RETScreen - Energy efficiency - Speaker's notes
SLIDE 1: Energy Efficiency Project Analysis with RETScreen 4
This presentation introduces the all-new Energy Efficiency Project Analysis capabilities of RETScreen 4.
SLIDE 2: Facility Types
RETScreen 4 can investigate the viability of energy efficiency improvements in a wide range of residential, commercial, institutional, and industrial buildings, from single-family homes to office buildings to hospitals. It deals with pumps, fans, motors, steam losses, compressed air, heat recovery, refrigeration, and more. It is useful for both new construction and retrofits. Whole facilities can be modelled, or sub-systems and rooms can be studied individually. In this way, even large, complex industrial facilities can be examined.
SLIDE 3: Energy Efficiency Analysis
At the outset of an energy efficiency project, certain information about energy usage must be collected. First, determine the types of fuels that are used and the amounts consumed; here, electricity is also considered a fuel. Second, identify and characterize the equipment that converts fuel into something more useful. For example, a heater might be 60% efficient in generating hot water using oil. Third, determine where and how that useful end product is being used. For hot water, showers could be the principal consumer.
Having understood the use of energy in the project, attempt to make improvements. First, minimize the usage of the end product. For the hot water example, find ways to reduce consumption, perhaps by installing low flow showerheads. Second, maximize the efficiency of the devices consuming the fuel. The oil heater might be replaced with a more efficient model or tuned using a combustion analyser. Third, optimize the supply of fuel. For example, natural gas could be used in place of oil, or a solar hot water system could reduce oil or gas consumption.
This prioritization, from minimizing usage through maximizing efficiency to optimizing supply, is critical. Efforts to minimize usage usually generate better returns overall than efforts to maximize efficiency, which in turn are more cost-effective than optimizing supply. Furthermore, the sizing of equipment typically depends on throughput, so minimizing usage has an upstream impact. In the hot water example, reducing the water requirement might permit a smaller gas heater and solar collector. It might also make them less financially attractive, but overall project returns would be better.
SLIDE 4: The RETScreen Energy Efficiency Model
As for all technologies, RETScreen's Energy Efficiency Model compares a proposed clean energy project to a base case scenario, usually involving conventional technology. For instance, the viability of triple glazing units and an air source heat pump would be examined through comparison to the conventional construction, which might be double-glazing units and a furnace.
The RETScreen analysis involves five steps. First, identify the types of fuels used in the building and the associated fuel rates, or per unit costs for the fuels. Also, determine the operating schedules, as discussed in the next slide.
Second, specify the facility characteristics. For example, here the user would indicate the type of windows and heating system in both the base case and the proposed case. The user would also enter the incremental cost for each proposed case measure.
Third, ensure the validity of the inputs by examining RETScreen's summary of energy and fuel usage. If possible, verify RETScreen's estimates against past energy bills.
Fourth, determine the emissions reductions of the project. This step is optional.
Fifth, enter financial parameters so that RETScreen can provide a summary of the financial viability of the project.
Let's look at these steps in more detail.
SLIDE 5: Fuels and Schedules
RETScreen permits an analysis involving up to 6 different fuels. By default, one of them is electricity. A drop-down list of common fuels includes natural gas, oil, propane, kerosene, coal, biomass and more. Other, user-defined fuels are possible, too. RETScreen accommodates a variety of units. For example, natural gas usage can be specified in GJ, cubic metres, 100's of cubic feet, or millions of BTUs.
Operating schedules are used in the calculation of weather-dependent heating and cooling loads, that is, loads due to the building envelope and ventilation. RETScreen automatically includes a "24/7" schedule. The user can add up to 5 schedules to specify the hours the building is occupied for each day of the week. The user indicates the desired space heating and cooling temperatures during occupied periods and, through a temperature setback or setup, unoccupied periods.
SLIDE 6: Facility Characteristics
RETScreen deals with efficiency measures applied to the heating system, cooling system (including GHG impacts of refrigerant leaks), building envelope (including air infiltration), ventilation, lights, electrical equipment, hot water, pumps, fans, motors and more. For each of these, a hyperlink opens a form.
