Functions and Spatial Structures of Local Utility Systems
Hans-Peter Tietz
Functions and Spatial Structures of Local Utility Systems
Local Utility Systems
Spatial relevance of systems
Review of systems
Past Development and Present Structures
Electricity Supply
Function of electricity supply
Spatial structures of electricity supply
Locations for electricity supply
Routes and networks
Heat Supply
Function of heat supply
Spatial structures of gas and district heating supply
Sewage Disposal
Function of sewage disposal
Spatial structures of sewage disposal
Water Supply
Function of water supply
Spatial structures of water supply
Outlook
Abstract:
Common to public infrastructure systems is that they supply populated areas with basic services largely by means of networks (power, heating, water, telecommunications) and dispose of what is no longer needed (sewage, waste). Another commonality is high path-dependency. They differ, however, in technical and operational boundary conditions. The functions and spatial structures of supply and disposal systems are currently undergoing major changes. This raises the question what general interest services local authorities really have to provide in future.
Local Utility Systems
The names of technical infrastructure systems indicate their function: power supply, heat supply, and water supply. They serve settlement areas directly or enable residents to supply themselves with these resources. Sewage, waste water and refuse disposal services rid populated areas of what is not wanted or what must be got rid of for sanitary reasons, or enable the population to do so.
Future utility systems will be strongly determined by existing structures, for past investments are often “sunk costs,” economic costs that have been incurred in the past and whose present or future accrual is mostly irrevocably fixed by past decisions. They can hence be influenced only to a limited degree, both now and in future.
Spatial relevance of systems
Nowadays, it is hardly possible to confine utility systems to the local authority area, that is to say, within the territorial boundaries of a municipal enterprise. The service areas for electricity, heating, and water supply, for sewage and waste disposal with their comprehensive networks have long since outgrown the single local authority, have fetched back customers through suburbanisation, and in the process have expanded far beyond the bounds of the municipality. Especially in serving larger cities, the resources (energy sources, water) and disposal sites (sewage works, tips) are widely distributed within the municipal territory or beyond in neighbouring local authorities, so that special purpose associations have been set up to establish joint, decentralized systems for certain sub-areas or regional, mostly centralized solutions, with several local authorities sharing the burden.
With regional and supra-regional utilities increasingly concentrating on a single field (electricity, gas, district heating, water, sewage), often restricted to a single supply or disposal function, the necessary coordination of such systems and their adaptation to settlement structures have become much more difficult. Strategic expansion planning by sectoral authorities thus proceeds in isolation, and these systems largely escape the purview of municipal planning, especially control by urban planning and urban development planning. Only in local authorities that have been able to retain their municipal multi-utilities does such coordination take place informally. For formal planning, the existing tools have been abandoned or left to sectoral planning agencies.
Review of systems
A look at public utility systems from a common, systematic perspective (see figure 1) shows what they have in common and where they differ.
Technical systems can be distinguished in terms of three functions: conversion, transport, and distribution/collection. There is a distinction in spatial requirements (point, linear, or network infrastructures) and in the temporal aspect between output and need, whose impacts depend on storage capabilities.
With the exception of refuse/waste disposal, transport in all systems is largely line-bound and mostly underground. Characteristic of technical systems is their indivisibility, high investment costs, and path-dependence – as material flows between the sources of raw materials (such as coal) or resources (such as water) and populated areas. The consumers of power, heat, and water, the producers of sewage and waste are located in populated areas (cf. Tietz 2007).
Figure 1: Utility systems, natural resources and settlements
Source: Tietz 2007.
Utility systems therefore constitute a link between natural resources and settlements subject to both ecological and social requirements. Ecological goals include environmental protection, like water quality management, but climate protection objectives are becoming increasingly important owing to the conversion and use of renewable energy for power and heat supply. Among social goals, the notion of Daseinsvorsorge, the equitable provision of essential, general interest services, is particularly important. The aim is to provide equivalent access to utility systems. If this access is denied, as examples from developing countries show, sustainable growth and economic development of the given region is no longer ensured. Supply systems are hence also an important locational factor for a community.
