Case Study

A clothing manufacturer in Central Java, Indonesia, had considered to go solar. Like most manufacturers, it was facing large electricity costs which had been increasing every year. Therefore, going solar was a smart option. However, the manager did not know where to start. Hence, he had three questions in mind.

  1. “Is my location good for solar?”

  2. “How will my system perform?”

  3. “What is my profit?”

To address these questions, the company needed a detailed case study. In this article, we introduce a short version of our study.

1. Site Assessment

First, we wanted to decide whether the location is good for solar. For this purpose, we focused in three major issues: roof space, sun radiation, and roof angle.

Sun radiation. The factory is located in Central Java, Indonesia (7°S, 110°E.) Therefore, we used our database to determine how the sun behaves in the location. (See Exhibit 2.) From the data, we could gain two insights:

  • Strong sun radiation at the site. Over a year, the total sun irradiation is 5.2 kWh/m² day on average. This number is large given that the site is located near the equator.

  • Higher level of cloud cover around March. Sun is vertically above the equator in March and September. Hence, the sunlight should be the strongest near these months. However, we saw how the sun is weaker than expected in March (compared to September.)

Roof conditions. First, we determined how much power the roof area could produce. For this purpose, we ran a calculation procedure. (See Exhibit 3.) As a result, we found out that the roof could support up to 480 solar panels, or 134,400 Wp (watts peak.)

Next, we moved on to analyze how the site’s roof angle affects the capture of solar radiation. The solar panels would be installed on the factory’s roof (10° facing North and 10° facing South.) For this purpose, we entered the data from Exhibit 2 into our simulation. (See Exhibit 4.) In conclusion, we found out that the factory’s roof is excellent for a solar installation (with 0% loss on its North facing roof and 5% loss on its South facing roof.)

2. Engineering Design

Circuit design. After the preliminary site assessment, we proceeded to design the circuit. We decided to install two sub-arrays, each with 240 solar panels. (See Exhibit 5.)

Energy production. We tested the circuit design in our simulation. First, we studied how much energy would be wasted as losses. We found out that our system would lose about 16% of its energy due to tilt angle, soiling, irradiance, heat, wiring, etc. (See Exhibit 6.) We forecast annual energy production of 214 MWh/year. After that, we further broke this number into monthly values for a more complete analysis. (See Exhibit 7.)

3. Economics Analysis

Costs. Next, we calculated each component of the system costs. The majority of the costs are solar panels (39%), engineering and installation (16%), mounting (15%), and inverters (11%.) (See Exhibit 8.)

Investment return. Finally, we proceeded to assess the profitability of the project. The investment will allow the consumer to cut electricity bills. This becomes continuous returns on investment. In our economics simulation, we assumed a 214 MWh/year energy production, an output degradation of 0.7%/year, and electricity price growth of 10%/year. We forecast a break-even point of 7 years and a combined lifetime cost savings of $1.8 million after a $0.2 million investment. Therefore, we concluded that the project is profitable. (See Exhibit 9.)

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