-»—SEC of new Stock o SEC of depreciated Stock -Expon. (SEC of Average Stock)

■ SEC of Average Stock

---Linear (SEC of depreciated Stock)

Figure 21.2 Average specific electricity consumption (SEC) (expressed as kWh per tonne of liquid steel) for average, retired, and new stock (Worrell and Biermans 2005).

Measuring Sustainability

To understand the sustainability of the energy system, it is essential to understand the way that energy is used as well as how energy use and services provide change over time. This requires a detailed understanding of energy consumption and efficiency levels, for which we currently lack a consistent way to measure and collect data. Energy represents, however, an area of study where relatively abundant data has been collected since the first oil shocks in the 1970s, certainly compared to the other themes discussed in this volume. However, most detailed data collection has focused on supply and less on demand. As discussed above, we do not have good estimates of the total recoverable reserves of other heavily studied energy sources, such as oil and natural gas.

For a more consistent analysis of the sustainability of the energy system, we need to improve available measures and data on the flows of energy carriers, as well as energy service and efficiency levels. Since the dynamics of energy demand are the key driver for changes in the supply system, we also need to understand how the demand for energy services develops:

• Which energy services are provided, and what is the activity level of each service?

• Can we device a basket to measure and compare energy service levels between economies and over time?

• What are the distribution, level, and dynamics of the mix of energy services over time?

• What is the efficiency with which energy services are provided, and what is the remaining potential for energy savings for (key) energy services?

Once we have developed a better understanding of the dynamics of energy (services), demand makes it then possible to evaluate the impact of such patterns on the flows of energy carriers and the impacts of this use:

• What are the total emissions to the environment?

• What is the distribution of supply over various primary energy sources, including renewable and nonrenewable energy sources as needs for non-renewable materials, water, and available land?

• What is the distribution of final energy carriers (e.g., power, fuels), and how will this change as a result of changes in energy services?

• What is the total remaining stock or accessibility ofprimary energy sources (expressed as volume, flow over time, or time needed to rebuild stock)?

• What are the total costs of production of the energy carriers and provision of energy service?

In the end, environmental, social (i.e., distribution and access to energy services), and economic sustainability (i.e., costs per unit of energy service provided) are key factors needed to determine the sustainability of the energy system. The first steps and studies have been done to assess the total costs of energy service provision. These tend to show that, even without full accounting of all externalities, an energy-efficient supply of energy services is not only environmentally more sustainable, but also economically and socially sustainable.


While energy is a key issue in determining the sustainability of society, society still lacks reliable data with which to measure the sustainability of supply and demand. Understanding energy use, conversion, and supply is a key issue in the transformation of society to more sustainable production and consumption patterns, as energy use patterns are primary factors in climate change, (air) pollution and depletion of nonrenewable resources. Measuring the sustainability of energy use has many aspects that are closely interrelated: production, conversion, supply, price, and efficiency. These relationships change over time, moving and removing the boundaries of the energy system and its sustainability.

The economy is a basket of activities or energy services (i.e., the ultimate service provided by the energy-using device). The economy itself is not interested in using energy, but rather in providing energy services at the lowest cost. Hence, sustainable use of energy means the provision of these services at the highest possible level of energy efficiency. Changes in energy service demand have altered the way society supplies energy, and will do so in the future, making a sustainable provision of energy services of paramount importance to a future sustainable energy system. As stated, reliable data is lacking with which to measure the sustainability of demand. Our understanding of (future) demand, technology and potential impacts is limited. This hinders our ability to quantify, accurately and consistently, the sustainability with which society uses energy. In addition, our lack of an understanding of the remaining reserves and the interaction with the economics of recovery makes it difficult for us to measure the potential for depletion.

Overleaf (left to right, top to bottom):

Jack Johnston, Steve Rayner

Ernst Worrell, Don Gautier, Trevor Demayo

Group discussion, Joan Ogden

Mark Delucchi, David Greene, Andreas Loschel

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