Considered by itself, the integration of distributed renewable generation sources into the electricity grid poses a number of challenges for the electric industry because of variability and lack of central control. Existing radial and network distribution systems are generally not designed for significant reverse or two-way power flow. This is an engineering and design reality that is at odds with the rapid deployment of distributed photovoltaics (PV)—averaging greater than 30% of grid connected new capacity additions per year. Given these higher penetration PV levels, utilities are becoming progressively more concerned about lineman and public safety, circuit protection, voltage control, and network reliability.
With large amounts of distributed solar on a partly cloudy day and with winds aloft, PV output can look fairly dismal. As shown in the chart below, transient cloud cover can significantly change PV power generation in a very short period of time.
PV production comes and goes at a rate that is much faster than typical end user load changes, underscoring the electric utility’s challenge of managing a variety of PV generator sizes, connection points, electronic interfaces, and distribution grid penetration levels. However, the core of utility reliability concerns relate to the aggregate effect of variability and controllability on existing distribution lines (that are not designed specifically for distributed energy resources [DER] such as PV).
Therefore, a collective of “green buildings” embedded with smart technology offers a novel opportunity for helping utilities balance rising levels of variability. The concept of the smart grid, which is intended to be intuitive about all energy delivery and resources—including load, demand response, distributed generation, and energy storage—is capable of supervising and administering a building’s entire demand and load activity. [For more on the smart grid, see “Evolving With The Smarter Grid”, also published in TFM November 2011.]
Much as appliances have different operating levels, so too do many building systems outfitted with thermal and electrical storage equipment. Meanwhile, plug-in electric vehicles (PHEVs) that can charge or discharge as necessary are anticipated to proliferate in the coming future. The potential upshot could very well be smart balancing via ambient and controllable building loads.The global marketplace will reward efficiency in the future. The U.S. is being outpaced by many emerging economies in adopting renewable energy technologies. According to the Solar Energy Industries Association, China accounts for nearly 80% of annual solar thermal installations worldwide, while the U.S. accounts for about .5%.
As mentioned, the EPA is the first major federal agency to purchase green power equal to 100% of its estimated annual electricity use nationwide. To qualify for a Green Power Partnership, potential partner groups must meet or exceed a minimum percentage of green power that corresponds to the organization’s purchased electricity use for a chosen purchase scope.
Green power purchases must also meet eligible resource, vintage, and “new” renewables requirements. Partners have six months from submitting a Partnership Agreement to make a purchase and meet the basic requirements.
Fms need to be diligent about energy efficiency improvements and evaluate the options of including some renewable energy in their organizations’ energy resource mix. If fms have climate emissions reduction commitments or goals, they need to start including the cost of offsets necessary to reach these goals in their evaluation of both energy efficiency and renewable energy choices. Proactive fms will not wait until global events make the transition to renewable energy an imperative.
Fms can get their facilities’ toes in the water by beginning to fulfill some of their energy needs with renewable energy. The EPA’s Green Power Partnership levels are great targets to consider.
Enbar is senior project manager for distributed renewables, power delivery, and utilization and Key is technical executive for the Electric Power Research Institute (EPRI). For more on EPRI, visit the web at www.epri.com.