Transcript 2-ch50182-energy

ENERGY
Energy is the capacity of a system to do work
Energy is always conserved but …
… can be transformed from one form to another
Energy, E (unit: 1 joule = 1 J or N m)
Power, P = dE / dt (unit: 1 watt = 1 J s-1 or 1 W) (where time, t / s)
1 J is about the energy required to raise 100 g (e. g., a mobile phone) vertically 1 m
against Earth’s gravity at sea-level (g =9.81 m s-2)
I W is the power required to do this in 1 s
Many different kinds of energy: kinetic, potential, mass (chemical, electrical,
magnetic, gravitational, thermal, nuclear, ...)
Here we are interested in energy used directly or indirectly by people for heat and
power, and related key issues.
World population 1950-2050
net current growth rate about 9,100 people per hour
6.9 billion now
Economic growth
Increased energy
demand
1 quad = 1 quadrillion Btu = 1015 Btu =1.055  1018 J = 1.055 EJ
528 EJ world energy consumption in 2009
↔ 16.7 TW globally or 2.5 kW per person on average
Peak oil … and coal, gas, uranium
Anthropogenic climate change
Intergovernmental Panel on Climate Change, IPCC (2007)
Energy Policy
enlightened
affordable energy
on demand
UK Energy Policy
UK Energy Policy largely set by Energy White Paper
(2007) and The UK Low Carbon Transition Plan (2009)
Energy Conversion
• Energy cannot be created or
destroyed (first law of
thermodynamics).
Ex
• However energy in one
form Ex (heat, work,
chemical, mass) may be
converted into energy of
another form Ey via suitable
technology.
technology

Ey
Contributions of Process Industries
to Global Environmental Problems
Energy
• Many global
problems arise from
energy use, and
resulting depletion of
raw materials and
increasing emissions.
we are interested in the case
where the product is energy (in
a different form than input)
Raw Materials
Process
Main
product(s)
Co-products
(waste)
World primary energy supply
Sectors
Industry
Domestic
Transport
Services
Scope
• Energy used in sectors: industry,
transport, domestic, services
(agriculture, hospitals, …)
• Consider main energy
conversion technologies.
Fossil Fuels
• coal, oil, gas
• power generation and
transport
• SOx, NOx, VOC, CO,
waste heat
• CO2
• efficient land use
• non-renewable
• sensitive to political
instability?
Nuclear
•
•
•
•
•
•
•
•
fission, fusion
fuel reprocessing
de-commissioning
short/long term
radiation hazard
nuclear arms
no direct CO2 emissions
terrorism
non-renewable
Biomass
•
•
•
•
broadly CO2 neutral
requires large land areas
significant water usage
competes with food
production
• has niche as by-product
of waste disposal
Wind Power
• variable power
available
• can be land or offshore
• moderate area use
• intermediate
technology
• planning?
Water Power
• hydro, wave, tides,
currents
• clean reputation
• low running costs
• can be environmentally
disruptive
• can destroy land
• can arise from political
oppression
• some real technical
challenges
Solar Power
• photovoltaic, passive
solar heating, solar
concentrators
• fairly efficient land
use
• intermittent
• depends on latitude
• some cost issues with
PV
Geothermal Energy
• hot water from
underground reservoirs
or via cold water pumped
from surface
• turbine power or direct
heating
• depends on local geology
• green though
undeveloped technology
World Energy
http://www.iea.org/
UK Energy
http://www.decc.gov.uk/en/content/cms/statistics/
Digest of United
Kingdom Energy
Statistics 2010
(“Dukes”)
UK Energy in
Brief 2010
Energy Forecast (UK)
• central issues are energy
sustainability & security
• remains largely fossil based
throughout 21st century?
• off-shore wind and wave power?
• next generation of nuclear power?
• hydrogen economy??
• effects of global warming may be
discovered the hard way