Welcome to the sixth post in the Sustainable Energy without the Hot Air – A New Zealand Perspective series. Today we’re crunching the numbers on solar potential in New Zealand. For the background to the work please our introductory post here. Also check out our earlier posts on the potential of hydro power, geothermal and wind, and yesterday’s summary. Note: the units are in kWh/day/person – ie. if you ran a 40W lightbulb for 24 hours, it’d take ~1 kWh over the space of a day. We then divide it by person to give you a sense of the scale of the resource proportionate to the size of the population. Be sure to check out the methodology. For reference – we’re looking to replace around 55 kWh/d/p of energy currently generated by fossil fuels.
So, solar! We’ve got a lot of it, or do we? Our lower latitude means that New Zealand’s solar potential is certainly rather better than that of the UK and the current world leaders Germany. A roof inclined at the optimal angle in NZ gets on average 181W/m2 in Northland, 178 in Auckland, 195 in central Otago, 185 in Canterbury. (This is based on averaging all available NIWA hourly radiation data at suitable measurement sites). This is impressive compared to the UK average of 110W/m2 and 130W/m2 in Germany.
There are 4 ways to harness solar energy:
- Solar hot water – panels that directly heat water.
- Photovoltaic (PV) – panels that convert the sun’s energy directly to electricity.
- Concentrated Solar Power (CSP): Actually a range of technologies that use reflectors to concentrate solar energy either into heat engines or onto very high efficiency PV.
- Biofuel – photosynthesis; this is considered separately.
Installing 10m2 of north-facing, solar hot water heating panels could deliver 8kWh/d/p of hot water per person per household (average household being 2.6 people). While this amount of energy is more than we require, sadly we currently are unable to store it for colder, gloomy winter days. Photovoltaic PV panels on 20m2/p of north-facing roof (3kW system) would deliver 4kWh/d/p per household, which is more than enough to cover the baseload energy use of a NZ house during sunshine hours, and has the benefit of being able to feed extra power generated into the grid for use elsewhere.
What about having a solar farm instead of using everyone’s house? Let’s consider, for example, covering all of Central Otago (which has pretty decent irradiation levels) with concentrating solar power station installations with efficiencies of 15W/m2. We could halve the area to allow for skifields, dwellings, shaded slopes, mountain tops, etc. This gives us a huge 330kWh/d/p! However, the environmental and fiscal costs would also be huge, and probably unacceptable. If we confine these solar farms to an area the size of the Maniototo (40,000 hectares, which is a block 20km x 20km, OR for you North Islanders, is roughly equivalent to the size of the Auckland urban area) we could still provide 30kWh/d/p if completely covered. While such a scheme would provoke outrage, it should be pointed out that these concentrating solar farms deliver 5-8 times as much power per square meter as wind, so the overall impact footprint on the New Zealand landscape would be a lot lower. The cost is currently 2-3 times hydro, geothermal and wind but is likely to come down in the near-future. Further, the price of PV panels is now about 2/5ths of what it was in 2009 and keeps dropping.
On an individual house basis, installing, say, 5kWh/d/p of solar hot water heating makes good economic sense especially if you use a lot of hot water (or have teenagers!). Larger scale investments will have to wait for relative costs to improve, but a potential for 9kWh/d/p of house-based PV plus 34kWh/d/p of large scale solar production for a total of 48kWh/d/p seems reasonable.
A small note on the Parliamentary Commissioner for the Environment report on solar hot water heating: The commissions findings that solar hot water heating is not particularly beneficial for reducing emissions (as they did little to reduce peak demand, which is overall the most polluting form of generation) is very valid. We still believe there are other benefits to be had from solar hot water heating such as insulation against rising energy costs and hot water in the event of a blackout. That said, the Commissioner’s recommendations about shifting hot water heating to a night cycle is something everyone should do: it saves money, and helps the country by consuming non-peak power to heat water.
Conclusion: New Zealand has great irradiation scores compared to other countries that are actively promoting solar, and the costs are rapidly declining to the point that it’s likely to be cost-competitive without subsidies soon. Like wind, the energy generated is variable (generated during the day, though bigger solar plants can generate at night) but again can be balanced by using hydro. In short: Solar has large potential and is the way of the future.
There is a heap of material on solar out there, but a good place to begin is with Do the Math (can you tell we really like Tom Murphy’s work?). The UCSD professor breaks down the potential for solar at a global level. We should note that this is the same article as was linked in the wind post. If any readers have any further sources that are worth reading, please feel free to suggest them in the comments section.