Let’s get real about alternative energy

By | May 27, 2009

This is an important perspective on alternative energy from David MacKay, a professor of physics at the University of Cambridge:

David MacKay says people engage in wishful thinking about energy because they don't look at the math.We need to introduce simple arithmetic into our discussions of energy.

We need to understand how much energy our chosen lifestyles consume, we need to decide where we want that energy to come from, and we need to get on with building energy systems of sufficient size to match our desired consumption.  …

Let’s express energy consumption and energy production using simple personal units, namely kilowatt-hours. One kilowatt-hour (kWh) is the energy used by leaving a 40-watt bulb on for 24 hours. The chemical energy in the food we eat to stay alive amounts to about 3 kWh per day. Taking one hot bath uses about 5 kWh of heat. Driving an average European car 100 kilometers (roughly 62 miles) uses 80 kWh of fuel. With a few of these numbers in mind, we can start to evaluate some of the recommendations that people make about energy. …

In total, the European lifestyle uses 125 kWh per day per person for transport, heating, manufacturing, and electricity. That’s equivalent to every person having 125 light bulbs switched on all the time. The average American uses 250 kWh per day: 250 light bulbs.

And most of this energy today comes from fossil fuels. What are our post-fossil-fuel options?

Among the energy-saving options, two promising technology switches are the electrification of transportation (electric vehicles can be about four times as energy-efficient as standard fossil-fuel vehicles) and the use of electric-powered heat pumps to deliver winter heating and hot water (heat pumps can be four times as energy-efficient as standard heaters).

Among all the energy-supply technologies, the three with the biggest potential today are solar power, wind power and nuclear power.

As a thought-experiment, let’s imagine that technology switches and lifestyle changes manage to halve American energy consumption to 125 kWh per day per person. How big would the solar, wind and nuclear facilities need to be to supply this halved consumption? For simplicity, let’s imagine getting one-third of the energy supply from each.

To supply 42 kWh per day per person from solar power requires roughly 80 square meters per person of solar panels.

To deliver 42 kWh per day per person from wind for everyone in the United States would require wind farms with a total area roughly equal to the area of California, a 200-fold increase in United States wind power.

To get 42 kWh per day per person from nuclear power would require 525 one-gigawatt nuclear power stations, a roughly five-fold increase over today’s levels.

I hope these numbers convey the scale of action required to put in place a sustainable energy solution.

via Commentary: Let’s get real about alternative energy – CNN.com.

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