Differences in the temporal and spatial availability of systems, their cost and quality, or even their unavailability create social inequities. The systems receive flows of material that is needed or produced in different places at different times and in differing amounts. Analysis of flows in recent years has, however, shown that the material flow approach alone is inadequate for evaluating the mediatory role between nature and society ascribed to metabolism (cf. Schramm 2006). At the same time, these systems are intended to recycle and recover unconsumed or only partly consumed materials.
It should be noted that the social sciences often use the metabolism metaphor to explain the function of supply and disposal systems in a society. The aim is to help bridge the gap in this field between the natural and social sciences.
Past Development and Present Structures
Before public utility systems existed, cities tended to develop where favourable natural conditions prevailed for supplying the community with energy or drinking water in the immediate vicinity. Major settlements thus arose on important traffic routes or rivers, which allowed fuel to be brought in or water power to be used locally and waste water and refuse to be rapidly disposed of. Outside such locations, in rural areas, settlement was mostly limited by the available capacity for decentralized supply or, in the case of waste disposal, by the self-purification capacity of soils or watercourses. Only when population and settlement density increased, at the latest with industrialisation, did the natural supply and disposal systems of cities come up against their limits. Effluent discharge exceeded the self-cleansing properties of rivers, and downstream river water was no longer always potable.
Communities have often remedied locational deficiencies by investing in infrastructure and have therefore managed to hold their own even where the technical conditions for supply and disposal are otherwise unfavourable. It is hence unlikely that the development of urban settlement has ever been hampered by a lack of technical utility services. On the contrary, the steadily improved endowment with infrastructure systems has been one of many reasons why people and jobs have moved from rural areas into cities. This has not only led to the growth of settlements but has also made it possible progressively to expand technical utility systems (see also Moss et al. 2008).
However, waste disposal was the problem that showed cities the limits to growth in the late 19th century. But since industrialisation brought enormous technical progress in sewage disposal, this danger, which had already manifested itself in major sanitary problems, could be eliminated by investing in the urban infrastructure (see also Frank/Gandy 2006). In the cities, underground waste disposal structures were gradually constructed that survived the devastation of two world wars and whose networks still bring cities competitive advantages thanks to immense investment.
In the second half of the 20th century, the principle of equivalent living conditions in rural areas was among the factors that gave further impetus to infrastructure development. In pursuit of environmental objectives (see above), the comprehensive system of supply and disposal services was extended beyond the cities to a high technical standard. In rural areas with their lower population densities, systems designed for heavily built-up cities were much more costly, and meeting the environmental standards imposed by law raised costs still further. Environmental goals such as resource and climate protection have meanwhile attained the status of societal objectives.
Suburbanisation trends have been another major influence on technical infrastructures. Suburbanisation has meant utility infrastructure lines have had to follow the population into periurban areas, where development is far less dense, and where the provision of public infrastructure is much more expensive. Distributing infrastructure costs for bigger and bigger systems among all users has meant that tariff-paying customers unable to afford the move to “better” residential areas on the outskirts of metropolitan areas have borne the full brunt. Suburbanisation has thus benefited from socially questionable cross-subsidisation (cf. Siedentop 2006).
Decisive for the efficient functioning and cost effectiveness of utility systems is the density of developed areas. Planned, as well as unplanned phenomena like shrinking cities and migration flows beyond the control of planners have a detrimental effect on systems such as district heating particularly sensitive to urban density (cf. Westphal 2008).
In sum, supply and disposal systems today have structures that:
- were created in the late 19th century and which existing rehabilitation and renewal strategies seek to maintain,
- were designed for growing not shrinking communities,
- presuppose public service provision and therefore do not allow for private sector optimisation,
- provide for largely the same standards in sparsely populated rural areas as in far more heavily built-up cities,
- allow for no spatial options for controlling growth, shrinkage, or renewal by distributing expansion costs within historical service areas.
Electricity Supply
The secondary energy electricity is the main energy supplied to households and industry, since it offers the greatest flexibility in spatial distribution for lighting, power, and heating/cooling and the greatest range of uses. Significant facilities in electricity supply are power stations of various sizes (from 0.5 MW small biogas plants to 1,400 MW nuclear power blocks), as well as power lines (high and extra-high voltage transmission by overhead line or underground cable) and networks of different voltages to distribute the electricity within the region and populated areas.
