City of Golden PV Evaluation

Overview

The City of Golden Photovoltaic Evaluation is a project the Golden Solar Solutions team has been assigned to in order to perform a feasibility analysis to help achieve the goal of 100% renewable energy by 2030. The scope of the project has expanded to include the entire plot designated for solar off of Highway 93 and W. 56th Ave. This allows for higher generation, but also presents new challenges for the project. These challenges include interconnection, sloped areas, possible floodplains, and increased project time. To support these aspects of the project, validation has been provided through engineering calculation and analysis and preliminary drawings.

The team approached this project by keeping two important concepts in mind which are sustainability and efficiency. While the project is renewable energy and already a sustainable approach to energy production the team took this a step further by making our components as sustainable as possible along with a focus on the effects the array will have on the environment. There is a direct correlation between sustainability and efficiency as well because more efficient products are sustainable as losses in the system are decreased.

The team focused on array efficiency by minimizing the losses in the system. While an array could have been placed on the entire plot and therefore have a much larger energy output this would have been very inefficient. On the plot of land there is a 400 foot hill on the West side referred to as a hogback. The hogback affects the production of the array during the afternoons when the sun is at its lowest in winter months. To minimize this the team did a shade analysis using Helioscope to see which panels were being shaded. Panels with 10% shading losses were removed from the array. This helped to increase the efficiency of the array. As seen in the top figure to the right, green panels experience no shading.

The team recommends going forward with a phased approach to the array to make implementation easier. The overall array was split into three separate arrays as seen to the right in the second picture. It was important to leave ample space from the current array on the land owned by Clean Energy Collective. Space was also left between each array to allow for wildlife to move through. The phased approach is broken down into the following sections.

Phase One

This section was chosen as phase one due to it being least affected by shading due to the hogback on the west side, it being easily accessible from the access road, being close to the point of interconnection with the grid, and it being among the smaller arrays so it will show the potential for solar energy on the plot.

Phase Two

This section was chosen as phase two due to its close proximity to the road. This array will also include a separate educational array that can be seen in the North most section of phase two. This educational array would be separate from the rest of phase two and allow for Golden and the surrounding areas to come and learn about solar energy.

Phase Three

Phase three is the largest array and would need an extension to the access road for installation. This array is farthest from the point of interconnection and is affected by shade on the west side but has been minimized by our array design. It also may be beneficial to split this array into two phases or two arrays. The team recommends splitting the phase three array in half with the split moving north and south. 

Array Design

The combined three phases of the array will be 12.8 MW DC. The array generates 19.5 GWh per year. The array is a fixed tilt south facing array with a tilt angle of 23 degrees. The top picture to the right shows the plot with a 15 foot setback from a fence line. There is 12 foot spacing between rows to allow for maintenance and to decrease row to row shading. For designing the array the components chosen were the Jinko 580 W split cell panel and the Delta Electronics M125HV inverter. 

Civil Design:

AutoCAD Civil3D was used to draw the existing solar panel, roads, houses, and trees scattered throughout the plot. Contours from DRCOG were collected as a response to the 2013 Colorado flood, and served as a basis for land analysis. Elevations were put in for each contour and trimmed to remain inside of the property line. See the second picture on the right. From there, we were able to create a surface from the contours to provide a 3D view. The slopes vary from 2.7% to 38.9% , but for the purpose of construction the slopes could not exceed 20%. The areas in which the slopes get that steep are in a large divot which cannot be constructed due to being a floodplain. Aside from that section of the plot and the hogback, the land is feasible to work with. 

Racking and Security:

APA Solutions Titan was chosen for the system’s racking because of the portrait orientation of the panels which helps to utilize the split cells of the panels. Titan meets all of Golden’s building standards.

The client was concerned about the arrays restricting animal grazing on the land. Instead of a large fence all around the plot, the team recommends a high security fence near the road with smaller fences surrounding each array. To make up for the decreased security of fencing, the team recommends security fasteners for the panels, panel locks, and motion activated lights within each array.

Interconnection:

The team went forward providing the client with a simplified way to connect with the grid focusing on two main components: the array side overcurrent protection and a transformer to connect to low voltage distribution. Our interconnection, pictured third to the right, is based on phase one but can be replicated for the rest of the phases previously discussed.

Lightning:

Lightning and thunderstorms threaten the array. Designing a suitable lightning rod array will alleviate concerns about longevity and durability. Rods will be designed to ensure they are above all panels, thus ensuring their protection along with surge protectors to ensure lightning does not damage the grid or the connection to the grid. All lightning defense companies the team has contacted have been insistent on developing after the installation of the array. 

Sustainability:

Previous land sustainability options included different agrovoltaic uses like cattle and sheep grazing, bee hives, and flowers. We looked into different options of pollinator plants that can be planted year round for different conditions. These conditions include blooming season, elevation, expected weather, and sun and water needs. All of these variations are valid options for the changing seasons of Colorado.

As for recycling, the team has been researching different options. Solar panels have a lifespan of 20-30 years so their parts will need to be replaced as well as recycled. The most sustainable way to dispose of panels would be through panel recycling. Recycle PV Solar recycles panels, but they are located in Nevada. Panel recycling should be more accessible in 20-30 years.

Cost Analysis:

For cost analysis of this project we looked into the sunk and prospective costs that would affect the system. For the sunk costs we looked into the initial capital costs. These costs include the overall materials needed for the solar system such as panels, racking, wiring, etc. For some of these costs we were able to get estimates from manufactures of the parts we were working with other costs came from the NREL 2020 Q1 Solar PV system cost Benchmark report. Another included sunk cost was that of yearly maintenance and system losses. The prospective costs included the cost of energy produced in kWh a $0.08/ kWh. This also included incentive costing which consisted of a Federal ITC of 22% of the initial capital cost of the system. The capital costs can be seen in the Table pictured fourth on the right and the cash flow generated from our data can be seen in the bottom picture on the right.