Summary: Grid operators may have a new ally in their efforts to integrate more renewable energy sources and regulate the frequency of the grid: buildings. Variable-speed drives used to run heating and cooling systems can be rapidly modulated in response to signals from grid operators, helping keep the frequency of electricity flowing across the grid within necessary tolerances.
Power grid operators must work around the clock to keep the frequency of electricity flowing across the grid within a narrow range in order to prevent damage to electrical equipment and keep lighting from flickering. These efforts are strained by the growing use of wind and solar power, whose rapid changes in output can cause unwanted fluctuations in the frequency of the grid. Grid operators must then quickly adjust the output of other conventional power plants to compensate, which causes wear and tear on power turbines and burns more fuel.
According to MIT researchers, grid operators may have a new ally in their efforts to regulate the grid: buildings. The systems that heat and cool large commercial and residential buildings are often powered by variable-speed electrical motors. According to detailed simulations at MIT, these variable-speed drives can be rapidly modulated in response to signals from grid operators. The heating or cooling output of variable-speed systems will vary in response, but temperatures inside the building can be kept within a comfortable range. That’s because buildings are effectively big thermal batteries, storing heat or cold within materials in the walls, floors and ceilings and in the air inside the building envelope. That thermal storage buffer gives buildings the ability to vary heating and cooling output to help regulate the grid without sacrificing the comfort of occupants.
Microgrids, local networks of distributed generators, energy storage devices, and smart electrical loads, must also keep frequency in a tight range. Yet with just a few small-scale generators or batteries, microgrids have fewer options to regulate frequency than the larger grid. Simulating an isolated microgrid, the MIT team demonstrated how buildings with variable-speed heating and cooling systems can help keep microgrids running in safe ranges while ensuring occupant comfort and avoiding long-term damage to building systems.
Publication: “Modeling and Analysis of a Variable Speed Heat Pump for Frequency Regulation Through Direct Load Control,” IEEE Transactions on Power Systems (in press, published online May 2014).
Authors: Young-Jin Kim is a doctoral student in the Department of Electrical Engineering and Computer Science, Les Norford is professor of Building Technology, and James Kirtley is professor of Electrical Engineering at the Massachusetts Institute of Technology.
Note: This is article is part of an ongoing series of concise summaries of interesting and important conclusions from new research and peer-reviewed journal articles. This series at Full Spectrum is written in partnership with Observatorio de las Ideas, a Spanish-language publication which finds and summarizes important, cutting-edge ideas for policy makers, business leaders, and others on key topics like energy, health care, economics, and more.
- Will buildings be a major contributor of frequency regulation or other ancillary services?
- How do buildings stack up against other possible providers of frequency regulation, including electricity storage, flexible power plants, and automated demand response?
- How critical is enhanced grid flexibility to integration of variable renewable energy sources like wind and solar power?
- What incentives, markets, and business models would be necessary to unlock the potential of buildings as providers of grid services?