Energy Conservation

1. Energy Conservation Energy Management

2. Role of an energy manager • Assess • Current energy demand • Energy audit • Analyse • Energy requirements • Advise • On technical improvements • Advertise • Ways to save energy • Account • For energy consumption

3. Assess energy demand • Keep records • Consumption • Time of readings • Temperature • Other factors affecting demand • Weekday/weekend • Special events • Frequency of readings • Weekly • Daily

4. Energy Audit • Feasibility study • Establish and quantify energy flows into and within a building or organisation • Aim • Identify viable and cost effective energy saving measures • Enhance operating efficiency and reduce maintenance costs • Establish a baseline energy consumption • Process • Collect data from energy invoices and meters • Surveys of plant, equipment and buildings • Collect information from managers and other staff

5. Auditing process • Identify energy management opportunities • Can be ‘no cost’ or ‘low cost’ measures • Change an energy tariff • Change an energy supplier • Reschedule production activities • Preferential tariffs • Adjust existing controls to match requirements • Implement ‘good housekeeping’ policies • Invest in small capital items • Thermostats & time switches

6. Who does energy audits? • Can be undertaken internally – energy manager • Specialist energy consultants • Energy service companies • Performance contracts • Guarantee organisations energy cost savings in return for a fee • Main interest is in installing and managing their recommended plant • May arrange finance of projects • Vested interest

7. Why is energy wasted? • Poorly designed buildings and installations • Insufficient insulation • Undersized ventilation ducts • Inadequate control systems • Poor control settings • Inefficient plant operation • Out of date technology • Poor maintenance • Poor operating and working practices

8. Different types of energy audit • According to level of detail and depth of analysis • Preliminary • Targeted • Comprehensive

9. Preliminary audit • How much energy is being consumed • What type of energy • Performance of facility compared with similar facilities • Characteristic performance of building

10. Preliminary energy audit • Identification of potential areas of energy saving • Financial energy audits • Collect data • Establish quantity and cost of each form of energy • Data from energy invoices and meters for previous year • Analyse data • Present data • Establish priorities • Make recommendations

11. Targeted energy audit • Provide data and analysis on specific targeted projects • e.g. heating of one building or lighting • Detailed survey of target area • Analysis of energy flows and costs • Recommendations for action

12. Comprehensive energy audits • Similar to preliminary audits but in far more detail • Detailed data on energy flows into and within organisation or facility • Often requires use of sub-metering to accurately determine component energy flows • Or estimate energy use • (Plant power output (kWh)/efficiency of plant) *operating hours per year • Use of thermal imaging • May use complex energy simulation software • Detailed energy survey • Energy project implementation plans

14. Collect data • Build up picture of pattern of energy consumption and cost from energy invoices • All invoices for relevant time period • Delivery notes for oil, solid fuel, LPG • Identify estimated meter readings – check with previous years • Inadequate/unavailable invoices – contact utility company/fuel supplier • Collect geographic data • Location, altitude, orientation • Weather data, degree day data • Manufacturing data (if appropriate) • Production output • Check data for anomalies • Small building using more energy than larger one • High energy use at night when unoccupied

15. Understanding invoices: electricity • Date of meter reading • Monthly standing charge • Present and previous meter reading • Daytime – peak rate • Night time – off-peak rate • Charges for each rate • Some tariffs have a higher unit charge for first 1000 kWh • Monthly maximum demand charge • For every kW of the peak power demand during the month • Penalise users make heavy demands during peak periods • Supply capacity – annual maximum demand • Monthly charge • Total cost + VAT

16. Gas invoices • Much less complicated than electricity • Date of meter reading or estimate • Calorific value of gas • Present and previous meter readings • Amount of gas used • ft3, kWh or therms • Unit price per kWh • Standing charge • Monthly or quarterly • Total cost + VAT

17. Other fuels • Fuel oil • Measured by volume • Varies with temperature corrected to standard condition of 15.50C • Date of delivery • Unit cost per standard litre • Calorific value (?) • Total cost + VAT • Solid fuel • Weight delivered • Date of delivery • Total cost + VAT • No calorific value

18. Analysing energy records • Key variables • Heating • External temperature - dominant • Wind speed ) • Humidity ) <=10% variation • Solar gain ) • Lighting • Hours of darkness

19. Data analysis Many different ways of analysing data • Annual energy consumption • Analysis of heating requirements • Degree day method • Mean temperature method • Cumulative deviation method • (Details in Keith’s lecture notes) • Normalised performance indicators (NPI) (Beggs, 2002) • Time dependent energy analysis • Linear regression analysis • CUSUM – cumulative sum deviation method

20. Annual energy consumption • Simplest analysis • Assess overall energy performance of building • Produces a percentage breakdown of annual energy consumption and cost data • Convert all energy consumption data into standard units (kWh) • Standard conversion factors & gross calorific values • Percentage breakdowns of total consumption and cost of each energy type • Present data • Total annual energy consumption • Cost • Percentage breakdown of each fuel type • Historical trends

21. Analysis of heating requirements • Degree day method • Quicker • Oil & coal heating difficult – general estimates of consumption • Mean temperature method • More accurate • Plot mean consumption against mean external temperature

22. Degree day method Two component parts • Temperature related • Independent of temperature • Hot water & cooking if by gas • E = W + H*degree days*86400 • Where E is total energy consumed • W energy for hot water + cooking (gas) • W approx constant for given house – 7-10 GJ/quarter • H is heat loss rate for the home • Two unknowns W & H, • Know degree days & energy consumption • Estimate heat loss & steady energy requirement

