The Summer Cottage WorkSheet |
Appliance Type | AC | DC | Rated Wattage/Hr | Hours on | Hrs used per day AC | Hrs used per day DC |
6 low watt bulbs | yes | 13 | 4 | 312W | ||
stereo | yes | 50 | 2 | 100W | ||
brew coffee maker | yes | 1200 | 10/60min | 200w | ||
toaster | yes | 1200 | 1 cycle | 150W | ||
Ceiling Fan | yes | 75 | 3 | 225W | ||
20" colour tv | yes | 100W | 2hrs | 200W | ||
Satellite dish/receiver | yes | 25 | 2 | 50W | ||
cordless phone | yes | 3.6 | 24 | 86W | ||
Mac Laptop | yes | 85w | 3 | 255w | ||
microwave | yes | 900w | 1 | 900W | ||
Refrigerator | yes | 150w/cycle | 24 | 1200W | ||
CD/DVD | yes | 25W | 3 | 75W | ||
Total | 3753W/day |
Calculating Your PV size: We will assume that you live in Canada in Southern Ontario and that you wish to setup in Cottage country in the Muskoka area. If you check the map of peak sun hours you will find that it is 4.4hrs/day during the spring summer season. For your specific area, please check the USA Natural resources sites or if you are in Canada please click on the "map of peak sun hours" link. To calculate the PV size in the above example. 3753 Watt-hours/day ÷ 4.4 sun hours/day = 853 W PV Panels We must derate the manufacturers ratings (by assuming a 20% derating factor): 853 Watt real power rating ÷ 0.77 reality factor = 1108 Watts/Hrs/day Manufacture rating There are two ways of looking at this power rating:
Batteries are an essential part of this PV system on non-grid connected systems. If you are Grid-tied or Grid-interconnected, batteries are an option and not essential unless you want battery backup power for when there is a power interruption. For this summer cottage, the power generated needs to be stored in batteries for later use. Here is how to determine your battery backup: To determine the voltage you will need in batteries; use the following guideline. A seasonal cottage with four occupants, refrigeration and limited water pumping. A 500 watt peak PV array should do fine. This would be a 12V system wired both for DC and AC depending on the load. A Full-time cottage or residence, including low power television, stereo, highly efficient EnergyStar compliant clothes washer and refrigerator, will require a 800 to 1000Watt PV array, wired for 24 Volts. During the Winter "dark months" an backup generator would be required. You can counter that with more PV panels. Below 7000Watts per day, a 24Volt system would work fine. This would suit a family of four. A daily energy consumption above 7000 Watts per day, a 48 Volt PV system will be required. A full-time residence using a dishwasher, clothes dryer (gas powered), central vacuum, washing machine and electric refrigeration would require a PV array of 2000Watts or higher depending on the load. Probably a backup generator would be needed for the dark winter months. Estimating the Required Battery Capacity (amp/hours)
Nominal Voltage of battery: (choose 12, 24, 48) _______ VDC Decide the number of days of battery storage you need. (Rule of thumb is two days for a hybrid system and three days for an non-grid connected system) _______ days
Battery capacity in (amp hours):
Total daily Load (Whrs/d) X (days of Storage) ÷ {Battery Voltage (VDC) X 0.42} =1108Wh/d x 3 ÷ (24VDC x 0.42) =3324 ÷ 10.08 =330 Ah The factor 0.42 assumes an 85 percent Battery effeciency and a 50 percent maximum depth of charge. For colder climates a higher battery capacity in Ah will be required. Increase the battery capacity by 30% for temperatures of (-20 C or -4 F) 429 Ah for colder climates.
|