Wind & Sun supplied and advised on a domestic grid connected PV system installed by the house owner.
The PV System
The 1.02kWp Photovolaic Array consists of 12 BP Solar 585F monocrystalline PV modules connected in series to give ~216 VDC output. The Saturn cells used are the most efficient commercially available, and most cost effective, giving maximum kWh energy production for a given area. . The PV array is cabled in to the house and connected to a SMA Sunny Boy grid connected inverter. PV system design was by Wind & Sun.
PV system installation was carried out by the owner, Tony Skelton. We had 12 stainless steel brackets made to hold the PV's. The two-pole DC disconnect and lockable AC isolation switch and the BP inverter were installed in the garage. A separate fuse board was installed for the system, and connected to the house distribution board that was just above it.
A DC disconnect switch was fitted to isolate the high voltage from the solar panels, and an AC disconnect switch was fitted to isolate the mains grid. As an extra a modem was fitted to the inverter to transmit system data to a display in the house, via the existing mains cable.
To make the cabling easy and neat, trunking and plastic tubing was used. Once the cables were in the roof, the owner installed a large junction box to terminate all incoming cables from the panels on the roof. All the cables from the panels were wired in series in this box.
A Sunny Boy control unit was installed in the house so the owner can see what is going on with the system at any time. It shows live information about wattage, total energy day by day, system status, voltage of the PV array, grid voltage, grid frequency, and resistance between power lines and earth. It is also the user interface for the inverter. Almost everything you might need to know regarding the performance of the system can be measured, displayed, or recorded with the Sunny Boy.
The owner felt that the most useful of these is probably "daily energy". This shows each days Kwh production for the last year. From this, spreadsheets or graphs can be generated, which clearly show any unusual days or possible problems. The information on the display is transmitted across the mains cabling at high frequency. By simply plugging the display into any mains outlet, you can see what is going on. There is a data port on the diplay panel that allows connection to a PC, so it is possible to print out data and graphs for any day or month. The annual average energy production for a system like this is about 850 Kwh.