Function of electricity supply
The basic or essential function of electricity supply is to provide developed areas everywhere with light and power. Electricity is not very suitable for space heating – to be dealt with in detail in the next section – because of its low primary energy efficiency. However, declining heat density due to thermal insulation and energy conservation means that it is becoming more and more important in space heating because of comparatively low transport costs, thus stabilising its status as the most important source of energy.
Given the need to ensure economically viable, area-wide provision, also on the periphery of supply areas and in very sparsely populated areas, it could be advantageous in future to supply households outside core areas on a decentralized basis, and also to use local renewable energy sources. The parallel need to supply large industrial consumers at all times where demand often fluctuates strongly, and reliably to maintain voltages and frequencies, means that a centralized, internationally integrated national system will continued to be required. New fields of application are currently increasing the demand for electricity, but the present supply system requires only a few adjustments and new actors to ensure savings and the efficient use of electricity, so that a future comprehensive electricity supply is not fundamentally at risk.
In the environmental field, electricity supply, having successfully adjusted to clean air requirements, now faces a major challenge in adapting to climate protection goals. Emissions trading and legislation giving priority to renewable energies will influence siting and routing at the local, regional, national, and international levels. Since consumers are charged directly in their homes or factories for the electricity they use, market mechanisms introduced by liberalisation and privatisation come to bear in electricity supply.
In the past, municipal electric utilities have played a key role in attracting industries to areas when attractive electricity prices could offer locational advantages, even though this was often at the cost of higher prices for local households. Liberalisation of the electricity market has fundamentally changed conditions. Although the electrical power capacities required can now be procured competitively, supply depends on an efficient and cost-effective electricity grid.
Spatial structures of electricity supply
Spatial structures in the electricity supply system are determined by where fuel is to be obtained and where consumption is concentrated. Apart from developed areas where people live and services and industries are located, this will continue to be the domestic sites of brown coal deposits and, increasingly, areas where renewable energy sources can be tapped. The planned phasing out of nuclear energy, which currently provides up to a quarter of electricity in Germany, will require the greatest adjustments, especially if renewable energies are to make the biggest contribution to replacing it.
Locations for electricity supply
The future role of coal is in dispute, especially because of the size of power station units (ca. 600 MW). About 60 such sites are currently under discussion, of which some 30 are likely to be developed. The reason is that the phasing-out of nuclear power and liberalisation of the market in Germany has attracted many foreign investors as independent electricity producers, thus introducing competition into the German electricity market as desired. Unlike established electricity producers with sites already at their disposal, new market participants must find economically optimal locations. For coal, most sites are in North Germany, where fuel can be delivered in large quantities by water or rail and where cooling water for effective thermal conversion is abundant. In the available locations, using waste heat locally as well as selling it under long-term contract to local authorities or large industrial customers for process or space heating are thus limited options.
Established electricity producers, in contrast, rely entirely on their existing locations. Their vested interests are usually protected, so that the question whether these sites are suitable for further use does not arise. From a spatial or urban planning point of view, or from that of the area concerned, this would be useful (cf. Tietz 2006). But a switch to renewable energy sources, too, requires new, especially decentralized sites, which runs counter to existing development. However land-use planning does hardly anything towards site provision; only in regional planning has a first step been taken with zoning for wind power stations. By specifying sites for cogeneration facilities close to developed areas every time new areas for development are designated, land-use planning could provide additional assistance.
The spatial frame of reference is even stronger when it comes to using domestic biomass like rapeseed oil to generate electricity. In addition to decentralized sites for conversion into electricity, cropland is required, competing with agricultural production or ecological balance functions.
Routes and networks
All these new generating sites considerably influence the German transmission network, as a Federal Network Agency (DENA) study has shown. Networks need to be extended and expanded to transport the power largely produced in North Germany (wind power and coal) southwards to the focal points of consumption, and to substitute most nuclear power stations, whose electricity generation capacities are gradually being reduced. Expansion of transmission network can partly be achieved by scaling up existing routes. In other cases entirely new routes will be needed. The detrimental effects on the physiognomy of the landscape and the feared impact of electromagnetic fields on human health are subjects of debate.
