p/litre and this is used as the baseline cost when calculating a heat charge rate to end users. As has been experienced in the past 18 months or so this figure can vary widely, and longer term it is widely expected that the cost of heating oil will be significantly higher than this. Some projections consider a 30% increase over the next 10 years. The Renewable Heat Incentive is expected to be in place by June This is a government funded support mechanism aimed at increasing heat supply from renewable energy sources, the UK s target for renewable heat supply is 12% of the total by Potential revenues arising from the supply of biomass-fuelled heat are based on the rates of support as outlined in the most recent government consultation, minus 20% as an interpretation of the most recent government announcement following the spending review. This translates to a benefit of 5.2p/kWh for heat supplied from a biomass boiler between 45 and 500kW capacity, guaranteed for 15 years. The rate is expected to be confirmed at the beginning of The financial appraisal considers the relative costs of heating oil and woodchip over the short to medium term this would be expected to widen. 26

27 4 ANALYSIS 4.1 Technical Analysis Equipment Sizing & Energy Calculations The following analysis considers the case of biomass heat supply to the various heating connections by group, starting with the core loads and extending to include additional loads. The heat demand figures assume no energy efficiency improvements are carried out to existing buildings nor that some loads are increased, i.e. estimates of current heat demands are used Core Heat Loads Four options as the core heat load are examined in the following analysis, these are: Option 1 Option 2 Option 3 Option 4 School School plus church School plus village hall School plus village hall plus church Energy analysis & boiler plant selection Core scheme option 1 - Existing boilers school Core scheme option 2 - Existing boilers school + church Corescheme option 3 - Existing boilers school + village hall Core scheme option 4 - Existing boilers school + village hall + church Core scheme option 1 heat supply Core scheme option 2 heat supply Corescheme option 3 heat supply Core scheme option 4 heat supply Biomass boiler to supply core option 1 Biomass boiler to supply core option 2 Biomass boiler to supply core option 3 Biomass boiler to supply core option 4 Oil boiler to supply core option 1 Oil boiler to supply core option 2 Oil boiler to supply core option 3 Oil boiler to supply core option 4 Heat supply from biomass core option 1 Heat supply from biomass core option 2 Heat supply from biomass core option 3 Heat supply from biomass core option 4 Heat supply from oil core option 1 Heat supply from oil core option 2 Heat supply from oil core option 3 Heat supply from oil core option 4 Biomass boiler full load operating hours option 1 Biomass boiler full load operating hours option 2 Biomass boiler full load operating hours option 3 Biomass boiler full load operating hours option kw 286 kw 159 kw 339 kw 89,981 kwh/yr 97,479 kwh/yr 107,120 kwh/yr 114,618 kwh/yr 60 kw 60 kw 90 kw 90 kw 100 kw 200 kw 150 kw 200 kw 85,482 kwh/yr 89,981 kwh/yr 101,764 kwh/yr 106,263 kwh/yr 4,499 kwh/yr 7,498 kwh/yr 5,356 kwh/yr 8,355 kwh/yr 1,425 hrs/yr 1,500 hrs/yr 1,131 hrs/yr 1,181 hrs/yr An initial estimate of the size of the biomass boiler is calculated at between 60 and 90kW depending on the combination of core heat loads supplied from the central 27

28 plant. The backup/ peak load fossil-fuelled boiler would require a capacity of between 100 and 200kW. The heat demand figure for each option includes district heating pipework losses of 4% of the total heat demand figures for each building. The amount of heat supplied from the biomass boiler ranges from approximately 85,000 to 106,000kWh/yr. The total amount of heat supplied ranges from approximately 90,000 to just under 115,000kWh/yr. Due to the very low heat load as hot water during summer months the biomass boiler would be switched off at those times. Woodfuel requirements Wood fuel required per year core option 1 Wood fuel required per year core option 2 Wood fuel required per year core option 3 Wood fuel required per year core option 4 MC Wood pellets tonnes cubic metres tonnes cubic metres tonnes cubic metres tonnes cubic metres Depending on the combination of core heat loads supplied, the annual woodchip requirements range from between 30 and 38tonnes per year at 30%MC (between 127 and 158 cubic metres). As a comparison with woodchip, figures for wood pellets show a consumption of between 21 and 27tonnes per year at 30%MC (between 36 and 44 cubic metres). 28

29 Woodfuel consumption rates and storage Wood pellets Estimated peak heat demand option hrs/day at full load Estimated peak heat demand option hrs/day at full load Estimated peak heat demand option hrs/day at full load Estimated peak heat demand option hrs/day at full load Central heat plant seasonal efficiency 85% 85% Maximum woodfuel input rate 60kW boiler kwh/hr at full load kg/hr at full load tonnes/day (peak) cubic m/day Maximum woodfuel input rate 90kW boiler kwh/hr at full load kg/hr at full load tonnes/day (peak) cubic m/day Woodfuel delivery vehicle capacity (estimated) cubic metres tonnes Woodfuel delivery vehicle type tractor/trailer tanker Operation at peak heat demand per delivery (60kW) days Operation at peak heat demand per delivery (90kW) days Approximate number of deliveries required option /yr Approximate number of deliveries required option /yr Approximate number of deliveries required option /yr Approximate number of deliveries required option /yr Height of woodfuel store (minimum) m Internal width of woodfuel store m Internal length of woodfuel store m Internal volume of woodfuel store (gross) cubic metres Estimated usable volume of woodfuel store cubic metres tonnes Operation at peak heat demand (60kW boiler) days Operation at peak heat demand (90kW boiler) days Woodfuel storage is sized using a combination of estimated biomass boiler full load operating hours and the types and capacities of delivery vehicles likely to be used. The maximum daily number of hours of operation of the biomass boiler is not likely to occur for more than 5 days at any one time due to the school and therefore the number of days of operation per woodfuel delivery will be greater than 22 days (60kW boiler) or 15 days (90kW boiler) based on an 18cubic metre (4.3tonnes) capacity tractor trailer vehicle. Deliveries from smaller vehicles such as tipping truck (between 1.5 to 2.5tonnes capacity) for example would require deliveries more frequently during peak heat demand periods. The woodfuel store size allows for a delivery of woodchip from the largest capacity vehicle likely to be used when the store is around one third full. The figures for wood pellets are shown for comparison Extension Heat Loads Four extension heat load options are examined in the following analysis, these are: Extension 1 Social housing no.1 29