With no centralised water supply, water is of prime concern on Great Barrier Island. A failure of storage can easily become a household catastrophe with no tankers to replenish a potable water supply. Summers are dry with periodic weather events that many households rely on to fill tanks, and in winter there can be long bouts of rain and the occasional flood. This all poses a particular set of problems to the Island with 65% of households using rainwater harvesting as their prime source of water. The simple act of not checking your gutters and downpipes, or leaving a tap on overnight, can mean suddenly finding a water tank empty only a few days after heavy rain.
The near 20% who harvest water from the streams fare little better with flooding and drought sometimes leading to washed out water lines or air blockages. Even with a filter stream water will taste slightly like clay for a few days after a heavy rain and those that reply purely on stream water for their needs can find themselves with no potable water after an extreme event such as the extreme weather event in 2014 proved.
Spring and bore bore water fare better in extreme events but relatively few of the Islands households are supplied by them. A common theme in water harvesting on the Island, and in fact a common theme in many activities on the Island, is the use of multiple water resources to ensure and adequate supply.
Hot water is primarily obtained through the use of califonts, solar water heating, and wetbacks. There are some gas heated hot water cylinders, but not many as califonts are a more efficient use of gas. Wetbacks have been the mainstay of the Island for many years but they are gradually being replaced by califonts and solar water heaters. In the future hot water heat pumps may also be a good option for heating water.
Heat pump water heating (HPWH) is a highly efficient option for medium to high water users. While not financially recommended for low hot water users, (1 -3 person families) it is a strong option for 4 person and up off grid families and commercial applications. HPWH systems work very well with solar PV as they deliver up to 4 units of energy for every 1 unit used. A typical All-in-One system only draws 700w when working and fully charges the storage tank in a few hours during the day when solar provides the power thus providing a highly effective energy storage ‘battery’ solution delivering abundant and cost effective hot water.
A typical integrated system of solar PV, battery storage and HPWH for a family of 4 would include a 3kWp solar system (about 12 panels), an All-in-One 170L HPWH and a battery bank of approximately 1240Ah capacity.
Last updated on the 06-04-2020