RETSCREEN: An evaluation tool for renewable energy projects and GHG emission estimation Dr S. Kumar Energy field of study Asian Institute of Technology CD 4 CDM Workshop, Siem Riep, Cambodia March 24 -26, 2004 1
Energy Project Implementation Process Pre-feasibility Analysis Feasibility Analysis Development & Engineering Construction & Commissioning • Important challenge – identification of projects for CDM • A simple tool for conducting pre-feasibility studies (renewable energy and energy efficiency projects): RETScreen • Development of project and including GHG emission reduction estimation 2
Presentation Overview • About Retscreen • How to use it: – To evaluate RE projects (electricity) – What it will provide – Advantages and limitations – Details using PV example – Energy model – GHG emission model – Inputs and Outputs 3
About Retscreen • To promote the deployment of renewable energy systems by building the capacity of planners, decision-makers and industry. • RETScreen International Renewable Energy Project Analysis Software was developed by Natural Resource Canada (CANMET Energy Technology Centre, Varennes) in collaboration with many Canadian institutions and international organisations (NASA, UNEP-DTIE), GEF’s SANET and WB’s PCF) 4
About Retscreen • RETScreen International Renewable Energy Project Analysis Software is now being used by more than 30, 000 people in 196 countries around the globe and which is growing at 200 new users every week. • Provides a common platform for both decision-support and capacity-building purposes. • Used to evaluate the energy production, life cycle costs and greenhouse has emissions reduction for various RETs. 5
Why Use RETScreen? • Simplifies preliminary evaluations – requires relatively small amounts of information – calculates key parameters automatically – Only 12 points of data (monthly) for RETScreen® vs. 8, 760 for hourly simulation models • Cost of analysis is very low as compared to other assessment methods • Standardized procedures allow objective comparisons • As a tool for understanding/building capacity of persons on RET project development 6
RETSCREEN: Salient Features • Covers 8 technologies: – Wind energy – Small hydro – Photovoltaics – Solar air heating – Biomass heating – Solar water heating – Passive solar heating – Ground-source heat pumps • Based on Microsoft Excel • • spreadsheet Easy-to-use and no need for any knowledge of any special computer program Contains detailed user manual & supporting databases Freely downloadable from www. retscreen. net Available in both English & French 7
Renewable Energy Electricity Generating Technologies covered by Retscreen Photovoltaics Small Hydro Photo credit: Vadim Belotserkovsky Photo credit: SNC-Lavalin Wind Energy 8 Photo credit: Middelgrunden Wind Turbine Co-operative
RETSCREEN Home page www. retscreen. net Download 9
The choice is yours…. • Choose the module • Download • Install 10
Or, you can download all…. • For each RE type, an individual icon is available • Click on the icon that you want to use SAH-Solar air heating SWH- Solar water heating PV- Photovoltaics GSHP – Ground Source Heat Pump PSH – Passive solar heating WIND HYDRO BIO – Biomass heating 11
Common Platform: Five key worksheets • Energy Model worksheet • Sub-worksheet (Solar radiation and Load calculation) • Cost Analysis worksheet • Greenhouse Gas Emission Reduction Analysis (GHG Analysis) worksheet • Financial Summary worksheet 12
RETSCREEN Colors and Codes Output white Input blue grey yellow • The user enters data into "shaded" worksheet cells only. All other cells that do not require input data are protected. • Choose from drop down list, Choose from database and key in data 13 • "blue-underlined" hyperlinks built into the worksheets.
Photovoltaic Project Analysis: Energy and GHG emission reduction Model 14
Energy Model … Energy worksheet contains the following main sections: • Background Information • provides project reference information, eg. location • SR and SLC • provides a description of the radiation estimation and other meteorological data • Product information • provides a description of product information • Energy model output Summary • provides a summary of the annual energy output, collector area, yield, etc 15
® RETScreen PV Energy Calculation • Annual analysis • Uses monthly solar resource • 3 types 16 © Minister of Natural Resources Canada 2001 – 2002.
Energy Model (details) • Site Conditions • Project name & location: Define a project name and its location for reference purposes only. • Nearest location for weather data: Enter the weather station location. Go to SR&SLC worksheet and fill up the “Site latitude and PV array orientation” section. This can also be done automatically by selecting the nearest weather station location. • All the other inputs of this section are automatically done when the SR&SLC sheets is 17 completed.
