Building owners are seeking out highly energy-efficient climate control systems to maintain indoor comfort. Martin Passingham explains how variable refrigerant volume (VRV) and variable refrigerant temperature (VRT) technologies can help balance heat output.
16 February 2015
Buildings are responsible for nearly half of all UK carbon dioxide emissions, with non-domestic buildings producing 18 per cent, principally from space heating and cooling, water heating, lighting and other building systems.
When designing new buildings, many organisations use BREEAM as a mandatory standard to ensure that they meet the exacting requirements for CO2 emission reductions. In addition to this, the new Part L of the Building Regulations came into force in April 2014. It requires energy efficiency standards of new non-domestic buildings to improve by 9 per cent on the 2010 regulations.
The new rules also apply when specific building services work, including climate control, is carried out.
With these rising demands for sustainable buildings, plus volatile energy prices and a warming climate, the business case for reappraising whole building energy strategies for efficiency savings is growing. To meet the new requirements, FMs are increasingly looking to HVAC systems that deliver heat into all building areas in a balanced, efficient and controlled way.
Use VRV technology
Variable refrigerant volume (VRV) technology with variable refrigerant temperature (VRT) and integrated heat recovery offers one of the few whole building solutions that achieve both efficiency and zoned building user comfort at reduced energy cost and CO2 emissions.
Unlike traditional HVAC solutions, which are commonly powered and operated separately from each other, an integrated three-pipe VRV system that provides simultaneous heating and cooling makes better use of the primary energy source. Additionally, VRV with heat recovery effectively reuses the ambient heat produced by equipment and lighting, refrigeration units, solar gain and body heat, which otherwise would be rejected and released into the atmosphere, for heating and generating hot water.
Such a total climate control system supports building operators in achieving their CO2 reduction targets and lowers operating cost in the long term, contributing to a more sustainable built environment.
At the same time the latest generation of VRV manipulates evaporating and condensing temperatures to help the system to meet the required loads at all times, consistently aiding optimum balance between efficiency and tenants' comfort across varying building zones.
No rejected energy
The ultimate operating condition for VRV systems is usually during autumn and spring temperatures and demands in the building may balance to 50 per cent heating and 50 per cent cooling. This is where VRV operates at maximum efficiency, with almost no rejected energy.
For example, a regular office building requires cooling and heating to maintain the indoor temperature between 20°C and 24°C, with 200 litres of water storage being required for washrooms and 150 litres of water storage for kitchens.
By recovering the heat from indoor units in cooling mode, a coefficient of performance (COP) of four can be achieved. In milder conditions, when 75 per cent of the indoor units are in cooling mode with 25 per cent in heating mode, the efficiencies rise to COPs of six. When a VRV system is fully balanced between heating and cooling, however, performance efficiencies can reach in excess of seven.
The key is to design the system so that it operates as close as possible to a balanced heating and cooling operation for the maximum amount of time, according to the building's energy use statistics. The heat use of new buildings is typically balanced by integrating a number of peripheral functions, including the use of waste heat from cooled areas, such as IT rooms or hotel kitchens, heating water overnight or connecting to low temperature hot water modules for underfloor heating.
Maintain the balance
To achieve higher COPs, in any case, it is vital to analyse right from the start a building's use patterns, varying occupancy levels and likely energy consumption. This will enable the design of an intelligent modular system that maximises seasonal efficiency and capitalises on existing sources for heat recovery.
Individual design also allows the VRV system to be scaled to fit any size of commercial building over its lifetime and to be reconfigured easily if occupant needs or internal layouts change. This adaptability reassures building owners and managers that VRV with heat recovery will suit the application long into the future with minimal disruption to daily operations when reconfiguration or upgrading does become necessary.
The benefits of a total HVAC solution using VRV technology are clear. Increased energy efficiencies cut the building's carbon footprint and energy bills, while flexible, modular design options for balancing heat and cooling in buildings across the retail, healthcare, offices, hospitality and public sectors future-proof the whole building to deliver indoor comfort.
Property owners and FMs looking to integrate a greener, high-performance HVAC system in their buildings without compromising the comfort of users should seek advice from a reputable manufacturer at the design stage to fully capitalise on the development of the optimum HVAC solution.
Martin Passingham is product manager at Daikin UK