The Lower Saxony government has reacted to the planned North-South expansion with an act on underground cables that requires underground transmission where economically reasonable. Underground cables cost a great deal more than overhead transmission lines. Transmission system operators have opposed this legislation on the grounds that too little experience has been gathered with underground transmission. New high voltage DC transmission lines (HVDC) could ease this situation: they operate with lower losses than the classical alternating current lines. Such systems, which can use either overhead or underground lines, also require new routes, which have yet to be coordinated with the numerous other demands made on open spaces, but which regional planning could keep in reserve.
Great hopes are therefore being placed on decentralized cogeneration. This involves small plants that generate (space) heat on demand in residential buildings, industrial and commercial premises, but which also produce electricity which is fed into the power grid (in the case of power-led CHP, it is heat that is the “by-product,” in heat-led CHP it is electricity). These small, decentralized power plants can be electro-technically interconnected to create “virtual power stations.” One control engineering problem that still has to be solved is how to adjust this input, as well as the uneven inflow of electricity from wind power plants, to fluctuating demand. This makes the storage of electricity a particularly important issue. One idea is to use several million electrical cars plugged in at home for storing electricity by means of intelligent control, thus making them part of the technical infrastructure.
Liberalisation of the market and the now well-established trade in electricity has given rise to another need for expanded electric power grids. There are times when the demand for hydroelectric power, for example in South Germany, is great but can be satisfied only from Norway; at other times it is attractive to deliver wind energy from North Germany to Scandinavia. This requires new power transmission lines, for instance between Norway and Germany.
Heat Supply
Heat supply is not necessarily a task for local authorities, since the space heat needed in homes and the process heat required by industry can also be produced individually by individual installations using off-grid energy sources (wood, coal, oil, liquid gas), or decentralized sources of energy that cannot yet be exploited economically by centralized systems. The necessary expansion of small, local district heating networks, for example, constructed in developed areas by housing companies, as well as the small-scale expansion of the gas grid for space heat supply will make this field of supply particularly important for local authorities in the years to come.
Function of heat supply
Network heat supply systems in built-up areas often use natural gas, which is either transported directly to individual furnaces in buildings or converted into district or local heat in heating plants. This type of network heat supply with water as a transport medium often uses waste heat from electricity generation (cogeneration) or generates heat energy in heating plants with the primary energy source coal, and increasingly with renewable energy sources (wood pellets, straw, etc.). In supplying populated areas with heat, the network systems compete with off-grid systems using various energy sources (oil, coal, biomass) that strongly limit the potential of network supply on the heating market.
Competition on the heat market is currently marked by coupled pricing for oil and natural gas and declining heat densities. This has been caused by lower demand for heating in new buildings, a consequence not least of building regulations introduced since 1995, and in the existing building stock owing to thermal insulation and new windows installed during rehabilitation and renovation. Lower heat densities have meant higher specific distribution costs for network heat supply systems. They have to be compensated through concentration or expansion on the outskirts of developed supply areas.
Spatial structures of gas and district heating supply
Heat distribution networks differ in location, type, and number of entry points. If heat from a major power station far from the city is used, it is mostly available in line with electricity production throughout the year. This means firstly that, where possible, one or more heat storage systems are integrated into the system and secondly that a heating plant (close to the consumer) is available to cover peak demand (see also discussion of the annual heat demand line). Such heat distribution systems mostly include both transport lines and distribution lines with a transfer station between these two components. A network often consists of several sub-networks, some of which have been developed separately (the term used is “island networks”), to be subsequently linked up to form an overall system.
Smaller heat supply systems with cogeneration plants can often be adapted more strongly in size to the demand for heating. However, heat storage is advisable in this case to adjust to the seasonal demand for heat. Demand peaks are covered in this case, too, by a heating plant component or a modular structure of heat supply units (“blocks”). The systems then usually include no transport lines, only sub-distribution lines. Sometimes a medium distribution level is introduced with bigger line cross-sections.
District heating supply networks need not necessarily cover a developed area in its entirety. It is possible to limit coverage to consumers who can be connected at the lowest cost for line provision. Unlike district heating, gas can provide homes not only with space heating but also with energy for cooking.
