Innovations in Comfort, Efficiency, and Safety Solutions.
Internal Sharing of Energy Information to Support Smart Grids
Every building, and every group of buildings, must become a microgrid. A microgrid is responsible for managing its energy use, generation, storage, and market operations.
Smart grids and the dynamic energy market they create present challenges to buildings far beyond those of traditional energy efficiency. (For this article, buildings incorporates industrial sites, commercial buildings, and even homes). The traditional focus on energy efficiency, while important, ignores issues presented when grid-supplied energy is available at a high price, or not at all. Distributed intermittent energy generation will present periods of local super-abundance, when normal efficient operations are unable to consume the energy available in the local market.
When we look beyond the building, to the buildings interactions with the energy sources and markets outside the building, we move away from energy efficiency to energy resilience. Efficiency scenarios anticipate a ready supply of energy at a predictable cost. Site-based generation introduces intermittent energy supplies within the building. Smart grids anticipate swings between scarcity and abundance, with prices to match. It becomes necessary for each building to manage its energy availability as well as energy use.
Every building, and every group of buildings, must become a microgrid. A microgrid is responsible for managing its energy use, generation, storage, and market operations. The purpose of the market operations are to acquire energy from the grid, when it makes sense, and to dispose of surplus, when it makes a profit. Tomorrow’s microgrid will face increased risks from the grid: increased availability risk, and increased price risk. The microgrid will manage these risks by managing its own use, generation and storage.
The approach of microgrids is recursive. A data center, or a suite could be a microgrid inside the building-based microgrid. On office park or a campus could be a microgrid of generating assets, storage assets, and many building-based microgrid. At each level, a microgrid establishes its own context for managing its energy use, generation, storage, and market operations; to the larger grid, those details are hidden.
Microgrids manage more than electricity use. Local energy uses and local energy sources present opportunities for the inclusion of a more diverse set of energy cycles than supported by the commodity grid. A direct connection between energy source and energy use eliminates conversion loss. Thermal capture, storage, use, and recycling are energy cycles managed as part of the microgrid. Energy can be stored in a form close to its final use, increasing the range of storage technologies. Direct Current (DC) distribution can efficiently match site-based electricity and its final use.
The site based microgrid is the organizing concept for systems design and systems management in net zero buildings. Greater knowledge of local needs and local assets enables better management than the grid operator can provide. Smaller spans of integration and of control allow more diversity. Local decision-making and tolerance of diversity enables markets that accept faster technological change. Internal management of systems and reliability supports greater privacy and autonomy for the building occupants.
Grid Integration challenges to the EMS
As the grid incorporates intermittent energy sources, large intra-day swings in supply will be reflected in large swings in price for electricity. As distributed energy puts strains on the distribution infrastructure, congestion charges may raise prices even when electricity is available. Building owners must plan to manage the risk of volatile availability and price previously managed by electricity providers.
Building-based generation cannot fully ameliorate grid-based shortages. Limits on the use of fossil fuels to generate electricity for the grid, whether economic or regulatory, will impose matching limits on technologies for site-based generation. Re-sale if site-generated electricity back to the grid will become less valuable as true markets develop and true costs are covered. Strategies that consume energy when available, to provide service when it is not, will be critical.
Consider intermittent site-based generation of solar power. Surplus power from site based generation will enter the market at the same time as surplus power from your neighbors; the sun shines on all alike. Whole neighborhoods selling power to the next creates distribution bottlenecks, which will be reflected in congestion charges. Once every office in the office park has solar power, sales to the grid in the afternoon will be like trying to give away home-garden zucchini in August.
For the same reasons, local scarcities also will re-enforce themselves. The wind will die down, and the rain clouds will cover the sky for a region at a time. Failure of one building to generate site-based power will align with the failures of its neighbors. Distributed renewable generation, if designed for simple net metering, will only make grid-based markets more volatile. Buildings will always be subject to the downside of the market risk.
Market conditions will reward the building able to balance its energy use within it site. Load shaping and load management will be used to mitigate risk. Controllable temporal shifts in energy purchases will be as important as energy efficiency. Anything that can buffer between energy acquisition and energy use we become more valuable. Storage technologies of all kinds will be valuable.
Pre-consumption will grow in import as a buffering technology. Thermal storage that chills when electricity is cheap for use when electricity is expensive will become the norm. Volatile prices will reward pre-consumption of all kinds. Pre-pumping that stores energy in high water tanks is as useful as exotic battery technologies.
As storage and pre-consumption capabilities grow, they will improve as alternatives to sales back to the grid. It may be better to use wind-generated energy for even inefficient storage rather than to sell electricity at the bottom of the market and buy later at the peak.
This price volatility is likely to be associated with reduced power quality from the grid. The power quality of the local distribution loop can be no better than the quality of the poorest performing, least maintained generation system of your neighbors. Poor voltage regulation, unbalanced power, out-of-phase noise, and other ailments will dirty the local loop. Minimal operating margins will reduce the capability of the grid to compensate. Power conditioning will raise the costs of using power from the grid.
The energy-resilient building will be responsible for a growing amount of it power supply. Site based generation will find greater value through intra-site load shifting. Responsibility for power quality will devolve onto the site.
Above all, the aim of intra-building protocols is the stability and resiliency of building service despite a volatile grid, volatile in availability, volatile in price. By hitting it’s mark, the building will have well-managed loads, with predictable load shapes. The building will be able to respond when asked by the grid, and its predictions of response will be accurate. A well-managed load, with a predictable shape, is the most valuable customer for smart grids.
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