How to double the country’s power, no land required
New Zealand could nearly double its electricity supply by putting floating solar panels on a fraction of reservoirs and dams, experts estimate. The system doesnt require valuable or productive land, says Rogier Simons, general manager of energy company Vector Powersmart. The water keeps the solar panels running efficiently, while the panels can reduce evaporation. But despite floating solar being built en masse overseas, theres just one moderately sized system in Aotearoa which Vector helped construct on an Auckland water treatment plant. And a freshwater scientist thinks Kiwis especially those who enjoy boating and fishing are unlikely to accept the technology on natural waterways. The Rosedale wastewater treatment plant on Aucklands North Shore was looking to reduce its carbon footprint and cut costs, Simons said. Floating solar seemed a great fit, he added. With the population growth in Auckland, that land is at a premium... But the reservoir was a piece of real estate that wasnt really used, Simons said. More than 2700 solar panels are connected to 4000 recyclable plastic floats, with more than 65 anchoring points around the array plus electricity cables and moorings to the land. We built the whole system on the land, row by row, and it went down a ramp, Simons said. Each of the four quarters were then pulled by boat into position, and the anchors were dropped. The 1 megawatt system, using tech from French company Ciel et Terre, only covers a few per cent of the reservoir. It provides the equivalent power of 200 homes. It was quite ground-breaking. At the moment, floating solar systems are more expensive to construct than land-based arrays, Simons said. But there are benefits that could outweigh that. Solar also works relatively well in cooler temperatures, so you get a little bit of gain in the efficiency of the panels. The system limits evaporation which could be increasingly important in future as regions face longer periods of dry weather. When a higher share of a waterway is covered, the set-up can limit algal blooms, according to Canadian, Chilean and German researchers. With its Lego-type assembly, systems can be easily expanded, he said. Solar including rooftop and land-based panels produced less than 1% of the countrys electricity last year, according to government data . Yet homeowners, businesses and energy companies are increasingly embracing the low-cost, low-carbon source of power generation, Simons said. Vector Powersmart envisioned the Rosedale array as a pilot project, although it hasnt been replicated to date. Floating solar could be installed on ponds, reservoirs, coastal areas where waves arent too high, dams and quarries which often have water ponds, Simons added. It definitely has the potential to be part of the energy mix. Meanwhile, other countries are embracing the tech. China, Japan and South Korea are building floating solar arrays 100 times the size or more of the Rosedale system. With plenty of lakes and reservoirs, New Zealand has a comparatively large opportunity to boost its green power supply with floating solar, according to a scientific study published earlier this year. Floating panels covering 30% of 407 reservoirs around the country could generate 38 terawatt-hours of electricity each year. According to government estimates, New Zealand consumes 39 terawatt-hours annually. The researchers said a floating array reduces evaporation directly below itself, but also in the surrounding uncovered areas of water. Therefore, the panels would also cut each reservoirs evaporation by nearly half. The international research team said floating solar was particularly suitable on pumped hydro dams since the panels could power the pumps. The Government is investigating whether a pumped dam in Central Otago or Tongariro could be an efficient, low-emissions way to store energy during dry years. Lake Onslow proponent Earl Bardsley didnt think the alpine lake in Central Otago, which was snowy and icy in winter, would be a good fit for floating solar. Simons agreed floating solar wouldnt be suitable for areas that experience freezing temperatures or high winds or large waves. In addition, Bardsley thought people would object. Local folk would think a big water level range is already enough of an impact on the lake without the added visual issue of extensive floating panels getting in the way of their boats. But electricity companies might also build smaller-scale pumped hydro plants to provide peak-time power each morning and evening, Bardsley said these projects would pair well with floating solar tech. Freshwater ecologist Mike Joy was chilled by the prospect. Light is the source of all life. So taking the light away is going to have negative effects on the lake... Its bonkers. Smaller arrays would have less of an ecological effect, Joy said but then might not reduce evaporation. New Zealand had recently upended decades of prioritising the use of water to make money, with the release of Te Mana o te Wai policy . The onus is on protecting freshwater ecosystems above and beyond anything else... putting the river, the lake or the groundwater first. There were comparatively few manmade waterways, Joy said. Large arrays would stymie the beauty of natural lakes, he added. Many of New Zealands hydro lakes were recreational areas, where people enjoyed boating and fishing. You cover them with solar panels and you wipe that option out. Our weekly email newsletter, by the Forever Project's Olivia Wannan, rounds up the latest climate events. Sign up here .