SOLAR TODAY

ISSUE HIGHLIGHTS

Rethinking Solar Water Heating in an Age of Booming PV
SWH could relieve utility stress about the challenges of integrating so much PV, so fast.
By Jill K. Cliburn and Joe Bourg

Affordable Net-Zero-Energy in Outlying D.C.
By minimizing construction and utility costs, the North Pointe homes in Frederick, Md., offer low-cost living  quite a feat in metro Washington, D.C.
By V. Paul Zanecki

Relieving a Glaring Problem
Proper design and siting of solar energy installations is probably the most effective way to mitigate potentially hazardous glare.
By Clifford K. Ho

Squeezing Utility Bill Savings from Commercial PV
Net metering or power purchase agreement? It depends on the customer and utility, but a study of North Carolina commercial customers finds that selling the PV generation yields the best savings, thanks to onerous net-metering charges.
By Kacey Hoover

Power Forward at SOLAR 2013
The 42^nd ASES National Solar Conference gets down to business in Baltimore, Md., April 16–20.
ASES staff

Innovators
Acting Against Coal
By Seth Masia

Investing
Japan’s Big Leap Forward
By Rona Fried, Ph.D.

The trade
Model Zoning Ordinances for Small Wind Turbines
By Mick Sagrillo

New Products
SOLAR 2013 Products Preview

System Accomplished
Do-It-Yourself Pays Off for UPS
By Seth Masia

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The orientation of installed panels can have a significant impact on energy produced, particularly in winter months. This is illustrated in the map, “Energy Gains with Tilted Panels,” which shows the increase in energy production achieved by tilting solar panels 30 degrees as compared to positioning panels with zero tilt, or horizontally.

As illustrated by the map, tilt-mount PV systems generally have the greatest benefit in northern states, which experience lower sun angles during the winter. This gain is dampened where clouds are prevalent. For the month of November, relatively sunny conditions in the upper Midwest and northeastern United States led to the highest gain in energy production with tilt-mount vs. horizontal-mount PV, with as much as an 80 or 90 percent increase in some locations.

To use the PV Power Map to calculate the generation potential of a PV system in a given location, multiply the power output indicated on the map by a project’s capacity, in kilowatts. The result is the total estimated power output for the month. PV Power Maps can be seen for the entire year at pvpowermap.solartoday.org.

The PV Power Map is created with power output estimates generated by SolarAnywhere services from Clean Power Research; these include simulation capabilities and hourly satellite-derived irradiance data with spatial resolutions from 1 to 10 kilometers. The calculations are based on a PV system with a total 1-kW nameplate rating that is configured as five 200-watt PV panels with a 1.5-kW inverter; fixed, south-facing panels with 30 degree tilt; no shading; panel PVUSA Test Conditions rating of 178 watts; and inverter efficiency of 95.5 percent. Visualization and mapping provided by GeoModel Solar. Access free historical irradiance data at solaranywhere.com.

The PV Power Map is a report of national solar resource availability as illustrated by the monthly energy output of a nominal 1-kilowatt (kW) photovoltaic (PV) system by location. As illustrated by the map, much of the Western United States experienced warm and dry weather conditions, which facilitated average-to-above average solar energy production. The Eastern United States experienced wetter and cloudier conditions for the month, which led to average-to-below solar energy production profiles prevailing throughout much of the region. The Ohio River Valley in particular recorded below average energy production due to an active storm pattern.

To use the PV Power Map to calculate the generation potential of a PV system in a given location, multiply the power output indicated on the map by a project’s capacity, in kilowatts. The result is the total estimated power output for the month. See an archive of monthly PV Power Maps at solartoday.org/pvpowermap.

The PV Power Map is created with power output estimates generated by SolarAnywhere services from Clean Power Research; these include simulation capabilities and hourly satellite-derived irradiance data with spatial resolutions from 1 to 10 kilometers. The calculations are based on a PV system with a total 1-kW nameplate rating that is configured as five 200-watt PV panels with a 1.5-kW inverter; fixed, south-facing panels with 30 degree tilt; no shading; panel PVUSA Test Conditions rating of 178 watts; and inverter efficiency of 95.5 percent. Visualization and mapping provided by GeoModel Solar. Access free historical irradiance data at solaranywhere.com.

The PV Power Map is a report of national solar resource availability as illustrated by the monthly energy output of a nominal 1-kilowatt (kW) photovoltaic (PV) system by location. Summer 2012 showed high solar resource availability across the United States, particularly in July. High irradiance generally also means high temperatures, which drives higher power demand for cooling. One benefit of solar is that it coincides with these peak demand periods, providing substantial value by generating power when it’s needed most.

