The photovoltaic array of a solar-powered calculator measures 20 mm by 20 mm and its efficiency in room lighting is 8%. what is the minimum light intensity, in watts per square meter, in which it will maintain a power output of three-tenth of a milliwatt? 3. a household in champaign il uses 15,000 kwh of electricity in a year. estimate what area of solar panels would be required to produce 15,000 kwh of electricity. what is the required installed capacity (kw)? what is the estimated cost of this solar pv project? (the insolation is 800 kwh m-2 yr-1 ). 4. a pv cell has an active area of 250 mm by 160 mm and operates with an average conversion efficiency of 20%. a. using an annual solar radiation data of 1068 kwh/m2 , estimate the electrical energy, in kwh, that could be provided by the above cell. b. calculate the number of such cells required to supply the 2,000 kwh per year of electricity needed by a small, energy-efficient household for lighting and electrical appliances? what would be the total active area? c. what is the most obvious drawback of this form of electricity supply, as described?