In addition to determining the overall feasibility of installing solar panels on the Wesley United Methodist church, a secondary goal of this project was to promote the awareness of solar panel systems the greater Worcester community. To achieve this, it was important to create a set of information that could be presented and distributed to the community. This final presentation included information
about solar panels in general, the steps required to determine their economic impact and get them installed, and reasons why solar panel systems are beneficial both economically and to the environment.
4. Site Analysis
This chapter is concerned with the physical conditions of the church and area around it that would affect the installation of a solar panel system. The nature of a solar array requires that the site analysis take into account the physical structure and layout of the roof space, as well as the weather. The weather plays an important role with such a system, determining the amount of sunlight that can be gathered by the panels and converted into energy. After a brief introduction to the location of the church, this chapter begins by discussing the meteorological findings for the area in which the church is located. The next section describes the physical layout of the roof space. This is followed by an analysis of the Church’s energy usage, and a look into the installation process.
4.1 Location of the Church
The Wesley United Methodist Church is located near the heart of Worcester Massachusetts. When traveling down Main Street the United Methodist Church becomes apparent as you approach the Johnson Tunnel, between State Street and Gertrude Ave. The church is located on 114 Main Street and resides at approximately 42.3 degrees latitude and -71.8 longitude. The building is four stories tall and formed primarily out of grey brickwork.
4.2 Meteorological Analysis
One of the greatest challenges in determining the feasibility of a solar project is determining the amount of energy that is provided by the sun. For solar panels, the primary factor of whether or not a project is feasible is the amount of sunlight a chosen area receives. To calculate this, many factors must be considered: average sunny days, clearness of the weather, precipitation, average sun duration, and latitude. To find how each of these factors effects the overall conclusion, tedious calculations must be done. Weather data from previous years need to be consolidated and then averages can be calculated
from this data. Fortunately, much of this information is readily available. The United States Renewable Resource Energy Data Center (RREDC) contains all the information needed to address these factors.32 One of the most useful ratings provided by the U.S Renewable Resource Data Center is the insolation graph. This graph displays the average solar energy per square meter per day in any given month. This value is calculated from thirty years of data gathering and is extremely useful when calculating the energy that can potentially be generated if solar panels are installed. From RREDC's website many different insolation graphs can be calculated. The website provides the user with three options. The first is what type of data to be displayed. This value can either be: average, minimum, or maximum. The second option is which month’s data to view. The user is given an option of choosing a specific month out of the twelve, or the annual reading, which provides an average. Finally, the third option specifies how the solar panels are to be orientated. Because Worcester is located at approximately 42 degrees latitude, the choice of orientation could drastically change the insolation values. For this project, the solar panels can be oriented southward at latitude. On the following page is a graph of the United States generated from RREDC's website which encompasses the average annual solar radiation for south facing panels. Each region on the map relates to a specific insolation value, where higher is better. In the case of Worcester, this area falls within the average of 3 to 5 kWh/m2/day.
32 RReDC. U.S. Solar Radiation Resource Maps. Renewable Resource Data Center. [Online] National Renewable Energy Laboratory. http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/
Expanding on the information above, the GAISMA organization also provides in-depth analysis of monthly insolation values. 33 By selecting the Worcester area, GAISMA provides a plethora of solar information from sunrise and sunset times, sun path diagrams, and solar energy and surface meteorology. While much of the information is enlightening, the most valuable statistic is the "insolation, kWh/m2/day" value found in the solar energy section. The GAISMA organization provides a very simple breakdown of insolation values for each month during the year. The difference between GAISMA's data and RREDC's is the fact that GAISMA provides a precise numerical value where RREDC only provides a range between two integers.
