Open-access content Monday 8th February 2016
11 February 2016 | By Jim Henley
Jim Henley explains what the latest Ecodesign European Directive, which started on 1st January, means for the heating, ventilating, and air conditioning industry.
The Ecodesign of Energy Related Products Directive 2009/125/EC is a framework that primarily focuses on energy in use. It does this by setting minimum requirements for certain energy-consuming products.
Certainly in the UK before Ecodesign 1253/2014, the driver behind energy efficiency had been the increasing Part L efficiency requirements to reduce overall specific fan power (SFP). This reducing fan power consumption required manufacturers to provide lower overall internal unit resistances by using low-pressure loss filter systems, lower component pressures through reduced unit velocity resulting in larger air handling units (AHUs), along with improved fan and motor efficiencies.
With the drive for even lower SFP values, designer/client partnerships are required, as system resistances also need to be reduced. At the same time, AHU selections are optimising unit pressures through best component design and operating velocity, which generally means that duct systems and AHUs are increasing in size and cost.
Grey areasImposition of the new standard for Non-residential Ventilation Units (NRVU) began in January and big challenges have been identified in several areas for compliance implementation. The standard imposes heat recovery on almost all systems classed as Bidirectional Ventilation Units (BVU).
As the law is new, there are grey areas where people are uncertain whether or not to fit heat recovery solutions (HRS); these must be addressed individually. For a supplier, it is key for the designers/clients to understand when a system dictates the use of heat recovery and to do a technical review.
A large part of the standard's emphasis is on HRS efficiency. Continental Europe has long been a large user of HRS owing to big temperature swings during the year. The UK sees smaller differentials between internal comfort conditions, supply temperatures and external ambience in summer and winter.
Within traditional systems in the UK, there has been a large use of free cooling mixing arrangements coupled with air-quality management to provide energy-efficient air systems. But under the new standard mixing is no longer considered as efficient heat recovery. Despite this, the use of free cooling could still have had a valid part to play in certain areas and applications.
As heat recovery systems are now needed on most supply and extract systems, additional adjustments are required of some systems that previously only used mechanical extract with no HRS. The second area to affect existing HRS is the increased efficiency requirements, which for runaround coil systems can be a challenge. Heat recovery efficiencies in the new legislation are also set to increase further in 2018, and when compared with the previous guidelines from Part L, the new regulations have imposed significant increases.
The standard requires that efficiency of the HR device is based on equal airflows and in dry conditions. Most operational conditions generally have a degree of latent heat energy within either the supply or extract airstream (which improves the efficiency of the HRS) and also many systems have unbalanced airflow between supply and extract.
For systems with unbalanced airflows the key area of change will be the equalisation of the airflows to match the supply stream as this is to be used as the reference flow rate. In simple terms, the lower airflow portion of the AHU will increase in size to enable the efficiency to be achieved in a theoretical balanced flow condition.
With efficiency of the HRS based on dry conditions, this will require a higher efficiency device to meet the dry conditions increasing the heat transfer surfaces of the device with resulting increases in size, cost and operating pressures, which will need to be mitigated to maintain SFP levels. This becomes a vicious circle of increased efficiency/pressure drop and/or increased size to reduce velocity and pressure drop while maintaining SFP levels; the optimisation of AHU selection is becoming an art form.
Driving improvementAll these new efficiency levels will also drive base improvements in the performance of the heat recovery devices themselves, along with the potential for combined hybrid cooling/reclaim coils and other innovations.
The key is to understand the system and layouts to enable the best solution to be provided, but generally it will mean larger AHUs and moving more to efficient plates and heat wheels.
The new standard does not stop at heat recovery efficiency improvements; it includes several other factors - some mandatory and used within the certification, along with others that are enabling informed decisions to be made for best equipment solution.
While the new standard is not perfect for the UK, it does present a method of certifying AHUs relative to the system they serve and will provide clients with reduced energy use for the life of the product.
Jim Henley is sales director of Daikin Applied UK