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Minnesota Department of Natural Resources
500 Lafayette Road, St Paul, MN 55155
Project Title: Development of Renewable Energy Strategies
Contract Number: EP3-13
Milestone Number: 8
Principal Engineer: Rob Bergh
Phone: 651.259.5522
Report Date: 4.30.2013
Congressional District (RDF Awardee): Fourth
Congressional District (PV Installations): First, Second, Fifth, Sixth, Seventh, Eighth
Project funding provided by customers of Xcel Energy through a grant from the Renewable Development Fund.
FINAL REPORT
Executive Summary: The Department of Natural Resources (DNR) installed 8 solar photovoltaic (PV) systems
into 7 State Parks and developed a renewable energy interpretive program. This prepared DNR for large-scale
implementation of renewable energy resources by establishing renewable energy design and specification
standards. The success leveraged by this RDF grant is evident. At this point DNR has 25 renewable energy
systems installed across the state and is one of the Top Ten generators of photovoltaic electricity in Minnesota.
DNR has succeeded in implementing renewable energy in a way that is cost effective and environmentally
sustainable, and also in a way that informs and encourages others to apply renewable energy. Our 350 KW of
renewable energy have also made us a significant industry job sustainer.
This grant allowed DNR to achieve five key objectives:
 An assessment process and tool for determining the feasibility and siting of photovoltaic systems that
evaluates multiple technical, environmental and interpretive factors.
 The development of standard designs, specifications and bid packages that have been used on all
subsequent PV projects.
 A system monitoring platform that provides real-time data on solar generation and building energy
consumption. Generation data is available at the total array and individual solar panel level. Automated
system monitoring sends DNR support staff an email when a solar panel has failed.
 Installation of 99 KW of photovoltaic generating capacity. DNR was actually able to install 113 KW
because of cost-effective design strategies and favorable industry trends in photovoltaic panel pricing.
 A renewable energy interpretive program that includes demonstrations, interpretive signage, rack card
brochures and an interactive, touchscreen display at each park.
The centerpiece of DNR interpretive efforts is an interactive website. With a theme of Energy-Smart, this new
site (http://www.dnr.state.mn.us/energysmart) lets visitors in our Parks or across the web learn about energy at
DNR including:
 Our renewable energy systems: where they are, how much energy they’re producing and how they work
 The economic and environmental benefits of renewable energy
 DNR strategies to reduce energy usage in our buildings and fleet
 What Minnesotans can do themselves to reduce energy.
The outcomes of this project have exceeded our expectations. We have received very positive feedback on our
website and attendance and engagement at interpretive events has been excellent. Thanks to this RDF Grant
renewable energy is now an integral part of DNR’s sustainability strategy.
Lessons Learned: Two important lessons learned have broad applicability.
Use of micro-inverters. Traditionally solar panel outputs were combined at the array and high-voltage, direct
current electricity was sent to a single central inverter inside the building for conversion to the alternating
current electricity that powers our lights, appliances, etc. About four years ago a new generation of technology
was introduced called the micro-inverter. Each solar panel is paired with a micro-inverter to convert the direct
current produced by the panel to the alternating current used on the electric grid. The micro-inverter has proven
to have several key advantages:
 Can provide more energy than traditional inverters. In an “apples to apples” comparison in the summer
of 2012 at our Gilbert, MN site 16 micro-inverter equipped PV panels produced 105% of the energy
produced by 16 PV panels using a traditional inverter.
 No single point of system failure. Failure of a traditional central inverter means loss of all energy
production.
 Simpler design, installation and management.
 Safer because of low voltage DC and standard AC, instead of 600 volts DC with traditional inverters.
No guarding or fencing is required for the wiring of micro-inverter based arrays.
 Provides performance monitoring at the individual PV panel level, not just at the entire array level.
Without panel-level monitoring how would we ever know that one of 165 panels had failed?
 Future proofing. Let’s say we have to replace a solar panel 10 years from now and it is no longer
available. With a central inverter you would have to carefully research the available panels to find one
that has similar physical and electrical characteristics to the rest of panels. A mismatched panel could
severely reduce the output of the array. With micro-inverters you could substitute any available
panel/micro-inverter combination that could physically fit. The 240 volt AC output is electrically
compatible with all the other panels.
The only issue we had with micro-inverters was found and resolved on our first installations. Voltages increase
across each micro-inverter in a branch circuit that typically has up to 15 micro-inverters. What we found, along
with the rest of the industry, was that the voltage at the end of the branch circuit could rise to a level that caused
the last few inverters to shut down. The solution to this is to connect to the branch circuit in the middle of the
string of micro-inverters rather than at the end. The installer of our first three systems was required to rewire the
arrays from end-fed to center-fed branch circuits.
Value of system monitoring. DNR has developed a system monitoring platform that provides real-time data on
solar generation and building energy consumption. There are four major benefits of system monitoring for
DNR. The generation data at both the array and panel level is essential for effectively managing the hundreds of
solar panels DNR has around the state. Many of these systems are geographically remote from the trained
support staff in St Paul. Panel level monitoring features the ability to automatically send an email to report an
error condition. Building energy consumption monitoring allows building occupants to observe how their
behaviors impact energy usage. We have consistently seen that in the 60 – 90 days following the installation of
building energy monitoring the building’s overnight power usage decreases as PC’s are powered off, coffeepots
unplugged, power strips installed, etc.
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The third major benefit of system monitoring is in support of DNR interpretive efforts. The real-time graphs of
generation and usage make the concept real for visitors to our parks and website. We are also able to retrieve
data from our energy submeters every half hour to build a consolidated, statewide picture of how much energy
we are generating and using. The fourth major benefit of system monitoring is the ability to retrieve and analyze
historical data. Analyses of history data downloaded from energy submeters allow DNR to compare and
contrast the performance of different types of solar panels and inverters over time. Different mounting methods
and angles can be analyzed, as well as the impacts of snow cover and panel soiling. DNR makes this data
available to the public and has supplied data to industry researchers.
