FAQ for MadiSUN Solarmap

Who created the solar map?

The solar map was created by Critigen and the City of Madison as part of the U.S. Department of Energy "Solar America Cities" program. The solar map was created in 2010.
The map only has limited updates by city staff. There is no maintenance and technical update. We plan to implement new features when new LiDAR data become available (est. 2015).
We will evaluate new features that will become available. Like any internet application, this solar tool will show its true potential once users use it and become creative in applying it. Some of the features we want to implement are:

LiDAR (Light Detection And Ranging) data with 9 ft resolution, acquired in 2005, was used to determine elevation of obstacles (i.e. buildings, trees, ground).
Based on these elevation data and the astronomic sun path, the annual sunshine duration hours were determined. An alternative would have been to integrate the total annual radiation. Both methods have drawbacks and the duration time method was considered to be less misleading for the user:

Integration of annual radiation would have shown south-facing roofs more favorable than a ground location with the same shading because it would have assumed a 0° slope for the ground-mounted system and a south-facing slope for the roof. This method always assumes the solar array to be in the same slope as the ground or structure underneath.
The duration method does not take into account the intensity of radiation that depends on angle of incidence. A slightly north-facing roof actually has more hours of exposure than other roof directions because in summer the sun rises in North-East and sets in North-West. However, this method treats ground locations the same as roof locations
With the data given and the computational resources available the duration method is easier to use since the user will intuitively know not to have a solar system face North and the actual slope of an array easily can be adjusted. In addition, the user more often has to decide between ground and roof installation. Sample calculations were done for both methods and the duration method showed more realistic results in judging how shaded a location is.

Depending on the actual location of the LIDAR points, minor obstacles can be overlooked. The LiDAR data available are from 2005 measurements. It is anticipated to have new data in 2015. Depending on the resolution available then, more features and options can be added.
Trees only are displayed in their current height. There is no determination of mature growth height and the solar installer needs to manually account for future growth. The same applies to any high-rise construction that happened after the LiDAR data were obtained.

The tool IMBY (In My Back Yard) developed by NREL (National Renewable Energy Laboratory) is employed to draw the array and perform estimations of energy production. IMBY is based on the NREL PV-Watt calculator.
IMBY uses average weather and radiation data to simulate a PV system. Solar Thermal systems are not modeled. The tool has the following limitations:

Actual shading shown is not taken into account. The user is encouraged to only install arrays in non-shaded areas.
Currently the user must estimate azimuth and slope of the array. An automatic reading of the slope from the LiDAR data is not implemented.

Owners of solar systems can volunteer their information to be listed on the solarmap. There is no requirement to do so.
If you want to be listed, please visit MadiSUN Solar Energy Program

The solar map uses technologies that conform to webs standards. Unfortunately not all browsers follow the standards.
At the time of creation of the solar map (2010) all major browsers were tested and all features worked (for IE 8 only in compatibility mode). However, over time new browsers use different standards and features not known at the time of the creation of the solar map. Because the solar map does not get updated, some future features might not work as expected. In such cases we recommend to use the compatibility mode of the browser or to try out different browsers.

When the solarmap was developed in 2010, the then current incentive and rebates were considered. Because the solarmap functions won't be updated a relatively open system with user input was created. This also allows using different utility programs and different types of owners. Incentives, tax rebates etc. depend a lot on if the owner is residential, commercial or non-profit and the size of system.
IMBY, the engine calculating energy production, originally employs automatic data from DSIRE to make financial calculations. However, those data are wrong and a correct and up-to date function could not be guaranteed.
The default data shown after drawing an array can and should be altered. In 2010 incentives were based on estimated production. When this scheme changes a workaround can help. For example:

If the incentive is based on installed size, this incentive can be calculated and subtracted from the purchase price. For instance, at a calculated $ 600 rebate per kW installed, one could enter a purchase price that is $ 0.60 lower than the actual price.
Alternatively one could adjust the per-kWh incentive. A 1-kW non-tracking system produces approximately 1,200 kWh annually. At $ 600 per installed kW this translates to $ 0.5 per produced kWh.
If the incentive takes into account shading (and IMBY doesn't) one could subtract the same percentage from the expected revenue.
If a tracking system is considered one could multiply the expected revenue by 1.25 or other appropriate factor and adjust for the higher installation price.

These are just some examples how any future rebate and incentive schemes could be handled with the tools available.
Like with any workaround, one has to be careful to not double-dip. If the result looks too good, financially speaking, it probably is. One incentive could be excluded by the other and the entities giving incentives (i.e. IRS, Focus on Energy, utilities) should be consulted to learn of the rules.
Please consider that the solarmap is an estimate tool only and financial decisions should be made with other means. There is no internet tool that can give reliable financial advice without taking into account the actual situation of the user. Please consult experts before making any financial decisions. Under no circumstances we claim any accuracy not give any financial advice.