The relationship between thermal and electrical demand is key to the correct design and specification of a CHP system.
A commercially sound operating strategy should be based around the spark gap or rate.
A mechanically sound operating strategy should take into account the facility infrastructure, and the relationship of the CHP system with both the Building Management System (BMS) and boilers.
Relationship with boilers & BMS
More than 90% of operational shutdowns or failures of CHP plant are caused by bad control strategy or errors in the surrounding systems. The efficiency of a CHP system will become irrelevant if the design and installation does not outline the correct relationship with the facilities existing boilers and BMS.
Electrical Infrastructure and G59
A CHP system is in effect a power supply connected to the national grid. There are many considerations before a CHP system can be commissioned, in other words become operational and connected to the power network. The main reason for the G59 recommendations is to regulate generator applications, so that no generators are connected to the grid without the specific knowledge and permission of the local electricity authority.
Allocation of sufficient space is a common design oversight when specifying CHP. The Construction Design and Management (CDM) regulations require designers to ‘build-in’ sufficient and appropriate access all around the unit, for safe and effective operation and maintenance procedures throughout its entire life.
There are three areas of consideration for acoustics:
- Breakout noise (sound that escapes from the engine package itself).
- Ventilation noise (for units that require ventilation – not all do – this is sound which escapes through the air intake / discharge ductwork).
- Exhaust noise.
Incorrect ‘Dump Rad’ use
There is no economic basis for using CHP to create electricity with no heat demand on the building. Given that CHP produces heat energy as a significant output from the gas fuel used to drive it, dumping this heat energy completely destroys the financial proposition of operating the CHP.