Pictures of the Future    Spring 2007

How Cities Can Save a Fortune

Anyone familiar with the Intergovernmental Panel on Climate Change report presented in February 2007 (see Facts and Forecasts) can no longer seriously doubt that climate change is a reality. It’s clear that burning fossil fuels such as gas, coal, and oil is a major cause of the greenhouse effect. So how can we turn things around? What would happen if we began using the most modern and energy-efficient technologies available for cars, power plants and household appliances? If we could start from scratch—how much energy would a hypothetical city with a population of ten million people require? It makes sense to think through such a scenario. It turns out that a comparison with a conventional city in industrialized countries leads to some surprising results…

Consider the figures for Germany, for instance, which is the sixth-biggest energy consumer after the U.S., China, Russia, Japan and India. The country currently consumes a little more than 14,200 PJ of primary energy per year (1 PJ equals 10¹⁵ J, one quadrillion joules). Germany has a population of 82 million, which means that a hypothetical city of ten million would consume around 1,750 PJ of primary energy. Generating this energy with hard coal would require 60 mill. t per year—enough to form a mountain nearly 30 m high, 1 km long and 1.5 km wide. In reality, the German energy mix consists of 36 % petroleum, 23 % natural gas, 13 % hard coal, 12 % brown coal, 12 % nuclear power and around 5 % power from water, wind, solar, biomass, geothermal and other sources. Converting this primary energy into usable forms of energy leads to losses due to energy consumption by power generation facilities themselves and power transmission. As a result, consumers wind up with only 1,120 PJ of so-called delivered energy or "site energy". Industry and business consume 42 % of this energy, households 29.5 %, and the transportation sector 28.5 %.

In our hypothetical city, residents, authorities, and industry have all pledged to practice energy conservation. Heat is a good place to start, because 58 % of the delivered energy in Germany is used solely to generate heat for offices, schools and homes, as well as heating up household water and supplying process heat in industry. The latter includes steam and heat for producing aluminum, zinc and chlorine. According to the Arbeitsgemeinschaft Energie­bilanzen—a federation of seven German energy associations—heat accounts for 80 % of total energy consumption in private households.

Heat thus offers huge savings potential that can easily be exploited. According to Germany’s Federal Environment Agency, energy consumption could be cut by 56% in older buildings alone, simply by renovating, insulating outer walls and basement ceilings, and installing heat-insulated windows. Old buildings consume 17–25 l of oil or cubic meters of gas per square meter of space per year. For comparison, conventional new buildings require only 10 l/m³ per year and low-energy houses five to seven. Even more impressively, a so-called "passive house" needs just 1.5 l of oil or cubic meters of gas per square meter per year.

It is therefore not surprising that all the old buildings in our hypothetical city have been renovated and new buildings have been built in line with low-energy or passive house standards using government funding.

The situation is similar for industrial and commercial buildings, in which process heat and space heating account for 67 % of total energy consumption. Electricity is also needed for ventilation and air conditioning systems. In our efficient city, however, these systems no longer run at full capacity all day but are instead regulated in line with requirements. Here, heat and CO₂ sensors determine whether rooms are too cold or stuffy, while other sensors register if rooms are occupied and assess how much fresh air is needed. Such solutions are a specialty of Siemens Building Technologies (SBT), whose energy-saving experts search for "energy leaks" in everything from hospitals and shopping centers to government agencies and schools. As it turns out, energy consumption in many buildings can often be reduced by 20 %–40 % without any major investment in new technology. This is possible because the SBT specialists align climate control systems as closely as possible with actual requirements.

By employing specialized algorithms, they can calculate when ventilation and heating systems need to be turned up to ensure precise temperatures at specific times. Detectors are also used to determine when rooms are empty, in which case lights and ventilation systems are automatically switched off. Technicians can even access operational information online. If, for example, someone has turned up the heat too high or forgotten to switch from the manual to automatic control mode, technicians can remotely make the necessary adjustments.

Miserly Motors. Our efficient city has also plugged other energy leaks, such as losses from the electric motors used in drives, conveyor belts and pumps. Motors account for nearly 70 % of total industrial power consumption. A lot of energy can be saved here by using intelligent and more efficient motors. In the past, virtually no one knew how much electricity was being used by which machines in a factory. But Siemens Automation and Drives has developed analysis software that enables operators to obtain such data. Known as Simatic powercontrol, the software works its way through processes at a factory and finds out how much energy is consumed by each machine—and when. This process reveals hidden potential for optimization and identifies energy guzzlers.

Of course, waste heat is also harnessed in the efficient city. Industrial Solutions and Services offers a concept here that is perfect for all sectors where large amounts of waste heat are produced, such as the glass, metal, pharmaceutical and cement industries. The principle is always the same. Waste heat vaporizes a liquid, and the resulting gas is used to drive a turbine, which in turn generates electricity.

Naturally, all of these measures cost money. And given that local governments generally operate on tight budgets, energy savings performance contracting can offer an ideal solution. Here, Siemens plans and installs new technology that guarantees energy savings. Local government pays for the investment in installments financed from the energy savings achieved. Such a system doesn’t burden local budgets, and once the contract expires after around ten years, all savings flow directly to the client. In Berlin, for example, SBT renovated 11 municipal indoor pools by replacing boilers and installing more-efficient heat recovery and warm water processing systems. It also converted operation from oil to gas. The public swimming pools now save 1.63 mill. € per year—or one third of their previous energy costs. Performance contracting particularly pays off in old municipal buildings, where it can often halve energy consumption. The concept has also been successfully implemented in hospitals.