Usefulness of Project Findings: This project placed eight photovoltaic systems in highly visible locations in
Minnesota state parks. Static signage and a content-rich, interactive website serve to de-mystify the technology
and encourage visitors to consider ways to generate their own renewable energy and reduce their energy usage.
More renewable energy means cleaner air and more jobs in Minnesota. Distributed generation of electricity can
increase the ability of the grid to handle peak loads on hot, sunny days. This project has increased the
photovoltaic knowledge base in the areas of micro-inverter installation best practices and system monitoring,
along with making publicly available a rich set of photovoltaic performance data.
Summary of Benefits: The 113 KW installed under this Grant will generate about 150,000 kWh each year,
reducing DNR annual operating expenses by $15,000. Over 107 metric tons of carbon emissions will be
avoided each year. At this point DNR has 25 renewable energy systems installed across the state and is one of
the Top Ten generators of photovoltaic electricity in Minnesota. DNR has succeeded in implementing
renewable energy in a way that is cost effective and environmentally sustainable, and also in a way that informs
and encourages others to apply renewable energy. Our 350 KW of renewable energy have also made us a
significant industry job sustainer.
System Installations: The eight photovoltaic systems are summarized below.
Lac qui Parle Wildlife Management Area has a 16.1 kW, ground-mounted, photovoltaic system south of WMA
HQ building. It has generated almost 50,000 kWh since it was installed in October 2010.
Afton State Park has a 15 kW, ground-mounted, photovoltaic system by the Contact Station. It has generated
almost 40,000 kWh since it was installed in October 2010.
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Lake Shetek State Park has a 13.8 kW, roof-mounted, photovoltaic system at the new Sunrise Campground. It
has generated almost 40,000 kWh since it was installed in December 2010.
William O’Brien State Park has two photovoltaic installations. The 38 kW system by the Contact Station is
made up of three photovoltaic ground mounts, and the other is a 9.9 kW roof mount at the Visitor Center. They
have generated almost 115,000 kWh since they were installed.
Fort Snelling State Park has a 3.6 kW, roof-mounted, photovoltaic system at the Visitor Center. It has generated
almost 8,500 kWh since it was installed in December 2010.
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Nerstrand Big Woods State Park has a 7.2 kW, ground-mounted, photovoltaic system by the Visitor Center. It
has generated over 10,000 kWh since it was installed in December 2011.
Wild River State Park has a 10.1 KW photovoltaic system by the Contact Station. These Minnesota-made solar
panels have generated about 2,500 kWh since being installed in November 2012.
Renewable Energy Interpretive Program
One of our major objectives is to inform and engage the public about renewable energy in a comprehensive
fashion that includes demonstrations, interpretive programming and displays. The centerpiece of DNR
interpretive efforts is an interactive website. With a theme of Energy-Smart, this new site will let visitors in our
Parks or across the web learn about energy at DNR including
 Our renewable energy systems: where they are, how much energy they’re producing and how they work
 The economic and environmental benefits of renewable energy
 DNR strategies to reduce energy usage in our buildings and fleet
 What Minnesotans can do themselves to reduce energy.
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The Energy-Smart main page is located at: http://www.dnr.state.mn.us/energysmart. Figure 1 shows the main
page and the wide range of energy topics available across the site. DNR has built its own energy monitoring
database that is fed by renewable energy submeters across the state. The main page shows total generation and
usage data for all DNR locations with renewable energy systems. Interactive charts driven by the database
allow you to see how much energy these sites have generated and used on day, week, month and year
timeframes. Figure 2 shows a typical solar energy page that presents information, pictures and generation/usage
data for the site. These pages are table-driven so the addition of a new site requires no additional programming.
Figure 3 shows the page explaining how solar energy works. Information is available at multiple levels of depth
and detail to accommodate different user expectations and interests. Figure 4 show information on the
economic benefits of renewable energy for individuals, businesses and the state of Minnesota. An interactive
Solar Energy Payback Calculator is available to explore the financial benefits of renewable energy.
Interpretive signage, rack card brochures and a touchscreen computer are available at DNR sites with renewable
energy and interpretive programs have been conducted at several locations. Interpretive naturalists are being
trained and have presentation materials to tailor.
Figure 1: Energy Smart Home Page
Figure 1: Main Page
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Figure 2: Solar Energy Site Page
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Figure 3: How Solar Energy Works Site Page
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Figure 4: Economic Benefits Site Page
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LEGAL NOTICE
THIS REPORT WAS PREPARED AS A RESULT OF WORK SPONSORED BY NSP. IT DOES NOT
NECESSARILY REPRESENT THE VIEWS OF NSP, ITS EMPLOYEES, OR THE RENEWABLE
DEVELOPMENT FUND BOARD. NSP, ITS EMPLOYEES, CONTRACTORS, AND SUBCONTRACTORS
MAKE NO WARRANTY, EXPRESS OR IMPLIED, AND ASSUME NO LEGAL LIABILITY FOR THE
INFORMATION IN THIS REPORT; NOR DOES ANY PARTY REPRESENT THAT THE USE OF THIS
INFORMATION WILL NOT INFRINGE UPON PRIVATELY OWNED RIGHTS. THIS REPORT HAS
NOT BEEN APPROVED OR DISAPPROVED BY NSP NOR HAS NSP PASSED UPON THE ACCURACY
OF ADEQUACY OF THE INFORMATION IN THIS REPORT.
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