33 GAISMA. [Online] www.gaisma.com
Figure 9: Mean Daily Irradiation for Worcester
Using the data we have collected concerning insolation values, we are now capable of determining an approximate output of the panels. For example, when the project was in its infant stages, we estimated we had 270 square meters to work with. We then wanted to determine what the average energy was available to that given area. To calculate this we multiplied an insolation value of a specific month by the area available. The result is in kWh per day. Currently, the average efficiency of a solar panel is approximately 10%, so we multiplied our result by 10%. The result is an average amount of energy we could hope to acquire in a day if we covered the entire area with solar panels of an appropriate power rating. To determine what the average energy would be in a month we multiply this value by the number of days in the month. The result is a value that we can use to directly compare with electricity bill's consumption value sent monthly by the local energy provider. The benefit of determining this is that we can determine if the energy produced by that area is enough to meet, or exceed the church’s current consumption.
4.3 Layout of Roof Space
The primary roof space that would potentially be used for the solar panel array is a mostly flat area that is about 55 feet wide and 80 feet long. The area has an open southern exposure that makes it ideal for solar power collection. The flat part of the roof is situated in such a way that it is sunny with few shadows throughout the day, and anything mounted to the roof would not affect the aesthetics of the building from most angles, particularly Main Street in front of the building.
The flat roof area is covered with a white rubberized roofing material. In the center of the main open area are two large skylights (shaded black in the drawing), which take up space and cannot be removed or covered with panels. There is a third skylight mounted to the side of the north sloped roof. To the west side of the large open area is another section of sloped roof that rises above the flat roof about 20 feet. This creates a separate flat section that is primarily shaded by the sloped roof and the large chimney. On the east side is the sloped roof that runs parallel to Main street in front of the church and will completely block anything on the flat roof from view. The southern exposure is open to the side street next to the church building, but the height of the building blocks anything not on the edge of the roof from view. In the northwest corner is an elevated flat portion about 40 feet taller than the rest. This 20 foot by 40 foot section is almost entirely in the sun throughout the day and is covered in the same white rubberized material. It’s accessible by a ladder mounted to the wall, and is somewhat isolated from the rest of the roof area. This makes it somewhat less convenient to use. There is internal access to the main portion of the roof, making inspections, repairs and snow removal easier. This would also facilitate in monitoring the solar panels.
4.4 Energy Usage
Due to the church’s size and daily activities it is no surprise that the Wesley United Methodist church uses a significant amount of electricity. Currently the church uses an average amount of 9500 kWh of energy a month; which totals to $1300 dollars a month in electricity costs. It is apparent why the church has sought cheaper, renewable energy to offset electricity cost.
To correctly assess the impact of renewable energy sources, such as solar panels, we determined the church’s past and present electricity usage. The easiest method for determining the consumption trends from month to month is using past electricity bills. After consolidating electricity usage bills for one year in 2007 we created the graph below to help visualize the months of greatest
demand. This graph displays the amount of energy consumed, in kWh, from month to month. From the graph, it can be seen that although there are not huge fluctuations in the amount of energy needed by the church, certain months, such as August and December, have higher energy demands. This may be due to factors such as air conditioning in the summer, and the increased need for lighting along with holiday activities in December.
Figure 10: Wesley United Methodist Church’s Electricity Consumption Using the meteorological data from section 4.2, we compared the energy consumption data of the church to the amount of energy that could be produced by a solar panel system. Although in chapter 7 we discuss a number of scenarios corresponding to various system sizes, the graph below demonstrates a system size of twenty kW. The blue bars in the graph represent the monthly energy demands of the church, as in the previous graph. The red bars represent the amount of energy that can be produced by a 20kW system. The difference between these two, which corresponds to the net energy demand after installing such a system, is displayed in green.
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Figure 11: Power Consumption vs. Energy Production of a 20 kW System From this graph, it can be seen that the system displayed does not produce enough electricity to fully offset the demands of the church. Because of the very large energy demand required by the church, coupled with the amount of irradiation in the Worcester area, it would take system that is larger than could be supported by the available roof space. So although it is unlikely that the church will be able to sell any excess energy back to the utility company, the amount produced could defer a considerable fraction of their overall energy demands.
