Renewable motivator

5 May 2014

The Renewable Heat Incentive has proved to be a boon for companies seeking cost-effective ways to dry timber. Sustainable Energy managing director Dr Gabriel Gallagher reports.

It has been almost three-and-a-half years since the launch of the Renewable Heat Incentive (RHI), which was a world first in terms of incentivising renewable heat generation. In that time, the RHI has had a big impact on the implementation of wood fired heating systems in the timber industry and has been instrumental in the rising value of timber co-products for energy generation.

In the timber industry, the largest area of growth has been in the application of biomass boilers for sawn timber drying. Drying of the wood fuel itself has been deemed to be an eligible heat use, despite a question mark over eligibility in the original consultation process, particularly where the dried wood fuel is used on site by the same boiler used to dry it or where wood drying activities would not be viable without the RHI.

The majority of biomass schemes are less than 1MW because of a last-minute reduction of the large-scale biomass tariff for plants larger than 1MW to 1p/kWh prior to launch of the scheme. To date, 3,160 biomass heating plants have been accredited for the RHI, with a total installed capacity of 644MW. Of these, 2,712 biomass heating plants were under 200kW capacity and 431 plants were between 200kW and 1MW capacity.

However, despite the attractive financial benefits to the timber industry there have been issues and frustrations with the application process and the eligibility and accuracy of heat meter arrangements. This has caused accreditation delays and operational issues for the schemes after accreditation. Most commonly, biomass heating systems have failed to gain accreditation because of incorrect meter placement, ineligible heat uses and boilers not meeting emission limits.

There have also been many instances of accredited schemes having RHI payments suspended because of irregularities in ongoing heat meter reading submissions. Most industrial schemes require 'multiple' heat meters under the RHI definition - this means that multiple meters are required to meter biomass boiler output, any fossil fuel boiler output and the end user heat demands. If the total consumption figure is less than the total heat generation figure, this would be assumed to be due to system inefficiency. However, there have been many cases of meter readings giving a total consumption higher than total generation - this would be treated as a metering error and RHI payments would be suspended until resolution is found or system changes are made.

The metering requirement for RHI eligibility is that heat meters must comply with the Measuring Instrument Directive and must have an accuracy level of MID Class 2 or above (an MID class 2 meter may have an accuracy of +/- 3.5%), therefore if two meters are used this could introduce an inaccuracy of up to 7% and still meet eligibility.

So how are many sites recording inaccuracies greater than this? New research conducted on metering inaccuracies has found that in certain circumstances, as the temperature difference across the meter reduces, the inaccuracy increases (sometimes above the limits of MID Class 2), although this is not addressed within the EN standard and is currently not accounted for in the RHI processes.

Key changes since RHI launch
In September 2013, mandatory emission limits for biomass boilers were introduced - this meant that from that point all boiler suppliers have to provide an RHI Emissions Certificate for all boiler models, proving emissions are within the prescribed limits. This caused a slowdown in the installation of biomass boilers as boiler manufacturers sought to get boilers tested and certificated to satisfy the eligibility requirements. The emissions limits are fair and achievable and so most small-scale boilers should comply easily, however, some larger boilers will need to consider particle filtration to ensure the boiler meets the prescribed limits.

A system of 'degression' has also been implemented which will slowly reduce RHI tariffs for new applications as the level of implementation reaches set 'trigger points' and the RHI budget becomes allocated. This has already led to a slight reduction of the medium scale tariff (for systems between 200-1000kW) although small-scale and large-scale tariffs have not been reduced to date. The next expected tariff reduction will be in July, although the expected reduction value is not yet known.

Under the degression system tariffs ill continue to drop as the scheme nears its end in 2016.

DECC is currently in consultation for a potential increase to the large-scale tariff from the current level of 1p/kWh to 2p/kWh. The current low large-scale tariff 1p/kWh has driven a general industry trend to install plants of less than 1MW to maximise income from the RHI. There has also been a rise in the number of small timber processing companies developing <200kW biomass heating projects for small-scale drying facilities comprising single kilns or to provide space heating using co-products.

  • Sustainable Energy Ltd has advised on over 40MW of biomass heating schemes across the timber sector and provides management services for RHI accreditation.

Dr Gabriel Gallagher
Of the 3,160 biomass heating plants accredited for the RHI, the majority are under 200kW capacity. Photo: Talbotts Biomass Energy Systems