2 The sole responsibility for the content of this presentation lies with the authors. It does not necessarily reflect the opinion of the European Union. the European Commission is not responsible for any use that may be made of the information contained therein
3 What is Woodheat Solutions? AIM: Inspire investment in wood-based heat generation from under managed woodlands in England, Croatia and Slovenia drawing on the experience gained in Finland and Austria.TIMEFRAME: 1 October 2008 to 31st March 2011Project Partners:Slovenian Forestry InstituteStyrian Chamber of Agriculture and ForestryTechnical Research Centre of Finland
4 Starting point and objectives Increasing concerns about climate change and energy securityLots of undermanaged woodlandRestoring sensitive woodland management delivers other benefits too, including jobs and biodiversityObjectives:Increase the number of woodheat projects in Slovenia, Croatia and the UK (15MW installed capacity)Facilitate the development of 10 major bio-heat projects in Slovenia, Croatia and the UKIncrease the area of actively managed, privately owned woodland in Slovenia, Croatia and the UK ((4,500 ha)Raise the profile of CEN TS/335 standards amongst woodfuel suppliers and end usersRaise the profile of woodheat projects amongst the general public, public sector decision makers, foresters and farmers
5 Approach - in a nutshell! Engagement: Identify and build relationships with key decision makers able to facilitate the establishment of woodheat projects in Croatia, Slovenia and the UKStudy tours: Identify a range of successful woodheat projects in Finland and Austria and use these to host study tours for key decision makersBest Practice: Develop regional guidance adapted from knowledge and experience gained in Finland and AustriaStandards: Summarise and disseminate CEN TS/335 technical standards and highlight the importance of quality control during woodheat production.Training: Develop courses and materials for all those potentially involved in the woodheat supply chain
6 Contrasting resources and population pressure Partner countriesCountryForestArea(millionhectares)Total landmass%Population(million)Finland23.03075%5.3Austria3.9847%8.3Slovenia1.2258%2.0Croatia2.75.742%4.5South EastEngland0.271.914%(plus 7.5 inLondon)1.1138%51.0UK3.02412%61.2EU (27)157.041937%497.6
7 Indicative targetsSlovenia, Croatia and England have significant resources of wood which is currently unharvested which could be used as woodfuel. Current plans are for:Croatia: to triple use of biomass by 2030, which equates to an increase of > 2,000,0000m3 per yearEngland: to bring an extra 2,000,000m3 from currently undermanaged woods to the market by 2020, with at least 500,000m3 coming from SE EnglandSlovenia: estimates the production of woody biomass could be increased by at least 1,600,000m3
8 Cultural differences: Austria and Finland have very strong cultures of wooduse and woodland management – it is exceptional to see woods which are not actively managedSlovenia and Croatia also have strong wood culture though the levels of technical development of wood use are not as well developed.Part of the reason may be the high proportion of forest cover and resource relative to population:CountryFinlandAustriaSloveniaCroatiaEngland% forest cover75%47%58%42%8%Area of woodland per person (ha)18.104.22.168.02
9 Cultural differences: In England the wood culture is very different with:Most woods not being actively managed;A population which has lost touch with wooduse, who are not used to seeing managed woods and many of whom believe felling trees is bad for the environment.
10 Woodland Ownership:Woodland ownership affects woodland culture and ability to adapt:In Austria and Finland many people own woods but the area of ownership may be very small;In Slovenia there have been major changes from state to private ownership in recent yearsIn Croatia the majority (80%) of woods are owned by the stateIn England most woods are privately owned but while there are many woodland owners most of the woodland area is linked to estates or farms. (Woodland ownership has not been broken down into very small plots through inheritance as in Austria)
11 Concerns about the evolving use of wood as a fuel As individual countries we’re all working hard to improve and make better use of our woodland resources and sharing experience between countries helps encourage lateral thought about how we can achieve our aims;However, there are concerns from some woodland owners and wood based businesses that the market for wood as a fuel will:compete for resources, increase raw material costs and endanger existing businesses; anduse wood which would be better used as timber;– particularly where the woodheat (and wood power) industry receives grant support.
