CASE STUDIES OF AC SYSTEM ENERGY AUDIT

1. Field Monitoring of Air Conditioning Systems in the Tertiary Sector: Experiences in ItalyMarco Masoero – Politecnico di Torino • CASE STUDIES OF AC SYSTEM ENERGY AUDIT • One of the goals of the AUDITAC project has been to collect and organise into a data base successful Case Studies of AC system energy AUDITS • The available information on such audits has proved to be limited in all participating countries, particularly as far as the actual energy consumption data are concerned

2. PROBLEMS ENCOUNTERED (1) • The main energy input for AC systems is the electricity used by the motors that drive refrigerating compressors, fans, and pumps • Generally, electrical energy is centrally metered at the grid interface (main delivery board) without separating the individual users (i.e., lighting, appliances, AC, etc.) • Most energy service contracts include AC systems, but electricity bills are generally paid directly by the building owner / tenant • Consequently, no real reasons exist at present for implementing a costly and relatively complex procedure of gathering disaggregated electricity use data

3. PROBLEMS ENCOUNTERED (2) • Most AC system retrofits carried out in the past (at least in Italy) were determined by reasons different from energy conservation, namely: • Improving the comfort condition in work spaces • Solving IAQ problems, or complying with compulsory regulations on air changes (e.g. in hospitals) • Replacing room air conditioners with a central HVAC system to overcome maintenance problems and to avoid excessive differences in indoor environmental conditions

4. PROBLEMS ENCOUNTERED (3) • For space heating, the Heating Degree-Day (HDD) method has been firmly established since decades as a simple and reliable means for correlating energy consumption and local climate • Standard methods for AC energy data analysis are not as well known and established in the professional community

5. CASE STUDIES FOR ITALY • Three case studies are presented: • Hospital in NE Italy: air conditioning of a surgery / nursing department • Hospital in NW Italy: retrofits of existing refrigeration equipment • Water-to-water heat pump system for a small Auditorium

6. CASE STUDY No. 1 Surgery / nursing department: • Air-conditioned floor area 350 m2 • Two identical AHUs each with: • 9700 m3/h air supply (100% outdoor) • 8800 m3/h extraction • Fan power: 11 kW supply, 4 kW extract • Intermediate-fluid heat recovery The energy analysis has been focused on optimising the operation of the Air Handling Units

7. Monitoring campaign data (June-September 2006): • Electricity consumption of the heat recovery loop circulation pump • Air and water temperatures (16 sensors)

8. Heat recovery type A B Δ (B–A) Recovered thermal energy (kWh) 2955 7819 4864 Chiller electrical energy savings (kWh) 1477 3910 2433 Pump electrical consumption (kWh) 389 0 -389 Net electrical energy savings (kWh) 1088 3910 2822 Heat Recovery data analysis: • Measured average effectiveness of the existing recovery system: 58% (A) • Estimated effectiveness of an air-to-air recovery system: 65% (B) Seasonal savings with existing recovery system: 300 € (A) Seasonal savings with air-to-air recovery system: 500 € (B)

9. Free cooling YES NO Δ Δ(%) Cooling energy (kWh) 48075 57079 9004 16% Chiller electrical energy (kWh) 24037 28539 4502 16% Free cooling with outdoor air: • Free cooling by direct supply of outdoor air (without mechanical cooling) is assumed feasible when Tout < 20°C • Estimated energy savings

10. CASE STUDY No. 2 Retrofits of existing refrigeration equipment: • No cooling foreseen at time of hospital construction (early 1960s) • 15 chillers installed were needed • Retrofit work includes: • New water loop connecting the units • Two new chillers (963 kW cooling each) Several different strategies of refrigeration units management (including recovery of condensation heat) have been analysed

11. Partial replacement of existing chillers with the new ones

12. Recovery of condensation heat for SHW production: Economic analysis (Net Present Value)

13. CASE STUDY No. 3 Monitoring of a water-to water heat pumpfor a small Auditorium: • Air-conditioned floor area 300 m2 • Fan-coil + primary air (3200 m3/h) HVAC • Heat Pump cooling power 68 kW @ 7-12°C • Heat Pump heating power 60 kW @ 40-45°C • Heat source / sink: lake water

14. AHU SECONDARY CIRCUIT FAN COIL PRIMARY CIRCUIT HEATPUMP TO LAKE FROM LAKE • Heat Pump / HVAC System Scheme

15. BEMS

16. Monthly average Heat Pump C.O.P. vs. outdoor temperature

17. Cooling energy vs. air temperature, air specific humidity and air enthalpy

18. Conclusions (1) • The implementation of EPBD’s article 9 may offer a unique opportunity to promote effective energy savings policies in building air conditioning • In order to transform this opportunity into a real market, several technical and institutional barriers still have to be overcome: • National legislations must provide clear guidance on AC inspection, in terms of timing, methodologies, reference standards, official inspecting bodies , etc. • Incentives should be adopted in order to promote energy service contracts including clauses that – similarly to what is already customary in space heating – remunerate electrical energy savings in summer air conditioning

19. Conclusions (2) • Technical standards, accepted by the professional and scientific community, are needed both for the calculation of summer AC energy and for the evaluation of ECOs • Provisions for disaggregated electricity use metering should become customary in new installations and incentives for retrofitting the existing one should also be introduced • To overcome these barriers, a concerted action will be necessary in the coming years involving, at the Community level, more EC funded research and CEN activities, and, at the National level, an effort to complete the implementation of the EPBD to include summer air conditioning.