problem 1: A solar thermal salesman heard about the Rusk’s solar PV system and decided to convince them to use part of their roof for solar thermal instead of solar PV.
a) If the thermal solar collectors are 70% efficient and the aperture area is 70% of the area covered by the solar thermal collector system, how many kWhs of energy per square meter is recovered assuming 5.5 kWh/m2/day? How many BTU’s?
b) The tap water comes into the house at 60 oF and is heated by the thermal solarsystem. How many gallons of this water can be heated to 130 oF per day per square meter of solar thermal system?
problem 3: The solar PV company comes back with a quote for the purchase and financing of the solar PV system. The total system with installation will cost $54,000.
a) The federal government gives them a 30% tax rebate. Assuming an interest rate of 7.5% for 15 years, what will be their monthly payment for the installed system?
b) Using the data described below (that is, use the average cost per year averaged over both years), what is the payback period for their system?
problem 4: A 20-kW CHP system has an electrical efficiency of 40% and a thermal efficiency of40%. Its $45,000 cost is paid for with an 7.5%, twenty-year loan having annual paymentsof $4386/year. Its heat output displaces gas costing $10 per million Btu that would havebeen burned in an existing 85%-efficient boiler. If the CHP system has a capacity factor(CF) of 0.90 (in essence it runs only 90% of the time during which it delivers the full 20 kW), find its cost of electricity.