What is environmentally sustainable is up for debate

Despite our political differences, Greens leader Senator Richard Di Natale and I have a lot in common.

In 1997 my wife and I left the big smoke to live in the bush. We purchased a block of land that we loved and built our house – a house that was ecologically sensitive and fitted well into the environment.

We had the choice of connecting to the grid or going offline, both choices cost about the same. But connecting to the grid would involve cutting a swathe through the trees on our property, and that was unacceptable, so we went solar.

We fought the council to install a composting toilet, and won that battle. They wanted us to install a particular brand of septic toilet that they considered ecologically desirable, but when we discovered that it used so much power that we would need 14 extra panels and considerably bigger batteries, we persevered. "It's our job to protect people like you from yourself" we were advised by a council officer. Now, of course, they encourage composting toilets. Ideas of what is clean and sustainable change over time, and there's always someone with your interests at heart to advise you.

Recently I was interested to learn from an online magazine One Step off the Grid (http://onestepoffthegrid.com.au) that Richard had followed much the same path some years later.

Reporter Emma Sutcliffe, when she visited the Di Natale property was greeted by the Senator riding a quad bike – and not wearing a helmet! "Despite plenty of sunshine," she writes, "their backup generator is humming, providing power to top up the state of charge [of their battery bank]."

"During winter we run the generator two or three times a week," Richard explained. He tells her that the batteries, now ten years old will probably need to be replaced next summer.

We both made the same mistake with our initial installation, which soon proved to be too small. Richard installed a 1.2kW system, mine was a bit less than 1kW. Improvements in technology over the years and generous government subsidies made it cheaper for Richard.

I installed a bank of lead-acid batteries that stored 720 amp hours, Richard's sealed gel batteries store 600 amp hours.

We have both upgraded our systems. The life of the BP solar panels I installed was expected to be 10 years – mine lasted a bit longer, but I replaced the whole lot with new panels totaling about 2kW, and guaranteed for twenty five years, which will outlast me. Richard upgraded to 2.5kW by adding to his existing BP panels.

With the new panels I upgraded my batteries to a bank of gel batteries that store 1300 amp hours.

We both have solar hot water boosted by a 'wetback' to our wood fire, which doesn't please those over-concerned with clean air policies. There are periods in spring and autumn when we don't need a fire and when the sun doesn't warm the water sufficiently, so we can also run the generator to ensure that we can have a warm shower.

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.

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.

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.

Almost 30% of the EU's generating capacity comes from natural gas. Ironically, as the USA takes advantage of shale gas, they are exporting coal to the EU at prices which make its use very competitive despite its higher carbon emission cost. As a result demand for gas has decreased by a third in the last three years. 39% of gas is imported from Russia.

In Australia, Richard and his Greens have called for 100% renewable energy. The ALP aims for 50%. These are substantially above European targets, and have to be achieved, if both parties stick to their policies, without nuclear, gas or hydro.

Worldwide, coal accounts for about 40% of electricity production, and will continue to do so for the foreseeable future. In innovation, research and job creation, Australia is in a position to be a world leader. Imagine the potential of creating methodologies for producing clean coal power! Redirecting some of the funds from the Clean Energy Finance Corporation to research in this area could be far more rewarding than further subsidizing the well established solar and wind industries.

Such research is being carried out by the CSIRO and other bodies. This research, and similar research into natural gas technology, currently receives subsidies of less than $1/MWh, compared to $412 for solar, $42 for wind and $18 for other renewables.

The ACT has announced ambitious targets for RNE – 100% by 2025. They are of course part of an interconnected system, and their backup will continue to be the national grid, generating about 70% of its power from fossil fuels. Meanwhile costs will rocket, as the ACT government has contracted for twenty years to purchase solar power at $184/MWh, and wind power at $92/MWh. NSW wholesale prices are $30-40/MWh. I wouldn't want to be a lower income earner in Canberra in winter! Perhaps they'll be like Germany and revert to fossil based fuel stoves for their heating, like Richard and me.

Can we achieve our targets with wind and solar?

Electricity of Tahiti (EDT) generates and distributes energy in over 20 islands throughout French Polynesia. These islands have adequate sunshine and wind that should ensure that they could be a major source of power, but this has not proven to be true. 66% of their power is diesel generated, 33% hydro, about 1% solar.

According to EDT: "Production of photovoltaic or wind generators can vary instantly and significantly, with fluctuations of up to 90% of the peak power on PV installations and 100% on wind generators. Therefore, they are often qualified as 'intermittent' or 'fatal' energy sources. These variations will cause inevitably voltage drops or surges that would impact the quality of the distributed power.

"To preserve stability of the system, share of intermittent energies must be limited to 20-30% of demand at all time. Beyond this limit, use of batteries is required. Renewable energies like wind or PV do not provide generation guarantee... it is necessary to have at all times enough generation capacity to guarantee the supply of energy, even if some generators are out of service or in maintenance, or to compensate variations caused by intermittent energies."

It's the same old problem. To ensure continuity of supply, systems require backup, and in Australia with existing technology, that means fossil fuelled, mainly coal, generators.

I don't know of any countries approaching 20-30% input from wind and solar.

The Green's 100% is clearly a pipe dream and should be dismissed. The ALP's 50% will seem achievable to some, and might prove to be a vote winner, as long as they don't have to come up with a plan that identifies and overcomes the obstacles.

At the moment the Abbott government's less ambitious target of 26% renewables looks to be at the outer limits of what is possible, but perhaps is achievable. It is in line with European targets. Certainly the decision to redirect the funding provided by the Clean Energy Finance Corporation away from wind projects should have the approval of everyone except the highly subsidised wind farmers. Solar power should similarly be excluded from such funding, so that money can be directed to technologies that might help us to bridge the more than 70% gap between our dreams and reality.

Richard Di Natale and I do have a lot in common. I think we both want to minimise our footprint on the planet, and ensure a bright future for our children – well grandchildren in my case. I'd like to sit down and discuss the appropriate use of all the available technologies, and plan a transition that doesn't threaten our economy and thousands of jobs. Unfortunately that's not possible when you have a constituency to worry about. We differ because he has another objective, and it's political.

If Richard is fair dinkum about sensible, achievable energy policies he'll renounce his party's ridiculous stance, and buy bigger batteries for his farm.