Aspects of Energy use by UK Air Conditioning. Roger Hitchin, Andy Lewry, Christine Pout, Alan Abela and Lorna Hamilton. Part of the BRE Trust

Transcription

1 Aspects of Energy use by UK Air Conditioning Roger Hitchin, Andy Lewry, Christine Pout, Alan Abela and Lorna Hamilton Part of the BRE Trust

2 Preface - The Symposium paper is a summary of a study for DECC - To gather evidence to support policy analysis for a/c energy consumption - The presentation is a summary of the paper - The client presentation took 2 hours - So the presentation will only pick out highlights - Full details at - And/or ask me later - Opinions expressed are mine - not DECC s

3 Scope of Study: Principal Tasks Literature search Including grey literature from planned EEBPp a/c GPG Re-analysis of existing monitoring data from 32 offices Analysis of 200 Air-Conditioning Inspection Reports and data from the corresponding Energy Performance Certificates Development of an algorithm to extend DECC s product policy model to include peak and monthly electricity demand from airconditioning Extract UK potential energy savings from policy options from previous EU-wide BRE study

4 Contents Presentation of selected results is by theme rather than task Location and Extent of Air Conditioning System and Product Efficiencies Annual Consumption and Peak Power Some options for reducing energy consumption

5 Location and extent of air conditioning Estimated current market penetration by floor area is 65% for offices and 30% for retail. Recent values of total floor area (but not a/c) from Valuation Office Agency Installed cooling capacity estimated to be 250% of 1994 based on sales data Most recent detailed information is from 1994 BRE report Floor Area (1,000m 2 ) % change Factories 213,548 41,621-81% Offices 70, ,211 44% Shops 94,217 92,345-2% Warehouses 119, , % Main Building Types 497, ,357 9% Region (E&W) Air conditioned floor area in 1994 (1000 m2) Office Retail Warehouse East Anglia East Midlands Northern North West South East South West Wales West Midlands Yorks and Humberside

6 EPC data EPC and ACIR data support the view that office and retail are major sectors Similar cooled areas Many more retail premises Hotels the next largest sector A relatively small, unstructured sample Building Type Number of Buildings Floor Area (m 2 ) A1/A2 Retail ,313 A3/A4/A5 Restaurants & Cafes 32 20,522 B1 Offices ,660 B2/B7 Industrial 5 53,432 B8 Storage and Distribution 6 22,980 C1 Hotels ,255 C2 Hospitals and Care Homes 1 8,221 C2 Universities and Colleges D1 Libraries Museums and Art Galleries 1 2,351 D1 Primary Health Care 4 4,424 D2 General Assembly and Leisure 6 13,827

7 Product efficiency: technology Seasonal Energy Efficiency Ratio (SEER) is now the regulatory metric High SEER is obtained by improved part-load performance Best available chiller has SEER of 5.4 Extra cost about 30%? (But ductand pipe-work is the main cost element in large systems) Good seasonal efficiency depends on matching load frequency to part-load efficiency, rather than sizing per se.

8 Product Efficiency: products - European-level information from Eurovent on what was placed on the market - Availability of highefficiency products has increased - But little information on the which ones sold best

9 SEER values reported in EPCs 60% of reported values are defaults (in the range 2 to 3) Presumably where data are difficult to find (Triggers recommendation to consider replacement) ErPD requirements are in range 3.5 to 4.5 depending on product System efficiency of central systems is also affected by duct leakage, fan heat pick up etc (not recorded on EPC database) Only 24 recommendations to improve duct leakage Number of reported SEERs in range System type < 2 2 to 3 to 4 to > Active chilled beams 1 Chilled ceilings or passive chilled beams 2 2 Constant volume system (fixed fresh air rate) Constant volume system (variable fresh air rate) Dual duct (constant 1 1 volume) Dual-duct VAV Fan coil systems Indoor packaged cabinet 4 2 (VAV) Induction system 3 Single room cooling system Single-duct VAV Terminal reheat (constant volume) 1 Water loop heat pump 1 Split or multi-split system

