CHP: CAN LESS REALLY BE MORE?

When it comes to the specification and subsequent installation of Combined Heat & Power (CHP) modules, a great deal of discussion is often centred around system design and sizing.

Here, Alex Parkinson, Commercial Sales Manager for CHP at Bosch Commercial and Industrial Heating, evaluates the pros and cons of multiple module CHP systems vs single module arrangements: (Read More)

“With CHP still generally viewed as something of an emerging technology, discussions around the best design practices are still ongoing. As far as this is concerned, there appears to be differences of opinion across the industry with regard to when cascades of multiple CHP modules, and single module systems should be used. Generally speaking, the conclusions lie in the assessment of three key areas.

Installation cost

“When it comes to the time and cost involved in the installation of a CHP system, a suitably-sized single module inevitably boasts the fewest complications and subsequently, the most cost-effective installation. The delivery and installation of one module means that only one set of gas, electrical, BMS, and flow/return connections needs to be made, and only one meter required. As a result, the installation and commissioning procedure ought to be relatively straightforward.

Plant Space

“As with any commercial or industrial heating and hot water technology, an investment in CHP will have spatial implications and as a result, careful planning of the plant room layout will be required. Naturally, one of the major drawbacks of a system comprising of multiple CHP modules is that more plant space is generally required. The physical dimensions of each CHP module isn’t the only logistical consideration to be made here either, as each module will generally require a connecting buffer vessel and a certain amount of clearance to be able to operate to its design potential.

Load mapping

“The most effective way to design a CHP system is to align the electrical output as closely as possible with the load of the application. Whilst the advantage of a CHP cascade is the ability to track electrical load to a lower output in the event of a reduction in demand, this can also prove to jeopardise efficiency levels. Ultimately, the full benefit is only realised when the number of hours that the system runs at full load is maximised, so having modules within a cascade tracking electrical load to lower outputs shouldn’t necessarily be seen as a desirable option.

“As an alternative, a single module system can, if the manufacturer’s product specification allows, modulate both electrically and thermally to 50 per cent of the load. While this level may not be as large a reduction as with a three module cascade for example, having a system designed to modulate for long periods is not a strong design scenario as the cost generally far outweighs the benefit.

“Although it is usually possible to meet the requirements of an end-user with the design and installation of a single or multiple CHP system, it is important to consider the advantages and limitations of each approach beforehand. Recent industry trends suggest that there is a tendency for consultants and contractors to favour a cascade of multiple units; however a single CHP module can often be a more attractive proposition – especially when it comes to installation and maintenance costs. As the range of CHP outputs offered by manufacturers continues to grow, stakeholders will be able to benefit from greater versatility and assurance that a single module can be sized according to the thermal base load of a project.

“Ultimately, the aim for the investor is to have a system in place which maximises efficiency levels and offers a favourable payback period.”

For more information on Bosch Commercial and Industrial Heating, its range of CHP modules, and customer support packages, visit www.bosch-industrial.co.uk