Assessing Alternatives to Fossil Fuels
Examining McKay
In class, we will work through examples of the McKay’s estimates together, using the same approach he used for Great Britain to consider the potential for renewable energy systems in the U.S. In preparation for class, please consider how McKay estimates the wind power potential for Great Britain. He expresses wind power potential as the average amount of energy (kWhr) that could be supplied per person each day. His back-of-the-enevelope calculation assumes that the windiest 10% of country, equal to 400 m2 of land per person, is covered in windmills that can produce 2 watts/m2 of electricity on average. Electricity production per unit land x amount of land available/person-day is the basis for his estimate (along with necessary conversion factors watts to kW; hrs to days) for Great Britain’s wind power potential of 19.2 kWh/per-day. See the equation below:
Make sure to spend some time to understand this calculation before you come to class.
In class, you professor will outline the approach taken by McKay for estimating the technical potential of Great Britain moving away from its fossil fuel dependence. In general, McKay follows these steps:
- Consider the technical potential of renewable energy systems to supply our current energy needs
- Consider the potential of energy conservation in reducing our need for energy
- Consider what realistically may be the gap between energy needs with conservation and what renewable energy systems can supply
- Consider a mix of other carbon-neutral alternatives to cover the gap such as nuclear, clean coal, or the importation of energy produced from renewable supplies elsewhere (e.g. electricity produced from solar farms in the Saharan desert).
In reviewing McKay’s estimates, some of you might rightfully ask why nuclear power is seen as only a stop-gap energy source in this stepped process. This could be seen as an implicit assumption by McKay that compared to renewables, nuclear is seen as less preferred given its risks. Still please note that nuclear power figures prominently in McKay’s “Economist’s Plan” — the plan that is seen as being most economically feasible. If you are not aware of the controversy that surrounds nuclear power as a way to address climate change, continue to the next page.
A watt is a unit of power, or rate of energy use or production, defined as one joule (energy unit) per second. A kilowatt (kW) is 1000 watts. There are many different ways of expressing energy -- McKay uses kilowatt-hour (kWh). Convince yourself that 1 kW-hr is 1000 watts used or produced over an hour period, is a unit of energy (e.g. rate of energy use x time of use = amount of energy).