Alternative energy: The term is not usually used as being synonymous with renewable energy; it can denote a wide range of non-fossil power forms and sources, from nuclear to municipal waste combustion, including what are defined as renewable systems.

City: any urbanized area managed and represented by one or several local governments, culturally and communally understood as a city, with specific administrative and political boundaries.

City region: a city region is the general, urbanized, ecological and economic area comprising and surrounding one or several urban nuclei, all or any of which may be defined as city.

Climate-stable practice: the working definition of a city’s climate-stable practice is a practical commitment to lower greenhouse gas emissions by a given target year – for example, the year 2050 – to a level that is proportionally in keeping with a globally sustainable level of emissions.

CO2-e: carbon-dioxide-equivalent; expresses the presence of effective greenhouse gases as an amount that would be required in CO2 to achieve the effect these gases have.

Clean energy: See also Green energy – the term is used in similar ways to denote a wide range of applications, but is generally applied to higher-efficiency, less polluting forms of fossil fuel power, and (particularly misleadingly) even to nuclear power.

Cogeneration: denotes the combined production of electricity and heat in power plants that can supply a single building or an entire neighborhood, business park, hospital or university. Cogeneration can be based on any fuel: traditionally natural gas, coal or wood. It can be powered by solar-thermal steam, biofuel, biogas and through renewable-energy fed hydrogen fuel cells. Cogeneration supports distributed or stand-alone generation and, given adequate management and supply conditions, can be more affordable than grid power.

Differentiated globalization: the deployment of renewable energy technologies on a large scale has the potential to support a time of differentiated globalization (as defined in Droege 1999, 2004), increasingly distinguishing between locally sourced food and basic goods, and the comparably more global, footloose trade in financial and other advanced services.

Embodied energy: here defined as the total energy content of any product or service that led to its making or delivery: the energy required to produce concrete, make hamburgers, grow wheat, finish construction timber or cut hair, produce a TV show or run a cruise line. The total embodied energy of a service or product includes all power inputs required in the final good or service as purchased or consumed: in mining, administration, transport, salaries, insurance or entertainment, for example. Most significant – and implied in this definition – is the amount of embodied fossil, nuclear and other non-renewable energy involved in the entire process.

Energy web or e-web: an expression newly coined for this book, to denote the intelligent networking of dispersed energy producers, consumers and prosumers into an overall urban or regional area network. This concept is related to that of the city as virtual power plant: a city of distributed sources simulating a single large plant by virtue of the combined functioning of numerous small sources and suppliers.

Green energy: This term is often used to express an aspiration of environmental friendliness in energy management. It is applied to all forms of renewable energy but often encompasses also non-renewable or unsustainable sources such as domestic waste incineration. It can also denote energy efficiency measures, high-efficiency natural gas devices, or even lower-carbon versions of coal power – somewhat ‘greener’ and ‘cleaner’ than the burning of high-sulfur coal, for example.

Greenhouse gas (GHG): human activity effected gases that trigger global warming are carbon dioxide  (CO2), methane (CH4), nitrous oxide (N2O) and chlorofluorocarbons, especially CFC–11, HCFC–22 and CF4. The emission levels of the latter three groups are often combined with CO2 and jointly expressed as CO2-e, ie calculated into the equivalent potency of carbon dioxide. The list of standardized anthropogenic emissions used by the Intergovernmental Panel on Climate Change (IPCC) is CO2, CH4, N2O, NOx, CO, NMVOCs, SO2, HFCs, PFCs and SF6.