This slide shows the pump characteristics form. Here the user describes the base case and the proposed case system. For each characteristic, the user specifies up to five base case/proposed case combinations. For example, a building with many different pumps could have some of them upgraded to energy efficient motors, others upgraded to premium efficiency motors, and others yet changed to variable flow.
RETScreen helps the user fill the form. For example, when the user enters the capacity and the type of the motor on the pump form, RETScreen automatically provides an estimate of the efficiency. This estimate can be overwritten, but often a better estimate will not be available.
For the pump itself, the user specifies the efficiency, whether the flow is variable or constant, a few parameters describing how variable flow is achieved, the operating hours of the pump, and the number of pumps having these characteristics. The form shows the energy savings associated with the modification.
Obviously, based on only a handful of inputs, RETScreen does not model the device in all its complexity. But RETScreen does provide a good first estimate, revealing whether it is worthwhile to investigate with more hard-to-obtain input parameters.
The user also enters the incremental initial costs and incremental annual operation and maintenance savings. These would include, for instance, the reduced costs for valve replacement if variable pump flow were achieved with a variable speed drive instead of a throttling valve.
Inefficiencies in pumps, lights and other devices generate heat. The user selects whether RETScreen considers this heat in its calculation of building heating and cooling loads.
SLIDE 7: Facility Characteristics
Other facility characteristics that can be specified through further RETScreen forms include process electricity, process heat, process steam (for which RETScreen automatically calculates steam properties), steam losses based on the size of either a leak or a plume, heat recovery, compressed air, and refrigeration.
The heat recovery form, shown on this slide, is unusual in that the base case is not explicitly described; rather, the base case is no heat recovery. A heat recovery efficiency is applied directly to a source of waste heat (for example, a compressor or condenser) or to the heat transfer between two fluid streams. The fluids may be steam, water, or user-defined. This is useful in the food and chemicals industries, where fluids other than water and steam are common.
RETScreen also contains an "Other" form. This helps model large, complex facilities.
SLIDE 8: Summary Section
The Summary Section consists of a summary of the fuel used, a project verification sub-section, and a benchmark sub-section.
For each fuel, the summary shows the consumption and cost in the base case and the proposed case, and the fuel cost savings corresponding to the difference between the two. The fuel and energy consumption are also broken down by heating system, cooling system, and electricity consumed elsewhere in the building.
The project verification sub-section compares RETScreen's estimate against past fuel consumption. For a retrofit, RETScreen's base case estimate can be verified against consumption figures from past fuel bills; if the two differ greatly, the analysis should be checked. Similarly, a year or more after project completion, fuel bills can be compared to the proposed case estimate, to verify that the expected savings are being achieved.
There are many benchmarks for the energy performance of different types of facilities. Building codes may establish minimum benchmarks, and incentives or certification may be based on a building exceeding a certain benchmark. Often these are expressed in normalized units, such as kWh per m² of floor space, MJ per person, or even quite specialized units.
In RETScreen's benchmark subsection, the user specifies units for a benchmark and indicates how RETScreen's fuel estimates should be normalized. For example, for a benchmark in kWh per m² of floor space, the user would enter the floor space in square metres. Then RETScreen presents the base case and proposed case fuel consumption or energy in terms of the benchmark units, broken down by heating, cooling and electricity.
SLIDE 9: Emissions Analysis and Financial Analysis
RETScreen's Energy Efficiency Project Model employs the same Emissions analysis and Financial analysis as other technologies. For simplified analyses in a single spreadsheet, Method 1 is selected from the Start page. For more in-depth analyses with individual Emissions Analysis and Financial Summary Sheets, Method 2 is selected.
SLIDE 10: The RETScreen Project Database
RETScreen's project database contains templates, case studies, and user-defined project databases, selected by three tabs across the top of the window.
Templates are RETScreen spreadsheets pre-filled with reasonable values for common types of projects. The help manual contains a text description of each template. Templates provide a quick and easy starting point for typical projects.
Case studies are similar to templates, but are analyses of built projects. Developed as aides for learning about both RETScreen and clean energy technologies, case studies are presented as assignments in the help manual. The solution is the filled-in RETScreen worksheet available from the project database. A Real Project description is found in the help manual. RETScreen contains over 100 case studies, covering the gamut of clean energy technologies.
