EE8744 Homework 1 Solution

Problem 1. [5 points] Gallium Arsenide has a band gap of 1.42 eV. What maximum wavelength can a photon have to create electron-hole pairs?
Problem 2. [20 points] Let us explore the design of a PV system for Las Vegas, NV to deliver 4000 kWhr/yr. Las Vegas is known to receive 6.4 kWhr/m2day of average annual insolation and it has an average ambient temperature of 26.9◦C. Answer the following questions:
1. What should the AC rated power of the system be?
3. If the PV modules are 13% efficient, what is the required area for the system?
4. Suppose the installed cost of the system is $6 per DC Watt, and the system is paid for with a30-year loan at 6% interest rate. Las Vegas offers a renewable energy credit that pays the owner $0.05/kWhr generated. What is the cost of electricity generated in year 1?
Problem 3. [8 points] The figure below shows the I − V curves for two cells. Answer the following questions:
1. Estimate Rs for the cell with I − V curve labelled as Rs =?
2. Estimate Rp for the cell with I − V curve labelled as Rs = 0.
3. Estimate the maximum power that can be delivered by the cell with I − V curve labelled as Rs = 0.
4. Consider the cell with I − V curve labelled as Rs = 0. Sketch the I − V curve that would be obtained by connecting 5 parallel strings each with 10 series-connected cells of this type.

Problem 4. [2 points] We wish to deliver maximum power to a 12 V battery from a PV resource with the following characteristics: Open-circuit voltage 41 V, short-circuit current 6 A, maximum-power point voltage 40 V, and maximum-power point current 5 A. Pick a DC-DC converter topology to accomplish this and indicate the duty cycle at which the converter would have to be operated for the task.
Problem 5. [5 points] A grid-connected PV array consists of sixteen Shell SP150 modules that can be arranged in a number of series (S) and parallel (P) configurations: (16 S, 1 P), (8 S, 2 P), (4 S,
1


4 P), (2 S, 8 P), (1S, 16 P). The array delivers power to a Sunny Boy SB2500 inverter. Using the specifications of the PV modules in Table 1 (a), and the specifications of the inverter in Table 1 (b), what series-parallel configuration of modules would deliver maximum power to the inverter? Circle the right answer and provide an explanation for your choice:
1. (16 S, 1 P)
2. (8 S, 2 P)
3. (4 S, 4 P)
4. (2 S, 8 P)
5. (1S, 16 P)
6. None of the above.
[Note. To clarify the notation, (2 S, 8 P) corresponds to the case that the array is built with 8 parallel strings and each string has 2 modules connected in series.]
2