Early CHP specification is crucial for viability of district heating systems: ENER-G

ENER-G 230kWe CHP unit

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, said John Hyde, consultant specification manager for ENER-G Combined Power-G.

CHP specification is often considered too late in the planning and construction process to achieve its full energy saving potential.

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, Hyde added.

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, Hyde added. 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,” Hyde added.

When all this 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, Hyde continued.

According to Hyde, 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 realized, Hyde added.

Rajani Baburajan