Analyses prepared by the user can be saved to user-defined project databases, stored as compact ".RET" files. A single database can contain all the scenarios or different analyses associated with a project.
The "New" button located at the far right hand-side of the project database window opens a blank RETScreen analysis. The Start page will be reset to default values; other pages will have blanks for all inputs.
We can save our analysis as either a complete Excel workbook or a more compact .ret file. To do the latter, we choose the "Save as type RETScreen *.ret" option, and then either enter a filename for a new file or select a .RET file to add the project to an existing file. Here we will create a new file. We can then reload it through the project database.
The project database also provides access to a large selection of sample projects. For example, we open a landfill gas power project from Norway. This utilizes the landfill gas calculator, one of RETScreen's many tools.
We can save this project to the .RET file we just created. Each file can thus contain many projects. For example, a single file can contain different scenarios, the same analysis repeated with different equipment types, or different analyses for the same client. In short, users can collect and organize their RETScreen projects any way they want.
SLIDE 11: Project Example: Hot Water
Let's see how RETScreen can be applied to energy efficiency measures for hot water in a 40-unit apartment building in Toronto. Imagine that after inspecting the building, we estimate that low-flow showerheads could reduce flow by 35% and that the supply temperature could be reduced from 60 to 55 deg C. We are considering switching from an old oil-fired heater to a natural gas heater, costing $40,000, and adding 20% efficient waste-heat recovery to the effluent stream. The low-flow showerheads and heat recovery unit cost $15,000. We also note that the reduced flow would result in reduced water use, which based on past water bills should be worth $3,000 per year.
For convenience, this example corresponds to a pre-existing template in the RETScreen project database. We open this template.
The first four cells on the start page are grey-that is, they do not affect the calculations. The information entered here is for the user's benefit.
"Energy efficiency measures" has been selected as the project type. The choice of facility type-residential, commercial, institutional, industrial, or other-determines which facility characteristics appear in the energy model page. We'll do a simplified, single sheet analysis, and thus choose Method 1; Method 2 would permit more detail.
The heating value reference selects between two conventions used for quantifying the energy available from combustion of a given fuel: in Canada and the USA, the convention is to use the higher heating value, which includes the energy available from condensing the steam by-product of combustion. Elsewhere the lower heating value, which excludes this energy, is used.
The default climate data is for Ottawa. We open the climate database and change the location to Toronto.
In the energy model page we start by describing the fuel types. We are considering two fuels-oil and natural gas, which are already fuel type 2 and fuel type 3. The fuel rate is the price paid for fuel, for example, $0.40 per cubic metre of natural gas.
Since schedules are used for building envelope and ventilation calculations, and do not affect hot water, we ignore them.
Having defined our fuel types and schedules, we can deselect "Show Data" for this sub-section of the energy page.
We want to make some changes in our heating system, so we click on that hyperlink in the list of facility characteristics. The form already contains data corresponding to our example: the base case uses diesel oil, entered as fuel type 2, and the proposed case uses natural gas, fuel type 3. We assume that the seasonal efficiency of the old oil boiler and new heater are around 65 and 80%, respectively. The incremental cost of the natural gas heater is $40,000. We assume that due to reduced maintenance requirements the annual O&M costs of this new heater, excluding fuel savings, will be $1000 less than for the old boiler. We click on the green paste button and the form closes.
We also want to make changes to the hot water system, so we open this form. First we must estimate the hot water usage. If we knew this from past bills, we could enter it directly. RETScreen includes a helpful calculator for those cases where it is unknown. By selecting "Apartment" as the load type and indicating 40 units that are 100% occupied, we obtain an estimate of 6,778 litres of hot water per day. We are not obliged to use this estimate; here we assume, based on our visit, that base case hot water use is 10,000 litres per day. With 35% reduction in flow, this would be 6,500 litres per day.
We are proposing to reduce the water temperature to 55 deg C from 60 deg C. The energy required to heat the water to this temperature will depend on how cold the water supply is. If we knew minimum and maximum supply temperatures, we could enter them directly. Otherwise, RETScreen provides a first estimate based on climate data.
In the base case, there is no heat recovery; in the proposed case, 20% of the available heat is recovered. The incremental initial costs of $15,000 and incremental annual O&M savings of $3,000, resulting from lower water bills, are entered. We specify that the water is heated with heating system 1. RETScreen calculates that water heating requires 222 MWh of energy in the base case, and 105 MWh in the proposed case-a 53% reduction.
