Buildings today are increasingly integrating renewable photovoltaic energy sources to supply power for the building loads. For those designing such an electrical installation, the integration of photovoltaic sources can be a challenge. This is especially true for existing buildings where, in addition to the power demand and the PV-produced power, constraints due to the existing electrical infrastructure must be considered.
Indeed, a photovoltaic system can be connected to the building electrical installation at different places: to the main low-voltage (LV) switchboard, to a secondary LV switchboard, or upstream from the main LV switchboard. These options, their advantages and drawbacks are discussed in this blog post.
1. Recommended design: connect to the main LV switchboard
One option is to connect the photovoltaic system to the main low-voltage switchboard of the electrical installation. If the conversion of the power produced by the solar panels is done by more than one photovoltaic inverter, it is recommended that the output of those inverters be grouped by connecting them to a secondary LV switchboard, which is then connected to the main LV switchboard at a single point.
This architecture is simple and safe to maintain because the photovoltaic production can be disconnected at a single point. It is recommended for both new and existing buildings.
2. For existing buildings with small-scale PV production
Connecting PV generators to the closest secondary low-voltage switchboard is an architecture used mainly in existing buildings where the PV production is much lower than the building consumption. This approach is used primarily in existing multi-floor buildings, where the PV production, usually on the roof, is far from the main LV switchboard, which is usually at ground level. Indeed, in such situations, the cable length between the PV system and the main LV Switchboard can be considerable. Connecting the photovoltaic system to a secondary LV switchboard nearby can minimize cable length and facilitate integration of the photovoltaic system.
However, this architecture presents important limitations including
- Complexity of the design, management, and maintenance of the installation, especially if there are several dispersed PV-sources
- Limited upgradability, because an increase in the PV system production capacity or the addition of other local production or storage may require significant changes such as resizing the existing electrical infrastructure
3. For existing buildings with PV production exceeding the demand
Connecting the PV system upstream from the main low-voltage switchboard is frequently the approach taken in existing buildings when the PV production being added is greater than the building’s consumption. In this case, connecting the PV system to a secondary or main switchboard would overload the existing electrical infrastructure and would require its modification, such as replacement of cables, switchboards, and protection equipment. Making the connection upstream from the main switchboard provides a better option because it does not require any modifications of the main LV switchboard or other system components downstream from the installation.
You can discover a detailed design for each of these architectures, as well as concrete project examples, in this video, which is part of larger video series on design of installations with photovoltaic production.
An additional resource
To simplify the integration of a photovoltaic system and/or other distributed energy resources, consider Schneider Electric’s Energy Control Center – an intelligent, pre-engineered, and configurable power control center designed to easily optimize resources and maximize facility performance.