After the monthly National Lab TAP Webinar, which is hosted by the U.S. Department of Energy Technical Assistance Program (TAP) for state and local officials, presenters answer several of the questions that were asked during the webinar. We invite you to enter any comments about the topic of the presentation, and to share your thoughts with others in the comments section following these questions/answers. You can also find copies of the October 27 webinar in PDF format, audio files in MP3 format, and background materials and reports in the TAP Webinar archive.

Babacar asks:
For a Power type project that has a combined technology (wind & PV) with different options (Option 1: wind: 40% power & PV: 60% power) and (Option 2: wind: 60% & PV: 40%), for a specific location, could RETScreen select the best option based on the power output?
Rickerson, Leng, and Sheriff answer:
You can evaluate projects using combined technologies in RETScreen by selecting “Power - Multiple Technologies” as the Project Type in the Start worksheet. Then, in the Energy Model, you can define your two different power systems. Once you have defined your two systems, you can also select which system is the base load power system without re-entering the information. RETScreen won't select the best option for you, but it gives you the tools so you can evaluate which option is the best.

Ted asks:
How often is data updated, and are construction and O&M costs adjusted for local conditions?
Rickerson, Leng, and Sheriff answer:

  • The RETScreen Product Database is updated each time we update the software. We add products upon request from manufacturers.
  • The RETScreen Climate Database is updated on a regular basis to add more ground monitoring stations, and to include more recent data.
  • The RETScreen Cost Database is updated each time we have a major update of the software or upon request, if adjustment is critical. The cost data given in the user manual is for Canada, and was updated in 2006. You can select your own currency in the Start worksheet. You need to tick the “Show Settings” box to see this option. Then you can enter your own data in the yellow cells in the software.

Peter Hoberg asks:
Is the weather (climate) data processed to be for a “TYPICAL” year (TMY) or is it based on the historical record? Also, are minimum and maximum temperature values available? Can I download the data for use in other applications?
Rickerson, Leng, and Sheriff answer:

  • The RETScreen Climate Database is based on historical records. The database includes climate data from ground monitoring stations and from NASA's global satellite/analysis data. If climate data is not available from a specific ground monitoring station, data is then provided from NASA's satellite/analysis data. Ground-based meteorological data includes averages of ground-based observations for more than 6,500 sites around the world, compiled from more than 50 different sources from 1982-2006. The current NASA data set is formulated from data gathered for a 20-year period starting in July 1983, using a 1-degree cell.
  • The minimum and maximum values are not available in the RETScreen Climate Database.
  • You can't download the data. If you tick the “Show Data” box in the Start worksheet, you can view the data for each climate’s location by pasting the data from the database to the software.

Peter Stone asks:
What about efficiency studies? Can we specify changing from one pump to another? Boiler upgrades for water heating and integrating SHW for base load, etc...
Rickerson, Leng, and Sheriff answer:

  • To compare the performance of two different pumps in RETScreen, you need to select “Energy Efficiency Measures Project Type” in the Start worksheet, and then you can open the “Pumps” form in the Energy Model worksheet. In this form, you can enter the characteristics of your base-case pump and of your new proposed-case pump. These include the pump efficiency, the flow rate (e.g. variable vs. constant), the type of flow control (throttling vs. variable speed), and the number of hours that the pump is operating. Other characteristics include the motor efficiency at full load, which depends on the type of motor (e.g., standard efficiency, energy efficient, or premium efficiency), the motor capacity, and the load factor (e.g.,  the ratio of the average load during operating hours over the full load capacity, including the capacity of the motor).
  • To evaluate the integration of a solar water heating system, you need to select “Heating” as the Project Type and “Solar Water Heater” as the Technology in the Start worksheet. Then, in the Energy Model worksheet, you can define your load, your solar water heating system (proposed case-base load system), your base-case system (e.g., a boiler), and your proposed case peak load system. If you want to use a solar water heating system as part of an energy efficiency measures project, you need to do two separate RETScreen analyses. First, do the solar water heating analysis, then start a second one after selecting “Energy Efficiency Measures Project Type,” and then enter the SWH heating delivered as a negative load in the the Other form. In version 5, we are looking at integrating the different renewable energy technologies to Energy Efficiency Measures projects.

Answers submitted by: Wilson Rickerson, MCG; Greg Leng, and Farrah Sheriff of RETScreen International