Project Process:

The solar powered charging station is the product of Hathaway Brown's 2013-2014 Campus and Community Sustainability class. Below, we describe the questions we had to answer as we moved through the process of designing the system and getting the charging station installed.


Who will use this charging station and how will they use it?

We wanted everyone in the school to be able to use the system and to be excited to do so.  To make sure that the system we designed would meet people's needs and work habits, we started the design process by sending out two surveys, one to faculty and one to students. Both questionnaires requested respondents to explain their preferences regarding the workings and design of the station, as well as what devices they would charge at the station and how often they brought their chargers to school. This information allowed us to construct a system to best accommodate its users. Below you will find the questions we asked and a summary of our findings.

Survey Question 1: Would you be more likely to use a charging station that allowed you to lock and leave your device or that was designed as a community workspace?

This was probably the most important question in the survey, as it would determine the base of the interior design.

A lock and leave station would be a much smaller space, possibly even a maneuverable set-up on wheels. The basics for this design formed around either a permanent installment with several lockable shelves and an interactive display, or a system on wheels to allow users to transport it around and between locations.

A community workspace design was imagined as a series of tables with spaces to neatly plug in devices connected to the solar powered system. This was imagined with an interactive display, but was not in any way able to move and would be for the most part permanent (aside from possible wheels on the bottom of the tables).

As shown by the results of the survey, there was not a dramatic difference in preference between the two set-ups; although the majority preferred a lock-and-leave, a large portion still wanted a workspace. The sustainability class moved to design a system with both tables for public use as well as secure “cubbies” for users to plug in and lock their devices for safe and sustainable charging. Due to time and budget constraints, the final system design only includes a workstation, with the option of installing a lock-and-leave set up in the future.

Survey Question #2: What type of devices do you use?

Knowing what kinds of electronics users would charge at the solar station was critical in determining both the physical look to the workspace (how many outlets to have in the tables or secure shelves in the lock-and-leave) as well as the mechanical and electrical design.

By taking inventory of the most common phones, computers, or other devices, (and the times at which users would be plugging in) the class was able to calculate maximum and average electricity draw. Not only did this help us design a more usable space, but it also gave us data to determine the draw the system would place on the electrical circuit and the number of panels the system would require.

Survey Question #3: What type of cell phone or laptop do you have?

Should we use a grid-tied system or a battery system?

The station can be designed so that the energy we produce is stored in batteries. In this case, the station will only work when the batteries have been charged by the sun. We could also design it so that the energy we produce feeds back into the grid, and essentially supplements the energy we purchase from the grid. In this case, the station will work all the time, whether or not we have been or are producing solar power. More energy is lost between production and use when using the batteries as a storage mechanism.

When we asked the community which type of system they thought we should design, 100% of faculty and staff respondents opted for a grid-tied system, as did 78% of student respondents.  We agreed with the community's recommendations, and ultimately designed a grid-tied system.

How much power do we need?

Once we had decided that we would be designing a grid-tied system, we knew that the tables at our workstation would plug into a centrally located outlet. We next looked at where the outlet would be and what the load would be on the circuit at that location (essentially how many things we could plug in). We chose our location to be in a central area where students and teachers across divisions could have access to the station. To find out what kind of load the station would be putting on the circuit, we first looked at what type of devices would most likely be used at the station and how many amps and watts they would draw. We gathered the information below from various sources on the internet as well as our Kill-A-Watt meter:

Device:

Amps:

Watts:

Versions:

iPhone 4

1 amp

5 watts

4, 4S

iPhone 5

1 amp

6 watts

5, 5S, 5C

iPad 2

2 amp

10 watts

16 GB, 32 GB, 64 GB

iPad mini 2

 

 

16 GB, 32 GB

MacBook Air

 

 

11”, 13”

MacBook Pro

1.5 amp

49-53 watts

11”, 13”, 15”

Lenovo

1.5 amp

45-50 watts

11”

Dell

1.5 amp

34-45 watts

11”, 13”

HP

 

 

11”, 13”, 15” (some 17”)


Using this information, we estimated what type of load would be placed on the circuit. Assuming, there would be 12 laptops and 13 iPads or phones charging at the station, we determined that we should have 25 plugs. (Ultimately, the table design and the space we had available limited the number of plug-in points to 18.)

