Jacob Klimstra, Wärtsilä Power Plants, The Netherlands
In recent years the majority of the countries in the Middle East region have enjoyed exceptional economic growth, and this growth is expected to continue for at least the next 20 years, if not for the foreseeable future. This economic growth has been paralleled by a rapid rise in electricity consumption.
The Middle East has large fossil fuels resources, primarily oil and gas, and traditionally uses these fuels to generate its electricity. However, even countries with ample energy resources need to consider the intrinsic value of these resources and aim to optimize fuel efficiency as much as possible. The link between energy use and wealth is widely recognized, so wasting fuel should be avoided, not least because of its impact on the environment.
With the growing demand for electricity in the Middle East, this sector is by far the largest consumer of fossil fuels in the region and improving efficiency through the optimal use of the fuel will have many beneficial effects.
Electricity intensity in the Middle East
As mentioned above the Middle East has seen strong economic growth, primarily fuelled by fossil fuel exports, in particular oil. However, the economies of individual countries do vary significantly. The gross domestic product (GDP) expressed in purchase power parity (PPP) per capita in $ (value year 2000) is a common indicator of the wealth level of a country.
In Figure 1, the differences in GDP (PPP) per capita across the Middle East region are shown1. Yemen has the lowest GDP (PPP) per capita with $870/capita, while Qatar has the highest at $38 500/capita. The graph also shows the average consumption of electricity per inhabitant and clearly indicates that electricity consumption and GDP are related.
Figure 1: GDP (PPP) and electricity consumption per capita in the countries of the Middle East, 2005
Further analysis shows the relationship between electricity use and GDP (PPP) per capita is close, with a correlation coefficient of 0.87. A correlation coefficient of 1 would indicate a 100 per cent match, but that is not realistic because of differences between countries. The link between electricity consumption and GPD tends to be weaker in poor countries because basic necessities such as food and shelter consume a larger proportion of private income.
In the Middle East region, the average amount of electricity used per unit of GDP, i.e. the electricity intensity of the economy, is close to 0.5 kWh/$. This is almost double that of the European Union. One reason for this relatively high electricity intensity is the climate in the region, where very high temperatures in the summer makes air-conditioning a necessity. Another reason driving consumption is the relatively low price of electricity in many of the richer Middle Eastern countries.
According to the WWF, the average citizen of the United Arab Emirates has an ecological footprint of 12 ha, while the world average is just 2.2 ha/capita. More importantly, an average footprint of 1.8 ha/capita is considered ecologically sustainable2.
According to data from the IEA, the Middle East shows a steady annual increase in total electricity consumption of around 7 per cent, partly fuelled by a growing population that is increasing by around 2 per cent a year.
Interestingly, consumption of electricity is increasing in almost every country in the region the poorer nations, as well as the richer ones. Clearly this is putting enormous pressure on the region’s power sector.
The consumption of electricity in the whole of the Middle East is currently 10 per cent of the region’s total primary energy consumption. However, because of the low efficiency of generation and in the supply of electricity, the power sector ultimately consumes more than 30 per cent of total primary energy supply, and this may well increase in the future.
Less reliance on FOSSIL FUEL exports
The growth in GDP (PPP) per capita in the Middle East, however, is not wholly dependent on revenues from fuel exports. In the United Arab Emirates (UAE), for example, the actual net energy export per capita decreased between 2002 and 2005, yet it experienced strong economic growth within the same period. Similarly, Egypt and Iran, which export little oil, still have economies that are growing. Thus, this supports the notion that the Middle East can create substantial economic growth without relying solely on fuel exports.
Analysis of the global economy shows that services-related activities have a much higher economic yield than industrial activities, while manufacturing revenues tend to be higher than those from commodity exports. Thus, if the major oil exporters reduced the energy intensity of their economies and used the saved fuel for activities in the service and manufacturing industries greater economic growth could ensue. Furthermore, not only would it be better for long-term economic growth, this would also be beneficial from an environmental point-of-view.
Inefficiency and high capital costs
Globally, the net fuel efficiency of electricity supplied by the power sector is around 32 per cent3. The main reasons for this include an aging inefficient power fleet, transmission and distribution losses and more part-load operation by the generators. Part-load operation is required to balance electricity production and demand, as well as for contingency in case a power plant unexpectedly fails.
Figure 2: The dynamics in electricity demand in Abu Dhabi, 2006 Source: ADWEC
Changes in the electricity demand during the day, as well as from season to season, are marked in the Middle East. The region’s maximum consumption is in summer, with the summer peak being twice as high as the winter peak. A similar picture is seen in the daily dynamics. If we take Abu Dhabi as an example, in the summertime peaks occur close to sunset when lighting is needed and people go home and switch on air conditioning and other electrical appliances. While, in the winter period, peaks occur in the morning when people wake up and go to work, as well as in the early evening when people return home.
As a result of these dynamics, the average capacity factor of the generators that are fit to run is 65 per cent. The effective utilization factor including time required for maintenance, repair and unscheduled outage will be between 50-55 per cent, which is typical for the power sector worldwide. The demand dynamics not only cause lower fuel efficiency, but also increase the specific capital costs of the generating equipment. An effective utilization factor of 50 per cent will result in 80 per cent higher capital costs than a utilization factor of 90 per cent.
