GUIDANCE NOTE 12 CHP SCHEE DESCRIPTION Refer to GN10 & GN11 for guidance on the influence of CHP Scheme boundaries on QI and Power Efficiency. ECONOIC SECTOR GN12.1 Applicants should enter the name of the sector that best describes the activity served by the Scheme (i.e. the recipient of the heat, not necessarily the CHP operator s core business sector) on Form F2 from the following list of classifications: Table GN12-1 Economic Sectors Iron and steel Chemical and pharmaceutical industry Paper, publishing and printing Textiles, clothing & footwear Vehicles ineral products (e.g. glass, cement, bricks) Construction Transport Public administration Health Defence Education Public sector housing Post Office Local or National Government Other public administration Other Horticulture anufacturing and Retail Timber Scientific Research Private Hospitals Royal Household Non ferrous metals Oil refineries Food, beverages and tobacco Electrical & instrument engineering echanical engineering and metal products Extraction, mining & agglomeration Other industrial branches Sewage treatment Horticulture Commerce Airports Hotels Sports and leisure ixed Community Heating Offices Other commerce CHP SCHEE LINE DIAGRA GN12.2 A CHP Scheme Line Diagram (see Fig GN12-1) showing the CHP Scheme and its relationship to the site as a whole is required. The diagram should include all the main plant items that lie within the CHP Scheme boundary, their interconnections, Final GN12-V3 CHPQA Guidance Note 12. Page 1 Crown Copyright 2014
and piping and cables carrying fuel and energy inputs, power and heat outputs (steam, hot water, or exhaust gas, as applicable). All lines should clearly indicate the fluid or service carried. In the case of steam and hot water, the notation should include the working pressure and temperature. CHP Boundary By-pass stack Exhaust stack Boiler feedwater 10 bar/180 C (sat) Steam to site Steam meter 4(FR) Electricity meter 3(EQ) Gas meter 1(FcQ) Gas compressor Gas turbine GT1 Supplementary burner Boiler HRB1(SF) To hot well Shell boiler FB1(NO) Gas oil meter 2(FQ) Fig GN12-1 CHP Scheme Line Diagram TAG NOTATION GN12.3 All main equipment items and metering stations should be identified on the CHP Scheme Line Diagram with simple Tag Numbers. Equipment Tags should consist of a simple prefix (as indicated below) followed by a number, e.g. GT1, GT2, ST1, HRB1. Where appropriate a suffix indicating the sub-type of machine should be added, e.g. ST1 (CO), ST2 (PO/CO), RE1 (G), RE2 (DF). Similarly, eter Tags should be 1(FcQ), 2 (TR) etc. Table GN12-2 Suggested Tag Notation Prefix Equipment type Suffix Sub-type GT Gas turbine RE Reciprocating (G) Gas engine engine (D) Diesel engine (DF) Dual fuel (HFO) Heavy fuel oil ST Steam turbine (BP) Back pressure (PO) Pass-out (PI) Pass-in (CO) Condensing Final GN12-V3 CHPQA Guidance Note 12. Page 2 Crown Copyright 2014
Prefix Equipment type Suffix Sub-type HRB Heat recovery (S) Steam boiler (W) Hot water (SF) Supplementary firing (AF) Auxiliary firing FB Fired boiler (NO) Normally operating (HS) Hot standby (CS) Cold standby FC Fuel Cell RGT Renewable Gas Turbine ORC Organic Rankine Cycle etering station (F) Flow / (Fc) flow (corrected) (E) Electric Power (H) Heat (T) Temperature (P) Pressure (An) Analyser (I) Indicator (R) Recorder (W) Weight (Q) Totaliser (C) Calculation CHP SCHEE ENERGY FLOW DIAGRA GN12.4 A separate copy of the CHP Scheme Line Diagram (see Fig GN12-2) should be marked up to show typical flow rates, heat outputs, and electrical and mechanical power outputs. Where there are different operating modes or significant seasonal or daily load variations, state clearly the case for which the data apply (e.g. winter average conditions). Final GN12-V3 CHPQA Guidance Note 12. Page 3 Crown Copyright 2014
CHP Boundary By-pass stack Exhaust stack Electricity meter 3(EQ) 5.0 W Gas meter Gas 1(FcQ) compressor 1800 m /h (=20.2 W) Gas turbine GT1 Supplementary burner Boiler HRB1(SF) Boiler feedwater 10 bar/180 C (sat) To hot well Steam to site Shell boiler FB1(NO) Steam meter 4(FR) 11.5 te/h (= 8.7 W) 0.0 litres/m Gas oil 2(FQ) Fig GN12-2 CHP Scheme Energy Flow Diagram HEAT PROFILES GN12.5 In order to determine QI axheat, all CHP Schemes with heat rejection facility should provide three graphs to illustrate the CHP Scheme s annual and daily heat output profiles. 1. The annual profile (see Fig GN12-3) should illustrate any seasonal variations in heat output using weekly or monthly average figures. 2. The daily profile (see Fig GN12-4) should show any day/night variations, weekday and weekends, reflecting production patterns or occupancy over the 24-hour period. 3. The heat load duration curve (see Fig GN12-5) should indicate the cumulative hours of heat output over a year (by plotting the number of hours when the heat output from the CHP Scheme is at or above a particular value). In the present context it would be more correctly called a heat output duration curve. If the data is not available an estimate of axheat will be required. Final GN12-V3 CHPQA Guidance Note 12. Page 4 Crown Copyright 2014