12 High technology developments of woodfuel use in Austria Current situation?Most woods in Austria and Finland are actively managedHigh technology developments of woodfuel use in AustriaPragmatic technology developments of large scale woodfuel use in FinlandIn some countries we have an embedded culture of woodland management;An understanding of the importance of seasoning wood before using as fuel; andWell established, and continually evolving, technology to make best use of wood as a sustainable source of fuelThere is an embedded culture of woodfuel use both for domestic and community heating
13 Current situation: Didcot Power Station Many woods in SE England have not been actively managed for decades, mainly due to loss of markets for wood productsBefore the industrial revolution woods provided many of the materials we needed including building materials, tools and fuel. At that time many woods were intensively but sensitively managed.The increased use of fossil fuel derived products has led to a gradual reduction in the value of woodland products and the subsequent reduction in active management of most of the woods in the SEThe lack of management reduces the diversity of habitats within the woods and adversely affects our native plants and animals.Using wood as a renewable fuel provides a market for the lower grade wood and will hopefully allow us to re-establish active and sensitve woodland management in many of these woods.Didcot Power StationThere is also a general energy culture based around large scale and centralised power stations
15 High silvicultural standards A ‘can do’ culture A long term view Everything is managedHigh silvicultural standardsA ‘can do’ cultureA long term viewCommunityProfessionalism
16 District heating is common Central woodheat plant a Toivakka provides heat through a heat main to properties in the centre of the village
17 Woodfuel receptionWoodfuel is delivered into a large barn (large capacity allows for extreme conditions when fuel delivery would be impossible).Walking floor moves fuel left to right &Large capacity augers deliver woodchips to boilerWhole system is robust and built to last
18 Chip store to boilerLarge capacity augers, less prone to jamming and long lastingWoodchip quality, included more shades and fines than seen in Austria BUT system was designed to cope
19 Wet ash disposal systems were the norm BoilersWet ash disposal systems were the normBoilers tended to be large in size (compared to Austrian equivalent) but were running at high load for long periods in winter
20 Whole system of wood to warmth complements to situation Why?Very cold winters mean that significant amounts of heat are needed for extended periods;While in southern Europe failure of the boiler might be inconvenient in Finland it could be life threatening;Whole system of wood to warmth complements to situation
21 Woodfuel harvestingFuel for local woodheat systems was often derived from subsidised first thinning operations designed to improve the quality of the retained timber trees.Usually highly mechanised modern harvesters possible due to terrain and low density of retained trees but also motor manual
22 Don’t burn water!When trees are first felled they are approx. 50% water (by overall weight). Seasoning for a year will normally reduce this to 30%. Energy value increases by about 8%Often whole trees are used for woodfuel, but rigorously seasoned. Waterproof paper helps prevent rewetting through snow melt
23 Use the whole resourceSophisticated specialist machinery is used for contract chipping.‘Giant’ chipper in operation chipping seasoned whole trees derived from first thinnings. Loading woodchips directly into walking floor lorry (and trailer) for delivery to local woodheat plant
24 Make use of existing equipment Local scale woodchip production (again using whole trees).Note use of:agricultural tractorSilage/corn trailerWoodchiper powered by tractor
25 InnovateDelivery of woodchips using simple (chain driven) walking floor lorry in Finland.Walking floor chip store allows easy access for a range of delivery vehicles and has large capacity
26 Consider fitting hydraulics to the roof so that it lifts vertical! InnovateHaving difficulty building a woodchip bunker which is versatile enough to allow delivery by a range of tipping trailers?Consider fitting hydraulics to the roof so that it lifts vertical!
