National Renewable Energy Laboratory

Dynamic Maps, GIS Data, and Analysis Tools

Federal Energy Management Program (FEMP) Maps

The Federal Energy Management Program (FEMP) teams with Resource Assessment staff at the National Renewable Energy Laboratory (NREL) to create federal energy management program maps showing the market potential for various solar technologies at federal facilities throughout the country.

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Maps of Solar Market Potential at Federal Sites—Dynamic Maps

Solar Resources for the U.S. Department of Defense (Interactive Maps) display the availability of solar resources at military sites across the United States. There are 18 views (or "layers") based on solar economic analyses that can help the user make informed decisions on various technologies, and a unique tool, PVWatts V2, that allows users to calculate the energy production and cost savings for grid-connected photovoltaic (PV) systems located throughout the United States. Note: Pop ups must be enabled to view maps.

The 18 economic analysis layers display viability of three different solar technologies: photovoltaic (PV), solar hot water (SHW), and solar ventilation/air preheat (SVP) systems. PV and SHW applications are based on annual average solar resource estimates using a tilt = latitude collector; SVP applications are based on a modeled dataset of energy delivered to the units. When needed, a commercial electricity rate derived from 2004 POWERmap and POWERdat derived data (© 2006 Platts, a division of the McGraw-Hill Companies) was used. A detailed explanation on how the economic analysis layers were created, including assumptions and formulae used, is available in the section below as well as links to static maps.

About the Maps

Through the use of Geographic Information Systems (GIS), we examined the viability of three solar technologies in the United States. The following are a series of links to jpeg images based on previous work, not the current work depicted in the interactive maps.

(Maps on other renewable energy technologies will be added as they become available.)

These maps show where the technologies are cost-effective today and where they will be cost-effective as the utility rates for electricity change. For example, the maps for solar water heating show areas where cost-effective solar systems could be installed now — the areas with a calculated savings-to-investment ratio of 1 or higher. At commercial electric rates of $0.10/kWh or more, however, solar water heating systems would be cost-effective for nearly any Federal facility in the United States.

Photovoltaic Maps

The following maps depict six scenarios for photovoltaic systems:

For details on the calculations used for the analyses of photovoltaic systems, see the About the Analysis section.

Solar Water Heating Maps

The following maps depict six scenarios for solar water heating systems:

For details on the calculations used for the analyses of solar water heating systems, see the About the Analysis section.

Solar Ventilation-Air Preheating Maps

The following maps depict six scenarios for solar ventilation - air-preheating (solar wall) systems:

For details on the calculations used for the analyses of solar ventilation-air preheating systems, see the About the Analysis section.

About the Analysis

We used ArcInfo® and ArcView® GIS software to conduct the analyses. The base data used in this analysis were annual average solar radiation, using a tilt = latitude collector; and energy cost, using 2004 commercial electricity rates calculated from PowerDat, a database produced by Platts. Six analyses were produced for each technology:

  1. Current savings to investment ratio (SIR);
  2. Current payback period
  3. Electricity rate needed to produce a SIR = 1
  4. Electricity rate needed to produce a payback period of 10 years
  5. The system cost needed to produce a SIR = 1
  6. The system cost needed to produce a payback period of 10 years.

We estimated cost-effectiveness "per square foot of solar collector" or "per watt of PV capacity" rather than using a facility's building energy load. This assumes that the solar system's output will never exceed the load; or if it does, that solar electricity will be sold back to the utility at its purchase price.

Photovoltaics (PV)

We calculated and mapped system costs and efficiencies using the following assumptions and equations.

I: Annual average solar radiation on tilt = latitude collector
  where kWh/m2/day = hrs/day, for hours when array is providing peak output,
  e.g. 5.3 kWh/m2/day = 5.3 hrs/day
CS: PV system cost = $10,000/kW
CE: Energy cost = $/kWh
PW: Present worth = 17.41 yrs
  1. Current SIR given current conditions SIR = (I × 365 days/yr × CE × PW) ÷ CS
  2. Current payback period given current conditions Payback = CS ÷ (I × 365 days/yr × CE)
  3. Energy cost (electricity rate) required to result in a SIR > 1 nationwide CE = CS ÷ (I × 365 days/yr × PW)
  4. Energy cost (electricity rate) required to result in a payback period < 10 years nationwide CE = CS ÷ (I × 365 days/yr × 10 yrs)
  5. System cost required to result in a SIR> 1 nationwide CS = I × 365 days/yr × CE × PW
  6. System cost required to result in a payback period < 10 years nationwide CS = I × 365 days/yr × CE × 10 yrs

Solar Hot Water (SHW)

We calculated and mapped system costs and efficiencies using the following assumptions and equations.

I: Annual average solar radiation on tilt = latitude collector
  where kWh/m2/day = hrs/day, for hours when array is providing peak output,
  e.g. 5.3 kWh/m2/day = 5.3 hrs/day
E: System efficiency = 40%
CE: Energy cost = $/kWh
PW: Present worth = 17.41 yrs
CS: SHW System Costs   $900 per sq. m.
  1. Current SIR given current conditions SIR = ( I × E × 365 days/yr × CE × PW ) ÷ CS
  2. Current payback period given current conditions Payback = CS ÷ ( I × 365 days/yr × CE × E )
  3. Energy cost (electricity rate) required to result in a SIR > 1 nationwide CE = CS ÷ ( I × E × 365 days/yr × PW )
  4. Energy cost (electricity rate) required to result in a payback period < 10 years nationwide CE = CS ÷ ( I × E × 365 days/yr × 10 yrs )
  5. System cost required to result in a SIR > 1 nationwide CS = I × E × 365 days/yr × CE × PW
  6. System cost required to result in a payback period < 10 years nationwide CS = I × E × 365 days/yr × CE × 10 yrs

Solar Ventilation-Air Preheat (SVP)

We calculated and mapped system costs and efficiencies using the following assumptions and equations.

CS: SVP system cost = $151/m2 (retrofit)
ED: Energy delivered = kWh/m2/yr
CE: Energy cost = $/kWh
PW: Present worth = 17.41 yrs
  1. Current SIR given current conditions SIR = ( ED × CE × PW ) ÷ CS
  2. Current payback period given current conditions Payback = CS ÷ ( ED × CE )
  3. Energy cost (electricity rate) required to result in a SIR > 1 nationwide CE = CS ÷ ( ED × PW )
  4. Energy cost (electricity rate) required to result in a payback period < 10 years nationwide CE = CS ÷ ( ED × 10 yrs )
  5. System cost required to result in a SIR > 1 nationwide CS = ED × CE × PW
  6. System cost required to result in a payback period < 10 years nationwide CS = ED × CE × 10 yrs