Note that this is not fuel savings, which depend on the heating system efficiency. This shows up when we close the form. We can choose the units for these results: let's say we prefer MWh. Then we see that flow reduction, temperature reduction, and heat recovery would annually save fuel of 149 MWh; switching our heater from oil to natural gas saves 65 MWh per year. We may also examine fuel consumption, energy, or energy saved.
The value of this in terms of cost savings is shown on the right; we can select which measures we wish to include by checking the boxes in the right-hand column. The simple payback period is shown as a very quick indication of whether the measure is attractive.
The flow reduction, temperature and heat recovery measures save nearly $15,000 annually, and have a simple payback period of 0.9 years. With all efficiency measures implemented, changing the heating system has a payback period of 5.4 years, and the ensemble of measures has a payback period of 2.2 years.
Note that were only the heating system changed, the payback period would be 2.5 years. This is misleading: we would be better off keeping the old heating system but implementing the other efficiency measures. This demonstrates the importance of minimizing usage before maximizing efficiency.
In the summary section, RETScreen shows, for each fuel type, base case and proposed case fuel consumption and costs, and fuel cost savings. In the project verification tool, we can compare actual fuel consumption to RETScreen's estimates. Let's say past bills showed average annual diesel fuel consumption to be 35,000 L. RETScreen's estimate is 8% below this, suggesting that our analysis of the base case is reasonable.
Imagine we wanted to benchmark our results on a MWh per person basis. Assuming 3 people in each of the 40 apartments, in the benchmark section, we select MWh as the energy unit, "person" as the reference unit, and enter 120 people. RETScreen tells us that we save almost 1 MWh per person per year. If we wanted to express this in terms of MWh per apartment, we could select "user-defined" reference units, enter "apartment" and indicate 40 apartments.
The emissions analysis and financial analysis are the same as for other technologies. Remember when doing these sections that Excel formulae can be used..
Having made these changes to the template, we save our work to a new file.
SLIDE 12: Questions?
This completes the overview of Energy Efficiency Project Analysis with RETScreen 4.
This presentation introduces the all-new Energy Efficiency Project Analysis capabilities of RETScreen 4.
SLIDE 2: Facility Types
RETScreen 4 can investigate the viability of energy efficiency improvements in a wide range of residential, commercial, institutional, and industrial buildings, from single-family homes to office buildings to hospitals. It deals with pumps, fans, motors, steam losses, compressed air, heat recovery, refrigeration, and more. It is useful for both new construction and retrofits. Whole facilities can be modelled, or sub-systems and rooms can be studied individually. In this way, even large, complex industrial facilities can be examined.
SLIDE 3: Energy Efficiency Analysis
At the outset of an energy efficiency project, certain information about energy usage must be collected. First, determine the types of fuels that are used and the amounts consumed; here, electricity is also considered a fuel. Second, identify and characterize the equipment that converts fuel into something more useful. For example, a heater might be 60% efficient in generating hot water using oil. Third, determine where and how that useful end product is being used. For hot water, showers could be the principal consumer.
Having understood the use of energy in the project, attempt to make improvements. First, minimize the usage of the end product. For the hot water example, find ways to reduce consumption, perhaps by installing low flow showerheads. Second, maximize the efficiency of the devices consuming the fuel. The oil heater might be replaced with a more efficient model or tuned using a combustion analyser. Third, optimize the supply of fuel. For example, natural gas could be used in place of oil, or a solar hot water system could reduce oil or gas consumption.
This prioritization, from minimizing usage through maximizing efficiency to optimizing supply, is critical. Efforts to minimize usage usually generate better returns overall than efforts to maximize efficiency, which in turn are more cost-effective than optimizing supply. Furthermore, the sizing of equipment typically depends on throughput, so minimizing usage has an upstream impact. In the hot water example, reducing the water requirement might permit a smaller gas heater and solar collector. It might also make them less financially attractive, but overall project returns would be better.
SLIDE 4: The RETScreen Energy Efficiency Model
As for all technologies, RETScreen's Energy Efficiency Model compares a proposed clean energy project to a base case scenario, usually involving conventional technology. For instance, the viability of triple glazing units and an air source heat pump would be examined through comparison to the conventional construction, which might be double-glazing units and a furnace.
