Getting the maximum benefit from air-conditioning inspections
Acting on the recommendations of air-conditioning inspections can definitely save energy, and an EU research project helps to identify the best opportunities to look for during an inspection.
Regular inspection of air conditioning systems with an effective rated output of more than 12 kW has been mandatory under the Energy Performance of Buildings Directive (EPBD) since January 2009. The purpose of the inspection is to try to improve the energy efficiency of such systems. However, to engage the owners of such systems to improve energy efficiency it is essential to answer one question. Is this inspection just another administrative burden or does it really provide some useful insights into possible energy savings?
The Intelligent Energy Europe project Harmonac* has developed and field-tested a CEN Standards-based inspection methodology to assess the actual energy savings to be achieved. What they found is that the owner has an influence on the value of the inspection that should not be underestimated.
The Energy Performance of Buildings Directive (EPBD) requires all air-conditioning systems with a cooling capacity of more than 12 kW have to undergo regular inspections to improve their energy efficiency. While some member states are still defining the legal frameworks for these inspections, such as inspection frequencies and accreditation of experts, the owners of such systems are more concerned about how much will it cost and the benefits to them.
The Harmonac project, supported by Intelligent Energy Europe, has completed a project aimed at understanding where inspections identify real energy-conservation opportunities (ECOs) and help improve the cost-effectiveness of the air-conditioning inspections throughout the EU.
This has been achieved by testing a CEN Standards-based inspection methodology in over 400 field trials across Europe. To support these trials 42 air-conditioning systems and their components have been monitored by measuring their energy consumption for a year in sub-hourly detail. The information from these in-depth studies has been used to provide previously unavailable detail on how, when and in what quantities AC systems and their components consume energy over the course of a year.
One of the main findings of the project was that an inspection can identify energy savings of over 50% in an AC system component, or up to 10% of the total electrical use of a building.
However, the current inspection procedures appear to identify only a small percentage of the potential savings available in many systems. The reason is that many energy-conservation opportunities were not possible to find without long-term monitored data specific to the AC system components. Also, only real consumption data for the system inspected allows the inspector to calculate energy savings and benefits with sufficient authority to convince the owner that this might act as a basis for a decision to invest time and money into improving efficiency.
Furthermore, the easiest energy-conservation opportunities are those related to operating and controlling an AC system, but these can often only be identified with detailed monitoring data. Unfortunately, although monitoring data specific to a system significantly influences the potential identification of energy-saving opportunities, only a few owners and operators of air-conditioning systems have access to this level of system data at present.
The major cost of an inspection is the time taken by the inspector. Field testing showed that there is generally a good correlation between floor area and time taken to complete an inspection. The average time needed for an inspection is about a day for small packaged systems to up to three days for the largest systems. However, these timings assume that most of the system and building details required are available, which is rarely the case, especially for systems that are being inspected for the first time.
By taking care of some basic activities, the owner can significantly influence the quality and costs of the inspection and ensure they get the most benefit from the required inspections:
Information on the system and the building should be gathered and structured well in advance of the inspection to give the inspector a good overview on the system and prevent him having to search for documents while on site.
The inspector should be accompanied by an experienced and motivated member of the technical staff to answer questions, help with measurements and provide access to parts of the system that the inspector cannot touch for reasons of insurance. This will save time and significantly improve the quality of the inspection report and recommendations.
The implementation of an energy-monitoring system capable of recording the consumption at the level of the AC system components will not only increase the quality of the inspection recommendations and help to quantify (monetary) savings but it will also help the owner to achieve long-term reductions in energy consumption. The implementation of an electronic monitoring and control system could also inspection costs as the recast of the EPBD allows Member States to reduce the frequency or extent of the inspection if such a system is in place.
To support the inspector, a range of inspection-specific tools and materials has been developed within the Harmonac project. These should help inspections become more time- efficient and also provide useful recommendations on how to improve the energy efficiency of the system. The central tool developed is the CEN Standards-based inspection methodology, with each inspection item linked to potential energy-conservation opportunities and training material. Four simulation tools help to identify and quantify saving potentials.
The Harmonac database also allows inspectors to search all the reports of Harmonac field tests according to system and building types. This can help them in identifying potential energy-conservation opportunities for the systems they are to inspect.
* Harmonising air-conditioning inspection and audit procedures in the tertiary building sector
More information on the Harmonac project including tools and materials is available from the web site.