27 Pay for energyWeight and moisture content have the greatest impact on energy value. Test energy value using domestic scales and oven
28 Engage the local community Forestry training starts early in Finland!Local children learning how their classroom is kept warm
29 Overall message:There are major opportunities for entrepreneurial woodland owners and rural businesses to add value to low quality wood by converting it into the much more valuable heat.Particularly if this can be carried out locally using existing resources
30 Consider the latest technology Compact harvester head with tracked rollers well suited broadleaf and even coppiceFinnish technology introduced to England:(Valtra tractor, Botex 8m boom and Keto harvester head.) Versatile and well suited to small woods with high environmental sensitivity
31 In Austria Hillier – making woodland management more challenging High technology development of woodheat systemsMore people and less woodland per person(but still a lot compared to England!)
32 Local woodheat for the community Local farmers sell woodheat to the villagers of Straden:Boiler house is built into the hillsideChip store takes advantage of the landform to allow easy delivery by tipping trailer;Large accumulator tank to optimise boiler efficiency; andSolar thermal panels provide heat in summer
33 Agitator arms to push woodchips to auger feed for boilers Woodheat for SchoolsLocal farmers sell woodheat to local primary & secondary schools:Rent basement rooms and install:Fuel bunker, andTwo woodfuel boilers (providing flexibility to address varied load while maintaining optimal boiler efficiency)Note: Farmers are not planning further developments as this system uses all the wood they produce from their own woods, if they had to buy woodfuel on the open market the business model would be less attractiveAccess to chip bunkerAgitator arms to push woodchips to auger feed for boilers
34 High technology Mobile high capacity woodchipping from Komptech System has both shute and elevator delivery of woodchips. Elevator is more energy efficient, quieter and could be fitted to a woodchip delivery vehicle to allow easy delivery to above ground chip stores
35 And for that oversized log! If there is the odd large log which is no use as timberIt can be made smaller to fit the chipper!
36 Ventilated floor of chip store Woodfuel retailThe concept of the ‘Biomass Trade Centre’ is an effective way to store, dry and retail a range of woodfuel typesHere wood is seasoned over a summer reducing moisture content from 50% to about 30% (by overall weight) in the open air and chipped (as illustrated in previous slides) by a contract chipper.If a lower moisture content is needed then ambient air can be blown through the woodchip store via a vented floorVentilated floor of chip storeVentilating fan
37 Woodchip deliveryIdeally woodchips will be delivered using a ‘tipping trailer’ (as this keeps costs down). However, for those sites where access to the chip bunker is restricted woodchips can be delivered pnuematically. But this is noisy, time consuming and costly – so void if you can!
38 Key lessons: Add value by selling heat if you can. You may be your best customer: If you are paying increasing amounts for oil or gas to heat your home and/or business premises and have your own woodland (or even if you have land to plant a new wood) then you could use your own wood to supply your own needs. In doing so you also gain experience and credibility as a Woodheat supplier which could be used to sell heat to others.Look for opportunities on your doorstep: Owners of neighbouring properties may be very interested in someone local, and trusted, supplying their heat needs at a competitive rateShort supply chains benefits both supplier and buyer: removal of the need for a lorry to transport the fuel usually allows the supplier to offer a better than open market price to the customer but gets a better price too (due to reduced costs) – effectively a ‘win-win’ opportunity;
39 Key lessons: (continued) Woodheat benefits long term contracts: Many potential buyers raise concerns about the security of woodfuel supply if woodheat becomes popular (a particularly strong concern in UK where the wood resource is less than other EU countries and the population is much higher). There are major opportunities for local woodland owners to enter long term supply contracts and benefit both buyer and supplier with short supply chains.Consider the long term: heat production and distribution equipment may last 50 years or more. For instance the woodfuelled heating system at West Dean, in West Sussex, England, has been operating for nearly 30 years and the first boiler has only just been replaced! The associated infrastructure which equated to the higher proportion of system installation costs remains!Consider the whole ‘wood to warmth’ system: Every site and supply chain is different so reflect on the whole system to ensure it is practically and financially viable – if it doesn’t look right it probably isn’t!
