energy system
sin_93147
GEOL241F2017Lect24--Consumption.pdf
GEOL 241 Fall 2017 Lecture 25: The Consumption Side – It is down to you and me!
Homework Essay #4 due via Blackboard, Friday November 17th, 5pm
2 page limit (see formatting guidelines on syllabus) – works cited can be in addition
Assume you are called upon to provide advice to the US Department of Energy (DOE) about where it should focus its attention strategically for the next 10-20 years. Based on what you have learned in this class, write an essay that makes the case for the one most important area where you think the DOE should put its effort. What do you think the greatest challenge will be in developing the energy system for the future? What are some ways that we might overcome the challenge you have identified?
As in the case of the prior essay assignments for this class, we are not looking for a “right answer” but are interested in you thinking about this issue. Establish the basis for your argument in what we have learned in class, supplemented by your own reading.
Is there an energy “problem”?
All sources of energy have costs – financial costs, and also environmental costs.
We want to grow our economy, and grow energy use. That requires finding additional sources.
These are clearly energy challenges.
There are only a few things we can do in the future: (1) Use less energy, either via:
• less consumption or • higher efficiency
(2) Find more sources of energy
Sources of energy in the U.S.
Fossil fuels have two big problems:
(1) They are non-renewable, so eventually (but hard to predict exactly when…) we will run out.
(2) They are thought to contribute to potentially
devastating climate change and other environmental
degradation (e.g. from fracking).
Sources of energy in the U.S.
Fossil fuels have two big problems:
(1) They are non-renewable, so eventually (but hard to predict exactly when…) we will run out.
(2) They are thought to contribute to potentially
devastating climate change and other environmental
degradation (e.g. from fracking).
Sources of energy in the U.S.
There is a lot of promise from many renewable energy
sources, but none come without drawbacks.
There is no “silver bullet” solution that would provide easy, abundant, cheap energy
with no cost to the environment or pocketbooks.
There are only a few things we can do in the future: (1) Use less energy, either via:
• less consumption or • higher efficiency
(2) Find more sources of energy
There are only a few things we can do in the future: (1) Use less energy, either via:
• less consumption or • higher efficiency
(2) Find more sources of energy
Focus today on this
question
Let’s think about efficiency: What is the scope to “lose” less energy?
Most of the energy we “produce” is “lost”! (these are in quotes because remember we don’t make or lose
energy, we just transform it… but we can lose the energy from the forms that are useful to us)
Efficiency = Useful energy output/Total energy input
If we increase the efficiency of our energy use we can achieve: • less pollution/environmental damage
• more socioeconomic/sociopolitical “energy security” • increased potential for future economic growth
But how much can we do this, realistically? And what are the best ways to do it?
Efficiency of some common devices
Efficiency = Useful energy output/Total energy input
DEVICE EFFICIENCY (%) Electric motor 90 Home oil furnace 65 Steam boiler at power plant 89 Thermal power plant 36 Gasoline auto engine 25 Light bulb (incandescent) 5 Light bulb (fluorescent) 20
Overall system efficiency
Consider a power plant
There is a boiler, a turbine, and a generator
System efficiency esystem = eboiler x eturbine x egenerator e = 0.88 x 0.41 x 0.97 E = 0.35 or 35%
This should be the same as esystem = electrical energy output/chemical energy input
The efficiency of a system is equal to the product of efficiencies of the individual devices (sub-systems)
System efficiency of a light bulb
STEP STEP EFFICIENCY %
CUMULATIVE EFFICIENCY %
Extraction of coal 96 96 Transportation of coal 98 94 Electricity generation 38 36 Transportation of electricity
91 33
Lighting Light bulb (incandescent)
5 1.7
Light bulb (fluorescent)
20 6.6
So, in absolute terms (i.e. in terms of the total amount of energy), increases in efficiency of energy use (e.g., more efficient light
bulbs) save more energy that expected from the final step alone.
System efficiency of an automobile
STEP STEP EFFICIENCY % CUMULATIVE EFFICIENCY %
Crude oil extraction 96 96 Crude oil refining 87 84 Transportation of gasoline
97 81
Combustion engine (chemical to thermal to mechanical)
25 20
Transmission 50 10 Rolling efficiency on the road
20 6.6
Limits to increasing efficiency Typically, most energy is lost in one or two key transformations for
example in the cases on the last two slides:
-- generating electricity at a power station (38% efficient) -- internal combustion engine in a car (25% efficient)
2nd Law of Thermodynamics – we always “lose” energy during conversion from one form to another, and these losses are
governed by basic physics (e.g., efficiency of heat engines that produce most of our electricity)
These physical laws cannot be escaped and mean that small steps to improve efficiency can make a meaningful difference to
total energy demand, but they can only go so far. So efficiency can only go so far to sustaining future energy (and
economic) growth.
If there is only so much we can do to increase the energy system efficiency, what is the scope for reducing future energy demand
by using less energy?
Could potentially achieve the same goals as increasing efficiency: • less pollution/environmental damage
• more socioeconomic/sociopolitical “energy security” • increased potential for future economic growth (if we can
deliver the same economic services for less energy)
How could be reduce our energy use? First, we need to understand a bit more about our uses of energy.
What about changing patterns of energy consumption
19
You are going to measure your personal electricity use in your take home lab next week.
