Figure 22: 25kW System Cash Flow Figure 6 depicts the total cash flow of the 25kW array. The

37 “Commonly Observed Degradation in Field-Aged Photovoltaic Modules.” Quitana, M.A.; King, D.L..; McMahon, T.J. and Osterwald, C.R.










Figure 13: Solar panel efficiency over time
Based on these two studies, we have decided to use the average of their results, and estimate 0.6% annual degradation.
Because solar panels contain no moving parts maintenance costs are found to be extremely minimal. Due to the fact that the lifetime warranties of solar panels are generally found to be twenty years or more, it is unlikely that any maintenance costs will be realized within this time span. The cost of maintaining an array will generally reside in labor, not replacement parts. Thus, maintenance costs for solar systems are estimated at costing 4% of the initial system cost.38 The “Incentives and Rebates” section is straightforward and its content is taken directly from MTC’s economic spreadsheet. It describes the total MTC rebate based on the system size, whether or not the building is public (churches are not considered public in this case), and whether or not the components are manufactured in Massachusetts. This rebate will most likely be $3.25 per Watt for Wesley United Methodist Church. Unfortunately, the MTC rebate is the only incentive applicable to the church, because all other aid is in the form of tax incentives.
38A Rural Electric Co-op’s Experience with Photovoltaic Systems for Livestock Water Pumping, Skinner, Rolland http://www.usda.gov/rus/electric/engineering/sem2002/skinner.htm
Section five, “Financing” allows the option for testing how the feasibility of a system changes by using a loan. This section requires the percentage of the entire loan that the down payment makes up, the interest rate, and the loan term. It assumes that a fixed rate mortgage will be used, and calculates the monthly payment. If you wish to not use any financing, simply put down that the down payment makes up 100% of the loan.
Section six deals with energy cost. The current cost of electricity was based on recent electricity bills from Wesley United Methodist Church. Current electric rates are $0.16 per kWh. The energy cost adjustor, or the amount that electricity costs will increase each year was determined based on historical data from the Energy Information Administration39. Data for the national average cost per kWh from 1973 to 2007 was taken and plotted to show the trend over time.
39 Average Retail Prices of Electricity, Energy Information Administration http://www.eia.doe.gov/emeu/mer/prices.html

Figure 14: Historical prices of the national average cost per kWh.
We initially expected an exponential increase in energy cost, or a certain percentage per year, however, the data clearly shows a linear increase of about $0.0018 per year. It is possible, and in fact likely, that energy costs will increase more rapidly in the future, though, as we begin to run out of fossil fuels. However, we will use the historical data as a way to predict future increases. The data above is taken at a national level and the costs of electricity can vary at a local level, based on the competition between companies, demand, and distribution fees, however, energy price trends happen at a national level. We have addressed this by taking the starting value for our predicted energy costs to be the present cost of electricity from one of Wesley United Methodist Church’s recent bills. We then estimated that this current cost of $0.16 per kWh would increase at a rate of $0.0018 kWh per year as the national data predicts.
The last section in the economic spreadsheet requiring input is the “Economic Factors” section, which calls for an estimation of the average inflation. This was determined by looking at historical data for the Consumer Price Index (CPI)40. The CPI was at 10 in 1914, and ended up at 217 in 2008. The percent change in the CPI from year to year was dramatically different, as shown below.
40 U.S. Department Of Labor, Bureau of Labor Statistics.

Figure 15: The year to year percent change in the Consumer Price Index. Solving the traditional compound interest formula for the interest rate, we found that typical inflation is 3.29% per year. A graph comparing the value of $10 by 1914 standards can be seen below, comparing the actual inflation with this estimate of 3.29% per year.

