One of today’s ‘great controversies’ in power electronics has been the use of ac-powering versus dc-powering for data centers, campus-sized micro grids, and other applications of varying sizes. The New Year will see the seeming controversy resolved and dc-powering will be increasingly seen as a viable and valuable solution. Three examples serve to illustrate this situation and the benefits that will be derived from the use of dc-powering technologies, the European Union’s DCC+G (DC Components + Grid) Project, the directive from the California Public Utilities Commission to incorporate extensive energy storage resources into the electricity grid, and the U.S.-based EMerge Alliance. Similar efforts are underway in various forms in Japan, Korea, China and other countries.
The DCC+G project is being driven forward by the European Commission's target of 2021 for 'nearly net-zero energy buildings' in new construction. According to the EC: The ac main utility grid does not completely match to today's electronic (dc) loads and dc distribution offers simpler control of multiple sources, easier integration of renewable power, and higher efficiency end to end for dc loads. The initial test beds are aiming for at least a 5% overall efficiency improvement compared with today's ac-based architectures.
With a total budget of 18M â‚¬, the DCC+G project is running on a 3-year timeline that started in April 2012. It includes 13 world-class partners from 5 countries (including 5 industry partners, 5 SME partners, and 3 research institutes). The major industry partners include Emerson Climate Technologies, Emerson Network Power, Infineon Technologies, Philips and Siemens.
Lower-power loads connected to a single 380Vdc bus while larger loads connect to the +/- 380Vdc bus. Grounding will be typical IEC TN-S system. Example of commercial buildings being targeted include; Supermarkets, large office buildings, and airports. The key objective of the project is to design and validate an energy-efficient building, with an integrated 380-Vdc energy distribution system including innovative and highly-efficient semiconductor power technologies.
Two primary goals of the project include; Infrastructure component design (sensors, switches, IGBTs, and so on) and Subsystem design for 380-Vdc grid in test bed installations. Many new technologies are expected to be developed to advance the application of 380-Vdc applied in commercial buildings. The DCC+G project expects to have two test beds operational starting August, 2014, with a final report available in 2015.
In October, 2013, the California Public Utilities Commission (CPUC) established an energy storage target of 1,325 megawatts for Pacific Gas and Electric Company, Southern California Edison, and San Diego Gas & Electric by 2020, with installations required no later than the end of 2024. The guiding principles of today's decision are 1) the optimization of the grid, including peak reduction, contribution to reliability needs, or deferment of transmission and distribution upgrade investments; 2) the integration of renewable energy; and, 3) the reduction of greenhouse gas emissions to 80 percent below 1990 levels by 2050, per California's goals. Energy storage systems can be deployed in three "grid domains" - transmission-interconnected, distribution-interconnected and behind-the-meter-interconnected.
This decision directs the utilities to file separate procurement applications containing a proposal for their first energy storage procurement period by March 1, 2014. The decision further establishes a target for Community Choice Aggregators and electric service providers to procure energy storage equal to 1 percent of their annual 2020 peak load by 2020 with installation no later than 2024, consistent with the requirements for the utilities. According to the decision, the state's investor-owned utilities must begin buying a combined 200 MW of energy storage technology by 2014 and reach 1.3 GW (1,325 MW) by the end of 2020. This is expected to increase California's installed capacity six-fold from its current 35 MW. "This decision represents an important first step in encouraging the storage market and supporting grid reliability," said Commissioner Carla J. Peterman, the lead Commissioner for this proceeding.
In anticipation of the growing market for utility-scale energy storage systems, EnerSys entered the market with its new OptiGrid Stored Energy Solutions, a new turnkey megawatt-hour scale energy management system for utilities and large industrial applications. According to the company, power grid stabilization is a prime concern among today's utilities, as they balance supply and demand and cope with issues such as voltage regulation, frequency regulation, peak management and renewable power integration. In addition, power disturbances are a major cost and concern today for both utilities and industry. It is estimated that the U.S. economy is losing between $119 billion and $188 billion annually from power outages and power quality issues.
Last November, the EMerge Alliance announced the launch of a new residential dc power standards initiative to advance the use of dc power in homes and small businesses. The Alliance is the only application standards development group working on advancing the use of dc power in residential and commercial buildings. The Alliance is forming a technical committee to identify needs and opportunities for residential dc power standards. EMerge Alliance members will collaborate with organizations like IEEE on the standards-development process.
Also in November, EMerge announced expansion of the EMerge Alliance Registered product program to include the first products supporting the EMerge Alliance Data/Telecom Center Standard. The EMerge Alliance Registered product program is the industry’s only program designed to simplify the use and adoption of dc power products that deliver numerous benefits enabling net-zero energy buildings. The EMerge Alliance Data/Telecom Center Standard creates an integrated, open platform for power, infrastructure, peripheral device and control applications to facilitate the hybrid use of ac and dc power within data centers and telecommunications central offices.
The residential dc power standard initiative is an expansion of the Alliance's long-term strategic plan of creating standards for the use of dc power throughout buildings. Since its inception in 2008, the Alliance has focused its work on developing dc power standards to increase the sustainability, flexibility and efficiency of commercial buildings. It also pioneered a data/telecom center standard designed to improve the efficiency and reliability of equipment, while decreasing the total operating costs of these centers.
According to EMerge Alliance Chairman Brian Patterson, the increasing percentage of home electronics running on dc power, combined with the rapid expansion of the residential solar market in the U.S., makes dc power distribution a clear opportunity for homes to achieve energy savings and grid independence.
"We have seen the sustainability, flexibility and reliability advantages that DC power provides to commercial building spaces, and it's time to extend these benefits to homes and small businesses," Patterson said. "DC power distribution would not only maximize the efficiency and ROI of rooftop solar panels by enabling them to directly power consumer electronics, appliances, LEDs and electric vehicles (EVs) without conversion losses, it could also give homeowners a choice to either store excess DC power or continue selling it back to power companies."
Like all EMerge Alliance standards, this new residential initiative will include the hybrid use of ac and dc power by defining interfaces with existing ac power systems at various upstream and downstream levels, with the goal of providing plug-and-play convenience for homes and small businesses, including faster EV charging and direct support of the expanding use of USB, wireless charging and other low-voltage dc power distribution means that simplify the convenient and efficient use of personal electronics and home automation equipment.