Contact: Allan Chen (510) 486-4210, A_chen@lbl.gov
Producing new commercial buildings that use 80 percent less energy than today’s average building is a new target in the fight against global climate change. If such a building’s remaining energy consumption is supplied by clean, carbon-neutral renewable energy, it would be responsible for little or no greenhouse gas emissions.
Buildings in the U.S. today consume 72 percent of electricity produced, and 55 percent of U.S. natural gas use. They account for about 40 percent of total U.S. energy consumption (costing $350 billion per year) and greenhouse gas emissions. Reducing the GHG emissions associated with buildings is essential to reducing overall U.S. emissions.
Before ultra-efficient buildings become commonplace, researchers will need to develop new technologies. Demonstration projects dating back to the 1990s suggest that it is possible to build these ultra-efficient buildings now, but at great expense. New research at Berkeley Lab is aimed at developing the advanced new technology to make it possible to build such buildings economically and in large numbers. Scientists at Berkeley Lab’s Environmental Energy Technologies Division, in partnership with United Technologies Corporation’s Research Center, and the University of California, Berkeley, Merced and Santa Barbara, have embarked on research aimed at developing computer models, building control algorithms and performance monitoring systems for the low energy buildings of the near future. The research is funded by the U.S. Department of Energy and the California Energy Commission’s Public Interest Energy Research Program.
The research teams are performing field testing and demonstration work of new technologies on the campus of the University of California, Merced. The UC Merced campus has five buildings which have received LEED ratings for sustainable design-four gold and one silver. The campus has been designed to be a living laboratory, with sensors and instrumentation to support the development and demonstration of energy-efficient technologies and practices.
Some of these campus buildings already achieve a high degree of energy efficiency. “We have a goal that buildings consume half the energy and demand of other University buildings in California,” says John Elliott, UC Merced’s Manager of Engineering, Energy, and Sustainability Facilities. “We have statistically significant benchmarks based on data from other campuses, and we have been phasing in this goal.” The campus’s first round of buildings were designed to use 80% of the energy benchmark, and the current round of buildings are being designed to be 65% of benchmark. The next phase of buildings will be designed to 50% of benchmark. However, according to Elliot, through careful design and energy management, many campus buildings are already achieving performance better than these goals. The campus is therefore the perfect place to begin testing new hardware and software technologies to drive building energy efficiency to even higher performance levels.
The strategy for achieving ultra-low energy use
“Today, there is usually no transfer of knowledge and design specifications from the design phase to operations,” says Philip Haves, Leader of EETD’s Commercial Building Systems Group. “Very few new buildings are commissioned and most building facilities management staff don’t have access to the design specifications of building systems they maintain.”
When buildings are designed so that their systems work together to maximize energy efficiency, they can use substantially less energy than they do on average today, even as they provide heating, ventilation, air conditioning and lighting, together with power at the electrical outlet. For this enhanced performance level to be achieved the building needs to be constructed according to specification-not always the case today.
Newly constructed buildings need to be commissioned-the process of having a team of engineers start up the various systems in the building, test them to make sure they are operating according to design specifications and make adjustments if they are not. Commissioning is originally a naval term applied to the process of making sure ships are seaworthy. Commissioning of both new and existing buildings could save billions of dollars in U.S. energy costs, according to Berkeley Lab research estimates.
Finally, buildings need to be operated by a facilities staff with training in the use of sensors and monitoring systems that provide them with accurate, real-time information about the energy performance and environmental conditions within the building.
This approach to improving efficiency in buildings selectively applies systems engineering methods that have transformed other industries, including the aircraft and automobile industries.
Need to know: building energy use in real-time
PC-based monitoring systems could open up a new world of real-time information to facilities staff about how energy is being used in buildings, but there is no common hardware and software platform-no standard building design and operating platform-nothing comparable to the operating system software common to many personal computers, for example.
A problem today is that “we don’t measure the energy use of buildings in real-time,” says Mary Ann Piette, the Deputy Head of EETD’s Building Technologies Department. “Most energy management systems in buildings are geared toward controlling energy use, but without much feedback about how buildings are actually using energy.”
Further, there is no performance standard for buildings-not for energy use, occupant comfort, average maintenance cost, or any other building metric one can think of. Most LEED standards are design oriented-the builder obtains a LEED rating by specifying various energy efficiency, water, materials and transportation-related measures, but once the building incorporates these during construction, there is usually no monitoring after the building is occupied to determine how well the building is really performing relative to the initial goals.
Performance benchmarks-data about how much energy an energy-efficient building uses compared to how much is used by an actual building of roughly the same size and type-would help facilities managers do a better job of operating buildings for energy-efficiency as well as for other qualities such as occupant comfort.
