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There is general agreement world-wide that an a 100% renewably powered world would be a desirable objective, and that the renewable technologies are particularly well suited to provide the energy needed in the countries most vulnerable to climate change.

There is also a clear scientific consensus that renewable electricity generators emit the lowest greenhouse gases: at least nine times less than the lowest fossil fuel generators and in some cases 40 times less.

There are, however, powerful lobbies that argue that the renewables are too unreliable; expanding too slowly; and too expensive to supply the world’s electricity needs. Without, that is, significant help from the technologies the lobbyists are paid to represent – be they fossil fuel or nuclear.

Here is the evidence, some of it new and unexpected, that the lobbyists’ arguments at a variance with the realities. Two projects in Germany, under the collective name of Komikraftwerk (combined-power plant) have clearly demonstrated that the reliability objection is a myth.

Solar PV and wind power are complementary. Together they can supply around 80% of the electrical power needs of Germany. The only backup required is 17% biogas electricity and 5% storage power. Together they provide a renewable electricity supply that is reliable 24/7, summer through winter.

Recent evidence in a paper I wrote with the head of Kombikraftwerk and an Italian colleague in Nature Materials explodes the second myth. Wind and PV and wind power are expanding exponentially in many countries. The expansion is so fast in Germany that wind and PV could provide the foundation of an all-renewable electricity supply as early as 2020.

Had the savage cuts to the subsidies for PV and wind power in the UK not been implemented, wind and PV could likewise be on target to provide the backbone of an all-renewable electricity system just two years later, in 2022.

The third renewable objection, on cost, fails when one notes that, thanks to the expansion of wind and PV, the wholesale price of electricity in Germany has fallen 37% in the last three years. Good Energy, the all-renewable electricity company, points out that thewholesale electricity price in the UK started falling in 2014.

How to achieve all renewable electricity supplies

The conclusion to our study was that the fastest way to reduce carbon emissions is to ensure that all new electricity generators are renewable. Kombikraftwerk showed that PV, wind and biogas power, the three most established renewable technologies, provided the minimum requirements for an all-renewable electricity supply.

Many more renewable technologies can contribute. Some are established: large and small scale hydropower and geothermal power. Others are emerging: concentrating photovoltaics (CPV), concentrating solar power (CSP), wave, tidal stream and tidal lagoons.

Large scale hydropower and geothermal can back up PV and wind in a similar way to biogas, and to some extent so will tidal and CSP, the latter when it has a heat storage option that allows the sun’s heat to be stored up during the day, and used to generate power on demand at night.

Most importantly, all these renewables have carbon footprints, or life-cycle greenhouse gas emissions below the 50 gCO₂/kWh recommended by the UK Committee on Climate Change for 2030. The consensus in the peer-reviewed scientific journals is that the carbon footprint of nuclear power is above this limit. The lowest fossil fuel electricity generators are at least nine times higher.

So the simplest way to ensure the swift attainment of an all renewable electricity supply is for countries to impose a 50 gCO₂/kWh emission limit on all new electricity generation here and now. I suggest we call this the ‘Get it from the Sun’ principle (wind is, after all, solar-powered).

The evidence in our paper shows that the renewables are expanding so fast that this is a safe and reliable option as well as producing the lowest cost electricity.

‘Get it from the Sun’ is already a grassroots movement……

The fastest, cheapest and safest way to reduce carbon emissions

On the basis of the evidence reported in our paper in Nature Materials we make the following suggestions to all participants and demonstrators at COP21:

• Countries should set a date when an environmental life-cycle limit of 50 g CO₂/kWh will be imposed on all new electricity-generating technology.
• All fossil-fuel subsidies should be transferred to the renewables. They should be paid by taxation rather than a levy so that the fall in the wholesale electricity price due to the renewable expansion is reflected in the retail price per kWh.
• Kombikraftwerk power tests should be made on national and state electricity grids to determine the most appropriate mix of renewables from indigenous resources.
• Progress towards all-renewable goals should be measured on a frequent and regular basis.

Our data suggests that these three policies, taken together, will form the quickest, cheapest and safest approach to reduce the carbon emissions from electricity generation.

The paper: ‘Recent progress towards all-renewable electricity supplies‘ is by Keith Barnham, Kaspar Knorr & Massimo Mazzer, and published in Nature Materials.

Keith Barnham is author of ‘The Burning Answer: a user’s guide to the solar revolution‘ and Emeritus Professor of Physics at Imperial College London.    http://www.theecologist.org/News/news_analysis/2986468/goodbye_fossil_fuels_goodbye_nuclear_we_can_get_it_from_the_sun_all_of_it.html