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Achieving energy independence

Achieving energy independence

Magazine Section: Change The World
College or School: CoE
Article Type: Issue Feature
Feature Intro: Buildings are the primary energy consumer in the U.S. Without a major transformation in the way we design and operate buildings, the U.S. cannot expect to meet its goals for greenhouse gas emissions.
Buildings are the primary energy consumer in the U.S. Without a major transformation in the way we design and operate buildings, to address complex engineering issues associated with their energy use and environmental impacts, the U.S. cannot expect to meet its goals for greenhouse gas emissions. These are the challenges driving research and educational pathways into the field of smart, net-zero energy buildings and building clusters.

Panagiota Karava, assistant professor of civil engineering, is among the Purdue researchers exploring ways to significantly reduce energy consumption by incorporating innovative strategies into the design and operation of new buildings, optimally linked with smart grids. Karava recently received the 2013 New Investigator Award from the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) for her work on model predictive control of high-performance buildings. The award supports Karava's three-year research project that could enable net-zero energy performance and market viability within the next decade.

The work includes key building-integrated solar energy systems and smart operation strategies that were not possible five or 10 years ago, Karava says. "The enabling technology simply did not exist, the computational power was limited and the weather forecasts were not as accurate."

Interdisciplinary approach is critical to success

Karava's research relates to building-integrated renewable energy systems, building thermal and airflow modeling and simulation, smart buildings, and predictive controls. "It is challenging, because it is very interdisciplinary and includes complex systems — hard to model, simulate and control," she explains.

Designers are committed to sustainability principles by finding ways to create buildings that can produce or sustain their own energy. However, buildings should also provide high-quality indoor environments to their occupants and these two are often conflicting requirements.

Improvements in weather forecasting accuracy, coupled with optimization algorithms that can run fast in real time due to more powerful computational resources, will show options to provide the least amount of energy consumption. This will allow the researchers to develop system integrations concepts and operation strategies that will reduce the demand-side loads while optimizing renewable energy generation, utilization and storage.

Her new experimental facility in the Robert L. and Terry L. Bowen Laboratory is an excellent platform for testing and prototyping new building technologies along with methods and algorithms for smart control.

Through a new "living laboratory" at the expanded Herrick Laboratories and the new Center for High Performance Buildings, Karava and the other researchers will be able to implement and test new building systems and concepts in actual working environments. Similarly, a "perception-based engineering" lab in the new building will be able to simulate a wide span of building environments. "This will be a unique opportunity to conduct collaborative research and to make a broader impact," Karava says.

"It's about designing a system than can anticipate weather conditions and adjust its operation to minimize energy loads. If it's going to be warm and sunny, you might decide to pre-cool the building during the night to lessen energy consumption and peak demand."

Most net-zero energy buildings are still connected to the electric grid. This allows for the electricity produced from traditional energy sources like natural gas or electricity to be used when renewable energy generation cannot meet the building's energy load.

Conversely, if on-site energy generation exceeds what the building needs, the surplus energy could be exported back to the utility grid, where allowed by law. But that isn't always as easy as it sounds. Her innovative research considers energy balances with a smart grid at different time and space scales (incorporated at the design stage) along with modeling representations of different complexity as a potential solution to this complex engineering problem.

For example, forecasts of heating/cooling loads and solar radiation can be used in an optimization algorithm to select a near-optimal set-point trajectory for a building and an energy storage tank heated with a hybrid heat pump that is assisted by a building-integrated photovoltaic thermal system.

Numerical prototypes of smart operating strategies for small generic groups of buildings can be developed to identify opportunities for net-zero energy performance beyond the boundaries of individual buildings.

"Smart buildings should be developed in parallel with smart grids," Karava says.

Saving energy, saving the planet

Karava says that the research isn't just about cost savings.

"Energy will become more scarce in the long term as fossil fuel sources are depleted," she says. "Also, reducing pollution and caring for future generations is critical."

From prototype building technologies, smart operation strategies and tools for new performance metrics, Karava and her team hope to develop the next generation of sustainable buildings and communities while reducing the need for additional fossil fuel power plants and providing superior indoor environmental quality to their occupants.