IEEE Std 1013-2019 pdf download

IEEE Std 1013-2019 pdf download.IEEE Recommended Practice for Sizing Lead-Acid Batteries for Stand-Alone Photovoltaic (PV) Systems.
4. Autonomy considerations
PV power systems may require some battery rcscrxc. both for reliability of service and to provide time for interveotlon in the event of an unanticipated occurrence, such as unusually poor weather or failure of a system cLmmnponeni. The miunther of days of autonomy is comnmnomily ceifted as a system design requirement and is based on scxcral considcra(ions. including the following:
ml System appikation. Critical load applications generally require more autonomy than non-critical applications.
b) Sixteja aindahllirr. System availability is the minimum percentage of the time that the PV system should be able to satist’ the system’s specified design loads.
C) Solar irrdiancr ssrriahditv. Daily and ea%onal vainaliuna in solar irrsdiasmcc affect the required autonomy.
dl P,rdiciabditv of load. The load may or may not be predictable: also, there may be the possibility of’ adjusting the loads, e.g.. dropping noncxscniial loads,
Cf Re-l,arge rapahilirw. If the array is insufficiently sized or if the available recharge time is tOo shun, then the battery may no be fully recharged between discharges.
I) Accessibility of ;ite. The worst-case time required for reashing the site and for correcting any problem should tic considered
5. Load determination
A description of the system’s electrical load, within the autonomy period, is itceded few the sizing of the battery. The validity of the battery sizing depends on the accuracy and completeness of this inlorinalion.
5.1 General considerations
The ovcnill duty cycle imposed on the battery is the description of the dc load current and its duration within the sutomimny period during which it is assunied that no power is pnividcd by the PV array. For ac loads supplied through an mx crier, these loads should be tabulated separately, totaled, and combined with the Inserter losses to detenninc the actual & load on the battery.
The system’s load can be espnssed in a tabular or graphical form, As both descrlptkmm. start with a tabulation of the individual loads and their durations, the tabular form is more general. The load-profile diagram, the graphical representation, is necessary to visualize the interrelationships of the individual loads. For both load descnpuons. all loads expected dunng a 24 h penod are tabulated along with their anticipated durations Worksheet I in Clause 9 pros idea a convenient method of tabulating load data in accordance with the sizing method of this recommended practice.
It may be necessary to consider a longer period of time when s24 h pcriod does not accurately describe the load profile. For those cases where the load profile ccccds 24 h. an average and a maximum daily load should be determined for subsequent battery capacity dctcrminatioiw. Worksheet 2 and Worksheet 3 in Clause 9 provide convenient methods for determining these loads, The average daily load is mcd in the initial determutation of the battery size.
Once the battery has been sized, the maximum daily load is used to determine the ability of this battery to sustain it. If thc maximum daily load sequence cannot be established, the days should be arranged in the worst possible order, generally with the maximum load day last. The battery’s capacity may need to be increased to satisfy the maximum daily load in this partially discharged state.
For applications where the load s’arics stgnificanlly on a monthly basis, the average daily load for cach month should be determined. The battery sizing should be based on the resulting maumum average daily
A load-profile diagram is a helpful aid in determining those areas where the battery’s performance needs to be checked to assure load satisfaction. To make a load profile diagram, do the following:
a) Tabulate all the individiul loads along with their starting and skipping times. hI Total the nincident loads for (heir respective petiods of time.
C) Plot the resulting total bed versus lime of day or elapscd time, as appropriate.
The reaullmg curve is the load-profik diagram If the daily loads vuy during the autonomy period, the individual daily load-profile diagrams, plotted in sequence. constitute the system’s load-profile diagram. Sec Annex B for esamplcs.
5.2 Load data
The systematic identification and characterization of the system’s individual loads arc fundamental to defining the battery’s duly cycle.
5.2.1 Momentary current
Loads lasting I mm or less arc designated “momentary” loads and arc given special consideratioii The anipere-hour requirements ol’ (his type of load are usually very low, hut their effcci on battery terminal soltagc may be considerable arid should he taken into account. Monseniary loads can OCCUr repeatedly during the duty cycle.