Appraising energy savings for a major dyeing and printing works

With a combined annual gas and electricity bill of about £2.5 million, a major UK dyeing and printing works was keen to explore ways to reduce its energy use and associated costs. RSK worked with a leading combined heat and power (CHP) system manufacturer to develop a commercially focused solution. This work was part of our role in providing specialist energy efficiency and renewable energy advice to ENWORKS, a regional environmental business-support programme that coordinates and gives environmental advice, training and support to businesses throughout North West England.

We produced an early-stage appraisal of the potential to retrofit a 500-kW CHP system and other technologies. This appraisal concluded that the best place to install the engine was in a vacant area of the plant room to provide most of the water heating required for the various processes. In this way, the recovered process heat currently used for water heating could be channelled elsewhere and/or used to heat office space via heat pumps. In addition to heating, this would generate a significant proportion of the company’s electricity needs on-site, thereby reducing its energy costs.

Assuming technical and commercial viability, two options were also provided for purchasing CHP engines, a tradition capital purchase or a discount energy purchase. In the first scenario, the client company buys the engine outright and maintains it. Savings over the lifetime of the system result from the zero-cost electricity that is generated on-site to replace mains electricity. In this example, financial payback was likely after about 3.2 years.

In a discount energy purchase scenario, the supplier effectively gives the engine to its client company and maintains it for an agreed period. The client thereby avoids capital layout. Thereafter, the supplier sells the generated electricity to its client. In this example, a net annual saving to the client of £50,000 was estimated.

In addition to CHP, the viability of a biomass heating system and heat pumps to assist in the heating of office space and water was also assessed. However, the payback periods associated with these solutions were found to be longer than for CHP, so they were considered to be less commercially viable.