A benchmark is a data set of performance metrics for the operation of a building, its energy use and the conditions within the building. Comparison of the performance metrics in different buildings can help a facilities manager pinpoint where specific problems in a building lie-for example, perhaps the lighting is efficient, but air conditioning energy use during the summer months is higher than normal for a building of that type, leading to the deduction that a chiller plant is underperforming. Benchmarks for each energy-using system in the building provide managers with the target data they need to ensure that each of their systems is operating efficiently.
Another need is for a broad, deep data set about performance of many, preferably thousands, of buildings in real-time-in other words, a building informatics repository. This would not only help building managers do a better job, it would help building scientists develop better control strategies for managing building energy use.
Berkeley Lab researchers are conducting three preliminary R&D projects aimed at developing a building design and operating platform, and an informatics repository.
Model Predictive Control
Berkeley Lab EETD researchers Philip Haves and Michael Wetter, the University of California’s Francesco Borelli, John Elliot of UC Merced and other team members from the United Technologies Corporation Research Center, are testing “model predictive control” (MPC) of a central chilled water system, which provides cooled air to campus buildings.
In model predictive control, a computer model of the chilled water plant simulates the effect of different control options on the performance of the system and provides input to the real-time control system for the chilled water plant so that it provides the cooling needed to maintain comfortable conditions while minimizing the cost of energy.
The computer models of the chillers, the cooling towers, the storage tank and the pumps are based on the manufacturers’ performance data and then fine-tuned to the measured performance of the system. The team estimates that energy savings of 10 to 20 percent of total HVAC energy use is possible using MPC. Field testing at UC Merced this summer will be used to determine the actual savings and provide a demonstration of the technology.
Michael Sohn, Group Leader of EETD’s Airflow and Pollutant Transport Group and colleagues from UC Merced and United Technologies are studying the use of sensors and occupancy estimating methods to control a building’s lighting and HVAC systems.
The guiding idea of this work is that if the occupancy density of a building is well known, its lighting and HVAC (heating, ventilation, air conditioning) energy consumption may possibly be reduced by 10 to 20 percent in a typical office building during the cooling season. What is needed is a hardware and software tool that determines the occupancy in different parts of the building accurately in real time.
Motion sensors exist today, but they only tell you if a space is occupied, not how many people are there. Carbon dioxide sensors are also available, and they are better indicators of how many people are in a room, but they are relatively slow to react-people come and go quickly, but CO2 levels change slowly.
Sensors that can quickly estimate how occupancy is changing in a space may be able to provide data that allow a control system to reduce lighting and HVAC services to unoccupied spaces quickly. For example the control system could allow room temperatures to float beyond their occupancy-based set points, and rapidly increase services in time to meet anticipated needs.
The research team will build smart, low-resolution sensor networks, and develop data processing algorithms, occupancy dynamics models, and energy control methods. The team will test whether this technology can provide sufficient data on building occupancy to make intelligent HVAC and lighting control possible at buildings on the UC Merced campus. The research will also develop benchmarks of the energy savings possible in buildings at different levels of occupancy.
Visualizing the Energy Performance of Buildings
Piette and her colleagues are developing visual tools for communicating the energy performance of buildings in real time so that better information can help facilities staff better manage their buildings. Collaborating institutions include United Technologies, UC Merced and UC Santa Barbara.
The team is developing tools to compare the measured energy performance of buildings to baselines derived from computer simulation, benchmarking and previous performance measurements. Their plan includes developing new methods of estimating quantities that are not measured in the building, such as space heating and cooling loads (the demand for power to keep the building properly heated and cooled) to help building facilities staff diagnose problems.
The methods and tools will correct for uncertainties in measurements and simulations in a systematic way, something that is typically not done in the building industry today. The researchers are also developing software for visualizing building conditions and performance designed for decision-makers at different facilities management levels.
Piette’s team will test the prototype monitoring system in the Science and Engineering I building and on the central plant on the campus of UC Merced.
The aim of the technology is to reduce energy consumption and electricity demand by 20 percent or more in large commercial buildings by providing actionable energy performance information to facility managers and operators.
More about commercial buildings research at Berkeley Lab: http://buildings.lbl.gov/
The Demand Response Research Center: http://drrc.lbl.gov/
Model Predictive Control at UC Berkeley http://sites.google.com/site/mpclaboratory/
LEED-rated buildings at UC Merced http://administration.ucmerced.edu/environmental-sustainability/green-buildings-and-leed
UC Merced Efficiency Testbed: https://eng.ucmerced.edu/soe/facandres/intra-campus/eng-res-meri
United Technologies Research Center http://www.utrc.utc.com/pages/our_company.html