Discover 5 key steps you need to take to achieve Good Quality CHP.
To optimise CHP efficiency and gain access to attractive fiscal incentives for gas generated CHP, schemes must be certified as ‘Good Quality CHP’ under the Combined Heat and Power Quality Assurance programme (CHPQA).
CHPQA is a voluntary initiative, providing a methodology for assessing the quality of CHP schemes according to energy efficiency and environmental performance. As such, CHP is assessed on its power efficiency and by a Quality Index (QI), which is a measure of the overall energy efficiency and delivery of primary energy saving.
To achieve 'Good Quality' certification schemes you must achieve or exceed the threshold criteria. These criteria are a QI rating of 100, and power efficiency of greater than 20%. Such ratings are achieved by examining data for fuel used, power generated, heat supplied and hours run. The thresholds are also designed to meet the requirements of the European CHP Directive.
By achieving or exceeding these minimum standards, schemes qualify as 'good quality CHP', which is a pre-requisite for the major fiscal incentives. Failure to achieve the threshold results in a scaling back of the fuel and/or electricity that will qualify for tax benefits.
The key steps to achieving CHPQA compliance and 'Good Quality CHP' are:
1. Accurate sizing of a CHP system is key and should be calculated in tandem with proposed demand reduction measures. In most cases you should limit the maximum size of the CHP to the electrical base load, but you should also take into account your heat demand so that you utilise as much as possible and don't resort to excessive heat dumping. It is essential to optimise the electricity and power generation to ensure the best financial/carbon savings. Boilers can always be used if there is an exceptional heat demand during peak periods.
2. Ensure CHP acts as the lead heat source at all times. When integrating CHP into heating systems for new build schemes, select flow and return temperatures of heating circuits to optimise operation and prevent your CHP from 'tripping' due to high return temperatures.
3. Ensure your metering is calibrated and complies with CHPQA standards. It should be capable of capturing fuel use, useful heat produced and electricity generated. For larger schemes this needs to be recorded monthly but smaller schemes need only record the annual quantities. Some sub 500kWe schemes opt for a simpler metering strategy using the 'unit list', which means they are only required to measure and monitor electric output. However, the 'unit list' can only be used if a heat rejection radiator has not been fitted. The unit list is available on the CHPQA website and lists CHPs whose performance has been assessed by CHPQA to allow fuel usage to be inferred from the electric output. Whilst in the early years of the scheme, this did go a long way to reducing complexity and cost for small players, but we would always advise customers to monitor all energy outputs via Good Quality metering to ensure that their asset (and their service provider) is working to the best of its ability.
4. Design and implement a detailed control strategy that will yield the best performance - both environmentally and economically. This should be connected to the wider building energy management system, or integrated into the controller - as is the case with ENER-G's E-Power controls system.
5. Implement a robust proactive maintenance and servicing strategy, in line with the manufacturer's guidelines, to keep your system operating at optimum performance. However good your CHP is technically, it won't save money if it isn't running properly. A CHP system is a business critical machine that requires daily observation to check for good operation. This can be performed via a remote control and diagnostic system, or by local monitoring. This will also identify trends that could indicate problems further down the line. Condition based monitoring, including regularly reviewing oil samples, will inform a robust and responsive servicing and maintenance to keep your cogeneration system in peak condition.
- CHPQA is a voluntary initiative, providing a methodology for assessing the quality of CHP schemes according to energy efficiency and environmental performance.
- Key steps to achieving CHPQA compliance include accurate sizing, designing and implementing a detailed control strategy and ensuring your metering is calibrated.
- By achieving or exceeding these minimum standards, schemes qualify as 'good quality CHP', which is a pre-requisite for the major fiscal incentives.
Optimising CHP efficiency is key to attracting fiscal incentives. Read The ENER-G High Quality CHP Plan.
Topics: CHP / Cogeneration