Figure 16: The amount of money required to have the same value as $10 in 1914. By comparing the two graphs, we see that although it is very difficult to predict what the CPI will be in a given year, over long periods of time, such as the length of this solar panel investment, the average rate of 3.29% is a good estimation. By obtaining these parameters from historical data, measurements, or by professionals in the business, we have given ourselves the tools necessary to analyze the feasibility of different solar panel systems. The next section in this report, “Scenarios”, will use what we have outlined here to expand upon the feasibility details of certain photovoltaic systems.
7. Scenarios
To correctly assess the feasibility and impact this project would have on the church a number of practical scenarios were generated. These scenarios are analyzed using the economic spreadsheet in the economic context presented in chapter six. In each scenario, the system size is varied. In order to accommodate a larger system size, different installation procedures are necessary.
7.1 Assumptions and Selection of Solar Panels
The first objective in creating a list of practical scenarios was to determine the base assumptions. The summation of these assumptions is then factored into each scenario to build a base by which all scenarios can be assembled on. By taking this approach we limit the number of changing variables to more correctly display the affect that each scenario has on the outcome of the entire project. The assumptions listed below are values that extend those found in the Economic Context section. 100% Down Payment: After discussing with the financial representative at Wesley United Methodist Church we discovered the church holds no debt. Thus, there is no reason to take out a loan to pay for the system. The church representative assured us that if a system was purchased, it could be paid either through gifts or through a trust fund. Using Kyocera’s KC200GT Solar Panel:
One of the most critical choices in constructing a solar panel array is the choice of which solar panel to use. To choose the most practical panel available a list of potential solar panels was constructed and from that list the panel with the best credentials was taken. This list compounded several important factors, the most important of which were: energy production, cost-per-watt, and panel size. Based on
these factors, the recommended panel was Kyocera’s KC200GT. This panel embodied high energy production, 200 Watts, low cost-per-watt at $4.35, and relatively small footprint. 42 degree solar panel array tilt: Another critical factor in determining how much energy is realized by the solar panel array is the tilt of the panel relative to the sun. Throughout the year the sun’s position changes every month. For solar panels, the optimum tilt is the one that is perpendicular to the incident angle of the sunlight. However, for this system, the panels would not be mechanically tracking the sun, instead they are manually set. The conclusion to this problem was to tilt the panels at 42 degrees, the exact latitude of the Worcester area. This provides the best energy production for non moving arrays. Sunny Boy Inverters: For system sizes 25kW and less, the Sunny Boy line provides a very inexpensive inverter to match the output of a chosen array size. As discussed in Chapter 5, the Sunny Boy products are effective in price, efficiency, and reliability and fits quite nicely in the following scenario sizes. Using these inverters, we estimated a total DC to AC conversion factor of 79.49%. This factor was a result of the inverter efficiency as well as the efficiency of the AC and DC wiring and connections to the system. Combining the efficiency of the solar panels and the efficiency of the DC to AC conversion, we calculated an overall system efficiency of 11.92%.
7.2 Scenario 1: Small System Size:
First we investigated the smallest system available. This system, while humble in size, must still be capable of providing a moderate percentage (10%-15%) of power to the church. However, due to the church’s large energy usage, a small system might actually be considered large in other applications. For the “Small System” scenario we chose to implement a 10kW system.
Characteristics:
One of the most notable advantages to constructing a small solar panel system is the fact that it comes with a small capital cost. The initial system cost was calculated to be $49,000.00 after the appropriate rebates are applied. This system consisted of forty seven solar panels ($40,898.00) and two SB4000US DC-to-AC inverters ($5,370.00) with the installation accounting for the remaining cost. The entire system spanned 126.42 square meters and required very few, if any, elevated platforms. The greatest disadvantage of small solar array is the fact it provides such a small percentage of the total power consumed by the church. This solar array will produce less than one-sixth of the energy that the church is currently consuming and will take nineteen years to payback its initial cost. A system with such a long payback period is also susceptible to being quickly outdated by new and improved technology.
Impact:

Figure 17: 10kW System Energy Production
The chart above depicts the energy consumed by The Wesley United Methodist Church, seen in blue, and the electricity produced by the 10kW solar array, seen in red. The total “net” usage is seen in green which is the difference between the energy consumed and the energy produced.