12 10 Average Heat Output, W 8 6 4 2 0 Jan Feb ar Apr ay Jun Jul Aug Sep Oct Nov Dec Fig GN12-3 Annual profile of CHP heat output 14 12 Winter Weekdays Summer Heat load, W 10 8 6 4 2 Winter Weekends/holidays Summer 0 00:00 02:00 04:00 06:00 08:00 10:00 12:00 Time 14:00 16:00 18:00 20:00 22:00 24:00 Fig GN12-4 Daily profile of CHP heat output Final GN12-V3 CHPQA Guidance Note 12. Page 5 Crown Copyright 2014
50.000 45.000 40.000 Scheme useful Heat Output (Wt) 35.000 30.000 25.000 20.000 15.000 axheat =21Wt ie heat demand>=21wt for 1000 hours of the year 10.000 5.000 0.000 0 1250 2500 3750 5000 6250 7500 8750 Fig GN12-5 Load duration graph (hourly data) Developing a Heat Load Duration Curve and determination of axheat The heat load duration curve (Fig GN12-5) is required to accompany the F2 submission and, more importantly, if in any particular Self-Assessment year the scheme fails to meet its Quality Index Threshold and the Qualifying Power Capacity (QPC) has to be scaled back from the Total Power Capacity (TPC) figure. It is used to derive the axheat value for the scheme at Normal Operating Conditions (NOC), so that the Quality Index (QI) can be recomputed at axheat conditions. For some schemes, the heat load duration curve only needs to be produced once, as the ax Heat value and the associated power and heat efficiencies may not change at NOC. However, there are situations where it will be necessary to produce another heat load duration curve:- Where the heat demand changes due to changes in process operation Where a prime mover has been removed from the scheme boundary, or another has been added Where a fully or partially condensing steam turbine is contained within the scheme boundary there may be trading off between heat and power; consequently, the ax Heat (and the associated scheme efficiencies) could change year on year. The heat load duration curve may be derived without difficulty within a simple spreadsheet providing that heat output data, (determined at regular time intervals), are available, together with the associated fuel inputs and power outputs. Ideally, half-hourly or hourly data should be used, but if these are not available daily or even weekly data may be adequate. Hours Final GN12-V3 CHPQA Guidance Note 12. Page 6 Crown Copyright 2014
Using the spreadsheet, sort the data into descending order of heat output (in Wth) and plot heat output against cumulative hours,. axheat (defined in the CHPQA Standard) is the heat output that is equalled or exceeded for a given number of hours in a year (1000, 750 or 500 hours depending on the use of the heat outputs from the CHP scheme). axheat value may then be determined from the graph. In order to determine the power and heat efficiencies at axheat conditions the fuel input and power output that best correspond to axheat need to be estimated. For some schemes, particularly those that include steam turbines, there may be many combinations of fuel inputs and power outputs that can result in the axheat heat output. The best strategy is to plot energy input (Y-axis) versus heat output (X-axis) and draw a smooth curve through the data points (e.g. a second order best-fit polynomial if doing this within the spreadsheet) and select the energy input that corresponds to the axheat heat output. Similarly a plot of power output versus heat output will reveal the power output that best represents axheat operation. Refer to GN 27 for guidance on the application of the ax Heat and related data for determining QPC. CHP SCHEE EQUIPENT GN12.6 All prime movers (including secondary steam turbines, see GN16.9) and boilers within the CHP Scheme boundary, should be identified and details provided, including: Tag Number anufacturer odel or type aximum rated power and/or heat outputs at ISO conditions Year commissioned Where a prime mover drives a mechanical load (e.g. a pump or a compressor) the mechanical power output should be converted to an equivalent electrical output using a multiplying factor of 1.05. Heat outputs for steam turbines should be based on the maximum pass-out and/or back-pressure steam flow rates. CHP Scheme onitoring Equipment Arrangements GN12.7 A list of all metering equipment that will be used to monitor the performance of the CHP Scheme is required, including heat and electricity export meters. This should also include details (including the eter Point Reference Numbers) of all gas supply billing meters, even if the CHP Scheme is supplied via a secondary meter. eters should be identified by tag numbers, and details of each meter must be provided, including: Tag number Serial number (and, where applicable, meter point reference number or other unique billing identifier) Year of installation anufacturer (of primary metering device), model and type Final GN12-V3 CHPQA Guidance Note 12. Page 7 Crown Copyright 2014