Energy model worksheet: Site Conditions 18
Energy Model • SR&SLC • To estimate the solar radiation at project site, information estimation of load. on collector and • It is similar for SWH, SPH and SAH (for radiation). • The load characteristics requires data for off grid, on grid or water pumping. • Load can be short or detailed (user’s choice) 19
SOLAR RADIATION and other meteorological INPUT • Requires monthly average values only • Necessary for all SWH, SAH, PSH and PV modules. • Three options: – User input data – Use RETSCREEN data base (country/location) – Link with NASA website • Key in latitude and longitude (or) Choose the location graphically • Zoom facility available • Also wind speed data and ambient temperature available 20
Energy Model: Solar Resource worksheet From data bases Data key in Output 21
NASA data base 22
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Zoom to choose the location 24
Finalize the site 25
Choose the RET 26
Data tables 27
Energy Model: Load Characteristics Load data Note the colours Output of the model 28
Energy Model System characteristics • Application type: This information is taken automatically from the SR&SLC sheet (off grid, on grid or water pumping). • PV system configuration: Select the option (drop down list) • Base Case Power System: • Source: Select the source of energy used prior to the use of PV system • Fuel type: Select the type of fuel has been displaced by the introduction of the PV system. • Specific fuel consumption: For natural gas fuel this quantity is expressed in m³/k. Wh and for other fuels, in L/k. Wh. For help see the table. 29
Energy Model … Ø Power Conditioning: • Suggested inverter (DC to AC) capacity: The model calculates and suggests the capacity of the inverter, in k. W AC • Inverter capacity: Enter the inverter capacity, in k. W AC (that is, the nominal output of the inverter). The entered value should not be lower than suggested. Zero should be entered if the PV system has no AC load. • Average inverter efficiency: Enter the inverter efficiency in %. Values between 80% and 95% are typical. Zero should be entered if there is no AC load. • Miscellaneous power conditioning losses: Enter power conditioning losses (%), if any. Use manufacturer’s specification for details. Enter zero for none. 30
Energy Model … Ø Battery: • Days of autonomy required: Number of days that the system requires to run when there is no sunshine (for eg. , typical value for a SHS is 3 days). • Nominal battery voltage: Input the voltage of the battery bank (not the voltage of a single battery). 31
Energy Model … • Battery efficiency: The average efficiency (%) of the battery, as specified at the nominal temperature of 25ºC should be mentioned. In the absence of information from the battery supplier, an efficiency of 85% could be used. • Maximum depth of discharge: DOD is suggested by the manufacturer. Usually, for automotive batteries it is 30 -40%, for flat plate deep cycle batteries 50 -60% and for tubular plate batteries 70 -90%. • Charge controller (DC to DC) efficiency: The average efficiency of the charge controller, in %. 32 A default value of 95% is suggested.
Energy Model … • Battery temperature control: • Ambient: If the battery is subject to fluctuations in outdoor temperature. • Constant: If the battery is kept at a constant temperature e. g. at the basement of a house. • Minimum: If the battery follows the fluctuations of outdoor temperature except when it falls below a certain level, e. g. if the battery is located inside a phase-change box or if the battery is heated. 33
Energy Model … • Suggested nominal battery capacity: The model calculates the suggested nominal capacity of the battery bank, in Ah. • Nominal battery capacity: Input the actual nominal capacity of the battery bank, in Ah. By default the model will enter the value calculated under "Suggested nominal battery capacity. " 34
Energy Model … PV array: • PV module type: Select the type of PV module from the six options from the drop-down list. The typical efficiencies are: mono-Si (13%), poly-Si (11%), a-Si (5%), Cd. Te (7%) and CIS (7. 5%). • PV module manufacturer / model: This is done by selecting from the database. The manufacturer, type and model of PV module could be chosen from the list. The model will automatically insert the required parameters where necessary. • Nominal PV module efficiency: If the model of the PV module is mentioned by the user, nominal efficiency (%) of the PV module used should be mentioned here. RETScreen model will automatically insert this information if the model is 35 chosen from the database.
