Because there are so many issues that relate to how a city obtains or uses energy – including land use and mobility policies and practices, waste management collection and disposal practices, and the type and level of local economic activity – urban energy systems can be defined in either broad or narrow terms. Issues such as transportation and land use are taken up in other topics of this assessment report, as they are significant enough to warrant detailed attention. Other topics by necessity fall outside the scope of this report given limited time and resources. For the purposes of this topic, however, the analysis will focus on electricity and thermal energy supply and distribution systems, as these link to the bulk of the energy used in most cities.
System overview
"Centralized" electricity systems are commonplace in cities, involving large power plants generating power which is then distributed to users through a complex web of high- and low-voltage wires crossing a city. Centralized generation takes advantage of the economies of scale offered by large power plants, which can be fueled by a variety of different sources, including coal, natural gas, biomass, solid waste, or nuclear fuels. Even large renewable energy systems, including large wind farms, geothermal power plants, or concentrating solar "power towers" can be sized at scales equivalent to "traditional" power plants, allowing them to fit relatively easy into the central generation and distribution model.
Power plants linked to this system can be located either within a city’s borders or at locations quite remote from the urban core. Locations within cities have proven less desirable in many locales because of concerns over the emissions from these plants, creating public health concerns and dampening real estate values in adjacent neighborhoods (Farber, 1998; Abt Associates et al., 2000). The advent of comprehensive state, national, or trans-national grids has allowed many cities to increasingly rely on out-of-city power sources, lessening the severity of the problem and the political challenges associated with siting new in-city power plants; although the siting of transmission lines has become problematic in many locations as well.
"Distributed" forms of power generation and distribution (also known as DG) refer to systems with much smaller power production units that are located at or near the point of energy use. DG systems enjoy certain advantages, such as the fact that because they link directly to the electric wiring system within the host building, they tend to suffer from less "transmission loss." These losses occur due to Joule heating of power lines and when electricity voltage levels are "stepped" up or down at different points in the transmission and distribution network (Lovins et al., 2002). DG systems may also allow a building or user to avoid certain design or service deficiencies involving the city-wide distribution grid, such as poor power "quality" or vulnerability to blackouts or other types of service disruptions (Lovins et al., 2002). Finally, DG systems may allow buildings to utilize certain types of power more easily or cheaply, such as electricity generated from renewable sources such as wind or solar power or technologies such as combined heat and power (CHP) units that enjoy high rates of energy efficiency.
Thermal energy use in cities - that is, energy used for space, water, or process heating or cooling – can also be produced in a centralized or decentralized manner. Centralized (or "district") thermal energy systems, tend to be more common in cities with extreme temperatures in winter or summer months. For cost or pollution reasons, local authorities and/or utilities in many cities have found there are benefits to producing steam or hot (or cold) water centrally, and then distributing this thermal energy to users via a network of underground pipes (see Table 4.1). Because of the cost of installing and maintaining the pipeline network, some minimum population density or level of demand is necessary to make these systems cost effective (Gochenour, 2001). District heating and cooling systems can be fueled by a range of energy sources, such as coal, natural gas, biomass, nuclear power, and geothermal sources. In some cases, the plants producing the thermal energy may operate as co-generation facilities, simultaneously producing electricity for use around the city.
The alternatives to district thermal systems are building-based thermal technologies such as gas-powered stoves, boilers, furnaces, or ground source heat pumps. Some buildings employ combined heat and power technology, satisfying some or all of the building’s thermal and electricity needs.
Although decentralized in function, building-sited thermal systems may nonetheless involve linkages to citywide fuel networks delivering natural gas or coal gas around a city. Building-sited thermal systems may also rely on fuel oil or liquid petroleum gas tanks located within the building that are refilled on an as-needed basis. Other buildings or homes rely on supplies of solid energy feed stocks, such as coal, kerosene, charcoal, biomass, or animal dung, which are burned in a boiler or cookstove to produce space or process heat. These latter systems may involve some type of formal supply chain, or less formal scavenging processes involving the building owner or dwelling occupant. In developing countries, these supply chains can create important opportunities for local economic development (Clancy et al., 2008).
The thermal systems employed may have significant health impacts within or near the home, because of differing levels of smoke or other pollutants emitted while operational. Households in cities in developing countries are far more reliant on solid fuels for cooking than urban dwellers in developed countries (UNDP/WHO, 2009; see Figure 4.1) This is testament to both differing levels of energy infrastructure in these cities, the price of the different fuels, and difficulties obtaining interconnections to formal distribution networks (Dhingra et al., 2008, Fall et al., 2008).
A corollary to the thermal system discussion is the fact that, in many cities around the world, there may be heavy reliance on electric heating and cooling systems. Electric air conditioners are well-known features in many homes and businesses in warmer climates, but – especially in cities with historically cheap electricity sources such as nuclear or hydropower – there were many decades during the twentieth century when electric space heating, water heating, or cooking systems were aggressively promoted as preferred technologies (Hannah, 1979; Platt, 1991; Nye, 2001).
Table 4.1: Selected urban district energy systems.
|
City |
Thermal application |
Approx. energy production (GWh/yr) |
Number of people served |
Number of buildings served |
Percentage of district served |
Use co-generation? |
Fuel Sources |
|
Copenhagen, Denmark |
Space heating |
5,400 |
500,000 |
31,300 |
98% |
Yes |
Coal, natural gas, biomass |
|
Seoul, South Korea |
Space heating and cooling |
10,600 |
>1,000,000 |
N/A |
25% |
Yes |
Natural gas, oil, landfill gas |
|
Austin, USA |
Space heating and cooling |
350 |
75,000 |
200 |
100% |
Yes |
Natural gas |
|
Goteborg, Sweden |
Space heating and cooling |
4,000 |
300,000 |
N/A |
64% |
Yes |
Natural gas, biomass, biogas |
|
New York City, USA |
Space heating and cooling |
7,600 |
N/A |
1,800 |
<10% |
Yes |
Natural gas, oil |
|
Paris, France |
Space heating |
5,000 |
N/A |
5,774 |
N/A |
Yes |
Natural gas, biomass, coal, oil |
Figure 4.1: Share of urban population relying on different cooking fuels.