40 Key lessons: (continued) Ensure everyone is talking the same ‘language’: There are very real opportunities for confusion in relation to volume of wood needed (solid vs loose woodchips), moisture content (by overall weight or dry weight) and energy value. Bring everyone together who is in any way involved in the process: buyer, onsite maintainer, system designer/architect, woodfuel supplier, delivery driver etc, together on site at an early point in the design stage and work through each element of the supply chain with them. It is very easy for simple omissions to have huge consequences – for instance we are aware of a superbly designed Woodheat system where the delivery vehicle wouldn’t fit through the site gate!Mutual respect: Woodheat is a long term business. Anyone looking for ‘quick wins’ at the expense of others is unlikely to survive the long term. Look for opportunities where the buyer and supplier can proceed with mutual respect and a long term vision.Clear, and fair, contracts: Make sure all elements of the woodheat contract are clear and fair. It is likely that some link to long term trends in fossil fuel prices is appropriate but it also needs to reflect fairness and avoid short term fluctuations as we have seen with fossil fuel prices.
42 Why do we need standards? To strengthen trust in wood as a fuel to facilitate trade between consumers and producersTo encourage the best use of a sustainable resource:To harvest it sustainably;To use it most efficiently,in both carbon and financial terms;To reduce negative impacts.To make life easier for buyers and suppliers by:Ensuring the fuel is suited to the boiler;Helping fuel buyers specify their requirements clearly;Helping suppliers know what is needed and how to check that their product meets the requirements;Helping identify problems; andProviding confidence in a growing market.
43 So what’s the problem? Standards are often perceived as: Bureaucratic ComplexTelling professionals what they know already!Providing little benefit to the person who has to do all the workLanguage – use of different measurements for the same thing:Moisture Content – water content vs wood humidityWeight – wet vs seasoned (30%, 20%?) vs oven dryVolume – solid m3, stacked m3, loose m3 (logs or chips)Calorific value – Kilowatt hours, kilojoules, BTU’s (British Thermal Units)?Carbon – or CO2Competition – litres, tonnes, kilowatt hoursPrice - Weight, volume or kilowatt hrs?Cost:Time and moneyScale:Industrial, local or somewhere between?
44 So how could we address these problems and turn theory into reality?
45 Make it simple: Focus on the direct benefits to the individual Provide information:in ‘bite size’ piecesWith the critical elements first‘Flick and dip’ – i.e. information which can be skimmed through quickly but dipped into for relevant details as requiredIllustrate with pictures, diagrams, examples and keep text as short as possible
46 CEN StandardsEU member states where woodfuel use is well established have developed national standards for woodfuel quality, such as ONORM in Austria.With increasing trade in woodheat technology and woodfuel between member states, and beyond, it became clear that an EU standard would be helpful.Approximately 12 years ago the European Union commissioned the Comité Européen de Normalisation (CEN) (the European Committee for Standardisation) to develop standards for solid biofuels.Subsequently CEN established Technical Committee 335 – Solid biofuels, which covers woody biomass, including wood from forests, plantations and landscape management.TC/335 then created a suite of interconnected technical standards (TS) defining terminology, specification, fuel quality assurance (FQA), sampling and the range of tests required to quantify fuel properties.Over time the CEN/TSs for solid biofuels are being revised and upgraded to Euro Norms ENs) displacing all other national standards across the EU (eg ONORM & DIN). They are also being used as the basis for new ISO standards (ISO/TC 238).
47 Key woodfuel parameters: Moisture content – because water doesn’t burn!Dimensions – to make sure it fits the appliance and its fuel handling systemOrigin – where does it come from and what does it consist ofAsh content, andEnergy valueOther parameters may also need to be given for specific types of woodfuel, but these are the key ones.