10 Annual Consumptions: Calculated EPC values - offices Mostly chiller systems (some splits) ECON 19 benchmarks: Good practice 14 to 21 Typical 31 to 41 Cost-optimal for new office is 9 kwh/m2 All values relate to standard occupation and equipment use Variation is presumably from building design, mixture of activities, location, lighting or system efficiency System efficiency accounts for about 10% of variance

11 Annual Consumptions: Calculated EPC values - retail Mixture of splits and chillers Much wider range than for offices No benchmarks Heat gains from display lighting probably a factor System efficiency accounts for 50% of variance (Typical electricity consumption breakdown for hypermarket: Air conditioning 9% Refrigeration 29% Lighting 23%)

12 Annual Consumptions: Measured values for offices Measured consumptions include most system types, including splits Measured consumptions are generally higher than from EPCs Often higher than ECON 19 typical Includes effects of different occupancy levels and patterns real-life system performance

13 Measured (standardised) cooling consumptions Variability between systems greater than between system types One outlier unusual situation and use Chilled ceiling/beam perhaps lower (but may be in low load buildings) No obvious relationship to floor area Perhaps more variability for smaller spaces

14 Peak power and annual load factor Peak power often around 25 to 40 W/m2 Equivalent to cooling load of say 60 to 100 W/m2 BSRIA rule of thumb 75 W/m2 Chilled ceiling/beams have lower peaks and consumptions General trend for systems with higher consumption to also have higher peak power Ratio is annual load factor (EFLH)

15 Annual load factor (EFLH) EFLH shows less variability than annual consumption (coefficient of variation 40% lower) But small spaces are variable on either measure Observed EFLH values are high compared to published simulation results (typically well below 1000 hours).

16 Operational issues 32% of the monitored systems in the current study did not have appropriate operating times. 14% of monitored annual consumption was at weekends. Weekend system operation Operating (generally for weekday hours) Weekend occupancy 4 4 Not operating 4 7 No Weekend occupancy A European study (Harmonac) found substantial energy wastage from poor operation and maintenance. And inspections only identified a minority of the opportunities to save energy Cooling Savings potential 24% 37% 39% Fabric and equipment Plant O+M

17 Operation and Maintenance: Inspection reports - Inspection reports frequently mentioned controls and O+M issues - Over 80% of installations are reportedly well-maintained. - However, 25% of these have dirty or blocked filters, missing or damaged insulation, or faulty or out of order units. Frequency of recommendations Description Frequency Controls 27% Maintenance 16% Documentation 10% Staff training 10% Metering and Monitoring 8% Refrigerants 7% Equipment 7% Internal heat gains 4% System sizing 4% External heat gains 3% Renewable energy 2% Others 2%

18 Some options for reducing energy consumption Policy Option Advantages Disadvantages Product and system efficiency Minimum performance requirements - Already in place for <12kW, imminent for - Slow uptake reflecting product for cooling products >12kW. - Existing requirements may need - Direct impact on consumption tightening Minimum requirements for SFP and duct leakage Integrated minimum performance requirements for buildings and systems Minimum performance requirements for lighting and equipment Shading requirements for buildings Better operational practice: inspections and energy audits Incentives for implementing recommendations - Also impacts ventilation-only systems - In place through Building Regulations - Already in place (EPBD) - Allows designers to balance load reduction and system efficiency measures Load Reduction - Effective cooling load reduction measures - Already in place (for lighting products) - Already within scope of Building Regulations - Some measures applicable to existing buildings Operation and Maintenance - Potentially rapid impact - Building Regulations already require controls and sub-metering in new systems Generally - Accelerate energy saving - (Need to focus on measured consumption?) - Limited application as retrofit - Impact on a/c is indirect - Only applies to new and refurbished buildings - Most effective measures only applicable to new and refurbished buildings, so slow take up - Easily reversed - Current EPBD policy instruments (mandatory inspections) of doubtful impact - Unclear how to obtain significant traction

19 For more information: The main report will be on the DECC website The main report and all annexes are at