Electric thermal systems remain popular in homes in many cities around the world, because of lack of access to gas supply lines or because builders did not want to incur the cost of installing the necessary feeder pipes.
Climatic conditions and the local economic base also figure decisively in local energy technology choices and usage levels. In China, for example, the colder and more heavily industrialized west has vastly different energy needs than the warmer and more service sector-focused coastal cities in the east and southeast (Dhakal, 2009). The "new" cities of coastal China also tend to have more modern buildings that are home to wealthier families, both of which contribute to different types of energy usage patterns (Chen et al., 2010).
These technology and fuel choices made years ago in cities create a path dependency that shapes current climate change mitigation and adaptation policymaking efforts. The embedded system assets – the massive technology investments in power plants and pipes and wires – are costly to replace or upgrade, and they may provide energy to homes and businesses at a market price lower than newer, more "climate friendly" technologies (Unruh 2000, 2002). This raises important questions for local authorities about how aggressively to promote new technology adoption, including whether existing system assets should be replaced before the end of their useful life. In cities in less-developed countries, the question may focus on whether more advanced energy systems can be cost effectively deployed as part of the overall infrastructure system development efforts sought in these cities.
Energy market structure
"Modern" energy systems1 involving gas and electricity supply chains were eventually recognized as operating most efficiently as natural monopolies, reducing the need for redundant gas and electricity supply lines across a city (Hannah, 1979; Platt, 1991). In some cases, monopoly rights were expanded vertically with a single entity holding responsibility for both the supply and distribution of energy around some or all of a city. Ownership responsibilities for these system assets were largely dictated by state or national market regulatory preferences, with different assets owned and operated by either government, private firms, or some type of public-private partnership. Government ownership can take the form of nationalized utilities or municipally owned utilities, where local government has direct control over the management and operations of the local energy system.
In the 1980s and 1990s, when energy market liberalization efforts took off around the world, some cities began to see significant changes in who owned and operated these systems. In many cases, ownership responsibilities became more fragmented, with supply and distribution responsibilities broken apart in the name of competition and economic efficiency.
In cities with large informal settlements with less comprehensive or technically advanced energy system infrastructures, market structures may look very different. Many households are unable to afford clean-fuel cookstoves or appliances (UNDP/ WHO, 2009); households may also be unaware of the ill effects caused by pollution from certain types of solid fuels (Viswa-nathan and Kavi Kumar, 2005). Supply chains may therefore focus on delivering fuels that can be used in very low-tech ways, satisfying heating and cooking needs. Developing country cities may also experience high levels of utility "theft," with homes and businesses illegally (and dangerously) tapping into local electricity distribution systems (USAID, 2004).
These different energy market circumstances all make addressing the issue of climate change a challenging one, as responsibilities for energy system planning – and payment for any system upgrades – may be divided among a very diffuse set of stakeholders.
Energy system governance
Technology choices, market structures, and ownership responsibilities are all important considerations as we look towards a future involving changing climatic conditions. The ability of cities to influence the design or operation of the local energy system varies widely.
In analyzing energy governance in cities, span of control (also known as agency or policy competency) is the critical factor. Span of control refers to the fact that energy policy is traditionally considered a supra-local issue, controlled at the state/provincial, national, or trans-national level (Bulkeley and Betsill, 2002). This is a reversal of the situation in the mid to late 1800s, the era when gas and electricity use first became prominent in cities. At that time, electricity and gas utilities were frequently under local authority control, a function of the technology in use at the time. Over time, however, as local networks were linked into ever-larger systems serving entire states or countries and concerns arose over corrupt local oversight practices, regulatory oversight for these systems was transferred to state/provincial or central government agencies (Hughes, 1983).
As markets for certain forms of energy became global, and as energy-related pollution or other externalities crossed country boundaries, international agreements or treaties shifted certain policy control powers yet again, to trans-national organizations such as the European Union or United Nations (Bulkeley and Betsill, 2002).
Today, we are increasingly seeing a re-engagement on energy policy matters by local authorities in both developed and developing countries (Keirstead and Schulz, 2010). Capello et al. (1999) note that the focus is on land use planning and building regulations, energy conservation policies, market or behavioral stimulation programs (e.g., grants and information campaigns), and support for technical innovations. Cities also have significant control over energy use in local authority-owned buildings and in the type of energy or technology used in publicly managed services such as mass transit, waste disposal or treatment, and water supply systems.
Because key regulatory control powers still reside at the state or national level, however, most local authorities lack the ability to force fundamental changes in the technologies that utilities employ or their efforts promoting energy conservation or efficiency. Energy or carbon taxing powers also tend to be within the prerogative of national governments, and their availability locally varies significantly from city to city (for example, see European Commission, 2007b).
Other policy options may be unavailable to cities owing to the high costs of entry, such as funding for major research and development projects. Some areas where cities can act, such as planning and building codes, may be constrained by institutional capacity. An innovation such as the Merton Rule,2 which promotes the increased use of renewables in buildings in London (House of Commons, 2007), requires adequately trained officials for plan approval and enforcement. Building codes exhibit this principle more generally; municipal governments in developing countries can often influence energy use through building codes, but the effectiveness of these measures is highly variable, depending on the resources available for application and enforcement. In China, enforcement of local buildings codes varies across cities and across different stages of design and construction (Shui et al., 2009).
