In my previous post I emphasized the need to focus on
actions that could have a significant impact on greenhouse gas emissions. I ended the post noting that shale gas, shale
oil, and other unconventional resources can help us buy time to develop CO2-free
sources of electricity. It got me
thinking about the relative amounts of CO2 emissions abated
through the expanded use natural gas vis-à-vis the
deployment of wind and solar technologies.
The recent Short Term Energy
Outlook report by the Energy Information Agency provides an unequivocal
answer: substantially greater amount of
CO2 emissions have been avoided by displacing coal with natural gas
to generate electricity than by deploying wind and solar technologies. Here are the numbers:
Between 2004 and 2011, the annual production of electricity
in the US has stayed around 4,000 TWh (0.26 CMO). Over this period the contribution of coal has
dropped from 2,000 TWh to 1,500 TWh, while the contribution from natural gas
has increased by 500 TWh (from 700 TWh to 1,200 TWh). Nuclear- and hydro-power were largely flat
over this period, and a decrease of about 100 TWh from oil is offset by an
increase in wind and solar power.
Figure 1. Total electricity generation in the US has remained
largely flat since 2004 with the most significant change being a swap of 500
TWh between coal and natural gas.
The CO2 footprint of electricity from natural gas
is half that of coal, and so the amount of CO2 abated through
expanded use of natural gas is equivalent to that emitted upon producing 250 TWh
from coal, about 550 million metric tons.
Meanwhile, wind and solar power in the US increased from 20 TWh to 130 TWh. Thus the amount of CO2 abated by
fuel switching from coal to natural gas is about twice as much as that avoided
by wind and solar generation. And, that
reduction was accomplished by market forces.
If our objective is to reduce greenhouse gas emissions, and it should be
so, then in the short term we can achieve greater reductions by promoting fuel
switching without having to decrease electrical power production, which would
adversely affect the nations economic vitality.
It so happens that there are abundant resources of shale gas
also in Europe, China, and many other regions. IF they were developed globally, we could slow
down the rise of ghg emissions without reducing the total electricity
supply. Of course, they have to be
developed responsibly: with best practices to avoid contaminating water or
causing other environmental damage.
Don’t get me wrong; I am not against developing wind or
solar systems of power generation.
However, policy makers charged with reducing CO2 emissions
have to also consider the impact of supporting commercial scale deployment of
solar with feed-tariffs or renewable portfolio standards, and the attendant drag
on economy, which inevitably pushes more people into poverty.
As I write this piece, India is suffering through a major
electricity crisis: 600 million people lose power for hours on end. No light, factories
idle, no air conditioning, no fans, no elevators, transportation snarled.
Ouch!!
CO2 emissions from wind are worse than you might think. Their capacity factor is about 30%, so for each wind turbine there must be a source of quick-ramping electric power that can provide energy for 70% of the time. That source is natural gas combustion turbine generation (NGCT) because they can start up quickly, like airplane engines.
ReplyDeleteNatural gas is clean relative to coal, in that it generates about twice the heat energy per kilogram of CO2 emitted. However, NCGTs have a electric/thermal efficiency of about 30%. The combined cycle gas turbines (CCGTs) that could replace baseload coal power use the gas turbine exhaust to boil water used in a steam turbine, generating power both from gas combustion turbines and steam turbines. The electric/thermal conversion efficiency is about 60%. But CCGTs can not back up wind turbines because they do not ramp power up and down fast enough.
As a consequence, wind turbines with NGCTs for backup consume more natural gas than CCGTs alone. There is more on this in my new book...
http://www.thoriumenergycheaperthancoal.com
Your understanding and usage of capacity factor is wrong and, therefore, some of your "important" conclusions, too:
ReplyDelete1) Wind turbines in a larger area do not have the the same maximum and mimimum production times. This leads to interesting observations/conclusions:
a) The maximum backup power must exceed 70% of the demand, however this higher demand is only needed for few hours per year.
In Germany, for example, only 4% of the currently installed wind power can be considered as reliable base load, if you connect production sites from France to Poland, you would get a much number (~15%).
b) You can install a much higher wind power without loosing much of the produced energy. As a result, you need much less chemical energy (methane). If 50% excesss power only produce 7% wasted energy, there is no argument for your numbers.
2) You work with data for wind turbines, which are obsolete or at least ignore current developments, e.g. with turbines optimised for weak wind you can increase the capacity factors of on-shore wind turbines.
3) Wind is quite predictable in larger areas. You would, therefore, use a mixture of different NG power plants. And very important, there are other possibilities available to flatten production and demand peaks like pump storage and compressed air storage, the latter can easily be combined with NG plants. In addition, during spring-autum you can nicely combine wind with PV - even less chemical energy needed.
If you want to promote nuclear energy -in principle no problem for me- you should start with better arguments when it comes to the rejection of alternatives. In the current form you do more damage than good for promoting nuclear energy, especially when you compare a technology like thorium reactor which is in best case only in the experimental stage with working alternatives.
In addition, with prices of around 5000 USD /kw in existing modern reactors the production costs for nuclear electricity does not longer look so promising for me.