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Case Study 1
Type of Building: Boiler Size: Fuel Type:
New build office complex 80kW Chip
This boiler is used in conjunction with solar water heating to provide heating and hot water to an eco friendly building.
Timber from the on site woodlands is used and a trailer mounted chipper is used. An open sided barn is used for primary storage. Chip quality is variable as the chipper is not specifically designed for fuel production. Consequently constant monitoring is required to ensure removal of oversize particles, which would interrupt fuel flow and extinguish the boiler fire.
The controls on the boiler are very simple and do not allow modulation of the output. No automatic ignition is fitted and the fire must be kept in slumber mode if it is to stay alight. Running the boiler with low heat output has resulted in incomplete combustion and formation of tars within the heat exchanger and flue which has to be removed manually.
The manager carries out minor maintenance consisting of periodically scraping the internal fire walls, removing the ash and checking fuel quality. Major servicing is carried out in the summer during the four month summer shutdown.
Case Study 2 Type of Building:
Boiler Size: Fuel Type:
Four storey stone built former mill used by the public. Building insulation complies with Building Regulations 2005 25 kW Pellets
The manager wished to fit an eco friendly heating system on a site with no mains gas. The limited number of dependable alternative fuels indicated biomass as the best choice. The selection, supply and installation of the boiler proved to be easy. However at that time the chosen boiler had a four to five month delivery delay.
Operation of the boiler is simple but requires bags of pellets to be lifted to chest height to load the boiler. The fuel feeds without problems providing the pellets conform to TS 14961 standard. Pellet fuel is delivered in three tonne loads, in 17kg bags, as access to the fuel store and space within it is limited. Fuel consumption is just under 3 kilos per operating hour. The integral fuel hopper is replenished as required, usually weekly. Ash production has been measured at 0.5% by weight of fuel burned.
During the warmer months the boiler is switched off and domestic hot water is supplied from solar panels mounted on the roof of the building.
The boiler is capable of burning grain when fitted with an adapter. Trials of grain firing showed that it required the boiler to be run at constant high load for effective operation. In addition the formation of clinker was a problem as was the corrosion that was caused to the boiler steelwork.
The manager carries out bi-annual cleaning and minor servicing is carried out in house as are twice weekly inspections. Concern was expressed at the dearth of local qualified service engineers for biomass boilers. It was felt that a scheme to provide a service infrastructure will be required in the near future as boiler numbers increase and existing units age.
Case Study 3 Type of Building:
Boiler Size: Fuel Type:
Holiday cottage complex of five buildings and a drying room 120 kW + 1200 litre heat accumulator tank Pellets
Choice of biomass fuel was made purely on economic grounds. Pellets were chosen as it was perceived chip production would need extra equipment, staff and cost. It was also believed space would be required for timber feedstock. The desire to minimise cost resulted in an early load of pellets being unsuitable for the boiler.
They had to be removed by the suppliers. Subsequently it has been discovered that 6mm pellets are the most suitable.
The manager spent a considerable amount of time conducting internet and telephone enquiries to locate equipment and fuel suppliers. Once suppliers had been identified the purchasing process was very easy. Installation of the equipment and training of the manager in its operation was effective. Day to day boiler operation is very easy. The supplier carries out boiler maintenance annually.
The fuel store was timber built from material that was to hand. Serious consideration is being given to installing a silo such as used for animal feed.
Heat is distributed by a heat main, a heavily insulated underground pipe. The boiler output can be modulated and normally runs at less then 50% of maximum output.
Case Study 4 Type of Building:
Boiler Size: Fuel Type:
Holiday cottage complex of eight buildings one of which contains a swimming pool 150kW Chip
150kW of modulating chip boiler capacity was installed to heat a holiday cottage complex of eight buildings one of which contains a swimming pool.
This replaced tank gas which had become prohibitively expensive. Wood chip was chosen as the cheapest form of biomass fuel. Sufficient space is available on site to accommodate delivery vehicles. Low grade timber is brought to site and stored for air drying.
Chipping directly into the primary and secondary stores is carried out by the manager using a hired in tractor and chipper. Chips are transferred from the secondary to the primary store and then into the boiler as required. This transfer, over a distance of approximately eight metres, is effected by an ex sawmill sawdust blower unit.
Wood heating was considered in 2000 when the complex was built but at that time the available equipment was not sophisticated enough. The idea was revived in 2006 with information from the advisors and local companies driven by large increases in gas price. A number of quotes were obtained from which the final system selection was made.
The service level from the suppliers was excellent as is illustrated by the regular telephone checks made to ensure satisfactory equipment performance. Training on boiler management took two hours. The operation of the boiler is quoted as being ‘fool proof’ and very easy to use. Being equipped with self cleaning boiler tubes and automatic ash removal to an external container manual intervention is minimised.
