Project design > User's needs ("load")

The programme offers great flexibility to define the needs of the user (or the "load" of the system). You can choose among the following options:

- Unlimited load, which only concerns installations connected to a sufficiently "strong" grid to absorb all the power produced. This is the default option with grid systems. But this option obviously makes no sense with a stand-alone installation, where production and especially battery behaviour are closely related to electricity use.

- Fixed constant load, offers the simplest way to define user's needs. You just have to define it as constant power or yearly energy.

- Monthly values gives the possibility of defining monthly averages, which will be used by the simulation as constant over each month (no daily modulation). Values are defined using a special graphic tool.

- Daily profiles in hourly values can be user-defined using a graphic tool, as:

Constant over the year: the same profile all along the year,

Seasonal modulation: four specific daily profiles, for each season (defined as June-August, September-November, December-February, March-May).

Monthly normalisations: one only daily profile, the amplitude of which being modulated according to given monthly sum values.

Weekly modulation: a specific daily profile for "working days", and another one for "week-ends". Each of these staying constant over the year. The number of "Working days" in a week is user defined.

- Probability profiles are designed for grid applications, when the grid load is not illimited. It is the probability distribution of the power which can be absorbed by the load at a given instant. This is especially suited to DC-grid for public transports. Possible power load is divided into 12 classes of given values; the user specifies the probability distribution values for each hour. This profile can be defined:

Constant over the year: the same profile all along the year,

Seasonal modulation: one specific daily profile for each season (as above).

Weekly modulation: a specific daily profile for "working days", and another one for "week-ends".

- Daily Household consumers is the default user's needs definition for stand-alone systems. It proposes a list of most usual domestic appliances, with unit power and daily use duration. Values can be defined as:

Constant over the year: the same daily load value all along the year,

Seasonal modulation: one specific daily load for each season.

Monthly definitions: a specific appliance distribution for each month.

NB:	With this tool a Weekly modulation option is independently available for each season or month, but only for putting some "week-end" days to zero or standby.

This appliance's definition is mainly thought as a presizing tool for stand-alone systems, in order to evaluate the load from a user's point of view. In presizing, the effective use of the defined values, during the simulation process, is equivalent either to a constant load, or to seasonally or monthly constant values. In detailed simulation, a superimposed daily profile may be defined.

- Load values read on ASCII file is the most flexible load definition: you can edit your own desired load profile (either in hourly or in daily values) in a spreadsheet editor or any ASCII file, and easily import it in PVsyst.

NB: You can save your Load profile as a model for reusing it in another project.