In areas with tiered electric rates, solar power generation reduces the need to purchase power at the highest rates through peak demand reduction, increasing the financial benefit. For example, in New York, where electricity costs more during peak hours, a homeowner with a 3.5-kW system, with base electricity consumption of 625 to 750 kilowatt-hours per month in July and August, could have saved as much as 70 to 80 percent off their electric bill, even though solar offset would have decreased their utility consumption by 65 to 75 percent. Peak reduction can have benefits at the utility level, as well. For example, as described in the paper “Solar Power Generation in the U.S.: Too Expensive, or a Bargain,” by Richard Perez, Ken Zweibel and Tom Hoff, the August 2003 Northeast blackout could have been averted with as little as 500 megawatts of solar PV installations dispersed throughout the region. (Download at bit.ly/SpAlNY.)

To use the PV Power Map to calculate the generation potential of a PV system in a given location, multiply the power output indicated on the map by a project’s capacity, in kilowatts. The result is the total estimated power output for the month. See an archive of monthly PV Power Maps at solartoday.org/pvpowermap.

The PV Power Map is created with power output estimates generated by SolarAnywhere services from Clean Power Research; these include simulation capabilities and hourly satellite-derived irradiance data with spatial resolutions from 1 to 10 kilometers. The calculations are based on a PV system with a total 1-kW nameplate rating that is configured as five 200-watt PV panels with a 1.5-kW inverter; fixed, south-facing panels with 30 degree tilt; no shading; panel PVUSA Test Conditions rating of 178 watts; and inverter efficiency of 95.5 percent. Visualization and mapping provided by GeoModel Solar. Access free historical irradiance data at solaranywhere.com.

The PV Power Map is a report of national solar resource availability as illustrated by the monthly energy output of a nominal 1-kilowatt (kW) photovoltaic (PV) system by location. The May and June maps illustrate the Great Lakes dampening effect commonly seen in warmer months. By dampening cloud formation, the Great Lakes’ cold water results in greater solar potential than other regions, such as the Eastern seaboard. For example, total power output of a 1-kW system in New York City and Miami during this time period was approximately 250 kilowatt-hours (120 + 130 kWh) and 230 kWh (120 + 110 kWh) respectively. Compare that to Chicago, where a 1-kW system produced approximately 305 kWh (150 + 155 kWh).

PV Power Maps can be seen for the entire year at solartoday.org/pvpowermap. Taking a look at the first six months of the year, solar potential for cities as diverse as Chicago, New York, Miami, New Orleans and San Francisco were all very similar, with total estimated power output of a 1-kW system ranging from 715 to 765 kWh. Of these cities, Miami had the least variance from month to month, while Chicago saw the largest variance. The southwest region consistently experienced the highest potential, with a 1-kW system in Phoenix producing an estimated 960 kWh.

To use the PV Power Map to calculate the generation potential of a PV system in a given location, multiply the power output indicated on the map by a project’s capacity, in kilowatts. The result is the total estimated power output for the month.

The PV Power Map is created with power output estimates generated by SolarAnywhere services from Clean Power Research; these include simulation capabilities and hourly satellite-derived irradiance data with spatial resolutions from 1 to 10 kilometers. The calculations are based on a PV system with a total 1-kW nameplate rating that is configured as five 200-watt PV panels with a 1.5-kW inverter; fixed, south-facing panels with 30 degree tilt; no shading; panel PVUSA Test Conditions rating of 178 watts; and inverter efficiency of 95.5 percent. Visualization and mapping provided by GeoModel Solar. Access free historical irradiance data at solaranywhere.com.

The PV Power Map is a report of national solar resource availability as illustrated by the monthly energy output of a nominal 1-kilowatt (kW) photovoltaic (PV) system by location. This issue highlights the difference in real-time production when compared to annual averages. The first map illustrates total estimated power output for the month of April 2012. The second shows the average monthly PV power output in 2011.

It’s a given that solar resources can vary on an hourly basis, but a comparison of these two maps shows that local differences in any given month can also be considerable. While April is typically close to annual averages, production in April 2012 throughout the U.S. Northeast and Midwest outpaced the average monthly production for 2011.

The April PV Power Map was created using real-time irradiance estimates that provide an accurate depiction of current weather conditions. This information is most useful for assessing the actual production of an existing PV power production system. The monthly average value, which in this case was calculated by averaging annual total PV power output by location, is best suited for comparing long-term performance of potential PV sites.

To use the PV Power Map to calculate the generation potential of a PV system in a given location, multiply the power output indicated on the map by a project’s capacity, in kilowatts. The result is the total estimated power output for the month.

To reference maps throughout the year, go to solartoday.org/pvpowermap, or access free historical irradiance data at solaranywhere.com.

The PV Power Map is created with power output estimates generated by SolarAnywhere services from Clean Power Research; these include simulation capabilities and hourly satellite-derived irradiance data with spatial resolutions from 1 to 10 kilometers. The calculations are based on a PV system with a total 1-kW nameplate rating that is configured as five 200-watt PV panels with a 1.5-kW inverter; fixed, south-facing panels with 30 degree tilt; no shading; panel PVUSA Test Conditions rating of 178 watts; and inverter efficiency of 95.5 percent. Visualization and mapping provided by GeoModel Solar.

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This article appeared in the July/August 2012 issue of SOLAR TODAY. Subscribe today and don’t miss an issue.