Queenstown Residence

21.6kW Solution

A secluded house in the Queenstown district features one of the largest Photovoltaic (PV) installations in New Zealand. The system is rated at an impressive 21.6kW with the install split between the roof of the house and a ground-mount system.

After extensively investigating all the available PV Panel brands available, the owners of this residence chose Mitsubishi Electric.

Mitsubishi Electric PV panels are manufactured to provide high efficiency. The higher the efficiency of each panel the more power produced, ultimately reducing the number of panels required for installation. The amount of power required from a PV array will dictate the overall size of the installation in terms of the number of panels required. This particular project combines 120 PV panels; therefore some consideration was given to how they would be fitted to the residence.

If you are considering an investment in your own PV power system, you want an assurance you are getting what you pay for. Mitsubishi Electric backs the quality of their brand with a power tolerance of +/- 3% meaning you get the wattage you pay for (in fact, often exceeded). This rating output is also back by a 25-year performance warranty, an assurance that not only gives confidence to our installers but also reflects Mitsubishi Electric’s guarantee that the product will maintain its output performance over many years.

As this residence is located in an area where power cuts can be both frequent and sometimes lengthy, the owner was keen to explore alternative power options for his new home.

The options for alternative energy generation are typically to install either an Off-grid or On-grid system.

An Off-grid system is one which is isolated and not connected to any external electricity provider. These systems are designed to produce enough energy to power your entire house, with any excess power stored in batteries which at peak times (or during very cold periods) can be powered by a diesel generator. Given that this type of system sits apart from traditional electricity supply, it would normally include more than one renewable energy source to ensure the power production is maintained (i.e. PV and Wind, or PV and Hydro solutions).

An On-grid system is a much simpler proposition, as the size of the alternative power system can be sized to suit your needs to offset some of your household’s overall electricity costs. An On-grid system is comprised of PV panels which are installed to provide a portion of your overall power usage which is fed back to the grid during off-peak times (i.e. during the day or periods of low demand), meaning the grid itself effectively becomes your storage. At night time, or other periods of peak demand, the power used by your household is offset by the “credit” your PV system produced during the day.

Both Options have Positives

The Off-grid system means no power bills – ever! No reliance of other power providers – ever! For this particular customer, an Off-grid system was not ideal due to the power consumption of the home. The number of batteries required to store the energy produced was not sufficient to provide unlimited power to the home, meaning any usage over and above the power stored would require the diesel generator.

The On-grid system means reduced power bills and the reassurance of knowing that the power grid is always available if required, without reliance on a generator. One of the biggest assumptions made when installing an On-grid system is that if the area has a power cut you can use the power your PV system is producing. Unfortunately, this is not true. During black-outs, the power produced by your On-grid system must also be isolated. This is done to ensure that any linesman or power line worker making repairs to the lines are not at risk of electrocution from the power your system is producing.

The installation for this residence combined both of the systems described above. This combination is known as a Back-Up System and is more commonly installed in commercial applications, such as telecommunications buildings, where back-up power is essential to continue business operations in the event of a power failure.

System Design

This system is installed on a large domestic home on the outskirts of Queenstown. The PV installation is split between the roof of the house and a ground mount system. The PV inverters are installed per phase consisting of 40 x 180w panels to each inverter.

System rated at 21.6kW and includes 120 x Mitsubishi Electric 180w Modules

This is an On-Grid system, but as the client wanted power available to the residence even during power cuts, a Back-Up system was also installed.