Renewable Energy Supply and Transmission
By Joe Abraham | The University of Arizona | June 01, 2009
Increasing the production and use of electricity from renewable and low-carbon energy sources is an important component of many state and local greenhouse gas reduction plans. Varying amounts of electricity can be generated from a variety of sources of renewable energy. From wind farms to rooftop solar panels, engineers and scientists continue to identify, design, and develop new and improved sources of energy that can provide power to the electrical grid and reduce greenhouse gas emissions.
Realizing the full benefit of wind farms and the many other large renewable energy projects being planned will require significant investment in our electrical grid.
Credit: ©Sven Hoppe, istockphoto.com
The U.S. electrical grid is a centralized, energy-producer-controlled network consisting of more than 9,200 electric generating units connected to more than 300,000 miles of transmission lines.1 The grid, however, is not well equipped to handle the many renewable energy sources that are envisioned and under development. Collectively, these energy sources are greater in number and more geographically dispersed, and in many cases they produce electricity intermittently. Thus, current efforts to transmit more low-carbon energy to and through the electrical grid generally focus on one or more of the following:
- Planning and developing large-scale renewable energy projects
- Increasing small-scale renewable energy generation
- Developing a smart electrical grid that utilizes a variety of renewable energy sources
Solutions for developing and transmitting more renewable energy are discussed below and are based, in part, on a review and analysis of state plans created between 2005 and 2007 in Arizona, New Mexico, Colorado, and Utah to help achieve statewide greenhouse gas emission reductions. Gubernatorial executive orders instigated the planning processes in Arizona, New Mexico, and Utah, while a coalition of stakeholders (including the state of Colorado) led by a regional non-profit organization initiated the Colorado plan. Recommended options for reducing emissions from these plans guided the research on recent and ongoing activities discussed below.
A renewable portfolio standard (RPS) is one of the most common policies used by U.S. states to increase the availability and use of renewable energy.2 State-by-state implementation varies, but in general a RPS requires electrical utilities to gradually increase the percentage of electricity they deliver coming from renewable energy sources like wind, solar, and geothermal hot springs. RPS can also provide important economic benefits for states if those new renewable energy sources are located in-state. Arizona, New Mexico, Colorado, Nevada, and California have a RPS in place. As of May 2009, Utah utilities are required to pursue renewable energy to the extent that it is cost-effective.
Figure 1. Western Governors’ Association and U.S. Department of Energy map of areas with large scale renewable energy development potential.
| Enlarge This Figure |
Credit: Joe Abraham, CLIMAS, The University of Arizona
Through a joint effort, the Western Governors’ Association, the U.S. Department of Energy, and a variety of stakeholders are working to determine where all this renewable energy will come from. They have recently identified areas in western North America that have significant renewable energy development potential (Figure 1). Not all these areas, however, are the most practical in terms of transmitting energy to the electrical grid. In 2010, the group aims to complete conceptual plans to deliver energy from many of these locations to cities and other areas of high energy demand.
In addition to improving renewable portfolio standards and regional energy project planning, states can help reduce barriers for projects designed to bring renewable energy to the grid. In Colorado, for example, renewable energy developers, transmission planners, financiers, and regulatory policy experts are working together to expand the state’s high voltage transmission system. The plan will help ensure wind and solar power resources in the state can be transmitted to energy markets. Similar efforts in other western states are underway.
Visit the Interwest Energy Alliance website for more information on the status of new renewable energy projects. The Alliance maintains an interactive map of renewable energy projects in the intermountain west with a capacity of producing at least 100 kilowatts of energy.
Increasing small scale renewable energy generation Increasing small-scale renewable energy generation
Smaller sources of renewable energy, like rooftop solar panels and small wind turbines, are typically installed in homes and businesses by owners seeking more energy independence or less reliance on non-renewable energy sources. These smaller renewable energy sources can provide much of the power needed for a home or business and at times produce energy in excess of demand.
Net metering is an increasingly popular practice that allows utility customers to provide this excess energy to the grid. Customers are credited for the energy that is provided back to the grid, which helps reduce the time it takes customers to recoup their investment in the systems. Most utilities and energy cooperatives in the U.S. offer net metering, but program specifics vary by state and utility. Collectively, the potential for the practice to increase the use of renewable energy and reduce greenhouse gas emissions is large, but most net metering programs currently limit the total amount of energy customers can individually or collectively send back to the utility.
Strong financial incentives and simple set-up rules are likely to play an important role in determining the pace at which additional renewable energy enters the grid by way of net metering. Federal, state, and local governments and utilities provide a variety of incentives for renewable energy development, such as tax credits, direct subsidies for purchasing systems, and short-term interest loans that help individuals and organizations purchase and set up a variety of small scale renewable energy sources. In addition to financial incentives, renewable energy experts and advocacy groups continue to push for simpler “interconnection” rules that utilities require customers to follow in order to participate in net metering programs.
Homes with solar panels can provide excess energy to the grid with net metering.
Credit: ©Richard Zuper, istockphoto.com
Energy demand in the U.S. is expected to grow between 16 and 36 percent between 2007 and 2030.3 Some of this demand can be met with the significant amount of new large-scale renewable energy sources already under consideration and development. This will require an expansion of the transmission lines to those sources (Figure 1). In addition to building more transmission lines, engineers and scientists are working to transform the current grid into a “smart grid.” This work will help improve the ability of today’s grid to transmit and monitor renewable energy sources efficiently. A smart grid also would help improve the efficiency of utility use of renewable energy from smaller sources via net metering.
Development of a smart grid will be expensive and require the participation of numerous groups including states, federal agencies, utilities, regulatory commissions, power generation and transmission councils, national laboratories, and many others. The city of Boulder, Colorado is partnering with the regional utility Xcel Energy and a consortium of technology firms to develop the Smart Grid City, an experiment to study and demonstrate smart grid technology at the scale of an individual community. The project represents the first fully integrated smart grid community with the largest and densest concentration of smart grid technologies to date.
Western Governors’ Association and U.S. Department of Energy “Western Renewable Energy Zones” project
| http://www.westgov.org/wga/initiatives/wrez/index.htm |
Colorado Governor’s Energy Office
| http://www.colorado.gov/energy/ |
Connecting Colorado’s Renewable Resources to Markets
| http://www.colorado.gov/energy/images/uploads/pdfs/23158d65cf0c2de7be220e35d1f7b72a.pdf |
Arizona Renewable Energy Assessment (2007)
| http://www.bv.com/Downloads/Resources/Brochures/rsrc_ENR_AZ_RenewableEnergyAssessment.pdf |
Utah Renewable Energy Zone Task Force renewable energy zone reports
| http://www.geology.utah.gov/sep/renewable_energy/urez/index.htm |
The Smart Grid: An Introduction
| http://www.oe.energy.gov/1165.htm |
| http://smartgridcity.xcelenergy.com/index.asp |
- U.S. Department of Energy. 2008. The smart grid: put it to work. Prepared by Litos Strategic Communication under contract No. DE-AC26-04NT41817, Subtask 560.01.04.
- Rabe, B.G.. 2006. Race to the top: the expanding role of U.S. state renewable portfolio standards. Prepared for the Pew Center on Global Climate Change.
- U.S. Energy Information Administration. 2009. Annual Energy Outlook 2009. Report # DOE/EIA-0383(2009).