One of the main arguments made against solar power in New Zealand is that the New Zealand electric supply already derives primarily from renewable energy sources anyway. Because of this, introducing home- or business-based solar power generation systems will do relatively little to improve the eco-sustainability of the business or household.
Today I’m going to take a look at some of the reasons why this is not the case, and that even with a power supply network derived primarily from renewable sources, there is still a lot to be gained from solar installations.
Variable power generation
Virtually all renewable energy sources generate levels of power that are variable. That means that they will each have peaks and troughs – some summers they will produce lots and lots of power, and other summers they will produce very little.
A good example of this is wind farms. No matter how many wind farms you have, you just never know what they are going to produce – and perhaps more importantly, when they are going to produce it. A group of 97 windfarms might produce 40 GWh during one season – and then drop down to 14 GWh during the next. This makes it very hard to forecast the results from energy generation, and when matched against a constant demand for energy, explains some of the large swings we have seen in wholesale energy prices over the last 12 months.
Falling Back on Coal and Diesel
When renewable power generation sources produce insufficient energy to meet the fairly constant level of daily demand, the New Zealand power market tends to fall back on reasonably cost-efficient but extremely carbon-inefficient fuels such as coal, gas and diesel. These fuel types are heavy emitters and often create around 40-50% of New Zealand’s carbon emissions from power generation while generating 7-8% of total power.
The very reason that we need to have these energy sources at all is because we simply cannot know how much our renewable energy sources will generate.
Marginal peak generation likely to be carbon inefficient
This means that the more energy you use during peak times, the more likely it is that that excess of consumption will be very carbon inefficient. As consumers use more and more power relative to limited current supply, the overflow has to be drawn from sources that are far less eco-friendly.
Impact of “dry winters”
This was the case during the recent “dry winter” (from May to August this year) where record low levels of hydro electric power generation and low levels of wind generation drove the wholesale cost of energy through the roof, at one point exceeding $200 per MWh (when it had sat steady at around $40 per MWh for the past 12 months). At this time, major energy companies were chewing their way through their coal supplies and New Zealand paid the price, generating as much as 1,700 tonnes of carbon emissions per hour.
Why reducing marginal demands on the grid is carbon efficient
The less marginal pressure on the grid, the less need we have for carbon-intensive emitting energy sources. The better prepared we will also be for future dry winters. This is the main environmental argument for solar – by introducing a new, highly local source of power generation for your home or business, you can not only reduce your ongoing costs, but you can also take pressure off the grid during periods of peak consumption.
Conclusion
Introducing solar power systems in New Zealand will not always be as environmentally advantageous as it would be in other countries that rely heavily on non-renewable energy generation sources such as coal or gas. But the reduction in marginal demand on the NZ grid will almost certainly result in lower levels of carbon emissions during periods where variable green energy sources produce below average results.