48 CEN StandardsAlthough at first sight the CEN standards may appear large and complex, the key parts any fuel supplier, or buyer, actually needs to know in detail are usually pretty small.The standards fall into three basic types:Descriptions and definitions:Fuel specifications and classesTerminology, definitions and descriptionsHow different parameters are determined, e.g.:Moisture contentParticle size distribution (e.g. chip size range)Calorific valueAsh content and propertiesMechanical durability of pelletsBut also:How representative sampling should be undertaken for testingConversion of analyses to different basesHow fuel quality is monitored and maintained through the supply chain
49 List of CEN Standards Descriptions and definitions BS EN 14961-1:2010 Fuel specifications and classes – Part 1: General requirementsPrENFuel specifications and classes – Part 2: Wood pellets for non-industrial usePrENFuel specifications and classes – Part 3: Wood briquettes for non-industrial usePrENFuel specifications and classes – Part 4: Wood chips for non-industrial useEN :2011Fuel specifications and classes – Part 5: Firewood for non-industrial usePrENFuel specifications and classes – Part 6: Non-woody pellets for non-industrial useEN 14588:2010Terminology, definitions and descriptions
50 List of CEN Standards (Continued) Measurement of parametersBS EN :2009Determination of moisture content – Part 1: Oven dry method. Total moisture – Reference methodBS EN :2009Determination of moisture content – Part 2: Oven dry method. Total moisture –Simplified methodBS EN :2009Determination of moisture content – Part 3: Oven dry method. Moisture in general analysis sampleBS EN 14775:2009Determination of ash contentBS EN 14918:2009Determination of calorific valueBS EN 15103:2009Determination of bulk densityBS EN 15148:2009Determination of the content of volatile matterBS EN :2009Determination of the mechanical durability of pellets and briquettes- Part1: PelletsEN 15104:2011Determination of total content of carbon, hydrogen and nitrogen - Instrumental methodsEN 15105:201Methods for determination of the water soluble content of chloride, sodium and potassiumEN :2010Methods for the determination of particle size distribution - Part 1: Oscillating screen method using sieve apertures of 3,15 mm and aboveEN :2010Methods for the determination of particle size distribution - Part 2: Vibrating screen method using sieve apertures of 3,15 mm and belowCEN/TS :2006Methods for the determination of particle size distribution - Part 3: Rotary screen methodCEN/TS 15150:2005Methods for the determination of particle densityEN 15289:2011Determination of total content of sulphur and chlorineEN 15290:2011Determination of major elementsEN 15297:2011Determination of minor elementsCEN/TS 15370:2006Method for the determination of ash melting behaviour – Part 1: Characteristic temperatures method
51 List of CEN Standards (Continued) Methods for samplingCEN/TS :2005Sampling – Part 1: Methods for samplingCEN/TS :2005Sampling – Part 2: Methods for sampling particulate matter transported in lorriesCEN/TS 14779:2005Sampling – Methods for preparing sampling plans and sampling certificatesConversion of resultsEN 15296:2011Calculation of analyses to different basesQuality assuranceEN :2011Fuel quality assurance – Part 1: General requirementsPrEN :2010Fuel quality assurance – Part 2: Wood pellets for non-industrial usePrEN :2010Fuel quality assurance – Part 3: Wood briquettes for non-industrial usePrEN :2010Fuel quality assurance – Part 4: Wood chips for non-industrial usePrEN :2010Fuel quality assurance – Part 5: Firewood for non-industrial usePrEN :2010Fuel quality assurance – Part 6: Non-woody pellets for non-industrial use
52 Descriptions and definitions OriginThe origin works on a hierarchical basis based on four main groups:Woody biomassHerbaceous biomassFruit biomassBlends and mixturesEach of these groups is then further divided into 2 to 4 sub-groups, and each of these is further divided and divided again down to four levels of detail. For instance:
53 Woodchip dimensionsCEN standards use simple calibrated sieves to assess the composition of particular samplesA common specification is likely to be P16 and this will comprise:75% of the total volume of woodchips being between 3.15mm and 16mm;Less than 12% of the total volume of woodchips will be less than 3.15mm in size; andFor P16A no more than 3% will be more than 16mm and all will be less than 31.5mm; OR for P16B no more than 3% will be more than 45mm and all will be less than 120mm
54 Moisture and ash Moisture content Specified in terms of the maximum moisture content (by proportion of overall weight)Hence an M35 woodchip would be 35% water, or less, and an M25 woodchip would be 25% water, or less.Ash content:Specified in terms of a proportion of the dry weight of the wood.Hence an A0.7 woodchip would produce no more than 0.7% of its’ dry weight as ash if burnt efficientlyHow much water – 50%
55 Other characteristics: In addition the standard provides a simple way for suppliers to describe other characteristics of the woodchips, which may be of interest to the buyer. For instance:In a N0.5 woodchip there will be no more than 0.5% nitrogen (as a proportion of its dry weight);In a Cl0.03 woodchip there will be no more than 0.03% chlorine (as a proportion of its dry weight);A Q3.5kWh/kg woodchip will deliver approximately 3.5kWh of energy per kilogram (based on 30% moisture content)An E800kWh/m3 woodchip will deliver 800kWh of energy for each loose cubic meter of woodchips; VERY VALUABLEA BD300 woodchip will have a bulk density of at least 300 kg per cubic meter of loose woodchipsAsh melting point is described simply as the temperature in ºC at which the ash starts to melt.
