Module 2: Text Versions

Below are the video text versions for Module 2 of the City and County Solar Photovoltaics Training Program.


Your project potential is determined by a number of variables, such as PV resource, roof and land availability, energy utility costs, inflation and escalation rates, and state incentives and policies. Understanding what's needed to analyze any given site will set your projects up for success. We'll show you the steps, data, and tools required to screen available PV sites.


>>Emma: Welcome to module two of the city and county solar PV training program. My name is Emma Helquist and I'll be your host for today. The topic of this module is "Screening and Identifying PV Projects," and today we'll talk about the different drivers of PV project potential and how you can assess your site using energy modeling tools that incorporate these drivers. Once you've completed this module you'll be able to understand the different factors that impact the technical and economic potential of a PV project, the steps of the PV screening process, and how to use REopt Lite to screen your site for PV and storage project potential.

Once you've set your energy goals and formed a strong project team it's time to screen sites to identify potential projects. The purpose of a screening is to quickly and efficiently down-select to viable technologies and sites. This reduces potential costly investment of time and money in unlikely projects. A screening provides an initial indicator of technical and economic viability in initial go/no-go decisions.

Let's start by talking about the drivers of PV potential that determines if PV will work for your site. There are many factors that determine if PV will work for your site. This includes your solar resource or how much energy a solar project will produce given your location; the cost of solar technologies and applicable incentives or how much you'll be paying for the project; the space that you have available or how large of a project you'll be able to consider; your utility cost and consumption or what the solar project will be offsetting; and finally, the financial parameters which determine the cost effectiveness. Each of these factors needs to be considered when evaluating PV at your site, and I'll be going into more detail about each of them in the next few slides.

One of the factors determining if PV is a good fit for your location is the magnitude of the solar resource. Research maps like the one shown here give you a high level picture of how the solar resource varies throughout the United States. You can see that the highest solar resource is in the Southwest, while the Pacific Northwest has the lowest solar resource. However, compared to other renewable energy resources, the solar resource only varies by a factor of less than two. As a result, solar projects are being implemented across all 50 states.

The NSRDB data viewer shown here allows users to explore the solar resource across the US and other countries in a general region or at a specific location. The zoom feature allows users to get a more granular view of their solar resource than a static map would typically provide. Note the link to the NSRDB viewer at the bottom of the slide. This link along with other resources are provided in separate document that you can access after you've completed this module.

Another great source for estimating the solar resource at a particular location is a tool called PVWatts. With just a few simple inputs including the site's location and system configuration the user can get a sense of both the annual and hourly energy generation of a potential PV system.

Another important driver of PV project potential is the cost of the technology itself. It's important to consider the total installed cost, which includes not only the PV module but also the inverter and other hardware components as well as soft costs such as labor, taxes, and overhead. This chart shows the total cost declines in residential, commercial, and utility-scale PV costs over the past eight years. In general, larger systems are cheaper on a per-kilowatt basis. These are US average costs, but PV costs can also vary by geographic location and installer.

Incentives can help lower the total cost of a PV system. Common incentives include capacity incentives, which are based on the total installed size of the PV system; production incentives, which are based on how much electricity the system in generating; and net metering incentives, which gives you bill credits, even if the PV production exceeds your load at a particular time. This map shows the 38 US states and territories that have some form of net metering incentives. The Database of State Incentives for Renewables and Efficiency, or DSIRE, is a great resource for staying up to date with incentives in your area.

You'll also need to know how much space is available for a PV project. A PV system is typically roof-mounted, ground-mounted, or installed as part of a carport. Shown here is a site interested in PV that has identified the carport area in pink, roof area in blue, and ground area in green. Where you install the PV system impacts the density, or how many panels you can fit in a given area. The cost of the system? Ground-mounted systems are typically the cheapest, while carport systems are typically the most expensive. The tilt and orientation of the system and the viewshed of your site. Project Sunroof is a tool that can be used to estimate how much PV fits on your roof. Just type in your address and you'll get a snapshot of the area available for PV and whether or not that area is shaded.

Your current utility cost is perhaps one of the most important factors in deciding if PV is going to work at your site. Compared to the PV resource, which varies by a factor of two across the United States, utility costs can vary by a factor of up to ten. But it's not as simple as just dollars per kilowatt-hours. There can be many components and different types of charges on your electricity bill, and installing PV impacts those charges differently. The energy charges are determined by the amount of electricity that a site consumes. PV can reduce the amount of electricity purchased, and therefore this charge. Just be aware that the energy charge can vary depending on the season and time of day.

Another common component is demand charges. This is billed not on the total energy consumption but on the highest amount, typically per month. PV can help reduce demand costs if the PV production coincides with peak demand. Finally, fixed charges are common components of electricity bills, but PV cannot offset these.

The map on the left shows the maximum demand charge for each US utility territory. These can vary from zero dollars per kilowatt to over $30.00 per kilowatt. You can find information about your utility cost and structure on your bill, but also through the utility rate database, which lists the rate structure and costs for over 47,000 US utility rates.

