See the bigger picture for tight climate control
Technological advances have revolutionised VRV/VRF capabilities and how these highly energy efficient systems are suitable for more applications than ever before, says Martin Passingham
Since the introduction 30 years ago, Variable Refrigerant Volume (VRV) - or, generically, Variable Refrigerant Flow (VRF) - solutions have proven to be a highly energy efficient way to control a building's climate system. However, until now, there has been an assumption that they are only suitable for certain types of applications, such as small to medium sized office buildings. But recent technological advances mean this is simply no longer true.
Perhaps because of VRV's modularity, it is often perceived as 'one step up' from a split or multi-split system - and therefore most suitable for buildings of up to 3,000sqm. In reality, the latest VRV systems can be applied on a much greater scale, to create fully integrated systems for buildings of any size.
In fact, it is when VRV systems are designed as a whole building solution that they can offer the very highest energy efficiencies of all.
Because VRV varies the refrigerant volume within the system to match the building's precise requirements at any moment, only the minimum level of energy is required to ensure that each area maintains its set temperature, thus saving energy costs and reducing carbon emissions. Indeed, the very latest generation of VRV heat pumps incorporates variable refrigerant temperature control, which automatically adapts the system to the individual building and climate requirements, for even greater energy efficiencies.
What is more, a genuinely versatile VRV heat recovery system, operating in balanced mode to manage climate control over an entire building, can increase energy efficiency even further.
A typical office building may require both cooling and heating simultaneously as well as hot water storage for washrooms and kitchens. With the indoor units in cooling mode, a typical Coefficient of Performance (CoP) of 3.97 can be achieved. In milder conditions, when 75 per cent of the indoor units are in cooling mode and 25 per cent are in heating mode, the efficiencies rise to COPs of 5.57. But when the system is fully balanced between heating and cooling, efficiencies can increase to as much as 10.07.
However, to achieve these market-leading COPs, it is vital to analyse a building's multiple requirements, usage patterns and varying occupancy levels right from the start. This allows design of an intelligent solution that optimises energy efficiency and heat recovery.
This may mean specifying the system so that it is capable of cooling one area of the building that is experiencing the highest heat gains and transferring that reclaimed heat to other areas requiring heating or hot water. By doing so, recovered heat can be diverted to heat water, or to additional applications such as over-door air curtains. This can save up to 67 per cent in running costs, when compared with electrically heated models.
The integration of a VRV system with the latest intelligent control systems can increase energy efficiency even more. For example, intelligent controls are now capable of allowing users to set system schedules on a weekly, monthly and annual basis. These can take into account holidays and seasonal variations in demand throughout the year, ensuring the system is being operated in the most energy-efficient way.
Additionally, smart controls can also monitor energy consumption across a range of equipment, including air conditioning, to pinpoint areas of a building where the most energy savings can be made.
All of these technological advances mean that VRV systems can provide unrivalled energy savings. According to Franklin + Andrews, one of the world's leading construction economists, running costs for VRV heat recovery systems are up to £6.25/sq m of gross floor area. This compares highly favourably with a two or four pipe fan coil system, which can cost as much as £8.75/m2 and £10.75/sq m of gross floor area respectively - a 40-72 per cent increase on running costs compared with a VRV heat recovery system.
A VRV system is more space efficient than a chiller too, because it requires much less plant space. For example, Franklin + Andrews estimates that a two or four pipe fan coil system could take up around 7 per cent of the overall lettable floor area of the building, while a comparable VRV-equipped building would take up between 3-5 per cent. This means that VRV allows developers to maximise the rental space, by requiring 29 per cent less plant space than a chiller system.
Of course, cost savings must be matched by a reduction in CO2 emissions too, as designers strive to meet ever tougher targets in the years ahead. A framework of continuous improvements has been set with a new version of the Building Regulations due out in October 2013, an expected change in 2016 and a final revision in 2019.
This means that by 2019, all new buildings will have to deliver zero carbon emissions from the energy required for heating, cooling, hot water and lighting. These challenging targets will require considerable innovations to improve on current practices.
Additionally, many organisations and local authorities use BREEAM as a mandatory design standard to ensure that both new build and existing premises meet the exacting requirements for CO2 emission reductions. For example, the healthcare sector has designated that all new buildings must meet a BREEAM Excellent rating and existing building stock must achieve a Very Good rating.
Again, heat pump technology can assist building designers in meeting the requirements of BREEAM by delivering heat into a building in an energy efficient, controlled way. According to BREEAM criteria, specific credits can be given for integrated services and building management systems. Further awards for innovation are also possible, depending on the system design.
All of these technological advances have made VRV heat pumps more energy efficient than ever - and for a wider range of buildings. It is time to think on a grander scale about the role they can play in meeting today's ever higher
standards for energy efficiency.
// The author is product manager, DX at Daikin UK //
10 September 2013