Energy Model … • PV array controller: Select the type of controller from the list. • MPPT or Clamped (a direct connection between the array and the batteries; in this configuration the array operates at the voltage set by the battery. ) • Miscellaneous PV array losses: – The user should enter array losses (%) from miscellaneous sources not taken into account elsewhere in the model (eg. dust). – A recommended value of this loss is 7%. 36
Energy Model … • Genset: Note, if genset is not selected under "PV system configuration", this section will not appear in the sheet. • Charger (AC to DC) efficiency: Enter the efficiency (%) of the battery charger/ rectifier. Values usually range between 80 and 95%. If data from the manufacturer is not available a value of 80% will likely be a reasonable estimate. • Suggested genset capacity: The model calculates and suggests the capacity of the genset, in k. W. The genset is sized so that: –it can always meet the AC load, and –it can nominally recharge the batteries in 8 hours. 37
Energy Model … • Genset capacity: Enter the genset capacity, in rated k. W for continuous operation as appropriate. • Fuel type: Select the type of fuel used by the genset. A list of common fuels is provided in the dropdown list. • Specific fuel consumption: Enter an estimation of the fuel consumption of the genset, per unit k. Wh of electricity delivered. 38
Energy model: System characteristics 39
Energy Model … Output of Energy Model: • Equivalent DC energy demand: The model calculates the equivalent DC energy demand, in MWh. This is the sum of the DC demand the AC demand divided by inverter efficiency, over the season of use. • Energy from genset: The model calculates the energy delivered by the genset (if any) over the season of use, in MWh. • Equivalent DC demand not met: The model calculates the electrical energy that the photovoltaic system is unable to provide to meet both DC and AC loads. The best value is zero. • Specific yield: The model calculates the specific yield, 40 in k. Wh/m²
Energy Model … Output of Energy Model: • Overall PV system efficiency: The model calculates the overall efficiency of the PV system. This value is the amount of renewable energy delivered divided by the amount of solar radiation incident on the photovoltaic array. • Renewable energy delivered: The model calculates the annual renewable energy delivered (MWh), which is the amount of equivalent DC electrical energy actually delivered by the PV system to the load. The user can also change the unit of energy selecting from the drop-down list. 41
Energy Model … Note the colors of the cells and the ranges suggested Output Choose the next work sheet 42
GHG Analysis Model … GHG emission reduction analysis worksheet contains four main sections: • Background Information • provides project reference information as well as GHG global warming potential factors. • Base Case System (Reference) • provides a description of the emission profile of the reference system, representing the baseline for the analysis. • Proposed Case System (Mitigation) • provides a description of the emission profile of the proposed (mitigation) system • GHG Emission Reduction Summary • provides a summary of the estimated GHG emission reduction based on the data entered by the user in the preceding sections and from values entered or calculated in the other RETScreen worksheets (e. g. annual energy delivered). • results are calculated as equivalent tons of CO 2 avoided per 43 annum.
GHG Analysis Model … 1. Use GHG analysis sheet? • The user selects from the drop-down list whether or not the optional GHG Analysis worksheet will be completed. 2. Type of analysis • The user selects one of the two options: "Standard" and "Custom“. • "Standard" analysis uses many pre-defined parameters. • "Custom" analysis requires that parameters be entered by the user. 3. Background Information 3. 1 Project name (for reference purposes only) 3. 2 Project location (for reference purposes only) 3. 3 Global Warming Potential of GHG • The model indicates the global warming potential of methane (CH 4) and nitrous oxide (N 2 O). The default values are those defined by the Revised Intergovernmental Panel on Climate Change (IPCC) Guidelines for Greenhouse Gas Inventories, 1996. • If the user selects the "Custom" type of analysis, different values from the default values provided may be entered by the user. 44
GHG Analysis Model … 4. Base Case Electricity System (Reference) 4. 1 Fuel type • For "On-grid" projects and for applications where the base case power/energy source is "Grid extension, " the user selects the fuel type from the options in the drop-down list. The fuel type is the fuel(s) or power plant(s) which will be displaced by the renewable energy project. • For "Off-grid" and "Water pumping" applications that do not use "Grid extension" as the base case power/energy source, the user selects the fuel type in the Energy Model worksheet and it is copied automatically to the GHG Analysis worksheet. • For "Standard" projects, if the user selects one of the fuel types from the drop-down list, default emission factor and fuel conversion efficiency values will be inserted into the row inputs of the table. • For "Custom" projects, if a specific fuel type is not included in the drop-down list, the user may choose "Other" and manually enter values for the remainder of the row inputs. 45
