You will note that Richard now generates about 25% more from his panels than I do, but has backup storage for less than half the capacity of my system. That's why he has to run his generator so often.
Conservative system design suggests that your backup storage should be about five days usage, to allow for the fact that you are sure to experience substantial periods when your panels generate less power than you need, and as Richard points out, you don't want to let your state of charge fall too low, as this will affect their life, and they're the most expensive component in the system.
Just because it's a lovely day doesn't mean that your panels will generate as much power as you might like. I can count on about five hours per sunny day of reasonable input during winter – I'm on the same latitude as Newcastle. That improves if you move north, but Richard lives considerably south of me, and he'll get less.
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We both use Honda petrol (i.e. fossil fuelled) generators, but I only run mine very occasionally, even in winter. Even in summer I run it occasionally or the starter battery will go flat, and that's an inconvenience.
Both Richard and I have stand-alone systems, we're not connected to the grid. Our first backup is our batteries, second is our generator. We need two levels of backup, as will any such system.
If the Greens are going to achieve their target of 100% renewable energy there are a few obstacles to overcome, as our mutual experience indicates. Certainly it can never be achieved by relying on solar and/or wind power.
In the city, where most of Richard's constituency lives, consumers are part of an interconnected system. The backup needed for their solar systems is provided by the grid, which now and in the foreseeable future must rely on fossil fuels to ensure continuity. New battery technology will allow a first level of backup, but the grid will still be needed as a third level. The grid will also be needed to sell any excess power generated to the utilities. The thought of doing away with the grid within ten years is a fantasy.
Germany and Denmark are both countries boasting high percentages of renewable energy, but they have access to power sources that are not available in Australia. If the sun isn't shining in Germany, or the wind isn't blowing in Denmark, they can buy nuclear power from France or other sources that use natural gas turbines dependent on fracking and the Russians for supply. That's why their electricity prices are so high.
Ironically, Germans are now installing fossil fueled boilers for heating their homes – it doesn't get counted in the RNE targets.
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In Europe a distinction is made between 'carbon-free' and 'renewable' energy sources. The former allows the inclusion of nuclear power, which accounts for 27% of its electricity overall, and 53% of EU carbon-free electricity.
41% is provided by fossil fuels, 19% hydro and 14% renewables, mainly solar and wind. The target is to achieve 27% renewables by 2030.
The International Energy Agency expresses concern about the huge differences in energy prices between USA and EU, with gas prices three times as high and electricity twice as high in the EU. They are worried by the loss of international competitiveness and an increasingly chaotic retreat from the various subsidy schemes related to renewable targets.
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