SIEMENS

The roofs of many one-family houses are covered with shiny blue-black photovoltaic modules, hills are dotted with wind turbines, and offshore wind farms generate power in places like the North and Baltic Seas. However, electricity from the sun and wind is unreliable, because the energy produced fluctuates with the weather. Wind facilities now account for roughly seven percent of all the electricity generated in Germany, with almost two percent obtained through solar power. Over the last few years, wind parks in the North Sea have repeatedly been shut down due to strong winds that threatened to overload the local grid. In other cases, surplus electricity has been sent to neighboring countries, despite the fact that it was not really needed. This can sometimes reduce prices to such an extent that suppliers begin losing money, especially since they still have to pay transmission fees. Conversely, whenever winds are weak, so-called peaking plants must be switched on, which makes electricity more expensive.

The increasing use of energy from renewable sources will put even more pressure on power grids in the future. According to the German Energy Agency, some 3,600 kilometers of new power lines will have to be built by 2020 in Germany alone to transport electricity to consumers. But even that won’t be enough, as grids will have to become more intelligent so as to create greater transparency and ensure more flexible pricing models and better electricity distribution (see Pictures of the Future, Fall 2009, Switching on the Vision).

Also being discussed are electricity storage units that store surplus electricity when winds blow and the sun shines, and then return it to the grid when winds are calm and the sky is gray. In addition, electric vehicles might be used in the future as a giant energy pool consisting of innumerable batteries. Indeed, the batteries in two million electric vehicles would have an energy content of roughly 40 gigawatt hours of electricity — the combined capacity of all German pumped storage units.

Consumption Follows Production. And now, a new potential solution to the energy puzzle is emerging — one that could be implemented by simply introducing a sophisticated software package. Known as “load shifting,” the idea is to manage electricity consumers, or loads, in buildings in such a way that they are mainly allowed to occur only when windmills and photovoltaic modules are generating surplus power — i.e. when electricity is cheap. Conversely, as much electrical equipment as possible would be powered down at night or when winds are weak. This amounts to a paradigm shift, since these days the operation of gas and coal-fired power plants is geared toward energy consumption behavior in households, factories, and offices. But in the future, the situation would be exactly reversed. Buildings would alter their power demand in line with current energy supplies. Consumption would follow production.

Working with specialists from Siemens Building Technologies, researchers at Munich’s Technical University (TUM) have found that a range of equipment in all kinds of buildings can be switched on and off in a relatively simple manner. The team spent several months collecting data from building management centers on everything from ventilation system and water pump activity to temperatures in offices and conference rooms. They examined questions such as: How long does it take for an office made of lightweight materials to heat up after you turn off the building’s air conditioning system? “The key question for us was how long you can turn off certain equipment without affecting comfort in a room or office,” says Timm Rössel, a research assistant in the Department of Building Climatology and Building Services at TUM. German building standards stipulate that office temperatures should not fall below 21 degrees Celsius if comfort is to be maintained. Rössel and his colleague Johannes Jungwirth from the Department of Energy Systems and Application Technologies analyzed four different building types for their study: office and administrative buildings, hospitals, indoor swimming pools, and schools.

They found that load shift potential was particularly high in office buildings. For example, ventilation systems in offices with normal occupancy can be completely shut down for as long as half an hour without causing rooms to become stuffy — and this can be done several times a day. The same goes for ventilation systems in underground garages. The researchers also examined how often and, more importantly, how fast elevators travel in office buildings. They determined that elevator speed could be cut back several hours every day outside the morning and evening rushes, thereby reducing electricity consumption by around ten percent. They also found that elevator users were not annoyed by the slower speed.

There is also plenty of room for improvement in buildings equipped with a service water system for toilet flushing. The pumps that fill the system’s tanks could be started with a delay of as much as 12 hours without any danger of the tanks running empty. And in hospitals, energy-saving efforts can focus on sterilization equipment for surgical utensils. In buildings equipped with indoor swimming pools, the greatest load shift potential lies in the compressors used in dehumidification systems, which can actually be shut down for several hours. The same is true of ozone and UV units used for water purification.

“The results of the study are important for us because they prove that large buildings have an overall load shift potential that pays off,” says Joachim Kiauk, a project manager a Siemens Building Technologies (BT) in Zug, Switzerland, who was responsible for the study. “Put simply, Siemens is now developing software tools with TUM that can be used to manage building control systems in line with tomorrow’s increasingly renewable-energy-centered electricity supply.”

Several hundred parameters and measurement values are fed into modern building management systems today, including office temperatures and fan output figures. All of this data will have to be linked together by load shifting software. TUM researchers are now using building simulations to refine the corresponding calculation specifications. “Ideally, we will be able to integrate these algorithms into existing control technologies like our Desigo system,” says Siemens Building Technologies’ Kiauk. Just how the required knowledge will be incorporated into Siemens products has yet to be determined. “The first step is basic research,” says Christoph Hielscher, head of Business Development for Smart Grid Applications at Siemens Energy. “Our goal is to make buildings intelligent and enable them to note how quickly they cool down, how much heat they require, and when they can shut down certain devices in order to conserve electricity. Each building has its own specific characteristics.”

Load Shedding Solutions. In the U.S., electricity load management has been commonplace for years. Here, the focus is not so much on fluctuating electricity production as on so-called load shedding. The U.S. faces a situation in which power plants and infrastructures that in some cases are outdated are being pushed to the limits of their capacity. This is a problem particularly on hot days when millions of Americans turn on air conditioners. In order to prevent supply bottlenecks, power companies shut down specific consumers — i.e. they shed loads. For example, private customers who agree to turn off their air conditioners on several hot days throughout the year are rewarded with lower electricity rates. The same is done for industrial companies and refrigerated warehouses. And as more precise weather forecasts have made short-term alerts possible, power companies have been able to inform such consumers of the outages by e-mail or phone the day before. Some 80 percent of all load-shedding customers are directly informed in this manner. This may sound complicated, but a nationwide call center service is a lot cheaper than building new power plants or grid components.

As part of its strategy to automate load management operations, Siemens has acquired SureGrid, a company that develops load management software for central computers and communication systems. SureGrid’s central computer in Austin, Texas, can, for example, accept an order from a power company for a required amount of electricity and then automatically distribute this total among all the participating buildings in a region. This solves the problem of insufficient reliability. That’s because when a power company requests load shedding via e-mail, there’s no guarantee that the customer will remember to turn off his or her air conditioner the next day. The energy supplier therefore needs to play it safe by planning in more load shedding than is actually needed. Automation, on the other hand, will make load management calculations more reliable and secure in the future.

Automation also offers another advantage. At the moment, energy suppliers must use weather forecasts to estimate roughly one day in advance when and for how long they need to shed electricity loads. In this case as well, they plan in a buffer and ask customers to shut down their appliances for several hours — in most cases longer than is actually necessary. Automation would allow power companies to react right before a bottleneck occurs, which would reduce the duration of a load shedding event.

The U.S. energy market differs greatly from the European market, of course. Everything in the U.S. revolves around supply shortages, whereas Europe focuses on fluctuating electrical output from wind and solar facilities. Nevertheless, the U.S. is also taking an initial important step toward greater building intelligence and smart power consumption through its automated load management systems. “The next step would be to implement the type of building management technology the TUM project seeks to develop — technology that’s also very flexible and able to react to changing electricity prices,” says Hielscher. The benefits are obvious. If people turn off their air conditioners today, they start sweating — but an intelligent load management system would instead simply reduce the speed of the elevators in their building.