Transcript Does Renewable Energy Reduce Greenhouse Gases: The Case of

Herbert Inhaber
Risk Concepts
Las Vegas, Nevada
[email protected]
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 operation
 In some regions (e.g., Germany), there is so-called
“feed-in” requirements
 When windpower is generated, fossil fuel backups are
turned off or down
 This frequent cycling produces more CO2 than
continuous operation
 Thus 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
region
 Windpower 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 prohibitive
Lead-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 saved
 Data collected from




around the world
Bentek (2010)–
Colorado
Bentek (2010) –
Texas
German study –
2005
Ireland - 2004
Results - continued
 Estonia – 2007
 De 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...”
Conclusions
 Results have strong implications for plans to reduce
CO2 emissions by deploying windpower
 Results 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 Uncertainties
 In 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