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the first step in energy management andrew ibbotson joe flanagan n.
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The first step in energy management Andrew Ibbotson Joe Flanagan

The first step in energy management Andrew Ibbotson Joe Flanagan

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The first step in energy management Andrew Ibbotson Joe Flanagan

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  1. Energy Survey Workshop The first step in energy management Andrew Ibbotson Joe Flanagan

  2. What is an energy survey? For a site, dept, or process • Establishes the energy cost and consumption • Is a technical investigation of the energy flows • Aims to identify cost effective energy savings • Examines both the technical and ‘soft’ management issues.

  3. Why carry out a survey? • Identify savings • Establish the viability of an energy management programme • Establish a ‘baseline’

  4. Identify where Energy is Used and Develop an Action Plan Survey Senior Management Commitment Measure Energy Consumption and Production Review Performance and Action Plan Develop Targets Implement Energy Saving Measures Produce Reports to Monitor Energy Use Against Output The Energy Management Process

  5. DIY or Consultant? Consultant • Expertise • Fresh pair of eyes • Should not be afraid to poke into any corner • Opinions may carry more weight • Job will be completed DIY • No cost • No learning curve • Projects should be viable

  6. Choosing a Consultant • Salesman or consultant? • Ensure he/she is experienced in your process • Don’t be afraid to take up references • Cost - day rate of fixed price

  7. The Survey Process • Define the scope • Establish energy balances • Identify priority areas • Identify energy saving projects • Low cost (control, housekeeping, awareness) • Medium cost (revenue expenditure <1 year payback) • High cost (capital expenditure <2-3 year payback) • Reporting

  8. How much effort is required? Depends upon • complexity of the site and scope • Level of detail available (esp. sub-meters) • Size and energy intensity • Rule of thumb • Up to €200,000 – 6 mandays • Up to €1,000,000 – 10-15 mandays

  9. Scope • Electricity, gas, oil, solid fuel etc • ?Water, effluent, industrial gases • In general further detailed study will be required for medium and high cost opportunities

  10. Energy Balances and Data Analysis • Last 12 months bills • Sub-meter readings • Principal energy users • Production and climatic data • 1st Law of Thermodynamics – energy can neither be created or destroyed

  11. Electricity Bills • Maximum Demand charges (kVA, kW) • Capacity charges (kVA, kW) • Day and night rates • Power factor

  12. kWh φ kVArh kVAh Power Factor PF = kWh/kVAh = cos φ From the electricity bill kWh = 17,400 kVArh = 8,700 What is the power factor?

  13. Power factor tan φ = 8,700/17,400 = 0.5 φ = 26.5º cos 26.5 = 0.89 PF improved by adding capacitors Worthy of further investigation below 0.85-0.90

  14. Gas Bills • More frequently estimated (in the UK) • Errors more prevalent • Very rarely obtain ½ hourly demand • Can obtain some useful energy management information

  15. ‘Base’ or process gas load

  16. Electrical Balance • Sub-meters help – but rarely provide all the required information • Need to list major electrical consumers (pumps, fans, compressors, chillers, lighting, process heating etc) • Need rating and running hours

  17. Estimating Electricity

  18. Design kW = rating on equipment e.g. plate rating of a motor; wattage of a bulb Estimating Electricity

  19. Actual kW = best estimate of actual power e.g. based on ammeter reading or design data Estimating Electricity kW = √3*V * I * PF

  20. Load factor allows for variable load e.g. air compressor on load / off load Estimating Electricity

  21. Total should = metered total either for whole site or for a sub-meter Estimating Electricity

  22. Estimating Electricity • High accuracy is time consuming • ±10% is very good • Portable data logger useful for large users • Don’t underestimate the large number of small users e.g. conveyors, fans, pumps

  23. Electricity Balance

  24. Fuel Balances • Process vs. space heating from a year of monthly or weekly data • Difficult to estimate the distribution among process users if there is no metering • Most gas process plant will operate well below MCR – manufacturers specification • No portable gas metering

  25. Could CHP be feasible? • Power demand >500 kW • Coincident heat (steam or hot water) demand? • Heat to power 3:1 • High operating hours > 2 shift 5d/week

  26. Benchmarking • Comparison to a published benchmark often seen as method for estimating savings • Treat with caution • ‘best practice’ often refers to ‘state of the art’ • Utilisation has a large influence • Generally confirms what you already know • Greatest validity for ‘basic’ industry – metals, ceramics, glass etc.. • Lots of information at www.actionenergy.org.uk

  27. Boilers & Steam Systems

  28. Scope

  29. Basic Combustion Process Natural gas 8N2 + CH4 + 2O2 CO2 + 2H2O + 8N2 Plus the release of ~10 kWh/m3 of CH4 10 volumes of air required for 1 volume of methane

  30. Heat Recovery Process Gas Passes - convection Burner Furnace Tube - radiation

  31. Exhaust (~20% on gas, ~16% on oil) Convection & Radiation (1% to 1.5% @ max continuous rating (mcr)) Air & Fuel Blowdown (<5%) Boiler Losses Convection proportional to T Radiation proportional to T4

  32. Combustion Losses • heat loss in flue gases • Latent heat of water vapour in flue gases • incomplete carbon combustion • ‘Excess’ air must be kept to a minimum • Generally at least 10% excess is required to ensure good combustion • Combustion losses depend upon volume and temperature of flue gases

  33. Excess Air • measured by inference from O2 in exhaust or level of CO2 in exhaust • Portable instrument (measures O2, temp and CO • Permanent zirconia probe in stack linked to air/gas valves (oxygen trim)

  34. Best Boiler Efficiency • optimised fuel / air ratio well insulated (shiny surface) • clean burner nozzles • clean boiler surfaces • minimum steam pressure / temperature • reasonable load (~80%) • optimised TDS controlling blowdown

  35. Combustion • 1% efficiency increase, 79% to 80% savers 1- 0.8 = 1.25% fuel • reduction of 02 by ~2% • reduction of exhaust temperature by ~20ºC • oxygen trim control; 1% to 1.5% on well adjusted boiler • Air preheat (duct from air compressors or boilerhouse) saving 0.5% to 1%

  36. Blowdown • maintaining recommended TDS levels ensures clean heat transfer surfaces • operating low TDS waste energy, water, chemicals and increases effluent costs • heat recovery (for large boilers payback 2-3 years)

  37. Other • check optimum load on boilers • rank multiple boilers to operate the group with minimum loss • Shutdown Loss Minimisation • gas side isolation with dampers • water/steam side isolation with crown valve

  38. Heat Recovery • economiser (to feedwater) • recuperator (to wash water)

  39. Insulation • check existing quality • insulate all hot pipework, flanges (1m pipe), valve bodies (5m pipe) • hotwell cover and insulation

  40. Key Points for the Boiler House Check • Boiler efficiency • Blowdown procedure • Condensate return • insulation

  41. The Nature of Steam Item Heat Content KJ/kg % Latent at 7 bar g 2050 74 Flash at Atmospheric from 7 bar g 300 11 Condensate at Atmospheric 420 15 Total 2770 100 Breakdown of heat content of 7 bar g saturated steam

  42. System Standing Losses Fixed loss from: • Pipework • Valves • Fittings etc. Losses range from 2% to 5%

  43. System Variable Losses Flash and % losses with steam at condensate ? bar g & cond. at 0 bar g return 7 5 3 0 Total loss 26 24 22 15 50% cond. return 19 17 15 7

  44. Management Control • Automatic isolation systems • Pressure reduction • Energy management: • Metering • Data analysis • Action

  45. Fixed Losses • Insulation • air ingress • steam leaks