We're now going to look at an example of how PV and storage can be used to offset energy and demand charges. Shown in black on this graph is a site's electrical load for one week. The electricity use increases during the day and decreases at night. The area under this curve is the total electricity production. The electricity purchased from the grid is shown in gray. The PV system in orange is offsetting some of this electricity during the day when the sun is shining. By doing so, it's offsetting electricity charges on the utility bill. The demand charge is determined not by the area underneath the curve but by its maximum height. As you can see in this example, the PV system is not generating electricity at the time of maximum demand, and therefore not offsetting demand charges.

Unlike PV, storage can be dispatched in the evening when the sun is now longer shining. By doing so, it can be used to mitigate demand charges. In this example, by adding a small storage system shown here in blue, the sits is able to reduce its demand charges.

Finally, financial parameters impact the long-term cost effectiveness of PV. The inflation rate impacts future O&M costs. The utility cost escalation rate impacts the future cost of energy that the PV system is offsetting, and the discount rate impacts the financing cost of the project. The chart here shows the impact that the utility cost escalation rate can have. A site's rate of $0.06 per kilowatt-hour today is projected to increase to somewhere between $0.09 and $0.15 per kilowatt-hour over the next 25 years, depending on the utility cost escalation rate used. EIA is a good resource for utility cost escalation rate information.

We are now going to go over the general PV screening process. You would first start by defining the goals of the analysis. As you learned in module one, there are many nuances to renewable energy goals and these can impact your analysis. Next, you would collect and review your site data. This can be somewhat time consuming, so keep in mind that you can start with readily available data and only obtain more detailed data if the project appears feasible. You would then run the analysis. This is an iterative process where you adjust the data and run additional analysis to refine your results. Finally, you can use this information to identify sites for more in-depth assessment.

To recap, the purpose of a screening is to quickly and efficiently down-select to viable technologies and sites and to reduce potential costly investment of time and money in unlikely projects. An initial screening provides go/no-go decisions and indicators of technical and economic viability. An initial screening doesn't provide final answers or investment grade audit results. PV modeling and analysis tools can help evaluate your site's potential. They are comprehensive in that they take into account all the factors that we talked about today. Listed here are four tools that can be used to gauge initial potential, optimize system sizing, and refine project economics. They vary in the expertise needed, inputs required, and key outputs provided.

Today, we're going to take a closer look at REopt Lite, a free-to-use tool that was recently released by NREL.

Case Study

I'm Theresa Worsham and I'm the city of Golden's Sustainability Coordinator.

We've got a 154 kW solar photovoltaic system that the city built in 2013.

It's part of a larger project and this one is built, actually, on two carports and it's a total of about 520 panels.

As I mentioned, this is one of nine projects that we built in 2013 and 2014 as part of our effort to meet our renewable energy goals as an organization.

My role was to coordinate the overall contract and oversee some of the construction of the nine different sites and to communicate the financial analysis to our city boards and commissions.

We analyzed more than 30 buildings and their energy consumption and combined that with the renewable energy credits that were available at the time from the utility.

And, these nine sites kind of came to the top and were the most favorable return on investment.

So, that is how this site was chosen.

Plus, the Splash water park was an ideal candidate for construction because it had plenty of room and it needed some shade.

We looked at other areas at this site, ground-mounted sites, but then when we had the idea that this could be a dual benefit, provide shade and generate electricity at the same time, we started looking at what it would take to build these carports.

The carports themselves added about 16% to the overall cost of the project, but we feel that the benefit of having the shade, especially in the summer, that the overall cost increase was worth it.

After considering a few loan options that are available to local governments, we decided to finance this using internal city funds.

We used some surplus revenue from one fund and loaned to this project and so, the original fund makes a little bit more interest than they normally would and at the same time, this project got a lower interest rate than we would have seen on the open market.

So, it was a win-win for the city.

Our return on investment calculates the energy savings that we would've spent if we had not had the solar and we combined that with the rebates offered by the local utility and we came up with a return on investment for 16 years and we're on track to pay that off.

This was the second phase of an existing energy services contract so we were really familiar with this particular vendor and we had successfully worked with them in the past.

But we also had some subcontractors — solar installers — that we hadn't worked with on this project.

Golden has a policy for locally owned companies and so we had many more subcontractors on these nine projects than we were used to so we did have to oversee and juggle multiple contractors.

But the main general contractor we had worked with before and they did a great job of coordinating schedules.

I think one of the main challenges is that this is a combination of rebates, renewable energy credits, and rate changes and to juggle all of those and make sure that those are accurately put into place after the project is complete is an important part of the follow-up and that's one of the main challenges that we had.

Some of those rebates were missed and we had to make sure that they got put into place in order to meet that return on investment.

I think one of the unique things about this project is that it was completed through a state of Colorado oversight program for an energy services contract.

A lot of local governments already know about that type of program but what they might not realize is they can use that type of program for all of their solar needs.

The state of Colorado oversees and licenses companies to do energy services contracting for local governments and publicly owned institutions.

Typically, those are energy efficiency projects but you can also use that type of program for solar.