56 CEN Standards made easy To help buyers and suppliers understand and appreciate the value of the standards we have produced:WhS Introduction to woodfuel standards;WhS Summary of woodfuel standards;WhS Roadmap to implementing standards; andWhS Guide to moisture testingAll are available on the WhS websiteand the Roadmap is available in hard copy
57 Key lessonsWoodfuel quality is essential to reduce costs and emissions;Woodfuel standards reduce the chances of confusion by providing a ‘common language’;CEN standards cover a wide range of issues and hence can appear complex to users, however, the principles are relatively straight forward;It’s crucial that CEN standards are presented in easy to understand ways;Quality applies to the overall system, not just the fuel; andQuality standards are more about establishing a culture of quality standards than a bureaucracy i.e. a situation where all those involved in woodfuel supply understand the aspects of woodfuel quality and produce quality fuel as a matter of course.
58 Designing a woodheat system Key issues to consider when designing your woodheat system
59 Common problems with woodheat installations: Oversized boiler: runs inefficiently, often leads to condensation when boiler is not running which damages the internal components = higher cost of maintenance and fuel and higher emissions;Poorly sized, located or designed woodchip bunkerage: increased costs of fuel delivery and inconvenience;Jamming woodchip feed systems: augers can be jammed by poor quality woodchips (containing ‘slivers’) = increased maintenance costs and inconvenience.
60 Identify the heat load and profile Explore opportunities to save energy first - better insulation etc;Have a formal heat load assessment undertaken by a qualified assessor (s/he will be able to assess the actual heat losses from particular building types and sizes);As a starter look at what energy you’re currently using (most utility bills will provide an indication of how many kWh’s of energy (as gas, oil or electricity) you have used)
62 Accumulator tanks are crucial Woodfuelled boilers tend to work most efficiently when they are working at a high proportion of their maximum capacity; andAn accumulator tank is purely a large, highly insulated, hot water tank which stores heat when you don’t need it – very like a rechargeable battery.For example:Domestic accumulator drawing heat from a wood burning stove and solar thermal array, with electric emersion coils for frost protection when owner is away in winter‘Large’ accumulator working with a 250kW boiler to heat a former stately home (or ‘schloss’)Accumulator (left rear) linked to a 100kW boiler (right centre) to provide heat for a community building
64 Two ways to use the accumulator To maintain a constant load on the boiler: in this approach the boiler runs at a constant load supplying heat directly to the user and when this is not needed direct to the accumulator. Maximum required load is supplied by the boiler and accumulator in tandem.To ‘buffer’ the heat demand: in this approach all heat demand from the user is supplied from the accumulator. The woodfuelled boiler runs intermittently to maintain heat stored in the accumulator. This approach works very well with log burning batch boilers where the system relies on only running the boiler for part of the day (i.e. on one ‘batch’ of logs). When used with pellet or woodchip boilers it is important to ensure that the boiler is not switching on and off regularly (one or two ‘burns’ per day is reasonable) otherwise energy will be wasted heating up the infrastructure of the boiler itself. In addition the boiler should be running for as long as possible so that it is running at maximum efficiency for the highest proportion of its’ ‘burn’.
