Failure to accurately size combined heat and power (CHP) at the pre-planning stage of building design is reducing the viability of district heating networks, according to cogeneration specialist ENER-G.
Speaking at a recent Association for Decentralised Energy (ADE) seminar on district heating, John Hyde, Consultant Specification Manager for ENER-G Combined Power, told the audience that CHP specification is often considered too late in the planning and construction process to achieve its full energy saving potential.
He explained: “In the right circumstances CHP can yield a typical return on investment within five years. This can provide impressive cost and carbon savings over a typical 15 years+ product lifecycle. Failure to size your CHP system correctly, however, will cancel out the benefits of choosing CHP and increase the long-term operating costs for stakeholders and ESCos, plus push up costs for end users. A CHP engine cannot run below a minimum load. If it’s too large, it will not operate for long enough and if it’s too small it will not provide the full cost savings.
“When we look at CHP and district heating networks, we need to think about iterative decisions made at each work stage and how that affects specification, purchase, installation and commissioning. When this all goes well, CHP can produce a reliable, cost competitive heat supply, reduce CO2 emissions and reduce energy usage. This ultimately helps to combat the classic energy trilemma of security, affordability and sustainability.”
He continued: “Often detailed CHP sizing doesn’t take place until stage four of the eight stages of the RIBA 2013 Plan of Work. By this time, the design has often gone too far and cannot be easily changed due to planning requirements. Unfortunately for CHP, when it is specified as simply another piece of plant in a construction project rather than a long-term investment, the true lifetime costs are excluded and the potential for energy savings are never realised.
“CIBSE’s recent emphasis on ‘soft-landings’ goes some way to address this problem and we need to see more of this for true sustainable construction. In addition, new publications like the 2015 CIBSE Heat networks: Code of Practice (CP1) and CIBSE’s AM12: CHP for Buildings have increased the focus on overall guidance for good CHP sizing and are helping to ensure a correct match with the load profiles of district heating networks.”
The seminar was attended by engineering designers, installers, developers and stakeholders involved in district heating networks. During the afternoon industry speakers shared best practice advice on how CHP can be designed, implemented and operated sustainably from cradle to grave.
Commenting on the seminar, attendee Isabelle Smith of Atkins Global, said: “The event was really useful as it allowed many different people from the construction industry to discuss the issues around CHP and how it is used in the industry. Sharing experiences is a great way to learn. especially when it covers such a broad area – from feasibility to operation.”
Steven Wallman of Skelly & Couch Ltd, said: “This event was presented by those that live and breathe CHP. It addressed the key considerations in feasibility, design and maintenance, providing guidance in best practice and current literature.”