etered service and line conditions (fluid temperature and pressure, electricity voltage, e.g. steam (42 bara/400 o C), electricity (3.3 kv)) eter output range (except for electricity meters which should be entered as N/A - not applicable), i.e. the minimum and maximum rate of flow (Qmin and Qmax for fluid flow meters). Not the maximum reading on a totaliser (e.g. 999999). eter output units (state if corrected for temperature and pressure) Uncertainty as a percentage of reading or percentage of output range. What is required here is the basic meter/transmitter/computer uncertainty only, excluding any additional uncertainties for excessive intervals between calibrations (which may change each year). Refer to GN13 for guidance on Scheme monitoring GN12.8 The assessment of the uncertainty of metering equipment is important, and where appropriate, supporting calculations shall be provided. Refer to GN17 for guidance on Uncertainty in etered Inputs and Outputs. GN12.9 Where a CHP Scheme s existing monitoring arrangements do not comply with the requirements set down in the CHPQA Standard (see GN 14,15 and 16) applicants are required to provide information on the additional metering that applicants propose to install and, where applicable, details of any indirect methods to be used to derive unmetered inputs and outputs. GN12.10 Where an indirect method is proposed, in order to derive an unmetered input or output, details of the proposed method and an assessment of the resulting uncertainty are required. Details of any metering equipment upon which the indirect method relies should be included in the list of meters in FormF2, Section 5. Refer to GN20, 21 & 22 for guidance on indirect determination of energy inputs and outputs. Refer to GN18 for guidance on Uncertainty in Calculated Energy Inputs and Outputs. GN12.11 Where inadequate, or no, metering is in place for measurement of steam or heat outputs, unmetered heat is discounted and should not be included in the Qualifying Heat Output. Final GN12-V3 CHPQA Guidance Note 12. Page 8 Crown Copyright 2014
GN12.12 etered or derived inputs (from metered values) that have uncertainties greater than the threshold shall have correction factors applied when calculating scheme efficiencies. Refer to GN13.10 & 14 for guidance on Energy Inputs. Refer to GN19 for guidance on Adjustment of Energy Inputs and Outputs for Excessive Uncertainty. GN12.13 etered or derived outputs (from metered values) that have uncertainties greater than the threshold shall have correction factors applied when calculating scheme efficiencies. Refer to GN13.10, GN15 & GN16 for guidance on Energy Outputs. Refer to GN19 for guidance on Adjustment of Energy Inputs and Outputs for Excessive Uncertainty. CHP SCHEE CAPACITY GN12.14 A CHP Scheme s performance can be described in two ways: CHP Total Power Capacity (CHPTPC): the registered maximum power generation capacity of the CHP Scheme (We ), at ISO conditions. It defines the size of the CHP Scheme for the purpose of selecting the appropriate Quality Index formula.. Where there is more than one electrical generator in a Scheme, CHPTPC shall include the total electrical capacity of all generators that can run together, i.e. the actual maximum generation capacity. Thus for a CCGT CHP Scheme with a 42We GT and a passout condensing ST capable of producing a maximum 13We (when in fully condensing mode) the CHPTPC = 42 + 13 = 55W e Where a Scheme includes mechanical power outputs, this shall be converted to an equivalent power output and included in CHPTPC. An example is given below: A site operates a CHP Scheme that includes a back-pressure steam turbine used to drive a process gas compressor. The steam flow and the turbine inlet and exhaust steam pressures and temperatures are all metered. Final GN12-V3 CHPQA Guidance Note 12. Page 9 Crown Copyright 2014
