Mercury is one of the largest energy companies in New Zealand. They are committed to a sustainable New Zealand, with 100% of their generation coming from renewable sources. They are also carbon positive, meaning they offset more emissions through their forestry partnership than they produce.

Mercury have completed many successful solar installations around New Zealand and the Pacific over the years, and have an award winning solar R&D centre in Auckland. This gives them a good depth of practical and expert knowledge of solar generation solutions.

For Rengaru Village their engineers have designed a 11.52kWp (36x320W panels) solar system combined with 27.6kWh of storage for each home. This is a robust design able to generate an excess of power sufficient to contribute towards charging an EV in the sunnier months and a rapid battery recharge in winter months. Average generation around 48kWh with a much higher peak output.

During the day, the sun first supplies power to the home to meet any need and then recharges the battery for evening use. Excess energy heats the hot water during the day and lastly, charges the car. Water is heated by a specialised heat pump driven by the electricity generated by the panels.

Because a passive solar design reduces the energy required to a third of the usual running household costs, solar can then realistically supply the energy required to run a modern household. This is combined with sensible cost saving measures such as low energy fridges, lighting and other electronics.

Depending on the build specifications either none or very little boost heating is required. For example, the fully certified e haus build requires only the body heat of the occupants to stay toasty or cool. A de-rated build in a warmer climate may choose to have a compact wood burner and wet back to cover winter cloudy days to allow water heating to go offline to service other needs.

Gas hob cooking is another back up system for prolonged winter cloudy days.

A generator is available as a final fall back in mid-winter and is recommended as a back up to meet any eventuality. However, with this package and the application of the above strategies they would seldom if ever be used.

Folks who live off grid often say, “Living off grid makes you feel really connected with your environment, which gives you a great sense of well-being” as well as having very low outgoings and no electricity utility bills. 

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There is no mains power to the solar village, and it is expected that all residents will install their own independent power system, most likely based on solar generation. On the demonstration house that we have built, power is supplied by an off grid system using the Mercury Energy solar package. This consists of 10.5KW of  photovoltaic (PV) panels, 36KWH of lithium ion storage and all the necessary control equipment. We deliberately installed an ‘oversupply‘ of generation, as PV panels are the cheaper part of the system and so it is designed to continue to provide sufficient power for rapid storage recovery during solar minimum in mid-winter, and to charge vehicles.

When combined with passive solar house design and construction, plus energy efficient appliances, this type of system can easily provide enough power for modern living. It is capable of generating up to 27KW per day, which matches the average daily consumption of energy inefficient homes of around 27KWH. So if you reduce your consumption to one third using energy efficiency measures & appliances, as suggested by the ECCA, then you can generate excess power for most of the year that can be used for your electric vehicles.

An annual maintenance plan and Wifi monitoring are also available from Mercury Energy at low cost.

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