23. Degree day method - example Energy consumption 2 successive quarters • 31.76 & 18.80 GJ Corresponding degree days • 1100 and 500 E = W + H * degree days*86400 1100 * H * 86400 + W = 31.76 (1) 500 * H * 86400 + W = 18.80 (2) Simultaneous equations (subtract 2 from 1) H = (31.76 – 18.80) * 109 = 250 Watts (1100-500)*86400 Substitute for H in either equation to get W W = 31.76 * 109 - 1100 * 250 * 86400 = 8 * 109 = 8GJ H - heat loss W - hot water

24. Degree day method Once H & W have been calculated • Performance for subsequent quarters can be estimated • If degree days for 3rd quarter = 400 • Consumption predicted to be • 400 * 250 * 86400 + 8 * 109 = 16.64 GJ • If actual consumption is 17.5 GJ then energy has been wasted

25. Mean temperature method (non electrical heating) • Plot the mean consumption over a specific period against mean external temperature • For 1 week or 1 day - less time than previous method

26. Analysis of lighting (non-electrically heated house) • Lighting varies throughout the year with hours of darkness • Need to assess a realistic time for lighting • There is constant load (A) from appliances and refrigeration use and an increasing amount from lighting. • Increase in lighting hours is used to obtain L & A in same way for H & W in heating example

27. Analysis of heating & lighting in an electrically heated house • More complex as both H & L are unknown • Combine A & W to give overall appliance + hot water load (A) • E = (degree days * H + lighting hours * L) * 86400 + A • Where E = energy consumption • H = heat loss rate • L = lighting (units of L are Watts per hour) • A = appliance + hot water • 3 unknowns – H, L & A • If we have data for 3 quarters • Estimate values for H, L & A by solving 3 simultaneous equations • If appliance load is known calculation is easier

28. No energy conservation – horizontal line Winter following improved insulation Summer – no savings – heat conservation only Winter – parallel to 2 Summer - improved management of hot water Should be (4) + (5) but less - energy conservation performance is reduced Cumulative deviation method

29. Normalised Performance Indicators (NPIs) • Provides an indication of the energy performance of a building • Compares actual annual energy consumption and costs with those achieved by buildings of a similar type and function • Problems • Buildings may be different sizes • Locations may have different climates • Locations may have different levels of exposure • Maybe different operating hours • Correct the building energy consumption data • allow for variables such as occupancy and weather. • NPIs developed to address these problems. Used to • compare with other buildings of a similar type and function • compare with standard energy benchmark for different building types • Benchmarks • Many countries have national energy benchmarks for different types of buildings • Usually kWh/m2 of floor area (volume) • Provide guidance, not absolute values to achieve

30. How to calculate NPIs • Establish total building energy use in standard units • Calculate the annual energy use for space heating • Sub-metering, or analytical techniques • Correct space heating energy data for climate & exposure • Weather coefficient = std annual heating degree days/ annual heating degree days experienced by building • Exposure coefficients • Sheltered (city centre) = 1.1 • Normal (urban/rural) = 1.0 • Exposed (coastal/hilly site) = 0.9 • Non-heating energy consumption + corrected space heating = non-time corrected energy consumption • To calculate normalised annual energy consumption need to correct for ‘hours of use’ • non-time corrected energy consumption * coefficient • Hours of use coefficient = std annual hours of use/actual annual hours of use • NPI = normalised annual energy consumption/building floor area

31. Energy Surveys • Integral part of energy audit • Helps to understand energy flows within a facility/building • Helps to identify energy wastage • Can be comprehensive or targeted • Objectives • Determine energy performance of facility/building or specific plant/equipment • Identify and quantify the principal energy flows & energy cost savings • Produce costed recommendations to achieve energy cost savings • Make recommendations on future energy management of facility

32. What to include in an energy survey • Management and operation characteristics of a facility or organisation • Energy supply to an organisations various facilities • Energy use within an organisations facilities • The plant and equipment within a facility • The fabric of the organisation’s buildings

33. Management and operating characteristics • Management culture • Can have considerable influence on energy consumption • Determine management structure and practices relating to energy procurement and consumption • Identify cost centres • Are the managers accountable for operating costs also responsible for energy consumption? • Maintenance procedures • Frequency and quality • Identify new maintenance measures to improve energy efficiency

34. Operating practices: data collection • Use of particular space or building • Mechanical/electrical services in building • Number & type of occupants e.g. stationary or active • Occupancy patterns • Environmental conditions • Air temp, humidity, lighting • Operating practices of plant/equipment • Identify where actual practices deviate from that stated by management • Overheated rooms, open windows, computers left on

35. Energy Supply • Identify tariffs and supply contracts of organisation • Ensure organisation is using correct electricity tariff to suite its load profile • Calculate load profile • Regular meter readings – include daytime, night time & weekends • For large electrical loads • Need to be more accurate • Measure every 30 mins, use portable meters if necessary • Investigate large peaks in load

36. Plant and equipment • Survey major items of plant and equipment to determine their operating efficiency • Include pipe distribution networks • Boilers • ‘tune’ to minimise flue gas heat loss • Identify if flue gas heat recovery is feasible • Refrigeration • Check efficiency • Opening practices • Is heat recovery feasible • Pipework • Insulation & leaks • Planned replacement of old plant Building fabric • Identify using U values areas of greatest heat loss • Thermal imaging • Excess ventilation – open doors

37. Energy management: recommendations • Recommendations will relate to cost of fuel – more interested in saving money than energy/carbon • Technical • Insulation, draft exclusion, thermostatic radiator valves, heating control • Low energy lighting, efficient refrigeration • Power factor corrections • Relocation of switches, movement sensors • Energy management • Checking performance • Record keeping • Financial • Make sub-sections responsible for their own energy budget • ‘Carrots’ for those who save energy • Other factors • Change patterns of working • Working practices • Use of space