Since supplying gas involves far lower line costs for both long-distance transport and distribution in populated areas (lower building costs and transport losses), gas supply can be very flexibly adapted to demand and settlement structure. Less dense supply areas can hence also be economically served. The municipal gas supply developed from the provision of town gas mostly produced within the city, but supply is meanwhile firmly in the hands of regional and national gas suppliers. In recent decades, they have invested heavily in a gas supply grid, enabling homes to be supplied almost throughout the country. Only the use of natural gas for large-scale electricity generation (e.g., combined-cycle power plants) has required the grid to be expanded.
Where renewable raw materials, local renewable energy sources are to be used, the focus is more on heat supply, for a certain level of storage is possible (storage of wooden chips and pellets, storing biogas or feeding it into the existing natural gas network).
Siting heat supply depends much more than electricity supply on the cost of transporting the converted energy to the consumer. From a favourable location for generating electricity (ease of fuel delivery and adequate cooling water) electricity can usually be transmitted at reasonable cost to consumers in existing networks. The parallel use of waste heat from such sites is, in contrast, mostly very expensive, because the district heating lines required are expensive to build and distribution losses are considerable. For reasons of environmental protection, these sites are, moreover, usually remote from developed areas. Process heat (e.g., for paper mills or refineries) has so far been generated on demand largely without consideration of the spatial dimension, and thus without envisaging combining the production of electricity and heat.
Sewage Disposal
Sewage and waste water disposal for homes, industry, and power stations serves primarily to safeguard environmental health in developed areas and to maintain and improve the quality of waters. There are subsystems for the disposal of waste water or sewage and rainwater (storm water). In the case of sewage disposal, the focus is on increasing the connection rate by extending the catchment areas of existing sewage treatment plants; on supplementing existing systems with smaller, decentralized plants to enhance capacity; on complementing systems through further (e.g., chemical) steps; and on expanding and organisation sewage sludge disposal. One major challenge in the years to come will be to adapt present systems in quality and quantity to changing demographic conditions in the service areas.
Function of sewage disposal
Waste water disposal depends very strongly on spatial conditions, because for health reasons sewage has to be kept as remote as possible from populated areas, but for energy conservation reasons the process needs the aid of gravity. This means that effluent in the sewerage system should flow downhill and discharged as directly as possible into the receiving watercourse. Sewage disposal system in developed areas must therefore be designed to operate as inexpensively as possible.
For this reason, collector sewers led out of the city, mostly downhill towards the next watercourse, which received the effluent, leaving cleansing to the self-purification capacity of the running water. The growing sewage load made it necessary, however, to treat the water before discharging it. Initially, sewage was treated mechanically, later biological treatment and finally chemical treatment were introduced. Sewage treatment plants steadily grew, and the sewage collected caused an odour nuisance, so that these plants finally had to be sited as far as possible out of town but nevertheless on collector sewers before the lines fed into the receiving watercourse. This means that there is practically no leeway for regulating the siting of sewage treatment facilities (such plants are therefore privileged in undesignated outlying areas under building permission law).
What can be regulated, however, is the size of sub-systems and the site of discharge into a watercourse. This need not always be the nearest big river; the job can also be done by groundwater if the residual pollution of the treated waste water is low or if it is rainwater, which is less polluted to start with.
The societal and political goal is still to continue increasing the connection rate in developed areas, now on environmental protection grounds rather than for sanitary reasons. Furthermore, the sewage disposal system can be controlled in terms of size and catchment area. Both population density, topography, and economies of scale in the transport and treatment of large volumes of waste water play a role. Here, too, settlement structure largely determines what system is best suited from a spatial planning point of view.
Spatial structures of sewage disposal
In the field of sewage disposal, technical developments have made it possible to attain the desired effluent values independently of the size of the system, providing more leeway in deciding on sites and size of treatment facilities. The basic decision between centralized and decentralized sewage disposal systems must take account not only of the spatial structure of developed areas (density, location of recipient watercourses, site potential) but also individual costs in the local setting.
However, when considering alternative systems, the established cost comparison method frequently used in sewage management comes up against its limits, since it takes account only of elements that can be assessed in monetary terms for fixed depreciation periods. A comparative cost estimate for short periods discourages opting for solutions that are more cost effective in the long run. Particularly for alternative sanitation concepts, a comparison of costs is favourable in proportion to the length of the projected period. Studies to date on the comparison of costs between conventional and alternative sanitation concepts show that the new concepts can be not only ecologically but also economically advantageous (cf. Peter-Fröhlich et al. 2006).
