Two ambitious scenarios to supply 100% (or almost 100%) of global energy demand by renewable sources by 2050

Recently two ambitious reports are published to persuade the world that we can both secure energy supply and mitigate climate change by supplying 100% (or nearly 100%) of global energy demand from renewable sources. Their target year is 2050.
One proposal is analyzed by two scientists from California and the other scenario is from the World Wide Fund for Nature (WWF).

I. Jacobson and Delucchi (2010), and Delucchi and Jacobson (2010)

Authors are confident that wind, water (wave, tidal, hydroelectric, and geothermal), and solar (solar photovoltaics and concentrated solar power) power (WWS) at current technology levels can satisfy all new energy demand by 2030 and replace all pre-existing non-WWS energy capacity by 2050.
They assert that their proposition is technologically and economically possible.
Before all, they dismissed promises of other self-declared clean energy sources such as coal with carbon capture, biofuels (corn ethanol, cellulosic ethanol, soy biodiesel, algae biodiesel, biomass for electricity, unmanaged grasses in non-agricultural habitats, etc.), natural gas, and nuclear power. Then they showed how WWS can be ultimate energy sources which are not only sufficient enough but also reliable and stable.

First, they demonstrated WWS has enough potential to supply all the world energy demand.
In likely-developable locations, wind alone has 3-5 times the global energy demand. In likely-developable locations, solar can satisfy the world's energy needs 15-20 times.
And if the world is transformed into all-WWS one, we will demand less energy. This all-WWS world would demand 11.47 TW in end-user power, which is 30% less than the US EIA-projected conventional fossil-fuel world (16.92 TW).
This scenario requires electrification of all energy facilities. More specifically, 30% energy demand reduction can be achieved by:
(1) Direct use of electricity for heating or electric motors rather than fuel combustion for the same purpose
(2) Use of electrolytic hydrogen than fossil fuels for transportation
(3) Modest demand-side conservation measures
(4) Energy savings by avoiding petroleum refining
(5) Substitution of all fossil-fuel vehicles with battery-electric vehicles (BEVs) and hydrogen fuel-cell vehicles (HFCVs)

Second, the all-WWS world will be guaranteed stable supply of energy by:
(1) interconnecting geographically dispersed and naturally variable energy sources (e.g., wind, solar, wave, and tidal)
(2) using a nonvariable energy source, such as hydroelectric power, to fill temporary gaps between demand and wind or solar generation
(3) using "smart" demand-response management to shift flexible loads to better match the availability of WWS power
(4) store electric power, at the site of generation, for later use,
(5) over-size WWS peak generation capacity to minimize the times when available WWS power is less than demand and to provide spare power to produce hydrogen for flexible transportation and heat uses,
(6) store electric power in electric-vehicle batteries
(7) forecast the weather to plan for energy supply needs better

This two-part proposal is very straightforward!
However, two problems I found about this proposal are:
(1) The authors require an astronomical number of power plants in just two dadades. For example, they call for 3.8 million wind turbines and 1.7 billion roof-top PV systems by 2030.
(2) The article didn't address the inevitable grid-connection problem that countries have to solve when they are geographically or politically isolated.


II. WWF International, Ecofys, & OMA (Office for Metropolitan Architecture) (2011)

This report is different from the article mentioned above in that it supports biofuels and does not require 100% electrification.

The proposed scenario is:

Overall results based on the scenario are:

(1) Global energy demand, split by energy carrier

(2) Global energy supply, split by source


To realize the scenario, the authors have 10 recommendations:
1. CLEAN ENERGY
Promote only the most efficient products.
Develop existing and new renewable energy sources to provide enough clean energy for all by 2050.
2. GRIDS
Share and exchange clean energy through grids and trade, making the best use of sustainable energy resources in different areas.
3. ACESS
End energy poverty.
Provide clean electricity and promote sustainable practices, such as efficient cook stoves, to everyone in developing countries.
4. MONEY
Invest in renewable, clean energy and energy-efficient products and buildings.
5. FOOD
Stop food waste.
Choose food that is sourced in an efficient and sustainable way to free up land for nature, sustainable forestry and biofuel production.
Everyone has an equal right to healthy levels of protein in their diet.
For this to happen, wealthier people need to eat less meat.
6. MATERIALS
Reduce, re-use, recycle - minimize waste and save energy.
Develop durable materials.
Avoid things we don't need.
7. TRANSPORT
Provide incentives to encourage greater use of public transport, and to reduce the distances people and goods travel.
Promote electrification wherever possible, and support research into hydrogen and other alternative fuels for shipping and aviation.
8. TECHNOLOGY
Develop national, bilateral and multilateral action plans to promote research and development in energy efficiency and renewable energy.
9. SUSTAINABILITY
Develop and enforce strict sustainability criteria that ensure renewable energy is compatible with environmental and development goals.
10. AGREEMENTS
Support ambitious climate and energy agreements to provide global guidance and promote global cooperation on renewable energy and efficiency efforts.

Although Ecofys who built a model for this report thoroughly investigated the global energy problems and its proposal seems more plausible than the previous two-part article, I cannot agree with this report because they are advocating controversial biofuels.



Sources:

Jacobson, M. Z., & Delucchi, M. A. (2010). Providing all global energy with wind, water, and solar power, Part I: Technologies, energy resources, quantities and areas of infrastructure, and materials. Energy Policy, doi:10.1016/j.enpol.2010.11.040 [Full-text available at http://j.mp/JandD_1]

Delucchi, M. A., & Jacobson, M. Z. (2010). Providing all global energy with wind, water, and solar power, Part II: Reliability, system and transmission costs, and policies. Energy Policy, doi:10.1016/j.enpol.2010.11.045 [Full-text available at http://j.mp/DandJ_2]

WWF International, Ecofys, & Office for Metropolitan Architecture. (2011). The Energy Report: 100% Renewable Energy by 2050. Gland, Switzerland: WWF International. [Full-text available at http://j.mp/WWF_Report]