The boiler supplier was called out when the boiler failed to reach operating temperature. Responding the same day they discovered that very wet chip was being burned. Subsequently chip moisture content is checked on a rule of thumb basis to prevent this recurring.
Case Study 5
Type of Building: Multi building residential complex including a swimming pool
Boiler Size: 500kW Fuel Type: Chip
A 500kW chip boiler installed in a new split level boiler house and fuel store. It provides heat to a multi building residential complex including a swimming pool. A heat main is utilised to distribute the heat from the boiler to the various buildings.
Biomass was chosen for several reasons (a) the presence of readily available timber (b) concerns over future fossil fuel availability and (c) an ageing boiler stock combined with the need for an additional boiler. Wood chip fuel was chosen as the most cost effective option.
The choice of the boiler was made after obtaining advice and holding wide ranging discussions. It was based on the cost, ease of use and that the boiler manufacturer also made a fuelwood chipper.
The intention was to chip trees growing on site in addition to buying in timber.
Initially obtaining information was quite difficult. Locating equipment suppliers was also problematic but once the boiler was chosen the purchasing process was very easy.
The level of service was good, even though this was the first boiler of this make to be installed in this country. The British agents together with engineers from the manufacturer carried out the installation. The installers were efficient and knowledgeable. Very little training was required to operate the boiler. The agents are very helpful and easily contacted by telephone.
There were some delays between installation and commissioning. These were mainly due to the time the in-house labour needed to install the heat main. In all other respects it was a very straight forward process.
The operation of the boiler has proved to be very simple with low maintenance and only minor unspecified incidents in operation. At present 80% of the fuel is produced from slabwood which generates a higher proportion of fine particles. The boiler copes with this material without problem. Maintenance is ten minutes greasing every month with an annual service carried out by the agents.
The bin for the auto de-ashing system is emptied twice per year.
Case Study 6
Type of Building: Boiler Size: Fuel Type:
Lightly used public building 25kW Pellets
A 25kW pellet boiler installed in a lightly used public building. Limitations on fuel storage capacity combined with the size of the boiler dictated the choice of fuel. Information was obtained through a local renewable energy advisory service. In addition to the boiler a wind turbine is a backup for the boiler and provides electricity and hot water for the building. At the time of boiler installation the building was insulated to a high standard (unspecified).
No other information was available for this installation.
Case Study 7
Type of building: Boiler Size: Fuel Type:
Community Building 50kW Pellet and Chip
A 50kW pellet boiler with chip option installed in an underground boiler room with an adjacent 10m3 fuel store with rotary agitator to serve new community facility.
Biomass was chosen for both ecological reasons and financial savings. It was seen that chips offered the most cost effective fuel which it was thought could be obtained from local Forestry Commission woodland. A firm of consultants did the research and sourced the boiler.
The boiler had to be in place before construction of the upper parts of the building. Cooperation between the installers and builders was excellent in this respect. On delivery the customer felt that the boiler did not meet the desired specification. Resolution of these differences took some time.
Training was provided for those responsible for boiler operation. It is felt that boiler management is complex with too many controls. Once the boiler came into service it suffered from frequent problems. Examples quoted included electrical faults on the control panel, extinguishing of the fire and the automatic ignition failing to operate, all of which required intervention. To date these problems have not been satisfactorily resolved.
Currently pellet fuel is being used as it was found impractical to load chip into the fuel store. This is due to its small size and location relative to the nearest vehicle access point. No chip has been utilised by the boiler as the store capacity provides only a few days operation during peak load periods. There is no possibility of increasing the size of the fuel store. Fuel is transferred to the store by means of an external hopper and auger which passes though the boiler room and discharges into the top of the fuel store.
A 500 litre heat accumulator was fitted, in practice it has been found that this is too small to satisfy the heat demand and it is estimated by the managers that 2000 litres capacity is required.
Maintenance is done weekly with manual cleaning of the 26 heat exchanger pipes, the ash ways and emptying of the ash tray. Monthly cleaning is a more thorough procedure.
Overall the level of satisfaction is very low
Case Study 8
Type of Building: Boiler Size: Fuel Type:
Detached stone built period property 15kW Pellets
A 15kW pellet boiler of which 7kW is space heating to the ground floor and 8kW is via a back boiler to the central heating system on the first floor of a detached stone built period property. The boiler replaced a multi fuel space heating stove. In another part of the property was a space heater/wet system boiler also multi fuel. These two units worked independently of each other. The new layout comprises of the pellet boiler which can operate solo with a link to the original multi fuel boiler as a backup. A fire run on bottled gas has been retained to provide a further reserve for two of the ground floor rooms.
Pellet fuel was chosen because of limited storage space. Internet research led to an independent supplier of the stove and fuel. In general it was not easy to find information.
