1、 中文 2344 字 The Basics of Solar Power for Producing Electricity Using solar power to produce electricity is not the same as using solar to produce heat. Solar thermal principles are applied to produce hot fluids or air. Photovoltaic principles are used to produce electricity. A solar panel is made of
2、 the natural element, silicon, which becomes charged electrically when subjected to sun light. Solar panels are directed at solar south in the northern hemisphere and solar north in the southern hemisphere (these are slightly different than magnetic compass north-south directions) at an angle dictat
3、ed by the geographic location and latitude of where they are to be installed. Typically, the angle of the solar array is set within a range of between site-latitude-plus 15 degrees and site-latitude-minus 15 degrees, depending on whether a slight winter or summer bias is desirable in the system. Man
4、y solar arrays are placed at an angle equal to the site latitude with no bias for seasonal periods. The intensity of the Suns radiation changes with the hour of the day, time of the year and weather conditions. To be able to make calculations in planning a system, the total amount of solar radiation
5、 energy is expressed in hours of full sunlight perm, or Peak Sun Hours. This term, Peak Sun Hours, represents the average amount of sun available per day throughout the year. It is presumed that at peak sun, 1000 W/m of power reaches the surface of the earth. One hour of full sun provides 1000 Wh pe
6、rm = 1 kWh/m - representing the solar energy received in one hour on a cloudless summer day on a one-square meter surface directed towards the sun. To put this in some other perspective, the United States Department of Energy indicates the amount of solar energy that hits the surface of the earth ev
7、ery +/- hour is greater than the total amount of energy that the entire human population requires in a year. Another perspective is that roughly 100 square miles of solar panels placed in the southwestern U.S. could power the country. The daily average of Peak Sun Hours, based on either full year st
8、atistics, or average worst month of the year statistics, for example, is used for calculation purposes in the design of the system. To see the average Peak Sun Hours for your area in the United States, U.S.-Solar Insolation Choose the area closest to your location for a good indication of your avera
9、ge Peak Sun Hours. For a view of global solar isolation values (peak sun-hours) use this link: Global Peak Sun-hour Maps , then, you can use back or previous on your browser to return right here if you want to. So it can be concluded that the power of a system varies, depending on the intended geogr
10、aphical location. Folks in the northeastern U.S. will need more solar panels in their system to produce the same overall power as those living in Arizona. We can advise you on this if you have any doubts about your area. The four primary components for producing electricity using solar power, which
11、provides common 120 volt AC power for daily use are: Solar panels, charge controller, battery and inverter. Solar panels charge the battery, and the charge regulator insures proper charging of the battery. The battery provides DC voltage to the inverter, and the inverter converts the DC voltage to n
12、ormal AC voltage. If 240 volts AC is needed, then either a transformer is added or two identical inverters are series-stacked to produce the 240 volts. The output of a solar panel is usually stated in watts, and the wattage is determined by multiplying the rated voltage by the rated amperage. The fo
13、rmula for wattage is VOLTS times AMPS equals WATTS. So for example, a 12 volt 60 watt solar panel measuring about 20 44 inches has a rated voltage of 17.1 and a rated 3.5 amperage. V A = W 17.1 volts times 3.5 amps equals 60 watts If an average of 6 hours of peak sun per day is available in an area,
14、 then the above solar panel can produce an average 360 watt hours of power per day； 60w times 6 hrs= 360 watt-hours. Since the intensity of sunlight contacting the solar panel varies throughout the day, we use the term peak sun hours as a method to smooth out the variations into a daily average. Ear
15、ly morning and late-in-the-day sunlight produces less power than the mid-day sun. Naturally, cloudy days will produce less power than bright sunny days as well. When planning a system your geographical area is rated in average peak sun hours per day based on yearly sun data. Average peak sun hours f
16、or various geographical areas is listed in the above section. Solar panels can be wired in series or in parallel to increase voltage or amperage respectively, and they can be wired both in series and in parallel to increase both volts and amps. Series wiring refers to connecting the positive termina
17、l of one panel to the negative terminal of another. The resulting outer positive and negative terminals will produce voltage the sum of the two panels, but the amperage stays the same as one panel. So two 12 volt/3.5 amp panels wired in series produces 24 volts at 3.5 amps. Four of these wired in se
18、ries would produce 48 volts at 3.5 amps. Parallel wiring refers to connecting positive terminals to positive terminals and negative to negative. The result is that voltage stays the same, but amperage becomes the sum of the number of panels. So two 12 volt/3.5 amp panels wired in parallel would prod
19、uce 12 volts at 7 amps. Four panels would produce 12 volts at 14 amps. A charge controller monitors the batterys state-of-charge to insure that when the battery needs charge-current it gets it, and also insures the battery isnt over-charged. Connecting a solar panel to a battery without a regulator
20、seriously risks damaging the battery and potentially causing a safety concern. Charge controllers (or often called charge regulator) are rated based on the amount of amperage they can process from a solar array. If a controller is rated at 20 amps it means that you can connect up to 20 amps of solar
21、 panel output current to this one controller. The most advanced charge controllers utilize a charging principal referred to as Pulse-Width-Modulation (PWM) - which insures the most efficient battery charging and extends the life of the battery. Even more advanced controllers also include Maximum Pow
22、er Point Tracking (MPPT) which maximizes the amount of current going into the battery from the solar array by lowering the panels output voltage, which increases the charging amps to the battery - because if a panel can produce 60 watts with 17.2 volts and 3.5 amps, then if the voltage is lowered to
23、 say 14 volts then the amperage increases to 4.28 (14v 4.28 amps = 60 watts) resulting in a 19% increase in charging amps for this example. Many charge controllers also offer Low Voltage Disconnect (LVD) and Battery Temperature Compensation (BTC) as an optional feature. The LVD feature permits conne
24、cting loads to the LVD terminals which are then voltage sensitive. If the battery voltage drops too far the loads are disconnected - preventing potential damage to both the battery and the loads. BTC adjusts the charge rate based on the temperature of the battery since batteries are sensitive to tem
25、perature variations above and below about 75F degrees. The Deep Cycle batteries used are designed to be discharged and then re-charged hundreds or thousands of times. These batteries are rated in Amp Hours (ah) - usually at 20 hours and 100 hours. Simply stated, amp hours refers to the amount of current - in amps - which can be supplied by the battery over the period of hours. For example,