GHG Analysis Model … 4. 2 Fuel mix • For "On-grid" projects, where the base case power/energy source is "Grid extension, " the user enters the fuel mix (%) of the base case electricity system for each fuel type. • For "Off-grid" and "Water pumping" applications that do not use "Grid extension" as the base case power/energy source, there is a single fuel type displaced and the fuel mix is thus set to 100 %. 4. 3 CO 2, NO 2 and CH 4 emission factor 4. 3. 1 Custom • The user enters the CO 2, CH 4 and N 2 O emission factors for the different fuel types (They represent the mass of greenhouse gas emitted per unit of energy). 46
GHG Analysis Model … 4. 3 CO 2, NO 2 and CH 4 emission factor 4. 3. 1 Custom • For "On-grid" projects and for applications where the base case power/energy source is "Grid extension, " the user should enter factors representative of large generating plants. • The model calculates the equivalent emission factors for the global electricity mix and per unit of electricity delivered. The electricity mix factors thus account for a weighted average of the fuel conversion efficiencies and T & D losses of the different fuel types. • Units are given in kilograms of gas emitted per gigajoule of end-use electricity delivered. • For "Off-grid" and "Water pumping" applications, the user should enter emission factors representative of the power source for the system specified. • For each fuel type selected, units are given in kilograms of gas emitted per gigajoule of heat energy generated (kg/GJ). 47
GHG Analysis Model … 4. 3 CO 2, NO 2 and CH 4 emission factor 4. 3. 2 Standard • The model provides the CO 2, CH 4 and N 2 O emission factors • The default factors provided are those which are representative of large power plants that feed a central electricity grid. • For each fuel type selected and the total electricity mix, units are given in kilograms of gas emitted per gigajoule of heat energy generated (kg/GJ). The default values provided by the model 48
GHG Analysis Model … 4. 4 Fuel conversion efficiency 4. 4. 1 Custom • For "On-grid" projects and for applications where the base case power/energy source is "Grid extension, " the user enters the fuel conversion efficiency for the selected fuel type. • This value is used to calculate, for each fuel type, the aggregate GHG emission factor and therefore is only relevant for fuel types which actually produce greenhouse gases (i. e. with non-zero CO 2, CH 4 and N 2 O emission factors). Fuel types which do not involve a thermal to electric conversion (e. g. hydro) have a default value of 100 %. 4. 4. 2 Standard • The model provides the fuel conversion efficiency for the selected fuel type. The fuel conversion efficiency is the efficiency of energy conversion from primary heat potential to actual useful energy output. 49 • The default values provided by the model are given.
GHG Analysis Model … 4. 5 Transmission and distribution losses • The user enters the transmission and distribution (T & D) losses (%) of the base case electricity system, which includes all energy losses between the power plant and the end-user. • The model calculates the weighted average of the T & D losses of the global electricity mix. • Units are given as a percentage of all electricity losses to electricity generated. It is reasonable to assume T & D losses of 8 to 10% in modern grids in industrialised countries and 10 to 20% in grids located in developing countries. 50
GHG Analysis Model … 4. 6 GHG emission factor • The model calculates the GHG emission factor for each reference fuel type. Values are calculated based on the individual emission factors, the fuel conversion efficiency and the T & D losses, if any. • For "On-grid" projects and for applications where the base case power/energy source is "Grid extension, " the weighted GHG emission factor for the total electricity mix is calculated. • For "Off-grid" applications, the user selects the base case electricity system in the Energy Model worksheet from the following list: Genset, Thermoelectric generator, Grid extension, Non-rechargeable batteries, 51 Lantern and other.
GHG Analysis Model … 4. 6 GHG emission factor • For "Water pumping" applications, the user selects the base case electricity system in the Energy Model worksheet from the following list of available power sources: Genset, Grid extension, Engine driven pump and Other mechanical pump. • The model allows for a more detailed analysis regarding T & D losses and using the "Custom" option under the "Type of analysis" drop-down list, the user can prepare an even more detailed analysis regarding emission factors, etc. • Units are given in tons equivalent of CO 2 emission per megawatt-hour of end-use electricity delivered 52 (t. CO 2 / MWh).