Although the manager was eligible for grant aid the complexity of this prevented any application being made.
Initial installation was carried out to a low standard with unnecessary components being included. As a result of this bad design all the heat stored in the accumulator was dissipated through the stove when it was not operating overnight. A local heating engineer subsequently removed the unnecessary equipment and ensured that water flowed correctly through the central heating thus resolving this problem.
There have been few problems with the boiler itself except for some surface paint flaking off after being heated. Internal rust is affecting the firebox when the stove is left cold for a period of time. These problems have been raised with the agent but to date no satisfactory response has been received.
The ash is cleaned every other day as it is distributed around the stove forming a layer against the glass door, only a proportion collecting in the ash pan.
The principle of biomass heating is very much endorsed and although satisfaction with the installation is very low the overall level of satisfaction is high and the manager would be happy to recommend this method of heating.
Using the knowledge gained from this installation any future biomass systems would be sourced from a supplier who had in-house installers. Concerns were raised over future maintenance as there is little expertise among local heating engineers.
Case Study 9
Type of Building: Boiler Size: Fuel Type:
Office complex 30kW Chip
A 30kW chip boiler heating an office complex. Biomass was chosen from a desire to utilise low grade timber in conjunction with the offer of a grant to restore neglected woodlands. Chip fuel was chosen on a cost and availability basis. Initial information was gained through professional contacts but at the time of buying the boiler there were very few on the market at this scale. The initial equipment purchased was designed to burn peat. This proved extremely problematic and failed after one year of use. The current boiler is of the same make and has worked very well.
The boiler is a very simple design, easy to operate but requires manual loading of the 0.5m3 fuel hopper every other day. This is done by means of a bucket which is filled from the adjacent 50m3 capacity fuel store. A number of fuel types have been tried with wood chip being found the most consistent, economical and reliable.
Roundwood and slabwood are bought in and chipped on contract into the main store. This is done annually. Maintenance is carried by the manager. This consists of emptying the ash every three weeks and scraping the heat exchanger monthly. The boiler is nine years old and some components have worn out, these have been replaced by a local blacksmith.
Level of satisfaction is extremely high and the manager would recommend biomass heating and this particular boiler in the right application.
Case Study 10
Type of Building: Boiler Size: Fuel Type:
New stone built office and workshops 50kW Chip
50kW chip boiler incorporated, together with its 10m3 fuel store, into a new stone built office complex with workshops. As woodlands owners, internet research widened their awareness of biomass potential. Wood biomass was chosen for ecological reasons, the relatively remote location and the availability of in-house managed woodland. Chips could be produced and were therefore the first choice as fuel.
The boiler is a prototype installed in 2004 but has not yet been commissioned and no operating manual was available. Initially the suppliers claimed that green wood could be burned successfully in the boiler. While a burn was achieved no usable heat was produced from this fuel as most of the energy was used in drying the next batch of fuel.
Since that time there have been numerous minor problems with a manager stating “anything that could go wrong has”. Currently inspection and overriding of control system is required every 20 minutes if the fire is to remain alight. The boiler supplier has been unable to satisfactorily rectify these problems. Maintenance of the de- ashing and boiler tube cleaning are done manually. Boiler ignition is also a manual task. Maintenance visits are carried out daily.
Biomass is a preferred system of heating and a boiler of another make will shortly be purchased. The level of satisfaction with the current boiler is zero.
Case Study 11
Type of Building: Boiler Size: Fuel Type:
Existing public building 30kW Pellets
An existing public building, insulated to 2008 standards was fitted with a 30kW pellet boiler and 500 litre heat accumulator. At the time of interview the boiler was being installed with an anticipated commissioning date of April/May 2008. No experience had been obtained in operating the boiler.
The installation came about as the result of an energy efficiency study funded by Cumbria Action for Sustainability (CAfS) who were able to offer guidance and access to grant aid for the installation. Grant was obtained from a number of local sources in a very straightforward process. This was in direct contrast to the funds offered by the Low Carbon Buildings Programme which required online spreadsheets and form completion. These were seemingly designed to dissuade all but the most tenacious applicants. Having been accepted for grant aid the time delay before receiving payment was so long that cash flow problems arose in connection with payment of suppliers’ invoices.
Considerable difficulty was experienced in finding an installer who would carry the project risk and over a year was spent before one was located. The small size of the project was probably a factor in that the cost of project insurance cover was disproportionately high. The first registered installer found took some months to provide a site visit and brief quotation. Requests for further information from the management committee went largely unresolved and the installer withdrew his quotation.
Once another and seemingly the only local supplier had been found it took twelve months to obtain a written quote which, when it arrived, was on half a side of A4 paper. Very little ancillary information was offered relating to the boiler and its installation requirements and performance. This part of the pre sales service was felt to be disappointingly poor quality. Again it proved impossible to obtain answers to queries as the supplier claimed to be new to biomass and very busy with other work.