For baseload generating equipment with good fuel efficiency, longer operating hours compensate a relatively high specific investment and lower fuel costs. However, equipment covering the demand dynamics only runs intermittently, so it needs to be relatively inexpensive but with a fast response to load changes and good part-load efficiency.
Expectations are that growth in the demand for electricity will continue for at least 15 years at around the same rate as now, i.e. 7 per cent per year. This means that a tripling of available peaking power will be needed and local generation could have an important role in helping to achieve this.
Improving the performance of electricity production
The greater application of local electricity generation would be a major step forward in improving the efficiency of the electricity sector in the Middle East. The right equipment for local generation can combine high efficiency at nominal load with good part-load efficiency. Moreover, such units have high ramping-up capabilities resulting in minimum stand-by losses. Furthermore, options for cogeneration such as water heating, absorption chilling and desalination of seawater are feasible. Finally, local generation would reduce investments in electricity transmission and distribution facilities.
Performance aspects of reciprocating engines
Modern reciprocating engines in the power range above 4 MW can have a performance that exceeds the values given for engines in the general literature. The optimum use of turbo-charging in combination with a large cylinder bore is the key.
Turbo-charging increases the power capacity of a given engine block so that the relative effect of friction and auxiliary losses on fuel consumption is lower. A large engine bore ensures that the heat released during combustion will experience a relatively small cool wall area, which minimizes heat losses from the cylinder medium to the coolant. The cylinder process of engines with a large bore is therefore close to adiabatic. Consequently, a modern reciprocating engine can have a fuel efficiency of over 46 per cent, even when its oil and water pumps are directly driven from the engine shaft.
A generator that converts the mechanical energy from the engine shaft into electric energy will also have some losses. These losses arise because of magnetization and bearing friction loss, electric resistance of the wiring, as well as ventilation power. With a possible generator efficiency of 97 per cent, the attainable fuel efficiency of a local electricity-generating unit can approach 45 per cent, which is relatively high for a simple cycle process.
Utilization of the heat present in the engine exhaust can further increase efficiency via a Rankine cycle. It should be noted that a fuel efficiency of 45 per cent already results in 27 per cent less specific fuel consumption than the current average of the power sector.
The fuel efficiency of electricity generation versus generator output is given in Figure 3 for a generator set driven by a 9 MW gas engine. An almost constant fuel efficiency in the power range between 70-100 per cent can be seen, which means that the generating unit can provide about 25 per cent of its output capacity for supply dynamics and contingency reserve without noticeably affecting fuel efficiency. In addition, the flat efficiency curve is of advantage in case of island operation (emergency power or in remote areas). In cases where the heat released by the engine can be used, such as process heat, desalination or absorption cooling, combined fuel efficiencies of over 85 per cent are achievable.
Figure 3: Performance of a 9 MW engine-driven generator installation as a function of power output
Furthermore, reciprocating engines have a fast ramping up in power output. Where steam-based installations can allow an increase of 3 per cent of rated capacity per minute, diesel engines can increase their output from 0 to 100 per cent in about a minute. Gas engines are slightly slower, but modern engines with per-cylinder gas injection can reach close to 70 per cent per minute. Moreover, the time required from start to electricity production is less than ten minutes, where a steam-based plant routinely needs six hours. In addition, frequent starting and stopping does not noticeably affect the maintenance requirement of reciprocating engines. Consequently, generating units driven by reciprocating engines are ideally suited to cover dynamics in demand without penalties in fuel efficiency.
Advantages of multiple units in parallel
Using a large number of engine-driven generators in parallel offers several advantages over a few big central power plants. In the case of a sudden failure of one large generator, significant capacity is lost and the system is likely to experience difficulties in maintaining frequency and voltage within prescribed limits. In contrast, with multiple smaller installations in parallel failure of one unit can easily be compensated by the remaining units.
Examples of such applications can be found in the Middle East at cement plants. In a typical application, a 6000 tonne/day cement plant has an average load of 32 MW. The electric energy is provided by a power plant consisting of six engine-generator sets of 7.6 MW each. Normally, five units are in operation, with one on stand-by or undergoing maintenance. A failure of one of the six units will mean that only 16 per cent of power capacity is lost. This is in contrast to the situation where one large generating unit or a single transmission line covers the demand of the cement plant and failure would result in a full blackout.
Even having one extra large reserve unit in parallel with the same capacity as the large plant, would pose insurmountable problems in case of failure the load step would simply be too high. Moreover, the combined fuel efficiency of the two plants would be low while the capital investment would be high.
The country of Azerbaijan, as an example, has recognized the advantages of power stations based on multiple units in parallel. Currently, a total of six stations consisting of 10 engine-driven generators each are either in operation or under construction. Significant changes in demand, as in case of Abu Dhabi, can easily be accommodated by such systems, just by starting up or shutting down individual units. This is the so-called ‘cascade concept’.
In addition, to solving the dynamics in demand, such modular units are also suitable to cover increasing demand in emerging economies such as Yemen.
1 Key World Energy Statistics, International Energy Agency, Paris, 2007
2 Living Planet Report 2006, World Wildlife Fund, Cambridge UK, 2006
3 On the values of local electricity generation, Work Package 3 Report, EU ELEP project, Contract EIE/04/175/S07.38664, April 24, 2007
The article is based on the paper ‘The benefits of flexible local electricity generation in the Middle East’ presented at POWER-GEN Middle East, 4-6 February 2008 in Manama, Kingdom of Bahrain.