HP steam to turbine Flow, pressure and temperature Shaft power output Back pressure Steam turbine Load Exhaust steam Flow, pressure and temperature Since CHPQA requires reporting of monthly figures, this example is based on the operation over 1-month, but the same calculation may be carried out for other periods of time including instantaneous rates. etered data Steam flow to/from steam turbine (S) 14,400 tonnes HP steam pressure (monthly average) 41.4 bar(g) HP steam temperature (monthly average) 410 o C Exhaust steam pressure (monthly average) 3.45 bar(g) Exhaust steam temperature(monthly average) 190 o C Assumption Turbine mechanical losses = 3% Calculation of mechanical power Specific enthalpy of inlet steam (41.4 bar(g) / 410 o C) = 3,233.9 kj/kg (steam properties) Specific enthalpy of exhaust steam (3.45 bar(g) / 190 o C) properties) = 2,837.4 kj/kg (steam Specific heat drop (inlet minus exhaust) = 396.5 kj/kg / 3.6 = 110.1 kwh/tonne Total heat drop in period = 14,400 tonnes x 110.1 kwh/tonne / 1,000 = 1,585.4 Wh Turbine shaft output allowing 3% mechanical losses = 1,537.8 Wh Equivalent electrical output = 1.05 x 1,537.8 = 1,614.7 Wh (electrical) The Total Fuel for Generating echanical Power = Equivalent Electrical Output /CHP Scheme s Power Efficiency* *From CHPQA certificate Final GN12-V3 CHPQA Guidance Note 12. Page 10 Crown Copyright 2014
CHP Total Power Capacity axheat conditions (CHPTPCaxHeat): the total power generation capacity of the CHP Scheme (We ) under axheat conditions. It defines the CHP Scheme s capacity if delivering the maximum heat output under normal operating conditions. Refer to GN27.4 for guidance on calculating axheat conditions [applicable to schemes that do not achieve the QI threshold under long term annual operation and new Schemes that (based on design data) failed to achieve the QI Threshold]. ADDITIONAL EQUIPENT GN12.15 Certain additional items of equipment are necessary for the operation of a Scheme. Whilst the energy consumed by such equipment is excluded in the assessment of quality, items necessary for the operation of a Scheme do need to be identified in order to be included for assessment of certain fiscal benefits. Such items of plant include: Gas fuel handing equipment including gas compressors, or treatment equipment for sewage, landfill gas or syngas Fuel treatment or handling equipment, for solid, liquid or gaseous fuels. This might include pulverisers or shredders for coal or solid waste; fuel storage for gas or for liquid fuels; filter units, heaters to aid pumping and combustion of viscous liquids, fuel pumps; pyrolysis or gasification equipment; solid waste crainage and storage etc Start-up equipment so that a Scheme can start up, whether or not connected to the electrical network. Such equipment may include electric motors or batteries, and diesel engines Equipment necessary for export of electricity, including direct connections Equipment necessary for Scheme monitoring and reporting Plant necessary for supplementary or auxiliary firing not identified elsewhere, including combustion air fans for auxiliary firing, or for provision of top-up and back-up heat, grate cooling Treatment/handling equipment for feed-water, the water or steam network including de-aeration equipment, de-ionisation or water softening equipment, filtration equipment, pumps, fans, etc Treatment/handling equipment for any direct use of exhaust gas not identified elsewhere, such as dryers, etc Other motors, drives, pumps, fans, blowers, etc necessary to the operation of the Scheme Other electrical parasitic equipment Other mechanical parasitic equipment Other heat parasitic equipment Continuous Emission onitoring (CE) equipment Ash and FGT collection and disposal equipment. Final GN12-V3 CHPQA Guidance Note 12. Page 11 Crown Copyright 2014
These items of plant need to be listed in Form F2 Section 7, with the following details: Item; manufacturer; model; number installed; whether they are normally running, used at start-up, or used rarely; and an estimate of energy load consumption (kwe or kwth). For the purpose of recording kw demand, mechanical parasitic loads should be treated as equivalent electrical loads, refer to GN15.4 to15.6 & 22. SELECTION OF QI FORULA(E) GN12.16 It is necessary for the Responsible Person to identify the relevant QI formula from GN10 (v4)-based on the CHP Scheme applying for Certification. CHP Schemes that burn mixtures of fuels, should enter the separate QI formulas for each fuel and the QI formula will be weighted by the use of each see GN24.10 A number of formulas for special cases are also provided. Refer to GN10.7 for detailed guidance on QI formula(s). Refer to GN24.10 for guidance on mixed fuels. Refer to GN14.6 & 14.7 for detailed guidance on Recovered Heat. Final GN12-V3 CHPQA Guidance Note 12. Page 12 Crown Copyright 2014