Water Supply
Water supply has two main tasks: to provide drinking water for private households and process water mainly to industrial enterprises and power stations for cooling purposes. Spatially relevant elements of the water supply system include facilities for spring water and groundwater extraction together with water protection areas, drinking water dams, and water treatment plants (waterworks) and storage facilities (elevated reservoirs, dams). Hygienic considerations have to be taken into account in planning. Where possible, process water systems should in future reduce their consumption of drinking water.
Function of water supply
Besides directly using rainwater, households in Germany have numerous groundwater and surface water resources at their disposition. The amount of rainwater available is determined by local precipitation, plot area per user, and the quality of the water. If rainwater is not potable, it has to be treated. This is expensive in small units and proper handling is difficult to supervise. As a rule, the plot area available in heavily built-up urban areas is insufficient despite abundant rainfall throughout the country. In the spatial distribution of groundwater and surface water, there are clearly identifiable water scarcity areas and water resource areas.
The development of settlement over the past 150 years has hardly been affected by any lack of drinking water resources. Where it was considered advisable for urban or regional planning purposes or for strategic reasons to zone land for development, to extend developed areas, or to set up industrial and commercial estates, the water sector has always managed to provide the necessary resources. Not even areas where a well-developed system of long distance water supply has been established (Ruhr District, Frankfurt, Stuttgart) have suffered from shortages. Economic considerations have usually played a role in such cases, which made delivery even from far distant areas appear less expensive than treating local surface water.
Spatial structures of water supply
Public water supply is still organised on a decentralized basis. In Germany there are currently more than 6,000 enterprises, most of which extract water themselves. There are four main types of organisation: (1) operations run by local authorities in the context of general municipal administration (direct service organisation); (2) local authority operations that are separate accounting entities (semi-autonomous municipal agency); (3) private firms owned by the municipality (municipal enterprise); (4) private firms commissioned to operate facilities with responsibility for performance remaining with the municipality (operator model).
The most important issue in adapting network infrastructures to future needs is whether to retain centralized supply and disposal facilities, adapting networks accordingly, or whether networks and facilities should be decentralized in the interests of adaptability, albeit it at the cost of economies of scale. A blanket preference for a single strategy is not possible.
The potential for decentralization in water supply systems differs from that in waste water disposal systems. In water supply, a drop in consumption causes problems that are easier to cope with than changes in sewage volume. The pressure for change is accordingly not so strong. In many places, a decentralized water supply fails because of inadequate water resources and poses safety problems due to the difficulty of monitoring and controlling a multitude of small plants. Since drinking water is a foodstuff, it is subject to high quality standards, and comprehensive quality control must be ensured. The risk of failure for distributed facilities in water supply must be judged differently from that in sewage disposal. Centralized and decentralized alternatives in water supply systems can therefore not be considered of equal utility.
Outlook
The functions and spatial structures of utility systems are currently undergoing major changes. New organisational arrangements such as liberalisation and privatisation are changing the market situation, and new systems of regulation and market incentives are influencing developments. New actors on the market have brought more competition but also additional boundary conditions that planners have to take into account. Similarly, new technical developments, involving both new plant and equipment and new control technologies, offer solutions that recoup spatial and temporal shifts between supply and demand.
The functions of traditional supply and disposal systems will remain. But which essential services local authorities must provide in future and which can be assumed by consumers (electricity, heat, water) or producers (sewage, refuse) needs to be examined. The question of spatial availability must also be broached. Must every (remote) place be equally endowed with utility services or can limits be introduced in the interests of resource conservation, leaving the affected parties to assume responsibility for supply and disposal? Finally, the question of tariff equity will become increasingly urgent as the users of old, depreciated systems have to contribute to the redevelopment of built-up areas without funding being made available to rehabilitate or conserve the value of their systems.
At present, a working group at the Academy for Spatial Research and Regional Planning (ARL) is examining the need for action in spatial planning in the field of local supply and disposal systems (cf. Tietz/Hühner forthcoming); their findings will provide a comprehensive contribution to the topic discussed in this article.
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