Dynamics of Energy Efficiency
Dynamical issues are ubiquitous within the context of demand-side energy efficiency. Modern commercial buildings operate in an environment that is dynamically uncertain both with respect to load (number of occupants in the building, their energy demand) and environment (weather conditions, state of the power grid). Micropower generators and energy harvesters operate under conditions of uncertain energy supply. Mechanical energy storage devices need to be able to operate in either generation or storage mode, depending on conditions. There are common threads that run through all these applications. Understanding the dynamics, stability and control of networks is essential: optimization of functionality that is enabled by access to uncertainty-reducing information and the consequent ability to act upon the information to alter the behavior of systems are the fundamental issues in the area of Dynamics of Energy Efficiency.
UC Santa Barbara researchers in energy efficiency of buildings are a part of the national research effort in integrated building systems, that includes commercial (United Technologies Corp.) and government laboratory partners (Lawrence Berkeley Laboratory)
(Graphic courtesy of United Technologies)
Buildings provide a specific example where dynamical issues play a substantial role. Commercial buildings alone account for 20% of the total U.S. energy bill. Commercial and residential buildings together produce close to 50% of the USA carbon emissions. While substantial savings (10% to 30%) can be realized using existing hardware and modeling tools and algorithms (such as “Energy Plus”) for the retrofit of old, and the design of new buildings, much more can be achieved with modern approaches based on Dynamics of Energy Efficiency principles. Igor Mezic, Jeff Moehlis, and Joao Hespanha are leading research efforts in Integrated Building Systems where active control of indoor airflows could greatly improve the ventilation and efficiency of heating and cooling in buildings. A smart building containing an array of sensors and an integrated, optimized control system can adjust lighting and HVAC control based on actual usage rather than planned occupancy. Frederic Gibou, Eckart Meiburg and Moehlis are providing fluid dynamics and modeling and theories of mixing that underpin the optimal control problem. Walter Yuen is involved in international collaborations on buildings with colleagues in Hong Kong, and the UCSB effort is being pursued in partnership with leading government (Lawrence Berkeley Laboratory) and commercial (United Technologies Corporation) laboratories.
A host of environments produce considerable vibrational energy, such as automobiles, trains, aircraft, watercraft, machinery and buildings. Energy harvesters promise considerable energy efficiency and energy production by the exploitation of novel couplings between flow, electrical, thermal, and acoustical fields and hold great promise for remote off-grid generation. Moehlis is researching energy harvesting that exploits ideas associated with nonlinear oscillators driven by both periodic and stochastic inputs, Sumita Pennathur is using nanofabrication to develop microgenerators that use mechanical energy to produce streaming currents in micro- and nano-devices, and Bassam Bamieh is researching the use of thermoacoustic generators for similar purposes.
An important special case of building design is the problem of data center buildings, where there are few people but extremely large heat loads from high power density arrays of computer servers. The cost of energy use in data centers is estimated at $3.3 billion/year and is projected to rise rapidly in proportion to internet and server demand. Data centers, even more than typical office and commercial buildings, require efficient ways of redistributing cooling energy. They present special and unique challenges in the modeling of the coupling between the computer uses and the cooling systems. Mezic and Rich Wolski are nucleating a combined effort of faculty in UCSB’s Mechanical Engineering and Computer Science departments, leading to new approaches and solutions for this special class of buildings.
