Thursday, May 19, 2011

How much energy will we need?

According to David MacKay's book Sustainable Energy - Without the Hot Air, the UK will need 70 kWh/pp/day to cover final energy needs for electricity, transport and heat. This is equivalent to 100 GJ/pp/yr of final energy.

In his book Energy at the Crossroads, Vaclav Smil argues that we can get by with 50-70 GJ/pp/yr - 70 GJ was roughly the energy consumption of Japan / France in the seventies.

The above graph comes from the recent Energy Report and gives an overview of estimates for primary and final energy needs towards the middle of this century.

The good news is that - in a 100% renewable system - the distinction between primary and final energy fades, and that we could suffice with 300-500 Exajoules of annual energy consumption. In a world of 9 billion people, this means 33 - 55 GJ/pp/yr, after we electrify personal transport and massively insulate buildings.

Monday, May 16, 2011

Four integrated energy visions

Solar Array récupéré de http://en.wikipedia.or...Image via WikipediaVision #1: Sustainable energy without the hot air
In his book, David Mackay works out the numbers for the UK. He uses a common unit (kWh/pp/day) and uses this to calculate daily energy needs for electricity, heating and transport, concluding that UK could be run on 70 kWh per person and per day. Then he reviews which sources could contribute to this demand, and develops 5 plans for powering Britain.

Vision #2: Searching for a miracle
This report by Richard Heinberg is all about the Energy Return on Energy Invested (EROEI) of various energy sources. It reviews 18 energy sources, and comes to a worrying conclusion. EROEI is decreasing rapidly.

Both experts emphasisize the need for energy conservation and on the advantages of electricity as an energy carrier. They see only very limited potential for bioenergy. Both see major potential for wind power, photovoltaics and concentrated solar power.

Vision #3: Providing all global energy with wind, water, and solar power
In this paper, Mark Jacobson estimates that a 100% renewable system will require 3,800,000 5 MW wind turbines, 49,000 300 MW concentrated solar plants, 40,000 300 MW solar PV power plants, 1.7 billion 3 kW rooftop PV systems, 5350 100 MW geothermal power plants, 270 new 1300 MW hydroelectric power plants, 720,000 0.75 MW wave devices, and 490,000 1 MW tidal turbines. It is one of the first global visions for 100% renewables, relying primarily on electricity.

Vision #4: The Energy Report
This report is a joint project between WWF and Ecofys also proposes a global, 100% renewables vision. Like the Jacobson report, it foresees a major role for electricity - a common characteristic for the 4 visions, but it also expects major contributions from bioenergy, e.g. for marine transport, aviation and industrial heating processes.

For these last 2 visions, Leonardo ENERGY is organising webinars on June 14 and June 16 where the respective authors will present their findings.

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