In order to calculate how many PV modules we would need to supply the power for the charging station, we first had to calculate how much power we thought the station would use over the course of a year.  We decided that we would rather overestimate the power needed than underestimate it, so we based our calculations on the following assumptions:

  • 25 devices plugged in, drawing 30 watts each
  • Devices will be plugged in 10 hours/day (7 am-5 pm), 5 days/week, 40 weeks/year

Based on these assumptions, we estimated the station would consume 1,500 kilowatt hours/year: 

(25 devices)(30 watts)(10 hours/day)(5 days/week)(40 weeks/year) (1/1,000 kilowatts/watt) = 1,500 kilowatt hours/year


How many modules do we need to supply that power?

Once we knew how much power the system needed to generate, we determined how many PV modules we would need to install to generate this power.  To do this, we used the following information:

  • Average number of peak sun hours a day in Cleveland, OH = 4.1 hours/day 
  • Watts generated per module at peak sun = 250 watts
  • Days per year = 365.25
  • System efficiency (percentage of the original power generated that will be available as usable electricity = 77%  (Approximately 23% of the power generated is lost due to system inefficiencies) 

Based on this information, we calculated how many kilowatts of electricity a single module would generate annually:

     (365.25 days/year)(4.1 hours/day)(250 watts)(0.77) = 288,273.56 watts/year

     (288,273.56 watts/year)(1/1,000 kilowatt/watt) = 288.37 kilowatts/year - electricity generated annually by each module

     (1,500 kilowatt hours/year)/(288 kilowatts/year/module) = 5.20 (5 modules)

From these calculations we concluded that the appropriate number of modules for our project was five. 


Where and how will we install the modules?

We needed to choose a place that was in direct sunlight (preferably south-facing), easily accessible, and that had room to expand the system should we want to do so in the future. The solar panels could not be placed on our slate roof, which narrowed down the space available considerably. One placement we considered was on the northern side of the Atrium building (still a south-facing roof), but this was not easily accessible to the public and so was also ruled out. In the end, we chose the link building roof, not only because it is in direct sunlight, but also because it is flat. We also chose it because there is more room to expand the project later with even more solar panels. It can also be viewed from a window in a classroom in the prime, which we thought would be great for educational purposes.

We next had to get approvals on the aesthetics of the station as well as the panel placement. Initially, there were some concerns about where we wanted to place our panels because the roof had recently been redone. An administrator was concerned about potentially putting holes into the new roof. After speaking with the roofing company, however, it was determined that the hole would not be a problem if we placed a cap over it. The roofing company had to inspect the panel installation job once it was complete to verify that the panels were properly installed and that the hole drilled in the roof was properly sealed.  Upon completion of this inspection, the roofing company signed a letter saying the original roof warranty was still intact. There were also concerns about being able to see the panels from the street; however, after deciding on a panel angle of 10°, this was no longer cause for concern. If the panels had been visible from the street, we would have had to delve further into getting approvals from the City of Shaker Heights. Luckily, both of these issues were relatively simple to solve.

What will the interior components look like?

With only $5,000 to design the interior component of this charging station, we had to spend a lot of time researching the furniture we wanted to use. Costs of the furniture added up quickly since we needed seven chairs and a large table. We found out that there were leftover chairs from the middle school “neighborhoods” which would not only be the most cost-effective choice (free) but would also be the most sustainable choice (no new materials being used). We decided to buy the tables from Reclaimed Cleveland because they would be made of local, recycled materials and also look nice. Once we figured out what we wanted the charging station to look like, we had to get approval from the administrators of the school. We held a brief meeting discussing what we wanted it to look like and got their opinion and changed what they thought should be changed.  

How can we educate users about the system and how it works?

One of the most important parts of this project is educating the HB community about what we did and how it works. We decided that the best way to get this information to the public would be via an iPad displaying key websites related to the project (like this one!) placed at the charging station and a larger infographic display above the charging station tables. The iPad/websites provide real-time and historic information about power production from our PV system.  In addition, they link to our weather station, and to descriptions of how we designed the system and how the system actually works. The infographic display targets people who were just walking by the charging station and want a brief overview of what the station is all about. 

How will we pay for it all?

The solar panels were paid for by a grant from Dominion Resources for a total of $3,800.  This grant, with some supplementary funds from the Center for Sustainability instructional budget allowed us to purchase the solar panels, small alternative energy charging devices for use in classroom activities, and materials to repair the weather station that is on the roof near the solar panels. For the interior component of the project, we got $5,000 from the Invention Lab budget at HB.

Shaker Heights, Ohio Girls K-12 Coed Early Childhood

19600 North Park Boulevard Shaker Heights, Ohio 44122 P: 216.932.4214
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