Following the launch of the Renewable Heat Incentive (RHI) and with a large number of biomass technologies available on the UK market, Gordon Traill of leading UK biomass boiler company Treco will discuss key aspects to consider when specifying a modern biomass boiler system.
When in the early stages of specifying a biomass boiler system, it is important to consider design, fuel flexibility, efficiency levels and ease of use.
The design aspect is key and covers a number of different areas. It is important to understand the end user’s requirements to ensure that biomass is a suitable fit for their needs. Some end users enjoy a high level of involvement, manually loading fuel, but some may not have the time or the ability and this may necessitate a high level of automation so they only need to empty the ash bin.
A good first step during the initial survey is to ensure that the space available on site is suitable for the preferred biomass fuel type. For instance, wood chips have a lower density than pellets, so will require more space for storage. Deliveries will usually be several tonnes at a time, so there must be suitable access for large vehicles to park close enough to the fuel store and adequate space for the vehicle to turn. Is there enough room for a boiler and fuel store in an existing boiler house or outbuilding that could be converted or is a bespoke, purpose-built boiler house the better option?
The choice of fuel type does not have to mean the client is tied into one specific biomass fuel. A number of biomass boilers on the UK market are “multi-fuel” and can burn a wide variety of fuel types including wood chips, wood pellets and miscanthus. This offers flexibility and allows the end user to choose best quality fuel for their money available at any given time.
This “multi-fuel” flexibility is accomplished in a number of ways. The most efficient systems on the market today feature a moving step grate. This enables the most complete combustion by continually moving and agitating the fuel during the burning process, delivering the most energy per unit of fuel and enabling the boiler to cope with a wide variation in fuel quality.
You also need to be aware of headline efficiency levels quoted by boiler suppliers as a rate of 90% or above may only be achieved when the boiler is operating at full output. This is important because there may be only be a requirement for the boiler to run at full output during especially cold weather. Good boilers operate as efficiently at 25% output as they do at 100%, which is called modulation. Some boiler systems will also require a technical support visit to switch between fuel types, but a high specification step grate system with electronic controls allows this to be done by the user at the touch of a button.
The correct sizing of the boiler system is an important part of system design for a number of reasons. RHI payments are based on “useful heat” so specifying a higher output than is necessary will not gain higher RHI payments. Rather than using one large boiler to meet the heat requirements, there are benefits to cascading a number of smaller boilers to provide the same output. The cascading approach allows for redundancy, in case there is a fault on one of the boilers, and delivers maximum efficiency whilst modulating at lower required outputs during the summer.
Biomass boilers can represent huge financial savings over fossil fuels. A recent installation that we completed for a 100kW system running on wood chips will gain fuel cost savings of 75% or in excess of £6,000 a year over heating oil. Typically, a 198kW system running on wood chips would save over £8,000 a year over oil.
Reduction in CO2 is becoming increasingly important for both private and public sector organisations. The Biomass Energy Centre states that CO2 savings of up to 96% can be achieved by burning biomass compared to fossil fuels, a great way for housing developers and specifiers to meet planning requirements. This will become even more the case when the minimum emissions standards in the Building Regulations increase in 2013.
As well as reduced fossil fuel costs, the RHI offers a great incentive for the country to meet legally binding CO2 reduction targets and to address climate change. The 100kW system above could expect to earn £10,000 or more a year for the 20 years of the scheme and the 198kW system would expect to gain over £20,000 a year.
Treco’s RHI calculator is available as a free download on www.treco.co.uk. This spreadsheet allows you to input the installed cost of a biomass boiler system and shows your potential RHI payments, fuel savings and the payback from the investment. The figures are expressed in both annual terms and as a total for the duration of the scheme and there are worked examples on the website to illustrate the RHI payments and fuel cost savings that can be achieved at different output levels. The combination of fuel cost savings and RHI payments offer a very attractive return on investment as the scheme often pays back within 5 years.
In summary, system design, fuel flexibility, efficiency levels and ease of use are key considerations. We always recommend visiting a similar installation to that proposed, enabling discussion with a client who has experience of the same type of system and if we can help in any way, we would be delighted to discuss your project. (938 words)
www.treco.co.uk or 0845 130 9012