65 Can you link with other heat sources Consider whether other heat sources can be included in the overall system to optimize efficiency of Woodheat:There may be existing fossil fuelled boilers on the site which could be used to provide heat during periods of low or high load, thus allowing your woodfuel boiler to be utilised at optimal efficiency. Hence determine whether:There is a ‘base load’ of demand which is constant throughout the year which could be supplied by the woodfuel boiler?There an constant load that could be supplied by the woodfuelled boiler through autumn, winter and spring? Peak load in winter and low summer load could be supplied by an existing oil or gas boiler running in parallel to the woodfuel boiler.
66 Identify the size of the boiler Depends on:The overall heat load;The heat profile;How well this can be ‘smoothed out’ with an accumulator;Whether there are other heat sources (e.g. oil, gas or solar) which can be linked into the networkHowever, as a ‘rule of thumb’ the capacity of the woodfuel boiler will be about 70% of the equivalent oil or gas system (oil and gas systems respond much better to lower loads than woodfuelled boilers)Some modern woodfuelled boilers can cope better with a varied load but generally operate more efficiently when running at high load.
67 Decide on the woodfuel type Conventional logs work well in batch boilers but usually require manual loading;Woodchip systems are more suited to large heat requirements but require space and a well thought out supply chain; andWood pellet systems require less space, offer great convenience but are difficult to fuel from your own woods.
68 Consider the size of the fuel ‘bunker’ - especially for woodchips Heat load: Woodchips need lots of space as loose woodchips may contain as little as 500kWh’s per loose cubic metre.Buffer required between deliveries: for instance in winter how long do you need to ‘run’ between fuel deliveries.Method of delivery: Delivery of a full load of woodchips will be cheaper than part loads and tipper lorry/trailers are cheaper than blower systems.Avoid ‘just in time’ constraints: The bunker should be large enough to hold at least 1.5 times as much volume as the largest delivery vehicle.
69 Woodchip bunker size (continued) Usable capacity of a woodchip bunker: Woodchips don’t flow (like sand or wood pellets) so it’s very difficult to fill the whole volume capacity of the chip bunker. For bunkers where the woodchips will be ‘tipped’ from a lorry, farm trailer or telehandler tipping into the centre of the pit will ensure much more of the overall volume of the pit is usable than tipping at one side.Access doors for tipping woodchips into bunker are sited in the centre of the bunkerAllows the delivery to drop into the centre of the bunker, keeping the unused space to the minimum
70 Access to bunkerEnsure that the delivery vehicles you are likely to use can access the bunker easily.Example: Surrey University Sports Centre: Access is well designed and ‘marked’ to discourage inadvertent parking, thus allowing easy delivery of woodchips from a local estate using existing farm equipment
71 Location of the fuel ‘bunker’ This is often a compromise but requires careful assessment of the issues:Boiler location: the bunker needs to be adjacent to the boiler BUT as it is easier to transport heat through a hot water pipe than woodchips the mode of supply may have a greater influence on the location of the boiler than the property being heated!Landform: Fully sunken woodchip bunkers offer great flexibility but are expensive to construct and maintain (plus they may be vulnerable to flooding). Semi-sunken systems taking advantage of sloping ground, or even man made landform, can be far more cost effective. Hence if you have landform – use it!Delivery method: The more flexible the system the greater the choice of woodfuel supplier, hence if a bunker can be accessed easily by a tipping articulated lorry then it can also be accessed by tractor trailer etc. However, the capacity of the store needs to be at least 1.5 times the capacity of the biggest delivery vehicle (as delivering part loads from tipping systems doesn’t work well!
