Feasibility

Is Biomass DH a feasible technology for growth within the UK?

Based on this project, it is believed that the technology has a lot of potential for further expansion within the UK. It may play a key role in providing energy security and implementing renewable energy into meeting future building heat demands.

High Capital Costs

Retro-fitting a biomass DH scheme is extremely difficult to make financially and technically feasible. The lack of base-case capital costs ensure that the simple payback period remains high. It is incredibly difficult to endorse biomass DH heating in functioning buildings, unless the outlined ‘Selection Criteria’ is met almost perfectly. Typically, one should not expect a payback period below 10 years for a proposed scheme for relatively high-performing existing buildings. The best case results from our case studies ranged between 15.6 – 16.7 years. We did not recommend these schemes to the council. New builds are far more viable, with regards financial and technical feasibility.

RHI Dependence

With the RHI incentive, the price per kWh paid by the bill-payer can almost be halved. For our ‘Site 1’ case study for example, with the RHI payments the price per kWh stands at 3.1p/kWh. Without the payment it stands at 5.5kWh. The DH scheme is highly dependent on the money received from powering the network from biomass fuel. Once the scheme extends to a size whereby a boiler over 1GW is required, RHI payments dramatically reduce. This limits the feasibility of biomass driven DH. Often, optimising thermal storage may provide a solution to reducing the boiler size to power larger schemes.

Our Site Selection Criteria

A high heat density and poor performing base case is critical. The average heat demand should be substantially higher than 10,000kW/km2. Ideally, the scheme should be implemented into new builds, whereby the base case performance is not working against the schemes financial and technical feasibility.

Cost Uncertainties

These have been tacked throughout the project yet remain a key barrier due to low market penetration of the technology within the UK. The sensitivity performed and theory outlined on non-definitive cost data may be used as a general guideline for any proposed project.

DEFRA Restrictions

Planning permission issues must be appreciated when undertaking a biomass DH feasibility analysis. The substantial impact that these issues have on project development have been uncovered within this project. Using the case study as a realistic example, the stack height and biomass boiler size is greatly restricted due to current environmental regulations. It is difficult to position a potential energy centre. Even after determining a project is feasible, DEFRA restriction or public opposition can easily hault the projects progression.

General Methodology:

The methodology and numerous design tools outlined can be used to undertake a high-level feasibility analysis on any given site. This process is relatively quick and easy, prior to detailed system design. The lack of design tools has historically been a major barrier to the technologies expansion within the UK. Individual weighting factors and sensitivity analysis may be applied to determine biomass DH feasibility across the UK. Schemes should always be analysed on a case by case basis to determine feasibility.

Further Work

This project was restricted to biomass DH feasibility. Also, the case study was restricted in scale and building types. This was mainly to ensure manageability and detail in the work that was performed. This refined focus was important in meeting a concise and practical aim, objectives and deliverables.

Upon completion, the group would like to highlight a number of areas in which the project may be expanded or enhanced in further detail. These have been tabulated below:

Further Work	Details
Biomass CHP DH Analysis	An interesting analysis may be performed by incorporating combined heat and power into the project. Biomass driven CHP is often cited as a poor performer as the combustion temperatures associated with biomass boilers are relatively low. Combined cycle electricity production is not an option. A relatively consistent heat demand throughout the year would be critical.
Base Case Retrofitting	Comparing the benefits of upgrading individual building fabric and heating system performance against constructing a new DH scheme may be analyzed. Comparing the feasibility of installing individual biomass boilers into buildings over a biomass DH network may be examined.
Heat Source Variation	Instead of biomass, gas or other forms of renewable energy heat production may be used to power the scheme, with the resulting feasibility analyzed. Concentrated solar thermal could be an alternative to explore.
DH Design Day Load Profile Analysis	Further detailed analysis may be performed in generating an accurate design day load profile The method used in the case study was deemed acceptable for a high-level feasibility analysis This should only be explored if a detailed system design is required.
Including Housing/Different Building Types	Expanding the biomass DH scheme to include housing may be an option to explore. Examining the impact of different building functions, outside the scope of this case study, may also provide useful results and conclusions.
Present Cost Assumption Analysis	Much of the equipment and construction costs used for the case study were based on logical assumptions or data that may not be considered definite. Costing such as the piping network construction cost estimations may be analyzed further as this data is not easily obtainable due to lower market penetration of the technology within the UK. This would ensure a more accurate feasibility methodology.
Further Sensitivity/ Future Cost Analysis	Sensitivity was limited due to time constraints. Further sensitivity of future costs may reduce the financial risks involved with designing and implementing a DH scheme.
Heat Exchanger Impact	The transfer of heat from the main piping distribution network into each individual building may be looked at in more detail. This was taken as a single, realistic efficiency figure for each building within the case study examined.