Renewable Energy Supply

Abstract

Renewable energy can be defined initially as any energy source that is derived directly or indirectly from solar energy. In the broadest sense, however, almost all of the energy we use today, including fossil fuels, can be considered a form of solar energy. The most familiar forms of energy, such as wood, oil, gas, and coal, are embodied forms of solar energy gathered, stored, and transformed by natural processes. Climate change due to emissions of GHGs, particularly CO 2 , becomes an issue when stored solar energy is converted to useable forms of energy {heat, electricity, fuels, chemicals} at a rate far exceeding the rate of formation. For coal, oil, and natural gas, the ratio of time between formation and use is on the order of 1 million to one: that is, the world uses in one year what took natural processes one million years to create. Only biomass among these stored forms has a time ratio that is within a human time frame of years or decades. Renewable energy can now be defined as forms of solar energy that are available and replenished in time scales no longer than human lifetimes. Given this definition of renewable energy, it becomes clearer why renewable energy is an important option for mitigating climate change. Because renewable energy creates little if any net greenhouse gas emissions, its use will not disrupt the radiative energy balance of the earth's atmosphere and will permit sustainable, long-term mitigation of climate change. The renewable energy option will allow climate change mitigation, energy use, and economic development to proceed in synergy rather than in opposition. The remainder of this chapter will discuss what information, data, and analytic tools are needed to identify, screen, and characterize renewable energy options. The information and data needed include: economic and social development goals and needs • energy end uses and tasks to be performed characteristics of energy needs-scale {total requirements, grid/off-grid, centralized/distributed, etc.}-timing of energy needs {duration, seasonality, diurnal, etc.} • available energy resources technology characterization Once energy needs are defined within the larger context of economic and social development needs and plans, renewable energy resources and technologies can be identified and evaluated for incorporation into this larger context. The analytical tools needed include systematic methods to inventory renewable energy resources and to evaluate the most appropriate applications of these resources. This chapter presents an overview of renewable energy options and discusses resource assessment and characterization of renewable energy technologies. Methods for analyzing renewable energy options within an integrated framework are discussed in Chapter 3. Policy options for encouraging adoption of renewable energy technologies are briefly described at the end of this chapter. 9.2 MITIGATION TECHNOLOGY OPTIONS Renewable energy supplies encompass a broad range of resources, and numerous technologies can be used to tap those resources. Table 9-1 lists the major technologies and the following discussion briefly describes each technology and its applications. Although many of these technologies are still under development, most have entered commercial markets around the world at some level. Some, such as hydropower and biomass technologies, have achieved sizeable market penetration, while others (e.g., J. Sathaye et al., Greenhouse Gas Mitigation Assessment: A Guidebook