Figure 18: 10kW System Cash Flow Figure 2 depicts the total cash flow of the 10kW array. The figure describes the trend of savings from the initial purchase in year one to the life expectency of a solar array, year 25.
7. 3 Scenario 2: Moderate System Size:
The second system we chose to investigate was a moderately-sized solar array. The goal of this system was to provide more electricity than the smaller apparatus while not drastically increasing cost. This system must be capable of providing approximately 20% of the churches electricity consumption. For the “Moderate System” scenario we chose to implement a 15kW system.
Characteristics:
The advantages to a 15kW system are that it produces much more electricity than its smaller system counter-part. In addition, the cost of constructing such a system is relatively inexpensive when
compared to the larger systems. To carry out such a system would require a total initial payment of $72,750.00 after rebates, consist of 70 solar panels ($60,900.00), two SB6000US inverters ($7,450.00) and installation costs. The system would be capable of producing slightly less than one quarter of the energy consumption of the church. With an increase in the number of solar panels on the roof of Wesley United Methodist Church, it becomes apparent that space is limited. A majority of the seventy solar panels, occupying 188.28 square meters, will need to be raised on an elevated platform to avoid shadowing affects. In addition to being space-limited, the “Moderate system” scenario will take nineteen years to pay off.
Impact:

Figure 19: 15kW System Energy Production The chart above depicts the energy consumed by The Wesley United Methodist Church, seen in blue, and the electricity produced by the 15kW solar array, seen in red. The total “net” usage is seen in green which is the difference between the energy consumed and the energy produced.

Figure 20: 15kW System Cash Flow Figure 4 depicts the total cash flow of the 15kW array. The figure describes the trend of savings from the initial purchase in year one to the life expectency of a solar array, year 25.
7.4 Scenario 3: Maximum System Size:
The third scenario maximized the number of solar panels that could be placed on roof. The energy produced by smaller systems is almost trivial compared to the total power consumption by the church. Thus, the goal of this system is to provide the most electricity possible using the maximum roof space available. For the “Maximum System” scenario we chose to implement a 25kW system.
Characteristics:
The greatest advantage of a large system is the large power output. A 25kW system is capable of producing more than one-fourth the church’s electricity, and, at various times, almost one third the total power consumption. Based on current costs, the maximum system size also has a payback period of nineteen years, the same as the modernly sized system found in the previous section: nineteen years. Although the system payback period is equivalent to the last three scenarios, this example produces a
much higher cash flow: averaging around $6,800 per year compared to $4,000 for the moderate system and $2,800 for the smallest system. The greatest disadvantage to this system is the cost to implement. Constructing a system of this size takes an initial $120,250.00 of capital investment, consisting of 117 solar panels ($101,790.00), three SB7000US inverters ($12,057.00) and installation costs. To fit 117 panels on the roof of the church requires elevating almost all of the panels and placing several of them on the slated section of the roof.
Impact:

Figure 21: 25kW System Energy Production The chart above depicts the energy consumed by The Wesley United Methodist Church, seen in blue, and the electricity produced by the 25kW solar array, seen in red. The total “net” usage is seen in green which is the difference between the energy consumed and the energy produced.

Figure 22: 25kW System Cash Flow Figure 6 depicts the total cash flow of the 25kW array. The figure describes the trend of savings from the initial purchase in year one to the life expectency of a solar array, year 25.
7.5 Scenario 4: Maximum System Size with Volunteer installation:
The final scenario produced assumed that the installation cost could be reduced by using volunteers to provide most of the necessary labor. Labor is the most significant cost involved in installing a solar panel array besides the cost of the system itself. The only requirement is that a licensed electrician supervises the electrical work.
Characteristics:
As stated in the section above, a solar system of this magnitude is capable of producing more than one fourth the energy consumption of the church. With volunteer work the system initial cost drops drastically from $120,250.00 to $41,057.00. The return on investment drops from nineteen years to only six! The disadvantage to implementing such a large system is the need for elevated platforms for
each panel. One hundred and seventeen solar panels require all the flat space on the roof including the slated area.