Despite their being only a verbal outline of the system and no opportunity for customer input the desire to fit a biomass boiler led to an order being placed with this company.
The actual installation was carried out efficiently and although some mess and disruption occurred this was only a minor nuisance. The number of pipes required to operate the three zone heating system was unexpectedly large.
Fuel will initially be supplied through the installer and then by shopping around for the best combination of quality, price and service. It is felt that the fuel should be sourced as locally as possible to maintain the low carbon ethos of the project.
Further information has been promised once operating experience has been obtained.
Case Study 12
Type of Building: Boiler Size: Fuel Type:
Farm house 65kW Pellets
A 65kW pellet boiler was purchased independently from the internet after biomass boilers had been seen in operation in Europe. This unit was intended to reduce the labour required to feed existing coal heating units.
The major factor in making the purchase was the price of the boiler; claimed to be significantly less than if it had been bought in the UK. The purchase was relatively straightforward although the only information was electronic and no physical examples of boilers could be found in a showroom.
The installation and commissioning were done by a friend who had experience of conventional boilers. No grants were applied for because of the bureaucracy involved. The boiler is fitted with very basic and simple controls with ignition and extinguishing of the fire being done manually. The makers state the boiler will run on grain and nut shells, the manager is convinced it will also operate on wood chip with which it will be tested in the near future.
It has not been easy to obtain fuel with little or no response to enquiries. There was some blowback of dust from the feed hopper and the unit is noisier than expected. Overall the level of satisfaction is 85%.
Case Study 13
*The information has been gathered during a site visit and not using the standard interview form, it is therefore less complete than the other case studies.
A 150kW chip boiler in a residential educational and leisure facility based in a country house. Originally a 100kW unit was specified but the supplier offered the larger boiler at the same price. This was accepted in good faith without knowing if the heat load required a boiler of this size.
The current manager was not in post at the time of the boiler purchase and therefore was less well informed of the rationale behind the decisions which were taken. The boiler is installed in a former motor house with accommodation on the first floor. The intention was to distribute heat by means of heat mains to the buildings on site. Wood chip was chosen on the ground of economics and the potential to incorporate it with woodland management.
The 15 cu. M. fuel hopper is a preformed steel box mounted on legs and attached to the boiler. It is sighted so that there is insufficient room between the top of the store and the ceiling of the building to permit mechanical loading of fuel. The manager has been told that arranging fuel delivery to the boiler is his responsibility despite the fact he has no experience in this field. The suppliers of the boiler state they have fulfilled their obligations and seem unwilling to provide any further assistance.
The manager understood that the cost quoted for the boiler installation was the total required and budgeted accordingly. Consequently an impasse has been reached where extra fuel handling equipment and storage is necessary if the system is to work but the finance and the expertise required is not available.
Apart from a short test firing after some fuel had been loaded into the fuel store by hand via a hatch low down on one side, the boiler has not been operated since it was installed in 2006.
The satisfaction level is zero.
Case Study 14
*The information has been gathered during site visits and not using the standard interview form, it is therefore less complete than the other case studies.
A dual fuel boiler producing 15kW when burning pellets and 20 kW from logs was installed in a new log cabin boiler house sited next to a detached dwelling. No mains gas was on site and the manager wished to reduce the carbon footprint of the building.
The pellets are delivered in 17 kilogram bags and stored in an existing barn. The boiler is equipped with a fabric fuel store suspended from a steel frame. This has a capacity of about a third of a tonne and is loaded by hand as required.
Fuel was supplied at a very competitive price with the promise that further orders would be met at the same cost. In the event the price rose to uncompetitive levels unless industrial scale volumes of pellets were delivered. A local pellet supplier was located via the internet and fuel was delivered.
Although the proportion of dust and fines were within the recognized limits for the CEN Standard the boiler was unable to cope. This was because the fuel feed was by means of an auger which lifted the pellets from the ready use store and delivered them to the fire box by a gravity drop tube. The fine material did not have sufficient mass to reach the fire box and gradually built up in the tube, blocking it and eventually catching fire. The safety cut out on this boiler was achieved by the feed tube melting and diverting any remaining pellets onto the boiler room floor.
The fuel supplier replaced the problem pellets with those that had been screened to remove almost all the fine particles. No further problems have been reported. Replacement of the drop tube proved problematic with a long delay in obtaining a replacement. As the boiler is dual fuel heat can be generated by loading a second firebox with logs. This is a labour intensive process and negates many of the automatic features of the boiler.
Some concern was expressed over the lack of local service engineers who could supply spare parts rapidly when needed.
The satisfaction level is fairly high as the problems so far are seen as part of establishing new technology.