Blog: Low lifetime costs for biomass boilers: How to get the balance right
By Paul Clark, MD Rural Energy and WHA Director.
Biomass boilers offer a practical and cost effective heating solution, particularly for applications with high heat demands like schools, hospitals, district heating schemes and other public buildings. Drivers such as the Renewable Heat Incentive have helped to make biomass even more appealing – but there is still some uncertainty around the true long-term costs of a biomass system.
Recent evidence has suggested that poor design and installation – and lack of maintenance – contribute significantly towards the lifecycle cost (LCC) of the installation. It’s essential then that some fundamental principles are adhered to when installing a biomass boiler, which will ensure the system performs to its maximum potential throughout the installation life.
Boiler sizing, selection and flue arrangements
There have been reports of some installations sizing the boiler in order to maximise RHI income, but correct boiler selection should always be based on the potential heat demands of the location. For retrofit projects, historical use data is often used to determine this but an appropriate model or simulation can be used when this is not available.
A biomass boiler sized to 50% of the peak demand will normally be able to provide 80-85% of the building’s annual heating needs. Sizing a biomass boiler to 100% of the peak load is unlikely to be a cost-effective strategy, as it will operate at full output for less than 1% of the year.
Fuel choice and storage
Exact requirements vary between boiler manufacturers, models and fuel-feed systems, so it’s important to consult carefully before choosing which type of fuel to use. Pellets require moisture content of <10%, while wood chips can vary between 15% and 40%. Some boilers may be capable of burning wetter fuels, but the efficiency can drop substantially.
Fuel storage should also be considered as bulk deliveries are often more cost effective meaning a larger fuel store could reduce long-term costs. Think about how the fuel will be fed into the system too – vertical augers for example will require a power supply that can greatly increase electrical consumption, therefore adding to the cost of fuel.
The hydraulic design is a major factor ensuring a high level of system efficiency and fuel usage. The design should take into account the specific requirements from the manufacturer, as well as relevant industry standards. Specifying the correct equipment can greatly affect the operational costs of the system. Components should be selected not only to be safe and fit for purpose, but also to reduce associated electrical loads for example under sizing pipes Creates a high pressure drop and requires higher pumping duty resulting in a higher electrical consumption. All pipes and stores must be insulated as well of course.
Remote system monitoring can be used pre-emptively to address issues and enable preventative maintenance programmes to maintain performance. A useful monitoring system is able to track the fuel used, as well as the heat produced by the boiler and delivered to each separate load, both allowing heat demand to be tracked and areas of concern to be identified. Being able to access and control the boiler remotely can expedite the identification of faults and potentially allow these to be corrected without having to call out a site technician.
Biomass boilers require weekly checks and cleaning by the operator to maintain efficiency. If there is no one available on site, this may need to be delivered through a service contract, therefore all cost projections should take into account the expense of servicing and maintaining the biomass system. Suppliers should be able to provide an idea of typical costs or replacement parts that may be required. Some boiler manufacturers also offer five, 10 or 20-year maintenance warranties on their products, which eliminate the unknown cost of call-outs and repairs for the main lifetime of the heating plant.
A well designed, operated and maintained biomass heating system can provide a high level of system efficiency. It will require increased initial planning and investment, and will achieve very good comparative lifecycle costs when it is used in conjunction with the RHI. The owner and operator play a key role in the process, and must be included in the development and application of the system. Along with clear written guidance and training, they are vital for effective biomass system commissioning, handover and lifetime operation.
Note: The Board of Directors of the WHA will each month publish a blog on topics related to the biomass heating industry. The views expressed in this blog post are those of the author(s) and do not necessarily reflect the views or policies of the WHA/REA.