Chiller-based hvac systems still have a vital role to play in improving energy efficiency in commercial buildings. In fact advances in technology mean that some chillers now qualify for the Renewable Heat Incentive. Martin Hayward looks at why chillers are still so important when it comes to cooling - and heating - our buildings.
The increased use of VRF heating and cooling systems in Europe has resulted in their sales outstripping those of applied systems in certain applications and building sizes. This is mainly due to an increase in the awareness of VRF and an ever expanding product range.

The simplicity of VRF design means that often manufacturers produce their own design and selection programmes and the products are, in many cases, specified by contractors, cutting out the need for consultants. While this may be the perfect solution for some buildings, it is important that exact requirements are examined at the outset and all options explored before deciding on the final solution.

In certain situations, chiller-based systems still provide the best answer to the hvac question.

For those looking for flexibility, chillers can offer an almost endless variety of options. For buildings that are too large for VRF to be efficient or where piping lengths are greater than feasible with VRF, chillers provide system designers with a range of bespoke solutions to address their needs.

Chillers are particularly suitable for new-build applications where an occupant such as a healthcare provider, for example, is likely to stay for the long term. Because of their flexibility, chillers can be built to the specific requirements of the client. However, if the building is likely to have a high turnover of occupants, or there is more than one occupant in a building, it could be that an 'off the shelf' VRF or VRV system would be more appropriate.

The installation of chillers can be easier (and cheaper) because all refrigerant is contained within the unit and does not require specialist handling skills. This also results in lower post-installation maintenance costs. Applied systems also have greater flexibility to be expanded in the future and allow engineers greater design responsibility. Applied systems are also more suited to applications where large volumes of fresh air are required.

In an environment where cooling is a year-round requirement such as data centres or processing plants, chiller-based systems will invariably provide the best and most efficient solution. With careful specification and design, it is possible to improve energy efficiency and reduce running costs even further.

Within replacement market

A large proportion of chiller specification is within the replacement market. Given that there is pressure on building managers to reduce downtime, it is common for snap decisions to be made. But to simply replace like for like is not only rash, it could also end up costing more money in the long run.

Outdated plant can be 15 to 20 years old and the chances of a cooling requirement remaining the same over that period are slim indeed. Although it is common to assume that this cooling requirement will have increased, very often it may well have reduced over time. So although it is tempting to play safe and to replace a chiller with one of the same capacity or greater, in many cases this would mean over-specifying and using more energy than is necessary, resulting in higher energy bills.

In fact, there is no need to specify expensive equipment with exceptional seasonal energy efficiency ratios because the seasonal load variation is actually quite small. Over-specifying a chiller system - like any other system - pushes up costs unnecessarily.

'Free' cooling is another area that could provide potential energy savings. For areas where cooling requires a constant year-round load, systems designed to utilise the outside air temperature in order to remove excess heat can prove cost effective. As these systems use 'free' cold air, plentiful in the UK's winter months, they can prove to be a highly cost effective and energy efficient solution.

However, water-cooled heat pump chillers can provide a heating function and these systems may even qualify for the Government's Renewable Heat Incentive. Daikin's own range can provide low temperature hot water for fan coil units to provide heating for a variety of commercial applications. By reversing the cooling cycle to take latent heat from the ground, hot water can be produced for space heating and because the system is based on ground source heat pump technology, it qualifies for payments under the recently introduced Renewable Heat Incentive.

Whatever the application, it is vital to analyse from the outset the precise heating and cooling requirements, how these might change and the extent of the flexibility that any system may require. Only then should decisions be taken about which solution is appropriate in any given circumstance.

• Martin Hayward is manager of Daikin UK's Applied Systems Department