Can renewables meet public and political expectations?

In 2012, in assessing how well a new carbon tax would work, I expressed reservations about renewable energy. Pricing emissions to make clean energy more competitive is a sound economic strategy. But the envisaged replacement technologies, especially renewables, were simply not up to the job. Feeble, intermittent solar and wind energy could not effectively replace fossil fuels, desirable as that may be, and these adverse characteristics of renewables are immutable.

In the intervening years public enthusiasm for solar and wind energy has not wavered. '100% renewables' is now a common mantra. Greens policy is to "ensure that energy generation is at least 90% renewable by 2030 and our energy efficiency is doubled". The ACT government says it will better its 90 per cent renewable energy target by 2020.

This enthusiasm for renewables reflects typical expectations of the Australian public. Can they be met? Should developments in energy technology and economics overturn my earlier doubts? Please note that there is no climate scepticism in my questions. Like the Ecomodernists, one can be critical of reliance on renewables while supporting strong action on carbon emissions.

Ideology and politics are of course connected with public sentiment on energy technologies and sources, especially coal and nuclear. One sees a growing opposition to investment in the fossil fuel sector. There are campaigns against the banks that fund the sector, universities are divesting their conventional energy portfolios and there are prominent campaigns against fossil fuel exploration, mining and use.

Australia is one of the countries where nuclear power is illegal or otherwise restricted. One source says thatAustralian public opinion on nuclear energy is presently about equally divided, but Friends of the Earth reports lower support. Recently the South Australian Nuclear Fuel Cycle Royal Commission Report recommended that the South Australian government "pursue removal at the federal level of existing prohibitions on nuclear power generation to allow it to contribute to a low-carbon electricity system, if required".

Energy technology advances

There are abundant good news stories about growing renewables investment and declining costs, e.g. for solar photovoltaic (PV) and solar thermal technologies. The technologies themselves are improving incrementally. Enthusiasts claim that renewables are already cheaper than alternatives. Great! No need for subsidies or carbon pricing! Since not a single national climate policy is based on this premise, it seems safe to bet that the enthusiasm is premature.

Domestic rooftop solar PV in Australia's urban areas is thriving, doubtless encouraging favorable perceptions of renewable technologies generally. But rooftop PV is a special case; it can't simply be extrapolated to larger-scale generation on dedicated sites. For example, the land and elevated mounting structures (i.e. roofs) come at zero marginal cost. Existing infrastructure facilitates access for equipment, materials and labour. Existing connection to the grid obviates the need for storage or backup to guarantee continuous power supply.

Many solar PV users claim they are self-sufficient in energy. They misunderstand the term. Australian households on average use around 25 gigajoules (GJ) of electrical energy per year. Australia's total primary energy supply averages around 660 GJ per household per year. That's the energy that goes into all the goods and services that an Australian household enjoys – food, clothing, shelter, transport, infrastructure, communications, education, health, entertainment, holidays – the list goes on. A domestic solar PV system might provide 100% of a household's electricity, but that's a mere 4% or so of the total energy sustaining that household's living standards, a far cry from '100% renewables'.

Two low-emission technologies, geothermal (enhanced geothermal systems, EGS, a renewable), and carbon capture and storage (CCS, not a renewable), figured prominently in earlier Australian energy scenarios. Geodynamics Ltd demonstrated EGS at significant scale but the company has since diversified in the clean energy sector, away from EGS. Other EGS activity has declined. Development activity in CCS continues but full scale demonstration in power generation has not occurred and one senses a decline in enthusiasm at government level. However, globally there are many active projects (plus several that are cancelled or inactive).

In my view both of these technologies face immense hurdles. EGS requires costly large-diameter wells several kilometres deep. Superheated brine must keep flowing for years at rates of several cubic metres/second through fractured rock strata. Fluid flow is bound to be affected by processes like mineral leaching, reprecipitation and pore blocking. The CCS process faces extreme challenges of scale, described by Trainer as "effectively having to construct plant capable of processing, transporting and burying more than three times the weight of all the coal, gas and oil produced each year".

Overall, I don't believe that developments in solar or wind technology have changed their intrinsic limitations or the prospects of '100% renewables'. The Australian 2010 report Zero Carbon Australia 2020 Stationary Energy Planwas a 10-year roadmap for 100% renewables; in 2014, almost the halfway mark, wind and solar accounted for 6% of our electricity and less than 1% of total energy.