The RETScreen analysis involves five steps. First, identify the types of fuels used in the building and the associated fuel rates, or per unit costs for the fuels. Also, determine the operating schedules, as discussed in the next slide.
Second, specify the facility characteristics. For example, here the user would indicate the type of windows and heating system in both the base case and the proposed case. The user would also enter the incremental cost for each proposed case measure.
Third, ensure the validity of the inputs by examining RETScreen's summary of energy and fuel usage. If possible, verify RETScreen's estimates against past energy bills.
Fourth, determine the emissions reductions of the project. This step is optional.
Fifth, enter financial parameters so that RETScreen can provide a summary of the financial viability of the project.
Let's look at these steps in more detail.
SLIDE 5: Fuels and Schedules
RETScreen permits an analysis involving up to 6 different fuels. By default, one of them is electricity. A drop-down list of common fuels includes natural gas, oil, propane, kerosene, coal, biomass and more. Other, user-defined fuels are possible, too. RETScreen accommodates a variety of units. For example, natural gas usage can be specified in GJ, cubic metres, 100's of cubic feet, or millions of BTUs.
Operating schedules are used in the calculation of weather-dependent heating and cooling loads, that is, loads due to the building envelope and ventilation. RETScreen automatically includes a "24/7" schedule. The user can add up to 5 schedules to specify the hours the building is occupied for each day of the week. The user indicates the desired space heating and cooling temperatures during occupied periods and, through a temperature setback or setup, unoccupied periods.
SLIDE 6: Facility Characteristics
RETScreen deals with efficiency measures applied to the heating system, cooling system (including GHG impacts of refrigerant leaks), building envelope (including air infiltration), ventilation, lights, electrical equipment, hot water, pumps, fans, motors and more. For each of these, a hyperlink opens a form.
This slide shows the pump characteristics form. Here the user describes the base case and the proposed case system. For each characteristic, the user specifies up to five base case/proposed case combinations. For example, a building with many different pumps could have some of them upgraded to energy efficient motors, others upgraded to premium efficiency motors, and others yet changed to variable flow.
RETScreen helps the user fill the form. For example, when the user enters the capacity and the type of the motor on the pump form, RETScreen automatically provides an estimate of the efficiency. This estimate can be overwritten, but often a better estimate will not be available.
For the pump itself, the user specifies the efficiency, whether the flow is variable or constant, a few parameters describing how variable flow is achieved, the operating hours of the pump, and the number of pumps having these characteristics. The form shows the energy savings associated with the modification.
Obviously, based on only a handful of inputs, RETScreen does not model the device in all its complexity. But RETScreen does provide a good first estimate, revealing whether it is worthwhile to investigate with more hard-to-obtain input parameters.
The user also enters the incremental initial costs and incremental annual operation and maintenance savings. These would include, for instance, the reduced costs for valve replacement if variable pump flow were achieved with a variable speed drive instead of a throttling valve.
Inefficiencies in pumps, lights and other devices generate heat. The user selects whether RETScreen considers this heat in its calculation of building heating and cooling loads.
SLIDE 7: Facility Characteristics
Other facility characteristics that can be specified through further RETScreen forms include process electricity, process heat, process steam (for which RETScreen automatically calculates steam properties), steam losses based on the size of either a leak or a plume, heat recovery, compressed air, and refrigeration.
The heat recovery form, shown on this slide, is unusual in that the base case is not explicitly described; rather, the base case is no heat recovery. A heat recovery efficiency is applied directly to a source of waste heat (for example, a compressor or condenser) or to the heat transfer between two fluid streams. The fluids may be steam, water, or user-defined. This is useful in the food and chemicals industries, where fluids other than water and steam are common.
RETScreen also contains an "Other" form. This helps model large, complex facilities.
SLIDE 8: Summary Section
The Summary Section consists of a summary of the fuel used, a project verification sub-section, and a benchmark sub-section.
For each fuel, the summary shows the consumption and cost in the base case and the proposed case, and the fuel cost savings corresponding to the difference between the two. The fuel and energy consumption are also broken down by heating system, cooling system, and electricity consumed elsewhere in the building.
