Does Renewable Energy Reduce CO2?: The Case of Wind

Herbert InhaberRisk Concepts

Las Vegas, Nevadahinhaber@hotmail.com

Presented at Third Santa Fe Conference on Global and Regional Climate Variability, October-November 2011

What is seen and not seen (after Bastiat, French economist)

Windmills – seen

Backup fossil fuel plants when wind doesn’t blow - unseen

CO2 Reductions with Intermittent (Variable) Energy Sources: How Much?

CO2 reduction is almost one-for-one for small number of windmills or solar collectors

BUT....

What Happens when Fossil Fuel Backup is Turned on and Off?An analogy: 2011

Toyota Camry mileage over highway and city (33 highway, 22 city)

Highway miles per gallon is always higher than city mpg

Stops and starts reduce efficiency, create greater pollution per mile driven

Another Analogy•Very few people have seen gas turbines turned on and off•However, starting a lawn mower is similar to that action•Even when the mover is later re-started, there is considerable pollution emitted, although perhaps less of a cloud

In the same way, fossil fuel backup starts and stops create more CO2 than continuous operationIn some regions (e.g., Germany), there is so-

called “feed-in” requirementsWhen windpower is generated, fossil fuel

backups are turned off or downThis frequent cycling produces more CO2

than continuous operationThus CO2 savings from windpower is greatly

reduced

But won’t windpower average out; i.e., when wind stops in one area, it will blow in another regionWindpower

production in the E.On Netz system, 2004

This covers much of Germany, from Bavaria in the south to the German Bight in the north

There is very little averaging

Will storage solve the frequent starts and stops of windpower backup? Picture is of pumped

storage in S. Carolina

There are 17 such systems in the U.S.

In principal, this type of storage could even out wind variability

But these systems are tiny in comparison to electricity demand

Storage to solve windpower problems – continued

Chemical storage (molten salts) has been tried since 1974 (Univ. of Delaware)

Cost on large scale would be prohibitiveLead-acid battery is still the cheapest (after

130 years) per unit energy stored – invented by Planté in France

Again, large-scale cost would be enormous.Example: Cost of lithium batteries in a recent

electric car is $18,000 – they store about $1.50 worth of electricity

Nissan Leaf

$18,000 worth of batteries holding about $1.50 of electric energy

Results – cycling of backup substantially reduces CO2 savedData collected

from around the world

Bentek (2010)– Colorado

Bentek (2010) – Texas

German study – 2005

Ireland - 2004

Results - continuedEstonia – 2007De Groot and Le Pair – “it is necessary to

establish on the basis of data, rather than model predictions, the level of extra fuel...”

U.S. National Academy of Sciences: “the committee estimates that wind energy... [p]robably will contribute to offsets of approximately 4.5% in U.S. emissions of CO2...”

ConclusionsResults have strong implications for plans to reduce

CO2 emissions by deploying windpowerResults are applicable to other intermittent

renewables such as solar photovoltaic and solar thermal

The only renewables exempt from this limitation of CO2 emission are hydroelectricity and geothermal, which have self-storage of energy

Results place in question President Obama’s goal of about 80% of American electricity supplied by renewables by 2035, presumably to reduce CO2 emissions substantially.

Uncertainties Type of fossil fuels Some literature is polemic Degree of intermittency Open or closed cycle gas turbines Some utilities don’t supply data Types of fossil fuels used as back-up How variable is the wind Export of wind energy (Denmark) Many others

Action Plan to Reduce UncertaintiesIn principle, regulatory agencies (public utility

commissions [PUCs] in the U.S.) and electrical utilities should gather and analyze data on the “missing” CO2 reductions

They generally do not do so because any expenditures on wind and other renewables are passed on to the consumer. Both PUCs and utilities state they are reducing CO2 emissions, but do not calculate how much

Consumers should know what reduction of CO2 they are getting for their increased costs

Summary

The story of the tea bag label