Putting the Brakes on Energy Use. Our energy-efficient city has also addressed the second-biggest energy consumer—transportation, which accounts for 28 % of delivered energy. Up until recently, 5.6 million passenger cars were on the road in our hypothetical city, emitting 15 mill. t of CO₂ per year. That was reason enough for the city’s residents to start using the extensive and modernized public transit network, especially since taxes and toll fees had made driving vehicles with high CO₂ emissions expensive.

The new buses and trains are comfortable, travel frequently at precisely timed intervals and consume 30 % less energy than their predecessors, thanks to lightweight materials and regenerative braking systems. Motorists use hybrid vehicles that store braking energy in their batteries, which is then transferred to an electric motor. This reduces fuel consumption by around 20 %. It will be possible to save even more energy when electric drive units and electric brakes are integrated directly into each vehicle’s wheels. In the meantime, Internet-based information and efficient traffic guidance systems are helping to prevent traffic jams and facilitate parking.

Our city wouldn’t be an efficiency champion if it hadn’t also cut power consumption. Although electricity only accounts for some 20 % of all delivered energy consumed in Germany, that’s only half the story. After all, it first has to be generated in gas, coal or nuclear power plants, whose losses total anywhere between 50 % and 65 %. In other words, 38 % of all the primary energy consumed in Germany is used to produce electricity. That was too much for the efficiency champions, who make better use of primary energy in facilities like combined cycle power plants, which today can already convert more than 58 % of the energy contained in gas into electricity. The energy-efficient city has not only increased this figure to more than 60 % but also exploits associated heat, pushing the fuel conversion rate to over 80 %. Here, process steam and heat are sent via pipes to nearby factories and apartment buildings.

In the town of Irsching, where a 530-MW combined-cycle plant is being built, Siemens is already demonstrating that efficiency ratings of more than 60 % could soon be the norm. The facility, which is being built for energy supplier E.ON, is scheduled to go on line in 2008. At the heart of the plant is a 13-m-long gas turbine built by Siemens in Berlin. Weighing 444 t, it’s as heavy as six diesel locomotives—but has 100 times the output. In fact, its 340 MW could supply the population of a city like Hamburg.

Future versions of the plant are expected to achieve an efficiency of 63 % within ten years. The implications of this become clear when you consider that replacing all coal-fired plants worldwide with the latest combined cycle plants would result in over four billion tons less CO₂ being released into the atmosphere each year.

Renewable energy sources also help reduce CO₂ emissions in our imaginary city. For example, solar cells can be found on top of nearly every public and private building. Windmills, geothermal plants and biomass power plants also provide their share of electricity, while a large portion of household waste is converted into fuel for power plants. Siemens and Energie Baden-Württemberg (EnBW) are developing yet another option—a fuel cell power plant in the MW class, which they plan to complete by 2012 (see  Fuel Cell Power Plants). When combined with a gas turbine, it will convert around 70 % of energy into electricity.

Saving at Home. Residents of the efficient city also contribute to energy conservation. Almost half of all electricity consumed in the household is used by refrigerators, freezers, stoves, washing machines and dishwashers. Purchasing new appliances is the best investment here, as the consumption of such devices has been cut by 30 %–75 % since 1990. The Wuppertal Institute for Climate, Environment and Energy estimates that replacing old household appliances throughout Germany would reduce annual electricity consumption by 7.9 TWh (billion kWh) or 28.4 PJ—the equivalent of the annual electricity requirement of nearly five million people.

Lighting systems in this hypothetical high-efficiency city would be completely re­vamped as well. Lighting accounts for more than 10 % of electricity consump­tion in Germany and nearly 19 percent worldwide. Given the current global energy mix, that corresponds to emissions of 1.6 billion tons of CO₂ per year—or the emissions produced by 500 million passenger cars (see  A Spectrum of Applications). The potential for savings here is huge and easy to exploit because energysaving lamps can reduce consumption by up to 80 % compared to conventional light bulbs (and last around 15 times longer). So too can LED lamps, which last around 50 times longer than incandescent light bulbs.

Some cities are already making the switch. Budapest, for example, has commissioned Siemens to replace the light bulbs in all of its 33,000 traffic lights with LEDs. The financing scheme for the deal is similar to the performance contracting model, because the monthly installments are lower than the savings generated from reduced consumption and the elimination of traffic light maintenance. In other words, this investment pays for itself.

Less developed countries can also take advantage of solutions such as one offered by Osram, which will replace light bulbs in private homes with energy-saving lamps free of charge. This is made possible by the United Nations' first-ever approval of such a project under the auspices of the Clean Development Mechanism. Here, the reduction in CO₂ emissions is converted into emission certificates that pay for the investment.

Energy consumption can also be reduced in production facilities, which up until now have often been equipped with several thousand fluorescent lamps. State-of-the-art mirror louvre luminaires, electronic ballasts and dimmers that automatically adjust to natural light can generate lighting-related electricity savings of up to 80 %.

Thanks to the combined potential for energy conservation in households, buildings, industry, transportation and power plant technology, an efficient city could reduce its consumption of primary energy and its CO₂ emissions by 50 %. This analysis of a hypothetical city clearly demonstrates that a variety of solutions already exist for achieving major reductions in energy consumption. In other words, they don’t have to be developed—they could be implemented right now.
                                                                                                               Tim Schröder