The project verification sub-section compares RETScreen's estimate against past fuel consumption. For a retrofit, RETScreen's base case estimate can be verified against consumption figures from past fuel bills; if the two differ greatly, the analysis should be checked. Similarly, a year or more after project completion, fuel bills can be compared to the proposed case estimate, to verify that the expected savings are being achieved.
There are many benchmarks for the energy performance of different types of facilities. Building codes may establish minimum benchmarks, and incentives or certification may be based on a building exceeding a certain benchmark. Often these are expressed in normalized units, such as kWh per m² of floor space, MJ per person, or even quite specialized units.
In RETScreen's benchmark subsection, the user specifies units for a benchmark and indicates how RETScreen's fuel estimates should be normalized. For example, for a benchmark in kWh per m² of floor space, the user would enter the floor space in square metres. Then RETScreen presents the base case and proposed case fuel consumption or energy in terms of the benchmark units, broken down by heating, cooling and electricity.
SLIDE 9: Emissions Analysis and Financial Analysis
RETScreen's Energy Efficiency Project Model employs the same Emissions analysis and Financial analysis as other technologies. For simplified analyses in a single spreadsheet, Method 1 is selected from the Start page. For more in-depth analyses with individual Emissions Analysis and Financial Summary Sheets, Method 2 is selected.
SLIDE 10: The RETScreen Project Database
RETScreen's project database contains templates, case studies, and user-defined project databases, selected by three tabs across the top of the window.
Templates are RETScreen spreadsheets pre-filled with reasonable values for common types of projects. The help manual contains a text description of each template. Templates provide a quick and easy starting point for typical projects.
Case studies are similar to templates, but are analyses of built projects. Developed as aides for learning about both RETScreen and clean energy technologies, case studies are presented as assignments in the help manual. The solution is the filled-in RETScreen worksheet available from the project database. A Real Project description is found in the help manual. RETScreen contains over 100 case studies, covering the gamut of clean energy technologies.
Analyses prepared by the user can be saved to user-defined project databases, stored as compact ".RET" files. A single database can contain all the scenarios or different analyses associated with a project.
The "New" button located at the far right hand-side of the project database window opens a blank RETScreen analysis. The Start page will be reset to default values; other pages will have blanks for all inputs.
We can save our analysis as either a complete Excel workbook or a more compact .ret file. To do the latter, we choose the "Save as type RETScreen *.ret" option, and then either enter a filename for a new file or select a .RET file to add the project to an existing file. Here we will create a new file. We can then reload it through the project database.
The project database also provides access to a large selection of sample projects. For example, we open a landfill gas power project from Norway. This utilizes the landfill gas calculator, one of RETScreen's many tools.
We can save this project to the .RET file we just created. Each file can thus contain many projects. For example, a single file can contain different scenarios, the same analysis repeated with different equipment types, or different analyses for the same client. In short, users can collect and organize their RETScreen projects any way they want.
SLIDE 11: Project Example: Hot Water
Let's see how RETScreen can be applied to energy efficiency measures for hot water in a 40-unit apartment building in Toronto. Imagine that after inspecting the building, we estimate that low-flow showerheads could reduce flow by 35% and that the supply temperature could be reduced from 60 to 55 deg C. We are considering switching from an old oil-fired heater to a natural gas heater, costing $40,000, and adding 20% efficient waste-heat recovery to the effluent stream. The low-flow showerheads and heat recovery unit cost $15,000. We also note that the reduced flow would result in reduced water use, which based on past water bills should be worth $3,000 per year.
For convenience, this example corresponds to a pre-existing template in the RETScreen project database. We open this template.
The first four cells on the start page are grey-that is, they do not affect the calculations. The information entered here is for the user's benefit.
"Energy efficiency measures" has been selected as the project type. The choice of facility type-residential, commercial, institutional, industrial, or other-determines which facility characteristics appear in the energy model page. We'll do a simplified, single sheet analysis, and thus choose Method 1; Method 2 would permit more detail.
The heating value reference selects between two conventions used for quantifying the energy available from combustion of a given fuel: in Canada and the USA, the convention is to use the higher heating value, which includes the energy available from condensing the steam by-product of combustion. Elsewhere the lower heating value, which excludes this energy, is used.