4.5 The Installation Process
Because the church has a newly installed membrane roof on its flat areas, installation on this portion of the roof should be relatively simple. The mounting structure for the panels can be directly connected to the roof and sealed to maintain insulation. These portions of the roof are rated for 35 lbs per square foot, which should not be exceeded.
The slanted portions of the roof, however, are covered in slate. If any solar panels were to be put on this area of the roof, we would recommend removing the slate tiles on these portions. This is because the fragility of slate requires that it be given higher level of maintenance. For example, cracked tile may need to be replaced. If solar panels were mounted on a slate portion of the roof that needed to be repaired, significant work would need to be done in order to fix the underlying slate. Also, the installation procedure for mounting panels on a slate roof is more complex, and the tilt angle of the panels is restricted to the slope of the roof.
It is important that during the installation process all necessary electrical and building codes are adhered to. Certain requirements are also stated by Commonwealth Solar in their minimum technical requirements.34 These include the use of a Massachusetts licensed electrician to do all of the electrical work, making sure all wiring modifications are properly insulated, and that the system can be disconnected for maintenance. Another aspect of the installation process is tying the solar panel system into the electric grid. This allows the excess electricity produced by the system to flow into the local electrical grid to be used by other members of the grid. This process begins by completing an interconnection agreement with the local utility company. The utility company reviews the project to make sure that it will have no negative impacts on the grid. The utility company, town and local inspectors, and the contractor installing the system are all involved in this process. It is best to begin the interconnection process during the final design stages of the system, but before construction, due to the level of technical detail needed by the utility company in order to assess the installation’s possible effects.
34 Massachusetts Technology Collaborative. Commonwealth Solar Rebate Program. Retrieved 1/15, 2009, from http://www.masstech.org/SOLAR/CS_AttachmentDMinimumTechnicalRequirements_v3_010109.pdf
In order to give the church the information necessary to pursue an installation if they found it to be feasible, we created a list of installers who would be able to install such a system. This list can be seen in Appendix
spreadsheet of Massachusetts solar panel installers provided by Commonwealth Solar.35 Installers were then selected based on the costs of their installations, the size and scope of previous installations, and reviews and recommendations gathered from our various correspondences.
35 Massachusetts Technology Collaborative. Information on Installers and Costs. Retrieved 1/15, 2009, from http://www.masstech.org/SOLAR/CS%20Installer-Cost-Location%20Data%20for%20Website%20as%20of%2001-31-09.xls
5. Possible Solar Panels and Inverters
One of the most important factors in devising a photovoltaic array is determining which solar panels to purchase and what type of inverter to utilize for the situation at hand. To correctly assess which panels and which inverters would make greatest impact on our feasibility solution for the Wesley United Methodist Church a component matrix was conceived. The component matrix contains pertinent information about potential photovoltaic/inverter candidates that have a high chance of success in our solution. The matrix incorporates many of the highest quality products made by various manufactures in the field of solar technology. By consolidating these potential products we are capable of determining which panels or which inverters have benefits over their competitors and how those benefits will affect our goal of feasibility. This chapter is separated in two distinct sections: solar panel choices, and inverter choices. Each section will discuss the criteria used to filter out unwanted components as well as which devices hold the greatest chance of success.
5.1 Solar panels
At first glance, the amount of solar panels available is overwhelming. To overcome this, a set of benchmarks was established and each panel was ranked against the set of criteria. If a given panel ranked poorly it was discarded. Any panel that was moderate or exceptional was added to the matrix of possible panels to be later scrutinized when all variables had been considered. The criteria were comprised of these important attributes: power output, efficiency, size, and weight.
Many selection criteria were initially established out of back of the envelope calculations and later altered when additional variables were realized. Judging by the electrical consumption of the Wesley United Methodist Church as well as the limited amount of space available for solar cells, we concluded that our solar panels must have a power output of at least 175 Watts. Panels that are equal
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