Let’s think about how your electricity use “adds up” to your total energy “footprint,” in the context of “your” other energy uses
Energy footprint: the total amount of energy used by you (or another person or organization) for all purposes
Measuring your use of electricity
A highly recommended resource: David Mackay’s Sustainable Energy Without the Hot Air
Tally of typical electricity use: • Microwave (1000 W) 12 mins (0.2 hr) =
0.2 kWh • Clothes washer (300 W) for 1 hour =
0.3 kWh • Clothes dryer (5000 W) for 1 hour =
5 kWh • TV & DVD (200 W) for 2 hour =
0.4 kWh • Desktop computer (100 W) on all day =
2.4 kWh • Refrigerator (average 75 W) on all day =
1.8 kWh • Lights (total 400 W) for 5 hours =
2 kWh Total: 12.1 kWh – think about this once you measure your own use… (note this would cost about $1.50/day at $0.13 per kWh)
A typical day of energy use in the U.S. …
Courtesy of Tom Murphy, UCSD
Tally of typical electricity use: • Microwave (1000 W) 12 mins (0.2 hr) =
0.2 kWh • Clothes washer (300 W) for 1 hour =
0.3 kWh • Clothes dryer (5000 W) for 1 hour =
5 kWh • TV & DVD (200 W) for 2 hour =
0.4 kWh • Desktop computer (100 W) on all day =
2.4 kWh • Refrigerator (average 75 W) on all day =
1.8 kWh • Lights (total 400 W) for 5 hours =
2 kWh Total: 12.1 kWh – think about this once you measure your own use… (note this would cost about $1.50/day at $0.13 per kWh)
A typical day of energy use in the U.S. …
Courtesy of Tom Murphy, UCSD
Add other energy use:
• 12.1 kWh/day of electricity • 26 kWh/day of natural gas for
heating • 10 gallons of gasoline every 2
weeks ® 26 kWh/day
Note that heating and transportation are the larger items here…
Total is 64 kWh/day = 2580 W, or 1300 W per person for a 20 person household
US energy services ~ 41.7 Quads per year ~ 122 x 1011 kWh/year
US population ~ 319 x 106 people
Energy use per person ~ 38000 kWh/year ~ 105 kWh/day
Compare to “personal” estimate of 64 kWh/day
Where is the “extra” energy we use?
So what about the rest of our energy use?
From David Mackay, “Sustainable Energy – without the hot air” http://www.withouthotair.com
Here (on the left side of this diagram, in red) is the wider breakdown of the energy footprint in a typical western economy: including uses in the home, but also the indirect uses of energy (e.g. embodied in products we buy, or food we consume)
(on the right side of this diagram, in green, Mackay has summarized his best estimates for how much energy we might optimistically hope to get from different renewable energy sources…)
An overview of how we use energy: A more complete view
From David Mackay, “Sustainable Energy – without the hot air” http://www.withouthotair.com
Embodied energy
energy consumed by all of the processes associated with making a product (could be anything from a can of coke to skyscraper), from the mining and processing of natural resources to manufacturing, transport and product delivery
An overview of how we use energy: A more complete view
From David Mackay, “Sustainable Energy – without the hot air” http://www.withouthotair.com
An overview of how we use energy: A more complete view
From David Mackay, “Sustainable Energy – without the hot air” http://www.withouthotair.com
How much of a difference do “gadgets” make?
From David Mackay, “Sustainable Energy – without the hot air”
http://www.withouthotair.com
“Vampires”: devices that draw electricity without serving any good (e.g., television on standby, etc.)
How much of a difference do “gadgets” make?
From David Mackay, “Sustainable Energy – without the hot air” http://www.withouthotair.com
Energy efficiency at home saved Mackay about 2kWh/day, by turning off vampires, using efficient bulbs, etc.
Not negligible, but consider in context of total energy use – or even choice to eat meat, or have a pet!
Tom Murphy tried going a bit further than David Mackay: starting in 2007, he and his wife: – never turned gas furnace/pilot on – shorter showers, with cutoff for soaping up – line-dry clothes – all bulbs compact fluorescent, some LED – diligent about turning off unused lights – bike/walk around neighborhood (and bus to work) – install experimental (small) solar photovoltaic system (off-
grid; battery-based) to run TV & living room
How much difference can home energy use make?
Courtesy of Tom Murphy, UCSD
Courtesy of Tom Murphy, UCSD
• decreased electricity use = 5-10 kWh/day energy use; • not including additional energy saved by not driving and using
less gas for heating
The results of Tom Murphy’s experiment
Courtesy of Tom Murphy, UCSD
• decreased electricity use = 5-10 kWh/day energy use; • not including additional energy saved by not driving and using
less gas for heating
The results of Tom Murphy’s personal experiment
An interesting lesson that our individual actions do “matter.”
But if you want to reduce your energy footprint, it’s worth knowing it is that you do that consumes energy,
so you can take smart action, rather than uneducated and ineffective action.
The bottom line on our energy use
So what are the most energy consuming activities we do on a daily basis?
• Flying • Driving cars and trucks • Home heating, hot water, and air conditioning • The stuff you buy • Eating meat and poultry
Does that mean you should stop doing these? NO! But worth being aware of them and what they require in terms of your own energy use.
From David Mackay, “Sustainable Energy – without the hot air”
http://www.withouthotair.com
What you can do and what it means: Simple actions to reduce your energy use
From David Mackay, “Sustainable Energy – without the hot air” http://www.withouthotair.com
Think about which actions you would be prepared to take – and which do you think should be prioritized – to reduce your energy footprint? Or should we not be worried about reducing energy footprint, and if not, why not?
What you can do and what it means: More serious actions to reduce energy use
Perhaps most importantly: • You can be aware of your own energy use and encourage
others (friends, family, public) to be aware of theirs. • We don’t have to give up our lifestyles… but we should be
having a discussion about energy, since it’s such a central part of our lives and our economy, and it comes with a price!
From David Mackay, “Sustainable Energy – without the hot air”