The default climate data is for Ottawa. We open the climate database and change the location to Toronto.
In the energy model page we start by describing the fuel types. We are considering two fuels-oil and natural gas, which are already fuel type 2 and fuel type 3. The fuel rate is the price paid for fuel, for example, $0.40 per cubic metre of natural gas.
Since schedules are used for building envelope and ventilation calculations, and do not affect hot water, we ignore them.
Having defined our fuel types and schedules, we can deselect "Show Data" for this sub-section of the energy page.
We want to make some changes in our heating system, so we click on that hyperlink in the list of facility characteristics. The form already contains data corresponding to our example: the base case uses diesel oil, entered as fuel type 2, and the proposed case uses natural gas, fuel type 3. We assume that the seasonal efficiency of the old oil boiler and new heater are around 65 and 80%, respectively. The incremental cost of the natural gas heater is $40,000. We assume that due to reduced maintenance requirements the annual O&M costs of this new heater, excluding fuel savings, will be $1000 less than for the old boiler. We click on the green paste button and the form closes.
We also want to make changes to the hot water system, so we open this form. First we must estimate the hot water usage. If we knew this from past bills, we could enter it directly. RETScreen includes a helpful calculator for those cases where it is unknown. By selecting "Apartment" as the load type and indicating 40 units that are 100% occupied, we obtain an estimate of 6,778 litres of hot water per day. We are not obliged to use this estimate; here we assume, based on our visit, that base case hot water use is 10,000 litres per day. With 35% reduction in flow, this would be 6,500 litres per day.
We are proposing to reduce the water temperature to 55 deg C from 60 deg C. The energy required to heat the water to this temperature will depend on how cold the water supply is. If we knew minimum and maximum supply temperatures, we could enter them directly. Otherwise, RETScreen provides a first estimate based on climate data.
In the base case, there is no heat recovery; in the proposed case, 20% of the available heat is recovered. The incremental initial costs of $15,000 and incremental annual O&M savings of $3,000, resulting from lower water bills, are entered. We specify that the water is heated with heating system 1. RETScreen calculates that water heating requires 222 MWh of energy in the base case, and 105 MWh in the proposed case-a 53% reduction.
Note that this is not fuel savings, which depend on the heating system efficiency. This shows up when we close the form. We can choose the units for these results: let's say we prefer MWh. Then we see that flow reduction, temperature reduction, and heat recovery would annually save fuel of 149 MWh; switching our heater from oil to natural gas saves 65 MWh per year. We may also examine fuel consumption, energy, or energy saved.
The value of this in terms of cost savings is shown on the right; we can select which measures we wish to include by checking the boxes in the right-hand column. The simple payback period is shown as a very quick indication of whether the measure is attractive.
The flow reduction, temperature and heat recovery measures save nearly $15,000 annually, and have a simple payback period of 0.9 years. With all efficiency measures implemented, changing the heating system has a payback period of 5.4 years, and the ensemble of measures has a payback period of 2.2 years.
Note that were only the heating system changed, the payback period would be 2.5 years. This is misleading: we would be better off keeping the old heating system but implementing the other efficiency measures. This demonstrates the importance of minimizing usage before maximizing efficiency.
In the summary section, RETScreen shows, for each fuel type, base case and proposed case fuel consumption and costs, and fuel cost savings. In the project verification tool, we can compare actual fuel consumption to RETScreen's estimates. Let's say past bills showed average annual diesel fuel consumption to be 35,000 L. RETScreen's estimate is 8% below this, suggesting that our analysis of the base case is reasonable.
Imagine we wanted to benchmark our results on a MWh per person basis. Assuming 3 people in each of the 40 apartments, in the benchmark section, we select MWh as the energy unit, "person" as the reference unit, and enter 120 people. RETScreen tells us that we save almost 1 MWh per person per year. If we wanted to express this in terms of MWh per apartment, we could select "user-defined" reference units, enter "apartment" and indicate 40 apartments.
The emissions analysis and financial analysis are the same as for other technologies. Remember when doing these sections that Excel formulae can be used..
Having made these changes to the template, we save our work to a new file.
SLIDE 12: Questions?
This completes the overview of Energy Efficiency Project Analysis with RETScreen 4.