GHG Analysis Model … 5. Proposed Case Electricity System (Mitigation) The proposed case system is normally referred to as the mitigation option. 5. 1 Fuel type/ Fuel mix • The fuel type of the PV project is assumed to be entirely solar, except for "Off-grid" applications for which the PV/batteries/genset configuration has been selected. 5. 2 CO 2, CH 4 and N 2 O emission factor • Units are given in kg of gas emitted per GJ of end-use energy (kg/GJ). Custom: The user enters the CO 2, CH 4 and N 2 O emission factors corresponding to the fuel type. Standard: The model provides default values for the CO 2, CH 4 and N 2 O emission factors corresponding to the fuel type. 53
GHG Analysis Model … 5. 3 Fuel conversion efficiency • For water pumping applications the fuel conversion efficiency equals the PV pump system efficiency specified in the Energy Model worksheet. • For PV/battery/genset configurations, the genset fuel conversion efficiency is calculated from the specific fuel consumption, as entered in the Energy Model worksheet. • The fuel conversion efficiency is used in conjunction with the CO 2, CH 4 and N 2 O emission factors and the transmission and distribution losses, if any, to calculate the aggregate GHG emission factor for the PV project. 54
GHG Analysis Model … 5. 4 Transmission and distribution losses • The user enters the transmission and distribution (T & D) losses (%) of the proposed case PV project, which includes all energy losses between the point at which the power plant is connected to the grid and the end-user. 5. 5 GHG emission factor • GHG emission factor is calculated based on the individual emission factors and the fuel conversion efficiency. • Units are given in tons equivalent of CO 2 emission per megawatt-hour of end-use energy delivered (t. CO 2 / MWh). 55
GHG Analysis Model … 6. GHG Emission Reduction Summary • The model calculates the annual reduction in GHG emissions when the base case system is displaced with the PV system. Units are given in tons equivalent of CO 2 emission per megawatt-hour of end-use energy delivered (t. CO 2 / MWh). 6. 1 Base case GHG emission factor • The model transfers the base case GHG emission factor calculated in the base case electricity system (reference) section. This value represents the amount of GHG emitted per unit of end-use energy delivered for the base case system. 6. 2 Proposed case GHG emission factor • The model transfers the PV project GHG emission factor calculated in the proposed case electricity system (mitigation) section. This value represents the amount of GHG emitted per unit of end-use energy delivered if the PV project is installed. 56
GHG Analysis Model … 6. 3 End-use annual energy delivered • The model calculates the end-use annual energy delivered by the PV project which is the amount of PV energy delivered to the electricity grid for "On-grid" applications, as calculated in the Energy Model worksheet, minus the T & D losses for the grid visà-vis the PV project. For "Off-grid" and "Water pumping" applications it is simply the amount of end-use annual energy delivered to the load. • Units are given in megawatt-hours of end-use energy delivered (MWh). 6. 4 Annual GHG emission reduction • The model calculates the annual reduction in GHG emissions estimated to occur if the proposed PV project is installed. • The calculation is based on emission factors of both the base case and the proposed case system and on the end-use energy delivered by the PV project on an annual basis. • Units are given in equivalent tons of CO 2 emission per year 57 (t. CO 2/yr).
GHG Analysis Worksheet 58
Financial Analysis Model … • Important financial (input) parameters required to evaluate a project. • Costs related to technology, operation and maintenance, etc • Inflation, discount rate, energy cost escalation rate • Debt ratio, debt term, debt interest rate, depreciation • RE production credit, duration, credit escalation rate • Project life • Income tax analysis (optional) • GHG emission reduction credit, duration, credit 59 escalation rate
Financial Analysis Model … Cashflow Calculations Cash Inflows Cash Outflows Equity Investment Annual Debt Payments O&M Payments Periodic Costs $ Annual Cashflows 40 20 thousands of $ Fuel Savings O&M Savings Periodic Savings Incentives Production Credits GHG Credits Cumulative Cashflow Time (yr) 0 0 1 2 3 4 5 6 7 8 9 10 -20 -40 Indicators -60 -80 -100 Year Net Present Value Simple Payback IRR Etc. 60 © Minister of Natural Resources Canada 2001 – 2002.
RETScreen Validation Example: Accuracy of Solar Resource Tilt-up Model within 7% Measured Data Calculated Data 61 Mean daily global radiation in the plane of the PV array
RETScreen Validation • e book lists a number of cases where results of RETScreen has been compared with real examples. • The cases have been given for each technology 62
® RETScreen Limitations • Currently not covered: – Concentrator systems – Radiation data estimation uses correlations – Only specific configurations are available – Simplified assumptions • Only Energy model calculations are detailed • Each technology is evaluated independently 63
Things to know… Contains information on • Models • Product database • Weather database • Online Manual 64
Things to know… • Details of models • Case studies • Download 65
Things to know… • Online manual downloaded automatically • An icon is available 66
Conclusions • RETScreen is an annual analysis with ® monthly resource calculation that can achieve accuracy comparable to hourly simulation models • RETScreen® automatically calculates important indicators of financial viability • RETScreen can provide significant ® preliminary feasibility study cost savings • A useful tool to understand the project case development 67
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