PV system design
Before making the PV system design, the need to understand and get some calculation and select the required basic data: PV system on-site location, including location, latitude, longitude and altitude; meteorological data in the region, including the monthly total solar radiation, direct radiation and scattered radiation, and the highest annual average temperature, low temperature, the longest consecutive rainy days, maximum wind and hail, snow and other special circumstances such as weather. Battery capacity battery design includes the design of series and parallel computing and battery pack design. First, the basic method of calculating the battery capacity is given.
1. The basic formula
I. The first step
The load required daily consumption multiplied by the number of self-sufficiency based on the actual situation of days you can get a preliminary determination of the battery capacity.
II. The second step
The battery capacity obtained in the first step divided by the maximum allowable depth of discharge of the battery. Because they can not let the battery is fully discharged in a few days in the self-sufficiency, it is divided by the maximum depth of discharge, to give the desired battery capacity. Select the maximum depth of discharge need to refer to the use of photovoltaic systems in the selection of battery performance parameters, you can get detailed information about the maximum depth of discharge of the battery from the battery supplier. Under normal circumstances, if you are using deep cycle type battery recommended 80% depth of discharge (DOD); If you are using a shallow cycle batteries, recommended use use 50% DOD.
The basic design of the battery capacity formula below:
Battery capacity = (X number of days the average daily subsistence load) / maximum depth of discharge
These of course are not corrected, the following is the correct formula:
BC battery capacity is calculated as: BC = A × QL × NL × TO / CCAh A safety factor, take 1.1 to 1.4
QL is the load average daily consumption, multiplied by the daily working hours for working current; NL for the longest consecutive rainy days;
TO is the temperature correction factor, generally above 0 ℃ to take more than 1, -10 ℃ to take 1.1, below -10 ℃ take 1.2; CC for the battery depth of discharge, lead-acid batteries typically 0.75, 0.85 alkaline nickel-cadmium batteries.
The following describes the method for determining battery strings in parallel. Each battery has its nominal voltage. In order to achieve the nominal voltage of the load of work, we will supply batteries connected in series to the load, the number of batteries needed in series equal to the nominal voltage of the load divided by the nominal voltage of the battery.
Serial number of the battery load = nominal voltage / battery nominal voltage
The basic method of calculating the energy of solar modules (ampere hours --AH) with energy (ampere hours --AH) load divided by the average daily need of a solar cell module that can be produced in one day, so you can calculate the number of solar cell modules in parallel system needs, the use of these components can be produced in parallel current system load required. The nominal voltage of the system divided by the nominal voltage of the solar cell module, the solar cell can be obtained a solar cell module required number of components connected in series, using these solar cell modules in series can produce the required voltage system load.