72 Woodfuel supply chainWoodchip quality depends on the boiler specification and visa versa - AGAIN this is an area where a careful compromise needs to be struck between what might be optimal for a boiler and what quality of woodfuel is available:Higher efficiency boilers often need a higher woodfuel specification, be careful that the added efficiency doesn’t increase the woodfuel production costs to a degree that the overall cost efficiency of the system suffers!If you have lots of small wood which would produce woodchips with a high proportion of fines you may decide to use a more robust but less efficient boiler which can cope with this lower quality and lower cost fuel!
73 Woodchip quality – critical elements Moisture content:Seasoning of the wood is critical and this depends on location and aspect: an open sunny and windy location without shade and a generally dry summer season is ideal, this should allow moisture to reduce from about 50% to 30%. A lower moisture content will require an extended period or forced drying.Chip size distribution:Use a high quality woodchipper designed for producing woodchip fuel; orUse mechanical screens to ‘refine’ lower quality woodchips – as might be produced from arboricultural operations;andUse a set of calibrated sieves as recommended in the CEN Standards to check that you are producing these to the agreed specification.
74 Who will maintain the system? Woodchip boilers generally require a small amount of maintenance, removal of dust from sensors and removal of blockages from the feed system. The person who will carry out this work must be identified and ‘enthused’ about what s/he needs to do.Lack of simple maintenance is a common cause of problems when woodheat systems are first installed – make sure you know what is needed and that the maintainer is doing it!
75 Example: Rodborough School, Surrey Rodborough School illustrates a common situation in many English schools – as new buildings have been built they have each incorporated their own discrete heating system.Surrey CC were considering replacing the two oil boilers shown in the first photo. While possible, with a degree of difficulty a review of the whole site reveals a whole series of discrete boiler installations, each of which requires servicing and in due course replacing!WhS advised on proposals to replace failing oil boilers.Discovered many different boilers heating individual buildings on site
76 Recommendation: Rodborough School, Surrey Install a heat main to link all buildings on siteBuild a new woodheat boilerhouse and woodchip bunker at an easily accessible point to allow easy deliveryLink ‘bank’ of gas boilers to network to provide summer load and add overall capacity for winter peak load allowing woodheat boiler to run at optimal efficiency and supply 80% of the overall heatIdeally a good solution would be to:(a) Join up the heating systems for the whole site using a heat main (as shown in red);(b) Build a new boiler house to encompass:a woodchip fuelled boiler,accumulator tank,chip bunkerage - locate in a part of the site which allows easy access for fuel delivery away from students and which allows delivery by farm tractor/trailer (provides high degree of flexibility), andsolar thermal array (to deliver summer heat load – especially for swimming pool;(c) Link the existing ‘bank’ of 5 gas fuelled boilers into the heat main to provide peak winter heat load as well as ‘back up’ and summer load.This approach allows the woodfuelled system to run at maximum efficiency and if required would allow the Council to tender for an Energy Supply Company to build the boiler house etc and sell heat to the network. Council retains access to gas based boilers to avoid being ‘held to ransom’! Ideally looking for a v local fuel supplier, and linking the school, curriculum to the management of the woods concerned.
77 A typical opportunity?This is a Forestry Commission site where woodheat is being considered. We are preparing detailed specifications for the options available which we will make public to help others considering woodfuel consider the practical issues they need to consider
78 Overall ConclusionsThere is a significant amount of underutilised woody biomass resource available in Slovenian, Croatian and UK woodlands;Woodheat offers a highly carbon efficient source of heat – particularly when used locally;Woodheat offers a major opportunity for many rural businesses across Europe;The culture and principles of using wood efficiently are less well embedded in some countries;Standards are essential to provide a common language but delivery of quality woodfuel requires us to build understanding and embed a culture of quality management;Woodheat quality must embrace the whole ‘wood to warmth’ supply chain;The use of wood as a fuel source requires the forestry community to consider wood in terms of carbon and energy as well as volume and timber;Woodheat is slowly developing in Slovenia, Croatia and the UK and as more systems are installed this will increase in pace; andOngoing technical and financial support and encouragement will help establish an efficient and effective Woodheat industry.