PLANET GOING SOLAR as payments are made and are responsible for maintenance. This arrangement works best if in-home electricity usage is high, but obtaining a loan and buying outright is probably preferable where possible. As usual, look carefully at the contract.
INVERTERS & FEED-IN-TARIFFS Every grid-connected solar installation requires an inverter. These convert generated DC current into usable AC and are rated according to their capacity. One Australian company named Tindo Solar offers a special type of micro-inverter that’s rated to match an individual panel or a pair of panels. For other inverters, system performance is limited by the deficiencies of the weakest panel but the Tindo system allows each panel to operate independently.
System prices vary a fair amount and bargains are liable to mean poorerquality panels, less attention to detail and inferior installations, including a lack of corrosion protection. Metering works so that solar power generated is first consumed in the house and any excess is typically exported to the grid. At times of day when the panels are not generating, power is sourced from the grid. This brings up the issue of the feedin tariff (FiT), a payment for power fed to the grid. A “gross” FiT is one where power is fed back for a retail-equivalent price, the equivalent of the meter running backwards. In Australia and New Zealand, this is only available in the Northern Territory. Elsewhere, there are “net” FiTs in operation. From a recent high point of up to 60c/kWh, most of Australia’s FiTs have fallen dramatically to far below the peak retail cost, the exception being the Northern Territory. Switching power companies can yield a better FiT. As a consequence of the drop in FiTs, most households going solar are now looking to match system size to usage based on their recent electricity bills. Another tip is to run units such as pool pumps and heat pump water heaters off rooftop solar by adjusting the timers to operate during the maximum sun period.
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SOLAR POLITICS In a complex transition, centralised power generation and distribution is being disrupted by a rival decentralised model. Overinvestment in Australia’s poles-and-lines network during the late 2000s and early 2010s, known as “goldplating”, may result in unused assets. There are a number of ways in which solar users are being disadvantaged, in subtle or not-so-subtle ways. Some network and electricity companies that have been leaking revenue have been trying to recoup it via what are dubbed “solar taxes”. These have been introduced in Spain and Arizona and also by the New Zealand network company Unison for solar gridexporters in the Taupo and Rotorua area. Moves to introduce them in Australia have so far been unsuccessful. Proposals have been made in Australia to restructure bills to tilt the playing field against solar users, who would pay higher network charges. Sometimes solar owners are knocked back from discounts available to other customers. Following a directive by the Australian Energy Regulator in late 2015, solar customers are now required to pay their own meter charges, which were previously shared by all energy consumers, but fortunately these only amount to about $7 per quarter.
THE BATTERY OPTION Even more disruptive to the traditional network model are storage batteries. These were traditionally of the clunky lead-acid variety and intended for houses with no grid connection. Everything changed in April 2015, when Tesla made headlines with its Powerwall battery. Sleek and sexy, this unit can easily be attached to the wall of a garage. It is based on lithium-ion technology, with a 6.4kWh capacity, and requires a solar PV system of at least 4kW plus a new inverter. With Australia’s average daily electricity consumption being 18kWh per day and New Zealand averaging 22kWh per day, multiple units will probably be needed unless the household is frugal. A battery enables exiting the grid, storing all of the power generated, postponing power usage to a lower-tariff time of day (load-shifting) and keeping the lights on during power cuts. Choice in Australia has estimated a cost of at least AU$12,000 (with existing solar) or AU$14,000 (without solar.) Payback periods are long and likely to be well in excess of the 10-year
warranty. While the economic case fails to stack up the moment, prices are likely to drop significantly over the next few years. While no figures are available for New Zealand, they are likely to be broadly similar. A major environmental side-effect from most lithium-ion batteries is linked to the use of rare-earth elements. Radioactive thorium produced during refinement of rare earths is a major disposal headache with a half-life of 14 billion years. The world capital of rare-earth production is the Chinese city of Baotou, which has created a vast tailings pond full of toxic and radioactive dark sludge. Several other companies have entered the battery market in this region including AGL (Power Advantage),